This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows the wall of a trough in the Zephyrus Fossae region, west of the Elysium Rise near 27.9°N, 217.5°W. The trough wall has cut through and exposed layered bedrock, visible near the top of the wall. Talus covers the lower portions of the wall; this debris includes many automobile- and house-sized boulder--most of which are seen as dark dots at the base of the slope. Dust has coated and mantled much of this terrain, including some of the boulders. The dark streak near the center of the picture was formed by landsliding (or avalanching) of some of the dust. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04525: Layers, Boulders, and Dust sur le site de la NASA.
22 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark teardrop-shaped sand dunes in eastern Copernicus Crater. The winds responsible for these dunes generally blow from the south-southwest (lower left).
Location near: 48.7°S, 167.4°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
28 May 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark slope streaks coming down the slopes of a knob in western Amazonis Planitia. All of the surfaces in this image are mantled by dust. On the slopes, mass movement of dry dust has created the streaks.
Location near: 19.6°N, 166.1°W
Image width: ~3 km (~1.9 mi
Illumination from: lower left
Season: Northern Autumn
When spring comes to the southern hemisphere of Mars, dark spots begin to form on sand dunes covered with carbon dioxide frost. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dune field near 61.8°S, 160.5°W in early spring. The processes that form the dark spots remain mysterious. The spots might form at the locations of the thinnest frost, the coarsest sand grains, or at interfaces between two different types of material surfaces (e.g., between dune and surrounding plain). The area shown here is illuminated from the upper left and covers an area 3 km (1.9 mi) wide.
Voir l'image PIA04588: Defrosting Sand Dunes sur le site de la NASA.
5 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an impact crater in the volcanic Tharsis region of Mars. The margins of a lava flow are seen to the north (above) the crater.
Location near: 22.2°N, 114.2°W
Image width: ~3 km (~1.9 mi
Illumination from: lower left
Season: Northern Autumn
12 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark squiggles and streaks created by passing spring and summer dust devils near Pallacopas Vallis in the martian southern hemisphere.
Location near: 53.9°S, 17.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
18 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the east margin of a landslide off the southern rim of Mutch Crater in the Xanthe Terra region of Mars. This particular landslide was likely triggered by a meteor impact that occurred nearby.
Location near: 0.7°S, 55.9°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
One objective for the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in the Extended Mission is to continue looking for changes and dynamic events taking place on the red planet. The feature shown here elicited gasps of excitement among the MOC Operations Staff when it was received in early April 2001.
The feature is a dust devil. 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. When this dust devil was spied in Amazonis Planitia on April 10th, the MOC was looking straight down. Usually when the camera is looking down the dust devil will appear as a circular, fuzzy patch with a straight shadow indicating its columnar shape. In this case, however, the dust devil is somewhat curved and kinked--its shape is best seen in the shadow it casts to the right. A thin, light-toned track has been left by the dust devil as it moved eastward across the landscape. Usually, such tracks are darker than the surroundings, in this case the light tone might indicate that the dust being removed by the passing dust devil is darker than the surface underneath the thin veneer of dust.
Dust devils most typically 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. This dust devil occurred at an optimal time for dust devils whether on Earth or Mars--around 2 p.m. local time in the middle of Northern Hemisphere Summer. North is up, sunlight illuminates the scene from the left (west), and 500 meters is about 547 yards. The shadow cast by the dust devil goes off the edge of the image, but the length shown here (about 1.5 km) indicates that the dust devil was a bit more than 1 km (0.62 mi) in height.
Voir l'image PIA03223: A Mid-Summer's Dust Devil sur le site de la NASA.
Since the initial discovery of scarp retreat in the south polar cap in August 2001, MOC Extended Mission operations have included observation of many changes that occurred since 1999, and acquisition of new data to see how the cap changes from Spring in late 2001 through Summer in early 2002. Additional images have been obtained to help document changes when the polar cap returns to Spring in 2003.
Previous releases regarding changes in south polar cap Carbon Dioxide landforms:
MOC Observes Changes in the South Polar Cap: Evidence for Recent Climate Change on Mars: PIA03179 MOC View of the Martian South Polar Residual Cap: PIA03180
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 PIA03471: Changes in South Polar Carbon Dioxide Ice Cap sur le site de la NASA.
The vast plains of Mars located south of Cerberus and the Elysium volcanoes have a platy, textured surface thought to have formed by floods of thick mud or, more likely, very fluid lava. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows that the platy plain--which is the darker surface covering most of the northern two-thirds of this picture--is being exhumed from beneath a brighter material. The small ridges in the bright material are yardangs, a landform created by wind erosion. Wind is slowly eroding the bright material away, revealing the darker, platy surface below. This area is located near 4.3°N, 208.5°W. Sunlight illuminates the scene from the left/lower left.
Voir l'image PIA04550: Exhuming Platy Plains sur le site de la NASA.
In planetary science, impact craters are "tools of the trade." They are common to all of the solid-surfaced objects in our Solar System, and are thus a good point of reference to compare different planetary bodies. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a crater that is about the same size as the famous Meteor Crater in northern Arizona, on the North American continent. This crater, however, is on the floor of the caldera--a large volcanic/collapse crater--of a giant martian volcano, Arsia Mons. This crater formed in volcanic rock, whereas the one in Arizona formed in sedimentary rock. Large, house-sized boulders dot the raised crater rim. This image is near 10.0°S, 120.4°W. The picture is illuminated from the left.
Voir l'image PIA04581: Impact on Arsia Mons sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the "swiss cheese" pattern of frozen carbon dioxide on the south polar residual cap. Observation of these materials over two Mars years has revealed that the scarps that bound the mesas and small buttes are retreating-the carbon dioxide ice is subliming away-at a rate of about 3 meters (3 yards) per Mars year in some places. The picture covers an area about 900 m (about 900 yards) wide near 87.1°S, 93.7°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04474: South Polar Ice Cap sur le site de la NASA.
18 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.5 meters per pixel view of gullies formed in material on the walls of an impact crater in the martian southern hemisphere. A liquid, laden with debris, poured down these slopes to form the gullies. Gully erosion cut through a thick mantle that covers the original crater wall, and then cut into the old wall itself. The source of the liquid might have been within the layered material exposed in the crater walls.
Location near: 46.6°S, 151.8°W
Image width: ~2 km (~1.2 mi)
Illumination from: upper left
Season: Southern Spring
11 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, layered, sedimentary rock exposures in western Candor Chasma, part of the vast Valles Marineris trough system. Most of west Candor's interior includes exposures of layered rock with very few superimposed impact craters. The rock may be very ancient, but the lack of craters suggests that the erosion of these materials is on-going.
Location near: 6.3°S, 76.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Summer
14 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of the famous "White Rock" feature in Pollack Crater in the Sinus Sabaeus region of Mars. The light-toned rock is not really white, but its light tone caught the eye of Mars geologists as far back as 1972, when it was first spotted in images acquired by Mariner 9. The light-toned materials are probably the remains of a suite of layered sediments that once spread completely across the interior of Pollack Crater. Dark materials in this image include sand dunes and large ripples.
Location near: 8.1°S, 335.1°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Summer
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture obtained in March 2003 shows dark-toned buttes of possible sedimentary rock in southern Melas Chasma. These buttes are remnants of a layer or sequence of layers that once covered this portion of the chasm floor. The buttes are located near 11.4°S, 75.1° W. Sunlight illuminates the scene from the upper right.
Voir l'image PIA04473: Buttes in Melas Chasma sur le site de la NASA.
7 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes on the floor of a southern mid-latitude impact crater. Craters are commonly the site of sand dunes, as sand may become trapped in these topographic depressions. In this case, the winds responsible for the dunes generally blew from the south/southeast (bottom/lower right),
Location near: 51.8°S, 105.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
Although northern plains are often called "flat" or "featureless" by people who study altimetry data, clearly this isn't true. This area has an indurated (strong or cemented) crust that has been subjected to directional stress (that's why the beaded-pitted fractures are almost all aligned the same direction) and that has been undermined (hence the pitting at both the small scale--the beaded fractures--and the large scale--the large irregular depressions.
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 PIA03174: Fractures/Pits in Northern Plains (Utopia Plains: 44.9 N, 274.7 W) sur le site de la NASA.
25 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dust-covered landscape in northern Tharsis, including several troughs formed by faults as the crust in the region expanded, long ago.
Location near: 25.8°N, 98.2°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season Northern Autumn
20 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a wind streak formed in the lee of an impact crater in western Daedalia Planum.
Location near: 12.7°S, 136.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
18 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows channels carved by catastrophic floods in the Tharsis region of Mars. This area is located northwest of the volcano, Jovis Tholus, and east of the large martian volcano, Olympus Mons. The terrain is presently mantled with fine dust.
Location near: 10.5°N, 203.4°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
Mars Global Surveyor orbits the red planet 12 times each day. Half of each orbit is spent on the day side of Mars, which is where most Mars Orbiter Camera (MOC) images are obtained because sunlight is required to illuminate the surfaces being observed. However, on the night side of Mars, the wide angle cameras can see clouds and hazes above the sunward martian limb. The limb is the edge of the planet as it appears when viewed from an oblique perspective.
This blue wide angle camera image, obtained on the night side of Mars on May 15, 2003, shows clouds picking up the first sunlight before dawn near 55° north latitude. The scene is illuminated by sunlight from the right. The sun is actually on the other side of the planet, and has not yet risen over this region. The dark area on the left side of the picture is the martian surface at night. The dark band on the right side is outer space. The bright features just right of center are the clouds hanging above the martian limb over the planet's northern plains. North is toward the top and east is to the right; the spacecraft was moving southward when the image was acquired.
Voir l'image PIA04562: Clouds Over Morning Limb sur le site de la NASA.
18 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a few dark wind streaks in the lee -- the downwind side -- of shallow craters on a lava- and dust-covered plain in eastern Tharsis. Streaks in east Tharsis, such as these, are usually very superficial features that change on timescales as quickly as a few weeks to months as very thin coatings of dust are redistributed by the wind.
Location near: 2.4°N, 95.6°W
Image width: ~1 km (~0.6 mi)
Illumination from: lower left
Season: Northern Winter
Small ridges known as yardangs in the upper left quarter of this April 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image indicate that wind has stripped away a mantling layer of sediment to reveal the terrain beneath. Layers and boulders on the cliff face near the south-center of the image show that the substrate is quite competent; its location southwest of Olympus Mons near Gordii Dorsum suggests the bedrock here may include old lava flows. The picture is located near 4.8°N, 142.7°W. Sunlight illuminates the scene from the left/lower left.
Voir l'image PIA04565: Terrain Near Gordii Dorsum sur le site de la NASA.
28 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows low-albedo sand dunes in Herschel Crater in the Mare Cimmerium region of the martian southern hemisphere. Winds responsible for these dunes generally blow from the north (top).
Location near: 14.5°S, 231.7°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Summer
At the center of this February 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is a pattern of branching channels in an apron of debris that distributed the sediment and fluid carried by the large gully below (to the south) of them. The slope decreases from the bottom toward the top of the image-that is, everything is downhill from the bottom to the top. Middle- and polar-latitude gullies were first discovered in MOC images and reported in June 2000. The distributing channels found in this gully apron are a good indicator that the fluid responsible for the gully and distributary channels had properties like that of liquid water. However, of course, the exact nature of the fluid is unknown, because it is no longer present. This picture is located near 47.8°S, 355.6°W. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04519: Distributary Channels sur le site de la NASA.
Each spring as the sun comes up over the polar regions, the seasonal frosts that have accumulated there during winter begin to sublime away. Dunes are among the first features to show spots and streaks resulting from the defrosting process. Unknown is whether the dark spots and streaks are sand (from the dune) that has been mobilized by wind, or frost that has become disrupted and coarse-grained (coarse grains of ice can look darker than fine grains). This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows north polar dunes near 76.6°N, 255.9°W in early spring. The image, acquired in June 2002, is 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04052: Defrosting North Polar Dunes sur le site de la NASA.
4 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small landslide off a steep slope in southwestern Ophir Chasma.
Location near: 4.6°S, 72.8°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
Whether on Earth or Mars, sedimentary rocks provide a record of past environments. Of course, it is difficult to read that record without being able to visit the site. However, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has revealed hundreds of locales on Mars at which sedimentary rocks are exposed at the surface. Terby Crater exhibits hundreds of layers of similar thickness and physical properties--some have speculated these may be the record of an ancient lake or sea. This MOC image shows some of the layer outcrops in Terby Crater. Fans of debris have eroded from the steep, layered slopes in some places. This picture covers an area 3 km (1.9 mi) wide near 27.5°S, 285.7°W. The image is illuminated from the upper left and was obtained in June 2003.
Voir l'image PIA04600: Layers in Terby Crater sur le site de la NASA.
Mars is a dynamic planet. This pair of Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) pictures, taken 2 Mars years apart, show changes in dark streak patterns caused by wind movement of dust. The top picture was taken in July 1999, the bottom one in March 2003. The pair of images are in Tharsis near 9.5°S, 128.5°W. Sunlight illuminates both from the upper left.
Voir l'image PIA04517: Wind Streak Changes sur le site de la NASA.
27 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, layered rock outcrops found in eastern Candor Chasma, part of the vast Valles Marineris trough system. Rocks such as these have been known to occur in the Valles Marineris since the 1971-1972 Mariner 9 mission. Whether they formed in rock that was exposed by the opening (by faulting) of the Candor Chasma trough, or formed in the trough after it was formed, is a matter of on-going debate and discussion within the Mars science community.
Location near: 6.3°S, 69.3°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
27 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows classic yardangs, landforms created by wind erosion in southern Amazonis Planitia. The boat-shaped mesa, in particular, is a classic example of a yardang landform. Yardangs are found on both Earth and Mars.
Location near: 11.2°N, 162.2°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season Northern Autumn
Toward the end of its Primary Mapping Mission, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) acquired one of its most spectacular pictures of layered sedimentary rock exposed within the ancient crater Becquerel. Pictures such as this one from January 25, 2001, underscore the fact that you never know from one day to the next what the next MOC images will uncover. While the Primary Mission ends January 31, 2001, thousands of new pictures--revealing as-yet-unseen terrain on the red planet--may be obtained during the Extended Mission phase, scheduled to run through at least April 2002.
The picture shown here reveals hundreds of light-toned layers in the 167 kilometers (104 miles) wide basin named for 19th Century French physicist Antoine H. Becquerel (1852-1908). These layers are interpreted to be sedimentary rocks deposited in the crater at some time in the distant past. They have since been eroded and exposed, revealing faults, dark layers between the bright layers, and a long geologic history (of unknown duration) recorded in these materials. Sets of parallel faults can be seen cutting across the layers in the left third of the image. Sunlight illuminates this scene from the top/upper right.
Voir l'image PIA03211: Spectacular Layers Exposed in Becquerel Crater sur le site de la NASA.
2 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.4 meters per pixel (~5 ft/pixel) view of an eroded landscape north of the crater, Antoniadi, in far eastern Arabia Terra. Each knob and butte in this image is a remanant of a formerly more-extensive layered rock unit that has been largely eroded away.
Location near: 84.2°S, 138.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season Southern Spring
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered sedimentary rock outcrops in Becquerel Crater of western Arabia Terra. These materials were deposited in the crater some time in the distant past, and later eroded to their present form. They probably consist of fine-grained sediments; they could have been deposited directly from dust and/or volcanic ash settling out of the martian atmosphere, or silt and sand settling to the floor of an ancient lake. The image does not provide enough information to distinguish between the two possibilities. The picture is located near 21.5°N, 8.1°W. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04501: Becquerel Layers sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a "text-book example" of an offset in layered rock caused by a fault. The offset is most easily seen near the upper right of the image. The martian crust is faulted, and the planet has probably experienced "earthquakes" (or, marsquakes) in the past. This scene is located on the floor of Ius Chasma near 7.8°S, 80.6°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04616: Ius Chasma Fault sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image acquired in March 2003 shows dozens of repeated layers of sedimentary rock in a western Arabia Terra crater at 8°N, 7°W. Wind has sculpted the layered forms into hills somewhat elongated toward the lower left (southwest). The dark patches at the bottom (south) end of the image are drifts of windblown sand. These sedimentary rocks might indicate that the crater was once the site of a lake--or they may result from deposition by wind in a completely dry, desert environment. Either way, these rocks have something important to say about the geologic history of Mars. The area shown is about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the left.
Voir l'image PIA04488: Sedimentary Rock Layers sur le site de la NASA.
12 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a group of tapered ridges, known as yardangs, which formed by wind erosion of a relatively easily-eroded material, most likely sedimentary rock or volcanic ash deposits containing some fraction of sand-sized grains.
Location near: 6.1°S, 210.8°W
Image width: ~2 km (~1.2 mi)
Illumination from: lower left
Season: Southern Summer
On Earth, the longitude of the Royal Observatory in Greenwich, England is defined as the "prime meridian," or the zero point of longitude. Locations on Earth are measured in degrees east or west from this position. The prime meridian was defined by international agreement in 1884 as the position of the large "transit circle," a telescope in the Observatory's Meridian Building. The transit circle was built by Sir George Biddell Airy, the 7th Astronomer Royal, in 1850. (While visual observations with transits were the basis of navigation until the space age, it is interesting to note that the current definition of the prime meridian is in reference to orbiting satellites and Very Long Baseline Interferometry (VLBI) measurements of distant radio sources such as quasars. This "International Reference Meridian" is now about 100 meters east of the Airy Transit at Greenwich.)
For Mars, the prime meridian was first defined by the German astronomers W. Beer and J. H. Mädler in 1830-32. They used a small circular feature, which they designated "a," as a reference point to determine the rotation period of the planet. The Italian astronomer G. V. Schiaparelli, in his 1877 map of Mars, used this feature as the zero point of longitude. It was subsequently named Sinus Meridiani ("Middle Bay") by Camille Flammarion.
