Mars exploration in the last half of the 20th Century comes full circle with a modern view of Mariner Crater obtained by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in early March 1999.
Mariner 4 was the first spacecraft to reach the red planet and take close-up pictures that revealed its ancient, cratered surface. The picture on the left, above, is the 11th image taken by Mariner 4 during its July 1965 flyby. The center of the Mariner 4 image is dominated by a crater that is about 155 kilometers (96 miles) in diameter and located at 32°S latitude and 164°W longitude. The crater was named "Mariner" in 1967 by the International Astronomical Union in honor of its discovery by Mariner 4. The white arrow indicates the location of the new MGS MOC image.
The picture on the right represents an improvement in resolution of almost a factor of 400. It shows a view of a tiny portion of the southeastern floor of Mariner Crater, as it appeared to the MGS MOC in 1999. In 1965, it was a surprise to find that the martian surface is pocked with craters. In 1999, using the MGS MOC, we now have the ability to see objects the size of automobiles on the martian surface. This view of the Mariner Crater floor has a spatial resolution of 1.5 meters(5 feet) per pixel and covers an area only 1.5 km (0.9 mi) wide by 2.2 km (1.4 mi) long. Illumination is from the upper left in both the Mariner and MGS images. For a mercator-projected Viking 1 Orbiter view of this crater (obtained in 1978)click here.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01685: Mariner 4 Meets Mars Global Surveyor--Mariner Crater 1965 and 1999 sur le site de la NASA.
Figure caption from Science Magazine
Voir l'image PIA00807: Candor Chasma sur le site de la NASA.
During the first 1500 orbits (March through August, 1999) of the Mars Global Surveyor (MGS) mapping mission the Thermal Emission Spectrometer(TES) instrument has been measuring the surface brightness (albedo) of Mars. In this figure of all of the TES data acquired during that period have been combined to produce a detailed image of the Martian surface. The region shown includes the equatorial region of Mars where both the Pathfinder and Viking 1 spacecraft landed. The dark regions are areas swept free of dust by the Martian winds, whereas the brighter regions are areas of dust accumulation.
These bright and dark markings are known to change over time as the Martian winds move dust and sand across the surface. The TES measurements are providing a means of tracking these changes in very precise manner. Note that the Pathfinder landing site is located near the boundary between bright and dark regions and that the landing site is located in a region of modest dust accumulation.
The TES instrument was built by Raytheon Santa Barbara Remote Sensing and is operated at Arizona State University as part of NASA*s Mars Global Surveyor mission. The MGS mission is managed by the Jet Propulsion Laboratory in Pasadena, CA and operated in conjunction with Lockheed Martin Astronautics in Denver, CO.
Springtime at the middle and high latitudes on Mars means clouds. The clouds form as the seasonal (i.e., winter) polar cap frosts and snows sublime and carbon dioxide and water vapor are returned to the atmosphere. In early August 1998, clouds and hazes were especially prevalent over the northern plains of Mars, mainly between about 50°N and 75°N latitude.
As has been the case throughout the Science Phasing Orbit period, the challenge for the MOC team has been to try to guess, about 3 days in advance, which areas within the accessible latitude band will be relatively cloud-free for high resolution imaging. Often this is not possible, but as the season has progressed, the clouds have thinned. Thus, despite the clouds, a few pictures of the northern plains have shown some surface detail. Most of these pictures still appear "murky" because of the thin haze still present in the atmosphere.
This is the best example of MOC imaging of the Vastitas Borealis plains obtained as of mid-August 1998. MOC image 48107 covers an area approximately 4.6 kilometers (2.9 miles) wide and 12.9 kilometers (8.0 miles) long, centered at 64.54°N, 155.71°W, and is shown here at full spatial resolution (~5.5 m/pixel; ~18 feet/pixel). The context maps, identified below show that the MOC image is located north of Arcadia Planitia and several thousand kilometers northwest of the famous Olympus Mons volcano.
Context maps: Martian Landmarks. Digital shaded relief map showing location of MOC 48107 relative to familiar Martian landmarks. Regional Context. This Viking Orbiter photomosaic is at a scale of 64 pixels per degree of latitude. The large white box represents the area covered in the local context image. The small white box indicates the location of MOC image 48107. Local Context. This Viking Orbiter photomosaic is at a scale of 256 pixels per degree of latitude/longitude. The small white box in the center represents the location of the MOC image. The area containing the white box is also shown as a 2x enlargement in the lower right corner. The orange circle outlines a subtle crater that is seen as a bright mound (rather than as a crater) in the MOC image. This circular feature was targeted by the MOC team to provide a link between the MOC image and the lower-resolution Viking images of this location.
The northern plains of Mars have puzzled planetary scientists ever since they were recognized in images from the Mariner 9 orbiter in 1972. The northern plains of Mars are lower than most of the cratered terrains in the martian southern hemisphere, and these plains are considerably lower than the volcanic rises of Tharsis and Elysium. The northern plains have been generally assumed to consist of both volcanic surfaces--e.g., flood basalts--and windblown sediments. An alternative model--that the northern plains are blanketed by sediment from an ocean which might have once covered these lowlands--has gained some popularity recently.
High resolution images of the northern plains are rare. A few taken by the Viking Orbiters in the late 1970s (with resolutions 8-20 meters-- 26-66 feet--per pixel) revealed an eroded, layered landscape. The northern plains show a complex arrangement of old, eroded impact craters, partly buried craters, polygonal cracks that range in scales from tens of meters to tens of kilometers, and vast areas that appear relatively flat and featureless.
The MOC image shows a relatively featureless terrain with some circular depressions that are probably buried or partly buried impact craters. The hummocky (hilly) surface appears to be eroded--probably by wind-- but no windblown dunes or drifts are present. There are no obvious lava flow features in the image, although the area covered is so small that the likelihood of seeing such features is very small. The style of erosion suggests that the surficial material was not hard rock, lending some support for the idea that the surface material is a sedimentary deposit. Nothing in this picture, however, provides an adequate test of the competing models for the nature and origin of the northern plains surfaces (e.g., volcanic vs. oceanic vs. windblown materials).
The MOC image was taken during the 381st orbit of Mars Global Surveyor at 4:41 p.m. (PDT) on August 9, 1998. The local time (on Mars) was very early in the morning--the Sun had only risen 8.9° above the horizon--equivalent to about 5:20 a.m.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01467: Seeing Mars' Northern Plains Through Springtime Haze sur le site de la NASA.
10 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, windblown sand dunes on the floor of Brashear Crater in the southern hemisphere. The dominant winds responsible for these dunes blew from the southeast (lower right). Grooves on some of the dune surfaces suggest that the sand may be somewhat cemented; the grooves form by wind erosion.
Location near: 53.9°S, 119.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
One of the most striking discoveries of the Mars Global Surveyor mission has been the identification of thousands of meters/feet of layers within the wall rock of the enormous martian canyon system, Valles Marineris.
Valles Marineris was first observed in 1972 by the Mariner 9 spacecraft, from which the troughs get their name: Valles--valleys, Marineris--Mariner.
Some hints of layering in both the canyon walls and within some deposits on the canyon floors were seen in Mariner 9 and Viking orbiter images from the 1970s. The Mars Orbiter Camera on board Mars Global Surveyor has been examining these layers at much higher resolution than was available previously.
MOC images led to the realization that there are layers in the walls that go down to great depths. An example of the wall rock layers can be seen in MOC image 8403, shown above (C).
MOC images also reveal amazing layered outcrops on the floors of some of the Valles Marineris canyons. Particularly noteworthy is MOC image 23304 (D, above), which shows extensive, horizontally-bedded layers exposed in buttes and mesas on the floor of western Candor Chasma. These layered rocks might be the same material as is exposed in the chasm walls (as in 8403--C, above), or they might be rocks that formed by deposition (from water, wind, and/or volcanism) long after Candor Chasma opened up.
In addition to layered materials in the walls and on the floors of the Valles Marineris system, MOC images are helping to refine our classification of geologic features that occur within the canyons. For example, MOC image 25205 (E, above), shows the southern tip of a massive, tongue-shaped massif (a mountainous ridge) that was previously identified as a layered deposit. However, this MOC image does not show layering. The material has been sculpted by wind and mass-wasting--downslope movement of debris--but no obvious layers were exposed by these processes.
Valles Marineris a fascinating region on Mars that holds much potential to reveal information about the early history and evolution of the red planet. The MOC Science Team is continuing to examine the wealth of new data and planning for new Valles Marineris targets once the Mapping Phase of the Mars Global Surveyor mission commences in March 1999.
This image: Massive (non-layered) material exposed in central Candor Chasma. MOC image 25205 subframe shown at 11.7 meters (38.4 feet) per pixel resolution. Image shows the southern tip of a massive "interior deposit" that points like a giant tongue from Ophir Chasma (to the north) down into the center of Candor Chasma. The ridged and grooved bright unit is the "interior deposit." South of this ridged unit is a low elevation surface mantled by dark dunes and sand. Image covers an area approximately 5.7 by 5.7 kilometers (3.5 x 3.5 miles). North is approximately up, illumination is from the lower right. Image 25205 was obtained during Mars Global Surveyor's 252nd orbit at 2:45 p.m. (PDT) on April 20, 1998.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01460: Candor Chasma - Massive (non-layered) material expos sur le site de la NASA.
Mars Orbiter Camera (MOC)images of the Valles Marineris chasm walls obtained early in the Mars Global Surveyor (MGS) mission demonstrated that the upper martian crust--at least in the location of the Valles Marineris--is layered down to depths of several kilometers/miles. Over the past year, examination of additional MGS MOC images of other parts of Mars--including the vast, heavily cratered terrains of the red planet--also exhibit a layered crust. On Earth, geologists use the composition, texture, and sequence of layered rocks to decipher clues about the planet's history. Mars might offer a similar opportunity.
Shown here is a picture of Tagus Vallis in the martian southern hemisphere. The picture on the left shows this valley in a view that is about 7 kilometers (4.4 miles)wide by 11 kilometers (6.8 miles) high. Tagus Vallis is the deep, steep-walled valley that runs almost diagonally from upper left to lower right. The white box shows the location of the magnified view of the valley walls on the right. Layered rock can be seen, exposed in the upper slopes of the valley. Bright sand dunes are visible on the valley floor (lower left) and on the upland plain (upper right).
In this picture, the illumination is from the upper right. This image was obtained in April 1998 during the MGS Science Phasing Orbits imaging campaign. This result was presented at the 30th Lunar and Planetary Science Conference in Houston,Texas, March 1999.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Figure caption from Science Magazine
Voir l'image PIA00800: Medusae Fossae #1 sur le site de la NASA.
9 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layering in terrain at the high southern latitudes of Mars. South polar layers are commonly assumed to consist of varying amounts of dust and ice. An alternative explanation -- they may be exposures of ancient sedimentary rock.
Location near: 78.9°S, 10.1°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
The above figure shows the location of all high resolution (narrow angle) MOC images of the Cydonia region that have been obtained to date, including the first three taken in 1998 (PIA01240, PIA01241, AND PIA01440). These images are superimposed upon a mosaic of Viking images taken during the 1970's. Images acquired during the Science Phasing Orbit period of 1998 slant from bottom left to top right; Mapping Phase images (from 1999 and 2000) slant from lower right to upper left. Owing to the nature of the orbit, and in particular to the limitations on controlling the location of the orbit, the longitudinal distribution of images (left/right in the images above) is distinctly non-uniform. An attempt to take a picture of a portion of the "Face" itself in mid-February 2000 was foiled when the MGS spacecraft experienced a sequencing error and most of that day's data were not returned to Earth. Only the first 97 lines were received; the image's planned footprint is shown as a dashed box. This image is one in a series of eight.
Voir l'image PIA02384: Cydonia: Two Years Later sur le site de la NASA.
Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01157: Schiaparelli Crater Rim and Interior Deposits sur le site de la NASA.
Click here to view a full res version of MOC2_163a.
This pair of Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images shows the eastern third of a 4 kilometer-diameter impact crater located in Acidalia Planitia. The picture on the left is a MOC red wide angle camera context frame. It was taken at the same time as the narrow angle (i.e., high-resolution) camera image (right). Impact craters form by the sudden release of energy when an asteroid slams into a planet's surface at many miles per second. The high resolution MOC view (right) shows the walls, raised rim, and ejecta material thrown out of the crater during this blast. Similar features are seen at the famous Meteor Crater in northern Arizona, U.S.A.--except that this martian example is about 4 times larger than the one in North America. In this example, faint radial and concentric ridges and cracks in the crater ejecta are believed to arise from the motion of ejected material in a manner similar to thick pancake batter flowing across the surface.
The wide angle view (left) shows that many of the craters in Acidalia Planitia have a bright streak formed by wind transport of dust or sand. The narrow angle image (right) covers the full field of view of the MOC narrow angle camera--i.e., an area that is 3 kilometers (1.9 miles) wide. Both images are illuminated from the left/lower left. The images were acquired on July 15, 1999. The crater is located at 34.3°N latitude, 42.9°W longitude.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02093: Detail of an Impact Crater, Acidalia Planitia sur le site de la NASA.
Other information available for this image is the following: Orbit: 239 Range: 331.07 km Resolution: 2.5 m/pixel Image dimensions: 1024 X 9600 pixels, 2.5 km x 24 km Line time: 0.35 msec Emission angle: 2.35 degrees Incidence angle: 66.77 degrees Phase angle: 68.81 degrees Scan rate: ~0.15 degree/sec Start time: periapsis + 375 sec Sequence submitted to JPL: Mon 04/13/98 16:40 PDT Image acquired by MOC: Tue 04/14/98 07:02:17 PDT Data retrieved from JPL: Tue 04/14/98 17:30 PDT
Voir l'image PIA01240: Cydonia Region - Pass #2 sur le site de la NASA.
Dunes on Earth move downwind at different speeds depending upon the local wind conditions, the amount of loose sand available to be transported by wind, the shape and volume of the dunes, and overgrowths of vegetation. Typically, smaller dunes move faster than larger dunes. On Earth, some of the fastest-moving dunes that have been measured (e.g., in the deserts of Peru) move 10 to 30 meters (33 to 100 feet) per year. Small dunes usually have an almost crescent-shape to them, and are known to geologists as barchan dunes.
To look for evidence of dune movement on Mars, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has been used to re-visit some areas of known barchan dunes--because these types move the fastest--that were observed by the Mariner 9 orbiter in 1972 and the Viking 1 and 2 orbiters between 1976 and 1980. The picture above, left, shows a MOC high-resolution image taken December 25, 1999. The classic, crescentic shape of the dark barchan dunes can be seen in this picture. The steep slopes, also known as the dune slip faces, on these dunes are facing toward the southwest (north is up in both pictures). Thus, the shape of the dunes indicates that they are moving toward the southwest.
The picture above right shows the MOC image from December 1999 superimposed on a Viking 1 image taken May 27, 1978. During the 11 1/2 Mars years that passed between these two dates, it turns out that no difference can be detected in the position of the dunes seen in the MOC image and the Viking image. The earlier Viking image had a resolution of about 17 meters (56 ft) per pixel, while the MOC image had a resolution of about 3.8 meters (12 ft) per pixel. Although it looks like the dunes didn't move between the Viking and MOC images, this observation is limited by the resolution of the Viking image. It is entirely possible that the dunes have moved as much as 17-20 meters (16-66 ft) and one would not be able to tell by comparing the images. As it is, movement of less than 20 meters (66 ft) in 11 martian years (nearly 22 Earth years) is slower than some dunes of similar size and shape on Earth. Thus, it appears that martian dunes are not "experiencing" the level of activity commonly reported for some of the modern desert dunes found on Earth. The dune field illustrated in these pictures is located in a western Arabia Terra crater at 1.6°N, 351.6°W. Both the Viking and MOC images are illuminated from the left.
Voir l'image PIA02355: Movement of Whole Martian Dunes Difficult to Detect or Confirm sur le site de la NASA.
Figure caption from Science Magazine
Voir l'image PIA00809: Textures in south polar ice cap #1 sur le site de la NASA.
3 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows streaks created by late spring and early summer dust devils on a field of dark sand dunes on the floor of Hooke Crater.
Location near: 45.0°S, 44.8°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
The above figure shows the location of all high resolution (narrow angle) MOC images of the Cydonia region that have been obtained to date, including the first three taken in 1998 (PIA01240, PIA01241, AND PIA01440). These images are superimposed upon a mosaic of Viking images taken during the 1970's. Images acquired during the Science Phasing Orbit period of 1998 slant from bottom left to top right; Mapping Phase images (from 1999 and 2000) slant from lower right to upper left. Owing to the nature of the orbit, and in particular to the limitations on controlling the location of the orbit, the longitudinal distribution of images (left/right in the images above) is distinctly non-uniform. An attempt to take a picture of a portion of the "Face" itself in mid-February 2000 was foiled when the MGS spacecraft experienced a sequencing error and most of that day's data were not returned to Earth. Only the first 97 lines were received; the image's planned footprint is shown as a dashed box. This image is one in a series of eight.
Voir l'image PIA02383: Cydonia: Two Years Later sur le site de la NASA.
It has been known since the discoveries of Mariner 9 in 1972 that water once flowed on Mars and carved a variety of canyons, valleys, and channels. Some of this water appears to have gushed across the landscape in sudden, massive floods. Other valleys appear to be the result of water that flowed underground and sometimes caused the ground to collapse and sediment to be transported away. But one puzzle that has remained for more than 20 years--did any of these valleys experience sustained flow of liquid water at the martian surface over long periods of time?
MOC image 8704 (above) shows a portion of the meandering canyons of the Nanedi Valles system--one of several valleys that cut through the smooth and cratered plains of the Xanthe Terra region of Mars. The valley is about 2.5 km (1.6 mi) wide. The floor of the valley in the upper right corner of the MOC image exhibits a small, 200 m (660 ft) wide channel that is covered by dunes and debris elsewhere on the valley floor. The presence of this channel suggests that the valley might have been carved by water that flowed through this system for an extended period of time. In other words, instead of a massive, catastrophic flood, this valley might have been incised in a manner similar to rivers on Earth. The valley itself would have widened by a variety of processes in addition to the water flowing along the bottom of the channel--slumps and landslides, wind, and perhaps groundwater flow could have all contributed to these processes.
MOC image 8704 was taken on January 8, 1998. The scene covers 9.8 km by 27.9 km (6.1 miles by 17.3 miles). The image is centered on 5.1°N latitude and 48.26°W longitude. (CLICK HERE for a context image). North is approximately up, illumination is from the left. The image dimensions have been corrected from an original aspect ratio of 1.5. This image was also the subject of an earlier MGS MOC release on February 2, 1998.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
9 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a variety of textures observed on a south middle-latitude plain east-southeast of Hellas Planitia. Dark streaks left by passing dust devils are practically ubiquitous across the scene, including the transition from the texturally-smooth area (the majority of the image) onto the circular, rough feature near the right (east) edge of the image. The circular feature might once have been the site of an impact crater; perhaps this is the remains of its floor, and the rest of the crater and the rock in which it formed was removed by erosion.
Location near: 60.4°S, 242.5°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
(B) top: April 1998; bottom: January 2000.
Can Mars Global Surveyor's 1.5 meter (5 ft) per pixel camera be used to find any evidence as to the fate of the Mars Polar Lander that was lost on December 3, 1999? One way to find out is to look for one of the other Mars landers and determine what, if anything, can be seen. There have been three successful Mars lander missions: Viking 1 (July 1976), Viking 2 (September 1976), and Mars Pathfinder (July 1997). Of these, the location of Mars Pathfinder is known the best because there are several distinct landmarks visible in the lander's images that help in locating the spacecraft. The MGS MOC Operations Team at Malin Space Science Systems has been tasked since mid-December 1999 with looking for the lost Polar Lander. Part of this effort has been to test the capabilities of MOC by taking a picture of the landing site of Mars Pathfinder.
An attempt to photograph the Pathfinder site was made once before, in April 1998, by turning the entire MGS spacecraft so that the camera could point at the known location of the Mars Pathfinder lander. Turning the MGS spacecraft like this is not a normal operation--it takes considerable planning, and disrupts the on-going, normal acquisition of science data. It took 3 attempts to succeed, but on April 22, 1998, MOC acquired the picture seen on the left side of Figure A, above. The three near-by major landmarks that were visible to the Pathfinder's cameras are labeled here (North Peak, Big Crater, Twin Peaks). It was known at the time that this image was not adequate to see the Pathfinder lander because the camera was not in focus and had a resolution of only 3.3 meters (11 ft) per pixel. In this and all other images shown here, north is up. All views of the 1998 MOC image are illuminated from the lower right, all views of the 2000 MOC image are illuminated from the lower left.
As part of the Polar Lander search effort, the Mars Pathfinder site was targeted again in December 1999 and January 2000. Like the 1998 attempt, the spacecraft had to be pointed off of its normal, nadir (straight-down) view. Like history repeating itself, it once again took 3 tries before the Pathfinder landing site was hit. The picture on the right side of Figure A, above, shows the new image that was acquired on January 16, 2000. The white box indicates the location shown in Figure B (above, right). The 1000 m scale bar equals 0.62 miles.
Figure B (above) shows a subsection of both the 1998 image (top, labeled SPO-1-25603) and the 2000 image (bottom, labeled m11-2414) projected at a scale of 3 meters (10 ft) per pixel. At this scale, the differences in camera focus and sunlight illumination angle are apparent, with the January 2000 image being both in focus and having better lighting conditions. In addition, the MGS spacecraft took the 2000 image from a lower altitude than in 1998, thus the image has better spatial resolution overall. The 500 m scale bar is equal to about 547 yards. The white box shows the location of images in Figure C, below.
(C) higher-resolution view; left: April 1998; right: January 2000.
D) Erroneous, preliminary identification of Mars Pathfinder location in January 2000 image. Subsequent analysis (Figures E & F, below) identified the correct spot.
The third figure (C, above) again shows portions of the April 1998 image (C, left) and January 2000 image (C, right), only this time they have been enlarged to a resolution of 0.75 meters (2.5 ft) per pixel. The intrinsic resolution of the January 2000 image is 1.5 meters (5 ft), so this is a 200% expanded view of the actual M11-02414 image. The circular features in this and the previous images are impact craters in various states of erosion. Some boulders (dark dots) can be seen near the crater in the lower left corner. The texture that runs diagonally across the scene from upper left toward lower right consists of ridges created by the giant floods that washed through the Pathfinder site from Ares and/or Tiu Vallis many hundreds of millions of years ago. These ridges and the troughs between them were also seen by the Pathfinder lander; their crests often covered with boulders and cobbles (which cannot be seen at the resolution of the MOC image). The 100 m scale bar is equal to 109 yards (which can be compared with a 100 yard U.S. football field). The Mars Pathfinder landing site is located near the center of this view.
The fourth picture, Figure D (above), shows a feature that was initially thought to be the Mars Pathfinder lander by MOC investigators. This and the following figures point out just how difficult it is to find a lander on the martian surface using the MGS MOC. Figure D was prepared early in the week following receipt of the new MOC image on January 17, 2000, and for several days it was believed that the lander had been found. As the subsequent two figures will show (E, and F, below), this location appears to be in error. How the features were misidentified is discussed below. Both Figure D and Figure F, showing possible locations of the Pathfinder lander in the MOC image, are enlarged by a factor of three over the intrinsic resolution of that image (that is, to a scale of 0.5 meters or about 1 ft, 7 inch per pixel). The right picture in Figure D shows sight-lines to the large horizon features--Big Crater, Twin Peaks, and North Peak--that were derived by the MOC team by looking at the images taken by the lander in 1997. After placing these lines on the overall image, there appeared to be two features close to the intersection of the sight-lines. Based upon the consistency of the size and shape of the lander as illuminated by sunlight in this image, the northern of the two candidate features (the small "hump" at the center of both left and right pictures) was considered, at the time, to be the most likely. HOWEVER...
(E) Photoclinometry, Topography, and Revised Landing Site Location.
(F) Mars Pathfinder Landing Site; lander not resolved by MOC.
Later in the week following acquisition of the January 16, 2000, image (and over the following weekend), there was time for additional analysis to determine whether the rounded hump identified earlier in the week (Figure D, above) was, in fact, the Mars Pathfinder lander. A computer program that estimates relative topography in a MOC image from knowledge of the illumination (called "shape-from-shading" or photoclinometry) was run to determine which parts of the landing site image are depressions, which are hills, and which are flat surfaces. The picture at the left in Figure E (above) shows the photoclinometry results for the area around the Pathfinder lander. The picture at the center of Figure E shows the same photoclinometry results overlain by an inset of a topographic map of the Pathfinder landing site derived by the U.S. Geological Survey Astrogeology Branch (Flagstaff, Arizona) from photogrammetry (parallax measurements) using images from Pathfinder's own stereo camera. By matching the features seen by MOC with those seen by the Pathfinder (the large arrows are examples of the matching), the location of the lander was refined and is now indicated in the picture on the right side of Figure E. The large, rounded hump previously identified as Pathfinder in Figure D (above), is more likely a large boulder that was seen in Pathfinder's images and named "Couch" by the Pathfinder science team in 1997.
Figure F is summary of the results of this effort to find Mars Pathfinder: it shows that while the landing site of Mars Pathfinder can be identified, the lander itself cannot be seen. It is too small to be resolved in an image where each pixel acquired by the MOC covers a square of 1.5 meters (5 feet) to a side, given the contrast conditions on Mars and the MOC's ability to discriminate contrast. At this scale, Pathfinder is not much larger than two pixels, and the same is true of the lost Polar Lander.
No evidence has been found in the January 2000 MOC image of the aft portion of Mars Pathfinder's aeroshell or its parachute, either. If the aeroshell is laying on its side, as interpreted from Mars Pathfinder's images, then it would be very difficult to see this from orbit. Because Pathfinder did not image the parachute, it is not known how it may be configured on the surface--it could be wrapped around the aeroshell or a boulder, for example.
This effort to photograph the Mars Pathfinder lander demonstrates that it is extremely difficult to find a lander on the surface of Mars using the Mars Orbiter Camera aboard the MGS spacecraft. This analysis suggests that it is not very likely that the December 1999 Polar Lander will be found by MOC.
Voir l'image PIA02352: MOC's Highest Resolution View of Mars Pathfinder Landing Site sur le site de la NASA.
Among the geological features examined by MOC in recent weeks--the enigmatic "Giant Polygons" on the martian northern plains. In the 1970s the Viking Orbiters saw huge cracks , some more than 1 kilometer (0.62 miles) wide, arranged in a polygonal pattern that outlined flat-lying areas sometimes 5 to 20 kilometers (3 to 12 miles) across. Giant polygons are most common in parts of Utopia Planitia and Acidalia Planitia, but there is also a cluster of them in the lowlands west of the Elysium volcanoes, on Elysium Planitia.
The exact origin of the giant polygons has never been determined. At first glance, they appear to resemble mud cracks that one might see on the surface of a dried-up puddle, pond, or lake. However, mud cracks and the polygonal patterns they create are small features--like the size of a human hand. The giant polygons on Mars are big enough to hold the entire downtown area of a moderate-sized city.
Mud cracks form by dessication-- i.e., the removal of water by evaporation (drying). Many ideas about the polygons on Mars have centered on the idea that they are somehow related to the dessication of thick layers of wet sediment-- perhaps deposited by some of the giant floods that Mars is known to have had. However, there has been considerable debate about whether the polygons formed in lava instead of sediment. Cooling lava might also crack and give the polygon texture, some have argued. Two observations have been made--using Viking images--that constrain the types of origins that can be proposed: (1) most of the "cracks" appear to be graben- -down-dropped blocks caused by faulting, and (2) some of the "cracks" appear to indicate the outlines of buried craters. These observations suggest that whatever caused the polygons, the process appears to be confined to material that has buried older terrain.
The new MOC image confirms the impression--from Viking images--that the polygon cracks-- troughs--are graben formed by faults. Unfortunately, the image does not provide ample information to distinguish between the various models for the origin of the polygons or the material in which they occur. The images, however, do show features of interest. The floors of the polygon troughs have bright, almost evenly spaced, windblown ripples or drifts(see also detailed sub-areas). Similar drifts can also be seen in and encroaching upon the surrounding, small impact craters. These drifts attest to the movement of sediment on the surface, and their brightness and shape suggests that they have not been active recently.
MOC image 52706 was taken at about 11:36 p.m. (PDT) on August 31, 1998, during the 526th orbit of Mars Global Surveyor as the spacecraft was nearing its 527th periapsis (closest point to the planet during the orbit).
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01469: Giant "Polygon" Troughs, Elysium Planitia sur le site de la NASA.
How recent is "recent"? The small martian gullies discovered in Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) pictures of certain craters, troughs, and valleys between latitudes 30° and 70° appear to be geologically young. This means that, on the scale of a planet that is 4.5billion years old, the gullies may be only a few million, or less, years old. The youth of these gullies relative to the history of Mars is indicated by the lack of impact craters--formed by meteors--on the alcoves, channels, or aprons of these features. However, other evidence suggests that the gullies may, in many cases, be much younger than a few million years--in fact, some might be actively seeping water in modern times.
The first picture, "Apron Covering Dunes," shows a deep, prominent martian gully in a south-facing wall in Nirgal Vallis near 29.4°S, 39.1°W. Sunlight illuminates the scene from the upper left. At the bottom of the picture is a series of evenly-spaced, almost parallel ridges. These ridges are dunes created by windblown sand. The apron--the fanlike deposit at the lower end of the deep channel--at this location is seen covering some of the dunes. The sand dunes are thus older than the apron of debris that came from the channel. The dune field has no small meteor impact craters on it, so it, like the gully landforms, is geologically young--yet older than the apron. If the dunes are active in the modern environment--which is uncertain despite the apparent youth of the dunes--then the apron would have had to form within the past few centuries or less. This picture was taken in September 1999.
The second picture, "Apron on Polygons," shows aprons deposited at the base of the south-facing slope in an impact crater at 54.8°S, 342.5°W, in Noachis Terra. The slope and plains surrounding the apron materials have a bumpy pattern of evenly-spaced polygons. Polygonal patterns like this are common in the middle and high latitude regions of Mars, and, like their counterparts in the Arctic and Antarctic regions of Earth, probably form by stresses induced by seasonal and daily freezing and warming cycles of ice in the ground. Such polygons, where found on Earth, are usually only several to tens of thousands of years old, at most. The fact than an apron of debris covers such polygons, and no new polygons have formed on top of the apron, all suggest that the apron--and therefore the gully involved in slope erosion at this location--may be no more than a few tens of thousands of years old, and could be much, much younger. The aprons shown here are from the same July 1999 picture as shown in an accompanying release, "Basic Features of Martian Gullies;" the picture is illuminated from the upper left.
The third picture, "Fresh, Dust-free Surfaces," shows a January 2000 view of small, dark channels eroded into one of the gully alcoves found in the "Aerobraking Crater" located at 65°S, 15°W. Two aspects of this picture indicate that two of the processes that contribute to martian gully formation--liquid water seepage and downslope movement of dry, as well as wet, debris--have probably occurred in the near-recent past. In this case, near-recent could mean "within a few days of when the picture was taken" to "within a few years of when the picture was taken." One aspect is the sharp contrast between dark-toned and light-toned surfaces. On Mars, fine, bright dust can settle out of the atmosphere and eventually coat surfaces so that the contrast between dark and light terrains is hidden from view. There was an experiment on the Sojourner Rover in 1997, for example, that found dust to be settling out of the atmosphere almost all of the time during Mars Pathfinder's 83-day mission. If dust were settling on the alcoves and small channels shown here, they would not appear to be so dark relative to the surrounding, bright, dust-covered terrain. The other attribute of the picture that suggests relative youth is the preponderance of boulders and their sharp, crisp relief which indicates that they have not yet broken into finer debris, nor have they been covered up and mantled by sand or dust. Sunlight illuminates the scene from the upper right.
Voir l'image PIA01041: Evidence for Recent Liquid Water on Mars: Clues Regarding the Relative Youth of Martian Gullies sur le site de la NASA.
This image is illuminated by sunlight from the upper left.
Looking like pieces of sliced and broken swiss cheese, the upper layer of the martian south polar residual cap has been eroded, leaving flat-topped mesas into which are set circular depressions such as those shown here. The circular features are depressions, not hills. The largest mesas here stand about 4 meters (13 feet) high and may be composed of frozen carbon dioxide and/or water. Nothing like this has ever been seen anywhere on Mars except within the south polar cap, leading to some speculation that these landforms may have something to do with the carbon dioxide thought to be frozen in the south polar region. On Earth, we know frozen carbon dioxide as "dry ice." On Mars, as this picture might be suggesting, there may be entire landforms larger than a small town and taller than 2 to 3 men and women that consist, in part, of dry ice.
No one knows for certain whether frozen carbon dioxide has played a role in the creation of the "swiss cheese" and other bizarre landforms seen in this picture. The picture covers an area 3 x 9 kilometers (1.9 x 5.6 miles) near 85.6°S, 74.4°W at a resolution of 7.3 meters (24 feet) per pixel. This picture was taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) during early southern spring on August 3, 1999.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02367: Martian "Swiss Cheese" sur le site de la NASA.
These three images were taken on three different orbits over the north polar cap in April 1999. Each shows a different part of the same ice-free trough. The left and right images are separated by a distance of more than 100 kilometers (62 miles). Note the similar layers in each image.
A pair of Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images (above, center and right) shows close-up views of a sand dune field that was first detected by the Viking orbiters in the late 1970s (above, left). What is surprising about the MOC images is that they reveal a dune field unlike any other thus far seen on Mars--this one has impact craters on its surface, and LOTS of them!
The field of parallel ridges north of the dune field (above the white boxes in picture at the left) is a wind-eroded material named the Apollinaris Sulci. It is possible that the dune field shown here was once covered by this wind-eroded material and was later exhumed. Regardless, the dunes were somehow hardened and have been exposed as hard rock on the martian surface long enough for many impact craters smaller than a few hundred meters (few hundred yards) across to form. These dunes are therefore quite ancient--one might say that this is a "fossil" dune field. A similar effect at a much smaller scale can be seen by examining some sandstones and siltstones on Earth--if conditions were right, ripples formed in either water or wind are preserved in such rocks.
The first MOC view, labeled M03-00006, was taken on July 1, 1999. The second view, M07-05007, was acquired September 26,1999. Both MOC images and the Viking picture are illuminated from the left. The dune field occurs east of the Apollinaris Patera volcano and northeast of Gusev Crater at 12.5°S, 181°W.
The release for image B in the above caption can be found here.
Voir l'image PIA02360: Ancient Paleo-Dunes Battered by Impact Craters sur le site de la NASA.
Small valleys in the martian cratered highlands are often quite old and have been modified by erosion and wind action. The valleys shown here are located on a crater rim in Terra Tyrrhena. MOC took this picture in April 1999.
Flow ejecta craters are so named because the material blasted out of the crater during the impact process appears to have flowed across the surface of Mars. First seen in Mariner 9 images in 1973, and described in detail using Viking Orbiter images acquired in 1976-78, flow-ejecta craters are considered by many scientists to be evidence that liquid water could be found in the near-subsurface at the time the craters formed. This image, a factor of two better than any previous view of such features (and a factor of 33 better than the best Viking frame of the specific crater, 056A61), shows two smaller, pre-existing craters and the interaction of the flowing ejecta with these craters. The uppermost small crater has been over-topped and partly buried by the flow, while the flow has been diverted around the lower crater. Ridges formed where the flow "stacked up" behind obstacles, or came to rest.
Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01162: Flow-ejecta Crater in Icaria Planum - High Resolution Image sur le site de la NASA.
7 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a cluster of craters in far western Arabia Terra. The crater cluster is oriented along a line that runs nearly east-west (left-right) across the scene. Clusters of craters positioned along a line like this are secondary craters -- that is, they formed as the result of a much larger meteor, asteroid, or cometary impact somewhere else in the region. These craters do not form from the object that impacted Mars to form the larger, primary crater; these are the product of the impact of the rocks and debris thrown out by the larger impact.
Location near: 14.9°N, 19.3°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) orbits the red planet twelve times each day. The number of pictures that MOC can take varies from orbit to orbit, depending upon whether the data are being stored in MGS's onboard tape recorder for playback at a later time, or whether the data are being sent directly back to Earth via a real-time radio link. More data can be acquired during orbits with real-time downlink.
During real-time orbits, the MOC team often will take a few random or semi-random pictures in between the carefully-selected, hand-targeted images. On rare occasions, one of these random pictures will surprise the MOC team. The picture shown here is an excellent example, because the high resolution view (top) is centered so nicely on a trough and an adjacent, shallow crater that it is as if someone very carefully selected the target for MOC. The high-resolution view covers an area only 1.1 km (0.7 mi) wide by 2.3 km (1.4 mi) long. Hitting a target such as this with such a small image is very difficult to do, on purpose, because there are small uncertainties in the predicted orbit, the maps used to select targets, and the minor adjustments of spacecraft pointing at any given moment. Nevertheless, a very impressive image was received.
The high resolution view crosses one of the troughs of the Sirenum Fossae near 31.2°S, 152.3°W. The context image (above) was acquired at the same time as the high resolution view on July 23, 2000. The small white box shows the location of the high resolution picture. The lines running diagonally across the context image from upper right toward lower left are the Sirenum Fossae troughs, formed by faults that are radial to the volcanic region of Tharsis. Both pictures are illuminated from the upper left. The scene shows part of the martian southern hemisphere nearly autumn.
Voir l'image PIA01046: Sirenum Fossae Trough sur le site de la NASA.
26 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows gullies formed in the wall of a depression located on the floor of Rabe Crater west of the giant impact basin, Hellas Planitia. Gullies such as these are common features on Mars, but the process by which they are formed is not fully understood. The debate centers on the role and source of fluids in the genesis of these features.
Location near: 44.1°S, 325.9°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
Gully landforms proposed to have been caused by geologically-recent seepage and runoff of liquid water on Mars are found in the most unlikely places. They typically occur in areas that are quite cold--well below freezing--all year round. Like the old adage about moss on trees, nearly all of them form on slopes that face away from sunlight. Most of the gullies occur at latitudes between 30° and 70°.
The highest latitude at which martian gullies have been found is around 70°-75°S on the walls of pits developed in the south polar pitted plains. If you were at this same latitude on Earth, you would be in Antarctica. This region spends much of the winter--which lasts approximately 6 months on Mars--in darkness and at temperatures cold enough to freeze carbon dioxide (around -130°C or -200°F). Nevertheless, gullies with very sharp, deep, v-shaped channels are seen on the pit walls (above, left).
Based upon the locations of the tops of the channels on the slope shown here, the inferred site of liquid seepage is located at a layer in the pit wall about 1/3 of the way down from the top of the MOC image. The channels start wide and taper downslope. The area above the channels is layered and has been eroded by mass movement--dry avalanching of debris--to form a pattern of chutes and ridges on the upper slope of the pit wall. The top layer appears to have many boulders in it (each about the size of a small house), these boulders are left behind on the upper slopes of the pit wall as debris is removed.
