The telescope's Wide Field and Planetary Camera 2 snapped images between April 27 and May 6, when Mars was 54 million miles (87 million kilometers) from Earth. From this distance the telescope could see Martian features as small as 12 miles (19 kilometers) wide. The telescope obtained four images (see PIA01587), which, together, show the entire planet.
This image is centered near a volcanic region known as Elysium. This area shows many small, dark markings that have been observed by the Hubble telescope and other spacecraft to change as a result of the movement of sand and dust across the Martian surface. In the upper left of this image, at high northern latitudes, a large chevron-shaped area of water ice clouds mark a storm front. Along the right limb, a large cloud system has formed around the Olympus Mons volcano.
This color composite is generated from data using three filters: blue (410 nanometers), green (502 nanometers), and red (673 nanometers).
Voir l'image PIA01591: A Closer Hubble Encounter With Mars - Elysium sur le site de la NASA.
[RIGHT] This NASA Hubble Space Telescope picture of Mars was taken on Sept. 12, one day after the arrival of the Mars Global Surveyor (MGS) spacecraft and only five hours before the beginning of autumn in the Martian northern hemisphere. (Mars is tilted on its axis like Earth, so it has similar seasonal changes, including an autumnal equinox when the Sun crosses Mars' equator from the northern to the southern hemisphere).
This Hubble picture was taken in support of the MGS mission. Hubble is monitoring the Martian weather conditions during the early phases of MGS aerobraking; in particular, the detection of large dust storms are important inputs into the atmospheric models used by the MGS mission to plan aerobraking operations.
Though a dusty haze fills the giant Hellas impact basin south of the dark fin-shaped feature Syrtis Major, the dust appears to be localized within Hellas. Unless the region covered expands significantly, the dust will not be of concern for MGS aerobraking.
Other early signs of seasonal transitions on Mars are apparent in the Hubble picture. The northern polar ice cap is blanketed under a polar hood of clouds that typically start forming in late northern summer. As fall progresses, sunlight will dwindle in the north polar region and the seasonal polar cap of frozen carbon dioxide will start condensing onto the surface under these clouds.
Hubble observations will continue until October 13, as MGS carefully uses the drag of the Martian atmosphere to circularize its orbit about the Red Planet. After mid-October, Mars will be too close to the Sun, in angular separation, for Hubble to safely view.
The image is a composite of three separately filtered colored images taken with the Wide Field Planetary Camera 2 (WFPC2). Resolution is 35 miles (57 kilometers) per pixel (picture element). The Pathfinder landing site near Ares Valles is about 2200 miles (3600 kilometers) west of the center of this image, so was not visible during this observation. Mars was 158 million miles (255 million kilometers) from Earth at the time.
[LEFT]
An image of this region of Mars, taken in June 1997, is shown for comparison. The Hellas basin is filled with bright clouds and/or surface frost. More water ice clouds are visible across the planet than in the Sept. image, reflecting the effects of the changing season. Mars appears larger because it was 44 million miles (77 million kilometers) closer to Earth than in the September image.
This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/.
Voir l'image PIA01243: Hubble Watches the Red Planet as Mars Global Surveyor Begins Aerobraking sur le site de la NASA.
NASA Hubble Space Telescope images of Mars, taken on June 27, 1997 (left) and July 9, 1997 (right), document the dissipation of a large dust storm during the 12 days separating the two observations.
The images were taken to monitor the weather conditions near Ares Vallis, the site where NASA's Pathfinder spacecraft landed on July 4. Maps of the equatorial region were constructed from the images and are shown at the bottom of the figure; a green cross marks the Pathfinder landing site. (All images are oriented with North to the top).
These two sets of observations show a number of dramatic changes in the planet's atmosphere. At about the 7 o'clock position on the June 27 image, the eastern end of the Valles Marineris canyon system is just coming into daylight and can be seen to be filled with yellowish dust. The dust appears to be confined to the canyons, which can be as much as 8 km deep and hundreds of km wide. Estimates of the quantity of dust involved in this storm indicate that 96% of the incoming sunlight is being blocked from reaching the surface by the dust clouds. Note that on the July 9 image, the dust storm appears to be subsiding; it is estimated that the dust quantity in most of the visible canyon system has dropped to only 10% to 20% of that seen on June 27.
However, on July 9 a streamer of dust is visible in the North polar region, extending about 1200 km southward from the dark sand dunes surrounding the polar ice cap; diffuse dust is visible over much of Acidalia, the dark region to the north of the Pathfinder landing site. The extent of clouds visible across the planet has also changed considerably between the two dates. Just to the west (left) of the July 9 dust streamer, a very bright area of water-ice clouds is seen; this area was considerably cloudier on June 27.