When Mariner 9 mapped the planet at about 1 kilometer (0.62 mile) resolution in 1972, an extensive "control net" of locations was computed by Merton Davies of the RAND Corporation. Davies designated a 0.5-kilometer-wide crater (0.3 miles wide), subsequently named "Airy-0" (within the large crater Airy in Sinus Meridiani) as the longitude zero point. (Airy, of course, was named to commemorate the builder of the Greenwich transit.) This crater was imaged once by Mariner 9 (the 3rd picture taken on its 533rd orbit, 533B03) and once by the Viking 1 orbiter in 1978 (the 46th image on that spacecraft's 746th orbit, 746A46), and these two images were the basis of the martian longitude system for the rest of the 20th Century.
The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has attempted to take a picture of Airy-0 on every close overflight since the beginning of the MGS mapping mission. It is a measure of the difficulty of hitting such a small target that nine attempts were required, since the spacecraft did not pass directly over Airy-0 until almost the end of the MGS primary mission, on orbit 8280 (January 13, 2001).
In the left figure above, the outlines of the Mariner 9, Viking, and Mars Global Surveyor images are shown on a MOC wide angle context image, M23-00924. In the right figure, sections of each of the three images showing the crater Airy-0 are presented. A is a piece of the Mariner 9 image, B is from the Viking image, and C is from the MGS image. Airy-0 is the larger crater toward the top-center in each frame.
The MOC observations of Airy-0 not only provide a detailed geological close-up of this historic reference feature, they will be used to improve our knowledge of the locations of all features on Mars, which will in turn enable more precise landings on the Red Planet by future spacecraft and explorers.
Voir l'image PIA03207: The Martian Prime Meridian -- Longitude "Zero" sur le site de la NASA.
13 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a slope on which layered materials are exposed by erosion in the north polar region of Mars. Wind streaks are also evident in this summertime scene. The layers that make up the material beneath the ice of the north polar residual cap are typically considered to be a mixture of some amount of dust and ice, but the proportions of these constituents are not known.
Location near: 82.6°N, 298.1°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Summer
10 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, windblown sand dunes in Herschel Crater. The winds responsible for these dunes came from the northeast (upper right).
Location near: 15.6°S, 228.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
25 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, layered, sedimentary rock outcrops in the crater, Terby. The crater is located on the north rim of Hellas Basin. If one could visit the rocks in Terby, one might learn from them whether they formed in a body of water. It is possible, for example, that Terby was a bay in a larger, Hellas-wide sea.
Location near: 27.9°S, 285.7°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Winter
Southern hemisphere spring on Mars will begin this year around May 6, 2003. During the spring, the MOC operations team will be documenting changes as the seasonal carbon dioxide frost cap retreats southward. In preparation for this year's southern spring, the team has been examining images obtained during the last southern spring, which occurred in 2001.
This pair of images shows gullies and associated scars formed by mass-movement down a slope in the south polar region. The first view, in mid-spring, was acquired in August 2001; it shows a terrain that is largely devoid of the frost that covered everything during winter. However, the aprons of debris from the mass-movements (landslides) are still frosted. By late spring, in the second picture (right), the frost on the aprons had finally sublimed away, and the debris was seen to be not much brighter than their surroundings. The second picture was taken in November 2001, about a week before the first day of summer.
The fact that the aprons of debris retained frost in mid-spring, whereas the surrounding terrain did not, probably indicates that the debris underlying the frost has different thermal properties than the surroundings. The debris might be more coarse-grained (sand or gravel, perhaps), and remained cooler in the daytime than the surrounding, dust-mantled surfaces.
The images are both illuminated from the bottom/lower right. North is toward the bottom, and the area imaged is located near 70.9°S, 339.3°W.
24 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.5 meters per pixel (~5 ft/pixel) view of three aligned meteor impact craters on the floor of a much larger crater in the Noachis Terra region. The craters may have formed together from a single event in which the impactor (the meteor) was broken into three pieces.
Location near: 33.9°S, 10.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the margin of a lava flow near the edge of a scarp in far western Daedalia Planum. A blanket of dust covers the upland (top 1/3 of picture) and the rugged lava flow (lower 2/3 of picture) surfaces. Wind has eroded fine sediment to form triangular tails on top of the ridges of the old lava flow. This image covers an area 3 km (1.9 mi) wide near 20.1°S, 146.6°W. The picture is illuminated from the upper left.
Voir l'image PIA04574: Daedalia Lava Flow Margin sur le site de la NASA.
Light-, dark-, and intermediate-toned slope streaks are common in the thick, dust-mantled regions of Arabia Terra, parts of Tharsis, Memnonia, and some of the knobby areas west of Amazonis Planitia. They most likely form by avalanching of loose, dry dust, perhaps each triggered by a gust of wind. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, acquired earlier this week (in May 2003), shows a plethora of slope streaks on the walls of an impact crater in east-central Arabia Terra near 13.0°N, 319.8°W. The image is 3 km (1.9 mi) wide; sunlight illuminates the scene from the left/lower left.
Voir l'image PIA04508: Slope Streaks in Arabia sur le site de la NASA.
30 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, windblown sand dunes in a crater in the Hesperia region of Mars. The steepest slopes on the dunes -- their slipfaces -- point toward the south-southwest, indicating that the winds responsible for the dunes blew from the north-northeast (top/upper right).
Location near: 12.4°S, 236.5°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season Southern Spring
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a ring of boulders on the floor of a southern mid-latitude basin. The sharp, inner ring of boulders and knobs is the location of the rim of a filled and buried impact crater. The outer, diffuse ring of boulders is the material ejected from the impact crater when it formed. The crater and its ejecta are only thinly buried beneath the surface. This feature is located near 55.5°S, 333.3°W. Sunlight illuminates the scene from the upper left.
21 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a polygon-cracked plain in the south polar region of Mars. When this picture was acquired in April 2005, the surface was covered with seasonal carbon dioxide frost. Dark spots and streaks indicate areas where the frost had begun to change and sublime away.
Location near: 86.8°S, 300.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
This March 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes near the center of Schaeberle Crater, located at 24.6°S, 310.3°W. The steepest slopes on the dunes point toward the left/upper left (northwest), indicating that, when the dunes were active, the dominant regional winds blew from the right/lower right (southeast). The dunes today, however, have a somewhat stunted and sculpted appearance, which suggests that in the most recent part of their history, they have been somewhat eroded. This image covers an area 3 km (1.9 mi) wide and is illuminated from the upper left.
Voir l'image PIA04573: Sand Dunes of Schaeberle Crater sur le site de la NASA.
6 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows outcrops of sedimentary rocks in a crater located just north of the Sinus Meridiani region. Perhaps the crater was once the site of a martian lake.
Location near: 2.9°N, 359.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
7 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a mesa in northeastern Isidis Planitia. The mesa might be a remnant of terrain that once more extensively covered the region.
Location near: 20.3°N, 267.7°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
9 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.5 meters per pixel (~5 ft/pixel) view of a portion of the upper west flank of the giant martian volcano, Olympus Mons. Although considered to be young relative to much of Mars, at high resolution the Olympus Mons volcano turns out to have one of the most heavily cratered surfaces -- at the scale of small craters of tens of meters diameter and smaller -- on the planet. In other words, while the volcano may be a geologically young feature, it is still very ancient and inactive. A segment of a lava channel -- likely a collapsed lava tube -- is present in this scene.
Location near: 17.9°N, 134.6°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) Extended Mission has included dozens of opportunities to point the spacecraft directly at features of interest so that pictures of things not seen during the earlier Mapping Mission can be obtained. The example shown here is a small meteorite impact crater in northern Tharsis near 17.2°N, 113.8°W. Viking Orbiter images from the late 1970's showed at this location what appeared to be a dark patch with dark rays emanating from a brighter center. The MOC team surmised that the dark rays may be indicating the location of afresh crater formed by impact sometime in the past few centuries (since dark ray are quickly covered by dust falling out of the martian atmosphere). All through MOC's Mapping Mission in 1999 and 2000, attempts were made to image the crater as predictions indicated that the spacecraft would pass over the site, but the crater was never seen. Finally, in June 2001, Extended Mission operations allowed the MOC team to point the spacecraft (and hence the camera, which is fixed to the spacecraft) directly at the center of the dark rays, where we expected to find the crater.
The picture on the left (above, A) is a mosaic of three MOC high resolution images and one much lower-resolution Viking image. From left to right, the images used in the mosaic are: Viking 1 516A55, MOC E05-01904, MOCM21-00272, and MOC M08-03697. Image E05-01904 is the one taken in June 2001 by pointing the spacecraft. It captured the impact crater responsible for the rays. A close-up of the crater, which is only 130 meters (427 ft) across, is shown on the right (above, B). This crater is only one-tenth the size of the famous Meteor Crater in northern Arizona.
The June 2001 MOC image reveals many surprises about this feature. For one, the crater is not located at the center of the bright area from which the dark rays radiate. The rays point to the center of this bright area, not the crater. Further, the dark material ejected from the crater--immediately adjacent to the crater rim in the picture on the right (above, B)--is not continuously connected to the larger pattern of rays. Asymmetries in crater form and ejecta patterns are generally believed to occur when the impact is oblique to the surface. The offset of the crater from the center of the rays suggests that the meteor struck at an angle, most likely from the bottom/lower right (south/southeast). The strange geometry of the rays is quite different from that seen for rays associated with impact craters on the Moon and other airless bodies; one possible explanation is that they resulted from disruption of dust on the martian surface by winds generated by the shock wave as the meteor plunged through the martian atmosphere before it struck the ground.
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 PIA03469: Fresh Impact Crater and Rays in Tharsis sur le site de la NASA.
29 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a crater surrounded by thin flows in southeastern Kasei Valles. The flows might have been lava or mud. The picture was acquired in August 2005.
Location near: 14.2°N, 75.1°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: left/lower left
Season: Northern Autumn
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a streak formed by wind in the lee of a meteor impact crater. The winds responsible for the streak and the numerous smaller "tails" behind small obstacles all indicate that regional winds blow from the right/upper right (northeast) toward the left/lower left (southwest). The crater is located near 13.7°S, 131.5°W. Sunlight illuminates the scene from the left/upper left.
Voir l'image PIA04590: Crater with Wind Streak sur le site de la NASA.
Gullies are common in some regions on middle- and polar-latitude slopes, such as crater walls. This March 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows gullies on the north wall of a crater in the Atlantis Chaos region near 34.3°S, 178.0°W. The gullies might have formed by flow of a fluid--perhaps liquid water--sometime in the geologically recent martian past. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04541: Gullied Crater Wall sur le site de la NASA.
28 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows flow materials-on the east/right side of the image-that have come in among a suite of sharp ridges and grooves on the floor of the vast Kasei Valles system. The ridges and grooves are much older and are believed to be the result of a giant, catastrophic flood. The flows might have been mud or lava that ran part way down the ancient valley at a later date.
Location near: 16.7°N, 76.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
11 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a field of low-albedo (dark) barchan sand dunes in a crater located in western Arabia Terra. Small dunes like these are common in the craters of western Arabia Terra and they are often the source of finer, dark sediment that forms windstreaks further downwind. The steepest slopes on the dunes, their slipfaces, are pointed toward the southeast (lower right), indicating that the dominant winds in this location come from the opposite direction.
Location near: 6.4°N, 346.2°W
Image width: ~3 km (~1.9 mi
Illumination from: lower left
Season: Northern Autumn
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a complex streak formed by deposition and erosion of sediment by wind in the lee of an impact crater in western Daedalia Planum. The winds needed to create this feature blew from the southeast (from the lower right). The picture covers an area 3 km (1.9 mi) wide near 10.1°S, 133.7°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04465: Daedalia Planum Wind Streak sur le site de la NASA.
9 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the gullied wall of a pit in the south polar region of Mars. The dark area is a patch of windblown and wind-eroded sand.
Location near: 71.4°S, 357.7°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
26 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a plethora of dark streaks created by spring and summer dust devil activity in Argyre Planitia.
Location near: 47.3°S, 39.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
Sending a very high resolution camera to Mars--the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC)--has resulted in some startling discoveries about the red planet since 1997. One of the MOC discoveries, announced three years ago in June 2000, is the presence of middle- and polar-latitude gullies that were cut by a fluid that behaves as water does. Since their discovery, gullies have generated considerable discussion and debate in the Mars science community. Some speculate that they are caused by groundwater, others suggest melting of subsurface ice or surface accumulations of snow. Still others debate whether the fluid was water, or something more exotic like gaseous carbon dioxide. Regardless, thousands of MOC images obtained since 1997 show that the gullies, while occurring at middle and polar latitudes, do not show a particular preference for poleward-facing slopes, as had been originally determined from the smaller sampling available in 1999 and 2000. Gullies tend to occur in regional clusters and they tend to be associated with layers exposed on the walls of craters, troughs, and valleys. This example shows gullies in the wall of an impact crater in Terra Sirenum near 39.1°S, 166.1°W. The picture was taken on June 10, 2003, the same day as the recent Mars Exploration Rover, Spirit, launch. The scene is illuminated from the upper left and covers an area 3 km (1.9 mi) across.
Voir l'image PIA04599: Gullies in Terra Sirenum sur le site de la NASA.
Gullies--possibly formed by a liquid such as water in the recent martian past--formed at two different levels in the walls of a meteor impact crater near 36.2°S, 185.5°W. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows gullies in the upper crater wall (top of the image) and emergent from the slope of a lower terrace (bottom of the image). Sunlight illuminates the scene from the upper left.
Voir l'image PIA04548: Gullies in Terraced Crater Wall sur le site de la NASA.
31 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a rare patch of dark sand dunes in the Nilosyrtis Mensae region of Mars. The steepest slopes on these dunes, their slipfaces, point toward the south-southwest, indicating that the dominant winds that formed them came from the north-northeast (top/upper right).
Location near: 34.5°N, 295.1°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
26 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows yardangs -- a typical ridge pattern formed by wind erosion -- in southern Amazonis. Some time after the wind erosion occurred, conditions changed and, instead of erosion, the region experienced deposition by a relatively thin, uniform coating of dust. It is this coating of dust that gives the region a monotone appearance. Dark streaks occurring on slopes are formed by avalanching of the dry dust.
Location near: 10.1°N, 156.9°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
26 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark rippled surfaces and a patch of light-toned, perhaps sedimentary rock exposed on the floor of western Tithonium Chasma, part of the vast Valles Marineris trough system.
Location near: 5.0°S, 90.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season Southern Spring
Sometimes Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images show things that look very bizarre. Unique among the MOC images is a suite of pictures from northwestern Hellas Planitia, such as the example shown here. The seeming familiarity of many MOC images, such as those showing Earth-like sand dunes or stream-like gullies might give the impression that it is pretty easy to understand what MOC images are telling us about the geology of Mars. Indeed, much of what has been found by MOC is both interpretable and profound--layers recording the planet's early geologic history, evidence for recent groundwater emerging at the surface, dust storms and frost patterns that indicate seasonal change. However, many martian landforms remain unexplained and may require years of study. This picture, acquired in late October 2000, appears to be a jumble of plates or layers exposed at the surface but subsequently covered by a thin mantle to give the scene a uniform brightness. What are these materials? Perhaps time and careful study will tell. The picture is illuminated from the upper left and covers an area 2.9 by 4.1 km (1.8 by 2.5 mi) near 39.7°S, 306.7°W.
Voir l'image PIA03210: Strange Surfaces of Hellas Planitia sur le site de la NASA.
5 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows gullies and dust devil streaks on the slopes of a large dune in Russell Crater. Gullies on martian dunes typically occur only in the Noachis Terra region, and almost exclusively form on southward-facing slopes. They might be the result of downslope movement of sand mixed with a fluid such as carbon dioxide gas or water that had been trapped as ice in the dune.
Location near: 54.6°S, 347.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows a pattern of polygons on the floor of a northern plains impact crater. These landforms are common on crater floors at high latitudes on Mars. Similar polygons occur in the arctic and antarctic regions of Earth, where they indicate the presence and freeze-thaw cycling of ground ice. Whether the polygons on Mars also indicate water ice in the ground is uncertain. The image is located in a crater at 64.8°N, 292.7°W. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04516: Polygons on Crater Floor sur le site de la NASA.
3 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a cratered surface in Isidis Planitia, a martian lowland. Light-toned "squiggles" in this August 2005 image are large windblown ripples.
Location near: 10.6°N, 275.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
3 September 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows polygons enhanced by subliming seasonal frost in the martian south polar region. Polygons similar to these occur in frozen ground at high latitudes on Earth, suggesting that perhaps their presence on Mars is also a sign that there is or once was ice in the shallow subsurface. The circular features are degraded meteor impact craters.
Location near: 72.2°S, 310.3°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
The spiraling feature near the center of this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is known as a cycloidal marking. Patterns like this can also occur on Earth. On Mars, the cycloidalpattern--and all of the other dark streaks in this picture--are thought to have been formed by passing dust devils. On Earth, cycloidal markings have been observed to result from some tornadoes. The pattern is created when more than one vortex (spinning column of air) is traveling, and spinning, together. This picture is near 62.9°S, 234.7°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04564: Cycloidal Dust Devil Track sur le site de la NASA.
29 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows house-sized boulders and layered volcanic rock exposed in a pit on the north flank of the giant Tharsis volcano, Ascraeus Mons. The pit most likely formed by collapse. Dust mantles much of the surrounding terrain and the pit floor.
Location near: 12.9°N, 101.6°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Winter
Although dust storms occur year-round on Mars, they often occur in greater numbers during certain seasons. In particular, it has long been known from Earth-based telescopic observations that the largest, global dust events(those that enshroud the entire planet) occur during the southern spring and summer. As the Mars Global Surveyor (MGS) mission began to monitor this period for the second time, particular attention was paid to local and regional dust storms in anticipation of capturing--for the first time--high spatial-and time-resolution observations of the start of a "global" storm.