Centered near 70.7°S, 355.7°W, the MOC image was acquired July 14, 1999, and covers an area approximately 2.8 km (1.7 mi) wide by 2.1 km (1.3 mi) high. Sunlight illuminates the MOC image from the upper left and north is toward the upper left. The context view (right) is from the Viking 2 orbiter and was acquired in 1977. The Viking picture is illuminated from the top/upper left; north is toward the upper right. The small white box in the context frame (upper right corner) shows the location of the high resolution MOC view.
Voir l'image PIA01034: Evidence for Recent Liquid Water on Mars: Gullies at 70°S in Polar Pit Walls sur le site de la NASA.
Elysium Mons was discovered by Mariner 9 in 1972. It differs in a number of ways from the familiar Olympus Mons and other large volcanoes in the Tharsis region. In particular, there are no obvious lava flows visible on the volcano's flanks. The lack of lava flows was apparent from the Mariner 9 images, but the new MOC high resolution image--obtained at 5.24 meters (17.2 feet) per pixel--illustrates that this is true even when viewed at higher spatial resolution.
Elysium Mons has many craters on its surface. Some of these probably formed by meteor impact, but many show no ejecta pattern characteristic of meteor impact. Some of the craters are aligned in linear patterns that are radial to the summit caldera--these most likely formed by collapse as lava was withdrawn from beneath the surface, rather than by meteor impact. Other craters may have formed by explosive volcanism. Evidence for explosive volcanism on Mars has been very difficult to identify from previous Mars spacecraft images. This and other MOC data are being examined closely to better understand the nature and origin of volcanic features on Mars.
The three MOC images, 40301 (red wide angle), 40302 (blue wide angle), and 40303 (high resolution, narrow angle) were obtained on Mars Global Surveyor's 403rd orbit around the planet around 9:58 - 10:05 p.m. PDT on July 2, 1998. The images were received and processed at Malin Space Science Systems (MSSS) around 4:00 p.m. PDT on July 4, 1998.
This image: MOC image 40303, shown at 25% of its original size. North is approximately up, illumination is from the right. Resolution of picture shown here is 21 meters (69 feet) per pixel. Image was received with bright slopes saturated at DN=255.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01455: Elysium Mons Volcano sur le site de la NASA.
30 October 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an outcrop of light-toned, layered, sedimentary rock in Aureum Chaos. The darker material, which includes ripples, is composed of windblown sand and granules. This scene is located near 3.8°S, 26.2°W, and covers an area roughly 7.7 km by 3 km (4.8 by 1.9 mi) wide. Sunlight illuminates the terrain from the top/upper right. This southern autumn image was acquired on 14 July 2006.
5 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a chain of collapse pits on the lower south flank of Ascraeus Mons. Pit chains such as this are the result of collapse along fault lines. In this case, before the collapses occurred, the fault was a conduit for molten rock -- magma -- which erupted to form a suite of lava flows (now covered by mantles of dust) that can be seen radiating away from the pit at the center of the image.
Location near: 7.2°N, 104.3°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
This picture is an enlargement of a portion of a MOC image taken in late July 1999, showing the onset of defrosting of the seasonal carbon dioxide frost cap (small, occasionally fan-shaped dark spots seen throughout this image). Two craters are seen in this image, a very rare occurrence on the south polar layered deposits. Shown for comparison at the same scale is a picture of Jack Murphy (now Qualcomm) Stadium in San Diego, California. Clearly visible in the inset is the baseball diamond and pitcher's mound; less clear but certainly visible are a number of automobiles (small light dots) in the parking lot west (to the left) of the stadium. The elevation of the sun in the Mars image is about 10°; the sunlight is coming from the bottom (north) in this image. The shadow of the rims of the craters can be used to determine their depths. The smaller crater in the bottom right corner is about 60 m (197 feet) across and 7 m (23 feet) deep; the large crater just below the inset is 175 m (574 feet) across and 17 m (56 feet) deep. Similar calculations for other features in the images indicate that much of the surface is smooth and flat. Relief is typically much less than 1-2 meters (3-7 feet) in height over areas of 10-15 meters across (33-49 feet).
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
One of the highlights of the Mars Global Surveyor Mars Orbiter Camera project thus far has been the realization that much of the upper crust--i.e., the bedrock--is layered. This dramatic view of a slope in the Amenthes Rupes region near the martian equator shows layered bedrock, smooth-surfaced debris at the slope base, and many small ripple-like dunes. The picture was taken during the second week of April 1999 and covers an area 3 kilometers (1.9 miles) wide. Illumination is from the lower right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Martian Dairy Products? If parts of the south polar cap can look like swiss cheese (see "Martian "Swiss Cheese""), then parts of the north polar cap might as well look like some kind of cheese, too. This picture shows a cottage cheese-like texture on the surface of a part of the residual--summertime--north polar cap.
The north polar cap surface is mostly covered by pits, cracks, small bumps and knobs. In this image, the cap surface appears bright and the floors of pits look dark. Based upon observations made by the Mariner 9 and Viking orbiters in the 1970s, the north polar residual cap is thought to contain mostly water ice because its summertime temperature is usually near the freezing point of water and water vapor was observed by the Vikings to be coming off the cap during summer. The south residual cap is different--its temperatures in summer remain cold enough to freeze carbon dioxide, and very little to no water vapor has been observed to come off the south cap in summer.
The pits that have developed on the north polar cap surface are closely-spaced relative to the very different depressions in the south polar cap. The pits are estimated from the length of shadows cast in them to be less than about 2 meters (5.5 feet) deep. These pits probably develop slowly over thousands of years of successive spring and summer seasons.
This picture was taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) during northern summer on April 5, 1999. The picture is located near 82.1°N, 329.6°W and covers an area 1.5 km wide by 3 km long (0.9 x 1.8 miles) at a resolution of 3 meters (10 ft) per pixel.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02369: "Cottage Cheese" Texture on the Martian North Polar Cap in Summer sur le site de la NASA.
3 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows two barchan dunes in the north polar region of Mars. The orientation of the dunes, with the steep faces pointed toward the southeast (lower right), indicates that the winds responsible for their formation blew from the northwest (upper left). At the time this image was acquired by MOC, the dunes and surrounding plains were covered by seasonal carbon dioxide frost.
Location near: 73.8°N, 40.8°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
Observation of dune activity--whether the movement of whole dunes or the movement of sediment on a dune--is the result of a direct link between the martian surface and its atmosphere. Observation of dune activity can be used to determine the rate at which wind moves sediment. It can also help to estimate how long it takes for windblown sand to abrade surfaces--including rocks and Mars landers.
One of the first sand dune fields ever recognized on Mars is shown here. Located on the floor of Proctor Crater (at 48°S, 330°W), this dune field was seen in Mariner 9images more than 27 years ago. In fact, the photomosaic base map in MOC2-170a (above, left) is constructed from Mariner 9 images taken in February and March of 1972. The thin strip overlain on the Mariner 9 mosaic is a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image taken in June 1999. The new MOC image shows evidence that the Proctor Crater dunes are active today.
The picture on the right is an expanded view of a portion of the MOC image (its location is indicated by the white box in the picture on the left). In this view (right), the sand dunes are dark and patches of southern winter frost are bright. The sun illuminates the scene from the upper left. Dark streaks can be seen on frost-covered slopes, particularly just left of the center of the picture. Thesestreaks result from recent avalanching of sand on the steep (up to 35°), down-wind side of the dune, otherwise known as the slip face. Because the dark sand streaks are superposed upon the bright frost, these streaks can only be as old as the frost. This frost cannot be more than 11 months old, and was probably only a few months old at the time the picture was taken. Thus, the dunes must be active today in order to show such streaks.
The placement of dunes in the MOC image was also compared with their positions in the earlier Mariner 9 image (above, left). No evidence that entire dunes have moved since March 1972 has been found. While the period of March 1972 to June 1999 is 27 Earth years, it is only about 14 Mars years. Looking for evidence of dune movement since 1972 is limited by the fact that the Mariner 9 images have spatial resolutions of about 62 meters (203 feet) per pixel--this means that the dunes would have to move more than about 62 meters before their motion could be clearly detected in a MOC image.
Taking the two results together--evidence for recent dune activity in the form of avalanches on slip faces versus lack of movement at the scale of 62 meters--helps to establish that (a) the dunes are active, but (b) they moved less than approximately 62 meters in 14 Mars years.
The 8 kilometer scale (upper left) indicates a distance of 5.0 miles. The 300 meter scale bar (lower right) represents 328 yards (984 feet). The Mariner 9 images are illuminated from the upper right, the MOC image from the upper left.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02304: Dune Activity in Proctor Crater sur le site de la NASA.
Observations during the first week of March 1999 were mostly aimed at acquiring quantitative and qualitative information about the Mars Orbiter Camera (MOC) in the environment in which it was originally designed to operate. Chief among the"calibration" data were measurements of the camera's focus, which is very sensitive to temperature because the magnification is so high. Using heaters around the rim (outer portion) and hub (inner portion) of the primary mirror to minutely change the shape of the mirror, pictures were taken of stars--which are "point sources" for accurate measurement--and of the north polar cap and polar dune fieldfor comparison between the theoretical quality of the image and the practical quality.
Two representative focus conditions are shown here. In each frame, the upper left corner of the left-hand image is shown enlarged 2-fold on the right. The star Omega 2 Scorpius is shown for comparison; its oblong shape is an indication of how far and in what direction focus lies. The closer to a symmetric "circle," the closer to focus. A comparison of the enlargements shows that subtle features are better discriminated in the image at 0.35 W hub (lower picture) than at 0.66 W rim (upper picture), indicating that heating of the inner portion of the mirror moves the camera closer to focus. The two MOC images show similar surfaces on the permanent north polar ice cap at nearly 1.5 meters (5 feet) per pixel. Each image (left side) shows an area about 578 meters (631 yards) wide; illumination is from the upper right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01670: MOC Focus Test Images sur le site de la NASA.
This type of bedrock layering has never been seen before in Valles Marineris. It calls into question common views about the upper crust of Mars, for example, that there is a deep layer of rubble underlying most of the martian surface, and argues for a much more complex early history for the planet.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01022: Western Tithonium Chasma/Ius Chasma, Valles Marineris - High Resolution Image sur le site de la NASA.
In December 1999, the MOC team finally had an answer! A dust devil, shown in the above left figure, was caught in the act of creating a swirly, dark streak! An eerie sensation washed over the first team members who saw this picture--here was an event on Mars "caught in the act" just hours before the picture was played back to Earth. A "smoking gun."
The first dust devil seen making a streak--located in Promethei Terra (above, left)--was traveling from right (east) to left (west). A columnar shadow was cast by sunlight coming from the upper left. This shadow indicates the true shape of the dust devil. The bright dust devil itself does not look like a column because the picture was taken from a camera looking straight down on it. The dust devil is less than 100 meters (less than 100 yards) wide and the picture covers an area approximately 1.5 by 1.7 kilometers (about 1 by 1 mile).
Dust devils are spinning, columnar vortices of wind that move across the landscape, pick up dust, and look somewhat like miniature tornadoes. Dust devils are a common occurrence in dry and desert landscapes on Earth as well as Mars. They form when the ground heats up during the day, warming the air immediately above the surface. As the warmed air nearest the surface begins to rise, it spins. The spinning column begins to move across the surface and picks up loose dust (if any is present). The dust makes the vortex visible and gives it the "dust devil" or tornado-like appearance. On Earth, dust devils typically last for only a few minutes.
The fourth picture (above, right) shows a surface in southwestern Terra Sirenum near 63°S, 168°W, that has seen the activity of so many dust devils that it looks like a plate of dark gray spaghetti. This image, taken in early summer during February 2000, covers an area 3 km wide and 30 km long (1.9 by 19 miles). In fact, a dust devil can be seen in the upper right of this image. Like the other pictures shown here, the Terra Sirenum image is illuminated by sunlight from the upper left.
Voir l'image PIA02378: Dust Devils Seen Streaking Across Mars: PART II--They're the Work of the Devil! sur le site de la NASA.
Recognizing that Mars is a desert planet, science fiction writers, scientists, and proponents of Mars exploration have, for decades, written and talked about "The Sands of Mars." The first martian sand dunes were observed by the Mariner 9 spacecraft in 1972. Ever since then, however, it has been unclear as to whether these dunes are active in today's extremely thin martian atmosphere (100 times thinner than on Earth at Sea Level), or if the dunes are the "fossil" remnants of a past epoch when the atmosphere was thicker and sand was more easily transported.
This year, the Mars Orbiter Camera (MOC), onboard the Mars Global Surveyor (MGS) spacecraft, made some key observations that appear to indicate that some martian dunes are active today. In fact, some dunes probably experienced activity--wind blowing the sand around--as recently as mid-1998.
Dunes typically contain granular fragments of rocks and minerals. These grains are usually 0.06 to 2 millimeters (0.002 to .08 inches) in size (which geologists call sand), and they are transported by the wind either by hopping over the ground (a process called saltation) or rolling along the ground (calledtraction). Images from the Mariner 9 and Viking orbiters of the 1970s did not have sufficient resolution to see detailed patterns of sand movement, although a few Viking images showed faint streaks emanating from a few dune fields; these were interpreted as possible indicators of sand movement.
Mars Global Surveyor has taken many images of martian dunes. Some dunes appear to be inactive and covered with dust. Other dunes, however, show all of the characteristics of fresh, active dunes. The most exciting examples have been found among the dunes in the martian north polar region.
The north polar cap of Mars (shown here in mosaics of Viking Orbiter 2images 065b56 and 065b58 of regional context andlocal context) is surrounded by a zone of dark (i.e., low albedo) dunes. These were first seen by Mariner 9 as a rippled texture, and by Viking as definitive sand dunes. Between late-July and mid-September 1998, the MGS periapsis (closest point in the spacecraft orbit relative to Mars) took the MOC right over the north polar dune fields four times a day. This provided many opportunities to take high resolution pictures of these dunes--resolutions that ranged from 1.5 to 5.0 meters (5 to 16 feet) per pixel.
The very first images of these north polar dunes--one of which was released via the World Wide Web on August 7, 1998--showed that they were coated with thin, bright frost that was left-over from the northern winter season that ended in mid-July. The first images also showed small dark spots along the bases of many of the dunes.
As more and higher-resolution images of the north polar dunes were taken, it became obvious that the dark spots on these dunes were areas where the seasonal frost coating had been removed--either by sublimation or by wind erosion--and that dark material was being exposed from underneath. The dark material was presumed to be the sediment that comprises the north polar dunes.
Some of the dark spots have thin, dark streaks emanating from them. These dark streaks are interpreted to be the result of wind action. The simplest explanation is that gusts of wind have blown the dark sand out across the frost-covered dunes, creating a streak of deposited sand over the frost. Some spots, as in the image shown here, have multiple streaks, each one indicating a different wind gust that moved in a different direction.
Because the frost that covers the north polar dunes can only be a few months old (i.e., northern winter lasted from mid-February 1998 to mid-July 1998), the dark streaks superposed on bright frost are clear indicators that dune material has been moved by the wind within recent months. The image shown here, MOC #50805, was taken on August 22, 1998. The streaks emanating from dark patches among the dunes in image 50805 must have formed sometime during 1998, and they most likely formed some time in July and/or August--once spring had begun in the northern hemisphere.
The observation of dark spots and wind streaks among the north polar dunes led the MOC science team to attempt to image the same dunes more than once. If the dunes are indeed active, then it would be possible--it was hoped--to see changes from one image to the next. Such changes could be used to (a) confirm that the dunes are active and (b) estimate the rate at which sand can be transported by wind under martian conditions. Since the MOC was turned off at the end of the Science Phasing Orbits in mid-September 1998, only about seven weeks (late-July to mid-September) were available to try to repeat an observation of a north polar dune field. Only once during this short span of time was there an opportunity to cross a dune field previously observed. A north polar dune field on the floor of an old impact crater was crossed by MOC twice--once on July 30, 1998, and again on September 2, 1998. However, it turned out that the two images crossedoutside the dune field, near the crater rim. It is quite difficult to image the same location twice with the MOC, because it cannot be pointed in a desired direction--it only "sees" what is beneath it. Minor fluctuations in the spacecraft orbit and attitude--due to variations in the martian gravity field and to upper atmosphere drag and inaccuracies within the attitude control system--led to the offset crossing.
The 1998 observations of the north polar dunes and other dune fields on Mars are quite tantalizing and appear to indicate that many dunes are active under present martian conditions. Confirmation of this result will await the Mapping Phase of the MGS mission, when it should be possible to take additional pictures of the same dune fields already observed by MOC. These new pictures will be compared with the ones from 1998 to see if any changes occurred. The Mapping Phase of the MGS mission is scheduled to commence in late-March 1999, and run for an entire martian year, into March 2001.
The results of the initial MOC study of martian sand dune activity are given in a paper entitled "Activity of Mars Eolian Dunes: Observation of a Low-Albedo Dune Field At High Spatial Resolution by the Mars Global Surveyor Camera," by MSSS Staff Scientist Kenneth S. Edgett and MOC Principal Investigator, Michael C. Malin, presented at the Geological Society of America Annual Meeting on October 29, 1998.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01495: Evidence for Recent Wind Action on Martian Sand Dunes sur le site de la NASA.
30 September 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows outcrops of south polar layered terrain. Their appearance in this July 2005 springtime image is enhanced by bright patches of carbon dioxide frost. The frost is left over from the previous southern winter season; by summer, the frost would be gone.
Location near: 84.6°S, 203.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
The second discovery made in this image are the small depressions found in the upper left and center of image (best seen in PIA01026) with faint dark lines crossing lighter floors. These depressions, and the pattern of lines, are similar to dry lake beds seen throughout the deserts of the southwestern United States. The light material may be salts or other minerals deposited as the lake evaporated, and the dark lines may be cracks created as the material dried out. Alternative explanations for the dark lines, involving freezing and thawing of water-saturated soil, are equally intriguing. In both cases, these features are the examples of a suite of such forms that can be used to diagnose the amount and distribution of surficial water that may have once ponded on Mars.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01025: Valley and Surrounding Terrain Adjacent to Schiaparelli Crater - High Resolution Image sur le site de la NASA.
Clouds have thus posed a real challenge for the MOC team, who are targeting high resolution images almost every day. Many of the high resolution images that were returned to Earth in early June 1998 were nearly white with clouds and haze. Very little detail could be seen on the ground.
The above picture illustrates one of the better cloudy images obtained by MOC. The haze was too thick to show much detail on the surface in the raw image, but in this case at least a dark lineation could be seen in part of the image. The full frame was nearly white everywhere except in the vicinity of the dark lineation. The MOC image, #35003, was obtained on Mars Global Surveyor's 350th orbit about the planet. The picture was taken around 4:00 a.m. PDT on June 7, 1998. The center of this subframe is at 8.03°N, 194.30°W. The dark lineation is one of the Cerberus Rupes--a set of dark lines (ridges or fractures) that cross the region southeast of the Elysium volcanic rise.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01444: Cloudy Image of Cerberus Rupes Dark Lineation sur le site de la NASA.
Dunes composed of low albedo (dark) sand grains encircle the north polar cap of Mars. This view was taken during the northern summer in May 1999.
The first time that the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC)team saw dark spots on defrosting dune surfaces was in August and September of 1998. At that time, it was the north polar seasonal frost cap that was subliming away (more recent images from 1999 have shown the south polar frosts). This picture (above) shows a small portion of the giant dune field that surrounds the north polar region, as it appeared on August 23, 1998. At the time, it was early northern spring and the dunes were still covered with winter frost.
Dark spots had appeared on the north polar dunes, and many of them exhibited a radial or semi-radial pattern of dark streaks and streamers. At first, there was speculation that the streaks indicated that the defrosting process might somehow involve explosions! The dark spots seemed to resemble small craters with dark, radial ejecta. It seemed possible that frozen carbon dioxide trapped beneath water ice might somehow heat up, turn to gas, expand, and then "explode" in either a small blast or at least a "puff" of air similar to that which comes from the blowhole of a surfacing whale or seal.
The image shown here changed the earlier impression. The dark spots and streaks do not result from explosions. The spots--though not well understood--represent the earliest stages of defrosting on the sand dunes. The streaks, instead of being caused by small explosions, are instead the result of wind. In this picture, the fine, dark streaks show essentially identical orientations from spot to spot (e.g., compare the spots seen in boxes (a) and (b)). Each ray of dark material must result from wind blowing from a particular direction--for example, all of the spots in this picture exhibit a ray that points toward the upper left corner of the image, and each of these rays indicates the same wind regime. Each spot also has a ray pointing toward the lower right and top/upper-right. These, too, must indicate periods when the wind was strong enough to move materials, consistently, in only one direction.
The sand that makes up the north polar dunes is dark. Each spot and streak is composed of the dune sand. The bright surfaces are all covered with frost. This picture is located near 76.9°N, 271.2°W, in the north polar sand sea. Illumination is from the lower left. The 200 meter scale also indicates a distance of 656 feet.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Until now, the vast northern plains of Mars have largely eluded the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) because these plains were obscured by winter and springtime clouds during most of the 1997 and 1998 Aerobraking and Science Phasing portions of the MGS Mission. However, now in March 1999 it is summertime in the northern hemisphere of Mars, and the northern plains are clearly in view. This image was taken at a resolution of 3 meters (10 feet) per pixel in order to characterize the nature of these plains. The image is located near Lomonosov Crater on the Vastitas Borealis plain. The image shows a patterned surface with two distinct rings that are suspected to be the locations of buried impact craters. The larger such ring (right) has dark spots clustered in several patches along its margins--these are fields boulders and rocks. The image covers an area 3 kilometers (1.9 miles) across and is illuminated from the lower left.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
2 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a view of frozen carbon dioxide in the south polar residual cap of Mars. Much of the south polar residual cap exhibits terrain that resembles stacks of sliced Swiss cheese, but this portion of the cap lacks the typical, circular depressions that characterize much of the region. Carbon dioxide on Mars freezes at a temperature of around 148 Kelvins, which is -125°C or about -193°F.
Location near: 87.2°S, 28.4°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02371: Gradual Contact Between North Polar Ice and Layers sur le site de la NASA.
19 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark streaks on a plain south of the giant impact basin, Hellas Planitia. The streaks map the routes traveled by dozens of individual southern spring and early summer dust devils.
Location near: 68.4°S, 296.1°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
In 1972, Mariner 9 images revealed a variety of branched and networked valleys on Alba Patera, a volcano in northern Tharsis. Since then, the question has always been, "what made these valleys, water or lava?" Because the Alba Patera volcano was considered to be a relatively young feature on Mars, it seemed that if waterways involved in the formation of the valleys, then it would imply that liquid water flowed on this part of Mars at a relatively recent time in the planet's history. Thus, it was hoped that Mars Global Surveyor (MGS), with its super-high resolution Mars Orbiter Camera (MOC), would help answer this key question about evidence for past water on the red planet.
However, when MOC peered down upon these valleys it became clear that the camera might not help answer the question of their origin. As the picture above shows, these valleys--which trend from lower right to upper left in the picture--are old and have been cut by younger faults that created graben--e.g., the wide, straight valley running diagonally from upper right to lower left. Worse, the close-up views revealed that the valleys are covered up by a lumpy-textured material that also partly fills nearby impact craters. The origin of the textured material is unknown but might result from years and years of wind erosion of surface "soil" or volcanic ash. However it formed, this covering obscures so much of the details of the valleys that high resolution pictures are unlikely to solve this mystery.
The picture above covers an area approximately 8 kilometers (5 miles) wide by 15 kilometers (9 miles) high. Illumination is from the right. The picture was acquired in August 1998 during the MGS Science Phasing Orbits imaging campaign, and was presented at the 30th Lunar and Planetary Science Conference in Houston, Texas, March 1999.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
20 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered, sedimentary rock exposures in the Sinus Meridiani region.
Location near: 4.8°N, 1.2°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
Ascraeus Mons Volcano:
Like Earth, Mars has many volcanoes and volcanic features. This high-resolution view shows some of the lava flows near the summit of Ascraeus Mons, one of the three giant shield volcanoes known as the "Tharsis Montes." Volcanoes form when magma (molten rock) erupts out onto the surface of a planet. Based on Viking-era observations, Ascraeus Mons is considered to be one of the tallest volcanoes on Mars... its summit is more than 11 km (6.8 miles) above the surrounding plain. The summit is more than 23 km (14 miles) higher in elevation than the place where Mars Pathfinder landed in July 1997.
Description of MOC Image:
This picture shows an area that is about 20 km (12 miles) higher in elevation than the Mars Pathfinder landing site. The picture shows three main features: (1) a crater at the center-right, (2) a sinuous, discontinuous channel across the upper half, and (3) a rough and pitted, elevated surface across the lower half of the image.
(1) Crater at center right. Distinguishing meteor craters from volcanic craters can sometimes be a challenge on Mars. This particular crater was most likely formed by meteor impact because it has a raised rim and a faint radial ejecta pattern around the outside of it. This crater is 600 m (2000 feet) across, about 3/4 the size of the famous "Meteor Crater" near Winslow, Arizona.
(2) Sinuous channel. The type of discontinuous channel running across the upper half of the image is sometimes referred to as a "sinuous rille." These are common on the volcanic plains of the Moon and among volcanoes and volcanic plains on Earth. Such a channel was once a lava tube. It is running down the middle of an old lava flow. The "tube" looks like a "channel" because its roof has collapsed. The discontinuous nature of this channel is the result of the collapse, or "cave-in" of what was once the roof of the lava tube. It is common for certain types of relatively fluid lavas to form lava tubes. As it is being emplaced, the outer margins of the lava flow cool and harden, but the interior remains hot and continues to flow down-hill. Eventually, the eruption stops and the lava inside the tube cools, contracts, and hardens, leaving behind a tube (basically, a long narrow cave).
(3) Rough elevated surface. The rough, pitted, and elevated surface across the bottom half of the image is a lava flow. The margins of this feature are somewhat lobate in form, and the entire feature is elevated above its surroundings, indicating that it was the last lava flow to pour through this region.
Putting it All Together: Aa and Pahoehoe Lava Flows:
Shield volcanoes such as Ascraeus Mons form from relatively fluid lavas. Shield volcanoes on Earth include the well-known Islands of Hawai'i. The kind of lava that is fluid enough to make shield volcanoes is called basalt. This is an iron- and magnesium-rich silicate lava that, when cooled, is usually black or very dark brown.
Basalt lava flows come in two main varieties: Aa and Pahoehoe. These are Hawai'ian names. "Aa" (pronounced "ah-ah") lava flows have very rough, jumbly surfaces, and they usually lack lava tubes. "Aa" lava flow surfaces are very rough to walk on-- thus the term "aa" probably refers to the sound a person might make when walking on a cooled/solidified aa flow in bare feet!
"Pahoehoe" (pronounced "pa-hoy-hoy") is a term that means "ropey." The surfaces of pahoehoe lava flows are generally very smooth and billowy. Sometimes they have a ropy texture like melted taffy or caramel. Pahoehoe flows very commonly contain lava tubes.
The rough-surfaced flow across the lower half of the MOC image is interpreted to be an "aa" lava flow, and the smoother surface with a sinuous channel running down its center is interpreted to be a "pahoehoe" lava flow. Both would indicate that the lavas on Ascraeus Mons, at least at this location, are probably composed of basalt.
More Picture Information:
This MOC picture is a subframe of image #26705, centered approximately at 11.5°N latitude, 103.5°W longitude. It was taken on April 28, 1998, at 4:23 AM Universal Time, on Mars Global Surveyor's 267th orbit around Mars. Orbit 267 was the second-to-last orbit on which observations were obtained before Mars and the spacecraft passed behind the Sun for several weeks known as "Solar Conjunction."
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.http://www.jpl.nasa.gov/galileo/sepo
Voir l'image PIA01431: Lava Flows On Ascraeus Mons Volcano sur le site de la NASA.
Dark streaks, everywhere! Many Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images of the middle latitudes of the northern and southern hemispheres of Mars show wild patterns of criss-crossing dark streaks. Many of these streaks are straight and narrow, others exhibit curly arcs, twists, and loops. They often cross over hills, run straight across dunes and ripples, and go through fields of house-sized boulders. The two examples shown above were acquired in the last three months. Both pictures are illuminated by sunlight from the upper left. The first picture (left), showing dark streaks on the rippled flats of Argyre Planitia, covers an area 3 km by 5 km (1.9 by 3.1 miles) at a latitude of 51°S. The second picture (right) shows an area approximately 3 km by 5 km in Promethei Terra at a latitude of 58°S.
For many months the MOC science team was seeing streaks such as these, but were uncertain how they formed. One speculation was that they might result from the passage of dust devils. Each dust devil would leave a dark streak by removing bright dust from the terrain in its path, revealing a darker surface underneath. An image described by the MOC team in July 1998 showed examples of streaks that were, at the time, speculated to be caused by dust devils.
Voir l'image PIA02376: Dust Devils Seen Streaking Across Mars: PART 1--What Are These? sur le site de la NASA.
The upper layer of the plains surrounding this impact crater have been stripped and deflated by wind. The rocky ejecta of the crater, however, protected the material beneath the ejecta blanket from such erosion. This process also gives the ejecta deposit a "raised relief" appearance. MOC image from July 6, 1998.
Peering down into craters offers Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) scientists an opportunity to examine one of the few landforms that Mars shares in common with the other planets and moons of our Solar System.
The picture on the left (above) is a MOC context frame taken at the same time as the MOC high resolution image on the right. The white box on the left shows the location of the high resolution view. The high resolution image was targeted on a 3 kilometers (1.9 miles) wide impact crater on the floor of a larger crater in the Nepenthes Mensae region (near 3°S, 239°W). The context image is about 115 km (71 mi) across, the high-resolution image is 3 km (1.9 mi) across, and both are illuminated from the left/lower left.
The 3 km diameter crater in the MOC image on the right is three times wider than the famous Meteor Crater in northern Arizona, USA. The high resolution image shows many small windblown drifts or dunes in the low areas both within the crater and outside on the surrounding terrain. Some portions of the crater's walls exhibit outcrops of bare, layered rock. Large boulders have been dislodged from the walls and have tumbled down the slopes to the crater floor. Many of these boulders are bigger than school buses and automobiles.
Voir l'image PIA02343: Layers and Boulders in Crater Wall, Nepenthes Mensae Region sur le site de la NASA.
11 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some typical relations between impact craters and light-toned, layered rock on Mars. The larger circular feature at the north (top) end of the image marks the location of a filled, buried crater on intermountain terrain north of Hellas Planitia. The larger crater at the southeast (lower right) corner formed by meteor impact into the layered material in which the buried crater is encased. The layered rock, in this case, has a light tone similar to the sedimentary rocks being explored by the Mars Exploration Rover, Opportunity, thousands of kilometers away in Sinus Meridiani.
Location near: 24.9°S, 299.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
Valles Marineris a system of troughs, chasms, and pit chains that stretches more than 4,000 km (2,500 miles) across the martian western hemisphere. Outcrops of layered material found in mounds and mesas within the chasms of the Valles Marineris were known from the pictures taken by Mariner 9 in 1972 and the Viking orbiters of 1976-1980. One example of the those known previously is the mesa labeled "Candor Mensa" in the context image (above); another example is the mound in the center of Ganges Chasma. For several decades, it has been widely speculated among Mars scientists that the light- and dark-toned layered materials in the Valles Marineris might have formed in lakes that had once filled the chasms during the most recent epoch of martian history; others thought they might result from volcanic ash deposited in the chasms. Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images have confirmed the presence of light- and dark-toned layered sedimentary rock outcrops in the Valles Marineris, but they have also revealed many more than were previously known and they have shown several good examples that these materials are coming out of the walls of the Valles Marineris chasms. The fact that these materials come out of the chasm walls means that the layers do not represent lakes (or volcanic debris) that formed in the Valles Marineris. Instead, they represent materials deposited and buried long before there ever was a Valles Marineris. They are seen now because of the faulting and erosion that opened up and widened the Valles Marineris troughs. The context image is a mosaic of Viking 1 orbiter images taken in 1976 showing a portion of the wall that separates western Ophir Chasma from western Candor Chasma in the Valles Marineris. This area is located around 5°S, 74°W. The white box labeled "M17-00467" shows the location of a subframe of MOC image M17-00467 that was acquired in July 2000 to allow scientists to examine one of the many bright patches (indicated by small arrows) seen on the walls of Valles Marineris. The release image is a subframe of MOC image M17-00467, showing a high-resolution view of one of the bright patches on the walls of Candor Chasma. The MOC image reveals that the bright material indeed consists of light-toned layered rock similar to other outcrops thought to be sedimentary in origin found throughout the Valles Marineris. The dark ridge running from top center to center-left in this view is mantled by a smooth, dark material that covers additional light-toned layered rock. The observation that these kinds of bright layered rock occur within the walls of the Valles Marineris indicate that the materials are very, very old. They have been buried under several kilometers (i.e., more than a mile) of additional layered rock, all of which is beneath plains thought to be more than 2.5 to 3.5 billion years old. These relationships suggest that all of the layered sedimentary rocks observed on Mars by MGS MOC may date back to the earliest parts of martian history, between 3.5 and 4.5 billion years ago. In both pictures, north is toward the top. Sunlight illuminates the context image from the top/right; the MOC image (top left) is illuminated from the upper left.
Voir l'image PIA02847: Light-toned Layered Outcrops in Valles Marineris Walls sur le site de la NASA.
The lava flows and channels on the flanks of the Alba Patera volcano are mostly obscured by a covering of eroded, lumpy-textured material of unknown origin. This picture was taken in July 1998.
Remnant frost from the retreating south polar ice cap, trapped in cracks, enhances the visibility of polygonal patterns in this new picture of Malea Planum in the far southern regions of Mars. This scene, taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in October 1999 shows a relatively smooth portion of Mars (a plain) that is covered with polygons both at large and small scales. Smaller polygons are mostly found on the surfaces of old, mantled impact craters (e.g., top and lower center), while larger polygons are evident on the surfaces between the craters. (Note: The polygons are too small to see in the above image--click on it to see the full-resolution image and the polygons).
It is spring in the southern hemisphere of Mars, and the region shown here has recently emerged from beneath a winter coating of frost. Patches of frost (bright material) remain in the cracks that make up the edges of each polygon in the picture. The image covers a narrow strip of martian terrain only 1.5 km (0.9 mi) across at a resolution of 3 meters (10 ft) per pixel.
Polygons such as these are common in Earth's arctic and antarctic regions and they usually indicate the presence of ice (i.e., frozen water) in the ground. Polygons form from the cycle of freezing and thawing of ground ice over the course of years, decades, and centuries. The fact that polygons are found on all surfaces in the Malea Planum scene shown here indicates that the ice is not too deeply buried because only a thin veneer (a few meters--or yards) of material appears to have covered the crater at the top of the scene.
Voir l'image PIA02344: Patterned Ground of the Martian Antarctic sur le site de la NASA.
Relief model of the topography of the North Polar Region showing the form of the ice cap and its surroundings.
12 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of a large landslide deposit on the floor of western Tithonium Chasma.
Location near: 4.3°S, 87.9°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Summer
This picture is the first MOC high resolution image that showed the contact between the Lycus Sulci uplands and Amazonis Planitia lowlands. In this subframe of MOC image SPO 1-225/03, Amazonis and Lycus Sulci are separated by a subtle rise that runs diagonally across the scene from near the lower left toward the upper right. The Amazonis plains are toward the top of the picture, the Lycus Sulci uplands are toward the bottom. Both surfaces have been cratered by small meteoroid impacts. The Amazonis plains surface has many small, nearly parallel ridges that may have formed by wind erosion. These ridges are not found on the Lycus Sulci surface. None of the features seen in this image look like typical seashore landforms found on Earth--i.e., there are no beaches, windblown coastal dunes, or even the wave-cut cliff that was thought to exist on the basis of previous Viking images. The picture is illuminated from the lower right and was acquired in April 1998.
Lycus Sulci is the name of a region of hills and ridges located north and northwest of the famous giant volcano, Olympus Mons (see inset, above). Viking images of the area where the western margin of the Lycus Sulci meets the smooth Amazonis plains (upper left in the figure above) led some researchers to conclude that the two surfaces were in contact along a cliff. The proposed cliff faces toward the smooth plains, and thus it was suggested that this might be the kind of cliff that forms from erosion by waves in a body of water as they break against a coastline.
During the first year that Mars Global Surveyor (MGS) was orbiting the red planet (1997-1998), the Mars Orbiter Camera (MOC) acquired three high-resolution images along the contact between the Lycus Sulci hills and the Amazonis plains. The location of the portion of each image that is illustrated below is shown in this figure by a small, white box identified by the archival image number (e.g., "SPO2-428/03" refers to the 3rd image taken on the 428th orbit during the Science Phasing Orbits 2 phase of the MGS mission). The regional context view shown here is a portion of Viking orbiter image 851A29; its center is near 32°N, 114°W and it is illuminated from the right.
MRPS 95319
Lycus Sulci and Amazonis Planitia are shown here separated by a rise that runs diagonally across the scene from near the lower left toward the upper right. This picture is a subframe of MOC image SPO2-428/03, taken in July 1998. The Lycus Sulci uplands here are more roughly-textured than in the previous image, and the flat Amazonis plains appear to be more smooth and lack the small parallel ridges seen in the earlier view. The lack of the small ridges might be real, or they might be present but cannot be seen because this picture has a lower resolution than the previous one. This image, too, shows that the contact between Amazonis and Lycus Sulci is not a cliff, and once again there are no features that can be unambiguously identified as coastal landforms.
MRPS 95320
This is the third MOC image obtained during the first year of MGS operations that shows the contact between Lycus Sulci and Amazonis Planitia. This picture, a subframe of SPO2-483/08, was taken in August 1998. The Lycus Sulciup lands at this location dominate the lower half of the picture, while the Amazonis plains cover the upper half. The uplands here exhibit many small buttes (bumps or knobs in lower right of the scene), and the contact zone between the upland and lowland includes a triangular-shaped ridge (center/right). As with the earlier views of the contact between Lycus Sulci and Amazonis, no features of obvious origin by coastal processes (e.g., erosion by waves crashing against ashore) are seen. The scene is illuminated from the right.
The first picture above shows the regional context of a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) high-resolution image that was targeted in August 1998 with the intent to test the hypothesis that the northern plains of Mars were once the site of a vast ocean of liquid water. The second picture shows the resulting MOC image, numbered SPO2-515/05 and located at 40.0°N, 6.0°W in the transition zone between the Cydonia region and Acidalia Planitia, Mars.
The context image (first picture) includes several dark lines, some of which are labeled I and some are labeled G. These dark lines were proposed in previous, peer-reviewed scientific papers to be possible ocean shorelines located along the margins of the martian northern plains. Line I was called the Interior Plains Boundary, and line G was called the Gradational Boundary. The MGS MOC high resolution image was targeted such that it would examine the nature of line I, the Interior Plains Boundary.
