Reull Valles, conspicuous southeast-trending fretted channel, dissects wall deposits of the large Hellas impact basin. Center of picture is at latitude 42 degrees S. longitude 258 degrees. Fretted channels are wide, flat-floored channels with steep walls, which may be runoff channels that have been modified and enlarged by mass wasting. Many nearby hills and mountains are surrounded by lobate debris aprons, which may have formed by slow creep of rock deposits aided by the presence of near-surface ice. Layering is exposed in the channel and crater walls. The color variations of the surface are very bland in this region; most of the variations seen in the enhanced-color version (PIA00153) are due to atmospheric scattering. Viking Orbiter Picture Numbers 126A08 (violet), 126A16 (green), and 126A24 (red) at 157 m/pixel resolution. Picture width is 161 km. North is 112 degrees clockwise from top.

Voir l'image PIA00322: Reull Valles in Approximately Natural Color sur le site de la NASA.

PIA00388: The United States Flag Stands On The Surface Of Mars

The flag of the United States stands on the surface of Mars. It is mounted on the housing of Viking 1's nuclear power system. Also seen are the U.S. Bicentennial symbol and a student designed Viking emblem. The bright flat surface near the center is the seismometer container. This picture was taken on July 23 at about 2:30 p.m. Mars time. The view is west of the spacecraft and includes a series of low hills. The blocky hill in the center appears to be part of a crater rim. The dark, rocky stripes may be material ejected from the crater. The light areas are dune-like and may be accumulations of windblown sand or dust.

Voir l'image PIA00388: The United States Flag Stands On The Surface Of Mars sur le site de la NASA.

PIA02985: Dust storm in the Thaumasia region of Mars

PIA00164: MC-4 Mare Acidalium Region

Mars digital-image mosaic merged with color of the MC-4 quadrangle, Mare Acidalium region of Mars. The central part is characterized by dark depression--the northern Chryse basin, which contains relatively smooth plains where several large outflow channels terminate. The depression is partly bounded to the southwest by the highly faulted and heavily cratered Tempe Terra province, to the southeast by the heavily cratered Arabia Terra province, and to the north by relatively smooth plains of Vastitas Borealis. Latitude range 30 to 65 degrees, longitude range 0 to 60 degrees.

Voir l'image PIA00164: MC-4 Mare Acidalium Region sur le site de la NASA.

PIA00091: Cerberus Hemisphere

This mosaic is composed of 104 Viking Orbiter images acquired on February 11, 1980. At that time, it was early northern summer on Mars (Ls = 65 degrees). The center of the image is at latitude 3 degrees, longitude 185 degrees, and the latitude limits are approximately 60 degrees N. and S. This image is in an orthographic projection with a scale of 1 km/pixel. The color variations have been enhanced by a factor of 2, and the large-scale brightness variations (mostly due to sun-angle variations) have been normalized by large-scale filtering. A major geologic boundary extends across this mosaic, with the lower third of the image showing ancient cratered highlands; north of this boundary are the lowland northern plains. A series of poorly-indurated sedimentary deposits occur just north of the highland-lowland boundary; some workers believe that these are explosive volcanic deposits (ignimbrites) whereas others have postulated that they are paleo-polar deposits. Other prominent features in this image include the large dark area left of the image center (named Cerberus), and the Elysium volcanic region (bright yellowish area north of Cerberus). The crater 'Mie' is located near the top left, and has a dark spot near its center. The Viking 2 Lander is located about 400 km west of the center of this crater, or about 1 1/2 crater diameter left of the left edge of the crater. Thin white clouds are dispersed over the northern hemisphere, and the opaque cloud in the upper right overlies the Olympus Mons Aureole. The arcuate markings west of the Aureole are thought to be extended drifts of windblown material. The bright blue area at the bottom of the picture shows the extent of the seasonal carbon dioxide polar cap (these frosts are actually white).

Voir l'image PIA00091: Cerberus Hemisphere sur le site de la NASA.

PIA00386: Example of Weathering And Sun Angle

PIA00421: Tyrrhena Patera

A color image of the Tyrrhena Patera Region of Mars; north toward top. The scene shows a central circular depression surrounded by circular fractures and highly dissected horizontal sheets. A patera (Latin for shallow dish or saucer) is a volcano of broad areal extent with little vertical relief.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 17 degrees S. to 25 degrees S. and from longitude 250 degrees to 260 degrees; Mercator projection.