Throughout the month of June 2001, the MGS Mars Orbiter Camera (MOC)routinely accumulated low resolution (7.5 km/pixel) global maps of Marson an orbit-by-orbit basis. A moderately large number of local dust storms were noted, especially along the retreating margin of the seasonal south polar CO2 frost cap and around the large and deep Hellas impact basin that dominates the southern, eastern highlands. On June 21, an otherwise undistinguished small dust storm surged into the basin from the southwest. When viewed 24 hours later, the storm had circulated clockwise about 1/3of the circumference of Hellas, indicating relatively high winds. For the next three days, this storm brewed north of Hellas and east towards Hesperia, but didn't cross the equator (see PIA03170). Then, sometime between 2 PM local Mars time on June 25 and 2 PM local Mars time on June 26, the storm exploded north across the equator, and in less than 24 hours thereafter, dust was being raised from separate locations in Arabia, Nilosyrtis, and Hesperia, thousands of kilometers away from Hellas. This was the start of the long-anticipated global dust event.
Over the following week, dust injected high into the stratosphere during the initial Hellas and Hesperia storms drifted eastward, carried by the prevailing south circumpolar jet stream. Beneath this "veil" of dust, an intense wind front moved across Mars, setting up conditions for many other local and regional dust storms. By July 4, a large regional storm was raging between Daedalia Planitia south of the Tharsis volcanoes and Syria Planum (just south of Labyrinthus Noctis, see PIA03171). Another storm was raising plumes of dust in north central Noachis/southwestern Meridiani. Plumes were rising in Hesperia but not Hellas.
Throughout July and August, MOC observations revealed a general pattern of regional storm centers beneath an ever-spreading veil of stratospheric dust. The Daedalia/Claritas/Syria storm created dust plumes on over 90 consecutive days .
Previous views and perceptions of global dust events had noted regional brightenings within the overall pall of what was called a "global duststorm." From our new observations, we know that at least this global dust "storm" was really a set of storms, somehow triggered to occur at the same time. We also know that dust was not raised from everywhere on the surface during this global event, but rather from discrete, long-lived centers of activity. We saw, for the first time, rapid, cross-equatorial flow of dust-raising winds.
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 PIA03172: The 2001 Great Dust Storms - Daedalia/Claritas/Syria Dust Plumes sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the results of wind erosion of a thick deposit of fine-grained, cemented material. The ridges oriented roughly from upper left to lower right (northwest to southeast) are called yardangs. Similar features occur in some of Earth's desert regions. The flat surface with narrow, sinuous ridges at the top (north) end of the picture is interpreted to be an ancient lava plain that is being slowly revealed as the overlying materials are eroded away. This picture is located near 13.2°N, 159.9°W. Sunlight illuminates the scene from the left/lower left.
Voir l'image PIA04518: Yardangs and Exhumation sur le site de la NASA.
22 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small impact crater with a "butterfly" ejecta pattern. The butterfly pattern results from an oblique impact. Not all oblique impacts result in an elliptical crater, but they can result in a non-radial pattern of ejecta distribution. The two-toned nature of the ejecta -- with dark material near the crater and brighter material further away -- might indicate the nature of subsurface materials. Below the surface, there may be a layer of lighter-toned material, underlain by a layer of darker material. The impact throws these materials out in a pattern that reflects the nature of the underlying layers.
Location near: 3.7°N, 348.2°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
26 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows two circular features on the plains of northern Utopia. A common sight on the martian northern plains, these rings indicate the locations of buried impact craters.
Location near: 65.1°N, 261.2°W
Image width: ~2 km (~1.2 mi)
Illumination from: lower left
Season: Northern Summer
The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) continues in 2003 to return excellent, high resolution images of the red planet's surface. This nearly 1.5 meters (5 ft.) per pixel view of a landslide on a 200 meter-high (219 yards-high) slope in Kasei Valles was specifically targeted for scientific investigation by rotating the MGS spacecraft about 7.8° off-nadir in January 2003. The scar left by the landslide reveals layers in the bedrock at the top the slope and shows a plethora of dark-toned, house-sized boulders that rolled down the slope and collected at the base of the landslide scar. A few meteor impact craters have formed on the landslide deposit and within the scar, indicating that this landslide occurred a very long time ago. Sunlight illuminates this scene from the left/lower left; the landslide is located near 28.3°N, 71.9°W.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows shear striations, dark dunes banked up against the toe of the slide and over-riding light-toned ripples and boulders on surface of slide. These features can be used to determine quantitative aspects of surface processes.
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 PIA03175: Toe of Ganges Chasma Landslide ( 8.0 S, 44.4W) sur le site de la NASA.
24 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a view of some of the circular pits and spectacular buttes and mesas formed in the frozen carbon dioxide of the martian south polar residual cap. The scarps that bound each pit and mesa have been observed by MOC to retreat at an average rate of about 3 meters (~3 yards) during each southern summer season that the spacecraft has been in orbit. A new summer season will start in mid-August 2005.
Location near: 86.9°S, 5.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
21 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows two troughs/depressions formed along the trend of the Sirenum Fossae, a suite of very extensive troughs formed by faults that are radial to the giant Tharsis Bulge. As the Tharsis region bulged outward, adjacent terrain expanded and formed a series of long, extensional fault systems.
Location near: 26.4°S, 142.4°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
17 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows channels carved by catastrophic floods in the Tharsis region of Mars. This area is located northwest of the volcano, Jovis Tholus, and east of the large martian volcano, Olympus Mons. The terrain is presently mantled with fine dust.
Location near: 20.8°N, 118.8°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image was acquired during the first week of June 2003. It shows a small mesa surrounded by a plain of dust-mantled dunes and ripples near 5.9°S, 202.8°W. Large, house-sized boulders have tumbled down the mesa slopes. This one of the highest resolution images from Mars, each pixel covers an area of 1.5 meters (5 feet) across. Sunlight illuminates the scene from the left.
Voir l'image PIA04563: Small Martian Mesa sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image portrays the dark, somewhat cemented, wind-scoured sand dunes of central Herschel Crater. The picture covers an area about 3 km (1.9 mi) wide near 15.7°S, 228.8°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04472: Grooved Herschel Dunes sur le site de la NASA.
16 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows gullies in the southeast-facing wall of an impact crater in northwestern Acidalia Planitia. Gullies are common in southern middle-latitude craters, and much less common in cases like the one shown here, found at a northern middle latitude. Debate continues within the Mars science community as to the origin of the gullies, whether by groundwater, melting ice or snow, or an alternative fluid such as carbon dioxide.
Location near: 41.4°N, 44.8°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
21 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows eroded, light-toned layered rock outcrops on the side of a large mound in Ganges Chasma, part of the vast Valles Marineris trough system. Perhaps a testament to the inherent human (and primate) ability to pick out faces where partially hidden from view (even when a face is not really there) -- near the top of this picture are two features, each a product of erosion, resembling a pair of human eyes. This picture was acquired in late November 2005.
Location near: 7.1°S, 49.4°W
Image width: width: 0.55 km (~0.3 mi)
Illumination from: left/lower left
Season: Southern Summer
8 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows bright (and a few dark) wind streaks formed in the defrosting carbon dioxide of the south polar seasonal frost cap. Unknown is whether the streaks form when wind picks up, moves, and deposits ice particles, or whether wind erodes down into the ice to form the streak pattern.
Location near: 86.7°S, 295.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
This is a late winter Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture of frost-covered gullies in a crater in the martian southern hemisphere. The dark spots are areas where the frost has begun to change or sublime away. The gullies are formed by a combination of mass movement (landsliding) and possibly fluid flow through the channels--whether the fluid was liquid water or some other material is unknown. Today, the surfaces are dry and subjected to the seasonal coming-and-going of carbon dioxide frost. The image is located near 71.0°S, 95.5°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04587: Defrosting Gully Aprons sur le site de la NASA.
NASA's Jet Propulsion Laboratory manages the Mars Global Surveyor mission for NASA's Office of Space Science, Washington, D.C. The Mars orbiter camera was provided by Malin Space Science Systems. Lockheed Martin Astronautics, Denver, is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
Voir l'image PIA04409: Gullies on Martian Crater (MOC) sur le site de la NASA.
6 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, layered, sedimentary rocks exposed by the fluids that carved the Ladon Valles system in the Erythraeum region of Mars. These rocks are so ancient that their sediments were deposited, cemented to form rock, and then eroded by the water (or other liquid) that carved Ladon Valles, so far back in Martian history that such liquids could still flow on the planet's surface.
Location near: 20.8°S, 30.0°W
Image width: ~3 km (~1.9 mi
Illumination from: upper left
Season: Southern Spring
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows rugged, wind-eroded material that once used to completely cover the upper flanks of the martian volcano, Apollinaris Patera. This material; perhaps ancient volcanic ash or more recent, cemented dust, has been partially removed by wind erosion, revealing a smoother surface beneath. This view is located near the summit of the volcano, around 9.3°S, 186.1°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04551: Apollinaris Patera Surfaces sur le site de la NASA.
1 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a south polar residual cap landscape, formed in frozen carbon dioxide. There is no place on Earth that one can go to visit a landscape covering thousands of square kilometers with frozen carbon dioxide, so mesas, pits, and other landforms of the martian south polar region are as alien as they are beautiful. The scarps of the south polar region are known from thousands of other MGS MOC images to retreat at a rate of about 3 meters (~3 yards) per martian year, indiating that slowly, over the course of the MGS mission, the amount of carbon dioxide in the martian atmosphere has probably been increasing.
Location near: 86.9°S, 25.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image was taken during southern spring, as the seasonal carbon dioxide frost cap was subliming away. Frost remaining in shallow cracks and depressions reveals a fantastic polygonal pattern. Similar polygons occur in the Earth's arctic and antarctic regions-on Earth such polygons are related to the freeze and thaw of ground ice. The picture covers an area about 3 km (about 1.9 mi) wide near 71.9°S, 11.1°W. Sunlight illuminates the scene from the left.
Voir l'image PIA04475: Polar Polygon Patterns sur le site de la NASA.
17 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, windblown sand and an eroded slope of massively-bedded, light-toned, sedimentary rock. These landforms are located in east/central Candor Chasma.
Location near: 6.8°S, 71.7°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
13 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows collapse pits on the lower east flank of Ascraeus Mons, a larger volcano in the Tharsis region of Mars.
Location near: 11.5°N, 102.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
12 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a banded surface in Argyre Planitia, the second largest impact basin in the martian southern hemisphere. The bands are the erosional expression of layered, perhaps sedimentary, rock.
Location near: 55.8°S, 45.4°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
4 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a circular feature on the martian northern plains. It was once a crater formed by meteoritic impact. It was completely filled and buried by and within layered material. Later, the layered materials have begun to be eroded away, re-exposing the old crater rims in the process.
Location near: 44.9°N, 264.7°W
Image width: ~3 km (~1.9 mi
Illumination from: lower left
Season: Northern Autumn
15 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a somewhat sinuous, nearly flat-topped ridge, located in eastern Arabia Terra. The ridgetop was once the floor of a valley, perhaps carved by running water. The valley floor, or material that covered the floor, was more resistant to erosion than the surrounding rock into which the valley was cut. Thus, over time, the valley disappeared and its floor was left standing high as a ridge. Inverted valleys are common on Mars; they also occur on Earth.
Location near: 10.8°N, 313.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
19 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows deep gullies cut into the wall of a south mid-latitude crater. Erosion has exposed layers in the upper wall of the crater; it is possible that groundwater seeping through a layer or layers in the wall led to the genesis of the gullies. The banked nature of the gully channels suggests that a liquid was involved.
Location near: 35.5°S, 194.8°W
Image width: width: ~2 km (~1.2 mi)
Illumination from: upper left
Season: Southern Spring
5 September 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dust devil caught in the act of creating a dark streak on the floor of the large, south mid-latitude crater, Mendel. Dozens of other dark streaks mark the paths of earlier dust devils. Dust devil streaks at southern middle and high latitudes are seasonal features; they are erased each winter by thin deposits of dust and frost, and they are re-created each spring and summer by new dust devils.
Location near: 58.9°S, 199.4°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
This summertime Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view of the floor of Argyre Basin shows a plethora of dark streaks thought to have been created by the passage of dust devils. Dust devils are vortices of wind--just as a tornado is a vortex of wind associated with stormy weather on Earth, and the spiraling of water down a bathtub drain is a vortex in a liquid. Dust devils usually form on Mars on relatively calm, quiet, spring and summer afternoons. The passage of a dust devil picks up and disturbs the thin coatings of dust on the martian surface, forming streaks that mark the path that the moving dust devil took. This picture covers an area 3 km (1.9 mi) wide and is located near 48.5°S, 43.0°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04524: Argyre Dust Devil Tracks sur le site de la NASA.
12 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a slope upon which are exposed some of the layered materials that underlie the south polar cap of Mars. The layers are generally considered to be sediments--perhaps dust--that may have been cemented by water ice.
Location near: 84.1°S, 343.9°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
23 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned rock outcrops, mesas, and buttes in Aram Chaos. Located immediately west of Ares Vallis, Aram Chaos is a large, nearly-filled impact basin. The sedimentary materials that filled the basin have been lithified -- that is, hardened to form rock.
Location near: 2.8°N, 20.0°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
29 May 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a surface in the south polar region, covered by carbon dioxide frost. In this springtime scene, the frost has begun to sublime or change character so that sandy surfaces exhibit an abundance of dark spots. The circular depression is probably the remains of an impact crater. In summer, the spotted surfaces in this image would be darker than their surroundings, because they are patches of windblown sand.
Location near: 67.6°S, 254.3°W
Image width: ~3 km (~1.9 mi
Illumination from: upper left
Season: Southern Spring
10 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows eroded remnants of carbon dioxide ice in the south polar residual cap of Mars. The scarps that outline each small mesa have retreated about 3 meters (~10 feet) per Mars year since MGS began orbiting the red planet in 1997.
Location near: 87.0°S, 31.9°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
16 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the results of catastrophic flooding in Marte Vallis, Mars. Marte is the Spanish word for Mars. Many of the major valleys on the red planet are named for the word for "Mars" in the various languages of Earth. This image shows just a very small portion of the hundreds-of-kilometers-long Marte Vallis system.
Location near: 17.4°N, 174.7°
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
A key aspect of the Mars Global Surveyor (MGS) Extended Mission is the opportunity to turn the spacecraft and point the Mars Orbiter Camera (MOC) at specific features of interest. A chance to point the spacecraft comes about ten times a week. Throughout the Primary Mission (March 1999 - January 2001), nearly all MGS operations were conducted with the spacecraft pointing "nadir"--that is, straight down. In this orientation, opportunities to hit a specific small feature of interest were in some cases rare, and in other cases non-existent. In April 1998, nearly a year before MGS reached its Primary Mission mapping orbit, several tests of the spacecraft's ability to be pointed at specific features was conducted with great success (e.g., Mars Pathfinder landing site, Viking 1 site, and Cydonia landforms). When the Mars Polar Lander was lost in December 1999, this capability was again employed to search for the missing lander. Following the lander search activities, a plan to conduct similar off-nadir observations during the MGS Extended Mission was put into place. The Extended Mission began February 1, 2001. On April 8, 2001, the first opportunity since April 1998 arose to turn the spacecraft and point the MOC at the popular "Face on Mars" feature.
Viking orbiter images acquired in 1976 showed that one of thousands of buttes, mesas, ridges, and knobs in the transition zone between the cratered uplands of western Arabia Terra and the low, northern plains of Mars looked somewhat like a human face. The feature was subsequently popularized as a potential "alien artifact" in books, tabloids, radio talk shows, television, and even a major motion picture. Given the popularity of this landform, a new high-resolution view was targeted by pointing the spacecraft off-nadir on April 8, 2001. On that date at 20:54 UTC (8:54 p.m., Greenwich time zone), the MGS was rolled 24.8° to the left so that it was looking at the "face" 165 km to the side from a distance of about 450 km. The resulting image has a resolution of about 2 meters (6.6 feet) per pixel. If present on Mars, objects the size of typical passenger jet airplanes would be distinguishable in an image of this scale. The large "face" picture covers an area about 3.6 kilometers (2.2 miles) on a side. Sunlight illuminates the images from the left/lower left.
Voir l'image PIA03225: Highest-Resolution View of "Face on Mars" sur le site de la NASA.
10 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows eroded, exposed layered materials in the south polar region of Mars. Since Mariner 9 in 1972, the polar layered materials have been assumed to be geologically recent accumulations of dust and ice, but MOC images provide no clear evidence that the materials are particularly young or composed of a specific suite of materials. They might as easily be composed of ancient, sedimentary rock.
Location near: 80.6°S, 230.1°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
7 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a field of small craters formed by secondary debris thrown from a larger meteoritic impact on the plains south of the Cerberus region.
Location near: 2.3°N, 195.7°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
27 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a plethora of dark streaks created by spring and summer dust devil activity in Argyre Planitia.
Location near: 64.9°S, 8.3°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
8 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a chain of pits associated with dust-covered lava flows in northern Tharsis. The pits formed along a fault; some of the flows may have erupted along this same fault.
Location near: 23.4°N, 110.6°W
Image width: ~3 km (~1.9 mi
Illumination from: lower left
Season: Northern Autumn
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an old meteor impact crater that was once buried and was then partially-exhumed from within the layered rocks on the floor of a much larger crater in eastern Arabia Terra. The erosion processes that began to exhume the crater, however, stopped some time ago, because today the entire area is covered by a blanket of dust. Avalanches of this dust have created dark streaks on the walls of the partly exhumed crater. This April 2003 image covers an area 3 km (1.9 mi) wide and is located near 20.9°N, 320.8°W. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04549: Old Arabian Crater sur le site de la NASA.
30 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a wind-eroded landscape in the Amazonis Mensa region of far western Tharsis. Two meteor impact craters that formed in -- and then were buried by -- rock are now found in a state of partial-exhumation from within the wind-eroded material.