The second figure shows the MOC high resolution view. The picture on the left side of the figure (second image) is the full MOC image and the white box indicates the location of the expanded view to the right. In the expanded view (the center of the figure), the location of line I--the proposed shoreline--is shown by a dashed curve. The dashed curve follows a subtle, shallow trough. None of the types of coastal landforms common on Earth--such as a beach, wave-cut cliff or terrace, or coastal dune fields, are seen at this location. If an ocean had once been present, then the water would have covered the top 2/3 of the expanded view--i.e., water would have lapped up against the rounded mounds in the lower 1/3 of this picture. Instead of coastal landforms, the MOC image exhibits a dark surface in its upper 1/3. The dark surface covers older, rounded hills and has a low, lobate escarpment along its southern margin. This escarpment faces south--that is, it faces toward the once-proposed coastline. In other words, the escarpment faces in a direction opposite of what would be expected for a coastal environment.
The context picture uses Viking orbiter image 561a24 as a base.
MRPS 50586
Mars Global Surveyor's (MGS) Mars Orbiter Camera (MOC) took the above picture (second of the two) of some massifs and mesas in the Cydonia region of Mars in early September 1998. The purpose of this image--number SPO2-532/04--was to test the hypothesis that the martian northern plains were once the site of an ocean or large sea. According to this hypothesis, and according to peer-reviewed and published maps, each one of the mesas and massifs in the two pictures above should have shorelines around their margins. The hypothesis holds that these were once islands and that waves would lap--and sometimes crash--against these landforms, rip off huge chunks of rock, and create steep cliffs and stair-stepped terraces in the rock.
The first picture above shows the regional context of the MOC high resolution view in Cydonia. The context picture, from Viking orbiter image 227S11, is illuminated from the right. The second picture above is a figure that shows the full SPO2-532/04 MOC image and two expanded views of portions of this image. Mesas are flat-topped uplands, and massifs are the more triangular, massive peaks. If an ocean had been present in this region, terraces that indicate erosion or bathtub rings of salt or carbonate deposits left by the retreat of this ocean as it dried up might be found around each mesa and massif. No such features are found, nor is it at all obvious why these mesas and massifs were portrayed in previously published figures as having shorelines around them. The MOC image is illuminated from the left.
If the northern plains of Mars had ever been the site of a vast ocean, then any highlands that protrude above these plains might be expected to exhibit shorelines. The somewhat curved, flat-topped mesa seen in Viking image 026A72 (first image) is bounded by a dark band. Prior to the Mars Global Surveyor (MGS) mission, this mesa was interpreted by some researchers as having been a possible island in an ancient, northern plains ocean. The dark band was interpreted to be a shoreline resulting from the action of waves lapping against the island's coast.
A high resolution image of the banded mesa--located on the Acidalia plains around 45°N, 7°W--was acquired by the MGS Mars Orbiter Camera (MOC) in August 1998, over twenty years after the Viking image was taken. A subframe of this image--SPO2-515/06--is shown in the second image. In the MOC image, the dark band resolves into a series of narrower bright and dark bands. Each band has a slightly different texture and brightness. Furthermore, what appeared to be a sunlit escarpment bounding the north side of the mesa in the Viking image appears in the MOC image to be only a shallow slope rather than a scarp or cliff. The origin of the different bands is not known, but the most likely explanation that would be consistent with other MOC observations of Mars is that the mesa consists of layered rock, and that each band is an outcropping of a different layer of this rock. The different textures would result from the differing resistance to erosion of each layer. Both images shown here are illuminated from the left.
Voir l'image PIA02338: Mars Shoreline Tests: Contact between Lycus Sulci and Amazonis Planitia sur le site de la NASA.
14 February 2006
Happy Valentine's Day from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) team!
This somewhat heart-shaped, eroded and partially-filled crater is located near the southeast wall of Columbus Crater in the Mare Sirenum region of Mars. North is toward the bottom/lower left.
Location near: 29.9°S, 165.2°W
Image width: 400 meter scale bar = ~1,312 feet
Illumination from: lower right
Season: Southern Autumn
Figure caption from Science Magazine
Voir l'image PIA00811: South polar region sur le site de la NASA.
Mars Global Surveyor's Mars Orbiter Camera is providing geologists with vistas that rival that of the aerial photographs they use in their field work on Earth. This picture shows the margin of a large lava flow located on Daedalia Planum, southwest of the Arsia Mons volcano. The picture covers an area only 1.5 kilometers (0.9 miles) wide and 2 kilometers (1.2 miles) long. The lava flow surface (upper portion of the frame) is rough but mantled with fine sand or dust. The ripples along the base of the lava flow margin are spaced about 15 meters (50 feet) apart and were formed by wind. Illumination is from the upper left.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
MOC "sees" by the dawn's early light! This picture was taken over the high southern polar latitudes during the first week of May 1999. The area shown is currently in southern winter darkness. Because sunlight is scattered over the horizon by aerosols--dust and ice particles--suspended in the atmosphere, sufficient light reaches regions within a few degrees of the terminator (the line dividing night and day) to be visible to the Mars Global Surveyor Mars Orbiter Camera (MOC) when the maximum exposure settings are used.
This image shows a bright, wispy cloud hanging over southern Malea Planum. This cloud would not normally be visible, since it is currently in darkness. At the time this picture was taken, the sun was more than 5.7° below the northern horizon. The scene covers an area 3 kilometers (1.9 miles) wide. Again, the illumination is from the top.
In this frame, the surface appears a relatively uniform gray. At the time the picture was acquired, the surface was covered with south polar wintertime frost. The highly reflective frost, in fact, may have contributed to the increased visibility of this surface.
This "twilight imaging" technique for viewing Mars can only work near the terminator; thus in early May only regions between about 67°S and 74°S were visible in twilight images in the southern hemisphere, and a similar narrow latitude range could be imaged in the northern hemisphere. MOC cannot "see" in the total darkness of full-borne night.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
It seems like only yesterday. Mars Global Surveyor (MGS) first reached the red planet two years ago on September 11, 1997 (Pacific Daylight Time). The very first high resolution picture acquired by the Mars Orbiter Camera (MOC) was obtained on the spacecraft's third orbit on September 15, 1997. This first picture was also the first twilight image obtained by MOC--the sun had already set and was about 1°below the local horizon. Scattering of sunlight reflected off airborne dust allowed a small portion of the floor of Lasswitz Crater--a 122 km (76 mi) diameter basin located at 9.4°S, 221.6°W--to be seen by the MOC on this first of many thousands of images that were to be obtained. The MGS spacecraft flew over Lasswitz Crater again on July 9, 1999--almost 1 martian year later. The new image taken by MOC had much better viewing conditions--the sun was in a 2 p.m. configuration, the camera was in focus, and the spacecraft altitude was low enough that the picture obtained has a resolution of about 1.8 meters (6 feet) per pixel.
Figure 177-A (left) shows Lasswitz Crater as it appeared on July 9, 1999. Sunlight illuminated the scene from the upper left. The two white boxes indicate the locations of the very first MOC narrow angle image taken from orbit around Mars(15 SEPT 97) and a higher-resolution view taken during a recent Mapping Phase orbit (09 JULY 99). The picture was taken by the MOC red wide angle camera at the same time that the 09 JULY 99 narrow angle frame was acquired. The picture has been map-projected so that north is up.
Figure 177-E (right) shows the September 1997 image overlain by the July 1999 image (darker inset) to show where the more recent image is located within the earlier view. North is up and illumination is from the left. The larger image covers an area approximately 5.5 km (3.4 miles) wide and 12 km (7.5 miles) long. The smaller view is 1.5 km (0.9 mi) wide.
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Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02331: Mars Global Surveyor MOC Celebrates 2 Years in Orbit! sur le site de la NASA.
This is a Mars Orbiter Camera view of the cratered uplands located between the Amenthes Fossae and Hesperia Planum. This ancient, cratered surface sports a covering of windblown dunes and ripples oriented in somewhat different directions. The dunes are bigger and their crests generally run east-west across the image. The ripples are smaller and their crests run in a more north-south direction. The pattern they create together makes some of the dunes almost appear as if they are giant millipedes!This picture covers an area only 3 kilometers (1.9 miles) wide. Illumination is from the top.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
On Mars, Northern Hemisphere Summer (and Southern Hemisphere Winter) began on December 16, 2000. In this December holiday season, many children across the U.S. and elsewhere are perhaps anticipating an annual visit from a generous and jolly red-suited soul from the Earth's North Pole. As the December holidays were approaching, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) was busy acquiring new views of the region around the martian north pole. The three best views obtained this month are shown here. The top (A) and bottom (C) views show many layers exposed and eroded into the form of ridges and troughs on shallow slopes within the martian north polar cap. The middle (B) view is a picture of the rugged, eroded polar ice cap surface itself. The layers are believed to have formed over tens to hundreds of thousands of years by deposition of dust and ice each cold martian winter. These surfaces today all appear to have been eroded. The brightest material in each image is frost--temperatures at this time of year indicate that the frost is composed of frozen water. In winter, temperatures can be cold enough to freeze carbon dioxide, as well.
Voir l'image PIA02898: North Polar Ice Cap Surface sur le site de la NASA.
"White Rock" is a ridged mound that was first seen and informally named "White Rock" in pictures from the Mariner 9 orbiter in 1972. In black-and-white photos, the feature appears much brighter than its surrounding terrain, giving the impression that the material is white. Later analyses of Mariner 9, Viking, and Mars Global Surveyor (MGS) data showed that the feature isn't actually white, it is somewhat red and reflects only about 20-25% of the sunlight that falls upon it (a white surface would reflect 100%).
Located in Pollack Crater, a 95 km (59 mile) wide impact basin at 7.9°S, 334.7°W, White Rock is the light-red/orange feature with the rectangular white box drawn on it in the context view above. The white box indicates the location of a sub-frame of a MGS Mars Orbiter Camera (MOC) image acquired in September 2000, shown in PIA02848. The light-toned material that gives White Rock its name forms steep cliffs with valleys between them covered by dark, windblown, rippled sand. This release image shows a close-up of a portion of PIA02848, illustrating that the bright material is layered (arrow, "layers") and that there is an old impact crater (arrow, "crater") that has been partly uncovered from beneath the White Rock material.
The layering in White Rock suggests that the material is sediment deposited at some time in the distant past within Pollack Crater. The fact that the material erodes to form steep cliffs suggests that it is hard like rock. Thus, White Rock is interpreted to be an outcrop of sedimentary rock. It is probably a small remnant of a larger body of rock that may have once covered the entire floor of Pollack Crater; this view is supported by the observation that more extensive layered rocks are seen in other craters across the surface of the red planet (e.g., the crater at 8°N, 7°W).
Both pictures shown here are illuminated by sunlight from the upper left, north is up. Pollack Crater was named in 1997 for James B. Pollack (1938-1994), a NASA Ames Research Center scientist known in the Mars research community for his atmospheric research with Mariner 9 and Viking data and the development of key computer models used to investigate the red planet's winds, storms, and climate.
Voir l'image PIA02849: White Rock' of Pollack Crater sur le site de la NASA.
April 1999--It is summer now in the northern hemisphere of Mars, and the north polar ice cap has retreated considerably since it was last viewed in detail by the Mars Global Surveyor Mars Orbiter Camera in September 1998 (see 1998 Polar List). This new, high-resolution view shows the edge of the retreating polar cap as a bright, wind-streaked surface seen at the lower left. The ridges and tiny buttes and pits in the upper and right portions of the picture are part of the polar cap's layered deposits--stacks of dust and ice built up over the millennia. The picture covers an area 2.6 kilometers(1.6 miles) wide and is illuminated from the upper right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
This image is illuminated by sunlight from the upper left.
Some of the surface of the residual south polar cap has a pattern that resembles that of sliced, swiss cheese. Shown here at the very start of southern spring is a frost-covered surface in which there are two layers evident--a brighter upper layer into which are set swiss cheese-like holes, and a darker, lower layer that lies beneath the "swiss cheese" pattern. Nothing like this exists anywhere on Mars except within the south polar cap.
This is a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image acquired on August 2,1999. It is located near 84.8°S, 71.8°W, and covers an area 3 km across and about 6.1 km long (1.9 by 3.8 miles).
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02368: More South Polar "Swiss Cheese" sur le site de la NASA.
This image, acquired by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in May 2000 shows numerous examples of martian gullies that all start--or head--in a specific layer roughly a hundred meters beneath the surface of Mars. These features are located on the south-facing wall of a trough in the Gorgonum Chaos region, an area found to have many examples of gullies proposed to have formed by seepage and runoff of liquid water in recent martian times.
The layer from which the gullies emanate has recessed backward to form an overhang beneath a harder layer of rock. The larger gullies have formed an alcove--an area above the overhang from which debris has collapsed to leave a dark-toned scar. Below the layer of seepage is found a dark, narrow channel that runs down the slope to an apron of debris. The small, bright, parallel features at the base of the cliff at the center-right of the picture is a series of large windblown ripples.
Although the dark tone of the alcoves and channels in this image is not likely to be the result of wet ground (the contrast in this image has been enhanced), it does suggest that water has seeped out of the ground and moved down the slope quite recently. Sharp contrasts between dark and light areas are hard to maintain on Mars for very long periods of time because dust tends to coat surfaces and reduce brightness differences. To keep dust from settling on a surface, it has to have undergone some process of erosion (wind, landslides, water runoff) relatively recently. There is no way to know how recent this activity was, but educated guesses center between a few to tens of years, and it is entirely possible that the area shown in this image has water seeping out of the ground today.
Centered near 37.9°S, 170.2°W, sunlight illuminates the MOC image from the upper left, north is toward the upper right. The context view above is from the Viking 1 orbiter and was acquired in 1977. The Viking picture is illuminated from the upper right; north is up. The small white box in the context frame shows the location of the high resolution MOC view.
Voir l'image PIA01032: Evidence for Recent Liquid Water on Mars:"Weeping" Layer in Gorgonum Chaos sur le site de la NASA.
2 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.5 meters (~5 feet) per pixel view of an impact crater that is approximately 3 km (9840 ft) in diameter. It is located in southwestern Terra Sabaea. South (toward the bottom of the image) of the impact crater is a second, more subdued circular feature which is probably an ancient impact crater that was buried and only partially exhumed, a common occurrence on Mars.
Location near: 21.9°S, 338.6°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
The Olympica Fossae are a complex array of deep troughs, channels and streamlined landforms in northern Tharsis. Water, mud, and lava are all thought to have played a role in the formation of these features. MOC image obtained on March 20, 1999.
On July 20, 1969, the first human beings landed on the Moon. On July 20, 1976, the first robotic lander touched down on Mars. This July 20th-- 29 years after Apollo 11 and 22 years since the Viking 1 Mars landing-- we take a look forward toward one possible future exploration site on the red planet.
One of the advantages of the Mars Global Surveyor Mars Orbiter Camera (MOC) over its predecessors on the Viking and Mariner spacecraft is resolution. The ability to see-- resolve--fine details on the martian surface is key to planning future landing sites for robotic and, perhaps, human explorers that may one day visit the planet.
At present, NASA is studying potential landing sites for the Mars Surveyor landers, rovers, and sample return vehicles that are scheduled to be launched in 2001, 2003, and 2005. Among the types of sites being considered for these early 21st Century landings are those with "exobiologic potential"--that is, locations on Mars that are in some way related to the past presence of water.
For more than a decade, two of the prime candidates suggested by various Mars research scientists are Gusev Crater and Ma'adim Vallis. Located in the martian southern cratered highlands at 14.7° S, 184.5° W, Gusev Crater is a large, ancient, meteor impact basin that--after it formed--was breached by Ma'adim Vallis.
Viking Orbiter observations provided some evidence to suggest that a fluid--most likely, water--once flowed through Ma'adim Vallis and into Gusev Crater. Some scientists have suggested that there were many episodes of flow into Gusev Crater (as well as flow out of Gusev through its topographically-lower northwestern rim). Some have also indicated that there were times when Ma'adim Vallis, also, was full of water such that it formed a long, narrow lake.
The possibility that water flowed into Gusev Crater and formed a lake has led to the suggestion that the materials seen on the floor of this crater--smooth-surfaced deposits, buried craters, and huge mesas near the mouth of Ma'adim Vallis--are composed of sediment that eroded out of the highlands to the south of Gusev Crater. In 1995, the Exobiology Program Office at NASA Headquarters produced a report, An Exobiological Strategy for Mars Exploration (NASA SP-530), that included Gusev Crater as a possible priority site for future Mars exploration because it might once have been a lake.
At 12:17 a.m. (PDT) on April 24, 1998-- during Mars Global Surveyor's 259th orbit--MOC obtained the high resolution image of Gusev Crater and Ma'adim Vallis shown above, in part to test some of the proposed hypotheses. The raw image has a scale of 7.3 meters (24 feet) per pixel. At this scale, there are no obvious shorelines that would indicate the past presence of a lake in either Ma'adim Vallis or Gusev Crater. There are several alternative explanations for this absence, including:
It is possible that any lake in Gusev occurred so long ago that erosion by wind and hillslope processes have long since removed such features.
It is possible that 7.3 meters per pixel is insufficient to identify key diagnostic lake features.
It is possible that a lake once existed, but that shore- and near-shore processes as they occur in terrestrial lake environments did not occur on Mars.
It is possible no lake ever existed.
When Mars Global Surveyor achieves its Mapping Orbit in March 1999, MOC will have the ability to obtain pictures with resolutions around 1.5 meters (5 feet) per pixel. Sometime during the mapping mission, it may be possible to image Gusev Crater again to look for potential lake features and possible future landing sites.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01454: Moon/Mars Landing Commemorative Release: Gusev Crater and Ma'adim Vallis sur le site de la NASA.
This figure compares five representative views of the Mars Polar Lander primary ellipse near 76°S, 195°W, with a similar-sized view of the U.S. capital for scale. Each box is approximately 1.2 km (0.75 mi) on a side. The brightness variations from one box to another among the Mars images reflects different amounts of frost cover, and possibly the differing compositions of frost (i.e., carbon dioxide vs. water ice). The brightness also depends upon surface texture both above and below the scale of these images (about 5.5 meters--18 feet--per pixel). These pictures show the range of surface texture and morphology that is found within the landing ellipse. Mounds and valleys that range from a few meters to as much as one hundred meters (328 ft) across--with relief of a few meters--dominate the landing site. All of the frost seen here is expected to be gone by the time the Mars Polar Lander arrives in December 1999. The Mars images are illuminated from the lower right. The view of Washington D.C. shows the Capitol Building at the center right and the National Air and Space Museum at center left (immediately below the grassy rectangles of the Mall).
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Happy St. Valentine's Day from the Red Planet! The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) captured this unique view of a bright, heart-shaped mesa in the south polar region on November 26, 1999. This feature is located in the Promethei Rupes region near 79.6°S, 298.3°W. Sunlight illuminates the scene from the lower left. The heart is about 255 meters (279 yards) across. The presence of this mesa indicates that the darker, rough terrain that surrounds it was once covered by a layer of the bright material.
Earlier in 1999, MGS MOC saw another valentine heart, but instead of a mesa, the feature was expressed as a pit. You can view that image by CLICKING HERE.
Image shows a fluid-scoured surface in the Hrad Vallis system, located northwest of Elysium Mons. The fluid is presumed to have been water. Image obtained by MOC on July 20, 1998.
Steep-walled valleys with lineations--ridges and grooves--on their floors are common in the fretted terrain. The material comprising these valley floors is called lineated valley fill. In some of the best images taken by the Viking Orbiters in the late 1970s, some of the valley fill appeared to resemble alpine glaciers like those seen on Earth. Given this superficial similarity, some scientists assumed that the lineations on these valley floors might have formed by flow of ice in (and perhaps through) these canyons and valleys.
The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) took a variety of pictures of the martian fretted terrain, particularly during the months of April through September of 1998. MOC image 46704 (above) was taken on August 2, 1998. It shows a very high resolution view of lineated valley fill on the floors of some straight, narrow canyons named the Coloe Fossae. The image reveals that the canyon walls are very smooth and generally featureless. The canyon floors display a complex set of ridges and grooves that are generally parallel to the cliffs, but in some places these are partly buried by a smooth-surfaced material. The general impression is that the ridges and grooves on the valley floors represent material that has been shed from the smooth canyon walls and was subsequently modified by wind. It is not clear whether any of this material is moving or flowing as it would in an ice-rich deposit (e.g., a glacier).
The picture shown is a subframe of MOC image 46703. The scene is 5.5 km by 21.5 km (3.4 miles by 13.4 miles). The image as presented here has a resolution of about 13.2 meters (43 feet) per pixel. The subframe is centered at 34.4°N latitude and 302.0°W longitude. (CLICK HERE for a context image). North is approximately up, illumination is from the right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01502: Mars Fretted Terrain: Lineated Valley Fill sur le site de la NASA.
6 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an old impact crater in southeastern Arabia Terra. The crater ejecta blanket is no longer visible and all of the terrain has been covered by a mantle of dust. The dark streaks on the crater wall are the result of dry avalanches of dust; the darker streaks formed more recently than the lighter-toned streaks. Indeed, the darkest streak is likely to be less than a few years old.
Location near: 3.0°N, 315.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
2 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows polygonally patterned ground on the floor of a trough in the southern hemisphere of Mars. The polygons could be an indicator that ground ice is or was present at this location. The dark streaks were formed by passing dust devils.
Location near: 67.4°S, 240.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
18 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of the south polar residual cap. The darkened edges of the pits and mesas are evidence of the removal - by sublimation -- of frozen carbon dioxide during the recent martian summer. Summer ended and autumn began the day this image was acquired in January 2006.
Location near: 86.8°S, 90.5°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer/Autumn
16 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of the south polar residual cap where the effects of sublimation are apparent. Over extended periods of time, sublimation "eats" away at the smoother appearing material (largely composed of frozen carbon dioxide), darkening the scarps and creating the irregularly shaped depressions that are present throughout much of the scene.
Location near: 87.1°S, 69.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
17 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a surface in Isidis Planitia, littered with degraded impact craters. Windblown ripples of various sizes and shapes are prevalent throughout the scene as well, producing wave-like patterns on the floors of some of the larger impact craters.
Location near: 16.8°N, 266.4°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
The two pictures above show examples of the north and south polar residual caps as they appeared in summer. The pictures are small because they have been extracted from the daily global maps taken by the Red Wide Angle Camera of the Mars Orbiter Camera (MOC) system onboard the Mars Global Surveyor (MGS) orbiter. On every orbit, a tiny picture showing a portion of Mars at a resolution of 7.5 kilometers (4.7 miles) per pixel is obtained so that the changing martian weather--and changing polar caps--can be monitored.
The latest northern hemisphere summer season ended the first of August 1999. Thus, the picture shown above (left) presents what the north polar residual cap looked like during the most recent summer. As for southern summer, it began around December 25, 1999, and continues today. The picture shown here (above, right) indicates what the south polar residual cap looked like near the end of February 2000.
These two images have been used as planning tools by the MOC team at MSSS. The "pinwheel" pattern in the south polar picture is being shown on purpose. The pattern results from the fact that the south polar picture is a mosaic of more than 12 global images acquired by MOC on February 25 and 26, 2000. Mosaics such as this are used every week by the team for targeting purposes (to see which areas are covered by frost). This particular mosaic was used for planning MOC high resolution views during the first few days of March 2000. The north polar image does not show seams because this picture was extracted from a single daily global image that was map-projected and used by the MOC team and used for weather monitoring.
To see an example of the MGS MOC "daily global map"--one acquired in April 1999--see:"Mars Global Weather Monitoring," July 19, 1999.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02366: What is a "Residual" Polar Cap? sur le site de la NASA.
The martian polar layered deposits exhibit features common to sedimentary rocks on Earth. The image on the left shows an angular unconformity, with horizontal layers overlying tilted beds. The image on the right shows deformed layers. Both pictures were taken on MGS's 445th orbit about the planet in July 1998.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01505: Corasis Fossae Valley sur le site de la NASA.
Figure caption from Science Magazine
Voir l'image PIA00808: Ridges in Mars' south polar region sur le site de la NASA.
The above figure shows the location of all high resolution (narrow angle) MOC images of the Cydonia region that have been obtained to date, including the first three taken in 1998 (PIA01240, PIA01241, AND PIA01440). These images are superimposed upon a mosaic of Viking images taken during the 1970's. Images acquired during the Science Phasing Orbit period of 1998 slant from bottom left to top right; Mapping Phase images (from 1999 and 2000) slant from lower right to upper left. Owing to the nature of the orbit, and in particular to the limitations on controlling the location of the orbit, the longitudinal distribution of images (left/right in the images above) is distinctly non-uniform. An attempt to take a picture of a portion of the "Face" itself in mid-February 2000 was foiled when the MGS spacecraft experienced a sequencing error and most of that day's data were not returned to Earth. Only the first 97 lines were received; the image's planned footprint is shown as a dashed box. This image is one in a series of eight.
Voir l'image PIA02382: Cydonia: Two Years Later sur le site de la NASA.
July 1999--Spring is rapidly approaching for the martian southern hemisphere. Over the past month, much of the high southern latitudes of Mars have emerged from nearly 5 months of wintertime darkness, revealing a bright, frost-covered surface that presently extends from about 57°S to the south pole. Frosts at this time of year can consist of both frozen carbon dioxide ("dry ice") and frozen water. The above images are interpreted to show surfaces covered by water frost, because the temperature of the surface at the time the images were acquired was about -184°F or -120°C (visit the Thermal Emission Spectrometer to see an example of their data). This temperature is above the freezing point of carbon dioxide (around -200°F = -130°C).
The pair of Mars Global Surveyor Mars Orbiter Camera (MOC) images presented here show a snow-covered surface located on Malea Planum, south of the giant Hellas impact basin. These pictures were taken simultaneously on July 18, 1999. The first image (left) is a MOC red camera wide angle context view showing the location of the higher-resolution narrow angle camera view (right). The white box in the context image indicates the location of the high-resolution view. Small black dots in the narrow angle image (right) are boulders and other surfaces from which the snow has been defrosted. The large crater in the wide angle (left) image is about 36 km (22 mi.) across. The narrow angle (right) image covers an area 3 km (1.9 mi)wide at a resolution of 3 meters (10 feet) per pixel. Illumination in each image is from the upper left.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02095: Winter Frosts of the Retreating South Polar Cap sur le site de la NASA.
The small volcano is located in the Tempe-Mareotis Fossae region of Tempe Terra (local context Viking 1 Orbiter image 627a28). Centered at 36.2°N, 85.1°W, this is one of many small volcanoes on Mars. The Mars Global Surveyor MOC image presented here is the first close-up view of one of these small volcanoes.
This volcano is similar in both shape and size to many of the small basalt shield volcanoes found on the Snake River Plain in southern Idaho, U.S.A. Other similar volcanic vents are found in Hawaii and Iceland. Basalt is the dark, iron- and magnesium-rich silicate rock found in places like the Snake River Plain, Hawaii, and Iceland. Basalt is also common on the floor of Earth's oceans and on the flat plains of the Moon known as maria.
The volcano seen in this MOC image does not show many of the features generally found around volcanoes of this size on Earth. Instead of the lava flows and leveed channels found on Earth, we see only a faint pattern of subtle, somewhat sinuous ridges and troughs that are radial to the long, elliptical summit depression (or caldera). This pattern gives the surface of the volcano and its surroundings quite a rough appearance. Much of the appearance of this "sandpaper-like" texture appears to be unrelated to the volcano, but is instead an expression of the eroded regolith--"soil"--that covers the old lava flows. The MOC image suggests that a person hiking around on this small martian volcano would find the walk pretty difficult (especially in a spacesuit).
But what an exciting and fascinating walk that would be. Not only would one be able to look, and even hike down, into the 150 m (460 foot) deep caldera, but one could also inspect the spectacular, regularly-spaced ridges seen on the floors of nearby troughs (e.g., in the lower 1/3 of this MOC image). These ridges are formed by wind and are probably composed of a mixture of sand and granules--perhaps reworked cinders from ancient volcanic eruptions in the region. Some windblown ridges can also be seen in the shadows on the floor of the volcano's linear caldera.
The MOC image was taken at 6:57 a.m. (PDT) on August 22, 1998, during the 506th orbit of Mars Global Surveyor as the spacecraft was nearing its 507th periapsis (closest point to the planet during the orbit). The local time (on Mars) was late in the afternoon--the Sun was only 10° above the horizon--equivalent to about 5:20 p.m.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01468: Small Volcano in Tempe Terra sur le site de la NASA.
The above figure shows the location of all high resolution (narrow angle) MOC images of the Cydonia region that have been obtained to date, including the first three taken in 1998 (PIA01240, PIA01241, AND PIA01440). These images are superimposed upon a mosaic of Viking images taken during the 1970's. Images acquired during the Science Phasing Orbit period of 1998 slant from bottom left to top right; Mapping Phase images (from 1999 and 2000) slant from lower right to upper left. Owing to the nature of the orbit, and in particular to the limitations on controlling the location of the orbit, the longitudinal distribution of images (left/right in the images above) is distinctly non-uniform. An attempt to take a picture of a portion of the "Face" itself in mid-February 2000 was foiled when the MGS spacecraft experienced a sequencing error and most of that day's data were not returned to Earth. Only the first 97 lines were received; the image's planned footprint is shown as a dashed box. This image is one in a series of eight.
Voir l'image PIA02385: Cydonia: Two Years Later sur le site de la NASA.
The unnamed crater is one of three closely adjacent impact features that display the ejecta pattern characteristic of one type of "flow-ejecta" crater. Such patterns are considered evidence of fluidized movement of the materials ejected during the cratering event, and are believed to indicate the presence of subsurface ice or liquid water.
Long, linear features of different brightness values can be seen on the on the steep slopes inside and outside the crater rim. This type of feature, first identified in Viking Orbiter images acquired over 20 years ago, are more clearly seen in this new view (about 3 times better than the best previous observations). Their most likely explanation is that small land or dirt slides, initiated by seismic or wind action, have flowed down the steep slopes. Initially dark because of the nature of the surface disturbance, these features get lighter with time as the ubiquitous fine, bright dust settles onto them from the martian atmosphere. Based on estimates of the dust fall-out rate, many of these features are probably only a few tens to hundreds of years old. Thus, they are evidence of a process that is active on Mars today.
Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01156: Flow Ejecta and Slope Landslides in Small Crater - High Resolution Image sur le site de la NASA.
Mars Orbiter Camera (MOC) narrow angle images provide high resolution views of the Martian surface that rival the quality of aerial photographs used to study the geology of Earth. Over the past year and a half, MOC images have helped to highlight the fact that much of the almost Moon-like heavily cratered terrains of Mars consist of layered materials.
Eastern Arabia Terra is a region that was known from the Viking orbiter missions(1976-1980) to show vast tracts of eroded terrain. The image on the left, above, shows a regional view from Viking. Eastern Arabia is distinct for its rough-textured cratered terrain, and for the presence of the ancient, perhaps water-carved valley, Auqakuh Vallis. The center image (above) includes a high-resolution view from the Viking 1 orbiter, with a more recent image from the Mars Global Surveyor (MGS) MOC shown as an inset.
The third image (above, right) is a MOC high resolution view that shows a portion of the ancient Auqakuh Vallis (just above center) and many eroded remnants of the ancient cratered terrain. The MOC image reveals dunes on the floor of Auqakuh Vallis, and shows a plethora of small, straight and curved ridges running across the terrain. The geological term for these ridges is "dike." Dikes most commonly form on Earth in volcanic terrain, when molten rock (magma) is injected into a crack in the subsurface. The magma cools, hardens, and later erosion removes the surrounding rock to leave behind the more resistant volcanic rock as a ridge. Shiprock in the northwest corner of New Mexico, U.S.A., is an example of a place on Earth where dike ridges are found. This MOC image is one of many that are being examined by the MOC Science Team in order to decipher the ancient geological history of the red planet.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02043: Eroded, Layered Cratered Highlands of Eastern Arabia Terra sur le site de la NASA.
The Mars Orbiter Camera (MOC) onboard the Mars Global Surveyor (MGS) orbiter, was designed specifically to bridge the gap between what can be seen from orbit in typical Mariner 9 and Viking orbiter images, and what can be seen from the ground by landers such as Viking 1 and Mars Pathfinder. The camera, therefore, takes pictures of extremely high resolution. These images are often comparable to aerial photographs used by geologists when they are exploring Earth. The highest resolution images that can be obtained are in the range of 1.4 to 2.0 meters (4.6 to 6.5 feet) per pixel.
Last year, several pictures of a portion of the Cydonia region of Mars were photographed at lower resolution than is now possible in the Mapping Phase of the MGS mission. The Cydonia region is perhaps most "famous" for being the location of a feature that--in Viking Orbiter images--seemed to resemble a human face. Nearby buttes and hills were considered by some to represent a "city."
The MGS spacecraft flew over the "famous" Cydonia landforms again--for the first time since April 1998--on June 27, 1999, at 10:53 UTC (Greenwich Time Zone). The new MOC images shown here provide the highest resolution view yet obtained of the "Cydonia city" landforms.
The picture at the above left (MOC2-142a) shows the regional context. Cydonia constitutes a transition zone between the cratered highlands of Arabia Terra, and the less-cratered lowlands of Acidalia Planitia. This transition zone contains thousands of mesas and buttes--somewhat like the Monument Valley region along the Arizona/Utah border in North America. The white box shows the location of the new high resolution view of the "city" landforms. The image is a red wide angle context frame obtained by MOC at the same time that the high resolution view was acquired. The picture is illuminated from the lower left, and north is toward the upper right.
The picture in the center is a processed version of the new MOC narrow angle camera image of this portion of Cydonia. You can view the full-size image
Like the context image (above left), the high resolution view (center) is illuminated from the lower left. North is toward the upper right. Boulders can be seen on some of the hill slopes, and the plains between the hills are rough and pitted. To conserve data in order to account for downtrack position uncertainties, only 1/2 of the MOC sensor was used to acquire this picture (allowing the image to be twice the length): it covers an area that is 1.5 km (0.9 mi) wide.
The picture at the above right is the unprocessed MOC image. This what the processed image (center) looked like before it was rotated 180° (so that north is toward the top) and corrected for a 1.5 aspect ratio. The pixel size in the unprocessed image is different in the cross-track (left-right) and down-track (top-bottom) directions, thus making the craters look "squished." The cross-track scale is about 1.5 meters (5 feet) per pixel, while the down-track scale is about 2.25 meters (7.4 feet) per pixel. In the unprocessed image, the illumination is coming from the upper right. You can view this image at full-size (use "Save this link as..." and examine (MOC2-142c 100% Size) or see it via your web-browser at half-size (MOC2-142c 50% Size).
For a look at the Cydonia images previously obtained by MGS MOC in 1998, CLICKHERE.
For a pre-MGS discussion of Viking orbiter images of the "Face on Mars," CLICKHERE.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02092: New Cydonia Picture sur le site de la NASA.
Dark streaks on the steep, down-wind slopes of sand dunes in Rabe Crater are seen at several locations in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image. These streaks indicate relatively recent (i.e., in the past few years or less) movement of sand down these slopes.
Sand dunes move forward by the combined action of wind that drives sand up the shallow slope on the windward side of the dune (in this case, the slopes that face toward the lower right) and the avalanching of this sand down the steeper, lee-side slope. The steep slope is also known as the slip face. The dark streaks indicated by arrows are evidence for sand avalanches that occurred within a few months or years of the time when the picture was taken in March 1999. Other streaks which are seen criss-crossing the dunes may be the result of passing dust devils. This image is illuminated from the upper left and located in Rabe Crater of the Hellespontus-Noachis region near 44.2°S, 325.6°W.
Voir l'image PIA02354: Recent Sand Avalanching on Rabe Crater Dunes sur le site de la NASA.
Other information available for this image is the following: Orbit: 258 Range: 409.53 km Resolution: 3.46 m/pixel Image dimensions: 1024 X 9600 pixels, 3.5 km x 33.2 km Line time: 0.50 msec Emission angle: 29.90 degrees Incidence angle: 69.59 degrees Phase angle: 60.62 degrees Scan rate: ~0.15 degree/sec Start time: periapsis + 410 sec Sequence submitted to JPL: Wed 04/22/98 21:45:00 PDT Image acquired by MOC: Thu 04/23/98 12:23:02 PDT Data retrieved from JPL: Fri 04/24/98 09:00 PDT
Voir l'image PIA01241: Cydonia Region - Pass #3 sur le site de la NASA.
8 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an area adjacent to the south polar residual cap that hosts several intricate fracture networks. Each network consists of multiple fractures radiating from a central location. Their origin is not understood -- some investigators have speculated that these are sites of release of carbon dioxide from beneath the ground, but this explanation seems inadequate to explain all attributes of the features. MOC images have shown that these features have not been changing from year to year during the course of the MGS mission.
Location near: 87.1°S, 234.1°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01158: Schiaparelli Crater Rim and Interior Deposits - High Resolution Image sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows several small, dark sand dunes and a small crater (about 1 kilometer in diameter) within a much larger crater (not visible in this image). The floor of the larger crater is rough and has been eroded with time. The floor of the smaller crater contains windblown ripples. The steep faces of the dunes point to the east (right), indicating that the dominant winds blew from the west (left). This scene is located near 38.5°S, 347.1°W, and covers an area approximately 3 km (1.9 mi) wide. Sunlight illuminates the landscape from the upper left. This southern autumn image was acquired on 1 July 2006.
When a meteor impacts a planetary surface, it creates a blast very much like a bomb explosion. Shown here are two excellent examples of small impact craters on the martian surface. Each has a dark-toned deposit of material that was blown out of the crater (that is, ejected) during the impact. Materials comprising these deposits are called ejecta. The ejecta here is darker than the surrounding substrate because each crater-forming blast broke through the upper, brighter surface material and penetrated to a layer of darker material beneath. This darker material was then blown out onto the surface in the radial pattern seen here.
The fact that impact craters can penetrate and expose material from beneath the upper surface of a planet is very useful for geologists trying to determine the nature and composition of the martian subsurface. The scene shown here is illuminated from the upper left and covers an area 1.1 km (0.7 mi) wide by 1.4 km (0.9 mi). The larger crater has a diameter of about 89 meters (97 yards), the smaller crater is about 36 meters (39 yards) across. The picture is located in Terra Meridiani and was taken by the Mars Global Surveyor Mars Orbiter Camera.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01683: Small Impact Craters with Dark Ejecta Deposits sur le site de la NASA.
This pair of Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images shows a variety of geologic features along the eastern edge of the Gigas Sulci (the rough, ridged surface at upper left in each picture) in western Tharsis. This is a volcanic region located approximately 750 km (470 mi) northwest of the Pavonis Mons volcano and 350 km (220 mi) southeast of the Olympus Mons volcano.