Tyrrhena Patera has a 12-km-diameter caldera at its center surrounded by a 45-km-diameter fracture ring. Around the fracture ring, the terrain is highly eroded forming ragged outward-facing cliffs, as though successive flat-lying layers had been eroded back. Cut into the sequence are several flat-floored channels that extend outward as far as 200 km from the center of the volcano. The structure may be composed of highly erodible ash layers and the channels may be fluvial, with the release of water being triggered by volcanic activity (Carr, 1981, The surface of Mars, Yale Univ. Press, New Haven, 232 p.).

Voir l'image PIA00421: Tyrrhena Patera sur le site de la NASA.

PIA00426: Valles Marineris and Chryse Outflow Channels

A color image of Valles Marineris, the great canyon and the south Chryse basin-Valles Marineris outflow channels of Mars; north toward top. The scene shows the entire Valles Marineris canyon system, over 3,000 km long and averaging 8 km deep, extending from Noctis Labyrinthus, the arcuate system of graben to the west, to the chaotic terrain to the east and related outflow canyons that drain toward the Chryse basin. Eos and Capri Chasmata (south to north) are two canyons connected to Valles Marineris. Ganges Chasma lies directly north. The chaos in the southeast part of the image gives rise to several outflow channels, Shalbatana, Simud, Tiu, and Ares Valles (left to right), that drained north into the Chryse basin. The mouth of Ares Valles is the site of the Mars Pathfinder lander.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color; Mercator projection. The image roughly extends from latitude 20 degrees S. to 20 degrees N. and from longitude 15 degrees to 102.5 degrees.

The connected chasma or valleys of Valles Marineris may have formed from a combination of erosional collapse and structural activity. Layers of material in the eastern canyons might consist of carbonates deposited in ancient lakes, eolian deposits, or volcanic materials. Huge ancient river channels began from Valles Marineris and from adjacent canyons and ran north. Many of the channels flowed north into Chryse Basin.

The south Chryse outflow channels are cut an average of 1 km into the cratered highland terrain. This terrain is about 9 km above datum near Valles Marineris and steadily decreases in elevation to 1 km below datum in the Chryse basin. Shalbatana is relatively narrow (10 km wide) but can reach 3 km in depth. The channel begins at a 2- to 3-km-deep circular depression within a large impact crater, whose floor is partly covered by chaotic material, and ends in Simud Valles. Tiu and Simud Valles consist of a complex of connected channel floors and chaotic terrain and extend as far south as and connect to eastern Valles Marineris. Ares Vallis originates from discontinuous patches of chaotic terrain within large craters. In the Chryse basin the Ares channel forks; one branch continues northwest into central Chryse Planitia and the other extends north into eastern Chryse Planitia.

Voir l'image PIA00426: Valles Marineris and Chryse Outflow Channels sur le site de la NASA.

PIA00381: First Photograph Taken On Mars Surface

This is the first photograph ever taken on the surface of the planet Mars. It was obtained by Viking 1 just minutes after the spacecraft landed successfully early today [July 20, 1976]. The center of the image is about 1.4 meters (five feet) from Viking Lander camera #2. We see both rocks and finely granulated material--sand or dust. Many of the small foreground rocks are flat with angular facets. Several larger rocks exhibit irregular surfaces with pits and the large rock at top left shows intersecting linear cracks. Extending from that rock toward the camera is a vertical linear dark band which may be due to a one-minute partial obscuration of the landscape due to clouds or dust intervening between the sun and the surface. Associated with several of the rocks are apparent signs of wind transport of granular material. The large rock in the center is about 10 centimeters (4 inches) across and shows three rough facets. To its lower right is a rock near a smooth portion of the Martian surface probably composed of very fine-grained material. It is possible that the rock was moved during Viking 1 descent maneuvers, revealing the finer-grained basement substratum; or that the fine-grained material has accumulated adjacent to the rock. There are a number of other furrows and depressions and places with fine-grained material elsewhere in the picture. At right is a portion of footpad #2. Small quantities of fine grained sand and dust are seen at the center of the footpad near the strut and were deposited at landing. The shadow to the left of the footpad clearly exhibits detail, due to scattering of light either from the Martian atmosphere or from the spacecraft, observable because the Martian sky scatters light into shadowed areas.

Voir l'image PIA00381: First Photograph Taken On Mars Surface sur le site de la NASA.