These images dramatically show that atmospheric conditions can change rapidly on Mars. Observations such as these will continue to be made over the next several months, allowing the detailed surface observations made by Pathfinder to be placed into the broader context of the global images available from HST.
This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/.
Voir l'image PIA01244: Decay of a Martian Dust Storm sur le site de la NASA.
NASA's Earth-orbiting Hubble Space Telescope took the picture on June 26, when Mars was approximately 43 million miles (68 million km) from Earth -- the closest Mars has ever been to Earth since 1988. Hubble can see details as small as 10 miles (16 km) across. The colors have been carefully balanced to give a realistic view of Mars' hues as they might appear through a telescope.
Especially striking is the large amount of seasonal dust storm activity seen in this image. One large storm system is churning high above the northern polar cap [top of image], and a smaller dust storm cloud can be seen nearby. Another large dust storm is spilling out of the giant Hellas impact basin in the Southern Hemisphere [lower right].
Hubble has observed Mars before, but never in such detail. The biennial close approaches of Mars and Earth are not all the same. Mars' orbit around the Sun is markedly elliptical; the close approaches to Earth can range from 35 million to 63 million miles.
Astronomers are interested in studying the changeable surface and weather conditions on Mars, in part, to help plan for a pair of NASA missions to land rovers on the planet's surface in 2004.
The Mars opposition of 2001 serves as a prelude for 2003 when Mars and Earth will come within 35 million miles of each other, the closest since 1924 and not to be matched until 2287.
Voir l'image PIA03154: Hubble Captures Best View of Mars Ever Obtained from Earth sur le site de la NASA.
These NASA Hubble Space Telescope views provide the most detailed complete global coverage of the red planet Mars ever seen from Earth. The pictures were taken on February 25, 1995, when Mars was at a distance of 65 million miles (103 million km).
To the surprise of researchers, Mars is cloudier than seen in previous years. This means the planet is cooler and drier, because water vapor in the atmosphere freezes out to form ice-crystal clouds. Hubble resolves Martian surface features with a level of detail only exceeded by planetary probes, such as impact craters and other features as small as 30 miles (50 kilometers) across.
[Tharsis region] - A crescent-shaped cloud just right of center identifies the immense shield volcano Olympus Mons, which is 340 miles (550 km) across at its base. Warm afternoon air pushed up over the summit forms ice-crystal clouds downwind from the volcano. Farther to the east (right) a line of clouds forms over a row of three extinct volcanoes which are from north to south: Ascraeus Mons, Pavonis Mons, Arsia Mons. It's part of an unusual, recurring "W"-shaped cloud formation that once mystified earlier ground-based observers.
[Valles Marineris region] - The 16 mile-high volcano Ascraeus Mons pokes through the cloud deck along the western (left) limb of the planet. Other interesting geologic features include (lower left) Valles Marineris, an immense rift valley the length of the continental United States. Near the image center lies the Chryse basin made up of cratered and chaotic terrain. The oval-looking Argyre impact basin (bottom) appears white due to clouds or frost.
[Syrtis Major region] - The dark "shark fin" feature left of center is Syrtis Major. Below it the giant impact basin Hellas. Clouds cover several great volcanos in the Elysium region near the eastern (right) limb. As clearly seen in the Hubble images, past dust storms in Mars' southern hemisphere have scoured the plains of fine light dust and transported the dust northward. This leaves behind a relatively coarser, and less reflective sand in, predominantly, the southern hemisphere.
The pictures were taken with Hubble's Wide Field Planetary Camera 2.
This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/.
Voir l'image PIA01252: Mars At Opposition sur le site de la NASA.
The telescope's Wide Field and Planetary Camera 2 snapped images between April 27 and May 6, when Mars was 54 million miles (87 million kilometers) from Earth. From this distance the telescope could see Martian features as small as 12 miles (19 kilometers) wide. The telescope obtained four images PIA01587), which, together, show the entire planet.
This image is centered near the location of the Pathfinder landing site. Dark sand dunes that surround the polar cap merge into a large, dark region called Acidalia. This area, as shown by images from the Hubble telescope and other spacecraft, is composed of dark, sand-sized grains of pulverized volcanic rock. Below and to the left of Acidalia are the massive Martian canyon systems of Valles Marineris, some of which form long linear markings that were once thought by some to be canals. Early morning clouds can be seen along the left limb of the planet, and a large cyclonic storm composed of water ice is churning near the polar cap.