The regional view (above, left) is a MOC wide angle context image showing the location of the higher resolution, narrow angle camera view (above, right) as a small, white box. The upper left portion of the context image shows a rough, hilly terrain--Gigas Sulci--that is cut along its margins by several troughs that look something like gashes made by a giant knife. Also in this scene are several impact craters, including one (upper right) with a bright, teardrop-shaped "tail" formed by wind. The context frame covers an area approximately 115 kilometers (71 miles) across and is illuminated from the left. North is up.
The high resolution picture (above, right) is a MOC narrow angle camera view of a 3 km-(1.9 mi)-wide area along the edge of the hilly, Gigas Sulci terrain. This image shows a range of interesting geologic features. The Gigas Sulci consist of steep, somewhat mountainous terrain, but the valleys and some of the slopes between these hills appear smooth and mantled (perhaps by dust). Small, parallel ridges on some of the valley floors are probably windblown dunes. The edge of the hilly terrain is cut by a deep trough caused by faulting and down-dropping of the terrain in the center of the valley. The slopes of this valley exhibit dark streaks caused by small landslides. Boulders the size of small buildings can also be seen on some of these slopes. This deep trough and another, shallower one to the south (lower left) cut across lava flows, indicating that the troughs formed after the lava flows were emplaced, cooled, and hardened. The trough at the lower left has slumped and terraced walls. As in the context frame, nor this up and the sun illuminates the scene from the left.
For a full-resolution (3.7 meters--12 feet--per pixel) view of the narrow angle camera image (2.9 Mbytes), Click HERE.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Figure caption from Science Magazine
Voir l'image PIA00801: Medusae Fossae #2 sur le site de la NASA.
10 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a crater that is approximately 2 km in diameter in south central Syrtis Major Planum. The image also captures a portion of the light-toned wind streak formed in the lee (to the left) of the crater. The wind streak is likely composed of a thin coating of dust.
Location near: 1.9°N, 294.0°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Northern Summer
Some of the pictures returned from Mars by the Mars Orbiter Camera (MOC) onboard the Mars Global Surveyor (MGS) spacecraft show features that--at a glance--resemble familiar, non-geological objects on Earth. For example, the picture above at the left shows several low, relatively flat-topped hills (mesas) on the floor of a broad valley among the mountains of the Nereidum Montes region, northeast of Argyre Planitia. One of the mesas seen here looks like half of a butterfly (upper subframe on right). Another hill looks something like a snail or a hot dog wrapped and baked in a croissant roll (lower subframe on right). These mesas were formed by natural processes and are most likely the eroded remnants of a formerly more extensive layer of bedrock. In the frame on the left, illumination is from the upper left and the scene covers an area 2.7 km (1.7 miles) wide by 6.8 km (4.2 miles) high. The "butterfly" is about 800 meters (875 yards) in length and the "hot dog" is about 1 km (0.62 miles) long.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01684: Hot Dog and Butterfly, Nereidum Montes sur le site de la NASA.
Figure caption from Science Magazine
Voir l'image PIA00806: Tithonium Chasma/Ius Chasma sur le site de la NASA.
10 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a variety of textures observed on a south middle-latitude plain east-southeast of Hellas Planitia. Dark streaks left by passing dust devils are practically ubiquitous across the scene, including the transition from the texturally-smooth area (the majority of the image) onto the circular, rough feature near the right (east) edge of the image. The circular feature might once have been the site of an impact crater; perhaps this is the remains of its floor, and the rest of the crater and the rock in which it formed was removed by erosion.
Location near: 4.0°S, 348.0°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Autumn
The Olympica Fossae are a collection of troughs and depressions located in northern Tharsis, south of the Alba Patera volcano. The Mars Global Surveyor Mars Orbiter Camera has been sending back unprecedented, spectacular views of this region. The Olympica Fossae are especially interesting because they show landforms that run the entire range of things seen elsewhere on Mars. This picture shows many examples, including layered outcrops in canyon walls, evenly-spaced dunes on the canyon floors, dark landslide streaks on the canyon walls, pits formed by ground collapse, and streamlined forms related to the flow of water, mud, or lava.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
On Mars, Northern Hemisphere Summer (and Southern Hemisphere Winter) began on December 16, 2000. In this December holiday season, many children across the U.S. and elsewhere are perhaps anticipating an annual visit from a generous and jolly red-suited soul from the Earth's North Pole. As the December holidays were approaching, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) was busy acquiring new views of the region around the martian north pole. The three best views obtained this month are shown here. The top (A) and bottom (C) views show many layers exposed and eroded into the form of ridges and troughs on shallow slopes within the martian north polar cap. The middle (B) view is a picture of the rugged, eroded polar ice cap surface itself. The layers are believed to have formed over tens to hundreds of thousands of years by deposition of dust and ice each cold martian winter. These surfaces today all appear to have been eroded. The brightest material in each image is frost--temperatures at this time of year indicate that the frost is composed of frozen water. In winter, temperatures can be cold enough to freeze carbon dioxide, as well.
Voir l'image PIA02899: Complex exposures of North Polar layered material sur le site de la NASA.
"White Rock" is a ridged mound that was first seen and informally named "White Rock" in pictures from the Mariner 9 orbiter in 1972. In black-and-white photos, the feature appears much brighter than its surrounding terrain, giving the impression that the material is white. Later analyses of Mariner 9, Viking, and Mars Global Surveyor (MGS) data showed that the feature isn't actually white, it is somewhat red and reflects only about 20-25% of the sunlight that falls upon it (a white surface would reflect 100%).
Located in Pollack Crater, a 95 km (59 mile) wide impact basin at 7.9°S, 334.7°W, White Rock is the light-red/orange feature with the rectangular white box drawn on it in the context view above. The white box indicates the location of a sub-frame of a MGS Mars Orbiter Camera (MOC) image acquired in September 2000, shown in the release image. The light-toned material that gives White Rock its name forms steep cliffs with valleys between them covered by dark, windblown, rippled sand. PIA02849 shows a close-up of a portion of this release, illustrating that the bright material is layered (arrow, "layers") and that there is an old impact crater (arrow, "crater") that has been partly uncovered from beneath the White Rock material.
The layering in White Rock suggests that the material is sediment deposited at some time in the distant past within Pollack Crater. The fact that the material erodes to form steep cliffs suggests that it is hard like rock. Thus, White Rock is interpreted to be an outcrop of sedimentary rock. It is probably a small remnant of a larger body of rock that may have once covered the entire floor of Pollack Crater; this view is supported by the observation that more extensive layered rocks are seen in other craters across the surface of the red planet (e.g., the crater at 8°N, 7°W).
Both pictures shown here are illuminated by sunlight from the upper left, north is up. Pollack Crater was named in 1997 for James B. Pollack (1938-1994), a NASA Ames Research Center scientist known in the Mars research community for his atmospheric research with Mariner 9 and Viking data and the development of key computer models used to investigate the red planet's winds, storms, and climate.
Voir l'image PIA02848: White Rock' of Pollack Crater sur le site de la NASA.
Among the geological features examined by MOC in recent weeks--the enigmatic "Giant Polygons" on the martian northern plains. In the 1970s the Viking Orbiters saw huge cracks , some more than 1 kilometer (0.62 miles) wide, arranged in a polygonal pattern that outlined flat-lying areas sometimes 5 to 20 kilometers (3 to 12 miles) across. Giant polygons are most common in parts of Utopia Planitia and Acidalia Planitia, but there is also a cluster of them in the lowlands west of the Elysium volcanoes, on Elysium Planitia.
The exact origin of the giant polygons has never been determined. At first glance, they appear to resemble mud cracks that one might see on the surface of a dried-up puddle, pond, or lake. However, mud cracks and the polygonal patterns they create are small features--like the size of a human hand. The giant polygons on Mars are big enough to hold the entire downtown area of a moderate-sized city.
Mud cracks form by dessication--i.e., the removal of water by evaporation (drying). Many ideas about the polygons on Mars have centered on the idea that they are somehow related to the dessication of thick layers of wet sediment--perhaps deposited by some of the giant floods that Mars is known to have had. However, there has been considerable debate about whether the polygons formed in lava instead of sediment. Cooling lava might also crack and give the polygon texture, some have argued. Two observations have been made--using Viking images--that constrain the types of origins that can be proposed: (1) most of the "cracks" appear to be graben--down-dropped blocks caused by faulting, and (2) some of the "cracks" appear to indicate the outlines of buried craters. These observations suggest that whatever caused the polygons, the process appears to be confined to material that has buried older terrain.
The new MOC image confirms the impression--from Viking images--that the polygon cracks--troughs--are graben formed by faults. Unfortunately, the image does not provide ample information to distinguish between the various models for the origin of the polygons or the material in which they occur. The images, however, do show features of interest. The floors of the polygon troughs, highlighted in these sub-areas of the MOC image (locations on MOC image) have bright, almost evenly spaced, windblown ripples or drifts(see also detailed sub-areas). Similar drifts can also be seen in and encroaching upon the surrounding, small impact craters. These drifts attest to the movement of sediment on the surface, and their brightness and shape suggests that they have not been active recently.
MOC image 52706 was taken at about 11:36 p.m. (PDT) on August 31, 1998, during the 526th orbit of Mars Global Surveyor as the spacecraft was nearing its 527th periapsis (closest point to the planet during the orbit).
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01470: Giant "Polygon" Troughs, Elysium Planitia at Full Resolution sur le site de la NASA.
13 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an impact crater in western Chryse Planitia that is approximately 850 meters (~2790 ft) in diameter, surrounded by a flat plain riddled by hundreds of smaller impact craters.
Location near: 27.6°N, 47.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
Figure caption from Science Magazine
Voir l'image PIA00810: Textures in south polar ice cap #2 sur le site de la NASA.
MOC "sees" by the dawn's early light! This picture was taken over the high southern polar latitudes during the first week of May 1999. The area shown is currently in southern winter darkness. Because sunlight is scattered over the horizon by aerosols--dust and ice particles--suspended in the atmosphere, sufficient light reaches regions within a few degrees of the terminator (the line dividing night and day) to be visible to the Mars Global Surveyor Mars Orbiter Camera (MOC) when the maximum exposure settings are used.
This picture shows a polygonally-patterned surface on southern Malea Planum. At the time the picture was taken, the sun was more than 4.5° below the northern horizon. The scene covers an area 3 kilometers (1.9 miles) wide, with the illumination from the top of the picture.
In this frame, the surface appears a relatively uniform gray. At the time the picture was acquired, the surface was covered with south polar wintertime frost. The highly reflective frost, in fact, may have contributed to the increased visibility of this surface.
This "twilight imaging" technique for viewing Mars can only work near the terminator; thus in early May only regions between about 67°S and 74°S were visible in twilight images in the southern hemisphere, and a similar narrow latitude range could be imaged in the northern hemisphere. MOC cannot "see" in the total darkness of full-borne night.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
15 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows two suites of gullies within a single impact crater in the Terra Cimmeria region. The gullies near the top of the image are located on the northern wall of the crater, while the lower suite resides on a lower bench in the crater's northern wall complex. Gully erosion has cut into the layered rock exposed on the crater wall. Water may have been involved in their formation.
Location near: 38.2°S, 190.6°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
These two buttes in the Elysium Basin exhibit many small dark streaks on their slopes. Each streak is the result of mass-movement (landslides). Darker streaks appear to be younger than the brighter ones. Image from MOC taken in April 1998.
On December 3, 1999, the Mars Polar Lander will touch down on the upper surface of a thick accumulation of layered material known as the "South Polar Layered Deposits." The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has been providing stunning new pictures of the south polar layered deposits that, in conjunction with Mars Polar Lander observations, will eventually help answer many questions about this terrain.
Both the north and south polar regions are blanketed by thick accumulations of layered material. This has been known since the 1971-1972 mission of Mariner 9. Based upon data from the Mariner and Viking projects in the 1970s, the polar layered deposits have long been considered to be accumulations of dust and ice. The layering is thought to indicate changes in how ice and dust accumulate at the poles over the course of millenia. Changes in climate might affect the thickness and composition of polar layers in a way that is analogous to how years of drought and years of plentiful rain change the width of rings in a tree trunk on Earth.
The pictures shown here provide new details of what the south polar layered deposits look like at extremely high resolution from the MGS MOC. The picture on the left is a context frame taken at the same time as the high resolution view on the right. The context image covers an area about 115 km (71 mi) across and shows a thick, smooth blanket of material covering the upper 2/3 of the frame. This thick blanket is the south polar layered deposit material. The circular features at the lower left in the context image are craters occurring outside the polar layered deposit. More craters occur underneath the polar layered deposits. The small white box indicates the location of the MOC high resolution image (right) along the edge of the polar layered deposits. The picture is illuminated from the lower right.
The picture on the right shows one of the clearest and highest-resolution images of south polar layered material ever obtained. Located at 73.0°S, 224.5°W, this picture covers an area approximately 550 km (340 miles) northwest of where the Mars Polar Lander will touch down in December. Illuminated from the lower right, this scene covers an area 1.5 km (0.9 mi) wide and 4.6 km (1.9 mi) long. The smallest objects that can be seen are about the sizes of automobiles. Small dark streaks in the upper right are formed from winds that have blown small patches of sediment across the surface of the layered material. Layers of only a few meters thickness are exposed along the edge of the polar layered deposits. The amount of dust versus ice in these layers is unknown. It is hoped that the Mars Polar Lander will be able to help determine--at least for the upper layers of the deposit--how much ice is present.
Voir l'image PIA02345: Layers of the South Polar Layered Deposits sur le site de la NASA.
Relief model of the topography of the South Polar Region showing the form of the ice cap and its surroundings. The circular area at the pole has not yet been mapped.
11 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows cracked surfaces in the south polar layered terrain of Mars. The cracks in this scene have formed complex dendritic arrays. Evidence of the fracture networks is clear in the topmost layer, however, close inspection reveals traces of apparently older networks in the underlying layers.
Location near: 79.1°S, 194.2°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
24 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark dunes superposed on the rippled floor of Proctor Crater in Noachis Terra. Winds blowing predominantly from east (right) to west (left) were responsible for the formation of these dunes.
Location near: 47.3°S, 329.4°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
Autumn in the martian northern hemisphere began around August 1, 1999. Almost as soon as northern fall began, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) started documenting the arrival of autumn frost--a precursor to the cold winter that will arrive in late December 1999. The first features to become covered by frost were the sand dunes that surround the north polar ice cap. The dunes seen here would normally appear very dark--almost black--except when covered by frost. Why the dunes begin to frost sooner than the surrounding surfaces is a mystery: perhaps the dunes contain water vapor that emerges from the sand during the day and condenses again at night. This picture shows dunes near 74.7°N, 61.4°W at a resolution of about 7.3 meters (24 feet) per pixel. The area covered is about 3 km (1.9 mi) across and is illuminated from the upper right. The picture appears to be somewhat fuzzy and grainy because the dunes here are seen through the thin haze of the gathering north polar winter hood (i.e., clouds).
Voir l'image PIA02339: Autumn Frost, North Polar Sand Dunes sur le site de la NASA.
Shown above are three pictures:
(A) is excepted from the U.S. Geological Survey's Mars Digital Image Mosaic, showing the Labyrinthus Noctis area west of the Valles Marineris. This image is about 175 km (109 miles) square. The outline of the MOC high resolution (Narrow Angle) camera image is centered at 4.6°S, 102.6°W.
(B) is the MOC frame P005_03. Because the MOC acquires its images one line at a time, the cant angle towards the sun-lit portion of the planet, the spacecraft orbital velocity, and the spacecraft rotational velocity combined to distort the image slightly.
(C) shows P005_03 skewed and rotated to the perspective that MOC was viewing at the time the image was taken.
Labyrinthus Noctis is near the crest of a large (many thousands of kilometers) upcoming of the Martian crust, and the 2000 meter (6500 foot) deep canyons visible in these pictures are bounded by faults. Debris shed from the steep slopes has moved down into after the canyons opened. Small dunes are seen in the lowest area, beneath the high cliffs.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The spacecraft has been using atmospheric drag to reduce the size of its orbit for the past three weeks, and will achieve a circular orbit only 400 km (248 mi) above the surface early next year. Mapping operations begin in March 1998. At that time, MOC narrow angle images will be 5-10 times higher resolution than these pictures.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA00941: MGS Views of Labyrinthus Noctis sur le site de la NASA.
The martian north and south polar regions are covered by large areas of layered deposits. Since their discovery in the early 1970's, these polar layered deposits have been cited as the best evidence that the martian climate experiences cyclic changes over time. It was proposed that detailed investigation of the polar layers (e.g., by landers and/or human beings) would reveal a climate record of Mars in much the same way that ice cores from Antarctica are used to study past climates on Earth. On January 3, 1999, NASA's Mars Polar Lander and Deep Space 2 Penetrators will launch on a journey to study the upper layers of these deposits in the martian southern hemisphere.
Meanwhile, investigation of the north polar layered deposits has advanced significantly this year with the acquisition of MGS data. The Mars Orbiter Laser Altimeter acquired new topographic profiles over the north polar deposits in June and early July, 1998, and dozens of new high resolution images were taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) from mid-July to mid-September, 1998. When it was proposed to NASA in 1985, one of the original objectives of MOC was to determine whether the polar layered deposits--then thought to consist of 10 to 100 layers each between 10 and 100 meters (33 to 330 feet) thick--have more and thinner layers in them. The layers were proposed to have formed by slow accumulation of dust and ice--perhaps only 100 micrometers (0.004 inches) per year. A layer 10 meters (33 feet) thick would take 100,000 years to accumulate, roughly equal to the timescale of climate changes predicted by computer models.
The image shown here (right image) was taken at 11:52 p.m. PDT on July 30, 1998, near the start of the 461st orbit of Mars Global Surveyor. The picture shows a slope along the edge of the permanent north polar cap of Mars that has dozens of layers exposed in it. The image shows many more layers than were visible to the Viking Orbiters in the 1970s (left images). The layers appear to have different thicknesses (some thinner than 10 meters (33 feet)) and different physical expressions. Some of the layers form steeper slopes than others, suggesting that they are more resistant to erosion. The more resistant layers might indicate that a cement (possibly ice) is present, making those layers stronger. All of the layers appear to have a rough texture that might be the result of erosion and/or redistribution of sediment and polar ice on the slope surface.
The presence of many more layers than were seen by Viking is an important and encouraging clue that suggests that future investigation of polar layered deposits by landers and, perhaps some day, by human explorers, will eventually lead to a better understanding of the of the polar regions and the climate history recorded there. Our view of these deposits will be much improved--starting in late March 1999--when the Mapping Phase of the MGS mission begins, and MOC will be able to obtain images with resolutions of 1.5 meters (5 feet) per pixel.
[The Viking Images (left)]: Regional and local context of MOC image 46103. The small figure in the upper right corner is a map of the north polar region, centered on the pole with 0° longitude located in the lower middle of the frame. A small black box within the polar map indicates the location of the Viking Orbiter 2 image used here for local context. The Viking image, 560b60, was taken in March 1978, toward the end of Northern Spring. The thin strip superposed on the Viking image is MOC image 46103, reduced in size to mark its placement relative to the Viking context image. The black box on the MOC image shows the location of the subframe highlighted here (right image). Illumination is from the left in the Viking image. The 10 kilometer scale bar also represents approximately 6.2 miles.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01479: Detailed View of Cliff-face in the North Polar Layered Deposits sur le site de la NASA.
This crater on northern Elysium Planitia is a little more than twice the diameter of the famous Meteor Crater in Arizona, U.S.A. It formed by the impact and subsequent explosion of a meteorite. Picture from MOC in July 1998.
On Mars, Northern Hemisphere Summer (and Southern Hemisphere Winter) began on December 16, 2000. In this December holiday season, many children across the U.S. and elsewhere are perhaps anticipating an annual visit from a generous and jolly red-suited soul from the Earth's North Pole. As the December holidays were approaching, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) was busy acquiring new views of the region around the martian north pole. The three best views obtained this month are shown here. The top (A) and bottom (C) views show many layers exposed and eroded into the form of ridges and troughs on shallow slopes within the martian north polar cap. The middle (B) view is a picture of the rugged, eroded polar ice cap surface itself. The layers are believed to have formed over tens to hundreds of thousands of years by deposition of dust and ice each cold martian winter. These surfaces today all appear to have been eroded. The brightest material in each image is frost--temperatures at this time of year indicate that the frost is composed of frozen water. In winter, temperatures can be cold enough to freeze carbon dioxide, as well.
Voir l'image PIA02897: North Polar Cap Layers and Frost on the First Day of Summer sur le site de la NASA.
Dark streaks, everywhere! Many Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images of the middle latitudes of the northern and southern hemispheres of Mars show wild patterns of criss-crossing dark streaks. Many of these streaks are straight and narrow, others exhibit curly arcs, twists, and loops. They often cross over hills, run straight across dunes and ripples, and go through fields of house-sized boulders. The two examples shown above were acquired in the last three months. Both pictures are illuminated by sunlight from the upper left. The first picture (left), showing dark streaks on the rippled flats of Argyre Planitia, covers an area 3 km by 5 km (1.9 by 3.1 miles) at a latitude of 51°S. The second picture (right) shows an area approximately 3 km by 5 km in Promethei Terra at a latitude of 58°S.
For many months the MOC science team was seeing streaks such as these, but were uncertain how they formed. One speculation was that they might result from the passage of dust devils. Each dust devil would leave a dark streak by removing bright dust from the terrain in its path, revealing a darker surface underneath. An image described by the MOC team in July 1998 showed examples of streaks that were, at the time, speculated to be caused by dust devils.
Voir l'image PIA02377: Dust Devils Seen Streaking Across Mars: PART 1--What Are These? sur le site de la NASA.
3 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, defrosting spots formed on a polygon-cracked plain in the south polar region of Mars. The surface was covered with carbon dioxide frost during the previous winter. In spring, the material begins to sublime away, creating a pattern of dark spots that sometimes have wind streaks emanating from them, as wind carries away or erodes the frost.
Location near: 87.2°S, 28.4°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
8 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of a pit chain on the lower, northern flank of the giant martian volcano, Arsia Mons. Pits such as these commonly form as a result of collapse of surface materials into a subsurface void, possibly along a fault or into an old lava tube. The layered material, exposed near the top of several of the pits, is shedding house-sized boulders which can be seen resting on the sloping sidewalls and floors of many of the pits.
Location near: 6.7°S, 120.1°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Summer
The surface looks somewhat like that of a kitchen sponge--it is flat on top and has many closely-spaced pits of no more than 2 meters (5.5 ft) depth. The upper, flat surface in this image has a medium-gray tone, while the pit interiors are darker gray. Each pit is generally 10 to 20 meters (33-66 feet) across. The pits probably form as water ice sublimes--going directly from solid to vapor--during the martian northern summer seasons. The pits probably develop over thousands of years. This texture is very different from what is seen in the south polar cap, where considerably larger and more circular depressions are found to resemble slices of swiss cheese rather than a kitchen sponge.
This picture was taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) during northern summer on March 8, 1999. It was one of the very last "calibration" images taken before the start of the Mapping Phase of the MGS mission, and its goal was to determine whether the MOC was properly focused. The crisp appearance of the edges of the pits confirmed that the instrument was focused and ready for its 1-Mars Year mapping mission. The scene is located near 86.9°N, 207.5°W, and has a resolution of about 1.4 meters (4 ft, 7 in) per pixel.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02370: Martian "Kitchen Sponge" sur le site de la NASA.
18 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a group of rounded hills surrounded by a vast, cratered plain in northeastern Isidis Planitia.
Location near: 16.8°N, 262.5°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
In this first week of Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) Mapping operations--i.e., early March 1999--seeing the red planet at 1.5 meters(5 feet) per pixel is quite a new and novel experience. This picture covers a 1.5 kilometer (0.9 miles) wide portion of Isidis Planitia. A person could walk across this scene in a matter of minutes. That person would encounter a variety of small, bright dunes that are perhaps only a few meters/yards high. Careful exploration would also show that the rims of the younger impact craters have rocks and boulders on them (e.g., see crater at center of the picture). Many more images of this quality and resolution lie ahead for MOC as it begins its 687-day Mapping mission. In this picture, the Sun's illumination is from the upper left.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01678: Craters and Bright Dunes of Isidis Planitia sur le site de la NASA.
In April 1998, one of the efforts undertaken by the MOC science team was to test two competing ideas about the history of the Elysium Basin--a huge depression that stretches about 3,000 kilometers(1,865 miles) east-to-west in the region south of the Elysium volcanic rise.
There were two competing ideas about the Elysium Basin. One hypothesis held that the depression was once the site of a vast lake approximately 1,500 meters (4,900 feet) deep. Because the floor of Elysium Basin has very few small, fresh impact craters, it was proposed that this lake dried up relatively recently in martian history--that is, the lake would have been younger than most of the volcanoes, craters, and even the Ares Vallis flood channel in which is located the Mars Pathfinder landing site. At some point, the lake in Elysium Basin was thought to have reached such a depth that it began to spill over arise on its east end. The water spilling out the east end of Elysium Basin was thought to have created Marte Vallis--a channel containing streamlined islands that stretches for hundreds of kilometers (miles)to the northeast. The lake bed and channel, it was proposed, might make good places to land future rovers that could travel around and collect samples that might contain evidence of past martian life.
The other hypothesis held that the Elysium Basin floor was covered with flows that were emplaced as extremely fluid lava (molten rock). It was suggested that a lake of water could have been in the basin long, long ago, but that the most recent geologic events had erupted huge volumes of very fluid lava across the basin floor. Some of this lava was proposed to have even poured out of the basin and travelled down Marte Vallis. In this hypothesis, it was assumed that Marte Vallis--named for the Spanish word for "Mars"--was first carved by water, and then was a conduit for lava from volcanic eruptions. The lavas were proposed to have been very fluid--behaving almost limewater. Such fluid lavas are known on Earth to result from molten rock that has a low concentration of silica, a high temperature, and/or a high eruption rate.
This MOC image, and MOC images 21904 and23804, of the floor of Elysium Basin taken in April 1998 revealed that the basin floor is covered with lava, not lake sediment. In other words, MOC has found that the Elysium Basin might not be a good place to look for evidence of martian life that might have existed in a lake.
However, the lava textures that MOC found are striking and indicate something very important about the geologic history of Mars. The surface texture of this lava includes giant plates that appear to have been broken up and floated on the surface of a fluid. In this case, the fluid was molten lava. The implication is that the Elysium Basin was once the site of giant, ponded lava flows that were many hundreds of kilometers (miles) across.
With the MOC images in hand, it is now quite easy to understand the older, lower-resolution Viking images ( Elysium Basin and Marte Vallis region,Viking 1 base map from 631st orbit,Viking 1 mosaic of local context)These Viking images showed a surface of dark plates with intervening bright surfaces. But they did not make sense--some thought they could somehow be volcanic, others thought they might be related to differences in the way that wind had eroded a dried lakebed. Now it can be seen that there are many dark plates that once floated on molten lava. When the lava was erupted, the upper surface crusted and cooled. The textures in these lavas indicate that they flowed and became cracked. Some cracks widened, and portions of the surface crust became rafts of solid rock--a few many kilometers (miles) across--that moved in the direction that the lava underneath was flowing. Other Viking and MGS images have shown similar platey lava textures in Marte Vallis, suggesting the possibility that some of the lava spilled into this valley and flowed thousands of kilometers (hundreds of miles) to the northeast.
The sparse occurrence of younger impact craters on the platey lava surfaces suggests that the eruptions happened relatively recently in Mars history. These eruptions would be much younger than the youngest of the large martian volcanoes like Ascraeus Mons and Olympus Mons in the Tharsis region; but they would still have occurred many, many millions of years ago (i.e., the pictures are not evidence that Mars is volcanically active today).
The MOC science team is continuing to study the images of Marte Vallis and Elysium Basin. Similar lava textures have been seen elsewhere on the planet, and are leading to some interesting revisions of our understanding of the volcanic and geologic history of the red planet. It should be noted that the observation of a volcanic surface in Elysium basin does not rule out the possibility that the depression was also once the site of a water lake, nor is it clear whether Marte Vallis is the result of volcanism alone, or volcanism that occurred some time after water had been present to carve the channel system.
The results of the initial study of the Elysium Basin are given in a paper entitled "Mars Global Surveyor Camera Tests the Elysium Basin Controversy: It's Lava, Not Lake Sediments," by Alfred S. McEwen, K. S. Edgett, M. C. Malin, L. Keszthelyi, and P. Lanagan, presented at the Geological Society of America Annual Meeting on October 29, 1998.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01494: Ancient Lakes on Mars? Results for Elysium Basin sur le site de la NASA.
1 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a second view of varied springtime defrosting patterns formed in a dune field and surrounding polygon-patterned ground in the south polar region of Mars. The previous view was featured as a MOC Picture of the Day on 20 August 2005 (PIA04162). Both images show portions of the same terrain and occur within a few hundred meters of each other. The previous release explained that the feature sporting an outline of dark spots and an interior of smaller, closely-spaced dark spots and dark-outlined polygons is a patch of windblown or wind-eroded sand that was covered by carbon dioxide frost during the previous autumn and winter. The fainter, larger polygon pattern on either side of the patch of defrosting sand is formed in the substrate upon which the sand patch is sitting. Polygonal forms such as these might indicate the presence of ice below the surface.
Location near: 79.9°S, 125.9°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
The image at left shows the location in the best available image from the Viking Orbiters (approximately 240 m/pixel). The center image is the full image, while at right is an enlarged portion of it. The two right images are available at higher resolution as PIA01025 and PIA01026, respectively.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01024: Valley and Surrounding Terrain Adjacent to Schiaparelli Crater sur le site de la NASA.
The above MOC image, #35704, was obtained on Mars Global Surveyor's 357th orbit. The picture was taken around 1:39 p.m. PDT on June 10, 1998, and its center is around 15.44°S, 309.48°W. This MOC image shows an eroded portion of the thick ejecta (material thrown out of an impact crater during its formation) from a very large impact basin, Huygens. The ejecta appears to have been eroded such that a previously buried crater has been exposed. Alternatively, the crater might have formed after Huygens, but then its eroded appearance would imply considerable erosion and removal of material.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01445: Eroded Crater Adjacent to Huygens Impact Basin sur le site de la NASA.
MOC image of dunes in Chasma Boreale, a giant trough in the north polar cap. This September 1998 view shows dark sand emergent from beneath a veneer of bright frost left over from the northern winter that ended in July 1998.
Shortly after midnight Sunday morning (5 April 1998 12:39 AM PST), the Mars Orbiter Camera (MOC) on the Mars Global Surveyor (MGS) spacecraft successfully acquired a high resolution image of the "Face on Mars" feature in the Cydonia region. The image was transmitted to Earth on Sunday, and retrieved from the mission computer data base Monday morning (6 April 1998). The image was processed at the Malin Space Science Systems (MSSS) facility 9:15 AM and the raw image immediately transferred to the Jet Propulsion Laboratory (JPL) for release to the Internet. The images shown here were subsequently processed at MSSS.
The picture was acquired 375 seconds after the spacecraft's 220th close approach to Mars. At that time, the "Face," located at approximately 40.8° N, 9.6° W, was 275 miles (444 km) from the spacecraft. The "morning" sun was 25° above the horizon. The picture has a resolution of 14.1 feet (4.3 meters) per pixel, making it ten times higher resolution than the best previous image of the feature, which was taken by the Viking Mission in the mid-1970's. The full image covers an area 2.7 miles (4.4 km) wide and 25.7 miles (41.5 km) long.
This Viking Orbiter image is one of the best Viking pictures of the area Cydonia where the "Face" is located. Marked on the image are the "footprint" of the high resolution (narrow angle) Mars Orbiter Camera image and the area seen in enlarged views (dashed box). See PIA01440-1442 for these images in raw and processed form.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01439: Mars Orbiter Camera Views the "Face on Mars" - Best View from Viking sur le site de la NASA.
Two views of Olympus Mons, shown as topography draped over a Viking image mosaic. MOLA's regional topography has shown that this volcano sits off to the west of the main Tharsis rise rather than on its western flank. The topography also clearly shows the relationship between the volcano's scarp and massive aureole deposit that was produced by flank collapse. The vertical exaggeration is 10:1.
Voir l'image PIA02806: Major Martian Volcanoes from MOLA - Olympus Mons sur le site de la NASA.
As the retreat of the south polar winter frost cap became visible in June 1999, high resolution images from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) began to show dark spots forming on the surfaces of frost-covered sand dunes. Immediately, the MOC science team began to plan to observe several dune fields more than once, should that opportunity arise, so that the evolution of these dark spots could be documented and studied. Such work will eventually lead to abetter understanding of how the martian polar caps retreat as winter ends and spring unfolds in each hemisphere.
MGS is in a polar orbit, which means that, unlike many other places on Mars, the spacecraft has more opportunities to take pictures of the same place. Dune fields near 87° latitude can be repeatedly viewed; dunes near the equator are not likely to be photographed more than once during the entire MGS mission.
The pictures presented here show changes on a set of nearly pear-shaped sand dunes located on the floor of an unnamed crater at 59°S, 353°W. The picture on the left shows the dunes as they appeared on June 19, 1999, the picture on the right shows the same dunes on July 15, 1999. The dark spots in the June 19picture--indicating areas where frost has sublimed away--became larger by July 15th. In addition, new spots had appeared as of mid-July. If possible, these dunes will be photographed by MOC again in mid-August and each month until the frost is gone.
The pictures shown in (B) (above) are expanded views of portions of the pictures in (A). The 200 meter scale bar equals 656 feet; the 100 meter bar is 328 feet (109 yards) long. All images are illuminated from the upper left; north is toward the upper right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02302: Defrosting Polar Dunes--Changes Over a 26-Day Period sur le site de la NASA.
Tyrrhenna Patera is thought to be an ancient volcano. It is located in Hesperia Planum in the martian southern hemisphere. The Mars Orbiter Camera recently acquired this view of escarpments and valleys on the lower northeast flank of the volcano. Small, bright dunes cover low areas such as valley and crater floors. The picture is illuminated from the lower right and covers an area 3 kilometers (1.9 miles) across.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Are these dunes? One of the most puzzling findings of the Mars Global Surveyor Mars Orbiter Camera investigation has been the discovery of many surfaces of sharp, parallel ridges and grooves that--at first glance--look like dunes, but upon closer inspection turn out to be something else. They aren't dunes because they occur too close together, their crests are too sharp, and their slopes are too symmetrical. In most places that they occur on Mars, they appear to be occurring within a specific layer of (usually) dark material. Exactly what processes make these ridges is a mystery, but it clearly involves some sort of erosion. Dark mesas in this picture of the floor of Melas Chasma in the Valles Marineris system are developing sharp, parallel troughs and pits that appear to eventually erode to become the fields of ridges seen throughout the rest of the image. Dark, ridged surfaces like this are common in the central floors of Valles Marineris and elsewhere in the equatorial regions of Mars, and present a type of surface that may need to be avoided by future Mars landers. This image, illuminated by sunlight from the left, covers an area 3 kilometers (1.9 miles) wide and 14.5 kilometers (9 miles) long. The scene is located near 8.8°S, 76.8°W and was acquired on March 22, 1999.
Voir l'image PIA02801: Ridged Terrain on the Floor Melas Chasma sur le site de la NASA.
During the Mars Orbiter Camera (MOC) focus and calibration testing period in the first week of March 1999, small pictures of surfaces in the north polar region were used to check the quality of each change in the camera's focus. Some of these pictures showed the north polar permanent ice cap, while others provided a close-up view of some of the dark sand dunes that surround the north polar region. This picture shows the best example. The dunes here are dark and their slipfaces--the steep slope on the dune's lee side--is on the left of each dune, indicating wind transport from right to left in this particular location. The substrate between the dunes is bright and has a rough, bumpy texture. The picture covers an area 1000 meters (1094 yards) by 400 meters (437 yards). Illumination is from the lower right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
4 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a landscape in the eastern Cerberus region that was scoured by catastrophic floods, and later cut by a deep, dark-walled trough. The trough is radial to the Elysium volcanic region, and formed along faults in the bedrock.
Location near: 15.7°N, 196.6°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
This type of bedrock layering has never been seen before in Valles Marineris. It calls into question common views about the upper crust of Mars, for example, that there is a deep layer of rubble underlying most of the martian surface, and argues for a much more complex early history for the planet.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01023: Western Tithonium Chasma/Ius Chasma, Valles Marineris - High Resolution Image sur le site de la NASA.
Shortly after midnight Sunday morning (5 April 1998 12:39 AM PST), the Mars Orbiter Camera (MOC) on the Mars Global Surveyor (MGS) spacecraft successfully acquired a high resolution image of the "Face on Mars" feature in the Cydonia region. The image was transmitted to Earth on Sunday, and retrieved from the mission computer data base Monday morning (6 April 1998). The image was processed at the Malin Space Science Systems (MSSS) facility 9:15 AM and the raw image immediately transferred to the Jet Propulsion Laboratory (JPL) for release to the Internet. The images shown here were subsequently processed at MSSS.
The picture was acquired 375 seconds after the spacecraft's 220th close approach to Mars. At that time, the "Face," located at approximately 40.8° N, 9.6° W, was 275 miles (444 km) from the spacecraft. The "morning" sun was 25° above the horizon. The picture has a resolution of 14.1 feet (4.3 meters) per pixel, making it ten times higher resolution than the best previous image of the feature, which was taken by the Viking Mission in the mid-1970's. The full image covers an area 2.7 miles (4.4 km) wide and 25.7 miles (41.5 km) long.
In this comparison, the best Viking image has been enlarged to 3.3 times its original resolution, and the MOC image has been decreased by a similar 3.3 times, creating images of roughly the same size. In addition, the MOC images have been geometrically transformed to a more overhead projection (different from the mercator map projection of PIA01440 & 1441) for ease of comparison with the Viking image. The left image is a portion of Viking Orbiter 1 frame 070A13, the middle image is a portion of MOC frame shown normally, and the right image is the same MOC frame but with the brightness inverted to simulate the approximate lighting conditions of the Viking image.
Processing Image processing has been applied to the images in order to improve the visibility of features. This processing included the following steps:
The image was processed to remove the sensitivity differences between adjacent picture elements (calibrated). This removes the vertical streaking.
The contrast and brightness of the image was adjusted, and "filters" were applied to enhance detail at several scales.
The image was then geometrically warped to meet the computed position information for a mercator-type map. This corrected for the left-right flip, and the non-vertical viewing angle (about 45° from vertical), but also introduced some vertical "elongation" of the image for the same reason Greenland looks larger than Africa on a mercator map of the Earth.
A section of the image, containing the "Face" and a couple of nearly impact craters and hills, was "cut" out of the full image and reproduced separately.
See PIA01440-1442 for additional processing steps. Also see PIA01236 for the raw image.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01442: Mars Orbiter Camera Views the "Face on Mars" - Comparison with Viking sur le site de la NASA.