PIA02982: Color Mosaic of Olympus Mons

PIA00163: MC-3 Arcadia Region

PIA00413: Fine Channel Networks

A color image of fine channel networks on Mars; north toward top. The scene shows heavily cratered highlands dissected by dendritic open channel networks that dissect steep slopes of impact crater walls.

This image is a composite of Viking high-resolution images in black and white and low-resolution images in color. The image extends from latitude 9 degrees S. to 5 degrees S. and from longitude 312 degrees to 320 degrees; Mercator projection.

The dendritic pattern of the fine channels and their location on steep slopes leads to the interpretation that these are runoff channels. The restriction of these types of channels to ancient highland rocks suggests that these channels are old and date from a time on Mars when conditions existed for precipitation to actively erode rocks. After the channels reach a low plain, they appear to end. Termination may have resulted from burial by younger deposits or perhaps the flows percolated into the surface materials and continued underground.

Voir l'image PIA00413: Fine Channel Networks sur le site de la NASA.

PIA00187: MC-27 Noachis Region

Mars digital-image mosaic merged with color of the MC-27 quadrangle, Noachis region of Mars. Heavily cratered highlands dominate the Noachis quadrangle. The northeastern part is marked by the western half of the ancient large Hellas basin, defined by a rim of rugged mountain blocks that surrounds a nearly circular expanse of light-colored plains. The southeastern part is marked by the Peneus caldera and part of the Amphitrites shield volcano and associated ridged plains that may be basaltic flows. Latitude range -65 to -30 degrees, longitude range -60 to 0 degrees.

Voir l'image PIA00187: MC-27 Noachis Region sur le site de la NASA.

PIA00156: Melas Chasm (Enhanced Color)

This picture (centered at latitude 10 degrees S., longitude 74 degrees W.) shows much of Melas Chasm and a portion of Candor Chasm (upper right) in central Valles Marineris. Several interesting compositional units can be seen in the image: white materials (center-right) may consist of carbonates or some other evaporite deposit, pinkish materials (upper right) may be relatively rich in crystalline iron oxides, and greenish materials (lower left) correspond to dark sand dunes. Viking Orbiter Picture Numbers 279B41 (violet), 279B49 (green), and 279B51 (red) at 257 m/pixel resolution. Picture width is 261 km. North is 50 degrees clockwise from top.

Voir l'image PIA00156: Melas Chasm (Enhanced Color) sur le site de la NASA.

PIA00009: North Polar Ice Cap

North polar ice cap of Mars, as seen during mid summer in the northern hemisphere. The reddish areas consist of eolian dust, bright white areas consist of a mixture of water ice and dust, and the dark blue areas consist of sand dunes forming a huge 'collar' around the polar ice cap. (The colors have been enhanced with a decorrelation stretch to better show the color variability.) Shown here is an oblique view of the polar region, as seen with the Viking 1 spacecraft orbiting Mars over latitude 39 degrees north. The spiral bands consist of valleys which form by a combination of the Coriolis forces, wind erosion, and differential sublimation and condensation. In high-resolution images the polar caps are seen to consist of thick sequences of layered deposits, suggesting that cyclical climate changes have occurred on Mars. Cyclical climate changes are readily explained by quasi-periodic changes in the amount and distribution of solar heating resulting from perturbations in orbital and axial elements. Variations in the Earth's orbit have also been linked to the terrestrial climate changes during the ice ages.

Voir l'image PIA00009: North Polar Ice Cap sur le site de la NASA.

PIA00180: MC-20 Sinus Sabeus Region

PIA00151: Memnonia Fossae (Enhanced Color)

Tharsis-centered volcanic and tectonic activity resulted in the formation of radial grabens of Memnonia Fossae, which cut materials of the ancient cratered highlands and the relatively young, highland-embaying lava flows from the Tharsis volcanoes. Center of picture is at latitude 16 degrees S., longitude 142 degrees W. The enhanced color version (following decorrelation stretch) reveals a diversity of subtle color variations; many of the color variations may be due to different lava flow units and variable amounts of weathering, possible alteration by water, and eolian redistributions. Viking Orbiter Picture Numbers 41B52 (green) 41B54 (red), and 41B56 (blue) at 198 m/pixel resolution. Picture width is 206 km. North is 119 degrees counter-clockwise from top.

Voir l'image PIA00151: Memnonia Fossae (Enhanced Color) sur le site de la NASA.