This color composite is generated from data using three filters: blue (410 nanometers), green (502 nanometers), and red (673 nanometers).
Voir l'image PIA01589: A Closer Hubble Encounter With Mars - Pathfinder Landing Site sur le site de la NASA.
The telescope's Wide Field and Planetary Camera 2 snapped these images between April 27 and May 6, when Mars was 54 million miles (87 million kilometers) from Earth. From this distance the telescope could see Martian features as small as 12 miles (19 kilometers) wide.
The telescope obtained four images, which, together, show the entire planet. Each view depicts the planet as it completes one quarter of its daily rotation. In these views the north polar cap is tilted toward the Earth and is visible prominently at the top of each picture. The images were taken in the middle of the Martian northern summer, when the polar cap had shrunk to its smallest size. During this season the Sun shines continuously on the polar cap. Previous telescopic and spacecraft observations have shown that this summertime "residual" polar cap is composed of water ice, just like Earth's polar caps.
These Hubble telescope snapshots reveal that substantial changes in the bright and dark markings on Mars have occurred in the 20 years since the NASA Viking spacecraft missions first mapped the planet. The Martian surface is dynamic and ever changing. Some regions that were dark 20years ago are now bright red; some areas that were bright red are now dark. Winds move sand and dust from region to region, often in spectacular dust storms. Over long time scales many of the larger bright and dark markings remain stable, but smaller details come and go as they are covered and then uncovered by sand and dust.
The upper-left image is centered near the location of the Pathfinder landing site. Dark sand dunes that surround the polar cap merge into a large, dark region called Acidalia. This area, as shown by images from the Hubble telescope and other spacecraft, is composed of dark, sand-sized grains of pulverized volcanic rock. Below and to the left of Acidalia are the massive Martian canyon systems of Valles Marineris, some of which form long linear markings that were once thought by some to be canals. Early morning clouds can be seen along the left limb of the planet, and a large cyclonic storm composed of water ice is churning near the polar cap. See also PIA01589.
The upper-right image is centered on the region of the planet known as Tharsis, home of the largest volcanoes in the solar system. The bright, ring-like feature just to the left of center is the volcano Olympus Mons, which is more than 340 miles (550 kilometers) across and 17 miles(27 kilometers) high. Thick deposits of fine-grained, windblown dust cover most of this hemisphere. The colors indicate that the dust is heavily oxidized ("rusted"), and millions (or perhaps billions) of years of dust storms have homogenized its composition. Prominent late afternoon clouds along the right limb of the planet can be seen. See also PIA01590.
The lower-left image is centered near another volcanic region known as Elysium. This area shows many small, dark markings that have been observed by the Hubble telescope and other spacecraft to change as a result of the movement of sand and dust across the Martian surface. In the upper left of this image, at high northern latitudes, a large chevron-shaped area of water ice clouds mark a storm front. Along the right limb, a large cloud system has formed around the Olympus Mons volcano. See also PIA01591.
The lower-right image is centered on the dark feature known as Syrtis Major, first seen telescopically by the astronomer Christian Huygens in the 17th century. Many small, dark, circular impact craters can be seen in this region, attesting to the Hubble telescope's ability to reveal fine detail on the planet's surface. To the south of Syrtis a large circular feature called Hellas. Viking and more recently Mars Global Surveyor have revealed that Hellas is a large and deep impact crater. These Hubble telescope pictures show it to be filled with surface frost and water ice clouds. Along the right limb, late afternoon clouds have formed around the volcano Elysium. See also PIA01592.
Shown here are color composites generated from data using three filters: blue (410 nanometers), green (502 nanometers), and red (673 nanometers). A total of 12 color filters, spanning ultraviolet to near-infrared wavelengths, were used in the observation.
Voir l'image PIA01587: A Closer Hubble Encounter With Mars - 4 Views sur le site de la NASA.
Hubble Space Telescope images of Mars, taken on June 27, 1997, reveal a significant dust storm which fills much of the Valles Marineris canyon system and extends into Xanthe Terra, about 600 miles (1000 kilometers) south of the landing site.
It is difficult to predict the evolution of this storm and whether it will affect the Pathfinder observations.
The pictures were taken in order to monitor the site in Ares Vallis where the Pathfinder spacecraft will land on July 4.
The two images of Mars at the top of the figure are Hubble observations from June 27 (right) and May 17 (left). Visual comparison of these two images clearly shows the dust storm between 5 and 7 o'clock and about 2/3 of the way from the center of the planet's disk to the southern edge of the June image.