Crater at 6°S, 184°W on 01 FEB 1998
What is happening on Mars right now? Pictures that show changes occurring from time to time give some clues as to what processes are shaping the modern martian landscape. Dust devils, dust storms, and polar frosts are all known to cause change sin the surface every martian year. But what about other geologic processes? How "active" is Mars today? The Mars Orbiter Camera (MOC) onboard the Mars Global Surveyor (MGS) has been in orbit long enough that it is starting to provide some answers. MGS began orbiting Mars in September 1997. Since that time, it has seen the planet cycle through more than 1 of its 687-Earth-days-long years. The pictures shown here document changes observed by the MOC caused by small landslides.
The picture at the lower left (above) shows a shallow crater located near Apollinaris Patera at 6°S, 184°W, that was photographed by MOC in February 1998. The walls of this crater exhibit approximately 100 dark streaks running down its slopes. These streaks have formed as small landslides or avalanches and are probably composed of sand and/or silt. The image is illuminated by sunlight from the lower left, and the crater is about 5 kilometers (3 miles) across. The white box shows the location of a section of the crater that was photographed again in mid-November 1999, about 92% of a Martian Year later.
The top picture shows a comparison of the southeastern crater wall as it appeared on February 1, 1998, and again on November 18, 1999. (Note that the picture has been rotated relative to the context image at lower left). During the time between the two images, three new dark slope streaks formed (arrows, top right). The older streaks are lighter and fainter than these new, dark ones, suggesting that streaks fade with time. This means that, at least for the crater walls shown here, any streak that is dark is younger than any streak that is pale. The stereo anaglyph (requires red-blue "3-d glasses") at the lower right uses the two images of the crater rim to provide a 3-dimensional view. The anaglyph is helpful to see that the dark streaks really do occur on a slope. In addition, by viewing the anaglyph without 3-d glasses, one can easily identify the three new streaks because they appear as blue and have no red counterpart.
These three new slope streaks formed sometime between February 1998 and November 1999. Similar streaks were observed in the highest-resolution images from the Viking orbiters in the late 1970s, but for more than 20 years no one has known how recent these features might be, or how often they might form. Now, MOC is providing some exciting answers.
Voir l'image PIA02379: Recent Movements: New Landslides in Less than 1 Martian Year sur le site de la NASA.
12 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a mid-summer view of layered terrain in the south polar region of Mars. The general hypothesis that has been around since the Mariner missions to Mars in the late 1960s and early 1970s is that the layered material in the polar regions is composed of some combination of dust and ice in unknown proportions. Alternatively, the layers might be ancient sedimentary rock, perhaps protected from erosion by millennia of seasonal ice caps covering the region for, roughly, half a Mars year.
Location near: 80.1°S, 259.7°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
17 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows alternating ridges and troughs exposed by erosion of material interpreted to be sedimentary rock in the Aeolis region of Mars.
Location near: 1.9°N, 218.6°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) continues to provide a stunning array of images that show the red planet to have a very diverse collection of surface textures and properties. This picture shows a 3 kilometers (1.9 miles) by 4.4 kilometers (2.7 miles) portion of the floor of Melas Chasma. Dark sand dunes spaced 55to 60 meters (~190 feet) apart dominate the floor of this portion of the Valles Marineris canyon system. Smaller ripples are also visible in the troughs between some of the dunes, perhaps indicating a modern, dynamic eolian (i.e., wind-swept) environment. Illumination is from the upper left.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Layers of wall rock, windblown drifts, and landslide deposits can be seen in this new view of the wall of Tithonium Chasma in the Valles Marineris trough system. The picture covers an area 3 kilometers (1.9 miles) wide by about 11 kilometers (6.8 miles) long and is illuminated from the lower right. The Mars Orbiter Camera on board the Mars Global Surveyor spacecraft acquired this dramatic picture in early April 1999.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
12 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of an old impact crater in the Sinus Sabaeus region of Mars, just south of the large impact basin, Schiaparelli.
Location near: 6.3°S, 341.7°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
Five images are shown above:
(A) is an excerpt from the USGS MDIM, roughly 180 km (112 mile) square. The small box outlines the MOC image acquisition.
(B) is MOC frame P006_05, shown here at reduced resolution because the full image is almost 7 MBytes in size. Because the MOC acquires its images one line at a time, the cant angle towards the sun-lit portion of the planet, the spacecraft orbital velocity, and the spacecraft rotational velocity combined to significantly distort the image. However, even in this reduced resolution version, dunes can be seen in the canyon and in areas on the upland surface around the canyon.
(C) shows a portion of P006_05 at the full resolution of the data. This view shows the dunes more clearly, and also illustrates better the distortion introduced by the method of data acquisition.
(D) shows P006_05 skewed and rotated to the perspective that MOC was viewing at the time the image was taken.
(E) shows a full-resolution version of a portion of the rotated perspective view.
Nirgal Vallis is one of a number of canyons called valley networks or runoff channels. Much of the debate concerning the origin of these valleys centers on whether they were formed by water flowing across the surface, or by collapse and upslope erosion associated with groundwater processes. At the resolution of this image, it is just barely possible to discern an interwoven pattern of lines on the highland surrounding the valley, but it is not possible to tell whether this is a pattern of surficial debris (sand or dust), as might be expected with the amount of crater burial seen, or a pattern of drainage channels. With 4X better resolution from its mapping orbit, MOC should easily be able to tell the difference between these two possibilities.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The spacecraft has been using atmospheric drag to reduce the size of its orbit for the past three weeks, and will achieve a circular orbit only 400 km (248 mi) above the surface early next year. Mapping operations begin in March 1998. At that time, MOC narrow angle images will be 5-10 times higher resolution than these pictures.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA00942: MGS Views of Nirgal Vallis sur le site de la NASA.
Mars is a desert planet in which wind has a considerable effect on the landscape. Bright and dark wind streaks in this image indicate past movement of fine sediment across the landscape from upper left toward lower right. Two impact craters that look like flowers or starfish are seen in the lower portion of the image. The ejecta deposits of these craters are raised above the surrounding terrain, and indicate that wind has deflated a layer of material (that is, blown it away, thus lowering the surface) that was present at the time that the craters formed. The craters were formed by impacts of meteorites into the earlier, higher surface, and the rocks and gravel thrown out when they formed protected some of this former layer from the wind's effects. This picture--showing part of the Medusae Fossae region near the martian equator--was taken in early April 1999 and covers an area only 1 kilometer (0.62 miles)wide. Illumination is from the lower right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
High-resolution images from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) have revealed small cone-shaped structures on lava flows in southern Elysium Planitia, Marte Valles, and northwestern Amazonis Planitia in the northern hemisphere of the red planet. The most likely interpretation of these cones is that they may be volcanic features known as "pseudo craters" or "rootless cones." They share several key characteristics with pseudo craters on Earth: they are distributed in small clusters independent of structural patterns, are superimposed on fresh lava flows, and they do not appear to have erupted lavas themselves.
The white box in the picture above left shows the location of one of the MOC images of possible pseudocraters on Mars. The white box is drawn upon a MOC red wide angle context image acquired at the same time as the high resolution view, shown on the right above. Located in northwestern Amazonis Planitia near 24.8°N, 171.3°W, both the context image and high-resolution view are illuminated from the lower left. The high resolution view shows several possible pseudocraters (cone-shaped features with holes or pits at their summits) that occur on top of a rough-textured lava plain. The context frame covers an area 115 km (71 mi) across, the high-resolution view is 3 km (1.9 mi) across.
Pseudocraters form by explosions due to the interaction of molten lava with a water-rich surface. Possible martian pseudocraters are of interest because they may mark the locations of shallow water or ice at the time the lava was emplaced.
Viking Orbiter images have shown structures in other regions of Mars that were interpreted to be pseudocraters, but the interpretations were uncertain because the morphology was poorly resolved, it was unclear if they occurred on volcanic surfaces, and they have diameters as much as a factor of 3 larger than terrestrial pseudocraters. The cone-shaped morphology is well resolved in the cones imaged by MOC, and they have basal diameters of less than 250 m (273 yards), consistent with terrestrial examples. The cones rest on a surface with a distinctive morphology consisting of ridged plates that have rafted apart, which MOC team members have interpreted as the surface of voluminous lava flows.
The surface shown here (above right) looks relatively fresh and has very few impact craters on it, which suggests that the lava flows and the cones are both geologically young. However, MOC images in other areas reveal such apparently young surfaces being exhumed (presumably by wind erosion) from beneath a blanket of overlying material. Impact processes may harden the blanket, or cover it with materials that cannot be removed by wind, so the wind erosion leaves behind elevated "pedestalcraters." The cones shown here are not typical of pedestal craters, but it is important to consider this alternative interpretation.
MGS MOC first began taking pictures of Mars in mid-September 1997. The planet that has been revealed by this camera is often strange, new, and exciting. The possibility that lava and water or ice have interacted to create features like pseudocraters indicates that Mars has had a diverse and complex past that researchers are only just beginning to understand.
Voir l'image PIA02341: Possible Rootless Cones or Pseudo craters on Mars sur le site de la NASA.
141 c
What is 8 kilometers (5 miles) high, forms in the mid-afternoon, and cannot be found the next day?
A Martian dust devil! The arrow in the left image (MOC2-141a, above) points to the tallest (8 km, 5 mi) of several dust devils spied by the Mars Global Surveyor MOC Wide Angle camera during its global geodesy campaign in May.
The above two pictures (MOC2-141a and MOC2-141b, top row) are centered near 36°N, 159°W in northern Amazonis Planitia. Each image covers an area 88 kilometers(55 miles) across, and each shows similar features on the ground, such as the two partially-buried craters at the center left.
Each image also shows features that are not found in the other image. These are dust devils. Each scene is illuminated by sunlight from the lower left-- thus each towering dust devil casts a long, dark shadow that points toward the right/upper right. The "movie" (lower row, MOC2-141c) shows a comparison of the two images. When viewing the "movie," note that permanent features such as the two partly buried craters do not move, but the dust devils in one image do not appear in the other. Different dust devils are seen in each of the two images. Other variations in apparent surface brightness are also seen when the two images are compared--these are thought to be places where smaller, ground-hugging dust plumes are also being "kicked-up" by the wind.
The pictures were taken 2 days apart--the first on May 13, 1999, the second on May 15, 1999. Large dust devils were known to occur in this region because they were seen in Viking images 20 years ago, but the new and repeated coverage by MOC gives more information about the dust devil's shape and occurrence. Dust devils are columnar vortices of wind that move across the landscape, pick up dust, and look somewhat like miniature tornadoes. For more information on dust devils, see MOC image release MOC2-60 from July 1998, "SUV Tracks on Mars? The Devil is in the Details."
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
This image continues the theme of things eroded, things covered up, and then exposed again. The circular feature labeled, "Partly-Exhumed Crater," is interpreted to be an ancient impact crater that formed on the same layered rock surface into which the channel in PIA02844 was cut. This crater, like the channel in PIA02844, indicates that the layered rock was exposed to the atmosphere for some period of time before the next layer of material--the bright, almost white ridged rock that covers most of the upper half of this picture--was deposited. In this scenario, the sedimentation ceased long enough for the lower rocks seen here to remain exposed, so that meteorites could hit the surface and form craters. These craters were then buried by the bright material that still covers about 1/3 of the partly-exhumed crater in this scene. When an ancient erosion surface, such as that into which the crater formed, is buried by additional layers of material, a gap in the geologic record is created. Geologists call a gap such as this an erosional unconformity.
Note: This is a subframe of PIA02843
Voir l'image PIA02845: Sediment History Preserved in Gale Crater Central Mound sur le site de la NASA.
The layered terrains of the polar regions of Mars are among the most exotic planetary landscapes in our Solar System. The layers exposed in the south polar residual cap, vividly shown in the top view, are thought to contain detailed records of Mars' climate history over the last 100 million years or so. The materials that comprise the south polar layers may include frozen carbon dioxide, water ice, and fine dust. The bottom picture shows complex erosional patterns that have developed on the south polar cap, perhaps by a combination of sublimation, wind erosion, and ground-collapse. Because the south polar terrains are so strange and new to human eyes, no one (yet) has entirely adequate explanations as to what is being seen.
These images were acquired by the Mars Orbiter Camera aboard the Mars Global Surveyor spacecraft during the southern spring season in October 1999. Each of these two pictures is a mosaic of many individual MOC images acquired at about 12 m/pixel scale that completely cover the highest latitude (87°S) visible to MOC on each orbital pass over the polar region. Both mosaics cover areas of about 10 x 4 kilometers (6.2 x 2.5 miles) near 87°S, 10°W in the central region of the permanent--or residual--south polar cap. They show features at the scale of a small house. Sunlight illuminates each scene from the left."Gaps" at the upper and lower right of the second mosaic, above, are areas that were not covered by MOC in October 1999.
Voir l'image PIA02390: High-Resolution South Polar Cap Mosaics sur le site de la NASA.
What is Mars Polar Lander going to find when it touches down on December 3rd? The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has been providing some spectacular previews. The following series of 7 figures illustrates the variety of surface textures, terrains, and geologic features that are found in the landing ellipse located at 76°S 195°W. It is now late southern spring, and the frost that covered this region for most of 1999 has gone away.
The focus here is upon a "tour" of a single MOC image obtained on November 26, 1999. In each figure below, the landing ellipse appears as a blue outline, the MOC image is drawn in orange, and the portion of the MOC image generally illustrated in each figure is yellow. The November 26th MOC image covers approximately 120 sq. km (75 sq. miles) of the central portion of the landing ellipse. The image is 3 km (1.9 mi) wide by 40 km (25 mi) long and has a resolution of about 4 meters (13 feet) per pixel. In each view, south is toward the top and the sun illuminates each scene from the lower right. The scale bar in each picture, 250 meters, is equal to 273 yards (820 ft).
Parallel Ridges with Rough Texture and Residual Frost
This picture shows a set of parallel ridges trending from upper left to lower right, spaced about 250-500 meters (273-547 yards) from one another. The amplitude of these ridges is not known, but elsewhere they are less than 20 m (66 ft) high. The surface also has irregular, light-toned knobs that resemble large boulders or pinnacles.
Parallel Ridges and Mounds with Gullies and Irregular Pits
A large portion of the landing ellipse (and the majority of the area seen in this image) is covered by parallel ridges surmounted by isolated groups of gullies and pits. The gully systems typically extend less than 500 meters(547 yards), and are often only a few hundred meters across. These gullies do not show the integration normal for fluid erosion (i.e., they were not carved by running water); instead, they have the form of cracks and depressions expanded by wall- and head-enlargement by processes such as sapping (removal of wall support by fluid seepage or the evaporation of ground ice) or ablation (removal of ices by sublimation and wind).
Low Relief with Subtle Depressions and Small Knobs
Some areas show little or no topographic relief (i.e., the area is relatively flat with no hills, ridges, or gullies). One class of this type of surface displays small, subtle, isolated depressions and areas of the rough texture made up of light-toned patches of knobs that resemble large boulders or pinnacles.
Dark Sand Dunes and Bright Low Relief Surface with Gullies
The darkest surface in the landing ellipse, now seen without its seasonal bright frost cover, shows the unmistakable form of dark sand dunes. This image shows the margin of the dune field that crosses the center of the MOC image. Note that in some places the sand depth is shallow and the shape and slopes of the underlying features can be seen.
Weakly-organized Ridges/Mounds and Gullies/Depressions
The second-most abundant surface texture in this portion of the landing ellipse consists of poorly aligned ridges and depressions which occasionally display steep wall slopes. This surface appears rugged at the scale of tens of meters, but may be smoother at small scales(meters).
Smooth Surface with Occasional Ridges and Pits
The southern-most portion of the November 26th MOC image shows a pattern of small, isolated ridges and a few irregular depressions and pits. However, much of the surface is actually quite smooth compared to other portions of the landing ellipse.
Representative Features of the Central Landing Ellipse
The illustration above shows a summary of the landforms seen within the November 26thMOC image in different colors. It is clear that the smoothest surface (green at bottom of frame) is rare in this part of the landing ellipse. Sand dunes (black) and really rough terrain (orange) are also fairly rare. Much of the surface is ridged with either gullies or pits.
Voir l'image PIA02346: Mars Polar Lander Landing Zone Compared With JPL sur le site de la NASA.
This view of the lower south flank of the Olympus Mons volcano shows lava flows with leveed central channels and a variety of surface textures. The picture was taken in July 1998.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dark, relatively smooth plain in the central Terra Meridiani region of Mars. The larger circular features in the upper three-quarters of the image are thought to be the locations of buried craters formed by meteorite impact. The cluster of smaller circular features in the bottom quarter of the scene represent a field of craters formed either by simultaneous impact of many meteorites, or there-impact of material thrown from a much, much larger nearby crater as it formed. The dark material covering these plains includes an abundance of the iron oxide mineral, hematite, that was detected by the MGS Thermal Emission Spectrometer (TES). During late 1999, the "hematite region," as it came to be called, emerged along with the Libya Montes as one of the top two choices of landing sites for the now-canceled Mars Surveyor 2001 lander. This image, illuminated by sunlight from the left, covers an area 3 kilometers (1.9 miles) wide and 19 kilometers (11.8 miles) long. The scene is located near 2.2°S, 3.7°W and was acquired on August 19, 1999.
Voir l'image PIA02397: The Plains of Central Terra Meridiani sur le site de la NASA.
25 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the remains of a once more laterally extensive layer overlying undulating terrain very near the south polar residual cap. Removal of the overlying layer has created "windows" through which are revealed topographic variations in the underlying material, predominantly manifested in the form of ridges which run diagonally, from the southwest (lower left) to the northeast (upper right), across the scene.
Location near: 86.9°S, 196.0°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
Labyrinthus Noctis near the crest of a large (many thousands of kilometers) upcoming of the Martian crust, and the 2000 meter (6500 foot) deep canyons visible in these pictures are bounded by faults. Debris shed from the steep slopes has moved down into after the canyons opened. Small dunes are seen in the lowest area, beneath the high cliffs.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The spacecraft has been using atmospheric drag to reduce the size of its orbit for the past three weeks, and will achieve a circular orbit only 400 km (248 mi) above the surface early next year. Mapping operations begin in March 1998. At that time, MOC narrow angle images will be 5-10 times higher resolution than these pictures.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA00945: MGS Views of Labyrinthus Noctis sur le site de la NASA.
The ancient cratered terrains of Mars exhibit many branching valley "networks." These were first observed by Mariner 9 in 1972, and immediately they were considered to be evidence that Mars had liquid water running across its surface during its earliest years(i.e., about 4 billion years ago). The Mars Global Surveyor(MGS) Mars Orbiter Camera (MOC) took pictures of a number of valley networks in the martian heavily cratered terrains during late 1997 and early 1998. Seen at resolutions ranging from 2 to 30 meters (7 to 98 feet) per pixel, most of these valley networks are found to be so old that their floors are covered by dunes and their walls obscured by dust and debris. Because of this obscuration, many of the small features that could be used to determine the origin of these valleys are missing.
The MOC image 24106 subframe (above) shows a portion of a typical valley network system in central Terra Meridiani near the martian Equator and Prime Meridian. The surface into which the valley has formed has a low albedo (that is, it is dark) and exhibits many circular impact craters and pits. The valley appears brighter than its surroundings, owing to sand and dust deposits; bright sand can also be seen on the floors of craters. The outline of the valley wall shows attributes--for example, various protrusions and alcoves--that suggest the margin of a lava flow (which would be consistent with the dark surface). Crater-like rings within the valley adjacent to the wall are the resistant portions of impact craters that survived the retreat of the wall as the valley widened. This is evidence that processes of valley widening were relatively gentle, probably related to groundwater seeping from beneath a resistant cap of volcanic rock.
MOC image 24106 was taken on April 14, 1998. The subframe shown here covers an area 11.5 km by 27.4 km (7.1 miles by 17.0 miles) in size. The image as presented here has a resolution of about 22.4 meters (74 feet) per pixel. The subframe is centered at 6.2°S latitude and 357.4°W longitude.(CLICK HERE for a context image). North is approximately up, illumination is from the lower right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01499: Mars Water: Valley Networks sur le site de la NASA.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01029: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris - High Resolution Image sur le site de la NASA.
One of the original objectives of the Mars Orbiter Camera (MOC) when it was proposed to NASA in 1985 was to take pictures that would be used to assess future spacecraft landing sites. Images obtained by the Mars Global Surveyor (MGS) MOC since March 1999 provide the highest resolution views (1.5 to 4.5 meters (5-15 ft) per pixel) of the planet ever seen. Over the past several months, MOC science personnel have been examining these new data to develop a general view of what Mars is like at the meter-scale within the general latitude and elevation range that will be accessible to the Mars Surveyor 2001 lander. (i.e., about 5°N to 15°S latitude and lower than 2.5 km (1.6 mi) elevation).
Because MOC images only cover a tiny fraction of one percent of the surface of Mars, we have been seeking general correlations that exist between what is seen in a MOC high-resolution image and what can be seen in the lower-resolution Viking and Mariner 9 images taken in 1972 and 1976-1980.
The most important results thus far are illustrated in the four pictures above. Nearly 70% of the terrain examined follows two very simple, but unexpected "rules" -- (1) If the terrain appears rugged at the hundreds of meters to kilometers scale in a Viking or Mariner image, then it will appear smooth at the meter-scale in a MOC image. (2) If the terrain appears to be smooth in the Viking or Mariner image, it will be rough in the meter-scale MOC image.
The image pair above illustrates the second "rule." Areas that appear to be smooth in the Viking and Mariner images--as in MOC2-138a (left)--tend to look quite rough at the meter scale in MOC images like MOC2-138b (right). The rough texture in this particular case was probably cause by wind erosion.
The Viking image shown here is illuminated from the upper right, while the MOC image is illuminated from the upper left. The MOC image was taken in April 1999, while the Viking image was obtained in the late 1970s. More details about this work are provided in an extended abstract (in Acrobat® PDF format) by M.C. Malin, K. S. Edgett, and T. J. Parker, "Characterization of terrain in the Mars Surveyor 2001 landing site latitude and elevation region using Mapping Phase Mars Global Surveyor MOC images," presented at the Second Mars Surveyor Landing Site Workshop, held June 22-23, 1999, in Buffalo, New York.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Some portions of the martian south polar residual cap have long, somewhat curved troughs instead of circular pits. These appear to form in a layer of material that may be different than that in which "swiss cheese" circles and pits form, and none of these features has any analog in the north polar cap or elsewhere on Mars. This picture shows the "fingerprint" terrain as a series of long, narrow depressions considered to have formed by collapse and widening by sublimation of ice. Unlike the north polar cap, the south polar region stays cold enough in summer to retain frozen carbon dioxide. Viking Orbiter observations during the late 1970s showed that very little water vapor comes off the south polar cap during summer, indicating that any frozen water that might be there remains solid throughout the year.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image was obtained in early southern spring on August 4, 1999. It shows an area 3 x 5 kilometers (1.9 x 3.1 miles) at a resolution of about 7.3 meters (24 ft) per pixel. Located near 86.0°S, 53.9°W.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02373: Mars South Polar Cap "Fingerprint" Terrain sur le site de la NASA.
First, Mars seemed to be greeting Mars Global Surveyor (MGS) with a Happy Face. Now, it seems as if the planet is sending its love with the latest picture (above, left) from MGS's Mars Orbiter Camera (MOC).
This valentine from Mars (above, left) is actually a pit formed by collapse within a straight-walled trough known in geological terms as a graben. Graben are formed along fault lines by expansion of the bedrock terrain (see "Chain of Pits on Pavonis Mons" for more information). The graben in which the pit formed can be seen in the full MOC image, depicted on the right (above).
The heart-shaped pit is about 2.3 kilometers (1.4 miles) at its widest. The image was targeted by the MOC team in order to examine the relationship between a lava flow (margins indicated by white arrows, above right) and the graben and pits that disrupted and cut across the flow. The graben, pit, and lava flow are located on the east flank of the Alba Patera volcano in northern Tharsis. The MOC images are illuminated from the left.
For another heart shaped image from Mars click here.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.Orbit 338 was the first orbit on which MOC obtained pictures following solar conjunction. This orbit executed on June 1, 1998. The picture above shows a 12.3 meters (40 feet) per pixel view of the floor of an ancient, eroded, 47 kilometer (29 miles) wide impact crater.
The most striking feature in this image is the small crater with dark ejecta on the far right side. This crater, formed by a meteor impact, is only about 38 meters (125 feet) across. The blast that formed the crater sent out ejecta in a radial pattern around the impact site. The ejecta pattern may be dark because subsurface dark material was thrown out by the impact or because the disturbed ground reflects less light. By martian standards, this crater is quite young--so young that fine, bright dust that has not yet covered it up. While interpreted to be geologically young, the crater is definitely more than 18 years old, because it is visible as a small, dark spot in the Viking context image taken in 1980. Also visible in this image are some small wind-blown dunes and many small mesas and buttes that probably formed by erosion.
The MOC image 33806 subframe is located at 9.94°N, 311.23°W, in the eastern Arabia Terra region of Mars. The picture was taken at 8:15 a.m. PDT on June 1, 1998.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01434: Small, Fresh Impact Crater With Dark Ejecta sur le site de la NASA.
During the first week of May 1999, the Mars Orbiter Camera (MOC) spent sometime peering into martian impact craters.
This crater is located in south-central Syria Planum and is about 7.0 kilometers (4.4 miles) across. Illumination is from the upper left.
If you have ever visited the famous Meteor Crater in northern Arizona, U.S.A., then you are aware of its immense size on a human scale. The Arizona crater, however, is only 1 kilometer across (0.62 miles), whereas this crater is seven times wider.
This crater was formed by the impact and explosion of a meteorite at some time in the martian past. After the crater formed, it was modified by wind and erosion. The crater shows deposits of sand and dust on the floor and in low areas around their rim, also boulders and other debris that has slid down the inside walls of the crater; and some crater walls show exposures of bedrock.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
27 November 2006
Dust-covered lava flows on the lowermost south flank of Olympus Mons are captured in this 3 kilometers (1.9 miles) wide Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view acquired during northern summer on 12 October 2006. One leveed lava channel just south (below) the center left of the image disappears into a thick, pitted and cratered dust mantle. Sunlight illuminates the scene from the left/upper left. The image is located near 13.8°N, 134.1°W. North is toward the top/upper right.
Despite evidence of catastrophic floods and integrated valley networks on Mars, unequivocal evidence of ponding has been difficult, if not impossible, to find. MOC image 7707 shows what, at first examination, appears to be such evidence. There are two striking geomorphic attributes of the crater shown in the image: (1) The crater wall shows channeling suggestive of fluid seepage; and (2) The contact (i.e., the boundary between two types of geologic materials) between the dark floor materials and the lighter materials of the crater wall suggests, by the formation of bays and peninsulas, a ponding relationship.
These relationships are best and most easily explained if, at some time in the past, water seeped out of layers within the crater wall and flowed down into the crater, flooding part of the crater floor. In this interpretation, the dark material may be sediment transported by the seeping water. The appearance of dunes within the crater may be coincidental, or the sand may have been generated by wind and wave action. The lack of superimposed fresh impact craters suggests this process may have been active relatively recently.
It is important to note that both the channel and floor relationships seen in this image may be formed by other processes, and that there is also the possibility that they may not be related (i.e., that the fluid from the channels did not emplace the dark, ponded floor material). It is also important to remember that a fluid other than water, for example, fluid lava, could be responsible for the features seen. Indeed, lower resolution Viking and some MOC images suggest just such an alternative explanation. The absence of craters may reflect the difficulty of the materials to preserve such features, or their burial by dust. Finally, the environmental difficulties of having liquid water seeping from the wall of a south polar crater are quite formidable. For these reasons, caution must be exercised in adopting any specific hypothesis.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01433: Seepage and Ponding within a Southern Hemisphere Crater sur le site de la NASA.
One of the original objectives of the Mars Orbiter Camera (MOC) when it was proposed to NASA in 1985 was to take pictures that would be used to assess future spacecraft landing sites. Images obtained by the Mars Global Surveyor (MGS) MOC since March 1999 provide the highest resolution views (1.5 to 4.5 meters (5-15 ft) per pixel) of the planet ever seen. Over the past several months, MOC science personnel have been examining these new data to develop a general view of what Mars is like at the meter-scale within the general latitude and elevation range that will be accessible to the Mars Surveyor 2001 lander. (i.e., about 5°N to 15°S latitude and lower than 2.5 km (1.6 mi) elevation).
Because MOC images only cover a tiny fraction of one percent of the surface of Mars, we have been seeking general correlations that exist between what is seen in a MOC high-resolution image and what can be seen in the lower-resolution Viking and Mariner 9 images taken in 1972 and 1976-1980.
The most important results thus far are illustrated in the four pictures above. Nearly 70% of the terrain examined follows two very simple, but unexpected "rules" -- (1) If the terrain appears rugged at the hundreds of meters to kilometers scale in a Viking or Mariner image, then it will appear smooth at the meter-scale in a MOC image. (2) If the terrain appears to be smooth in the Viking or Mariner image, it will be rough in the meter-scale MOC image.
The image pair above illustrates the first "rule." MOC2-137a (left) shows a rugged plain in the martian southern cratered highlands near the Nepenthes Mensae. The small white box indicates the location of the MOC image, which is on the right (MOC2-137b). The MOC image reveals that while the terrain is rough at the large scale, it is quite smooth at the meter-scale.
The Viking image shown here is illuminated from the upper right, while the MOC image is illuminated from the upper left. The MOC image was taken in April 1999, while the Viking image was obtained in the late 1970s. More details about this work are provided in an extended abstract (in Acrobat® PDF format) by M.C. Malin, K. S. Edgett, and T. J. Parker, "Characterization of terrain in the Mars Surveyor 2001 landing site latitude and elevation region using Mapping Phase Mars Global Surveyor MOC images," presented at the Second Mars Surveyor Landing Site Workshop, held June 22-23, 1999, in Buffalo, New York.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
While Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images have shown that the north and south polar cap surfaces are very different from each other, one thing that the two have in common is that they both seem to have been eroded. Erosion in the north appears mostly to come in the form of pits from which ice probably sublimed to vapor and was transported away from the polar cap by wind. Erosion in the south takes on a wider range of possible processes that include collapse, slumping and mass-movement on slopes, and probably sublimation. Among the landforms created by these process on the south polar cap are the "aprons" that surround mesas and buttes of remnant layers such as the two almost triangular features in the lower quarter of this image. The upper slopes of the two triangular features show a stair-stepped pattern that suggest these hills are layered.
This image shows part of the south polar residual cap near 86.9°S, 78.5°W, and covers an area approximately 1.2 by 1.0 kilometers (0.7 x 0.6 miles) in size. The image has a resolution of 2.2 meters per pixel. The picture was taken on September 11, 1999.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02374: South Polar Cap Erosion and Aprons sur le site de la NASA.
22 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a transition from one of the many layered troughs in the north polar region of Mars to the relatively homogeneous-looking upper surface of the polar cap. The difference in brightness across this scene is a function of several factors, one of which is the amount of dust versus that of ice in any given location. The bright material that dominates the scene is largely water ice.
Location near: 83.2°N, 297.8°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower right
Season: Northern Summer
The Mars Global Surveyor Mars Orbiter Camera narrow angle image (top) shows what, at first glance, might look like a "hot crossed bun" on the martian northern plains. The context for this landform is shown in the picture on the right. Unlike the southern highlands of Mars, the northern plains are lower and have far fewer impact craters on them. The relatively few craters that are present in the north have been severely eroded and/or buried. The context image shows a circle of mounds on the northern plains near the Phlegra Montes. These mounds were once the rim of a crater formed by impact of a meteorite. The mound in the high-resolution view (top) has been cracked and was at one time mostly covered by a thin veneer of light-toned material that is now seen only partly covering it. These two pictures were taken simultaneously on August 16, 1999, and occur near 45.9°N, 191.1°W. Both images are illuminated by sunlight from the lower right, the high resolution picture covers an area 3 km (1.9 mi) wide by 10.8 km (6.7 mi) long; the context image is about 115 km (71 miles) on a side. The bright, wispy features in the context image are clouds, their dark shadows can be seen cast upon the surface to the right of each cloud feature.
Voir l'image PIA02802: Hot-Cross-Bun' on the Northern Plains sur le site de la NASA.
After several weeks of hiatus owing to problems with Mars Global Surveyor's High Gain Antenna (e.g., see JPL Release (April 16, 1999)) the Mars Orbiter Camera resumed operations during the final days of April 1999. Shown here is one of the first images returned after MOC began taking pictures again.
Warrego Valles is a system of discontinuous valleys located in the martian southern hemisphere south of Valles Marineris between Aonia Terra and Icaria Planum. This picture shows one of the small valleys in this system. The planet's surface both inside and outside the valley appears to be extremely rough. A person would find this terrain challenging to walk around in. The picture is illuminated from the upper left and covers an area 3 kilometers (1.9 miles) across.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
This set of 12 images was obtained during the period of Mars Orbiter Camera (MOC) focus tests and calibrations that executed in the first week of March 1999. Each picture was taken near 15.6°N latitude, which at this time was the sub-Earth point—the latitude at which Earth would be seen directly overhead if viewed from the ground. These pictures were obtained to provide a direct link between simultaneous Earth- and space-based telescope observations and the MOC. Each picture is shown at the full commanded resolution of 12 meters (39 feet) per pixel, and each covers an area 3 by 3 kilometers (1.9 miles) in size with illumination from the upper left. Typically, images that will be obtained by MOC during the Mapping Phase of the Mars Global Surveyor mission will have resolutions of 1.5 meters (5 feet) per pixel—a factor of 8 improvement over the pictures shown here.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01672: Mars Surfaces at 15.6°N Latitude, March 1999 sur le site de la NASA.
The Mars Orbiter Camera (MOC) was designed to be able to see objects the size of automobiles and small buildings on the martian surface. Of course, the Mars Global Surveyor science teams do not expect to find buildings and automobiles...but boulders, instead. These pictures show a typical MOC scene in the martian equatorial cratered highlands. The picture on the left (above) is a MOC wide angle context frame, showing the location of the high resolution image on the right. The high resolution image exhibits slopes and valleys that occur within an ancient impact crater that is about 33 kilometers (20.5 miles) across, located at 6.5°S, 218.8°W in the Aeolis region of Mars.
The high resolution view shows smooth, mantled surfaces, as well as bare, rocky surfaces. The bare surfaces are typically located on slopes. Small rounded knobs--particularly in the upper left corner of the image--are boulders. A few boulders have rolled down the slopes and are deposited in the valleys. The high resolution image covers a very small area--only 3 km wide by 4.2 km tall (1.9 miles by 2.6 miles). Both images were obtained at the same time, and both are illuminated by sunlight from the left. North is toward the upper right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
17 September 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a wind-eroded terrain. The ridges that cut across the scene from the lower right toward upper left (southeast to northwest) are classic yardangs, a landform created by wind erosion. These are located in the Eumenides Dorsum region of Mars.
Location near: 5.5°N, 159.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
Shortly after midnight Sunday morning (5 April 1998 12:39 AM PST), the Mars Orbiter Camera (MOC) on the Mars Global Surveyor (MGS) spacecraft successfully acquired a high resolution image of the "Face on Mars" feature in the Cydonia region. The image was transmitted to Earth on Sunday, and retrieved from the mission computer data base Monday morning (6 April 1998). The image was processed at the Malin Space Science Systems (MSSS) facility 9:15 AM and the raw image immediately transferred to the Jet Propulsion Laboratory (JPL) for release to the Internet. The images shown here were subsequently processed at MSSS.
The picture was acquired 375 seconds after the spacecraft's 220th close approach to Mars. At that time, the "Face," located at approximately 40.8° N, 9.6° W, was 275 miles (444 km) from the spacecraft. The "morning" sun was 25° above the horizon. The picture has a resolution of 14.1 feet (4.3 meters) per pixel, making it ten times higher resolution than the best previous image of the feature, which was taken by the Viking Mission in the mid-1970's. The full image covers an area 2.7 miles (4.4 km) wide and 25.7 miles (41.5 km) long. Processing Image processing has been applied to the images in order to improve the visibility of features. This processing included the following steps:
The image was processed to remove the sensitivity differences between adjacent picture elements (calibrated). This removes the vertical streaking.
The contrast and brightness of the image was adjusted, and "filters" were applied to enhance detail at several scales.
The image was then geometrically warped to meet the computed position information for a mercator-type map. This corrected for the left-right flip, and the non-vertical viewing angle (about 45° from vertical), but also introduced some vertical "elongation" of the image for the same reason Greenland looks larger than Africa on a mercator map of the Earth.
A section of the image, containing the "Face" and a couple of nearly impact craters and hills, was "cut" out of the full image and reproduced separately.
See PIA01440-1442 for additional processing steps. Also see PIA01236 for the raw image.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01441: Mars Orbiter Camera Views the "Face on Mars" - Calibrated, contrast enhanced, filtered, brightness-inverted sur le site de la NASA.
5 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dark-toned, cratered plain in southwest Utopia Planitia. Large, light-toned, windblown ripples reside on the floors of many of the depressions in the scene, including a long, linear, trough.
Location near: 30.3°N, 255.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
18 September 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the inverted remains of several channels in a fan-like complex in the Aeolis region of Mars. The inverted channels are the flat-topped ridges that trend from lower right toward upper left (southeast to northwest). Other ridges, trending from lower left toward upper right (southwest to northeast) are yardangs, the products of wind erosion. The channels were inverted by erosion, as well -- the tops of these ridges were once the floor of the channels (or the tops of materials that filled the channels).
Location near: 5.1°S, 205.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
The image shown here, MOC image 47903, was targeted on Friday afternoon (PDT), August 7, 1998. This picture of ejecta from a nameless 9.1 kilometer (5.7 mile)-diameter crater was designed to take full advantage of the present lighting conditions. When the image was taken (around 5:38 p.m. (PDT) on Saturday, August 8, 1998), the Sun had just risen and was only about 6° above the eastern horizon. With the Sun so low in the local sky, the contrast between sunlit and shadowed surfaces allowed new, subtle details to be revealed on the surface of the crater ejecta deposit.
The crater shown here has ejecta of a type that was first identified in Mariner 9 and Viking Orbiter images as "fluidized" ejecta. Ejecta is the material that is thrown out from the crater during the explosion that results when a meteor--piece of a comet or asteroid--collides with the planet. Fluidized ejecta is characterized by its lobate appearance, and sometimes by the presence of a ridge along the margin of the ejecta deposit. In the case of the crater shown here, there are two ridges that encircle the crater ejecta--this type of ejecta deposit is sometimes called a double-lobe rampart deposit. The MOC image shows that this particular crater also has "normal" ejecta that occurs out on the plains, beyond the outermost ridge of the main, fluidized ejecta deposit.