Location near: 2.0°N, 147.3°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
28 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows eroded sedimentary rock outcrops in northern Sinus Meridiani.
Location near: 3.6°N, 2.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
11 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows two small mesas, a hill, and other landforms in the highly-eroded landscape of eastern Arabia Terra.
Location near: 30.0°N, 295.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
One of the most profound discoveries that would not have been possible if NASA's Mars Global Surveyor mission had not been extended beyond its primary mission of one Mars year (687 Earth days) is that of dramatic changes that take place in the south polar residual ice cap each martian year. To make this discovery, the Mars Orbiter Camera on the spacecraft had to be employed during a second Mars year to repeat images of sites on the south polar cap that had been imaged during the primary mission.
The initial discovery was made in 2001, when the camera team repeated images of portions of the south polar cap that had already been imaged in 1999. The goal of these images was to obtain stereo views, which would allow investigators to see the topography of the cap in three dimensions and to measure the thickness of the polar ice layers.
It was not possible to produce the desired 3-D views. To the team's surprise, the landforms of the south polar cap had changed.
The south polar residual cap -- that is, the portion of the ice cap that remains bright and retains ice throughout the southern summer season -- was seen in 1997 and 1999 images to have a complex terrain of broad, relatively flat mesas, small buttes, and many pits and troughs. Pits are generally circular and in some areas visually resemble a stack of thin slices of Swiss cheese. Very early in the Mars Global Surveyor mission, the Mars Orbiter Camera team speculated that these landforms must be carved into frozen carbon dioxide, because they look so unfamiliar and because Viking orbiter infrared measurements indicated that the south polar cap is cold enough consist of frozen carbon dioxide, even in summer.
The observations made by Mars Orbiter Camera in 2001, during the first part of the extended mission, showed that the scarps and pit walls of the south polar cap had retreated at an average rate of about 3 meters (10 feet) since 1999. In other words, they were retreating 3 meters per Mars year (and, of course, most of that retreat takes place during the summer). In some places on the cap, the scarps retreat less than 3 meters a Mars year, and in others it can retreat as much as 8 meters (26 feet) per martian year.
Of the two volatile materials one is likely to find in a frozen state on Mars -- water and carbon dioxide -- it is carbon dioxide that is volatile enough to permit scarp retreat rates like those observed by the Mars Orbiter Camera.
Over time, south polar pits merge to become plains, mesas turn into buttes, and buttes vanish forever. Since 2001, two additional Mars years have elapsed. A scientific benefit of having a long extended mission for Mars Global Surveyor has been the opportunity to document how the polar cap is changing each year.
Four images are shown here, plus an animation at left presenting the four frames in sequence. The location is near 86.3 degrees south latitude, 49.4 degrees west longitude, and the images show the same portion of the south polar residual cap as it appeared in 1999, 2001, 2003, and 2005. Comparing the images or viewing the animation makes it evident that the landscape of the south polar cap has been changing rapidly over the past four martian years.
Each year that Mars Global Surveyor has been in orbit, the landforms of the south polar residual cap have gotten smaller, and the carbon dioxide removed from the cap has not been re-deposited. The implication is that Mars presently has a warm (and possibly warming) climate, with new carbon dioxide going into the atmosphere every year. The other implication is that, at some time in the not-too-distant past, the planet had a colder climate, so that the layers of carbon dioxide could be deposited in the first place. If one takes the rate of scarp retreat and projects it backwards to fill in all of the pits and troughs with the carbon dioxide that has been removed from them, one finds that the colder climate might only have occurred a few centuries to a few tens of thousands of years ago. This kind of time scale is not unlike that of the climate changes that have been recorded on Earth, including the Ice Ages and the smaller fluctuations that have occurred since the last Ice Age (e.g., the "Little Ice Age" of the mid-14th through mid-19th centuries).
After the discovery that the pits were enlarging and that we were not seeing carbon-dioxide deposition, it was suggested that interannual variations might be large enough to permit such deposition on a short timescale. However, two Mars years of additional observations show no large magnitude annual differences. Variations that would permit carbon dioxide deposition may require decades. And to see such variations may require many more Mars years of observations by orbiting spacecraft.
The Mars Orbiter Camera was built and is operated by Malin Space Science Systems, San Diego, Calif. Mars Global Surveyor left Earth on Nov. 7, 1996, and began orbiting Mars on Sept. 12, 1997. JPL, a division of the California Institute of Technology, Pasadena, manages Mars Global Surveyor for NASA's Science Mission Directorate, Washington.
West Candor is part of the vast Valles Marineris trough system. These chasms and canyons cut through ancient, layered bedrock. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows some of the layering revealed in the wall and on the upland surface outside of southwest Candor Chasma. This image is located near 6.7°S, 76.8°W. Sunlight illuminates the scene from the right/lower right.
Voir l'image PIA04540: Layered Walls of West Candor sur le site de la NASA.
27 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows outcrops of light-toned, layered rock exposed in the central peak of Oudemans Crater, near the Labyrinthus Noctis of the western Valles Marineris complex. The rocks in this August 2005 image were once below the ground and flat-lying. Now they are tilted on edge-a product of the impact that formed Oudemans Crater. Their regular layering and light tone suggest these might be ancient sedimentary rocks.
Location near: 10.0°S, 92.1°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
11 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of troughs in the Tharsis region that were also the site of some catastrophic floods. These features are located northwest of the volcano, Jovis Tholus.
Location near: 1220.7°N, 118.6°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
12 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an impact crater with large boulders along its rim. The crater is located in Tempe Terra.
Location near: 36.6°N, 88.9°W
Image width: ~3 km (~1.9 mi
Illumination from: lower left
Season: Northern Autumn
The portion of the martian south polar cap that persists through each southern hemisphere summer is known as the residual cap. This Mars Global Surveyor(MGS) Mars Orbiter Camera (MOC) image shows a 2.9 by 4.8 km (1.8 by 3 mi) area of the south polar residual cap as it appeared in mid-summer on 23 February 2000. The landscape of the south polar residual cap is dominated by layered, frozen carbon dioxide ("dry ice") that has been eroded into a variety of pits, troughs, buttes, and mesas. Commonly, the pits are circular and the mesa scarps are arcuate. In summer, as carbon dioxide is subliming away, the scarps bounding the pits and mesas darken. The darkened slopes may indicate that small amounts of dust are present, mixed-in with the ice. The ice is layered, indicating many cycles of deposition preceded the present period of sublimation and erosion. Recent MGS MOC images acquired in 2001 have indicated that the scarps are retreating an average of 3 meters (3.3 yards) per martian year. As more carbon dioxide is released into the atmosphere each southern spring and summer, the atmospheric pressure of Mars may increase such that it could double in a few hundred to a thousand Mars years (687 Earth days = 1 Mars year). The picture shown here is from MOC image M12-02295 and is illuminated by sunlight from the lower right.
A version of this picture appears on the cover of the December 7, 2001, issue ofScience and accompanies a paper regarding the MGS MOC discovery of evidence for martian climate change.
Voir l'image PIA03180: MOC View of the Martian South Polar Residual Cap sur le site de la NASA.
8 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows landforms created by sublimation processes on the south polar residual cap of Mars. The bulk of the ice in the south polar residual cap is frozen carbon dioxide.
Location near: 86.6°S, 342.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
10 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows complexly-eroded, layered, sedimentary rock outcrops in southern Melas Chasma, part of the vast Valles Marineris trough system. These rocks were originally deposited as sediment, perhaps in water, long ago.
Location near: 12.5°S, 73.3°W
Image 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 PIA03468: MGS MOC Extended Mission View of North Polar Layers sur le site de la NASA.
30 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows mesas and other eroded landforms in eastern Arabia Terra, near Huo Hsing Vallis. Arabia Terra is generally a cratered terrain that has been severely eroded, although the causes of the erosion -- and where all the material went when it was removed -- are not known.
Location near: 27.3°N, 293.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Summer
1 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small, relatively light-toned knob of layered material, and the erosional expression of the underlying layers, in the south polar region of Mars. When the image was acquired in April 2005, the surface was still covered with seasonal carbon dioxide frost. Dark spots and streaks mark locations where the frost had begun to change and sublime away.
Location near: 84.2°S, 138.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season Southern Spring
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a fresh, young meteor impact crater on the martian surface. It is less than 400 meters (less than 400 yards) across. While there is no way to know the exact age of this or any other martian surface feature, the rays are very well preserved. On a planet where wind can modify surface features at the present time, a crater with rayed ejecta patterns must be very young indeed. Despite its apparent youth, the crater could still be many hundreds of thousands, if not several million, of years old. This impact scar is located within the much larger Crommelin Crater, near 5.6°N, 10.0°W. Sunlight illuminates the scene from the left.
Voir l'image PIA04619: Fresh, Rayed Impact Crater sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture obtained in April 2003 shows eroded layered rock outcrops near the southwest rim of Juventae Chasma in the southern hemisphere. This area is near 4.8°S, 63.7°W. Layers such as these record some fraction of the geologic history of Mars; however, that history cannot really be known from pictures alone. The erosional pattern of these layers suggests that they are sedimentary rocks. The area shown is about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04487: Layers Near Juventae Chasma sur le site de la NASA.
22 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.5 meters per pixel (~5 ft/pixel) view of the interior of a trough, formed by faulting, on the lower southwest flank of Biblis Patera, a volcano in the Tharsis region of Mars. Boulders tend to be most common in volcanic regions, attesting to the hardness of the volcanic rock. In this case, the boulders and surrounding terrain have been largely mantled with dust.
Location near: 1.3°N, 124.9°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
This is a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view of frost-covered sand dunes in Chasma Boreale in the early northern spring season. Dark spots, some of them with bright halos of re-precipitated frost, have formed as the dunes begin to defrost. Most of the frost is carbon dioxide which freezes out of the atmosphere during the cold martian polar winters. This picture is located near 84.7°N, 358.8°W, and is illuminated from the lower left.
Voir l'image PIA04572: Frosted Chasma Boreale Dunes sur le site de la NASA.
7 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a meteor impact crater in northern Tharsis. This crater is a bit more than 2 kilometers wide -- about twice the size of the famous Meteor Crater in northern Arizona, U.S.A. Many smaller craters can be seen superimposed upon the ~2 km diameter crater.
Location near: 34.4°N, 118.8°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
23 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a view of some of the widely-varied terrain of the martian south polar residual cap. The landforms here are composed mainly of frozen carbon dioxide. Each year since MGS arrived in 1997, the scarps that bound each butte and mesa, or line the edges of each pit, in the south polar region, have changed a little bit as carbon dioxide is sublimed away. The scarps retreat at a rate of about 3 meters (~3 yards) per martian year. Most of the change occurs during each southern summer.
Location near: 86.7°S, 9.8°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
This is a late southern summer Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view of the sand dune field in Richardson Crater. In winter and spring, the dunes are covered by carbon dioxide frost. Dozens of MOC images acquired over the past several Mars years (available in the MOC Gallery) show the progression of defrosting patterns on this dune field. In summer, there is no carbon dioxide frost. Small dark streaks on some of the dune slip face slopes are the sites of the most recent avalanches of sand. The slip faces also indicate that the general direction of sand transport is from right (east) to left (west). This image is near 72.4°S, 180.6 °W. The picture is illuminated from the upper left.
Voir l'image PIA04575: Richardson Dunes in Summer sur le site de la NASA.
Sometimes, pictures received from Mars Global Surveyor's Mars Orbiter Camera (MOC) are "just plain pretty." This image, taken in early September 2000, shows a group of sand dunes at the edge of a much larger field of dark-toned dunes in Proctor Crater. Located at 47.9°S, 330.4°W, in the 170 km (106 mile) diameter crater named for 19th Century British astronomer Richard A. Proctor (1837-1888), the dunes shown here are created by winds blowing largely from the east/northeast. A plethora of smaller, brighter ripples covers the substrate between the dunes. Sunlight illuminates them from the upper left.
Voir l'image PIA03208: "Sharks Teeth" -- Sand Dunes in Proctor Crater sur le site de la NASA.
In this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, wind has streaked a field of defrosting sand dunes in Chasma Boreale in the martian north polar region. Dune slip faces--the steep slope formed by avalanching sand on each dune--and the dark streaks indicate that wind transports sediment from the lower left toward the upper right. The picture covers an area about 3 km (1.9 mi) wide near 84.6°N, 358.5°W. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04509: Chasma Boreale Dunes sur le site de la NASA.
9 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a south polar scene, covered by bright, seasonal, carbon dioxide frost. The dark patches are areas where the frost has begun to sublime away.
Location near: 80.0°S, 334.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
19 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows lava flows at the southeast base of the giant volcano, Olympus Mons. The flat plain in the south-southeast (bottom/lower right) portion of the image is younger than and cuts off the ends of many of the lava flows that came from the northwest (upper left). Many of the lava flows in this image exhibit channels with levees bounding their margins. As each lava flow was advancing, its outer margins cooled and hardened, forming a channel or tube through which the molten rock continued to advance.
Location near: 17.2°N, 129.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
24 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the walls and floor of a valley in the western Memnonia region of Mars. The finely-textured ridges and pits found on the valley walls and upland outside of the valley were formed by wind erosion.
Location near: 487.5°S, 155.8°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
March 6, 2003, is the first day of spring in the martian southern hemisphere. As spring progresses in the south, dust devils will begin to form and sweep up some of the veneer of bright dust that accumulated during the recent autumn and winter seasons.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows sand dunes in Wirtz Crater. The dark streaks that criss-cross each dune were probably formed by passing dust devils that disrupted or removed some of the thin layer of dust that coats the dunes. The picture covers an area about 3 km (1.9 mi) wide near 48.3°S, 25.4°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04507: Dunes and Dust Devil Tracks sur le site de la NASA.
The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) red and blue wide angle cameras provide daily coverage of the planet "from limb to limb." The "limbs" are the edges of the planet as seen to the west and east of the spacecraft. Depending on weather conditions, clouds or haze can sometimes be seen above the limb. This picture was taken by the blue camera in December 2002. It is an oblique view looking westward across heavily cratered terrain at high southern latitudes. A thin line of haze, high in the martian atmosphere, can be seen above the planet's surface. The view of craters in the foreground is enhanced by the presence of bright, winter-time carbon dioxide frost. The darkness above the limb is outer space.
Mars Global Surveyor's (MGS) Mars Orbiter Camera (MOC) has obtained thousands of images of martian sand dunes since it began observing the planet from orbit in 1997. Many of the dunes appear to be inactive in the modern environment, but appear to be quite young, otherwise (they do not have any small meteor impact craters on them, they often have sharp edges and brinks--all attributes of modern, active dunes). In some dune fields, as in Herschel Basin in Terra Cimmeria, the dunes are grooved (e.g., see Mars Picture of the Day for April 19, 2003), indicating that they have been cemented and then eroded by wind. In the Noachis Terra region of Mars, many dune fields also appear to have been cemented. The evidence in this case comes from the deep scars formed on the slip face slopes by avalanches of sand. This MOC image shows more than a dozen examples a dune in eastern Kaiser Crater near 47.1°S, 340.0°W. If the dunes were not cemented--that is, if the sand was loose--then the avalanches would not leave steep-sided chutes on the slip face slopes. The implication that many martian dunes are cemented and inactive in the modern martian environment, but were active sometime in the not-too-distant past, suggests that the climate of Mars may have changed in recent times. This picture was obtained in June 2003; it is illuminated from the upper left. North is toward the upper right; the area shown here is about 3 km (1.9 mi) wide.
Voir l'image PIA04610: Kaiser Dune Avalanches sur le site de la NASA.
19 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered material exposed by erosion in the south polar region of Mars. At the time the image was acquired, the surface was covered with seasonal carbon dioxide frost. Dark spots and streaks indicate areas where the annual springtime defrosting process was underway.
Location near: 82.7°S, 112.1°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is a springtime view of frost-covered layers revealed by an eroded scarp in the martian north polar cap. The layers are thought to consist of a mixture of dust, ice, and possibly sand. Some layers are known to be a source for dark sand that occurs in nearby dunes. During the summer, this surface would be considerably darker because most of the bright frost sublimes away during the spring season. The picture covers an area about 3 km (1.9 mi) wide near 85.2°N, 4.4°W. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04500: Frosty North Polar Layers sur le site de la NASA.
3 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small, dust-covered, volcano in the Jovis Fossae region of Mars. While Mars is known for its extremely large volcanoes, such as Olympus Mons, many small volcanoes also occur on the red planet, particularly in the Tharsis region. This small volcano is a good example of those. It was originally found by members of the MGS Mars Orbiter Laser Altimeter (MOLA) team during the MGS primary mission. The volcano is old, and cratered. Its surface is mantled by dust, and its caldera (summit depression) has some dust-covered wind ripples on its floor.
Location near: 20.7°N, 111.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season Northern Autumn
11 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, layered rock outcrops in Eos Chaos, located near the east end of the Valles Marineris trough system. The outcrops occur in the form of a distinct, circular butte (upper half of image) and a high slope (lower half of image). The rocks might be sedimentary rocks, similar to those found elsewhere exposed in the Valles Marineris system and the chaotic terrain to the east of the region.
Location near: 12.9°S, 49.5°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Summer
19 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows two craters that formed at the same time by a split meteoritic impactor. Long after they formed, these craters have been eroded, degraded, and other materials have been deposited on and within them.
Location near: 35.0°S, 328.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
19 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a mid-summer scene in the south polar region of the red planet. The light-toned surface is covered with seasonal frost that, later in the season, would have sublimed away.
Location near: 86.8°S, 322.8°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
16 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows small yardangs formed by wind erosion of a material that once completely covered everything in this scene. These landforms are located in southern Amazonis Planitia.
Location near: 8.1°N, 151.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
15 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a curved, pitted ridge in Isidis Planitia. This feature may be a remnant of a once more-extensive layer of material that covered the present, cratered surface.