The digital data were projected to form the map of the equatorial portion of the planet which is shown in the bottom portion of the figure. The green cross marks the location of the Pathfinder landing site, and the yellowish ribbon of dust which runs horizontally across the bottom of the map traces the location of Valles Marineris, a system of canyons which would stretch from Los Angeles to New York if placed on Earth.
Most of the dust is confined within the canyons, which are up to 5-8 kilometers deep. The thickness of the dust cloud near the eastern end of the storm is similar to that observed by Viking lander 1 during the first of the two 1977 global dust storms which it studied.
Other interesting features appear in this image. The northwestern portions of the planet are enveloped in unusually thick water ice clouds, similar to cirrus clouds on Earth; some clouds extend as far as Lunae Planum, the slightly darker region about halfway from the center to the left side of the map. The dark spot near the terminator (boundary between day and night) at about 9:00 in the June 27 planet image is Ascraeus Mons, a 27 kilometer high volcano, protruding through the clouds.
The remnant north polar cap, composed of water ice, is at the top of the May and June images, and a bluish south polar hood, composed of water ice clouds, is seen along the southern edge. Because the planet's axis is tipped towards us during this season, we cannot see the south polar cap, which is in winter darkness.
This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/.
Voir l'image PIA01245: Hubble's Look at Mars Shows Canyon Dust Storm, Cloudy Conditions for Pathfinder Landing sur le site de la NASA.
The telescope's Wide Field and Planetary Camera 2 snapped images between April 27 and May 6, when Mars was 54 million miles (87 million kilometers) from Earth. From this distance the telescope could see Martian features as small as 12 miles (19 kilometers) wide. The telescope obtained four images(see PIA01587), which, together, show the entire planet.
This image is centered on the region of the planet known as Tharsis, home of the largest volcanoes in the solar system. The bright, ring-like feature just to the left of center is the volcano Olympus Mons, which is more than 340 miles (550 kilometers) across and 17 miles(27 kilometers) high. Thick deposits of fine-grained, windblown dust cover most of this hemisphere. The colors indicate that the dust is heavily oxidized ("rusted"), and millions (or perhaps billions) of years of dust storms have homogenized its composition. Prominent late afternoon clouds along the right limb of the planet can be seen.
This color composite is generated from data using three filters: blue (410 nanometers), green (502 nanometers), and red (673 nanometers).
Voir l'image PIA01590: A Closer Hubble Encounter With Mars - Tharsis sur le site de la NASA.
This NASA Hubble Space Telescope view of the planet Mars was, at the time it was taken, the clearest picture ever taken from Earth, surpassed only by close-up shots sent back by visiting space probes. The picture was taken on February 25, 1995, when Mars was at a distance of approximately 65 million miles (103 million km) from Earth.
Because it is spring in Mars' northern hemisphere, much of the carbon dioxide frost around the permanent water-ice cap has sublimated, and the cap has receded to a core of solid water-ice several hundred miles across.
Towering 16 miles (25 km) above the surrounding plains, volcano Ascraeus Mons pokes above the cloud deck near the western or limb. This extinct volcano, measuring 250 miles (402 km) across, was discovered in the early 1970s by Mariner 9 spacecraft. Other key geologic features include (lower left) the Valles Marineris, an immense rift valley the length of the continental United States. Near the center of the disk lies the Chryse basin made up of cratered and chaotic terrain. The oval-looking Argyre impact basin (bottom), appears white due to clouds or frost.
Seasonal winds carry dust to form striking linear features reminiscent of the legendary martian "canals." Many of these "wind streaks" emanate from the bowl of these craters where dark coarse sand is swept out by winds. Hubble resolves several dozen impact craters down to 30-mile diameter. The dark areas, once misinterpreted as regions of vegetation by several early Mars watchers, are really areas of coarse sand that is less reflective than the finer, lighter dust. Seasonal changes in the surface appearance occur as winds move the dust and sand around.
This picture was taken with Hubble's Wide Field Planetary Camera 2 in PC mode. The pictures were map-projected onto a sphere for accurate registration and perspective.
This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/.
Voir l'image PIA01253: Springtime on Mars: Hubble's Best View of the Red Planet sur le site de la NASA.
Pictures of the planet Mars taken with the recently refurbished NASA Hubble Space Telescope (HST) will provide the most detailed global view of the red planet ever obtained from Earth.
The images were taken by HST's Wide Field Planetary Camera-2 on March 10, 1997, just before Mars opposition, when the red planet made one of its closest to the Earth (about 60 million miles or 100 million km).