Fluidized or "rampart" ejecta deposits have long been thought by many Mars scientists to result from an impact into a surface that contains water. The water would have been underground, and could have been frozen or liquid. According to the prevailing model, when the meteor hit, this water was released--along with tons of rock and debris--and the ejecta flowed like mud. Images with resolutions higher than those presently attainable from the 11.6 hr elliptical orbit are needed to see the specific features (such as large boulders "rafted" by the dense mud) that would confirm or refute this model. Such images may be acquired once MGS is in its mapping orbit.
MOC image 47903 was received and processed by the MOC team at Malin Space Science Systems on Monday afternoon (PDT), August 10, 1998. The image center is located at 27.92°N latitude and 184.66°W longitude, in the northern Tartarus Montes region.
Voir l'image PIA01330: Fluidized Crater Ejecta Deposit sur le site de la NASA.
On June 14, 1998, Mars Global Surveyor's Mars Orbiter Camera revealed that part of the dark surface on the floor of Herschel Basin consists of a field of sand dunes ((B) above). These dunes have a distinct crescent-like shape characteristic of dunes on Earth called barchan dunes. They result from winds that blow from a single dominant direction.
In the case of Herschel Basin, the dunes indicate that the strongest winds blow approximately north-to-south. The crescent horns on the ends of some of the dunes in this image are elongated. This condition indicates that the dominant winds do not always blow in exactly the same direction-- sometimes the winds blow from the northeast, sometimes from the northwest, and sometimes from the north. The local topography probably influences the wind direction--and hence dune shape--because this dune field is located on a narrow, low plain between a high crater rim to the east, and a narrow mountain range-- the inner ring of the Herschel impact basin--to the west (see image (A)).
MOC image 36507 was obtained on Mars Global Surveyor's 365th orbit around 10:51 a.m. PDT on June 14, 1998. This subframe is centered around 14.27°S, 231.68°W.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01446: Windblown Dunes on the Floor of Herschel Impact Basin sur le site de la NASA.
The center image (available at higher resolution as PIA01028) shows the northern portion of the area inscribed in the left image. The right image (PIA01029) shows the southern portion.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01027: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris sur le site de la NASA.
Two views of Olympus Mons, shown as topography draped over a Viking image mosaic. MOLA's regional topography has shown that this volcano sits off to the west of the main Tharsis rise rather than on its western flank. The topography also clearly shows the relationship between the volcano's scarp and massive aureole deposit that was produced by flank collapse. The vertical exaggeration is 10:1.
Voir l'image PIA02805: Major Martian Volcanoes from MOLA - Olympus Mons sur le site de la NASA.
This dramatic image shows a field of dark sand dunes in the Nili Patera region of Syrtis Major. The shapes of these dunes indicate that wind has been steadily transporting the dark sand from the right/upper right toward the lower left. This picture was taken on the first day of the MGS Mapping Phase during the second week of March 1999. It shows an area 2.1 kilometers (1.3 miles) wide at the full commanded resolution of 3 meters per pixel. Illumination is from the upper left.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
The patterns created by dark spots on defrosting south polar dunes are often strange and beautiful. This picture, which the Mars Orbiter Camera team has dubbed, "the snow leopard," shows a dune field located at 61.5°S, 18.9°W, as it appeared on July 1, 1999. The spots are areas where dark sand has been exposed from beneath bright frost as the south polar winter cap begins to retreat. Many of the spots have a diffuse, bright ring around them this is thought to be fresh frost that was re-precipitated after being removed from the dark spot. The spots seen on defrosting polar dunes are a new phenomenon that was not observed by previous spacecraft missions to Mars. Thus, there is much about these features that remains unknown. For example, no one yet knows why the dunes become defrosted by forming small spots that grow and grow over time. No one knows for sure if the bright rings around the dark spots are actually composed of re-precipitated frost. And no one knows for sure why some dune show spots that appear to be "lined-up" (as they do in the picture shown here).
This Mars Global Surveyor Mars Orbiter Camera image is illuminated from the upper left. North is toward the upper right. The scale bar indicates a distance of 200 meters (656 feet).
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
The first clue that there might be places on Mars where liquid groundwater seeps out onto the surface came from a picture taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) during the pre-mapping Orbit Insertion Phase of the mission. The picture, shown in (A) above, was taken at the end of December 1997 while the spacecraft was still in the midst of aerobraking maneuvers to put it into the circular orbit needed for the Mapping Phase of the project. The Aerobraking 1 image, AB1-07707, showed dark, v-shaped scars on the western wall of a 50 kilometer-(31 mile)-diameter impact crater in southern Noachis Terra at 65°S, 15°W (see B, above, for context). The v-shaped features taper downslope to form narrow, somewhat curved channels. The relationship seen here was interpreted by MOC scientists to be similar to seepage landforms on Earth that form where springs emerge on a slope and water runs downhill.
Once MGS achieved its Mapping Orbit in March 1999, the MOC was in a better position to take pictures of 10 times higher resolution than the Aerobraking AB1-07707 image. The opportunity to take a new picture of the proposed "seepage" sites on the wall of the crater in southern Noachis finally arose in January 2000. The result is MOC image M11-00530, shown above in (top) and (C). This new close-up shows that the darkly-shaped scars host many small channels of only a few meters (yards) across. These small channels run downslope and coalesce at the apex (or point) of each "v." Amid the small channels are many large boulders, some of them the size of houses, that have eroded out of the crater wall. A 3-D view created using the AB1 and M11 images is shown in (D). The stereo picture (red-blue "3D" glasses required) emphasizes the presence of small channels and valleys, and shows that these valleys start almost at the very top of the v-shaped dark areas.
The context picture in (B) is a mosaic of Viking 2 orbiter images 497B47 and 497B48 acquired December 28, 1977. The Aerobraking MGS MOC image, AB1-07707, is shown overlain on the Viking context image; it was taken 20 years later on December 29, 1997. The smaller white box in the context picture shows the location of MOC Mapping Phase image M11-00530, roughly 2 years later on January 4, 2000. North is "up" in pictures (A) and (B), and to the lower right in (top), (C), and (D). Sunlight illuminates (A) from the upper left, (B) from the upper right, and (top) and (C) from the upper right. The top image in (top) is the aerobraking image, AB1-07707, with a white box indicating the location of the lower image, M11-00530, and the stereo pair in (D). The white box on the left in (C) shows the location of the close-up on the right in (C).
Voir l'image PIA01036: Evidence for Recent Liquid Water on Mars: Seepage Sites in "Aerobraking Crater" Revisited sur le site de la NASA.
Release image with labels
Context Image
The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has found that only two ancient martian valleys contain evidence for sustained fluid flow. The first was Nanedi Valles--this finding was announced back in February 1998 (See: Nanedi Vallis: Sustained Water Flow?). When this picture was obtained in September 1999, Nirgal Vallis joined the lonely list with Nanedi Valles. But Nirgal is different--it also contains evidence for much more recent fluid seepage from its walls!
The context view on the right--a mosaic of Viking orbiter views from the U.S. Geological Survey--shows the location (white box) of the high resolution MOC view on the left. The MOC image shows two channels running through the center of Nirgal Vallis--a wide, outer channel with a narrow, leveed "inner channel" running down its center. Leveed refers to the fact that the inner channel's walls appear to be raised above the surrounding terrain, like a levee that might be used to protect property from floods on the Mississippi River. Levees can form naturally from running water or lava... it is not clear which fluid--lava or water--was involved in Nirgal Vallis.
The wall of Nirgal Vallis shows something else--a much more recent "gully" with an alcove at the top of the slope, a channel, and an apron that partly covers some of the adjacent sand dunes. This gully is inferred to be much younger than the channels running down the center of Nirgal Vallis, because these channels are covered by dunes, while the gully's apron covers the dunes. This gully feature is one of many reported by MGS MOC scientists in June 2000 as being the possible result of geologically recent groundwater seepage and mud or debris flow. (See: MOC Images Suggest Recent Sources of Liquid Water on Mars).
The image is located near 29.4°S, 39.1°W. North is toward the upper right and illumination is from the upper left. Aspect ratio is 1.5:1, thus the scale bar in the labeled image (middle) shows different vertical and horizontal scales. The picture covers an area 3 km (1.9 mi) by 6.5 km (4 mi) and is a subframe of M07-00752. To see what the raw MOC image data look like, visit the newest data releases (for Mission Subphases M07 - M12, covering September 1999 through February 2000) in the MOC GALLERY.
Voir l'image PIA02814: Channels and Gullies in Nirgal Vallis--The Work of Water? sur le site de la NASA.
During the year spent waiting to achieve the planned circular, polar Mapping Orbit, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) took about 1170pictures that had resolutions in the 2 to 20 meters (7-66 feet) per pixel range. These pictures were obtained between September 1997 and September 1998, and are now archived with NASA and available to the public at NASAPDS--http://ida.wr.usgs.gov/. Although these pictures were generally a vast improvement in spatial resolution compared to the previous images from Viking and Mariner, the latest pictures from MOC--taken this month (April 1999) from the proper Mapping Orbit--demonstrate the power of the MOC when in focus and operating at the correct altitude (~380 km or 235 miles).
The Viking Orbiter picture on the left, above, shows the 83 kilometers-(52 miles)-wide crater, Escalante. Located on the martian equator at 245°W longitude, a portion of this crater's floor was seen by MOC before the mapping mission began, at a resolution of 9.4 meters (31 feet) per pixel as shown in the middle image. The new picture--on the right--peers down into one of the pits seen in the earlier MOC image--only now it is viewed at 1.8 meters (6 feet) per pixel.
The new high resolution image (right) covers an area only 1.5 kilometers (0.9 miles)wide and shows that the crater floor--which appears relatively smooth in the context view on the left--is actually quite rough at the scale that a human being would notice if trying to hike around in this landscape. The latest picture also shows small, bright windblown dunes that were not visible in the earlier MOC image.
MOC2-120a is a mosaic of Viking Orbiter images 381s62 and 379s47, and MOC2-120b is a subframe of MGS MOC image SPO-2-382/04. The large white box shows the location of MOC2-120b, and the small white box shows the location of MOC2-120c. In MOC2-120a and MOC2-120b, illumination is from the right/upper right, in MOC2-120c it is from the left.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
When it was proposed to NASA in 1985, one of the goals of the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) experiment was to take pictures with high enough resolution to be able to see large boulders on the planet's surface. For large martian outflow channels--believed by some to have been carved by giant floods several billion years ago--seeing boulders and measuring their size and distribution in the channels can tell geologists something about the nature of the flood--for example, how fast the water was moving, and, in some cases, how deep it was.
But Mars doesn't always cooperate.
The white box in the context image on the right shows the location of the high resolution MOC image on the left. The white box in the context frame is located among buttes and mesas within Mangala Valles, one of the large martian channels thought to have been carved by floods long ago. The high resolution view, however, offers no insight into the processes that formed Mangala Valles. Instead, the entire surface--mesa tops, buttes, and channel floor--are all covered-up with a thick blanket of wind-eroded, ridged and grooved material. Some of the buttes and mesas have boulders on their surfaces, and wind has hollowed-out circular depressions around these boulders. But the boulders in this case probably have nothing to do with the floods that might have formed Mangala Valles--they are boulders exposed in the bedrock contained beneath the ridged and grooved mantle that covers each butte and mesa. The dark streaks on slopes in this image are places where dry accumulations of dust have slid downhill, much like a snow avalanche. Similar streaks have been seen elsewhere on the dusty surfaces of Mars, and some have been found to change over time. For example, see Recent Movements: New Landslides in Less than 1 Martian year.
This picture is located near 8.7°S, 151.2°W; it covers an area 3 km (1.9 mi) by 11.7 km (7.3 mi). North is toward the upper right, and illumination is from the upper left. This is a subframe of MOC image M11-01809, acquired January 13, 2000. To see what the raw MOC image data look like, visit the newest data releases (for Mission Subphases M07 - M12, covering September 1999 through February 2000) in the MOC GALLERY.
Voir l'image PIA02813: Groovy Terrain in Mangala Valles sur le site de la NASA.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01508: Small Valley Network Near Schiaparelli Crater sur le site de la NASA.
Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01169: Nanedi Vallis: Sustained Water FLow? sur le site de la NASA.
Many aspects of our studies of Mars from Earth are dictated by the different rates at which the two planets orbit the Sun. This difference allows Earth to pass Mars in its orbit, continue to lead Mars around the Sun, and then eventually overtake Mars again, every 26 months. This cycle governs opportunities to send rockets to Mars when the closest approaches between the two planets occur (opposition). The cycle also dictates when Mars will pass behind the Sun relative to Earth (conjunction). A Solar Conjunction period has just ended. During this time radio communications from the Mars Global Surveyor spacecraft, operating at Mars, were interrupted for a few weeks. Because it would not be able to send pictures back to Earth during this time, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) was turned off on June 21, 2000, and turned back on again July 13, 2000. The two pictures shown here are among the very first high resolution views of the martian surface that were received following the resumed operation of the MOC. Both pictures arrived on Earth via radio downlink on Saturday, July 15, 2000.
The first picture (above left) shows a ridged and cratered plain in southern Hesperia Planum around 32.8°S, 243.2°W. The second image (above right) shows the layered northeastern wall of a meteor impact crater in Noachis Terra at 32.9°S, 357.6°W. Both pictures cover an area 3 kilometers (1.9 miles) wide at a resolution of 6 meters per pixel. Both are illuminated by sunlight from the upper left.
Voir l'image PIA01043: MGS MOC Returns to Service Following Solar Conjunction Hiatus sur le site de la NASA.
Click for full-resolution image.
Click for full-resolution image.
Click for full-resolution image.
As we head into the 21st Century, it seems hard to believe that human beings have been sending spacecraft toward Mars for more than 3 decades already. The first spacecraft to reach Mars was Mariner 4 in 1965. This success was followed by two spacecraft in 1969, Mariners 6 and 7. Now the wonders and alien beauty of Mars continue to unfold with each day that the Mars Global Surveyor--which arrived in September 1997--continues to radio its data to Earth.
Mars exploration was always difficult and each bit of data returned from the planet is a marvel. On August 5, 1969, the Mariner 7 spacecraft flew past Mars at a minimum altitude of about 4200 km. It acquired 14 wide/narrow angle image pairs during the few minutes of the "near encounter" flyby. One of these image pairs, 7N19/7N20, shows the south polar region and contains a feature that at the time was nicknamed "the Giant's Footprint." Shown in the first two pictures, above, the feature consists of two adjoining craters, one about 80 km (50 mi) in diameter and the other about 50 km (31 mi) across near latitude 76°S, longitude 276°W. The oblique geometry of the Mariner 7 image enhances the impression of a footprint.
The "Giant's Footprint" was almost missed when Mariner 7 suffered a near-catastrophic battery failure just a few days before the encounter--on July 30--that put the spacecraft sporadically out of contact with Earth for two days. Ground controllers at the Jet Propulsion Laboratory (JPL)recovered the spacecraft, re-planned its imaging sequence based on results from the Mariner 6 flyby on July 31, and salvaged all of the mission's science goals in under a week!
In the 1970's, the larger crater in "giant's footprint" was named "Vishniac" in honor of Wolf Vishniac, an American microbiologist of the University of Rochester who was instrumental in the development of methods to search for life on Mars. Vishniac was tragically killed in a fall in Antarctica in 1973 while retrieving a life detection experiment, and the crater was named in honor of this "giant" in the search for life on Mars.
More than three decades after the Mariner 7 flyby, Mars Global Surveyor's Mars Orbiter Camera (MOC) acquired a commemorative view of the interior of Vishniac Crater on October 25, 1999. The context image and the 3-meters (9.8 feet)-per-pixel narrow angle view are shown above (in the lower image pair). Mariner 7's 7N20 has a nominal resolution of about 180 meters (591 feet) per pixel, while the MOC high resolution view is about 60 times higher (in actuality, the lower quality of the Mariner 7 images makes the resolution gain even more dramatic).
The MOC high resolution view (lower right, above) shows a 1.5 kilometer-(0.9 mile)-wide portion of the floor of Vishniac in the process of defrosting during southern spring. The bright areas are still frost-covered, while the darker areas are either defrosted or composed of darkened or "dirty" frost. The dark patches in the image seem to serve as sources for dark streaks of material that has either been blown across the landscape by wind, or has somehow caused the erosion of frost to create the streaks. Dark streaks follow the local topography, as might the wind that blew across this landscape. This pattern of spots and streaks was quite common on the defrosting south polar cap during the spring that lasted from early August 1999 to late December 1999.
All images shown here are illuminated by sunlight from the lower right. Image orientation with north toward the bottom was selected in order to show the "footprint" visible in Mariner 7 image 7N20. The Mariner 7 images were recovered at Malin Space Science Systems from the original 7-track magnetic tapes, archived on CD-ROM by the JPL Data Preservation activity.
Voir l'image PIA02365: Return to "Giant's Footprint" 3 Decades After Mariner 7 Flyby sur le site de la NASA.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01506: Channels on Bakhuysen Crater Wall sur le site de la NASA.
Someone's kitchen floor? A stone patio?This picture actually does show a floor--the floor of an old impact crater on the northern plains of Mars. Each "tile" is somewhat larger than a football field. Polygonal patterns are familiar to Mars geologists because they are also common in arctic and antarctic environments on Earth. Typically, such polygons result from the stresses induced in frozen ground by the freeze-thaw cycles of subsurface ice. This picture was taken by MOC in May 1999 and is illuminated from the lower left.
This high resolution picture (right) of the Martian surface was obtained in the early evening of January 1, 1998 by the Mars Orbiter Camera (MOC), shortly after the Mars Global Surveyor spacecraft began it's 80th orbit. Seen in this view are a plateau and surrounding steep slopes within the Valles Marineris, the large system of canyons that stretches 4000 km (2500 mi) along the equator of Mars. The image covers a tiny fraction of the canyons at very high resolution: it extends only 9.8 km by 17.3 km (6.1 mi by 10.7 mi) but captures features as small as 6 m (20 ft) across. The highest terrain in the image is the relatively smooth plateau near the center. Slopes descend to the north and south (upper and lower part of image, respectively) in broad, debris-filled gullies with intervening rocky spurs. Multiple rock layers, varying from a few to a few tens of meters thick, are visible in the steep slopes on the spurs and gullies. Layered rocks on Earth form from sedimentary processes (such as those that formed the layered rocks now seen in Arizona's Grand Canyon) and volcanic processes (such as layering seen in the Waimea Canyon on the island of Kauai). Both origins are possible for the Martian layered rocks seen in this image. In either case, the total thickness of the layered rocks seen in this image implies a complex and extremely active early history for geologic processes on Mars.
The left and center "context" images are Viking mosaics reproduced at scales of 230 meters/pixel and 80 meters/pixel respectively. Outlines in these two images represent the location of the higher resolution image(s).
Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01167: Layers within the Valles Marineris: Clues to the Ancient Crust of Mars sur le site de la NASA.
(B) Sinus Sabaeus, dark mantle with cracks.
(D) Ganges Chasma 3-D Context.
When seen through a telescope from Earth, Mars reveals a pattern of bright and dark regions. Early astronomers speculated that the dark regions were seas. Later astronomers suggested that the dark regions were vast tracts of vegetation. As recently as the early 1960s, it still seemed possible to a few astronomers that the dark regions had some kind of plant life because they seemed to darken each summer as if plants were growing in response to sunlight.
Since the Mariner missions to Mars (1965-1972), purely geological explanations have been proposed to explain the dark regions and the changes we see in them. In particular, dust storms have been observed on Mars. Thus wind and dust storms are the suspected culprits that created the 19th Century illusion that something was growing and changing with each martian season. Just as there are "hurricane seasons" and "monsoon seasons" on Earth, there may be "dust storm seasons" on Mars.
The dark regions of Mars are now being seen in greater detail than ever before by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC). As expected, none of these areas are covered by vegetation! But what has been a surprise is the great variety of dark surfaces seen. Before MGS, most had been thinking that these areas are sandy because all of the large martian sand dunes are dark, too. But in many cases, dark dunes and sand are not found in the MOC images--such areas instead are thickly blanketed by a cracked, crusty covering of what may be fine silt instead of sand. Other areas--in particular the floor of Ganges Chasma in the Valles Marineris region--show thick accumulations of windblown sand.
The first two pictures presented here (A and B, above) show dark, blanketed or mantled surfaces in the Sinus Sabaeus region (310°-350° W longitude and 5°-12°S latitude) of Mars. This dark material in some places has bright dunes on top of it (top, left picture), and in other places appears to have narrow cracks running through it (top, right picture). If the dark material consisted of sand, it would show drifts and tails formed around and behind obstacles as are seen in the thick sand sheets of Ganges Chasma (C and D, above). Because wind transports sand close to the ground, it interacts with obstacles such as the bright mounds in Figure C (above) to make drifts and tails.
The top left picture is MOC image AB1-11105 located in Sinus Sabaeus near 7.0°S, 343.4°W. The top right picture is also in Sinus Sabaeus and is MOC image M00-01078 near 10.0°S, 329.1°W. The bottom left pair of images show a thick sheet of dark sand in Ganges Chasma. The bottom right picture is a stereo anaglyph (use 3-d red/blue glasses) MOC wide angle view showing the locations of the two Ganges Chasma images. Ganges Chasma is around 7°S, 50°W. All pictures are illuminated from the left. The AB1 images were taken in January 1998, the M00 images are from April 1999.
Voir l'image PIA02362: The Dark Surfaces of Mars: Mantles and Sand Sheets sur le site de la NASA.
MOC image 38804 (above) shows a portion of Marte Vallis. Marte Vallis has been thought by some to have been carved by a giant water flood. However, the picture shown here does not have any flood features. If there ever was a water flood, all of the evidence in this particular location (at 7.1°N latitude and 182.7°W longitude; CLICK HERE for a context image) has been covered-up by a vast lava flow. When it was forming, the lava flowed from the lower left, toward the center right, then curved to the left and flowed toward the top-center of the frame.
The center of the lava flow in image 38804 has a wide, shallow channel bounded by steep, discontinuous walls--also known as levees. Such leveed channels are commonly the conduit through which some of the later stages of molten rock are transported along a lava flow. The margins of the lava flow are broken into plates--some of them several kilometers across. These plates were once part of a hard, rock crust that floated on molten lava. As the lava flowed down Marte Vallis, huge chunks of this crust broke off at the margins of the flow and floated a few kilometers away from where they had originated. Long after the lava had cooled and hardened, a distant meteorite impact splashed ejecta across the martian surface such that a field of small craters--known as secondary craters--formed on top of the lava flow shown here.
MOC image 38804 was taken on June 25, 1998. This subframe shows an area 15.8 km by 45.8 km (9.8 miles by 28.5 miles) in size. The image here has a resolution of about 31 meters (101 feet) per pixel. North is approximately up, illumination is from the right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01501: Mars Volcanism: Large, Fluid Lava Flows sur le site de la NASA.
Valley floors in the middle latitudes, particularly in the "fretted terrain" of northern Arabia Terra (shown here) have curious grooved and pitted surfaces. These features not glaciers and show very little evidence (if any) of flow. Their origin is unknown. MOC image from July 1998.
The image was taken on October 30, 1997 at 11:05 AM PST, shortly after the Mars Global Surveyor spacecraft's 31st closest approach to Mars. The image covers an area 3.6 X 21.5 km (2.2 X 13.4 miles) at 3.6 m (12 feet) per picture element--craters only 11 m (36 feet, about the size of a swimming pool) across can be seen. The best Viking view of the area (VO 1 387S34) has a resolution of 240 m/pixel, or 67 times lower resolution than the MOC frame.
Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01160: Medusae Fossae Formation - High Resolution Image sur le site de la NASA.
Valles Marineris was first observed in 1972 by the Mariner 9 spacecraft, from which the troughs get their name: Valles--valleys, Marineris--Mariner.
Some hints of layering in both the canyon walls and within some deposits on the canyon floors were seen in Mariner 9 and Viking orbiter images from the 1970s. The Mars Orbiter Camera on board Mars Global Surveyor has been examining these layers at much higher resolution than was available previously.
MOC images led to the realization that there are layers in the walls that go down to great depths. An example of the wall rock layers can be seen in MOC image 8403, shown above (C).
MOC images also reveal amazing layered outcrops on the floors of some of the Valles Marineris canyons. Particularly noteworthy is MOC image 23304 (D, above), which shows extensive, horizontally-bedded layers exposed in buttes and mesas on the floor of western Candor Chasma. These layered rocks might be the same material as is exposed in the chasm walls (as in 8403--C, above), or they might be rocks that formed by deposition (from water, wind, and/or volcanism) long after Candor Chasma opened up.
In addition to layered materials in the walls and on the floors of the Valles Marineris system, MOC images are helping to refine our classification of geologic features that occur within the canyons. For example, MOC image 25205 (E, above), shows the southern tip of a massive, tongue-shaped massif (a mountainous ridge) that was previously identified as a layered deposit. However, this MOC image does not show layering. The material has been sculpted by wind and mass-wasting--downslope movement of debris--but no obvious layers were exposed by these processes.
Valles Marineris a fascinating region on Mars that holds much potential to reveal information about the early history and evolution of the red planet. The MOC Science Team is continuing to examine the wealth of new data and planning for new Valles Marineris targets once the Mapping Phase of the Mars Global Surveyor mission commences in March 1999.
Layers exposed near the middle of western Candor Chasma. MOC image 23304 subframe shown at 10.7 meters (35 feet) per pixel. Two layered buttes (upper right and lower right) and a layered or stepped mesa (center right) are shown. The image covers an area approximately 5.5 by 5.5 kilometers (3.4 x 3.4 miles). North is approximately up, illumination is from the lower right. Image 23304 was obtained during Mars Global Surveyor's 233rd orbit at 9:23 a.m. (PDT) on April 11, 1998.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01459: Western Candor Chasma - Layers exposed near the middle sur le site de la NASA.
This suite of Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) pictures provides a vista of martian gullies on the northern wall of a 12 kilometer-(7.4 mile)-wide meteor impact crater east of the Gorgonum Chaos region on the red planet.
The first picture (above left) is a composite of three different high resolution MOC views obtained in 1999 and 2000. The second picture (above right)shows the location of the high resolution views relative to the whole crater as it appeared in the highest resolution image previously acquired of the area, taken by the Viking 1 orbiter in 1978. The release image (top) shows a close-up of one of the channels and debris aprons found in the northwestern quarter of the impact crater.
Some of the channels in this crater are deeply-entrenched and cut into lighter-toned deposits. The numerous channels and apron deposits indicate that many tens to hundreds of individual events involving the flow of water and debris have occurred here. The channels and aprons have very crisp, sharp relief and there are no small meteor impact craters on them, suggesting that these features are extremely young relative to the 4.5 billion year history of Mars. It is possible that these landforms are still being created by water seeping from the layered rock in the crater wall today.
The crater has no name and it is located near 37.4°S, 168.0°W. The composite view in (above left) includes a picture taken by MOC on September 10, 1999, a picture obtained April 26, 2000, and another on May 22, 2000. The scene from left to right (including the dark gap between photos) covers an area approximately 7.6 kilometers (4.7 miles) wide by 18 km (11.1 mi) long. Sunlight illuminates the scene from the upper left. MOC high resolution images are taken black-and-white (grayscale); the color seen here has been synthesized from the colors of Mars observed by the MOC wide angle cameras and by the Viking Orbiters in the late 1970s.
Voir l'image PIA01038: Evidence for Recent Liquid Water on Mars: Channels and Aprons in East Gorgonum Crater sur le site de la NASA.
19 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a partially-buried crater in the north polar region of Mars. The circular feature is surrounded and partly overlain by some of the many, many sand dunes in the area. The steepest slopes on each dune -- their slip faces -- face toward the southeast (lower right), indicating that the dominant winds responsible for sand transport in this region come from the northwest (upper left). In summer, the dunes in this scene would be darker than their surroundings, but in this northern springtime image, the dunes and everything else in the area are covered by carbon dioxide frost. The frost is left over from the winter which ended in January 2006.
Location near: 76.0°N, 82.2°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Spring
1 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of gullies on a scarp in Lyell Crater.
Location near: 69.7°S, 14.0°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
Many aspects of our studies of Mars from Earth are dictated by the different rates at which the two planets orbit the Sun. This difference allows Earth to pass Mars in its orbit, continue to lead Mars around the Sun, and then eventually overtake Mars again, every 26 months. This cycle governs opportunities to send rockets to Mars when the closest approaches between the two planets occur (opposition). The cycle also dictates when Mars will pass behind the Sun relative to Earth (conjunction). A Solar Conjunction period has just ended. During this time radio communications from the Mars Global Surveyor spacecraft, operating at Mars, were interrupted for a few weeks. Because it would not be able to send pictures back to Earth during this time, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) was turned off on June 21, 2000, and turned back on again July 13, 2000. The two pictures shown here are among the very first high resolution views of the martian surface that were received following the resumed operation of the MOC. Both pictures arrived on Earth via radio downlink on Saturday, July 15, 2000.
The first picture (above left) shows a ridged and cratered plain in southern Hesperia Planum around 32.8°S, 243.2°W. The second image (above right) shows the layered northeastern wall of a meteor impact crater in Noachis Terra at 32.9°S, 357.6°W. Both pictures cover an area 3 kilometers (1.9 miles) wide at a resolution of 6 meters per pixel. Both are illuminated by sunlight from the upper left.
Voir l'image PIA01044: MGS MOC Returns to Service Following Solar Conjunction Hiatus sur le site de la NASA.
The above figure shows the location of all high resolution (narrow angle) MOC images of the Cydonia region that have been obtained to date, including the first three taken in 1998 (PIA01240, PIA01241, AND PIA01440). These images are superimposed upon a mosaic of Viking images taken during the 1970's. Images acquired during the Science Phasing Orbit period of 1998 slant from bottom left to top right; Mapping Phase images (from 1999 and 2000) slant from lower right to upper left. Owing to the nature of the orbit, and in particular to the limitations on controlling the location of the orbit, the longitudinal distribution of images (left/right in the images above) is distinctly non-uniform. An attempt to take a picture of a portion of the "Face" itself in mid-February 2000 was foiled when the MGS spacecraft experienced a sequencing error and most of that day's data were not returned to Earth. Only the first 97 lines were received; the image's planned footprint is shown as a dashed box. This image is one in a series of eight.
Voir l'image PIA02386: Cydonia: Two Years Later sur le site de la NASA.
Not all sand dunes on Mars are active in the modern martian environment. This example from the Lycus Sulci (Olympus Mons"aureole") region shows a case where small windblown dunes at the base of a slope have been over-ridden by more recent dark streaks (arrows). The dark streaks are most likely caused by what geologists call mass wasting or mass movement (landslides and avalanches are mass movements). Dark slope streaks such as these are common in dustier regions of Mars, and they appear to result from movement of extremely dry dust or sand in an almost fluidlike manner down a slope. This movement disrupts the bright dust coating on the surface and thus appears darker than the surrounding terrain.
In this case, the dark slope streaks have moved up and over the dunes at the bottom of the slope, indicating that the process that moves sediment down the slope is more active (that is, it has occurred more recently and hence is more likely to occur) in the modern environment than is the movement of dunes and ripples at this location on Mars. The dunes, in fact, are probably mantled by dust. This October 1997 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture is illuminated from the left and located near 31.6°N, 134.0°W.
Voir l'image PIA02357: Dark Streaks Over-riding Inactive Dunes sur le site de la NASA.
The Mars Orbiter Camera (MOC) on board the Mars Global Surveyor (MGS) spacecraft has been documenting a variety of landforms in the volcanic Tharsis region, including these valleys and associated lava flows on the plains southeast of Olympus Mons. Lava flows are visible in the upper left quarter of this image, but meandering valleys with streamlined "islands" dominate the scene. The valleys might have been carved by running water, but extremely fluid lava or mud might also have flowed through the channels. The exact role of each type of fluid--water, mud, or lava--remains to be determined. Illumination is from the right. The area shown is 7.3 km (4.5 mi) wide by 12 km (7.5 mi) long.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01689: Valleys and Lava Flows near Olympus Mons sur le site de la NASA.
The seasons on Mars and Earth are anti-correlated at present: days are getting shorter and shadows are getting longer as autumn end sand the beginning of winter draws nearer in the martian southern hemisphere, just as the same is occurring in Earth's northern hemisphere. Long shadows are especially prominent in this high resolution view of mountains forming part of the central peaks of Hale Crater (left), a 136 kilometer-(85 mile)-diameter impact crater at 36°S, 37°W. The two pictures were taken simultaneously by the Mars Global Surveyor Mars Orbiter Camera on November 10, 2000. The sun illuminates the scene from the northwest (upper left) about 22° above the horizon. Knowing the sun angle and the length of the longest shadow (~1.6 km; ~1.0 mi), the height of the largest peak in the high resolution view (right) is about 630 meters (~2,070 ft) above the crater floor. Sand dunes blanket the middle portion of the high resolution view, and small gullies--possibly carved by water--can be seen on the slopes of some of the peaks at the upper left. Winter in the southern hemisphere will begin in mid-December 2000. The high resolution view covers an area 3 km (1.9 mi) wide at a full-resolution scale of 3 meters (9.8 ft) per pixel.
Voir l'image PIA02828: Autumn Afternoon in Hale Crater sur le site de la NASA.
5 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a channel extending northward from the Elysium Mons caldera at the volcano's summit. The north wall of the caldera -- the summit depression formed by collapse as magma withdraws‚ is located at the south end (bottom) of this picture.
Location near: 24.8°N, 213.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
Big sand dunes! Mars is home to some very large, windblown dunes. The dunes shown here rise to almost 100 meters (275 feet) at their crests. Unlike dunes on Earth, the larger dunes of Mars are composed of dark, rather than light grains. This is probably related to the composition of the sand, since different materials will have different brightnesses. For example, beaches on the island of Oahu in Hawaii are light colored because they consist of ground-up particles of seashells, while beaches in the southern shores of the island of Hawaii (the "Big Island" in the Hawaiian island chain) are dark because they consist of sand derived from dark lava rock.
The dunes in this picture taken by the Mars Orbiter Camera (MOC) are located on the floor of an old, 72 km-(45 mi)-diameter crater located northeast of Syrtis Major. The sand is being blown from the upper right toward the lower left. The surface that the dunes have been travelling across is pitted and cratered. The substrate is also hard and bright--i.e., it is composed of a material of different composition than the sand in the dunes. The dark streaks on the dune surfaces area puzzle...at first glance one might conclude they are the result of holiday visitors with off-road vehicles. However, the streaks more likely result from passing dust devils or wind gusts that disturb the sand surface just enough to leave a streak. The image shown here covers an area approximately 2.6 km (1.6 mi) wide, and is illuminated from the lower right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
As many people on Earth celebrated the dawn of a new year, a new century, and a new millennium, the Mars Global Surveyor(MGS) Mars Orbiter Camera (MOC) continued its journey that began with a proposal to NASA nearly 15 years earlier in 1985. As the clock rolled over to 2000 A.D., MOC was busily snapping its daily global weather maps and a variety of higher-resolution images such as the two shown here.
On December 25, 1999, Mars passed its northern hemisphere winter solstice, marking the beginning of northern winter (and summer in the southern hemisphere). The pictures shown here are from the northern hemisphere among the mesas and buttes of the Nilosyrtis Mensae. This region, if it were on Earth, would be located in western Afghanistan around 33° N latitude, 63° E longitude (297°W on Mars). The picture was one of the first high resolution views of Mars taken by the MGS MOC on January 1, 2000, at 06:42 UTC (6 hours, 42 minutes after the new year began in the Greenwich Time Zone).
The picture on the left is a context frame that covers an area 115 km (71 mi) across. The white box shows the location of the new millennium Mars image, which also appears on the right. This high resolution view shows a wide variety of surface textures caused mainly by unknown, possibly uniquely "martian" geologic processes. The view also includes small, bright, windblown drifts. The high resolution view covers an area 3 km across at a resolution of 4.5 meters (15 feet) per pixel. The sun illuminates both scenes from the lower left.
The MGS MOC began taking pictures from Mars orbit in September 1997. It's primary mission will last through January 2001. After that, an extended mission might be approved by NASA--this would allow the camera to continue its activities well into 2002 or beyond.
Voir l'image PIA02350: 01 January 2000 On The Red Planet sur le site de la NASA.
The circular, polar orbit of Mars Global Surveyor (MGS) achieved in early 1999 has begun to provide many opportunities to examine features in the martian southern hemisphere at high resolution. One of our favorite examples (thus far) is this picture of a small portion of the floor of Alexey Tolstoy Crater.
The top of the image shows a dark surface that is extremely rough and rocky. The rest of the image shows a brighter, smoother material. It appears that the bright material has been eroded back, exposing the lower, darker surface. The small crater that dominates this picture is only about 850 meters (930 yards) wide and has also been partly exhumed/exposed from beneath the bright, smooth material. Illumination is from the upper left.
Alexey (or Aleksey) Tolstoy Crater, in which the small unnamed crater seen in this picture occurs, was named by the International Astronomical Union in 1982 to honor the Soviet writer who died in 1945. It is one of only a few craters on Mars designated by both the first and last names of the honored person. The Alexey Tolstoy Crater has a diameter of 94 kilometers (58 miles) and is centered at 47.6°S latitude, 234.6°W longitude in eastern Promethei Terra.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
10 October 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of dunes in one of the several north polar dune fields. The bright surfaces adjacent to some of the dunes are patches of frost. These dunes spend much of the autumn, winter, and spring seasons covered with carbon dioxide frost. Only in late spring and in summer are the dark windblown sands fully exposed.
Over the course of the 9+ years of the MGS mission, the MOC team has sought evidence that sand dunes may be migrating downwind over time. However, no clear examples of the movement of a whole dune have been identified. On Earth, such movement is typically detectable in air photos of the smallest active dunes over periods of a few years. Owing to the fact that the north polar dunes spend much of each martian year under a cover of frost, perhaps these move much more slowly than their frost-free, terrestrial counterparts. The sand may also be somewhat cemented by ice or minerals, likewise preventing vigorous dune migration in the present environment.
This view covers an area approximately 3 km (1.9 mi) wide and is illuminated by sunlight from the lower left. The dunes are located near 79.8°N, 127.1°W, and the picture was acquired on 11 September 2006.
Figure caption from Science Magazine
Voir l'image PIA00805: Crommelin Crater #2 sur le site de la NASA.
Orbit: 220
Range: 444.21 km
Resolution: 4.32 m/pixel
Emission angle: 44.66 degrees
Incidence angle: 64.96 degrees
Phase angle: 61.97 degrees
Scan rate: ~0.1 degree/sec
Start time: periapsis + 375 sec
Sequence submitted to JPL: Sat 04/04/98 15:15 PST
Image acquired by MOC: Sun 04/05/98 00:39:37 PST
Data retrieved from JPL: Mon 04/06/98 09:05 PDT
Voir l'image PIA01237: Cydonia Region - detail sur le site de la NASA.