Location near: 2217.4°N, 277.8°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
17 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows kidney bean-shaped pits, and other pits, formed by erosion in a landscape of frozen carbon dioxide. This images shows one of about a dozen different patterns that are common in various locations across the martian south polar residual cap, an area that has been receiving intense scrutiny by the MGS MOC this year, because it is visible on every orbit and in daylight for most of 2005.
Location near: 86.9°S, 6.9°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
This view shows sharp detail of a scarp at the head of Chasma Boreale, a large trough cut by erosion into the martian north polar cap and the layered material beneath the ice cap. The picture is a mosaic of two images acquired in January 2005 by the Mars Orbiter Camera on NASA's Mars Global Surveyor, using a resolution-enhancing technique called "compensated pitch and roll targeted observation." The camera team considers this the best pair of images yet acquired using that technique.
During each northern summer on Mars, there occurs a narrow window in time of two to three months when conditions are ideal to image the north polar cap at high resolution. Throughout this period, the atmosphere is generally clear over the cap, and the seasonal carbon-dioxide frost from the previous winter and spring has sublimed away, permitting a good view of the surface geology. The two images in this mosaic were acquired during this brief period during the most recent northern summer. Within a few weeks of when these images were acquired, dust storm activity picked up in the north polar region, making the atmosphere too dusty to obtain any more detailed views until late 2006.
Chasma Boreale is cut into the layered material that lies beneath the water ice of the north polar cap. For decades, these layered materials were assumed to consist of a mixture of ice and dust. Mars Orbiter Camera images obtained in 1999 and 2001 began to show that some of the layers are a source for windblown sand. The science objective for the two images shown in this mosaic was to look for boulders in the debris shed from the steep slopes cut into the north polar layers by Chasma Boreale. Finding boulders would imply that the layers that are the most resistant to erosion in the polar region are as competent as solid rock, perhaps giving a new insight into the nature of the polar layered materials. The pictured site is near 84.8 degrees north latitude, 356.4 degrees west longitude.
Examination of the high-resolution mosaic shows that there are indeed some large boulders that have eroded out of the layered materials and rolled down the slopes. It is possible, therefore, that the north polar layers are not simply a mixture of ice, dust, and sand. Some layers may actually be rock, cemented by minerals rather than by ice. Alternatively, if the materials are cemented by ice, then a future high-resolution view might show that the boulders have become smaller over time.
In addition to the observation of boulders eroding out of the polar layered materials, the mosaic also helps confirm that dark sand is eroding out of the polar layered materials, and that there are three different groups of layers under the polar ice. The upper unit is light-toned, finely layered, and more resistant to erosion (more competent, less easily destroyed by erosion) than the middle unit, which is rich in dark sand but also has several shelf-forming layers in it. Finally, below the dark, sandy layer is a third unit that is light-toned and has a different appearance relative to the other two units. Some of its layers have surfaces that have been broken by shallow fractures into polygonal and linear forms, also implying that they are hard, resistant rock.
The level of detail seen in the mosaic was made possible by the development of a resolution-enhancing technique for using the Mars Orbiter Camera. During 2003 and 2004, the Mars Orbiter Camera operations team at Malin Space Science Systems, San Diego, Calif., worked closely with the Mars Global Surveyor operations teams at the Jet Propulsion Laboratory, Pasadena, Calif., and Lockheed Martin Space Systems, Denver, Colo., to develop a new technique in which the spacecraft does a maneuver that permits the camera to acquire images at a higher spatial resolution than normal. Usually, Mars Orbiter Camera images have a resolution of about 1.5 meters (5 feet) per pixel, and the camera can be commanded to acquire lower resolution data when desired. To obtain a higher resolution, the whole spacecraft must be pitched at such a rate that the camera over-samples its view of the martian surface in the down-track direction. Called compensated pitch and roll targeted observation, or cPROTO, this technique allows Mars Orbiter Camera to obtain images that have a resolution of about 50 centimeters (20 inches) per pixel in the down-track direction, and 150 centimeters (5 feet) per pixel in the cross-track dimension.
The Mars Orbiter Camera was built and is operated by Malin Space Science Systems, San Diego, Calif. Mars Global Surveyor left Earth on Nov. 7, 1996, and began orbiting Mars on Sept. 12, 1997. JPL, a division of the California Institute of Technology, Pasadena, manages Mars Global Surveyor for NASA's Science Mission Directorate, Washington.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) high resolution image shows part of a dark-floored valley system in northern Newton Crater. The valley might have been originally formed by liquid water; the dark material is probably sand that has blown into the valley in more recent times. The picture was acquired earlier this week on July 6, 2003, and is located near 39.2°S, 157.9°W. The picture covers an area 2.3 km (1.4 mi) across; sunlight illuminates the scene from the upper left.
Voir l'image PIA04621: Dark Valley in Newton Crater sur le site de la NASA.
24 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of south mid-latitude gullies on a crater wall. Gullies such as these may have formed by runoff of liquid water.
Location near: 35.6°S, 204.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
8 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a field of dark sand dunes on the northwestern floor of Brashear Crater. The dunes formed largely from winds that blew from the southeast (lower right).
Location near: 253.7°S, 119.4°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
20 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dust devil (right center) and a plethora of streaks created by previous dust devils, on the eastern floor of Mendel Crater. Dust devils are common at middle to high latitudes in the southern hemisphere during the spring and summer seasons.
Location near: 59.0°S, 198.4°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
8 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, windblown sand in the form of dunes and a broad, relatively flat, sand sheet in Ganges Chasma, part of the eastern Valles Marineris trough complex. The winds responsible for these dunes blew largely from the north. Sand dunes on Mars, unlike their Earthly counterparts, are usually dark in tone. This is a reflection of their composition, which includes minerals that are more rich in iron and magnesium than the common silica-rich dunes of Earth. Similar dark sands on Earth are found in volcanic regions such as Iceland and Hawaii. A large dune field of iron/magnesium-rich grains, in the form fragments of the volcanic rock, basalt, occurs south of Moses Lake, Washington, in the U.S.
Location near: 7.7°S, 45.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
10 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a complex of overlapping, inverted channels in a fan exposed by erosion, then mantled by dust, in the Aeolis region of Mars. Aeolis exhibits an abundance of inverted channels and fan-shaped forms, largely created by a liquid such as water, and then preserved in layered, sedimentary rock that has been subsequently eroded by wind.
Location near: 4.6°S, 205.3°W
Image width: ~3 km (~1.9 mi
Illumination from: upper left
Season: Southern Spring
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image captures frost-covered north polar sand dunes in springtime as they are beginning to defrost. Dark spots and streaks indicate areas where frozen carbon dioxide has started to be removed by sublimation and wind. The picture covers an area 3 km (1.9 mi) wide near 76.3°N, 264.9°W. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04460: Defrosting North Polar Dune Field sur le site de la NASA.
22 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an eroded landscape in the south polar region of Mars. Layered material has been exposed to create a complex pattern of steps and low, isolated mesas. The material has also been cracked, and semi-parallel ridges on some of the 'stairsteps' may be old, windblown ripples.
Location near: 86.0°S, 182.1°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
29 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows knobs of remnant, wind-eroded, layered sedimentary rock that once completely covered the floor of a crater located west of the Sinus Meridiani region of Mars. Sedimentary rock outcrops are common throughout the Sinus Meridiani region and its surrounding cratered terrain.
Location near: 2.2°N, 7.9°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
31 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows irregular-shaped mesas in the south polar region of Mars. The bright patches are the remains of seasonal frost. During winter and most of spring, this entire scene would have been covered by carbon dioxide frost.
Location near: 79.2°S, 298.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
Some of the most important high resolution imaging results of the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) experiment center on discoveries about the presence and nature of the sedimentary rock record on Mars. This old meteor impact crater in northwestern Schiaparelli Basin exhibits a spectacular view of layered, sedimentary rock. The 2.3 kilometer (1.4 miles) wide crater may have once been completely filled with sediment; the material was later eroded to its present form. Dozens of layers of similar thickness and physical properties are now expressed in a wedding cake-like stack in the middle of the crater. Sunlight illuminating the scene from the left shows that the circle, or mesa top, at the middle of the crater stands higher than the other stair-stepped layers. The uniform physical properties and bedding of these layers might indicate that they were originally deposited in a lake (it is possible that the crater was at the bottom of a much larger lake, filling Schiaparelli Basin); alternatively, the layers were deposited by settling out of the atmosphere in a dry environment. This picture was acquired on June 3, 2003, and is located near 0.9°S, 346.2°W.
Voir l'image PIA04592: Schiaparelli Sedimentary Rocks sur le site de la NASA.
27 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.5 meters per pixel (~5 ft/pixel) view of aligned pits formed by collapse along a fault trend in the Tractus Catena region of Mars, in northern Tharsis.
Location near: 32.2°N, 101.7°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
This May 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of wind-sculpted ridges on the plains northwest of the Tharsis volcano, Ascraeus Mons. The two circular features are old meteor impact craters. The ridges running from upper left toward lower right may have once been sand dunes. These dunes and the two craters were later covered by thick accumulations of dust or volcanic ash, and this fine material was later eroded by wind to form the somewhat triangular tails and markings that point toward the upper right. The area shown is 1.7 km (1.1 mi) wide and located near 16.0°N, 107.6°W. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04543: Wind-Eroded Terrain in Tharsis sur le site de la NASA.
26 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a crater and adjacent terrain that have been exhumed from beneath a wind-eroded material. The sharp, pointy ridges inside and immediately adjacent to the crater are the remains of a material that once covered the entire scene. Wind has stripped these materials away, forming yardangs. Inside the crater, the erosion has revealed an older, eroded layered material. This smooth-surfaced layered feature inside the crater was already eroded to nearly its present shape before the yardang-forming material was deposited (and then eroded away).
Location near: 7.2°N, 156.4°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
13 July 2005
The south polar residual cap of Mars is composed of layered, frozen carbon dioxide. In 1999, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) showed that the carbon dioxide layers have been eroded to form a variety of circular pits, arcuate scarps, troughs, buttes, and mesas. In 2001, MOC images designed to provide repeated views of the areas imaged in 1999 -- with the hope of creating stereo (3-D) images, so that the height of scarps and depth of pits could be measured -- showed that the scarps had retreated, pits enlarged, and buttes and mesas shrank. Only carbon dioxide is volatile enough in the martian environment to have caused such dramatic changes -- the scarps were seen to retreat at an average rate of 3 meters (about 3 yards) per Mars year. Most of the scarp retreat occurs during the southern summer season; in some areas the scarps move as much as 8 meters, in others, only 1 meter per Mars year.
Three Mars years have now elapsed since MOC first surveyed the south polar cap in 1999. Over the past several months, MGS MOC has been re-imaging areas that were seen in 1999, 2001, and 2003, to develop a detailed look at how the landscape has been changing. This animated GIF provides an example of the dramatic changes that have occurred during the past three martian years. The first image, a sub-frame of M09-05244, was acquired on 21 November 1999. The second image, a sub-frame of S06-00973, was obtained on 11 May 2005. The animation shows the changes that have occurred between 1999 and 2005. Each summer, the cap has lost more carbon dioxide. This may mean that the carbon dioxide content of the martian atmosphere has been increasing, bit by very tiny little bit, each of the years that MGS has been orbiting the red planet. These observations also imply that there was once a time, in the not-too-distant past (because there are no impact craters on the polar cap), when the atmosphere was somewhat thinner and colder, to permit the layers of carbon dioxide to form in the first place. Just as Earth's environment is very different today than it was just 11,000 or so years ago, the martian environment has also been changing on a similar time scale.
Location near: 88.9°S, 25.7°W
Image width: width: ~0.6 km (~0.4 mi)
Illumination from: upper left
Season: Southern Spring
13 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a wind-streaked plain in Tharsis near the Pavonis Mons volcano. The lighter-toned surfaces show how the plain used to look, before strong winds removed much of a thin coating of dust. The light-toned tails behind several craters show that the winds blew from the southwest (lower left).
Location near: 36.6°N, 88.9°W
Image width: ~3 km (~1.9 mi
Illumination from: lower left
Season: Northern Autumn
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture obtained in April 2003 shows the margin of a large lava flow south of Tharsis near 33.5°S, 137.5°W. Some of the lava broke out and poured into an adjacent crater formed by meteor impact. The picture covers an area about 3 km (1.9 mi) wide; the crater is more than twice the size of the famous Meteor Crater in northern Arizona, U.S.A. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04467: Lava Flow and Impact Crater sur le site de la NASA.
17 October 2005
Following the loss of Mars Polar Lander in December 1999, the MOC team began a 2-month intensive effort to acquire 1.5 meters per pixel (~5 feet per pixel) images of the landing ellipse, in hopes of spotting the lander and, perhaps, to provide additional insight as to its fate. Those search efforts were described in two previous Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) releases:
PIA02353: Mars Polar Lander: The Search Continues 24 January 2000PIA02349: Mars Polar Lander: The Search Begins 21 December 1999.
In addition, a later year 2000 release included the full MOC imagemosaic of the site obtained during the search:
PIA02815: South Polar Terrain in "3-D" 16 October 2000.
Based upon the configuration of Mars Exploration Rovers Spirit (PIA05248) and Opportunity (PIA05229, PIA05230, PIA05231), lander hardware observed from orbit by MOC in early 2004, we revisited the December 1999/January 2000 images of the Mars Polar Lander site. Earlier this year, we identified a location in images acquired in January 2000 that included features reminiscent of those that might be expected to exist at the location where the Mars Polar Lander reached the surface. Specifically, we identified a bright feature that resembled a parachute, and a dark area with a small, light-toned central spot that could be the location of the lander amid a dust-deflated area cleared by the lander's descent engines. This finding, alongwith a definitive image of the Viking 2 lander, was detailed in:
MGS Finds Viking Lander 2 and Mars Polar Lander (Maybe) 5 May 2005.
At the time of this identification in early 2005, the Mars Polar Lander landing ellipse was covered by seasonal carbon dioxide frost. As the frost began to sublime away and spring gave way to summer, we attempted to acquire an image of the candidate Mars Polar Lander site at a spatial resolution that is higher than we were able to achieve during the initial search in December 1999/January 2000. To obtain an image with an effective spatial resolution better than 1 meter per pixel, we used the cPROTO (compensated Pitch and ROll Targeted Observation) technique described and illustrated last year in:
PIA06880: cPROTO Views of Spirit's Rover Tracks and Athabasca Vallis Flood Features 27 September 2004.
Hitting a specific target with the cPROTO technique is challenging, and often it takes 3-4 attempts before we hit. For the candidate Mars Polar Lander location, we made 6 attempts. The first was in April 2005, when the surface was still covered with frost -- that image was saturated white because of the frost. The next attempts were made after the frost had sublimed away -- these were made in July, August, and September 2005. We finally hit the candidate lander location on 27 September 2005.
The figure above compares the features extracted from the earlier, January 2000, image with the same location seen in the new, September 2005, image. The two pictures were taken under nearly identical illumination and atmospheric conditions, almost exactly 3 Mars years apart. The feature identified as a candidate for Mars Polar Lander's parachute is found be the illuminated slope of a small hill. The hill is part of a group of similar hills in the area. The dark feature that was identified as possible rocket blast zone has faded (which would be expected owing to dust deposited by dust storms), but, more importantly, the spot interpreted to be the lander has disappeared. In reality, this spot is a pixel whose value differed from its neighbors in the first image owing to a bigger than average contribution of noise. Close inspection of the January 2000 image (bottom left) shows many small bright and dark blurry spots that do not show up in the September 2005 image (bottom right). There are even smaller, blurry spots in the second image, they are also noise. The fact that these pixels do not coincide is excellent evidence that they are not real features on the surface of Mars.
We conclude that our interpretation of these features was in error. This is NOT the location of the Mars Polar Lander. Because the landing uncertainty ellipse is so much larger than our images, and we do not have another candidate to which to target additional cPROTOs, we cannot continue to hunt for the lander. Finding it now falls to the High Resolution Imaging Science Experiment (HiRISE) presently en route to Mars on-board the Mars Reconnaissance Orbiter (MRO) spacecraft.
Location near: 76.7°S, 195.3°W
The 125 meter scale bar = ~ 410 feet
Illumination from: upper left
Season: Southern Summer (M11-03986 Ls=291.5°; S10-01322 Ls=295.7°)
5 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dust-mantled plain streaked by spring and summertime dust devils in southern Noachis Terra.
Location near: 57.4°S, 336.2°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dozens of layers of sedimentary rock in an unnamed western Arabia crater at 8°N, 7°W. Dark, wind-blown sand and lighter-toned dunes or ripples enhance the apparent contrast in this area. Several faults, indicated by off-set layers, are present. The picture covers an area about 1.5 km (just under 1mi) wide. Sunlight illuminates the scene from the left.
Voir l'image PIA04483: Layers in 8°N, 7°W Crater sur le site de la NASA.
14 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows rugged terrain in northern Arabia Terra. The circular features are the remains of old meteor impact craters -- either the eroded remnants of the interiors of craters, or the remains of craters that were filled by layered material. The martian bedrock has craters of all sizes and states of erosion interbedded with its layered materials.
Location near: 31.4°N, 299.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
29 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark spots and streaks formed in seasonal frost covering terrain in the martian south polar region. This springtime image shows the frost, which formed in the previous autumn and winter, as it is starting to change and sublime away. Dark streaks indicate the direction of winds that have moved some of the defrosting material.
Location near: 84.7°S, 259.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season Southern Spring
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the mysterious dune gullies of Russell Crater. The terrain shown here is one very large sand dune; the surface slopes from upper right toward lower left. Gullies start on the slope at the upper right and indicate flow toward the lower left. These might have formed by the presence of a fluid-either liquid or gas-mixed with sand that avalanched down the dune slope. Or not. Their origin is unknown, although it is known that they tend to occur only on slopes facing southward. The MOC team has re-imaged these gullies several times in the past three Mars years, but no new gullies have formed. The picture covers an area about 3 km (1.9 mi) wide near 54.5°S, 347.3°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04484: Russell Dune Gullies sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows wind-sculpted remnants of layered sedimentary rock that once completely covered the northwestern floor of Henry Crater, an ancient impact basin located at 11.7°N, 336.4°W. These landforms, shaped somewhat like inverted boat hulls, are "textbook examples" of a wind erosion form known as a yardang. The image covers an area 2.3 km (1.4 mi) wide; sunlight illuminates the scene from the left.