These pictures were taken during three HST orbits that were separated by about six hours. This timing was chosen so that Mars, with its 24-hour 39- minute day, would rotate about 90 degrees between orbits. This imaging sequence therefore covers most of the Martian surface. These observations will be combined with others planned for March 30 to provide complete coverage.
During each orbit, Mars was observed in nine different colors spanning the ultraviolet to the near infrared. The specific colors were chosen to clearly discriminate between airborne dust, ice clouds, and prominent Martian surface features. The color picture shown here was created by combining images taken in blue (433 nm), green (554 nm), and red (763 nm) colored filters. The Martian north pole is at the top (near the center of the bright polar cap) and East is to the right. The center of the disk is at about 23 degrees north latitude, and the central longitudes are near 160, 210, and 305 degrees.
These images show the planet on the last day of Martian spring in the northern hemisphere (just before summer solstice). The annual north polar carbon dioxide frost (dry ice) cap is rapidly sublimating, revealing the much smaller permanent water ice cap. This polar cap remnant, along with a few nearby detached regions of surface frost are most obvious in pictures taken through ultraviolet, blue, and green filters. These filters also show numerous bright water ice clouds. The brightest clouds are in the vicinity of the giant volcanos on the Tharsis Plateau (to right of center on left image), and in the giant impact basin, Hellas (near bottom of right-hand image), but a diffuse haze covers much of the Martian tropics as well.
The familiar bright and dark markings on the Martian surface are most obvious in images taken through red and near-infrared filters. These images clearly reveal the large, dark, circular "sea" of sand dunes (Olympia Planitia) that surrounds the north pole, as well a number of other familiar features, including the giant Tharsis volcanos. The 16-mile (27 km) high Olympus Mons is near the center of the left-hand image, with Arsia, Povonis, and Ascraeus Mons forming a south-west to north-east line just to its right. The volcano, Elysium Mons is near the center of the middle image. The prominent dark feature just below the center on the disk on the rightmost image is Syrtis Major Planitia.
Hubble is being used to monitor dust storm activity to support the Mars Pathfinder and Mars Global Surveyor Orbiter Missions, which are currently en route to Mars. Airborne dust is most easily seen in WFPC2's red and near-infrared images. Weather reports derived from these observations are particularly valuable for Mars Pathfinder, which is scheduled for a July 4, 1997 landing on the red planet. A preliminary analysis of these HST data reveals enhanced dust activity over the dark Vastitas Borealis region in the northern hemisphere, and over the Noachis Terra and Terra Tyrrhena regions just south of the Martian equator. There is also evidence for airborne dust and ice clouds in the Hellas basin. However, these images show no evidence for large-scale dust storm activity.
This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/.
Voir l'image PIA01250: Hubble Captures A Full Rotation Of Mars sur le site de la NASA.
Four faces of Mars as seen on March 30, 1997 are presented in this montage of NASA Hubble Space Telescope images. Proceeding in the order upper-left, upper-right, lower-left, lower-right, Mars has rotated about ninety degrees between each successive time step. For example the Tharsis volcanoes, which are seen (between 7:30 and 9 o'clock positions) in mid-morning in the UPPER-RIGHT view, are seen near the late afternoon edge of the planet (about 3 o'clock position) in the lower-left image. All of these color images are composed of individual red (673 nanometers), green (502 nm), and blue (410 nm) Planetary Camera exposures.
Upper left: This view is centered on Ares Valles, where Pathfinder will land on July 4, 1997; the Valles Marineris canyon system stretches to the west across the lower left portion of the planet, while the bright, orangish desert of Arabia Planitia is to the east. The bright polar water-ice cap, surrounded by a dark ring of sand dunes, is obvious in the north; since it is northern summer and the pole is tilted toward us, the residual north polar cap is seen in its entirety in all four images. Acidalia Planitia, the prominent dark area fanning southward from the polar region, is thought to have a surface covered with dark sand. Numerous "dark wind streaks" are visible to the south of Acidalia, resulting from wind-blown sand streaming out of the interiors of craters.
Upper right: The Tharsis volcanos and associated clouds are prominent in the western half of this view. Olympus Mons, spanning 340 miles (550 km) across its base and reaching an elevation of 16 miles (25 km), extends through the cloud deck near the western limb, while (from the south) Arsia Mons, Pavonis Mons, and Ascraeus Mons are to the west of center. Valles Marineris stretches to the east, and the Pathfinder landing site is shrouded in clouds near the afternoon limb.