PIA00414: Ma'adim Vallis

Color image of Ma'adim Vallis region of Mars; north toward top. Image shows the 600-km-long channel that drained into impact crater Gusev. Crater Gusev is about 160 km in diameter. This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 13 degrees S. to 29 degrees S. and from longitude 180 degrees to 188 degrees; Mercator projection. Ma'adim Vallis is cut into the degraded highlands of Mars and has morphologic characteristics of terrestrial river beds, including the well-developed dentritic tributaries that constitute an integrated river system. However, the junction angles between tributaries commonly show a wide variation, which gives the channel system a more random directional pattern than typical terrestrial drainage networks. Topographic contours suggest a large drainage basin once existed for this channel. Gradients for the channel are high, about 0.007, over the central 300 km of its length; this is about two times that of the upper 450 km of the Colorado River. In places, some tributaries are discontinuous, perhaps indicating burial by more recent material. After the channel breaches Gusev it appears to end within the crater. Termination may have resulted from burial by younger deposits or perhaps the flow percolated into the surface materials and continued underground.

Voir l'image PIA00414: Ma'adim Vallis sur le site de la NASA.

PIA01522: Viking 2 Image of Mars Utopian Plain

The boulder-strewn field of red rocks reaches to the horizon nearly two miles from Viking 2 on Mars' Utopian Plain. Scientists believe the colors of the Martian surface and sky in this photo represent their true colors. Fine particles of red dust have settled on spacecraft surfaces. The salmon color of the sky is caused by dust particles suspended in the atmosphere. Color calibration charts for the cameras are mounted at three locations on the spacecraft. Note the blue star field and red stripes of the flag. The circular structure at top is the high-gain antenna, pointed toward Earth. Viking 2 landed September 3,1976, some 4600 miles from its twin, Viking 1, which touched down on July 20.

Voir l'image PIA01522: Viking 2 Image of Mars Utopian Plain sur le site de la NASA.

PIA04275: Meridiani Planum

Released April 11, 2003

The designated landing site for the second Mars Exploration Rover mission is Meridiani Planum, seen here in its geological context from NASA Viking images

Details of the Meridiani Planum designated landing site are added with topographic information and higher-resolution imaging from instruments on the Mars Global Surveyor and Mars Odyssey orbiters.

Voir l'image PIA04275: Meridiani Planum sur le site de la NASA.

PIA00189: MC-29 Eridania Region

Mars digital-image mosaic merged with color of the MC-29 quadrangle, Eridania region of Mars. The quadrangle is dominated by heavily cratered highlands, with some moderately cratered plains in the central part and large ridge systems in the southern part. The west-central part is marked by a large impact crater, Kepler. Kepler is an ancient remnant of the many large impact events that occurred during the period of heavy bombardment. Latitude range -65 to 30 degrees, longitude range -180 to -120 degrees.

Voir l'image PIA00189: MC-29 Eridania Region sur le site de la NASA.

PIA00528: 'Mister Badger' Pushing Mars Rock

Viking's soil sampler collector arm successfully pushed a rock on the surface of Mars during the afternoon of Friday, October 8. The irregular-shaped rock was pushed several inches by the Lander's collector arm, which displaced the rock to the left of its original position, leaving it cocked slightly upward. Photographs and other information verified the successful rock push. Photo at left shows the soil sampler's collector head pushing against the rock, named 'Mister Badger' by flight controllers. Photo at right shows the displaced rock and the depression whence it came. Part of the soil displacement was caused by the collector s backhoe. A soil sample will be taken from the site Monday night, October 11. It will then be delivered to Viking s organic chemistry instrument for a series of analyses during the next few weeks. The sample is being sought from beneath a rock because scientists believe that, if there are life forms on Mars, they may seek rocks as shelter from the Sun s intense ultraviolet radiation.

Voir l'image PIA00528: 'Mister Badger' Pushing Mars Rock sur le site de la NASA.

PIA00198: Center is at Latitude 30 Degrees North, Longitude 270 Degrees

Center of the orthographic projection is at latitude 30 degrees N., longitude 270 degrees. The north polar residual ice cap of the Planum Boreum region, which is cut by spiral-patterned troughs, is located at top. The upper part is marked by a large depression, Isidis basin, which contains light-colored plains. The upper part also includes the light-colored smooth plains of Elysium Planitia and dark plains of Vastitas Borealis. Together, these form a vast expanse of contiguous plains. Toward the bottom, on the other hand, the southern hemisphere is almost entirely made up of heavily cratered highlands. At bottom left, a conspicuous, relatively bright circular depression marks the ancient large Hellas impact basin.