Voir l'image PIA04571: Layered Yardangs in Henry Crater sur le site de la NASA.
20 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an impact crater in western Daedalia Planum, around which has developed a wind streak that runs off to the west (left) of the image. The winds responsible for the streak came from the east (right).
Location near: 11.2°S, 139.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
16 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows streamlined landforms carved by catastrophic floods that occurred in the eastern Cerberus region, some time in the distant martian past.
Location near: 15.1°N, 193.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
20 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows varied springtime patterns formed in defrosting, seasonal carbon dioxide frost in the south polar region of Mars. 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: 79.6°S, 125.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
To date, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) narrow angle system has only imaged about 3% of the martian surface. Thus, a new discovery can come at any time, as additional places are covered every day. This MOC image shows a portion of a shallow valley south of Cerberus that was just discovered in April 2003. The valley may have been cut but torrents of mud-laden water; alternatively, an extremely fluid lava was involved. This picture was acquired in May 2003; it covers an area 3 km (1.9 mi) wide and is illuminated from the left. North is toward the top/upper right. The picture is located near 4.6°N, 204.3°W.
Voir l'image PIA04614: Valley South of Cerberus sur le site de la NASA.
2 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark slope streaks formed on dust-mantled mountains of the Lycus Sulci region, west of the giant volcano, Olympus Mons. Despite their fluid-like appearance, dark slope streaks form in very dry dust.
Location near: 18.3°N, 142.4°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
1 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dark wind streak formed in the lee of a crater in Daedalia Planum. The winds responsible for the streak blew from right (east) to left (west).
Location near: 11.7°S, 136.4°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Summer
Among the most exciting places that the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has photographed during its three and a half years in orbit has been this crater in central Noachis Terra. Located at 47°S, 355°W, the crater appears to have been almost completely filled, and subsequently eroded in localized pits, by unknown processes. In this one place we see elements of the two most important results of the MOC investigation--the discovery of young gullies formed by fluid erosion and the occurrence of thick sequences of layered rock attesting to a martian past of substantial geologic activity.
Picture A shows the location of the other two figures, which are sections of three of about a dozen images acquired of this crater. Picture B (M12-00595) shows examples of gullies on the pit walls. Their contributary pattern (including the angles at which they join) argues for fluid behavior during their creation; the dark floors suggest that they have been active recently (or else they, like the slopes around them and most of Mars, would be lighter-toned owing to the accumulation of dust). These gullies are formed well down on the pit wall, where a distinctive, boulder-rich layer is found. Figure C, a mosaic of two high resolution images (M09-00539 and M15-00964), shows an area somewhat higher in the sequence of layered material that fills the crater. This sequence clearly alternates between layers that either contain or erode to form boulders and layers that do not have boulders. Note in particular the overhanging layers near the top center--such overhangs are evidence of the strength of the material. Here, too, gullies appear to start at specific layers; these, however, may not be as young as those seen in (B), as they appear to have at least a thin covering of dust. How it is that this crater came to be filled with layers of material containing (or eroding to create) boulders is a mystery.
Voir l'image PIA03205: Secrets of the Noachian Highlands: Pit Craters sur le site de la NASA.
On the dry, desert planet, Mars, wind is not the only contemporary geologic process that modifies the surface. Gravity also has a role to play. In regions such as Amazonis, Tharsis, and Arabia, most surfaces are covered by mantles of very fine dust. From time to time, an avalanche occurs on a dust-covered slope. This process is happening today, because changes have been observed by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) over the course if its mission, which began in September 1997. This picture shows a variety of dark slope streaks, formed by avalanches of dust, on the walls of a crater in southwest Amazonis near 7.6°N, 171.8°W. The size and shape of each slope streak, including the wide feature near the upper right, is determined by the steepness and texture of the slope on which it occurs. New slope streaks in some regions have been observed to form over periods of less than a few months to a year. This picture was taken in June 2003, and is illuminated from the lower left. The image is 2.3 km (1.4 mi) wide.
Voir l'image PIA04613: Dark Slope Streaks sur le site de la NASA.
4 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a trough formed of coalesced collapse pits in the Tractus Catena region of northern Tharsis, Mars.
Location near: 54.8°S, 0.7°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
1 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a scene reminiscent of some of the Mars Exploration Rover (MER-B), Opportunity, images of terrain in the vicinity of Erebus Crater -- a substrate of light-toned rock, broken into polygonal forms, overlain by large, dark-toned, ripple-like drifts. However, this scene is many hundreds of kilometers away from Meridiani Planum -- it lies on the floor of an old impact crater near the northwest rim of the giant Hellas Basin.
Location near: 21.0°S, 312.0°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a thick mantle of dust covering lava flows north of Pavonis Mons so well that the flows are no longer visible. Flows are known to occur here because of the proximity to the volcano, and such flows normally have a very rugged surface. Fine dust, however, has settled out of the atmosphere over time and obscured the flows from view. The cliff at the top of the image faces north (up), the cliff in the middle of the image faces south (down), and the rugged slope at the bottom of the image faces north (up). The dark streak at the center-left was probably caused by an avalanche of dust sometime in the past few decades. The image is located near 4.1°N, 111.3°W. Sunlight illuminates the scene from the right/lower right.
Voir l'image PIA04515: Dust Mantle Near Pavonis Mons sur le site de la NASA.
If a boulder rolls down a slope on an uninhabited planet, does it make a sound? While we do not know the sound made by a boulder rolling down a slope in the martian region of Gordii Dorsum, we do know that it made an impression. This full-resolution Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a series of depressions made on a dust-mantled slope as a boulder rolled down it, sometime in the recent past. The boulder track is located just right of center in this picture. The boulder sits at the end of the track. This picture was acquired in May 2003; it is located near 11.2°N, 147.8°W. North is toward the lower left, sunlight illuminates the scene from the right. The picture covers an area only 810 meters (about 886 yards) across.
Voir l'image PIA04605: Boulder Track sur le site de la NASA.
29 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows frost-covered sand dunes in the martian north polar region. The winds responsible for these dunes generally blew from the southwest (lower left).
Location near: 80.0°N, 114.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Spring
Mars Global Surveyor (MGS) was launched from Earth just over five years ago on November 7, 1996. It began to orbit Mars on September 12, 1997. After slightly more than four years in orbit, we have now received our 100,000th image from the MGS Mars Orbiter Camera (MOC). For comparison, the Viking 1 and Viking 2 orbiters together returned ~55,000 images during the time they were operational from 1976 to 1980. The Vikings returned about 70 Gbytes of data; MOC has returned 163 Gbytes (after decompression).
MOC's 100,000th image was received on November 5, 2001. Its context frame (below) was received at the same time. The 100,000th image is located near 24.2°N, 127.4°W, in Cyane Sulci, a grouping of ridges northeast of the giant volcano, Olympus Mons. This image shows a valley running diagonally from near the upper right to the lower left, the floor of which is covered by windblown dunes. The slopes on either side of the valley show dark streaks of debris that have slid down from the surrounding ridges. The image has fairly low contrast and a streaked appearance because the atmosphere of Mars was still somewhat hazy following a series of large dust storms that nearly obscured the planet between July and October 2001. Both images are illuminated from the lower left, the high resolution view (above) covers an area 1.5 km (0.9 mi) across, the context view (with white box to indicate location of high resolution view) covers an area 63 km (39 mi) across.
To date, more than two-thirds of all MOC images, covering the first year and a half of pre-mapping operations and the first full Mars year of mapping, have been carefully examined, validated, cataloged, and archived with the NASA Planetary Data System (PDS). To view these first 78,000+ MOC images, visit the MOC Gallery. Work is on-going to similarly process data being collected during the "extended mission" presently underway, which will be archived in future deliveries to the PDS.
Voir l'image PIA03178: MOC's 100,000th Image sur le site de la NASA.
14 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, layered, sedimentary rock outcrops in Becquerel Crater in the western Arabia Terra region. The crater may once have hosted a lake, into which these sediments were deposited. Although the fine, detailed layering in Becquerel was not known until the MGS MOC first began to image these materials in 1999, the presence of a grossly-layered, light-toned feature was known from Viking orbiter images and was speculated from those data to possibly represent evidence for the presence of a former lake.
Location near: 21.5°N, 8.2°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
25 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a summertime view of sand dunes in Richardson Crater in the Mare Chromium region of the martian southern hemisphere.
Location near: 72.4°S, 179.7°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
This MGS MOC image shows erosional streaks on dunes which means that the dunes are indurated (cemented).
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 PIA03176: Dunes in Herschel Crater (Herschel Crater: 15.7 S, 228.8 W) sur le site de la NASA.
27 May 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small, relatively young impact crater in the Xanthe Terra region of Mars. Boulders can be seen in the crater ejecta deposit.
Location near: 2.3°N, 57.8°W
Image width: ~3 km (~1.9 mi
Illumination from: lower left
Season: Northern Autumn
16 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows small barchan dunes on the floor of a crater in western Arabia Terra. Similar dunes are found in most of the larger craters of the region. The steepest slopes on these dunes, their slipfaces, point toward the west-southwest, indicating that dominant winds blow from the east-northeast (upper right).
Location near: 10.9°N, 2.8°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image provides a glimpse of the layered sedimentary rocks in southern Galle Crater. The picture covers an area about 3 km (1.9 mi) wide near 52.3°S, 30.1°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04567: Layers in Galle Crater sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image of layered sedimentary rock outcrops in northern Sinus Meridiani shows several buttes and ridges formed in rock that is somewhat resistant to erosion. The circular feature near the bottom of the picture is an old impact crater that was filled, then buried within the layered material, then later partially exhumed. The sinuous ridge and small buttes to the right of the exhumed crater are composed of the same rock materials that once buried the crater. The picture covers an area about 3 km (1.9 mi) wide near 2.3°N, 353.6°W. Sunlight illuminates the scene from the left.
Voir l'image PIA04492: Meridiani Cliffs and Buttes sur le site de la NASA.
30 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows eroding mesas of frozen carbon dioxide in the martian south polar residual cap. During the summer season, the scarps that bound each pit and mesa in the south polar region become dark as carbon dioxide sublimes away. The darkening might result from the roughening of the surfaces from which ice is subliming, or from the concentration of trace amounts of dust on these slopes, or both.
Location near: 84.7°S, 48.2°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
23 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered sedimentary rocks exposed by erosion, then mantled by dust, in Tikhonravov Crater in central Arabia Terra. Dark slope streaks occur where some of the dust has slid down the layered slopes.
Location near: 13.8°N, 324.8°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
4 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark-toned sand dunes on the floor of the large martian impact crater, Herschel, located in the Terra Cimmeria region of Mars. The winds responsible for these dunes blew from the northeast (upper right).
Location near: 15.7°S, 228.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
Olympus Mons is the largest volcano in the Solar System. While it is considerably taller than Mount Everest, its slopes tend to be 1° to 5° over most of the volcano. With such low slopes, one would not really "climb" to the summit of Olympus Mons, one would instead hike. This very high resolution Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view of the middle western flank of Olympus Mons shows, however, that it would not be an easy place to hike. The surface is rugged, with many overlapping lava flow structures, all of which are mantled by a thick blanket of dust and wind-scoured sediment. This image is near 19.9°N, 135.5°W, and illuminated from the lower left.
Voir l'image PIA04583: Flows on Olympus Mons sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a pattern of polygonal cracks and aligned, elliptical pits in western Utopia Planitia. The picture covers an area about 3 km (about 1.9 mi) wide near 44.9°N, 274.7°W. Sunlight illuminates the scene from the left.
Voir l'image PIA04476: Utopia Cracks and Polygons sur le site de la NASA.
20 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a crater in the Memnonia region of Mars, around which has formed a wind streak. The bright streak is in the lee of the crater -- that is, it is on the crater's down-wind side. Thus, the winds responsible for the streak blew from the southeast (lower right).
Location near: 6.7°S, 141.4°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
11 September 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows heavily-cratered lava flows on the slopes of the martian volcano, Ascraeus Mons. The mountain is a classic shield volcano, similar in many respects to the volcanoes of Hawai'i. Shield volcanoes typically form from silica-, oxygen-, and aluminum-bearing rocks that are enriched in iron and magnesium -- that is, basalt. The lava flows of Ascraeus Mons are most likely basaltic, as are the volcanic rocks in Gusev Crater that were examined by the Mars Exploration Rover, Spirit, during its first year on the martian surface.
Location near: 10.3°N, 103.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
6 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, windblown sand dunes in the caldera of Nili Patera, a volcanic crater in Syrtis Major. The dunes were formed by winds blowing from the northeast (upper right).
Location near: 9.0°N, 292.9°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season Northern Autumn
Two Earth years ago, NASA's Mars Exploration Rover Spirit touched down in Gusev Crater. The rover marked its first Mars-year (687 Earth days) anniversary in November 2005. Shortly before Spirit's Martian anniversary, the Mars Orbiter Camera on NASA's Mars Global Surveyor acquired an image covering approximately 3 kilometers by 3 kilometers (1.9 miles by 1.9 miles) centered on the rover's location at that time in the "Columbia Hills."
"Husband Hill," the tallest in the range, is just below the center of the image. The image has a resolution of about 50 centimeters (1.6 feet) per pixel. North is up; illumination is from the left. The location is near 14.8 degrees south latitude, 184.6 degrees west longitude.
The image was acquired on Nov. 2, 2005. A white box (see Figure 1) indicates the location of an excerpted portion on which the location of Spirit on that date is marked. Dr. Timothy J. Parker of the Mars Exploration Rover team at the NASA's Jet Propulsion Laboratory, Pasadena, Calif., confirmed the location of the rover in the image. The region toward the bottom of the image shows the area where the rover is currently headed. The large dark patch and other similar dark patches are accumulations of windblown sand and granules.
12 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the solidified remains of flows -- probably lava, but possibly mud --in the Zephyria region of Mars, south of Cerberus.
Location near: 5.2°N, 203.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
15 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows rugged terrain in the Nestus Valles portion of northern Memnonia. Wind erosion has scoured the landscape. Dust, deposited after the wind erosion occurred, mantles the scene. Dark streaks have formed by avalanching of the fine, dry dust on some of the slopes in the region.
Location near: 6.8°S, 158.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
2 September 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a patch of frost-covered, dark sand that, at the time the picture was acquired in June 2005, had begun to defrost. The frost is carbon dioxide. Dunes and other patches of sand are usually the first polar features to develop dark spots as the frost begins to sublime away.
Location near: 78.9°S, 80.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
23 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows mesas in northeastern Arabia Terra. This heavily-cratered region of Mars has been severely eroded, although very little evidence regarding the erosive processes has been preserved.
Location near: 26.9°N, 293.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
A 50-cm contour map of part of Mars' south polar ice cap. The region shown is roughly a kilometer on a side. The shaded relief model is shown with a tenfold vertical exaggeration.
This high resolution Mars Global Surveyor (MGS) topographic model of the surface of Mars is created by combining Mars Orbiter Laser Altimeter (MOLA) gridded topographic data base with information from Mars Orbiter Camera (MOC) Narrow Angle (NA) high resolution images. The top image is a shaded relief model derived from the MGS MOLA gridded topography for a small part of the cap near 87°S 348°W; the area covered is about 3x3 km and the MOLA resolution about 230 meters/pixel. The bottom image is an enhanced shaded relief model of the same area derived by adding high-resolution topographic information from a MOC NA image data to the MOLA topography model. This yields a 3-D model that has a horizontal resolution of 2.75 meters; both models are shown with a 10x vertical exaggeration. Using shape-from-shading or photoclinometry techniques, MOCNA image m0906496 was used to derive high resolution (meter-scale) topography. The photometric properties of the surface, including albedo variations, and scattering of the atmosphere were carefully modeled by constraining the low-frequencies of the MOC NA photoclinometry model to match the high-quality MOLA data.
Voir l'image PIA03874: Derived Topographic Model from Mars Global Surveyor Instruments sur le site de la NASA.
5 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dust-mantled, wind-eroded landscape in the Medusae Sulci region of Mars. Wind eroded the bedrock in this region, and then, later, windblown dust covered much of the terrain.
Location near: 5.7°S, 160.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
27 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some of the light-toned, layered, sedimentary rock outcrops in northern Terby Crater. Terby is located along the north edge of Hellas Planitia. The sedimentary rocks might have been deposited in a greater, Hellas-filling sea -- or not. Today, the rocks are partly covered by dark-toned sediment and debris.
Location near: 27.2°S, 285.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows large, relatively bright ripples of windblown sediment in the Sinus Sabaeus region south of Schiaparelli Basin. The surrounding substrate is thickly mantled by very dark material, possibly windblown silt that settled out of the atmosphere. The picture is located near 7.1°S, 343.7°W. Sunlight illuminates the scene from the left.
Voir l'image PIA04584: Large, Bright Wind Ripples sur le site de la NASA.
17 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a frost-covered surface in the south polar region. The substrate beneath the frost is cracked, and seasonal frost surrounding each crack has begun to sublime away, creating a distinct pattern of dark streaks in this September 2005 scene.
Location near: 85.3°S, 288.4°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
13 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows gullies cut into layered rock and debris on the wall of a south middle-latitude crater. Gullies such as these are common at middle latitudes and may have required water to form.
Location near: 41.1°S, 204.8°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
31 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a crater formed in light-toned, layered, sedimentary rocks in Meridiani Planum. This crater is located approximately 55 kilometers (~34 miles) southwest of the Mars Exploration Rover, Opportunity, site. Erosion of sedimentary rock layers around the crater rim has caused an uneven retreat, resulting in the formation of U-shaped alcoves where undermining and collapse have occurred. Dark material in this scene is probably sand and granules, similar to the dark surfaces explored by the Opportunity rover.