Lower left: This relatively featureless sector of Mars stretches from the Elysium volcanic region in the west to the Tharsis volcanoes (shrouded by the bright clouds near the afternoon limb) in the east. The group of three dark specks just left of center are all that remain of Cerberus, a very prominent dark region during the Viking and Mariner 9 missions. This is an example of the remarkable large scale changes which can occur on Mars due to windblown dust: the former dark area has now been covered by a layer of bright dust, masking the underlying material.
Lower right: The dark Syrtis Major region dominates this image. Syrtis Major is one of the most prominent dark features on Mars, and has been visible since ground-based observers first peered at Mars through telescopes. The bright cloud at 3 o'clock is associated with Elysium Mons. The bright bluish-white feature near the southern limb of the planet is Hellas, a 1,200 mile (2,000 km) diameter impact basin formed by the collision of a large body with Mars long ago. Hellas is covered with dry ice frost and clouds during this season (winter in the south).
This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/.
Voir l'image PIA01248: Four Views of Mars in Northern Summer sur le site de la NASA.
[upper right]: This is a color polar view of the north polar region, showing the location of the storm relative to the classical bright and dark features in this area. The color composite data (410, 502, and 673 nm) indicate that the storm is fairly dust-free and therefore likely composed mostly of water ice clouds. The bright surface region beneath the eye of the storm can be seen clearly. This map covers the region north of 45 degrees latitude and is oriented with 0 degrees longitude at the bottom.
[lower right]: This is an enhanced orthographic view of the storm centered on 65 deg. N latitude, 85 deg. W longitude. The image has been processed to bring out additional detail in the storm's spiral cloud structures.
The pictures were taken on April 27, 1999 with the NASA Hubble Space Telescope's Wide Field and Planetary Camera 2
Voir l'image PIA01545: Hubble Views Colossal Polar Cyclone on Mars sur le site de la NASA.
Two Hubble Space Telescope images of Mars, taken about a month apart on September 18 and October 15, 1996, reveal a state-sized dust storm churning near the edge of the Martian north polar cap. The polar storm is probably a consequence of large temperature differences between the polar ice and the dark regions to the south, which are heated by the springtime sun. The increased sunlight also causes the dry ice in the polar cap to sublime and shrink.
Mars is famous for large, planet-wide dust storms. Smaller storms resembling the one seen here were observed in other regions by Viking orbiters in the late 1970s. However, this is the first time that such an event has been caught near the receding north polar cap. The Hubble images provide valuable new insights into the behavior of localized dust storms on Mars, which are typically below the resolution of ground-based telescopes. This kind of advanced planetary "weather report" will be invaluable for aiding preparation for the landing of NASA's Pathfinder spacecraft in July 1997 and the arrival of Mars Global Surveyor orbiter in September 1997.
Top (September 18, 1996) - The salmon colored notch in the white north polar cap is a 600-mile (1,000 kilometer) long storm -- nearly the width of Texas. The bright dust can also be seen over the dark surface surrounding the cap, where it is caught up in the Martian jet stream and blown easterly. The white clouds at lower latitudes are mostly associated with major Martian volcanos such as Olympus Mons. This image was taken when Mars was more than 186 million miles (300 million kilometers) from Earth, and the planet was smaller in angular size than Jupiter's Great Red Spot!
Bottom (October 15, 1996) - Though the storm has dissipated by October, a distinctive dust-colored comma-shaped feature can be seen curving across the ice cap. The shape is similar to cold fronts on Earth, which are associated with low pressure systems. Nothing quite like this feature has been seen previously either in ground-based or spacecraft observation. The snow line marking the edge of the cap receded northward by approximately 120 miles (200 kilometers), while the distance to the Red Planet narrowed to 170 million miles (275 million kilometers).
Technical notes: To help compare locations and sizes of features, map projections (right of each disk) are centered on the geographic north pole. Maps are oriented with 0 degrees longitude at the top and show meridians every 45 degrees of longitude (longitude increases clockwise); latitude circles are also shown for 40, 60, and 80 degrees north latitude. The color images were assembled from separate exposures taken with the Wide Field Planetary Camera 2.
This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/.
Voir l'image PIA01251: Springtime Dust Storm Swirls at Martian North Pole sur le site de la NASA.
LEFT
This "true-color" image of Mars shows the planet as it would look to human eyes. It is clearly more Earth-toned than usually depicted in other astronomical images, including earlier Hubble pictures. The slightly bluer shade along the edges of the disk is due to atmospheric hazes and wispy water ice clouds (like cirrus clouds) in the early morning and late evening Martian sky. The yellowish-pink color of the northern polar cap indicates the presence of small iron-bearing dust particles. These particles are covering or are suspended in the air above the blue-white water ice and carbon dioxide ice, which make up the polar cap.