The above figure shows the location of all high resolution (narrow angle) MOC images of the Cydonia region that have been obtained to date, including the first three taken in 1998 (PIA01240, PIA01241, AND PIA01440). These images are superimposed upon a mosaic of Viking images taken during the 1970's. Images acquired during the Science Phasing Orbit period of 1998 slant from bottom left to top right; Mapping Phase images (from 1999 and 2000) slant from lower right to upper left. Owing to the nature of the orbit, and in particular to the limitations on controlling the location of the orbit, the longitudinal distribution of images (left/right in the images above) is distinctly non-uniform. An attempt to take a picture of a portion of the "Face" itself in mid-February 2000 was foiled when the MGS spacecraft experienced a sequencing error and most of that day's data were not returned to Earth. Only the first 97 lines were received; the image's planned footprint is shown as a dashed box. This image is one in a series of eight.
Voir l'image PIA02388: Cydonia: Two Years Later sur le site de la NASA.
A pair of Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images (above, center and right) shows close-up views of a sand dune field that was first detected by the Viking orbiters in the late 1970s (above, left). What is surprising about the MOC images is that they reveal a dune field unlike any other thus far seen on Mars--this one has impact craters on its surface, and LOTS of them!
The field of parallel ridges north of the dune field (above the white boxes in picture at the left) is a wind-eroded material named the Apollinaris Sulci. It is possible that the dune field shown here was once covered by this wind-eroded material and was later exhumed. Regardless, the dunes were somehow hardened and have been exposed as hard rock on the martian surface long enough for many impact craters smaller than a few hundred meters (few hundred yards) across to form. These dunes are therefore quite ancient--one might say that this is a "fossil" dune field. A similar effect at a much smaller scale can be seen by examining some sandstones and siltstones on Earth--if conditions were right, ripples formed in either water or wind are preserved in such rocks.
The first MOC view, labeled M03-00006, was taken on July 1, 1999. The second view, M07-05007, was acquired September 26,1999. Both MOC images and the Viking picture are illuminated from the left. The dune field occurs east of the Apollinaris Patera volcano and northeast of Gusev Crater at 12.5°S, 181°W.
The release for image C in the caption can be found here.
Voir l'image PIA02359: Ancient Paleo-Dunes Battered by Impact Craters sur le site de la NASA.
8 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows two circular features in the south polar region of Mars. The circular features are degraded impact craters. The dark, irregular features in each crater are the remnants of a layer of material that probably once covered the entire scene, before being eroded away. All of the terrain in this image is covered by defrosting, seasonal carbon dioxide frost.
Location near: 79.5°S, 295.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
The above Mars Orbiter Camera (MOC) image shows a portion of the slope just inside the south rim of the approximately 400 kilometer-(250 mile)-wide Schiaparelli Basin near the martian equator. The large white arrow points to a steep cliff exposure of dark-toned rock. The small white arrow points to one of several ~18 meter (59 feet) diameter boulders that apparently broke off the steep, dark cliff and rolled down the slope to the basin floor. Each boulder left behind a trail on the relatively soft, dusty slope. In addition, some of the boulders exhibit a bright wind streak pointing toward the lower left/center, indicating that these boulders have been sitting there long enough to influence local wind distribution of sediment.
Before the Mars Global Surveyor (MGS) mission, boulder tracks such as these had never been seen on Mars before, but in the 1960s and 1970s several examples on the Moon and Earth were documented. The picture shown here covers an area approximately 2.8 kilometers (1.7 miles) by 4.4 kilometers (2.7 miles). Illumination is from the lower left. The picture was acquired in January 1998 during the MGS Aerobrake-1 Orbits imaging campaign, and was presented at the 30th Lunar and Planetary Science Conference in Houston, Texas, March 1999.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
17 October 2006
The middle portion of the northern summer season is the ideal time of year to capture relatively dust- and haze-free views of martian north polar terrain. This year, much more of the north polar cap has sublimed away than has been evident in previous northern summers going back to 1999, when Mars Global Surveyor (MGS) began the Mapping Phase of the mission. This MGS Mars Orbiter Camera (MOC) image shows a nearly ice-free view of layers exposed by erosion in the north polar region. The light-toned patches are remnants of water ice frost. The layers are generally considered by the Mars scientific community to be record of past depositions of ice and dust. This picture is located near 82.5°N, 118.6°W, and covers an area about 3 km by 10 km (1.9 by 6.2 miles). Sunlight illuminates the scene from the upper left; the image was acquired on 22 September 2006.
Figure caption from Science Magazine
Voir l'image PIA00802: Hebes Chasma #1 sur le site de la NASA.
19 September 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the results of wind action on the floor of the giant martian impact basin, Huygens. The large crater in this image has a wind streak on its lee side, pointing toward the lower right (southeast). Usually, a light-toned wind streak behind a crater on Mars will be composed of a thin veneer of dust that the wind was not able to erode because it was protected by the presence of the crater's raised rims. In this case, the streak is caused by something different -- by the fact that dark, windblown sand has not been able to accumulate behind the crater.
Location near: 13.0°S, 303.7°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
The MOC image shown above, 45205, was obtained during the 452nd orbit of Mars Global Surveyor at 3:10 p.m. PDT on July 26, 1998. The image is located near latitude 76.87°N, longitude 253.81°W, and it shows a close-up view of martian sand dunes. These dunes were not visible to MOC until the last week of July. Just a few months earlier, the dunes were likely covered with frost, obscured by thick clouds, and cloaked by the darkness of the martian polar winter. Indeed, small patches of bright frost were still present when the picture was taken (e.g., the bright patches on the west (left) side of each crescentic dune in (left image).
As the above picture illustrates, the camera on board Mars Global Surveyor (MOC) continued to take exciting new views of the martian surface throughout July 1998. As the month progressed, the ground track-- the area visible to the camera--migrated farther north. Simultaneously, sunlight began falling on the north polar regions, making it possible to take some pictures at far northern latitudes. However, these regions have been tricky to photograph because of thick clouds and hazes. The image shown here, for example, is relatively bland gray (has relatively low contrast) because of clouds.
As first seen by the Viking 2 Orbiter in 1976, a vast "sea" of sand dunes surrounds the north polar cap. The dunes imaged by MOC (above) are classic forms known as barchan dunes--the small, crescent-shaped hills (see left image above)-- and transverse dunes--ridges that resemble coalesced barchans (shown in right image above). These dunes are similar in size and shape to familiar sand dunes found in desert regions on Earth. These two varieties form from winds that persistently come from a single direction (in this case, from the southwest).
Over the next several months, the sky above these dunes will clear. Northern Summer will arrive near the end of January 1999, and Mars Global Surveyor should have an excellent view of this region when it begins its mapping mission in late March 1999. Because it is in a polar orbit, Mars Global Surveyor will have many opportunities to revisit the north polar dunes in 1999. The images in 1999 will have resolutions around 1.5 meters (5 feet) per pixel--a substantial improvement even over the pictures shown here.
Voir l'image PIA01331: Spring Time View of North Polar Sand Dunes sur le site de la NASA.
16 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dust devil producing a track among dozens of other, preexisting streaks on a dusty, south middle-latitude plain on Mars. The dust devil is located just above (north/northwest of) a small, dark-floored crater.
Location near: 58.7°S, 141.1°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
Mars Pathfinder was soon joined by the orbiting Mars Global Surveyor on September 11, 1997 (PDT). Mars Global Surveyor's high resolution camera, MOC, took a picture of the Mars Pathfinder landing site region during its 256th orbit on April 22, 1998. This picture--at about 5 meters (11 feet) per pixel--is the best available for the site. The previous best images were from the Viking 1 Orbiter in 1976, and had resolutions of about 38 meters (125 feet) per pixel.
The MOC image has allowed scientists to determine the exact location of the Mars Pathfinder lander. Unfortunately, the image resolution is not good enough to actually see the lander--nor can any of the familiar boulders (e.g., "Yogi") be seen at this resolution.
Using the MOC image, the landing site location has been refined by Dr. Michael Malin, Principal Investigator for the Mars Global Surveyor MOC Team and a Participating Scientist on the Mars Pathfinder mission. The images above illustrate how the landing site was located by using the "sight lines" published by T. Parker (Jet Propulsion Laboratory, Pasadena, CA) and topographic map provided by R. Kirk (U.S. Geological Survey, Flagstaff, AZ).
Left image: MOC image 25603 subframe, shown at 15 meters (about 50 feet) per pixel resolution. Small, colored box is a topographic map of the Mars Pathfinder landing site produced by the U.S. Geological Survey (Flagstaff, AZ) from Mars Pathfinder stereographic images . Dark, heavy lines are "sight lines" to various landmarks seen along the horizon in Mars Pathfinder camera images, measured by T. Parker and matched to features seen in Viking Orbiter images. These lines were published in Science, v. 278, p. 1746, December 5, 1997. The lighter, thinner sightlines are the same lines, adjusted to match the same features as seen in the higher resolution MOC image 25603. These lines indicate the location of the landing site to within a few hundred meters/yards. The colored box--the topographic map--has been placed at the location of the actual landing site. The lander and rover would be located at the center of the colored box. The white box shows the context of the image to the right. North is up, illumination is from the lower right.
Top right image: Location of Mars Pathfinder lander and Sojourner Rover, relative to Mars Global Surveyor MOC image obtained April 1998. The famous "Twin Peaks"-- first seen by the lander on July 4, 1997--are shown at the lower left. The scale bar indicates distance in feet and in meters. The colored box is the topographic map of the Mars Pathfinder landing site, derived from Pathfinder camera stereoscopic images by R. Kirk and colleagues. The lander and rover were located in the center of the colored box.
Bottom right image: Location of Mars Pathfinder landing site in MOC image 25603. The lander is located in the center of the white box. The original resolution of the MOC image was about 3.3 meters (11 feet) per pixel; however, because the region was hazy at the time the picture was taken, the effective resolution is only about 5 meters (16.4 feet) per pixel. Thus, the lander and rover are too small to actually be seen in the image. The colored box, 120 m (just under 400 ft) on a side, is the topographic map of the landing site. The topographic map was made using the stereographic images taken by Mars Pathfinder in 1997. Low areas-- depressions--are blue and purple, high areas--hill--are shown as red. The range of heights is actually fairly small--a total of 4 m (about 13 ft) from dark purple to bright red. The lander is represented within the black dot at the center of the map. A preliminary version of the topographic map that is generally similar to this more refined version was published in Science, v. 278, p. 1736, December 5, 1997.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01447: Mars Pathfinder First Anniversary Special -- Refined Landing Site Location sur le site de la NASA.
Two views of Arsia Mons, the southern most of the Tharsis montes, shown as topography draped over a Viking image mosaic. MOLA topography clearly shows the caldera structure and the flank massive breakout that produced a major side lobe. The vertical exaggeration is 10:1.
Voir l'image PIA02804: Major Martian Volcanoes from MOLA - Arsia Mons sur le site de la NASA.
During the first week of May 1999, the Mars Orbiter Camera (MOC) spent sometime peering into martian impact craters.
This crater is located on a plain west of the Tartarus Montes (east of Elysium Mons volcano). The crater is about 2.7 kilometers (1.7 miles) across. Illumination is from the left.
If you have ever visited the famous Meteor Crater in northern Arizona, U.S.A., then you are aware of its immense size on a human scale. The Arizona crater, however, is only 1 kilometer across (0.62 miles), whereas this crater is nearly three times that size.
This crater was formed by the impact and explosion of a meteorite at some time in the martian past. After the crater formed, it was modified by wind and erosion. The crater shows deposits of sand and dust on the floor and in low areas around the rim, also boulders and other debris that has slid down the inside walls of the crater; and some crater walls show exposures of bedrock.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
The Mars Orbiter Camera (MOC) on board the Mars Global Surveyor (MGS)spacecraft was designed to be able to take pictures that "bridge the gap" between what could be seen by the Mariner 9 and Viking Orbiters from space and what could be seen by landers from the ground. In other words, MOC was designed to be able to see boulders of sizes similar to and larger than those named "Yogi" at the Mars Pathfinder site and "Big Joe" at the Viking 1 landing site. To see such boulders, a resolution of at least 1.5 meters (5 feet) per pixel was required.
With the start of the MGS Mapping Phase of the mission during the second week of March 1999, the MOC team is pleased to report that "the gap is bridged." This image shows a field of boulders on the surface of a landslide deposit in Ganges Chasma. Ganges Chasma is one of the valleys in the Valles Marineris canyon system. The image resolution is 1.5 meters per pixel. The boulders shown here range in size from about 2 meters (7 feet) to about 20 meters (66 feet) in size. The image covers an area 1 kilometer (0.62 miles) across, and illumination is from the upper left.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
"They look like bushes!" That's what almost everyone says when they see the dark features found in pictures taken of sand dunes in the polar regions as they are beginning to defrost after a long, cold winter. It is hard to escape the fact that, at first glance, these images acquired by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) over both polar regions during the spring and summer seasons, do indeed resemble aerial photographs of sand dune fields on Earth--complete with vegetation growing on and around them! Of course, this is not what the features are, as we describe below and in related picture captions. Still, don't they look like vegetation to you? Shown here are two views of the same MGS MOC image. On the left is the full scene, on the right is an expanded view of a portion of the scene on the left. The bright, smooth surfaces that are dotted with occasional, nearly triangular dark spots are sand dunes covered by winter frost.
The MGS MOC has been used over the past several months (April-August 1999) to monitor dark spots as they form and evolve on polar dune surfaces. The dark spots typically appear first along the lower margins of a dune--similar to the position of bushes and tufts of grass that occur in and among some sand dunes on Earth.
Because the martian air pressure is very low--100 times lower than at Sea Level on Earth--ice on Mars does not melt and become liquid when it warms up. Instead, ice sublimes--that is, it changes directly from solid to gas, just as "dry ice" does on Earth. As polar dunes emerge from the months-long winter night, and first become exposed to sunlight, the bright winter frost and snow begins to sublime. This process is not uniform everywhere on a dune, but begins in small spots and then over several months it spreads until the entire dune is spotted like a leopard.
The early stages of the defrosting process--as in the picture shown here--give the impression that something is "growing" on the dunes. The sand underneath the frost is dark, just like basalt beach sand in Hawaii. Once it is exposed to sunlight, the dark sand probably absorbs sunlight and helps speed the defrosting of each sand dune.
This picture was taken by MGS MOC on July 21, 1999. The dunes are located in the south polar region and are expected to be completely defrosted by November or December 1999. North is approximately up, and sunlight illuminates the scene from the upper left. The 500 meter scale bar equals 547 yards; the 300 meter scale is also 328 yards.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
23 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an unusally-shaped (not circular) impact crater in the Elysium region of Mars. A dark-toned lava flow surface is seen in the southern (lower) portion of the image.
Location near: 5.9°N, 220.0°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
Two views of Alba Patera with topography draped over a Viking image mosaic. MOLA data have clarified the relationship between fault location and topography on and surrounding the Alba construct, providing insight into the volcanological and geophysical processes that shaped the edifice. The vertical exaggeration is 10:1.
Voir l'image PIA02803: Major Martian Volcanoes from MOLA - Alba Patera sur le site de la NASA.
20 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows platy flow surfaces in the Marte Vallis region of Mars. The origin of the flows is not well-understood, but as some Mars scientists have suggested, the flows may be the product of low viscosity (very fluid), high temperature volcanic eruptions, or perhaps they are the remains of large-scale mud flows. In either case, the materials are solid and hold a record of small meteor impact craters, thus indicating that they are not composed of ice, as still others have speculated.
Location near: 6.7°N, 182.0°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
Shortly after midnight Sunday morning (5 April 1998 12:39 AM PST), the Mars Orbiter Camera (MOC) on the Mars Global Surveyor (MGS) spacecraft successfully acquired a high resolution image of the "Face on Mars" feature in the Cydonia region. The image was transmitted to Earth on Sunday, and retrieved from the mission computer data base Monday morning (6 April 1998). The image was processed at the Malin Space Science Systems (MSSS) facility 9:15 AM and the raw image immediately transferred to the Jet Propulsion Laboratory (JPL) for release to the Internet. The images shown here were subsequently processed at MSSS.
The picture was acquired 375 seconds after the spacecraft's 220th close approach to Mars. At that time, the "Face," located at approximately 40.8° N, 9.6° W, was 275 miles (444 km) from the spacecraft. The "morning" sun was 25° above the horizon. The picture has a resolution of 14.1 feet (4.3 meters) per pixel, making it ten times higher resolution than the best previous image of the feature, which was taken by the Viking Mission in the mid-1970's. The full image covers an area 2.7 miles (4.4 km) wide and 25.7 miles (41.5 km) long. Processing Image processing has been applied to the images in order to improve the visibility of features. This processing included the following steps:
The image was processed to remove the sensitivity differences between adjacent picture elements (calibrated). This removes the vertical streaking.
The contrast and brightness of the image was adjusted, and "filters" were applied to enhance detail at several scales.
The image was then geometrically warped to meet the computed position information for a mercator-type map. This corrected for the left-right flip, and the non-vertical viewing angle (about 45° from vertical), but also introduced some vertical "elongation" of the image for the same reason Greenland looks larger than Africa on a mercator map of the Earth.
A section of the image, containing the "Face" and a couple of nearly impact craters and hills, was "cut" out of the full image and reproduced separately.
See PIA01441-1442 for additional processing steps. Also see PIA01236 for the raw image.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01440: Mars Orbiter Camera Views the "Face on Mars" - Calibrated, contrast enhanced, filtered sur le site de la NASA.
6 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a frosty, springtime scene in the north polar region of Mars. The area is blanketed by a maze of sand dunes; their appearance is enhanced by subliming, seasonal carbon dioxide frost.
Location near: 80.2°N, 168.8°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
The area outlined in the upper right image, the highest resolution view of the region previously available, is 6.6 km (4 miles) wide by 55.6 km (34.5 miles) long. The ridges to the north and south are about 4000 m (13,000 feet) above the floor of the troughs, but in the area photographed, the relief is slightly lower (about 3000 m, or 10,000 feet). The top portion of the image is shown on the left, and a section of that image is shown enlarged at lower right. The scale is 6.45 m/pixel across the image by 9.65 m/pixel down the image. The left and lower right images are available at higher resolution as PIA01022 and PIA01023, respectively.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01021: Western Tithonium Chasma/Ius Chasma, Valles Marineris sur le site de la NASA.
The large pits, troughs, and "swiss cheese" of the south polar residual cap appear to have been formed in the upper 4 or 5 layers of the polar material. Each layer is approximately 2 meters (6.6 feet) thick. Some Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images of this terrain show examples in which older pitted and eroded layers have been previously buried and are now being exhumed. The example shown here includes two narrow, diagonal slopes that trend from upper left toward lower right at the left/center portion of the frame. Along the bottoms of these slopes are revealed a layer that underlies them in which there are many more pits and troughs than in the upper layer. It is likely in this case that the lower layer formed its pits and troughs before it was covered by the upper layer. This observation suggests that the troughs, pits, and "swiss cheese" features of the south polar cap are very old and form over long time scales.
The picture is located near 84.6°S, 45.1°W, and covers an area 3 km by 5 km (1.9 x 3.1 mi) at a resolution of about 3.8 meters (12 ft) per pixel. The image was taken during southern spring on August 29, 1999.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02375: Complex Burial and Exhumation of South Polar Cap Pitted Terrain sur le site de la NASA.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01028: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris - High Resolution Image sur le site de la NASA.
Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01170: Nanedi Vallis: Sustained Water Flow? - High Resolution Image sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view of the south polar cap surface was obtained during southern spring on November 3, 1999. Located near 87.0°S, 5.9°W, this view covers 3 by 3 kilometers (1.9 x 1.9 miles) at 1.5 meters per pixel. The pits are only a few meters deep, at most, as determined by measuring shadows cast in them.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02372: Martian South Polar Cap Close-Up sur le site de la NASA.
Many of the craters found on the northern plains of Mars have been partly filled or buried by some material (possibly sediment). The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image presented here (MOC2-136b, above left) shows a high-resolution view of a tiny portion of the floor of one of these northern plains craters. The crater, located in Utopia Planitia at 44°N, 258°W, is shown on the right (MOC2-136a)with a small white box to indicate the location of the MOC image. The MOC image reveals that the material covering the floor of this crater is cracked and pitted. The origin and source of material that has been deposited in this crater is unknown.
The MOC image was acquired in June 1999 and covers an area only 1.1 kilometers (0.7 miles) wide at a resolution of 1.8 meters (6 feet) per pixel. The context picture is a mosaic of Viking 2 orbiter images 010B53 and 010B55, taken in 1976. Both images are illuminated from the left. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01343: Cracks in Utopia sur le site de la NASA.
During the first week of May 1999, the Mars Orbiter Camera (MOC) spent sometime peering into martian impact craters.
This crater is found on Hesperia Planum and is 7.3 kilometers (4.5 miles) across. Illumination is from the upper left.
If you have ever visited the famous Meteor Crater in northern Arizona, U.S.A., then you are aware of its immense size on a human scale. The Arizona crater, however, is only 1 kilometer across (0.62 miles), this crater is seven times wider.
This crater was formed by the impact and explosion of a meteorite at some time in the martian past. After the crater formed, it was modified by wind and erosion. The crater shows deposits of sand and dust on the floor and in low areas around their rim, also boulders and other debris that has slid down the inside walls of the crater; and some crater walls show exposures of bedrock.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
What will Mars Polar Lander find when it reaches the red planet on December 3, 1999? The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC)--currently operating in Mars orbit since September 1997--is providing some of our highest-resolution views of the planet ever obtained. MOC, in fact, can see objects the size of automobiles with its 1.5 meter (5 ft) per pixel capability.
To give some sense of the nature of polar terrain in the vicinity of Mars Polar Lander's 76°S, 195°W landing zone, very high resolution MOC images are here compared with the "main campus" of the Jet Propulsion Laboratory (JPL). JPL is located in Pasadena, California, and is part of the California Institute of Technology (Caltech). Together with partners Lockheed Martin Astronautics (Denver, CO), University of California-Los Angeles, The Planetary Society (Pasadena, CA), and Malin Space Science Systems (San Diego, CA), JPL is operating and managing the Mars Polar Lander and Deep Space 2 missions under contract from NASA.
The three MOC images shown next to each view of JPL represent the three most abundant terrain types seen in the Mars Polar Lander landing ellipse--ridges and small knobs, ridges and gullies, and ridges and pits. Each is shown at the same scale as the buildings of the Jet Propulsion Laboratory (1.5 m/pixel). Each image is about 400 meters (437 yards) across and is illuminated by sunlight from the lower right.
Mars Polar Lander Landing Zone Compared With JPL
The picture on the left is a MOC image taken in mid-November 1999 near the west edge of Mars Polar Lander's landing ellipse. Many small, bright pinnacles or knobs are visible amid a few circular features and dark patches. The picture on the right shows a portion of the Jet Propulsion Laboratory at the same scale. Note that buildings and some trees can be discerned in the JPL photo.
Ridges and Gullies Compared to Features of Similar Scale
Taken in November 1999 after the winter frost had finally cleared away, this view of typical ridged and gullied terrain in the Mars Polar Lander ellipse (left) is compared at the same scale with the buildings of the Jet Propulsion Laboratory (right). A person standing in one of the gullies or cracks in the polar terrain would certainly notice that they are down in a hole!
Ridges and Pits Compared to Features of Similar Scale
The image on the left shows a third sample of terrain in the Mars Polar Lander landing zone. This picture was acquired in mid/late November 1999 after the seasonal frost had sublimed away. The terrain appears rugged but not nearly as rugged as the artificial terrain of buildings and sidewalks at the Jet Propulsion Laboratory (right).
Voir l'image PIA02347: Mars Polar Lander Landing Zone Compared With JPL sur le site de la NASA.
The ridged surface in the lower half of this image is that of a large lava flow in Daedalia Planum, southwest of the Arsia Mons volcano. The flow was stopped here by a buried crater rim (topographic high in the upper half of the image). MOC image taken June 5, 1999.
Some exposures of layered material interpreted to be sedimentary rock on Mars are quite thick and reveal a complex history of change. Gale Crater, a basin 172 km (107 mi) in diameter located at 5.4°S, 222.2°W, contains a large central mound of layered rock that, in places, is more than 2.3 km (1.4 mi) thick. The pictures shown here illustrate some of the variety of features that occur in the layered mound, and show that there is evidence for a history that included a hiatus in the deposition of new material, erosion and impact cratering of the material, followed by new deposition on top of the eroded surface.
Picture A shows an oblique view--looking toward the southeast--of Gale Crater and its central mound that was generated by combining Mars Orbiter Camera (MOC) wide angle images with Mars Orbiter Laser Altimeter (MOLA) elevation data from the Mars Global Surveyor (MGS) spacecraft. The white box indicates the location of MOC narrow angle image M03-01521, which was used by MOC scientists to begin the process of deciphering the history recorded in the layers that make up the large central mound. This mound is thought to be a remnant of a once larger deposit that probably filled much or all of Gale Crater and perhaps extended onto the surrounding terrain.
Picture B shows a view of Gale Crater looking straight-down from MGS's ~370 km-high (~230 mi-high) orbit. In this mosaic of MOC wide angle images, north is up, sunlight illuminates the scene from the upper left, and the location of the high resolution view, M03-01521, is again indicated by a white box. Other MOC high resolution views, such as M00-01602, show that the dark material surrounding the mound on the crater floor consists mainly of sand dunes. The high resolution view, MOC image M03-01521, was used to examine the details of layered rock exposed in the Gale Crater central mound. It is shown here with north toward the lower left (so it is oriented roughly the same as is seen in (A)) and illuminated by sunlight from the lower right. Dark sand dunes can be seen near the contact between the crater floor and the mound.
Picture C is an interpreted cross-section through the part of the Gale Crater mound that is visible in MOC image M03-01521. The lower part of Picture C is the image, M03-01521, with each different rock unit (some have many, thin layers, others have few layers, others erode differently or have different brightness, etc.) shown by a different color. The cross section uses the MOLA topographic profile that was acquired by MGS at the same time as the MOC image. The MOLA data give elevations for the area between the two straight black lines running lengthwise across the MOC image. Where the MOLA profile intersects the contact between each colored unit, the position of this unit in the cross section can be inferred. These data and the observations presented in PIA02844 and PIA02845 show that the Gale Crater mound preserves a complex history that includes the formation of many layers in the lower part of the mound, a period of erosion and cratering on these lower layered units, then deposition on top of these materials by younger, brighter, and not-layered (i.e., massive) units.
Voir l'image PIA02843: Sediment History Preserved in Gale Crater Central Mound sur le site de la NASA.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The spacecraft has been using atmospheric drag to reduce the size of its orbit for the past three weeks, and will achieve a circular orbit only 400 km (248 mi) above the surface early next year. Mapping operations begin in March 1998. At that time, MOC narrow angle images will be 5-10 times higher resolution than these pictures.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA00944: Rotated Perspective View of Nirgal Vallis sur le site de la NASA.
This subsection of frame P006_05 is shown here at reduced resolution because the full image is almost 7 MBytes in size. Because the MOC acquires its images one line at a time, the cant angle towards the sun-lit portion of the planet, the spacecraft orbital velocity, and the spacecraft rotational velocity combined to significantly distort the image. However, even in this reduced resolution version, dunes can be seen in the canyon and in areas on the upland surface around the canyon.
Nirgal Vallis is one of a number of canyons called valley networks or runoff channels. Much of the debate concerning the origin of these valleys centers on whether they were formed by water flowing across the surface, or by collapse and upslope erosion associated with groundwater processes. At the resolution of this image, it is just barely possible to discern an interwoven pattern of lines on the highland surrounding the valley, but it is not possible to tell whether this is a pattern of surficial debris (sand or dust), as might be expected with the amount of crater burial seen, or a pattern of drainage channels. With 4X better resolution from its mapping orbit, MOC should easily be able to tell the difference between these two possibilities.
Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The spacecraft has been using atmospheric drag to reduce the size of its orbit for the past three weeks, and will achieve a circular orbit only 400 km (248 mi) above the surface early next year. Mapping operations begin in March 1998. At that time, MOC narrow angle images will be 5-10 times higher resolution than these pictures.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA00943: Subsection of Nirgal Vallis Image sur le site de la NASA.
Mars Global Surveyor's Mars Orbiter Camera continues to reveal a surface of variety. Never before has Mars been scrutinized in such detail, with images sampling narrow strips of terrain that are as varied as the surface of our own Earth. This picture provides an example of just how strange Mars looks at this new resolution. This surface--located in northern Terra Cimmeria about 210 km (130 mi)southwest of Gusev Crater--shows rounded, rocky ridges separated by lowlands filled with sand or dust. The fill--whether sand or dust--is probably hardened to form a surface strong enough to have bright windblown ripples and small impact craters on it. This picture covers an area 3 km (1.9 mi) wide by 3.9 km (2.4 mi) and is illuminated from the upper left.
By the way, do you see a duck in this picture? Look carefully. If you give up, click here!
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
The jumbled and broken terrain in the picture on the left is known as chaotic terrain. Chaotic terrain was first observed in Mariner 6 and 7 images of Mars more than 30 years ago, and is thought to result from collapse after material--perhaps water or ice--was removed from the subsurface by events such as the formation of giant flood channels. The region shown here is named "Margaritifer Chaos." The left picture is a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) red wide angle camera context frame that covers an area 115 km (71 miles) across. The small white box is centered at 10.3°S, 21.4°W and indicates the location of the high-resolution view on the right. The high resolution view (right) covers a small portion of the Margaritifer Chaos at 1.8 meters (6 feet) per pixel. The area shown is 3 km (1.9 miles) across. Uplands are lumpy with small bright outcrops of bedrock. Lowlands or valleys in the chaotic terrain have floors covered by light-toned windblown d rifts. This image is typical of the very highest-resolution views of the equatorial latitudes of Mars. Both pictures are illuminated from the left/upper left, north is toward the top.
Voir l'image PIA02340: The Terrain of Margaritifer Chaos sur le site de la NASA.
Some of the geological features of Mars defy conventional, or simple, explanations. A recent example is on the wall of a 72 kilometer-wide (45 mile-wide) impact crater in Promethei Terra. The crater (above left) is located at 39°S, 247°W. Its inner walls appear in low-resolution images to be deeply gullied.
A high resolution Mars Orbiter Camera (MOC) image shows that each gully on the crater's inner wall contains a tongue of material that appears to have flowed (to best see this, click on the icon—above right—and examine the full image). Ridges and grooves that converge toward the center of each gully and show a pronounced curvature are oriented in a manner that seems to suggest that material has flowed from the top toward the bottom of the picture. This pattern is not unlike pouring pancake batter into a pan... the viscous fluid will form a steep, lobate margin and spread outward across the pan. The ridges and grooves seen in the image are also more reminiscent of the movement of material out and away from a place of confinement, as opposed to the types of features seen when they flow into a more confined area. Mud and lava-flows, and even some glaciers, for the most part behave in this manner. From these observations, and based solely on the appearance, one might conclude that the features formed by moving from the top of the image towards the bottom.
But this is not the case! The material cannot have flowed from the top towards the bottom of the area seen in the high resolution image (above, right), because the crater floor (which is the lowest area in the image) is at the top of the picture. The location and correct orientation of the high resolution image is shown by a white box in the context frame on the left. Since gravity pulls the material in the gullies downhill—not uphill—the pattern of ridges and grooves found on these gully-filling materials is puzzling. An explanation may lie in the nature of the material (e.g., how viscous was the pancake batter-like material?) and how rapidly it moved, but for now this remains an unexplained martian phenomenon.
The context image (above, left) was taken by the MOC red wide angle camera at the same time that the MOC narrow angle camera obtained the high resolution view (above, right). Context images such as this provide a simple way to determine the location of each new high resolution view of the planet. Both images are illuminated from the upper left. The high resolution image covers an area 3 km (1.9 mi) across.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02086: Martian Mystery: Do Some Materials Flow Uphill? sur le site de la NASA.
The layered terrains of the polar regions of Mars are among the most exotic planetary landscapes in our Solar System. The layers exposed in the south polar residual cap, vividly shown in the top view, are thought to contain detailed records of Mars' climate history over the last 100 million years or so. The materials that comprise the south polar layers may include frozen carbon dioxide, water ice, and fine dust. The bottom picture shows complex erosional patterns that have developed on the south polar cap, perhaps by a combination of sublimation, wind erosion, and ground-collapse. Because the south polar terrains are so strange and new to human eyes, no one (yet) has entirely adequate explanations as to what is being seen.
These images were acquired by the Mars Orbiter Camera aboard the Mars Global Surveyor spacecraft during the southern spring season in October 1999. Each of these two pictures is a mosaic of many individual MOC images acquired at about 12 m/pixel scale that completely cover the highest latitude (87°S) visible to MOC on each orbital pass over the polar region. Both mosaics cover areas of about 10 x 4 kilometers (6.2 x 2.5 miles) near 87°S, 10°W in the central region of the permanent--or residual--south polar cap. They show features at the scale of a small house. Sunlight illuminates each scene from the left."Gaps" at the upper and lower right of the second mosaic, above, are areas that were not covered by MOC in October 1999.
Voir l'image PIA02391: High-Resolution South Polar Cap Mosaics sur le site de la NASA.
This is a sub-frame taken from near the center of PIA02843. Like the larger image, it is oriented with north toward the lower left. This area shows the thinly-bedded lower units of the Gale Crater mound. The lower part of the mound has hundreds of thin (2-5 meters; 2-5 yards thick) beds of similar thickness and properties--in this regard, the lower units are similar to the beds observed elsewhere on Mars, such as in southwestern Candor Chasma. The most striking feature in this sub-frame, however, is the area labeled "filled channel." This is interpreted to be a channel that was cut into the layered rock some time in the past. Perhaps it was cut by running water. Later, the channel was filled and then completely buried by additional sediment. At an even later time (closer to the present, but still very ancient), the material that buried the channel was stripped away, leaving a filled channel that, at its lower end (from center toward lower right) actually stands as a ridge higher than the surrounding terrain. This channel attests to the possible erosion of the layered rock by running water. It also indicates that there was a period in the past when the rock was eroded before being covered-up again. Such evidence and interpretations are pieces of the story of this area.
Note: This is a subframe of PIA02843
Voir l'image PIA02844: Sediment History Preserved in Gale Crater Central Mound sur le site de la NASA.
Each day, Mars Global Surveyor makes 12 orbits around the red planet. On each orbit at the present time (April 1999), the spacecraft passes from daylight into night somewhere over the northern plains of Mars, and re-emerges into daylight over the southern cratered highlands. The illumination conditions near the martian terminator--the line between night and day--are perfect for observing surface texture and topography. This picture shows a common, rough and bumpy texture that MOC has revealed on the northern plains of Mars. Note the eroded impact crater at the bottom right--small black dots along its rim are interpreted to be boulders. This image covers an area 3 kilometers (1.9 miles) wide by 8 kilometers (5 miles) long and is illuminated by the sun shining low from the northeastern horizon (from the upper right).
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01697: Northern Plains Textures Visible Near the Terminator sur le site de la NASA.
An example of the complexity of martian geologic history is shown by a crater in Kasei Vallis that was imaged during the 345th orbit of Mars Global Surveyor at 5:44 p.m. PDT on June 4, 1998. MOC image 34504 (above) shows a 6 kilometer (4 mile) diameter crater that was once buried by about 3 kilometers (2 miles) of martian "bedrock."
Kasei Vallis, seen in this Viking 1 Orbiter mosaic, is actually a system of giant channels thought to have been carved by catastrophic floods that occurred more than a billion years ago . A similar scenario was proposed to explain the Ares Vallis channel, where Mars Pathfinder landed in July 1997.
The Kasei Valles floods carved a deep and wide system of channels into the northern portion of Lunae Planum--a vast, relatively flat plain made up of layered rock that formed some time before the floods.
The crater shown above (and in local context in this Viking 1 Orbiter image 226a08) was partly excavated by the Kasei Valles floods. The crater is poking out from beneath an "island" in the Kasei Valles. The mesa was created in part by the flood, and by subsequent retreat--by small landslides--of the scarp that encircles it. A "mote" or trench partly encircles the crater to the west and south. This moat formed were the turbulence of the floodwaters interacting with the obstacle represented by the crater rim eroded material in front of, and along the side, of the crater. The rim was too high for the flood to overtop, and the flood lasted too short a time for the erosion to breach the crater rim and destroy it.
The crater seen here was most likely formed early in Mars history, perhaps as long as 3.5 billion years ago. Sometime after it formed by meteor impact, it was buried by the material that comprises Lunae Planum (the large plains unit of which the island appears to be part). The material composing the island is, at least in places, hard rock, since the brink of the cliff is sharp and the erosional ridges that extend down from the brink stand out in sharp relief. However, the processes that emplaced the rock were sufficiently gentle that the crater was not destroyed by that emplacement, nor by the burial. In that respect, the crater is like a giant fossil. Likewise, the process or processes that exposed the crater--the Kasei floods and retreat of the mesa scarp-- were also sufficiently "gentle" so that much of the crater's original appearance has been preserved.
This exhumed crater is one of many seen by MOC during its first year of operations. This particular crater was first suspected to have been exhumed when it was seen in images from Mariner 9 in 1972. The close-up view provided by MOC confirms that the crater has emerged from beneath the mesa, and that it suffered little damage from the Kasei floods.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01475: Exhumed Crater in Kasei Valles sur le site de la NASA.
13 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dike exhumed by erosion from beneath the cratered terrain near Auqakuh Vallis in northeastern Arabia Terra. The dike is the narrow, discontinuous ridge that cuts diagonally from the northwest (upper left) toward the southeast (lower right) across the scene. Typically, a dike is formed underground when molten rock -- magma -- is injected through a crack or fault. The magma eventually cools and hardens. A dike can also sometimes form in a non-volcanic setting by injection of wet sediment (which later hardens to rock) into an overlying sedimentary layer. The ridge is formed later, when surrounding rocks are eroded away, leaving the more erosion-resistant rock behind as a ridge. For an example on Earth, the famous Shiprock in northwestern New Mexico, U.S.A., has several dikes associated with it.
Location near: 31.4°N, 299.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
13 March 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of a trough in the Sirenum Fossae region. On the floor and walls of the trough, large -- truck- to house-sized -- boulders are observed at rest. However, there is evidence in this image for the potential for mobility. In the central portion of the south (bottom) wall, a faint line of depressions extends from near the middle of the wall, down to the rippled trough floor, ending very near one of the many boulders in the area. This line of depressions is a boulder track; it indicates the path followed by the boulder as it trundled downslope and eventually came to rest on the trough floor. Because it is on Mars, even when the boulder is sitting still, this once-rolling stone gathers no moss.