Location near: 3.1°S, 5.8°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
30 May 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, wind-eroded, sedimentary rock outcrops in eastern Candor Chasma, part of the Valles Marineris trough system.
Location near: 7.7°S, 65.3°W
Image width: ~3 km (~1.9 mi
Illumination from: lower left
Season: Southern Spring
Now in its Extended Mission, Mars Global Surveyor (MGS) is into its second Mars year of systematic observations of the red planet. With the Extended Mission slated to run through April 2002, the Mars Orbiter Camera (MOC) is being used, among other things, to look for changes that have occurred in the past martian year. Because Mars is farther from the Sun than Earth, its year is longer--about 687 Earth days.
The two pictures shown here cover the same portion of Lycus Sulci, a rugged, ridged terrain north of the giant Olympus Mons volcano. The interval between the pictures span 92% of a martian year (August 2, 1999 to April 27, 2001). Dark streaks considered to result from the avalanching of dry, fine, bright dust are seen in both images. The disruption of the surface by the avalanching materials is thought to cause them to appear darker than their surroundings, just as the 1997 bouncing of Mars Pathfinder's airbags and the tire tracks made by the Sojourner rover left darkened markings indicating where the martian soil had been disrupted and disturbed. The arrows in the April 2001 picture indicate eight new streaks that formed on these slopes in Lycus Sulci since August 1999. These observations suggest that a new streak forms approximately once per martian year per kilometer (about 0.62 miles) along a slope.
In both images, north is toward the top/upper right and sunlight illuminates each from the left. Dark (as well bright) slope streaks are most common in the dust-covered martian regions of Tharsis, Arabia, and Elysium.
Voir l'image PIA03226: Changes Over a Martian Year -- New Dark Slope Streaks in Lycus Sucli sur le site de la NASA.
2 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some of the platy flow material in the Zephyria region of Mars. The materials have impact craters in them, suggesting that they are composed of solid rock rather than ice. Some investigators have proposed that these materials are part of a vast ice-covered lake or sea, but the impact craters formed in the material suggest that it is not ice. Other investigators have cited evidence for an origin by very fluid lavas; some of the evidence includes small volcanoes scattered throughout the region.
Location near: 3.7°S, 195.5°W
Image width: ~3 km (~1.9 mi
Illumination from: upper left
Season: Southern Winter
20 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, layered, sedimentary rock outcrops in an unnamed crater located at 8°N, 7°W. Dark, windblown sand enhances the contrast in this view. Hundreds of layers of repeated thickness and physical properties suggest that a cyclic or at least episodic process acted over a considerable period of time to deposit these materials in the crater. At the time the sediments were deposited, the crater might have hosted a lake.
Location near: 6.1°N, 10.7°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
9 September 2005
Early on 8 September 2005 (Universal Time), the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) resumed imaging of Mars after a nearly 2-week hiatus to recover the spacecraft from a glitch that put MGS into a protective "safe mode." The MOC was turned on during MGS orbit 29053, while the spacecraft was flying across day side of the planet. MOC then resumed taking pictures on the next orbit, 29054. Shown here is a portion of the first picture acquired following MOC turn-on. The image shows a view of the martian south polar region, as it appeared on 8 September 2005. The image was taken by MOC's red wide angle camera. In this case, the spacecraft began imaging Mars as it passed across the southern terminator, at the bottom of the image. MGS then flew southward, over the polar cap, then northward toward the equator. The equatorial region is further north than the area shown here. The image not only provided the MOC team a confirmation that MOC imaging has resumed, this particular image, in the map-projected form shown here, is being used by the team to assist in setting the exposures for MOC narrow angle camera images that will be acquired from the south polar region over the next several days.
Location near: 90°S
Illumination from: upper left
Season: Southern Summer
Voir l'image PIA04287: MOC Imaging Resumes sur le site de la NASA.
This mosaic of two Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) narrow angle camera images, one from 2001, the other from 2003, shows light-toned, layered, sedimentary rock outcrops exposed on the floor of a trough that parallels Coprates Chasma in the Valles Marineris system. Layered rocks form the pages from which the history of a place can be read. It may be many years before the story is read, but or now at least we know where one of the books of martian history is found. This picture is located near 15.2°S, 60.1°W. Sunlight illuminates the scene from the left.
Voir l'image PIA04637: Sedimentary Rock Near Coprates sur le site de la NASA.
30 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows complexly-eroded terrain within a partially-filled impact crater in Noachis Terra.
Location near: 48.5°S, 336.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
22 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows details in eroded bedrock among the mountains of western Argyre. Smooth, dark areas are patches of windblown sand.
Location near: 48.0°S, 55.1°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
5 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows gullies formed in the walls of an impact crater. Such gullies might result from seepage and runoff of groundwater; others have suggested snowmelt might be involved, although there is no evidence for snow at this location.
Location near: 35.7°S, 207.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
July 4, 2003, is the 6th anniversary of the Mars Pathfinder landing. One of the elements carried to the red planet by Pathfinder was the Wind Sock Experiment. This project was designed to measure wind activity by taking pictures of three aluminum "wind socks." While the winds at the Mars Pathfinder site did not blow particularly strong during the course of that mission, dust storms seen from orbit and Earth-based telescopes attest to the fact that wind is a major force of change on the dry, desert surface of Mars today. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) narrow angle image shows dark sand dunes and lighter-toned ripples trapped among the mountainous central peak of an old impact crater in Terra Tyrrhena near 13.9°S, 246.7°W. The dune slip faces--the steepest slope on the larger dunes--indicate sand transport is from the top/upper left toward the bottom/lower right. North is toward the top/upper right; the picture is 3 km (1.9 mi) across. Sunlight illuminates the scene from the upper left. This picture was obtained in April 2003.
Voir l'image PIA04612: Windblown Dunes and Ripples sur le site de la NASA.
6 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered material exposed on a slope in the south polar region of Mars. The composition of the layers, and whether they contain ice, is not known.
Location near: 87.0°S, 176.1°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
This picture of sand dunes in Wirtz Crater was obtained by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in early October 2002. The shape of the dunes indicates that wind has been transporting the sand from the southwest toward the northeast (lower left toward upper right). The picture covers an area about 3 km (1.9 mi) wide and is located near 48.6°S, 25.5°W. Sunlight illuminates the scene from the upper left.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image portrays a plethora of dark streaks created by passing dust devils during early summer in the martian southern hemisphere. The picture covers an area about 3 km (1.9 mi) wide near 40.2°S, 237.7°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04502: Martian Dust Devil Tracks sur le site de la NASA.
21 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows martian sediment in two basic forms: (1) light-toned, layered, sedimentary rock outcrops and (2) dark, windblown sand dunes. The dark sand of the dunes is most likely composed of grains rich in iron-, magnesium-, aluminum-, and silicon-bearing minerals. The hills and mounds of layered sedimentary rock were once more extensive, covering the entire scene shown here, which occurs on the floor of a crater in western Arabia Terra.
Location near: 8.9°N, 1.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
3 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a trough formed of coalesced collapse pits in the Tractus Catena region of northern Tharsis, Mars.
Location near: 30.6°N, 99.3°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
Although most of the best examples of layered sedimentary rock seen on Mars are found at equatorial and sub-tropical latitudes, a few locations seen at mid- and high-latitudes suggest that layered rocks are probably more common than we can actually see from orbit. One extremely good example of these "atypical" layered rock exposures is found in the 72 km-diameter (45 miles) crater, Spallanzani (58.4°S, 273.5°W). Located southeast of Hellas Planitia, the crater is named for the 18th Century Italian biologist, Lazzaro Spallanzani (1729-1799). Picture A presents a composite of the best Viking orbiter image (VO2-504B55) of the region with 4 pictures obtained June 1999 through January 2001 by the Mars Global Surveyor Mars Orbiter Camera (MOC). Each MOC narrow angle image is 3 km across. Taken in the MOC's "survey mode," all four images were acquired at roughly 12 meters (39 ft) per pixel. Picture B zooms-in on the portion of the composite image that includes the 4 MOC images (the 100%-size view is 20 m (66 ft) per pixel). Other craters in the region near Spallanzani show features--at Viking Orbiter scale--that are reminiscent of the layering seen in Spallanzani. Exactly what these layers are made of and how they came to be where we see them today are mysteries, but it is possible that they are similar to the materials seen in the many craters and chasms of the equatorial latitudes on Mars.
Voir l'image PIA03203: Mid-Latitude Sedimentary Rock: Spallanzani Crater sur le site de la NASA.
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image mosaic was constructed from data acquired by the MOC red wide angle camera. The large, circular feature in the upper left is Aram Chaos, an ancient impact crater filled with layered sedimentary rock that was later disrupted and eroded to form a blocky, "chaotic" appearance. To the southeast of Aram Chaos, in the lower right of this picture, is Iani Chaos. The light-toned patches amid the large blocks of Iani Chaos are known from higher-resolution MOC images to be layered, sedimentary rock outcrops. The picture center is near 0.5°N, 20°W. Sunlight illuminates the scene from the left/upper left.
Voir l'image PIA04485: Aram and Iani Chaos sur le site de la NASA.
Many craters and troughs at polar and middle latitudes on Mars have gullies carved in their walls. These gullies may have formed by running water; others have suggested alternative, exotic fluids such as liquid or gaseous carbon dioxide. This view of martian gullies was acquired by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC). The image shows gullies in the wall of an old meteor impact crater near 39.0°S, 200.7°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04570: Gullies in Crater Wall sur le site de la NASA.
15 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a frost-covered surface in the martian south polar region. As the seasonal frost begins to sublime away, local variations in surface texture-mostly dendritic cracks, in this case-lead to early defrosting in some areas. Those areas already defrosted appear dark in the image.
Location near: 79.1°S, 340.1°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
25 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a gullied crater wall in the Terra Sirenum region of Mars. The fluids that formed the gully channels and deposited debris in aprons at the base of the crater wall may have percolated through layers in the layered bedrock exposed in the crater wall. As fluid seeped out of the ground, it undermined overlying layers of rock, and caused the formation of several compex alcoves, higher in the crater wall. The formation of alcoves requires the undermining and collapse of layered material at a point where the channel begins; this is a key observation supporting the hypothesis that martian gullies require groundwater, not snowmelt or other exotic processes or fluids, to form.
Location near: 37.3°S, 153.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
This high resolution Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows eroded, layered sedimentary rock exposures in an unnamed western Arabia Terra crater at 8°N, 7°W. The dark material is windblown sand; much of the erosion of these layers may have also been caused by wind. Sunlight illuminates the scene from the left.
Voir l'image PIA04542: Eroded Sedimentary Rock sur le site de la NASA.
9 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of a lava flow in the Daedalia Planum region of Mars, south of the volcano, Arsia Mons. Daedalia Planum is known for its abundance of ancient, long, lava flows.
Location near: 22.7°S, 116.9°W
Image width: ~3 km (~1.9 mi
Illumination from: upper left
Season: Southern Spring
Dark, windblown sand dunes have over-ridden a suite of low, somewhat rectilinear ridges on the floor of an impact crater near 36.5°S, 219.0° W, in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image acquired in May 2003. The dune field is located in Terra Cimmeria. The image is 1.2 km (3/4 mile) wide; sunlight illuminates the scene from the upper left.
Voir l'image PIA04539: Ridges and Sand Dunes sur le site de la NASA.
28 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a view of linear troughs and mesas formed in the frozen carbon dioxide of the martian south polar residual cap. This image, obtained in May 2005, is a reminder that not all of the south polar cap landscapes resemble "swiss cheese."
Location near: 86.7°S, 24.8°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
21 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a cratered surface in the Tempe Terra region of the red planet. One of the goals of the MOC Picture of the Day series is to present images that capture the range and variety of surface features seen by MOC all over Mars. This view presents a fairly typical scene from the plains northeast of the Tharsis region.
Location near: 31.0°N, 84.1°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
The martian north polar ice cap is surrounded by fields of dark, windblown sand dunes. This March 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dunes near 76.5°N, 264.7°W. The steep dune slip faces indicate wind transport of sand from the lower left toward the upper right. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04620: North Polar Sand Dunes sur le site de la NASA.
25 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of south mid-latitude gullies on a crater wall. Gullies such as these may have formed by runoff of liquid water.
Location near: 38.0°S, 167.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
9 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the floor and walls of a small portion of Nirgal Vallis. The floor is covered by large windblown ripples. The valley wall near the center right exhibits a group of gullies, formed perhaps by a combination of mass movement and possibly seepage and runoff of groundwater.
Location near: 28.2°S, 42.2°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
18 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows exposures of light-toned, layered, sedimentary rock among dark-surfaced plains in northern Sinus Meridiani. The circular feature in the southeast (lower right) corner of the image is a wedding-cake-like tower of sedimentary rocks.
Location near: 2.9°N, 359.9°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
17 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an ancient lava flow surface near the volcano, Ascraeus Mons. The volcanic material has been completely covered by thick accumulations of dust. An earlier accumulation of dust or ash was eroded by wind to form the sharp, nearly triangular hills and ridges seen on top of the flow surfaces. A small impact crater with bouldery ejecta has formed on top of the old flow material in the southern (lower) quarter of the image.
Location near: 8.5°N, 110.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
14 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.5 meters per pixel (~5 ft/pixel) view of a pair of small meteor impact craters in the Arena Colles region of Mars, located north of Isidis Planitia.
Location near: 22.7°N, 278.5°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
18 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark-outlined polygons on a frost-covered surface in the south polar region of Mars. In summer, this surface would not be bright and the polygons would not have dark outlines--these are a product of the presence of seasonal frost.
Location near: 77.2°S, 204.8°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
23 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes in the north polar region of Mars. Surrounding much of the north polar ice cap are fields of sand dunes. In this case, the strongest winds responsible for the dunes blew off the polar cap (not seen here), from the north-northwest (upper left).
Location near: 76.5°N, 63.7°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Summer
1 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small portion of a broad, shallow channel system located on the plains northeast of Olympus Mons. Several similar valley/channel systems occur near Olympus Mons, and all of them are mysterious in terms of the nature of the fluids involved-- Was it water? Lava? Mud?
Location near: 20.8°N, 125.0°W
Image width: ~3 km (~1.9 mi
Illumination from: lower left
Season: Northern Summer
21 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dust-mantled crater in central Arabia Terra. Light and dark slope streaks have formed on the crater walls, as dry dust has slid down the slopes.
Location near: 12.7°N, 319.1°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
In an effort to save fuel so that the Mars Global Surveyor (MGS) mission can be extended additional years into the future (in order to act as a relay for entry, descent, and landing telemetry from the Mars Exploration Rover mission in early 2004), the spacecraft was re-oriented in mid-August 2001 such that it no longer points the camera and other science instruments straight down at Mars (i.e., towards its nadir). Now it points about 16° off-nadir. For the Mars Orbiter Camera (MOC) experiment, this new orientation, known among MGS teams as "Relay-16" (because it enables the "relay mission" and has an offset of 16°), has resulted in a tremendous increase in the number of opportunities to acquire high resolution stereo (3-D) views of the martian surface. Ideally, an image taken during the Mapping Mission when the spacecraft was pointing nadir is repeated within a week or two of its first Mars anniversary--i.e., 1 Mars year after it was first acquired--so that the illumination conditions are close to the same in the two images.
The 3-D anaglyph shown here is an example of the on-going effort to acquire rRelay-16 stereo during the MGS Extended Mission. The first picture used to make this image, M13-01484, was acquired March 21, 2000. Nearly 1 Mars year later, the second image, E12-02584, was taken on January 23, 2002. Together, the images show eroded, pitted, light-toned layer outcrops in Iani Chaos near 4.4°S, 18.6°W. The layered materials may be ancient sedimentary rocks. The image covers an area 26 km (16 miles) by nearly 3 km (1.9 mi) wide, and is illuminated from the top left.
To see this image in stereo vision, you must use "3-D" glasses (red in left eye, blue in right). To see the original image from March 2000, visitM13-01484 in the MOC Gallery.
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 PIA03472: Stereo View of Layer Outcrops in Iani Chaos sur le site de la NASA.
11 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows severely tilted--dipping--layered rocks in Oudemans Crater in the Valles Marineris region of Mars. The rocks have a light tone and are somewhat broken-up by faults. These rocks were deposited in flat-lying layers. Sometime later, Oudemans Crater formed by meteor impact. When that occurred, rocks that were underneath the site of the impact were uplifted and tilted by the force of the impact. The light tone and repeated nature of some of the layers suggests that these may be sedimentary rocks.
Location near: 10.2°S, 92.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Spring
8 September 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows outcrops of light-toned, sedimentary rock among darker-toned mesas in Aram Chaos. Dark, windblown megaripples -- large ripples -- are also present at this location.
Location near: 3.0°N, 21.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
Extensional faulting, wherein some fraction of the martian crust is pulled apart and faults are formed where the bedrock breaks, has also led to formation of collapse pits in the Tractus Fossae region. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows one such pit and the layered bedrock exposed in its walls. Dark streaks on the slopes of the pit result from avalanches of dry, fine-grained debris (probably dust, as these streaks are only found in the dust-mantled regions of Mars). This pit is located near 23.5°N, 103.8°W. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04636: Tractus Fossae Collapse Pit sur le site de la NASA.
14 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a circular depression and a suite of eroding mesas of carbon dioxide. These features occur in the south polar residual cap of Mars. The eroding carbon dioxide creates landforms reminiscent of "Swiss cheese." The circular feature might indicate the location of a filled, buried impact crater.