Accurate colors are needed to determine the composition and mineralogy of Mars. This can tell how water has influenced the formation of rocks and minerals found on Mars today, as well as the distribution and abundance of ice and subsurface liquid water. Confirmation of the presence of certain oxidized (rusted) minerals (processed by heat or water action) would imply the possibility of different, perhaps much more Earth-like, past Martian climate periods. Because the smallest features visible in this image are only about 14 miles (22 km) across, Hubble can track small-scale variations in the distribution of minerals that do not follow global trends. The image was generated from three separate Wide Field and Planetary Camera 2 images acquired at wavelengths of 410, 502, and 673 nanometers, in March 1997.
RIGHT
A false-color picture taken in infrared light reveals features that cannot be seen in visible light. Hubble's unique infrared view pinpoints variations in the abundance and distribution of unknown water-bearing minerals on the planet. While it has been known for decades that small amounts of water-bearing minerals exist on the planet's surface, the reddish regions in this image indicate areas of enhanced concentrations of these as-yet-unidentified deposits. They are perhaps related to the water-rich history of this part of Mars. In particular, the large reddish region known as Mare Acidalium was the site of massive flooding early in Martian history. (NASA's Pathfinder spacecraft landed at the southern edge of this region in 1997.) This composite image was taken in July 1997 with Hubble's Near Infrared Camera and Multi-Object Spectrometer. Red corresponds to the strength of an absorption band detected near 1450 nanometers; green to the brightness of the surface in the near-infrared; and blue to topographic elevation, determined from Viking Orbiter data.
Voir l'image PIA01543: Martian Colors Provide Clues About Martian Water sur le site de la NASA.
The telescope's Wide Field and Planetary Camera 2 snapped images between April 27 and May 6, when Mars was 54 million miles (87 million kilometers) from Earth. From this distance the telescope could see Martian features as small as 12 miles (19 kilometers) wide. The telescope obtained four images (see PIA01587), which, together, show the entire planet.
This image is centered on the dark feature known as Syrtis Major, first seen telescopically by the astronomer Christian Huygens in the 17th century. Many small, dark, circular impact craters can be seen in this region, attesting to the Hubble telescope's ability to reveal fine detail on the planet's surface. To the south of Syrtis a large circular feature called Hellas. Viking and more recently Mars Global Surveyor have revealed that Hellas is a large and deep impact crater. These Hubble telescope pictures show it to be filled with surface frost and water ice clouds. Along the right limb, late afternoon clouds have formed around the volcano Elysium.
This color composite is generated from data using three filters: blue (410 nanometers), green (502 nanometers), and red (673 nanometers).
Voir l'image PIA01592: A Closer Hubble Encounter With Mars - Syrtis Major sur le site de la NASA.
The sharpest view of Mars ever taken from Earth was obtained by the recently refurbished NASA Hubble Space Telescope (HST). This stunning portrait was taken with the HST Wide Field Planetary Camera-2 (WFPC2) on March 10, 1997, just before Mars opposition, when the red planet made one of its closest passes to the Earth (about 60 million miles or 100 million km).
At this distance, a single picture element (pixel) in WFPC2's Planetary Camera spans 13 miles (22 km) on the Martian surface.
The Martian north pole is at the top (near the center of the bright polar cap) and East is to the right. The center of the disk is at about 23 degrees north latitude, and the central longitude is near 305 degrees.
This view of Mars was taken on the last day of Martian spring in the northern hemisphere (just before summer solstice). It clearly shows familiar bright and dark markings known to astronomers for more than a century. The annual north polar carbon dioxide frost (dry ice) cap is rapidly sublimating (evaporating from solid to gas), revealing the much smaller permanent water ice cap, along with a few nearby detached regions of surface frost. The receding polar cap also reveals the dark, circular sea of sand dunes that surrounds the north pole (Olympia Planitia).
Other prominent features in this hemisphere include Syrtis Major Planitia, the large dark feature seen just below the center of the disk. The giant impact basin Hellas (near the bottom of the disk) is shrouded in bright water ice clouds. Water ice clouds also cover several great volcanos in the Elysium region near the eastern edge of the planet (right). A diffuse water ice haze covers much of the Martian equatorial region as well.