Voir l'image PIA00198: Center is at Latitude 30 Degrees North, Longitude 270 Degrees sur le site de la NASA.

PIA03213: Noctis Labyrinthus

As the sun rises over Noctis Labyrinthus (the labyrinth of the night), bright clouds of water ice can be observed in and around the tributary canyons of this high plateau region of Mars. This color composite image, reconstructed through violet, green, and orange filters, vividly shows the distribution of clouds against the rust colored background of this Martian desert.

The picture was reconstructed by JPL's Image Processing Laboratory using in-flight calibration data to correct the color balance.

Scientists have puzzled why the clouds cling to the canyon areas and, only in certain areas, spill over onto the plateau surface. One possibility is that water which condensed during the previous afternoon in shaded eastern facing slopes of the canyon floor is vaporized as the early morning sun falls on those same slopes. The area covered is about 10,000 square kilometers (4000 square miles), centered at 9 degrees South, 95 degrees West, and the large partial crater at lower right is Oudemans. The picture was taken on Viking Orbiter 1's 40th orbit.

Voir l'image PIA03213: Noctis Labyrinthus sur le site de la NASA.

PIA00301: South Polar Residual Ice Cap

This mosaic is composed of 18 Viking Orbiter images (6 each in red, green, and violet filters), acquired on September 28, 1977, during revolution 407 of Viking Orbiter 2. The south pole is located just off the lower left edge of the polar cap, and the 0 degree longitude meridian extends toward the top of the mosaic. The large crater near the right edge (named "South") is about 100 km in diameter. These images were acquired during southern summer on Mars (Ls = 341 degrees); the sub-solar declination was 8 degrees S., and the south polar cap was nearing its final stage of retreat just prior to vernal equinox. The south residual cap is approximately 400 km across, and the exposed surface is thought to consist dominantly of carbon-dioxide frost. This is in contrast to the water-ice surface of the north polar residual cap. It is likely that water ice is present in layers that underlie the south polar cap and that comprise the surrounding layered terrains. Near the top of this image, irregular pits with sharp-rimmed cliffs appear "etched," presumably by wind. A series of rugged mountains (extending toward the upper right corner of the image) are of unknown origin.

Voir l'image PIA00301: South Polar Residual Ice Cap sur le site de la NASA.

PIA00191: Center is at Latitude 30 Degrees South., Longitude 330 Degrees

Center of the orthographic projection is at latitude 30 degrees S., longitude 330 degrees. Heavily cratered highlands dominate this view. Toward the lower right, a conspicuous light-colored circular depression marks the ancient large Hellas impact basin. Directly northeast of Hellas, several large ancient impacts dot the landscape, including Cassini, Schiaparelli, and Huygens. Several large outflow channels are located in the upper left-hand corner. The permanent, residual south polar ice cap is located near the bottom.

Voir l'image PIA00191: Center is at Latitude 30 Degrees South., Longitude 330 Degrees sur le site de la NASA.

PIA00526: Trench Left By Sampler Scoop

PIA00196: Center is at Latitude 30 Degrees South, Longitude 210 Degrees

PIA00172: MC-12 Arabia Region

PIA00175: MC-15 Elysium Region

Mars digital-image mosaic merged with color of the MC-15 quadrangle, Elysium region of Mars. The Elysium quadrangle includes relatively smooth lowland plains immediately north of the more cratered highlands. The plains are interrupted on the northwest by two large shield volcanoes, Elysium Mons and Albor Tholus. The plains are also marked by an elongate crater, Orcus Patera, at the east boundary and a band of knobby terrain that extends northeastward through the eastern part. Latitude range 0 to 30 degrees, longitude range -180 to -135 degrees.

Voir l'image PIA00175: MC-15 Elysium Region sur le site de la NASA.

PIA00568: First Color Image of the Viking Lander 2 Site

The first color picture taken by Viking 2 on the Martian surface shows a rocky reddish surface much like that seen by Viking 1 more than 4000 miles away. The planned location for the collection of soil for on-board analysis is seen in the lower part of the photo. The Lander s camera #2 is looking approximately to the northeast. The right edge of the picture is due east of the spacecraft. The sun is behind the camera in the Martian afternoon. As at Chryse Planitia where Viking 1 landed in July, the sky over Utopia is pink. Colors of the rocks and soil also are almost identical at the two landing sites. Because the spacecraft is tilted about 8 to the west, the horizon appears tilted. In fact, it is nearly level.