Location near: 86.8°S, 111.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
Beneath the northern plains of Mars are numerous buried meteor impact craters. One of the most heavily-cratered areas, although buried, occurs in Utopia Planitia, as shown in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image. The history of Mars is complex; impact craters provide a tool by which to understand some of that history. In this case, a very ancient, cratered surface was thinly-buried by younger material that is not cratered at all. This area is near 48.1°N, 228.2°W; less than 180 km (112 mi) west of the Viking 2 lander site. Sunlight illuminates the scene from the lower left.
Voir l'image PIA04526: Buried Craters of Utopia sur le site de la NASA.
26 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a field of secondary craters located on the plains north of Ares Vallis, roughly 30 or 35 kilometers (19-22 miles) northeast of the Mars Pathfinder landing site. These craters did not form directly by individual meteor impacts-they resulted from the impact of material ejected from a much larger meteor impact that occurred somewhere to the south of the region.
Location near: 19.9°N, 33.3°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images acquired in 1999 and 2001 suggested that each Mars year, for the past several hundred years (if not thousands), the layered carbon dioxide ice of the south polar residual cap has been disappearing. Scarps formed by sublimation of these icy layers retreat at an average rate of about 3 meters (~3 yards) per Martian year.
MOC is now in its third Mars year of detailed exploration of the red planet. Recently, southern spring began, and the south polar cap emerged from winter darkness. The first picture shown here (top) was obtained by MOC less than a week ago (May 2003). The second picture shows the same area of the south polar residual cap, as it appeared 2 Mars years earlier in August 1999. Comparison shows that, between 1999 and 2003, several small mesas and buttes vanished, holes grew larger, and more cracks and pits appeared as carbon dioxide was removed from the polar cap.
The image pair is located near 86.8°S, 109.0°W. Sunlight illuminates both from the upper right. One Mars year is about 687 Earth days long.
Voir l'image PIA04528: Two Mars Years of South Polar Change sur le site de la NASA.
15 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of the enigmatic valley of the Olympica Fossae region. Unknown is whether water, lava, or mud, or some combination of these things, once poured through the valley system.
Location near: 24.2°N, 115.7°W
Image width: ~2 km (~1.2 mi)
Illumination from: lower left
Season: Northern Autumn
4 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a polgyon-cracked surface, into which deep, somewhat kidney-bean-shaped pits have formed. These are landscapes of the martian south polar residual cap. This view was captured during May 2005.
Location near: 86.9°S, 5.1°W
Image width: ~1.5 km (~0.9 mi)
Illumination from: upper left
Season Southern Spring
Two Earth years ago, NASA's Mars Exploration Rover Spirit touched down in Gusev Crater. The rover marked its first Mars-year (687 Earth days) anniversary in November 2005. On Nov. 2, 2005, shortly before Spirit's Martian anniversary, the Mars Orbiter Camera on NASA's Mars Global Surveyor acquired an image centered on the rover's location in the "Columbia Hills." The location of Spirit on that date is circled on the image on the right. On the left, for comparison, is an image from Jan. 10, 2004, when few dreamed that the Spirit would ever reach the hills from its landing site about three kilometers (two miles) away.
The newer image has a resolution of about 50 centimeters (1.6 feet) per pixel. North is up; illumination is from the left. The location is near 14.8 degrees south latitude, 184.6 degrees west longitude. Dr. Timothy J. Parker of the Mars Exploration Rover team at NASA's Jet Propulsion Laboratory, Pasadena, Calif., confirmed the location of the rover in the 2005 image. The scale bar is 50 meters (164 feet).
1 September 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an impact crater cut by troughs which formed after the crater formed. The crater and troughs have large windblown ripples on their floors. The ripples, troughs, craters, and other surfaces in this scene have all been mantled by dust. Dark streaks on slopes indicate areas where avalanches of dry dust have occurred. These features are located on Sacra Mena, a large mesa in the Kasei Valles region.
Location near: 25.4°N, 66.8°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
22 October 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the broken, platy texture of flow surfaces in the Zephyria region of Mars. Some investigators have suggested that these materials represent the remains of an ice-covered lake; others suggest that these are the surfaces of hardened lava that -- when it was erupting -- was very hot and fluid. Although not illustrated here, a key piece of evidence against the ice-covered lake hypothesis is that there are some small craters formed on these surfaces (one can be seen in the lower left/southwest corner), and some of them have boulders in their ejecta. The boulders indicate that the material is rock-solid.
Location near: 5.3°N, 208.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
6 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows shows a suite of small, dark sand dunes on the floor of a crater in western Arabia Terra. The winds responsible for these dunes generally blow from the east/southeast (right/lower right).
Location near: 6.3°N, 349.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Northern Summer
3 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows yardangs, a ridge-and-groove landform produced by wind erosion of a granular, sand-rich bedrock. These are located west-southwest of the volcano, Olympus Mons. Yardangs are common on Mars, especially in the regions west and southwest of Olympus Mons, in southern Amazonis Planitia.
Location near: 14.8°N, 146.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
A sequence of layered, sedimentary rock, more than 1 km (0.62 miles) thick, once filled or nearly filled Terby Crater, a basin just north of Hellas Planitia. The sedimentary rocks were eroded and exposed so that today, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) regularly takes pictures of these outcrops in an effort to better understand them. Exposures of sedimentary rock on Mars are extremely important because they show that the planet has a rich, diverse history. However, an opportunity to read the history recorded in these rocks may still be many years away. This image is near 27.6°S, 285.9°W. The picture is illuminated from the upper left.
Voir l'image PIA04582: Terby Crater Layers sur le site de la NASA.
23 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned rock outcrops in northeastern Sinus Meridiani. The entire northern Sinus Meridiani region has vast exposures of light-toned, layered rock, covering an area many times greater than that of all the famous sandstone, limestone, and shale outcrops of northern Arizona and southeastern Utah. The rocks in this image are probably similar to those explored by the Mars Exploration Rover, Opportunity, but probably are of a different age and position in the region's geologic history.
MGS MOC and Mars Odyssey THEMIS images were recently used to describe the complex geology of the Sinus Meridiani region, as detailed in the open access Mars journal article, "The sedimentary rocks of Sinus Meridiani: Five key observations from data acquired by the Mars Global Surveyor and Mars Odyssey orbiters," by Malin Space Science Systems' K. S. Edgett. The paper is available at: doi:10.1555/mars.2005.0002.
Location near: 0.3°S, 356.0°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Southern Summer
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows rocky, dust-mantled buttes in a terrain similar to the Monument Valley of Utah/Arizona, located southwest of the Cerberus region. Boulders the size of large houses have tumbled down into the valleys between the buttes. The picture covers an area about 1.5 km (just under 1 mi) wide near 3.3°N, 212.4°W. Sunlight illuminates the scene from the left.
Voir l'image PIA04477: Buttes South of Cerberus sur le site de la NASA.
10 September 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an inverted valley in eastern Arabia Terra. The relatively flat-topped ridge that runs down much of the length of this picture was once the floor, or a material covering the floor, of an ancient martian valley. The floor material was harder and more resistant to erosion than the rocks into which the valley had been cut. Thus, erosion removed the rocks that were cut by the valley, and then removed additional rocks that were lower than the valley floor, leaving what was once a valley as a high-standing ridge.
Location near: 11.4°N, 312.9°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Autumn
19 June 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark spots formed in carbon dioxide frost that covers the surfaces of patches of sand in the south polar region. As spring arrived this year in the martian southern hemisphere, so began the annual defrosting process. The fact that sand dunes begin to defrost earlier than other surfaces, and that the defrosting process involves the formation of spots like these, has been known since the earliest days of the MGS mission.
Location near: 66.8°S, 15.7°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
7 July 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, windblown sand dunes in the caldera of Nili Patera, a volcanic crater in Syrtis Major. The dunes were formed by winds blowing from the northeast (upper right).
Location near: 16.0°N, 93.1°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season Northern Autumn
4 September 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, layered, sedimentary rocks exposed by erosion in Terby Crater, located on the north rim of the Hellas Basin. Sedimentary rocks are common on Mars; the light tone of the rocks here suggests that they might bear some similarity to the sedimentary rocks of Meridiani Planum, explored by the Mars Exploration Rover, Opportunity. Water was likely involved in the alteration of the rocks, and perhaps in their deposition as sediments, long ago.
Location near: 27.9°S, 285.6°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
2 November 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, layered, sedimentary rock exposures in Terby Crater, just north of Hellas Planitia. These rocks might have formed from sediment deposited in a lake or a larger Hellas-filling sea.
Location near: 28.0°S, 285.4°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
31 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of a shallow channel carved in the plains of the Zephyria region of Mars. This feature might be the result of the passing of either extremely fluid lava or, perhaps, mud.
Location near: 5.1°N, 203.7°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
24 December 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a full-resolution (1.5 meters/5 feet per pixel) view of an old meteor impact crater, somewhat filled with sediment. This crater is located near a larger crater, Newcomb, in far northern Noachis Terra.
Location near: 22.1°S, 1.1°W
Image width: ~1 km (~0.6 mi)
Illumination from: upper left
Season: Southern Spring
One of the earliest results of the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) investigation shortly after the spacecraft began to orbit Mars in 1997 was the discovery of layered rock outcrops reaching deep down into the martian crust in the walls of the Valles Marineris. Since that time, thousands of MOC images have revealed layered rock in a variety of settings--crater floors, canyon interiors, and scarps exposed by faulting and pitting. This spectacular example taken by MOC in 2001 is found on the floor of an impact crater located near the equator in northwestern Schiaparelli Basin (0.15°N, 345.6°W). The image covers an area approximately 3 km (1.9 miles) across and is illuminated by sunlight from the upper left. Layers of uniform thickness and appearance suggest that these materials are ancient sediments, perhaps deposited in water, or perhaps deposited by wind. Wind has subsequently eroded and exposed the layers. Dark drifts of sand occur at the lower center of the image, and lighter-toned windblown ripples dominate the center and upper right.
Voir l'image PIA03177: Ancient Layered Rocks in Schiaparelli Crater sur le site de la NASA.
Compare each image on the left with their counterparts on the right. Small hills vanished and pit walls expanded between 1999 and 2001. The pits are formed in frozen carbon dioxide, and the carbon dioxide is subliming away a little more each Martian year. Sunlight illuminates each of the four different scenes from the upper left.
CLICK HERE for animation of all 4 of these panels (6.2 MBytes).
One of the most profound benefits of being able to continue photographing Mars in the Mars Global Surveyor (MGS) Extended Mission is the opportunity to go back and re-image a site that was seen in the previous martian year. New MGS Mars Orbiter Camera (MOC) images have provided a startling observation: The residual martian south polar cap is changing. The fact that it is changing suggests that Mars may have major, global climate changes that are occurring on the same time scales as Earth's most recent climate shifts, including the last Ice Age.
MOC images of the south polar cap taken in 1999 were compared with images of the same locations taken in 2001, and it was discovered that pits had enlarged, mesas had shrunk, and small buttes had vanished. In all, the scarps that enclose the pits and bound the mesas and buttes retreated about 3 meters (3.3 yards) in 1 martian year (687 Earth days). This rapid retreat of polar scarps can only occur if the ice is frozen carbon dioxide (also known as "dryice"). Retreat of scarps made of water ice is much slower and would not have been measurable from one martian year to the next.
The portion of the martian south polar cap that persists through summer is called the residual polar cap. The two sets of four pictures shown here are from four places on the residual south polar cap. The pictures from 1999 were taken in October of that year, the corresponding pictures from 2001 were acquired in August, approximately 1 Mars year after the 1999 images were obtained. In each case, the pictures are illuminated by sunlight from the upper left, and each shows an area about 250 meters (273 yards) across. The polarcap is layered, and the layers have eroded to form pits, troughs, mesas, and buttes. The pits form as sunlight warms frozen carbon dioxide during southern spring and summer, and the ice sublimes away. There is so much carbon dioxide that it does not all go away in one summer--in fact, it may take hundreds to thousands of years to disappear.
These new observations indicate that the south polar residual cap is not permanent. It is disappearing, a little bit more each southern spring and summer season. At the present rate, a layer 3 m thick can be completely eroded away in a few tens of martian years. Since each layer is equivalent to about 1% of the mass of the present atmosphere (which is 95% carbon dioxide), if sufficient carbon dioxide is buried in the south polar cap, the mass of the atmosphere could double in a few hundred to a thousand Mars years. That could lead to profound changes in the environment. For example, it would change how much and where wind erosion would occur, and where and for how long liquid water could survive at or near the surface.
It also means that Mars may have been very different in the recent past (perhaps only a few thousands of years ago). On today's Mars, the ice is eroding, but in the past that material had to have been deposited. The martian climate was probably colder, and there was more carbon dioxide in the atmosphere. For some reason, large amounts of carbon dioxide froze at the south pole--one might say that there was a "Martian Ice Age"--and this freezing occurred on a time scale similar to that of the most recent Ice Age on Earth.
Mars is changing, and it is changing on a time scale that we can measure and observe. If all of the carbon dioxide that is being released into the atmosphere from the south polar cap is not freezing out somewhere else, and if it is not being adsorbed into the martian soil, then it must be causing the atmospheric pressure to increase. If this so, and if one were to assume that the entire known volume of the polar cap is made of carbon dioxide that sublimes at the same rate we see today, then it could increase the martian atmospheric pressure by as much as 10 times, to about 1/10th the density of Earth's atmosphere, in just the next few thousand years. Although this atmosphere would not be breathable, carbon dioxide is a "greenhouse gas" that would cause the global temperature to increase considerably and make it easier for liquid water to persist elsewhere on the planet. Perhaps, just perhaps, a thickening martian atmosphere would eventually make it easier for people to live on Mars.
Voir l'image PIA03179: MOC Observes Changes in the South Polar Cap: Evidence for Recent Climate Change on Mars sur le site de la NASA.
28 August 2005
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a frost-covered slope in the south polar region of Mars. The layered nature of the terrain in the south polar region is evident in a series of irregular, somewhat stair-stepped bands that run across the image.
Location near: 84.3°S, 27.2°W
Image width: width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
15 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layers exposed by erosion on a slope in the martian south polar region. Both polar caps on Mars are underlain by a complex stratigraphy of layered material; the Mars Polar Lander -- lost in December 1999 -- was designed to have provided some insight as to the nature and composition of the layers in the southern hemisphere.
Location near: 86.9°S, 180.5°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer
Tremendous floods carved these tear drop-shaped landforms in Athabasca Vallis in the Cerberus region, south of the Elysium volcanoes. The orientation of the streamlined forms indicate that the fluid flowed from the right/upper right toward the left/lower left (from the northeast to the southwest). Similar features occur in central and eastern Washington in the northwestern United States. The examples in Washington formed when massive amounts of water rushed across the landscape, scouring a "channeled scabland" during the last Ice Age, roughly 12,000-13,000 years ago. The features on Mars are much older; while the absolute age cannot be determined, the small impact craters with rayed ejecta patterns on the flood surfaces indicate it must be much, much older than the flood landscape in Washington. This is a mosaic of six Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images acquired in 1999 through 2002. Illumination is from the left. The mosaic covers an area 11.9 km (7.4 mi) by 13.0 km (8.1 mi). The full-size mosaic has a resolution of 4 meters (13 ft) per pixel.
Voir l'image PIA04051: Athabasca Vallis Streamlined "Islands" sur le site de la NASA.
16 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an impact crater, roughly the size of the famous Meteor Crater in northern Arizona, U.S.A., in western Elysium Planitia. Light-toned, windblown ripples of sediment have accumulated in subtle troughs and in the lee -- the downwind side -- of the crater.
Location near: 28.4°N, 247.9°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Winter
This chain of pits formed by collapse as faulting extended the upper crust in the Tractus Catena region of Mars. The layered bedrock can be seen in the upper walls of each pit in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image. The picture covers an area about 3 km (1.9 mi) wide near 28.5°N, 102.9°W. Sunlight illuminates the scene from the left.
Voir l'image PIA04568: Tractus Catena Collapse Pits sur le site de la NASA.
Polygons similar to those found in Earth's arctic and antarctic regions are also found in the polar regions of Mars. Typically, they occur on crater floors, or on intercrater plains, between about 60° and 80° latitude. The polygons are best seen when bright frost or dark sand has been trapped in the troughs that form the polygon boundaries. Three examples of martian polygons seen by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) are shown here. Each is located in the southern hemisphere:(left) Polygon troughs highlighted by frost as the south polar cap retreats during spring. The circular features are the locations of buried craters that were originally formed by meteor impact. This image, E09-00029, is located at 75.1°S, 331.3°W, and was acquired on 1 October 2001.(center) Summertime view of polygons, highlighted by dark, windblown sand, on the floor of a crater at 71.2°S, 282.6°W. The image, E12-02319, was obtained on 21January 2002.(right) Polygon troughs highlighted by the retreating south polar frost cap during southern summer near 80.7°S, 70.4°W. This picture, M11-01795, was taken by MOC on 13 January 2000.Some Mars researchers assume that polygons on the Red Planet are key indictors that ground ice is present or was present in the recent past. However, whether these polygons actually required water ice to form is, in fact, unknown, since dry processes are also known on Earth for form similar polygons.
Voir l'image PIA03496: Southern Hemisphere Polygonal Patterned Ground sur le site de la NASA.
2 January 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of a dark sand dune field in a crater in the Noachis Terra region. Martian dunes are darker than their typical terrestrial counterparts because they contain minerals with a higher abundance of iron and magnesium, and somewhat lower amounts of silica.
Location near: 45.4°S, 331.1°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Spring
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a typical southern mid-latitude surface at very high resolution. The smooth-surfaced material (mostly on the left and lower left sides of the image) erodes and breaks down into the knobby terrain (seen at the top and right). The exact cause of this degradation of smooth-surfaced material at middle latitudes is unknown. One speculation is that the materials are a mixture of water ice, dust, and silt; when the ice sublimes away, it leaves behind the knobby terrain. The image is located near 37.0°S, 84.0°W. Sunlight illuminates the scene from the upper left.
Voir l'image PIA04514: Martian "Ground Rot" sur le site de la NASA.