The WFPC2 was used to monitor dust storm activity to support the Mars Pathfinder and Mars Global Surveyor Orbiter Missions, which are currently en route to Mars. Airborne dust is most easily seen in WFPC2's red and near-infrared images. Hubble's "weather report" from these images in invaluable for Mars Pathfinder, which is scheduled for a July 4 landing. Fortunately, these images show no evidence for large-scale dust storm activity, which plagued a previous Mars mission in the early 1970s.
The WFPC2 was used to observe Mars in nine different colors spanning the ultraviolet to the near infrared. The specific colors were chosen to clearly discriminate between airborne dust, ice clouds, and prominent Martian surface features. This picture was created by combining images taken in blue (433 nm), green (554 nm), and red (763 nm) colored filters.
This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/.
Voir l'image PIA01249: Hubble's Sharpest View Of Mars sur le site de la NASA.
When Hubble photographed Mars in early September, the storm had already been raging across the planet for nearly two months obscuring all surface features. The fine airborne dust blocks a significant amount of sunlight from reaching the Martian surface. Because the airborne dust is absorbing this sunlight, it heats the upper atmosphere. Seasonal global Mars dust storms have been observed from telescopes for over a century, but this is the biggest storm ever seen in the past several decades.
Mars looks gibbous in the right photograph because it is 26 million miles farther from Earth than in the left photo (though the pictures have been scaled to the same angular size), and our viewing angle has changed. The left picture was taken when Mars was near its closest approach to Earth for 2001 (an event called opposition); at that point the disk of Mars was fully illuminated as seen from Earth because Mars was exactly opposite the Sun.
Both images are in natural color, taken with Hubble's Wide Field Planetary Camera 2.
Voir l'image PIA03173: Scientists Track "Perfect Storm" on Mars sur le site de la NASA.
These images, which seem to have been taken while NASA's Hubble Space Telescope (HST) was looking directly down on the Martian North Pole, were actually created by assembling mosaics of three sets of images taken by HST in October, 1996 and in January and March, 1997 and projecting them to appear as they would if seen from above the pole. This first mosaic is a view which could not actually be seen in nature because at this season a portion of the pole would have actually been in shadow; the last view, taken near the summer solstice, would correspond to the Midnight Sun on Earth with the pole fully illuminated all day. The resulting polar maps begin at 50 degrees N latitude and are oriented with 0 degrees longitude at the 12 o'clock position. This series of pictures captures the seasonal retreat of Mars' north polar cap.
October 1996 (early spring in the Northern hemisphere): In this map, assembled from images obtained between Oct. 8 and 15, the cap extends down to 60 degrees N latitude, nearly it's maximum winter extent. (The notches are areas where Hubble data were not available). A thin, comma-shaped cloud of dust can be seen as a salmon-colored crescent at the 7 o'clock position. The cap is actually fairly circular about the geographic pole at this season; the bluish "knobs" where the cap seems to extend further are actually clouds that occurred near the edges of the three separate sets of images used to make the mosaic.
January 1997 (mid-spring): Increased warming as spring progresses in the northern hemisphere has sublimated the carbon dioxide ice and frost below 70 degrees north latitude. The faint darker circle inside the cap boundary marks the location of circumpolar sand dunes (see March '97 map); these dark dunes are warmed more by solar heating than are the brighter surroundings, so the surface frost sublimates from the dunes earlier than from the neighboring areas. Particularly evident is the marked hexagonal shape of the polar cap at this season, noted previously by HST in 1995 and Mariner 9 in 1972; this may be due to topography, which isn't well known, or to wave structure in the circulation. This map was assembled from WFPC2 images obtained between Dec. 30, 1996 and Jan. 4, 1997.
March 30, 1997 (early summer): The cap has fully retreated to its remnant core of water-ice. This residual cap is actually almost cut into two by a large, horn-shaped canyon called Chasma Borealis which is cut deeply into the polar terrain. The HST images also reveal a curious layered terrain which is evidence of past climatic changes on Mars. The sublimation of all of the carbon dioxide has exposed the ring of dark sand dunes which encircle the North Polar Cap. Outliers of ice persist south of the polar sand sea (between the 3 o'clock and 9 o'clock positions). The bright circular features at 3, 6, and 9 o'clock are ice-filled craters.
All images were taken with the Wide Field and Planetary Camera 2. The color is constructed from images taken in red (673 nm) , blue (410 nm) and green (502 nm) light. The resolution at the North Pole ranges from about 115 km/pixel in October '96 to about 45 km/pixel in March '97.
This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/.
Voir l'image PIA01247: Seasonal Changes in Mars' North Polar Ice Cap sur le site de la NASA.