Location near: 29.4°S, 146.6°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
Mars Global Surveyor's Mars Orbiter Camera obtained its last SPO-2 images of Mars on September 12, 1998. SPO-2, or "Science Phasing Orbit-2," took place between early June and mid-September 1998. Shown above are MOC wide angle (red and blue band) images of the martian north polar region obtained around 3:15 a.m. PDT on September 12, 1998. This image, MOC image 55001, was one of the last pictures taken of the planet until the camera resumes its work in late-March 1999.
The north polar layered deposits, a terrain believed composed of ice and dust deposited over millions of years, dominates this view. The swirled pattern in the images above are channels eroded into this deposit. The pattern is accentuated by the illumination and seasonal frost differences that arise on sun-facing slopes during the summer. The permanent portion of the north polar cap covers most of the region with a layer of ice of unknown thickness.
At the time this picture was obtained, the martian northern hemisphere was in the midst of the early Spring season. The margin of the seasonal carbon dioxide frost cap was at about 67° N, so the ground throughout this image is covered by frost. The frost appears pink rather than white; this may result from textural changes in the frost as it sublimes or because the frost is contaminated by a small amount of reddish martian dust. Please note that these pictures have not been "calibrated" and so the colors are not necessarily accurately portrayed.
In addition to the north polar cap, the pictures also show some clouds. Some of the clouds on the right side of the images are long, linear features that cast similar long, dark shadows on the ground beneath them.
When the MOC resumes imaging of Mars in March 1999, summer will have arrived in the north polar regions and the area surrounding the permanent polar cap will appear much darker than it does here. The dark features surrounding the cap are sand dunes, and these are expected to darken over the next several months as seasonal ice sublimes and is removed from the surface.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01472: Martian North Polar Cap on September 12, 1998 sur le site de la NASA.
Beginning Thursday, December 16, 1999, the Mars Global Surveyor (MGS) spacecraft initiated a search for visible evidence of the fate of the missing Mars Polar Lander using the high resolution Mars Orbiter Camera (MOC) operated by Malin Space Science Systems of San Diego, California. Mars Polar Lander was lost during its landing attempt near 76.3°S, 195.0°W on the martian south polar layered terrain on December 3, 1999. Although the likelihood of seeing the lander is quite small, the MOC effort might provide some clues that shed light on what happened to the lander. The problem, however, is one of "pixels"--those little square boxes of different shades of gray that comprise a digital image.
The two pictures above illustrate the difficulty of finding the lander in MOC images. The picture at the top of the page is the first of the images that were acquired to look for the lander--this one was snapped by MOC around 3:36 p.m. Greenwich time on December 16th. Local time on Mars was about 2 p.m. Portions of this image are shown at 1/4th scale (left), full-scale (~1.5 meters, or 5 feet, per pixel--middle), and 10 times enlarged (right). Because the landing site is very far south (at this latitude on Earth, you would be in Antarctica), the Sun illumination is not ideal for taking high resolution pictures with MOC. Thus, the full-resolution MOC data for this region show a large amount of "salt and pepper" noise, which arises from statistical fluctuations in how light falling on the MOC charge-coupled-device (CCD) detector is converted to electricity. Other aspects of the MOC electronics also introduce noise. These effects are greatly reduced when taking pictures of portions of Mars that have better, more direct sunlight, or when the images are taken at reduced resolution to, in effect, "average-out" the noise.
The lower picture shows a model of the Mars Polar Lander sitting on a carpet in a conference room at Malin Space Science Systems. This model is illuminated in the same way that sunlight would illuminate the real lander at 2 p.m. local time in December 1999--in other words, the model is illuminated exactly the way it would be if it occurred in the MOC image shown above (left). This figure shows what the Mars Polar Lander would look like if viewed from above by cameras of different resolutions from 1 centimeter (0.4 inch) per pixel in the upper left to 1.5 meters (5 feet) per pixel in the lower right. The 1.5 meters per pixel view is the best resolution that can be achieved by MOC. Note that at MOC resolution, the lander is just a few pixels across.
The problem of recognizing the lander in MOC images is obvious--all that might be seen is a pattern of a few bright and dark gray pixels. This means that it will be extremely difficult to identify the lander by looking at the relatively noisy MOC images that can be acquired at the landing site--like those shown in the top picture.
How, then, is the MGS MOC team looking for the lander? Primarily, they are looking for associations of features that, together, would suggest whether or not the Mars landing was successful. For example, the parachute that was used to slow the lander from supersonic speeds to just under 300 km/hr (187 mph) was to have been jettisoned, along with part of the aeroshell that protected the lander from the extreme heat of entry, about 40 seconds before landing. The parachute and aeroshell are likely to be within a kilometer (6 tenths of a mile) of the lander. The parachute and aeroshell are nearly white, so they should stand out well against the red martian soil. The parachute, if lying on the ground in a fully open, flat position, would measure about 6 meters (20 feet)--thus it would cover three or four pixels (at most) in a MOC image. If the parachute can be found, the search for the lander can be narrowed to a small, nearby zone. If, as another example, the landing rockets kicked up a lot of dust and roughened the surface around the lander, evidence for this might show up as a dark circle surrounding a bright pixel (part of the lander) in the middle. The MOC operations team is using a set of these and similar scenarios to guide the examination of these images. The search continues...
Voir l'image PIA02349: Mars Polar Lander: The Search Begins sur le site de la NASA.
One of the earliest observations made by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) was that the upper crust of the planet appears to be layered to considerable depth. This was especially apparent, early in the mission, in the walls of the Valles Marineris chasms. However, layered mesas and mounds within the Valles Marineris troughs were recognized all the way back in 1972 with Mariner 9 images. The MOC image presented here shows many tens of layers of several meters (yards) thickness in the walls of a mesa in southern Melas Chasma in Valles Marineris. Erosion by mass wasting--landslides--has exposed these layers and created the dark fan-shaped deposits seen near the middle of the image. The floor of Melas Chasma is dark and covered with many parallel ridges and grooves (lower 1/3 of image). In the lower left corner of the picture, a bright, circular dust devil can be seen casting a columnar shadow toward the left. This image, illuminated by sunlight from the right/lower right, covers an area 3 kilometers (1.9 miles) wide and 8.2 kilometers (5.1 miles) long. The scene is located near 10.1°S, 74.4°W and was acquired on July 11, 1999. North is toward the lower left.
Voir l'image PIA02398: Layers and a Dust Devil in Melas Chasma sur le site de la NASA.
Daedalia Planum is a broad, wind-swept volcanic plain southwest of the Arsia Mons volcano. Since the 1972 Mariner 9 mission, this region has been known to have many wind streaks formed in the lee of obstacles (i.e., downwind of craters and hills) as wind blows loose sediment through the region. Here, the wind streaks are a combination of bright surfaces (where sand and/or dust has accumulated) and dark surfaces (where sand and/or dust has been removed). The streaks indicate wind blowing from right to left. Other evidence of wind action is found in the form of many parallel ridges and grooves that run diagonally across the scene--these probably formed by wind erosion at an earlier time when the wind was blowing from a direction different from that indicated by the bright and dark streaks. This picture was taken by the Mars Orbiter Camera (MOC) onboard the Mars Global Surveyor (MGS) and is illuminated from the left. The picture covers an area about 7.6 km (4.7 miles) by 9.3 km (5.8 miles).
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
The above figure shows the location of all high resolution (narrow angle) MOC images of the Cydonia region that have been obtained to date, including the first three taken in 1998 (PIA01240, PIA01241, AND PIA01440). These images are superimposed upon a mosaic of Viking images taken during the 1970's. Images acquired during the Science Phasing Orbit period of 1998 slant from bottom left to top right; Mapping Phase images (from 1999 and 2000) slant from lower right to upper left. Owing to the nature of the orbit, and in particular to the limitations on controlling the location of the orbit, the longitudinal distribution of images (left/right in the images above) is distinctly non-uniform. An attempt to take a picture of a portion of the "Face" itself in mid-February 2000 was foiled when the MGS spacecraft experienced a sequencing error and most of that day's data were not returned to Earth. Only the first 97 lines were received; the image's planned footprint is shown as a dashed box. This image is one in a series of eight.
Voir l'image PIA02389: Cydonia: Two Years Later sur le site de la NASA.
Except for small wind ripples on their surfaces, normal, active sand dunes have very smooth slopes. However, some dunes found in the Herschel Basin of Terra Cimmeria (around 15°S, 228°W) have very rough, grooved surfaces instead. These grooves indicate that the dune surfaces for some reason are cemented--i.e., the sand is not loose--and that wind has actually had to scour the sand to remove it and transport it away from these dunes. What has caused these dunes to become cemented is unknown, and dunes like this are extremely rare on Mars (they have only been seen in Herschel Basin, thus far). This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image was acquired on May 5, 1999, and is illuminated from the upper left.
Voir l'image PIA02358: The Groovy Dunes of Herschel sur le site de la NASA.
9 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows several overlapping lava flows located on the vast plains east of the volcano, Ascraeus Mons. Hundreds of lava flows cover the plains from Ascraeus Mons eastward to Kasei Valles. These flows have largely been mantled by fine dust; a few areas in the image exhibit dark streaks, where wind gusts have stripped away some of this thin dust mantle.
Location near: 5.2°N, 86.7°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
A picture taken by the camera on Mars Global Surveyor just one day earlier showed several thin, dark lines that--at first glance--looked like pathways blazed by off-road sport utility vehicles. Who's been driving around on Mars?
The MOC image in question (#26403), seen here at full resolution of 13.8 meters (45 feet) per pixel, was obtained around 10:22 a.m. PDT on April 26, 1998, during Mars Global Surveyor's 264th orbit. North is approximately up, illumination is from the lower right. Located in eastern Arabia Terra near 16.5° N latitude, 311.4° W longitude, the image showed a number of natural features--small craters formed by meteor impact, several buttes and mesas left by erosion of the surrounding terrain, small dunes and drifts, and a mantle of dust that varies in thickness from place to place. But the new picture also showed two dark lines--each varying in width up to about 15 meters (49 feet)--that extended several kilometers/miles across the image.
Lines like these have been seen before on Mars. They are most likely the result of dust devils--columnar vortices of wind that move across the landscape, pick up dust, and look somewhat like miniature tornadoes. Dust devils are a common occurrence in dry and desert landscapes on Earth as well as Mars. They form when the ground heats up during the day, warming the air immediately above the surface. As pockets of warm air rise and interfere with one another, they create horizontal pressure variations that, combined with other meteorological winds, cause the upward moving air to spin (the direction of the spin is controlled by the same Coriolis forces that cause terrestrial hurricanes to spin in specific directions). As the spinning column of air moves across the surface, it occasionally encounters dust on the surface, which it can suck upward. This dust rises into the spinning air, giving the appearance of a tornado-like column that moves across the landscape. As the column of air moves, its ability to pick up dust varies--sometimes they hold a lot of dust and are nearly opaque; sometimes you cannot even see them. Dust-devils rarely last long, since their very motion changes the conditions that allowed them to form in the first place.
Mars Pathfinder detected the passage of several dust devils during its 83 days of operation on Mars in 1997. Mariner 9 and the Viking landers and orbiters of the 1970s also found evidence that dust devils occur on Mars; indeed, some Viking Orbiter images actually show dust devil clouds. MOC image 26403 is the latest entry in the body of evidence for the work of wind in the modern martian environment. The MOC Science Team is continuing to study these and other streaks caused by wind interacting with the martian surface.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01463: SUV Tracks On Mars? The "Devil" is in the Details sur le site de la NASA.
Images from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) dramatically illustrate that many places on the red planet have outcrops of layered geologic materials. The two pictures above show the remains of layered material inside craters in southwestern Utopia Planitia (see inset for detailed view). These remnant layers indicate that the craters--and perhaps the plains that surround them--were once buried beneath a deposit that has since been eroded away. This theme of layered outcrops and exhumed craters appears to be one of the dominant observations that MGS MOC has made--to date--about Mars. The origin and composition of the layered material--and its ultimate fate once it was largely eroded away--are unknown.
Each of the two pictures shown here covers an area about 4 kilometers (2.5 miles) by 6.3 kilometers (3.9 miles). Illumination is from the lower right. These are subframes of a single MOC image acquired in July 1998 during the MGS Science Phasing Orbits imaging campaign. This figure was presented at the 30th Lunar and Planetary Science Conference in Houston, Texas, March 1999.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01681: Eroded Layered Material in Southwest Utopia Planitia sur le site de la NASA.
Figure caption from Science Magazine
Voir l'image PIA00803: Hebes Chasma #2 sur le site de la NASA.
Pavonis Mons is the middle of the three large Tharsis Montes volcanoes in the martian western hemisphere. Located on the equator at about 113°W longitude, Pavonis Mons stands as much as 7 kilometers (4 miles) above the surrounding plain. The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) recently spied the above chain of elliptical pits on the lower east flank of Pavonis Mons. The picture covers an area 3 kilometers (1.9 miles) wide by 3.4 kilometers (2.1 miles) in length. The pits are aligned down the center of a 485 meters-(530 yards)-wide, shallow trough. The straight trough and the pits were both formed by collapse associated with faulting. The scarp on each side of the trough is a fault line--troughs of this type are known to geologists as graben. Such features are typically formed when the ground is being moved apart by tectonic forces, or when the ground is uplifted by molten rock injected into the near sub-surface from deeper underground. Both processes may be contributing to the features seen on Pavonis Mons. The pits follow the trend of these faults, and indicate the locus of collapse. Illumination is from the upper left in this image.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Figure caption from Science Magazine
Voir l'image PIA00804: Crommelin Crater #1 sur le site de la NASA.
Orbit: 220
Range: 444.21 km
Resolution: 4.32 m/pixel
Image dimensions: 4.42 km X 82.94 km
Line time: 0.69 msec
Emission angle: 44.66 degrees
Incidence angle: 64.96 degrees
Phase angle: 61.97 degrees
Scan rate: ~0.1 degree/sec
Start time: periapsis + 375 sec
Sequence submitted to JPL: Sat 04/04/98 15:15 PST
Image acquired by MOC: Sun 04/05/98 00:39:37 PST
Data retrieved from JPL: Mon 04/06/98 9:05 PDT
Voir l'image PIA01236: Cydonia Region sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image was obtained during the first week of June 1999. It shows a portion of the Nilosyrtis Mensae region, located north of Syrtis Major and southwest of Utopia Planitia. This region is part of a planet-wide transition zone that separates the high, cratered terrain of the southern two thirds of Mars from the low, relatively uncratered northern plains. Old remnants of the cratered highlands are common in this transition zone, and they are usually in the form of mesas and buttes.
The MOC image shows several low, flat-topped mesas. Although flat at large scale, their surfaces are quite rough and bumpy at smaller scales. Many of these bumps might be boulders, but the resolution of this particular image (4.5 meters--15 feet--per pixel) is not high enough to be certain. The lowlands surrounding the mesas are cracked and pitted--especially the darker surfaces on the right side of the image. The cause of the pitting is not known and can only be speculated upon (because the material removed from each pit is now gone). Possible origins for the pits include removal of dust or sand by wind and/or sublimation of ice from the near subsurface. The picture covers an area 3 kilometers (1.9 miles) wide and is illuminated from the left.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
March 1999--it is summer in the martian northern hemisphere, yet patches of frost or snow persist in some areas of the northern plains. Winter ended eight months earlier, in July 1998. Recently, the Mars Orbiter Camera (MOC) passed over a relatively small impact crater located at latitude 68°N (on the Vastitas Borealis plain, north of Utopia Planitia) and took the picture seen at the left, above. The curved crater rims are visible in the upper and lower quarters of the image, and the crater floor is visible at the center right.
The picture on the right is a magnified view of the crater rim area outlined by a white box in the image on the left. The bright patches are snow or frost left over from the martian winter. These snowfields are so small that a human could walk across one of them in a matter of minutes--or perhaps sled down the small, sloping patch that is seen in a shadowed area near the lower left.
In winter, the entire scene shown here would be covered by frost. The long strip at the left covers an area 3 km (1.9 mi) wide by 26 km (16 mi) long. The expanded view on the right covers an area 2.9 km (1.8 mi) by 5.3 km (3.3 mi). Illumination is from the upper right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
4 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark streaks created by dust devils on a plain southwest of Hellas Planitia. Based on the width and the length of individual streaks in this scene, it is clear that not all dust devils are created equally.
Location near: 55.8°S, 317.5°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
This recent Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows mesas and smaller buttes that occur on the Elysium Plains, approximately 300 kilometers (~185 miles) south of the Cerberus region in the Martian eastern hemisphere.
Like the world-famous Monument Valley located in the Navajo Nation on the border of Arizona and Utah, this "Martian Monument Valley" consists of a series of mesas and buttes that have formed by erosion of layered bedrock. The uneroded rock forms a flat upland at the top of the image. The number of mesas and buttes decreases toward the bottom of the image, but their presence indicates that the rock in which they formed was once more extensive and covered the entire scene. Small dunes form parallel ridges on the lowland between many of the mesas near the top of the image. The image covers an area that is 3 kilometers (1.9 miles) wide and is illuminated from left.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
The above figure shows the location of all high resolution (narrow angle) MOC images of the Cydonia region that have been obtained to date, including the first three taken in 1998 (PIA01240, PIA01241, AND PIA01440). These images are superimposed upon a mosaic of Viking images taken during the 1970's. Images acquired during the Science Phasing Orbit period of 1998 slant from bottom left to top right; Mapping Phase images (from 1999 and 2000) slant from lower right to upper left. Owing to the nature of the orbit, and in particular to the limitations on controlling the location of the orbit, the longitudinal distribution of images (left/right in the images above) is distinctly non-uniform. An attempt to take a picture of a portion of the "Face" itself in mid-February 2000 was foiled when the MGS spacecraft experienced a sequencing error and most of that day's data were not returned to Earth. Only the first 97 lines were received; the image's planned footprint is shown as a dashed box. This image is one in a series of eight.
Voir l'image PIA02387: Cydonia: Two Years Later sur le site de la NASA.
Some martian sand dunes may be more active than others. In this picture, wind has caused the dark and somewhat crescent-shaped dunes to advance toward the lower left. While their movement cannot actually be seen in this April 1998snapshot, the location of their steepest slopes--their slip faces--on their southwestern sides indicates the direction of movement. Oddly, these dark dunes have moved across and partly cover sets of smaller, bright ridges that also formed by wind action.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image illustrates an intriguing martian "find." Strangely, the two dune types have different shapes and a different relative brightness. There are two explanations for the relationship seen here, and neither can be distinguished as "the answer"--(1) it is possible that the brighter dunes are old and cemented, and represent some ancient wind activity, whereas the dark dunes are modern and are marching across the older, "fossilized" dune forms, or (2) the bright dunes are composed of grains that are much larger or more dense than those that compose the dark dunes. In the latter scenario, the bright dunes move more slowly and are over-taken by the dark dunes because their grains are harder to transport. An interpretation involving larger or denser grains is consistent with the small size and even-spacing of the bright dunes, as well, but usually on Earth such features occur on the surfaces of larger, finer-grained dunes, not under them. The actual composition of either the bright or dark materials are unknown. This example is located on the floor of an impact crater in western Arabia Terra at 10.7°N, 351.0°W. The picture is illuminated from the right.
Voir l'image PIA02356: Dark Dunes Over-riding Bright Dunes sur le site de la NASA.
These pictures compare an image of wind features on a lava field on Mars with similar features on a lava field in southern California. The first picture (above, left) shows that the martian example occurs in western Daedalia Planum, a region covered by long, dark-toned lava flows southwest of Arsia Mons, the southernmost of the three large Tharsis Montes. The second picture (above, center) is Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image no. AB1-10905. It was acquired on January 29, 1998. What struck the MOC Science Team as most exciting about this image was that the relationship between lava flows, bright windblown sediment, and dark wind tails behind craters in AB1-10905 reminded them of a similar scene near Amboy, California, in the Mojave Desert (above, right).
Based upon observations of Daedalia Planum from the Viking orbiters in the late 1970s, it has been assumed for 20 years that most of Daedalia Planum is a lava flow field that is mantled by bright dust. However, the similarity to the Amboy lava field in California has caused some scientists to re-think the situation on Mars. Instead of bright dust, it now appears that bright sand might be present in this portion of Daedalia Planum.
What's the difference between dust and sand? Observations from the Viking and Mars Pathfinder landers have suggested that martian dust consists of very, very tiny particles of less than 10 micrometers (less than 1/10th the width of a human hair). Sand, on the other hand, is defined by sedimentologists as consisting of particles with sizes in the range 62.5 to 2000 micrometers(2000 micrometers is 2 millimeters, or about 8-hundredths of an inch). In the martian environment, sand moves close to the ground by bouncing and hopping when strong enough gusts of wind come along, this is called saltation. Dust, on the other hand, gets picked up by the wind and travels by being suspended in the air. When dust settles back to the ground, it forms a coating that blankets surfaces in a fairly uniform manner, whereas sand makes drifts, tails, and streaks as it interacts with obstacles such as craters, hills, and the lumpy surfaces of lava flows.
At the Amboy lava field in California, bright sand is being blown across the dark lava from adjacent dry streambeds. When this sand encounters a volcanic cinder cone that rises above the lava field (pictures "B" and "D" in the above, right figure), the sand is deflected around the cone and leaves a dark "shadow" in which very little bright sand gets deposited. A similar situation is seen with respect to craters formed by meteor impact in the Daedalia Planum image AB1-10905 (pictures "A" and "C" in the above, right figure). The spectacular Amboy wind streak, lava flows, and cinder cone can often be seen from an airplane by passengers flying into or out of Los Angeles International Airport (LAX) from points east such as Denver, Colorado.
MOC image AB1-10905 is illuminated from the left. The Amboy lava flows and cinder cone volcano are illuminated from the lower right. The Amboy photographs were taken from an airplane and are from the U.S. Geological Survey. Wind has blown material from right to left in the MOC image, and from upper left toward lower right in the Amboy pictures. North is up in all figures.
For a higher-resolution view of the AB1-10905 MOC image (2.4 MBytes), CLICK HERE.
Voir l'image PIA02363: Wind Streaks of Daedalia, Mars, and Amboy, California sur le site de la NASA.
Boulders are one of the keys to determining which processes have eroded, transported, and deposited material on Mars (e.g.,landslides, mud flows, flood debris). During the first year in orbit,MGS MOC obtained pictures with resolutions between 2 and 30 meters (7to 98 feet) per pixel. It was found that boulders are difficult to identify on Mars in images with resolutions worse than about 2-3 meters per pixel. Although not known when the MOC was designed,"thresholds" like this are found on Earth, too. The MOC's 1.5 m/pixel resolution was a compromise between (1) the anticipation of such resolution-dependent sensitivity based on our experience with Earth and (2)the cost in terms of mass if we had built a larger telescope to get a higher resolution.
Some rather larger boulders (i.e., larger than about 10 meters--or yards--in size) have already been seen on Mars by the orbiting camera. This is a feat similar to that which can be obtained by "spy" satellites on Earth. The MOC image 53104 subframe shown above features a low, rounded hill in southeastern Utopia Planitia. Each of the small, lumpy features on the top of this hill is a boulder. In this picture, boulders are not seen on the surrounding plain. These boulders are interpreted to be the remnants of a layer of harder rock that once covered the top of the hill, but was subsequently eroded and broken up by weathering and wind processes.
MOC image 53104 was taken on September 2, 1998. The subframe shows an area 2.2 km by 3.3 km (1.4 miles by 2.7 miles). The image has a resolution of about 3.25 meters (10.7 feet) per pixel. The subframe is centered at 41.0°N latitude and 207.3°W longitude.(CLICK HERE for a context image). North is approximately up, illumination is from the left.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01500: Mars Boulders: On a Hill in Utopia Planitia sur le site de la NASA.
Some craters in the middle latitudes of Mars exhibit strange, concentric- and radial-textured patters on their floors--as seen here. The origin is presently unknown. This crater is in northern Arabia Terra, and the picture was taken in April 1998.
Valles Marineris was first observed in 1972 by the Mariner 9 spacecraft, from which the troughs get their name: Valles--valleys, Marineris--Mariner.
Some hints of layering in both the canyon walls and within some deposits on the canyon floors were seen in Mariner 9 and Viking orbiter images from the 1970s. The Mars Orbiter Camera on board Mars Global Surveyor has been examining these layers at much higher resolution than was available previously.
MOC images led to the realization that there are layers in the walls that go down to great depths. An example of the wall rock layers can be seen in MOC image 8403, shown above (C).
MOC images also reveal amazing layered outcrops on the floors of some of the Valles Marineris canyons. Particularly noteworthy is MOC image 23304 (D, above), which shows extensive, horizontally-bedded layers exposed in buttes and mesas on the floor of western Candor Chasma. These layered rocks might be the same material as is exposed in the chasm walls (as in 8403--C, above), or they might be rocks that formed by deposition (from water, wind, and/or volcanism) long after Candor Chasma opened up.
In addition to layered materials in the walls and on the floors of the Valles Marineris system, MOC images are helping to refine our classification of geologic features that occur within the canyons. For example, MOC image 25205 (E, above), shows the southern tip of a massive, tongue-shaped massif (a mountainous ridge) that was previously identified as a layered deposit. However, this MOC image does not show layering. The material has been sculpted by wind and mass-wasting--downslope movement of debris--but no obvious layers were exposed by these processes.
Valles Marineris a fascinating region on Mars that holds much potential to reveal information about the early history and evolution of the red planet. The MOC Science Team is continuing to examine the wealth of new data and planning for new Valles Marineris targets once the Mapping Phase of the Mars Global Surveyor mission commences in March 1999.
This image: Layers in western Candor Chasma northern wall. MOC image 8403 subframe shown at full resolution of 4.6 meters (15 feet) per pixel. The image shows an area approximately 2.4 by 2.5 kilometers (1.5 x 1.6 miles). North is up, illumination is from the left. Image 8403 was obtained during Mars Global Surveyor's 84th orbit at 10:12 p.m. (PST) on January 6, 1998.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01458: Western Candor Chasma, Valles Marineris sur le site de la NASA.
Newton Crater is a large basin formed by an asteroid impact that probably occurred more than 3 billion years ago. It is approximately 287 kilometers (178 miles) across. The picture shown here (top) highlights the north wall of a specific, smaller crater located in the southwestern quarter of Newton Crater (above). The crater of interest was also formed by an impact; it is about 7 km (4.4 mi) across, which is about 7 times bigger than the famous Meteor Crater in northern Arizona in North America.
The north wall of the small crater has many narrow gullies eroded into it. These are hypothesized to have been formed by flowing water and debris flows. Debris transported with the water created lobed and finger-like deposits at the base of the crater wall where it intersects the floor (bottom center top image). Many of the finger-like deposits have small channels indicating that a liquid--most likely water--flowed in these areas. Hundreds of individual water and debris flow events might have occurred to create the scene shown here. Each outburst of water from higher upon the crater slopes would have constituted a competition between evaporation, freezing, and gravity.
The individual deposits at the ends of channels in this MOC image mosaic were used to get a rough estimate of the minimum amount of water that might be involved in each flow event. This is done first by assuming that the deposits are like debris flows on Earth. In a debris flow, no less than about 10% (and no more than 30%) of their volume is water. Second, the volume of an apron deposit is estimated by measuring the area covered in the MOC image and multiplying it by a conservative estimate of thickness, 2 meters (6.5 feet). For a flow containing only 10% water, these estimates conservatively suggest that about 2.5 million liters (660,000 gallons) of water are involved in each event; this is enough to fill about 7 community-sized swimming pools or enough to supply 20 people with their water needs for a year.
The MOC high resolution view is located near 41.1°S, 159.8°W and is a mosaic of three different pictures acquired between January and May 2000. The MOC scene is illuminated from the left; north is up. The context picture was acquired in 1977 by the Viking 1 orbiter and is illuminated from the upper right.
Voir l'image PIA01039: Evidence for Recent Liquid Water on Mars: Channeled Aprons in a Small Crater within Newton Crater sur le site de la NASA.
27 February 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered buttes, knobs, and other landforms exposed by erosion in the Aeolis region of Mars.
Location near: 6.3°S, 208.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
Another spring has "sprung" in the northern hemisphere of Mars! Northern spring began in June 2000, and as we approach August 2000, sunlight is now illuminating most of the north polar cap each day. This is the second northern spring that MOC has viewed--we've now seen, in selected areas, a full Mars year of atmospheric and surface conditions. Although the pictures do not cover the exact same area, pictures from exactly two Earth years ago (26 July 1998) show very similar features in the north circum-polar dune field (see Spring Time View of North Polar Sand Dunes).
At this time, frost left-over from the recent winter is slowly subliming away to expose underlying northern plains and sand dune surfaces. The picture above shows a frost-covered portion of the vast dune fields that surround the north polar cap as they appeared on July 22, 2000. In summer, the dunes are dark, but in winter and early spring they are covered with bright frost. Small dark spots and streaks indicate areas where the frost has begun to disappear. This Mars Global Surveyor Mars Orbiter Camera image covers an area 2.3 km (1.4 mi) wide by 7.7 km (4.8 mi) long near 78°N, 107°W and is illuminated from the lower left.
Voir l'image PIA01045: Frosted North Polar Sand Dunes in Early Spring sur le site de la NASA.
How can martian gullies--thought to be caused in part by seepage and runoff of liquid water--be distinguished from the more typical, "dry" slope erosion processes that also occur on Mars? For one thing, most--though not all--of the gully landforms occur on slopes that face away from the martian equator and toward the pole. For another, slopes that face toward the equator exhibit the same types of features as seen on nearly every other non-gullied slope on Mars.
The example shown here comes from northwestern Elysium Planitia in the martian northern hemisphere. The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) high resolution view (A, left) shows a portion of a 10 kilometer-(6.2 mi)-diameter meteor impact crater at a resolution of about 9 meters (29.5 ft) per pixel. The crater is shown in the context image (B, middle). The north-facing (or, pole-ward) slope in the MOC view is shadowed because sunlight illuminates the scene from the lower left. In this shadowed area, a series of martian gullies--defined by their erosional alcoves, deep channels, and apron deposits--are seen. On the sunlit south-facing (or equator-ward) slope, a scene more typical of most martian impact craters is present--the upper slopes show layered bedrock, the lower slopes show light-toned streaks of dry debris that has slid down the slope forming talus deposits that are distinctly different from the lobe-like form of gully aprons. The picture in (C) has been rotated so that the two slopes--one with gullies (right) and one without (left)--can be compared.
The crater is located at 36.7°N, 252.3°W. The MOC image was acquired in November 1999 and covers an area 3 km (1.9 mi) wide by 14 km (8.7 mi) long; north is toward the upper right (in A) and it is illuminated by sunlight from the lower left. The Viking 1 orbiter context image (B) was obtained in 1978 and is illuminated from the left; north is up. The MOC image has been rotated in the Explanatory Figure (C) such that north is toward the upper left, illumination is from the lower right.
Voir l'image PIA01042: Evidence for Recent Liquid Water on Mars: "Dry" Processes on One Slope; "Wet" Processes on Another sur le site de la NASA.
Over the past six months, the southern hemisphere of Mars has passed through spring and into summer. Spring started in early August 1999 and summer arrived toward the end of December 1999. Mars Global Surveyor (MGS) is in a polar orbit, thus the spacecraft's Mars Orbiter Camera (MOC) has had an excellent view of the daily changes that have occurred as the south polar frosts sublimed away during spring and into the summer season.
Shown here are three views of the same portion the layered terrain near the martian south pole. Together, these three views document changes that occurred between August 1999 and February 2000 for the same small region. Each view is 3 kilometers(1.9 miles) wide. The differences in orientation of the surface features are caused by the fact that the MGS did not pass directly over the exact same spot in each view. Each view is illuminated by sunlight from the lower right. The wavey, almost parallel lines in the upper half of each picture are exposed layers of the south polar "layered terrain."
As the terrain began to defrost in early August 1999, dark spots appeared. Wind occasionally picks up some of the dark material and blows it across the landscape, creating dark streaks. By late September, much of the scene is covered with these dark spots and narrow, dark wind streaks. By February, all of the frost and dark spots were gone, revealing the underlying layered terrain surface.
Based upon the extremely cold temperatures measured by the MGS Thermal Emission Spectrometer (TES) during southern spring at 87°S latitude, the frost seen in the left and middle pictures are probably composed mostly of frozen carbon dioxide--known on Earth as "dry ice." The 1 km scale bar is also equivalent about 0.62 miles; the arrow indicates the general direction of north.
Voir l'image PIA02364: A High-Resolution Look at the Spring Thaw of the Martian South Polar Cap sur le site de la NASA.
Portion of dissected terrain southeast of Parana Valles (MOC 7705). This heavily gullied landscape (25.9°S, 8.3°W) shows the highest "drainage density" yet seen in MOC images. This image is somewhat lower in resolution (downtrack scale = 21.4 m/pixel, crosstrack = 14.3 m/pixel) but in other parameters comparable to Figures 1 and 2 (incidence angle = 27.5°, emission angle = 14.5°).
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01507: Dissected Terrain Near Parana Valles sur le site de la NASA.
The northern plains of Mars exhibit craters that often appear to be partly buried by or exhumed from beneath layers of pitted and eroded material. This example was taken by MOC in August 1998.
Mars Global Surveyor passes over the north polar region of the red planet twelve times each day, offering many opportunities to observe how the polar cap frosts and dunes are changing as the days goby. Right now it is summer in the north. This picture, taken the second week of April 1999, shows darks and dunes and remnant patches of bright frost left over from the winter that ended in July 1998. Dark streaks indicate recent movement of sand. The picture covers an area only 1.4 kilometers (0.9 miles) across and is illuminated from the upper right.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02001: Polar Dunes In Summer Exhibit Frost Patches, Wind Streaks sur le site de la NASA.
Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01168: Layers within the Valles Marineris: Clues to the Ancient Crust of Mars - High Resolution Image sur le site de la NASA.
Elysium Mons was discovered by Mariner 9 in 1972. It differs in a number of ways from the familiar Olympus Mons and other large volcanoes in the Tharsis region. In particular, there are no obvious lava flows visible on the volcano's flanks. The lack of lava flows was apparent from the Mariner 9 images, but the new MOC high resolution image--obtained at 5.24 meters (17.2 feet) per pixel--illustrates that this is true even when viewed at higher spatial resolution.
Elysium Mons has many craters on its surface. Some of these probably formed by meteor impact, but many show no ejecta pattern characteristic of meteor impact. Some of the craters are aligned in linear patterns that are radial to the summit caldera--these most likely formed by collapse as lava was withdrawn from beneath the surface, rather than by meteor impact. Other craters may have formed by explosive volcanism. Evidence for explosive volcanism on Mars has been very difficult to identify from previous Mars spacecraft images. This and other MOC data are being examined closely to better understand the nature and origin of volcanic features on Mars.
The three MOC images, 40301 (red wide angle), 40302 (blue wide angle), and 40303 (high resolution, narrow angle) were obtained on Mars Global Surveyor's 403rd orbit around the planet around 9:58 - 10:05 p.m. PDT on July 2, 1998. The images were received and processed at Malin Space Science Systems (MSSS) around 4:00 p.m. PDT on July 4, 1998.
This image: MOC image 40303 subframe of the Elysium Mons' southern caldera wall and floor shown at full resolution (5.24 meters (17.2 feet) per pixel). Illumination is from the right, north is approximately up.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA01456: Elysium Mons Volcano - Detail of Southern Caldera Wall and Floor sur le site de la NASA.
Nirgal Vallis is an ancient valley thought for nearly 3 decades to have been carved, in part, by running water at some time far back in the martian past. Today the valley is, like the rest of Mars, quite dry. However, some of the high resolution Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images reveal small gullies on the walls of this valley system. An example is shown here (above, left), in which more than 14 channels nearly 1 kilometer (0.6 miles) long run down the south-facing slope of the Nirgal Vallis wall. Each narrow channel starts at about the same position below the top of the valley wall, indicating that there is a layer along which a liquid--most likely, water--has percolated until it reached the cliff, then ran down hill to form the channels and the fan-shaped aprons at the bottom of the slope. Some of the apron deposits seem to cover the dunes on the floor of the valley (lower 1/3 of the image), suggesting that the channels and aprons formed more recently than the dunes. The fact that neither the dunes nor the aprons and channels have impact craters on them suggests that these features are all geologically young, meaning a few million years at most, a few days or weeks at least.
Nirgal Vallis is the one location where martian gullies thought to be related to recent groundwater seepage have been found closer to the equator than 30° latitude. All of the features in Nirgal, however, occur close to 30°--they are all between 27°S and 30°S. The MOC image is near 29.7°S, 38.6°W, and was obtained July 12, 1999. The MOC picture covers an area approximately 2.3 km (1.4 mi) wide by 2.8 km (1.7 mi) long. Sunlight illuminates the MOC scene from the upper left, and north is up. The context view (right) is a mosaic of Viking orbiter images illuminated from the upper right from the U.S. Geological Survey Mars Digital Mosaic maps. The small white box in the context frame (just below center of image) shows the location of the high resolution MOC view.
It is ironic to note that one of the first pictures returned to Earth from MOC, back on September 21, 1997, showed similar small channels and aprons on the wall of Nirgal Vallis--but their significance was not realized at the time.
Voir l'image PIA01037: Evidence for Recent Liquid Water on Mars: South-facing Walls of Nirgal Vallis sur le site de la NASA.
This figure shows a comparison at the same scale (about 5 meters--16 feet--per pixel) of the 1997 Mars Pathfinder landing site (left) and a representative portion within the primary landing ellipse designated for the Mars Polar Lander (right). Familiar landmarks at the Mars Pathfinder site include the "Twin Peaks" (center left), "North Peak" (top), and "Big Crater" (lower right). The south polar layered deposits are generally devoid of the large craters and hills seen at the Pathfinder site. The "wavey" texture at the Pathfinder site (the result of the movement of sediment by the large flood that swept through that location billions of years ago) is replaced at the proposed Mars Polar Lander site by a random arrangement of very low ridges and grooves that suggest the surface has been exposed to erosion by ablation of ices. When the picture on the right was taken, the surface was still mostly covered by winter-time carbon dioxide frost. However, as the sun rises higher, the carbon dioxide frost sublimes (goes directly from solid to vapor), creating the dark spots that are just barely visible in this image. Illumination is from the lower right in both pictures.
For pictures showing the location of Mars Pathfinder, Click HERE.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Voir l'image PIA02311: Mars Polar Lander and Mars Pathfinder Sites Compared sur le site de la NASA.
20 November 2006
Crisp details in a suite of mid-latitude gullies on a crater wall are captured in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view obtained in southern winter on 12 October 2006. During southern winter, shadows are more pronounced and the atmosphere is typically quite clear. These gullies, which may have formed in relatively recent martian history by erosion caused by flowing, liquid water, are located in a crater on the east rim of Newton Crater near 40.4°S, 155.3°W. Sunlight illuminates the scene from the upper left. The picture covers an area about 3 km (1.9 mi) wide; the crater rim is on the right side of the image, the crater floor is on the left. North is toward the top/upper left.