Voir l'image PIA00568: First Color Image of the Viking Lander 2 Site sur le site de la NASA.

PIA00397: Boulder 'Big Joe' And Surface Changes On Mars

This pair of pictures from Viking Lander 1 at Mars' Chryse Planitia shows the only unequivocal change in the Martian surface seen by either lander. Both images show the one-meter (3-foot) high boulder nicknamed 'Big Joe.' Just to the lower right of the rock (right photo) is a small-scale slump feature. The picture at left shows a smooth, dust-covered slope; in the picture at right the top surface layer can be seen to have slipped downslope. The event occurred sometime between Oct. 4, 1976, and Jan 24, 1977. (Pictures taken before Oct. 4 do not show the slump; the first picture in which it appears was taken Jan. 24.) The surface layer, between one-half and one centimeter (one-fifth to one-third inch) thick, is apparently less cohesive than the underlying material. The layer that slipped formed a 30-centimeter-long (11.8-inch) 'tongue' of soil and a patch of exposed underlying material. The triggering mechanism for the event is unknown, but could have been temperature variations, wind gusts, a seismic event, or perhaps the lander's touchdown on July 20, 1976.

Voir l'image PIA00397: Boulder 'Big Joe' And Surface Changes On Mars sur le site de la NASA.

PIA00399: Northern Plains Of Mars

This rocky panoramic scene is the second picture of the Martian surface that was taken by Viking Lander 2 shortly after touchdown on September 3 at 3:58 PM PDT (Earth received time). The site is on a northern plain of Mars, at about 48 N. Lat., 226 W. Long., known as Utopia Planitia. The picture sweeps around 330 degrees in azimuth, starting from northwest at the left through north (above the sampler arm housing) past east, where the sky is bright at the center, and southeast toward the right above the radioisotope thermoelectric generator cover. The surface is strewn with rocks out to the horizon, ranging in size up to several meters across. Some pitted rocks resemble fragments of porous volcanic lava. Other rocks have grooves that may have been eroded by windblown sand and dust. Although fine-grained material is seen between the boulders, no sand dunes are evident. The dip in the eastern horizon at the center is an illusion caused by an 8-degree tilt of the Lander toward the west. Actually, the terrain is more level than that at the Viking 1 site. The horizon toward the left of the panorama (northwest) appears featureless, indicating that it may be several kilometers distant. The sky at the center (east) is bright because the sun was above but out of the picture at 10 AM Mars time. Toward the right (southeast), the rocks that are silhouetted against the skyline indicate that the horizon is much nearer, probably because of a slight rise in that area of the terrain. The circular high-gain antenna at the right has clots of fine-grained material adhering to the lower half, some of which appeared to have been sliding downward while the camera was scanning the area. At the extreme right, the banded appearance resulted because the camera continued to scan while it was no longer moving in azimuth. Any motion or other variation in the scene would show up as a change in successive lines.

Voir l'image PIA00399: Northern Plains Of Mars sur le site de la NASA.

PIA04274: Gusev Crater

Released April 11, 2003

The designated landing site for the first Mars Exploration Rover mission is Gusev Crater, seen here in its geological context from NASA Viking images.

Details of the Gusev Crater designated landing site are added with topographic information and higher-resolution imaging from instruments on the Mars Global Surveyor and Mars Odyssey orbiters.

Voir l'image PIA04274: Gusev Crater sur le site de la NASA.

PIA00188: MC-28 Hellas Region

Mars digital-image mosaic merged with color of the MC-28 quadrangle, Hellas region of Mars. The northwestern part includes the eastern half of the ancient large Hellas basin, defined by a rim of rugged mountain blocks that surrounds a nearly circular expanse of light-colored plains. The southwestern part is marked by part of the Amphitrites shield volcano and associated ridged plains that may be basaltic lava flows. The northern part includes a low, dissected shield volcano, Hadriaca Patera, and associated plains that may be basaltic lava flows. These plains are dissected in places by large sinuous channels. The eastern part is dominated by high-standing heavily cratered highlands, perhaps uplifted by the Hellas impact event. Latitude range -65 to -30 degrees, longitude range -120 to -60 degrees.

Voir l'image PIA00188: MC-28 Hellas Region sur le site de la NASA.

PIA00006: Oblique View with Altimetry of Valles Marineris

An oblique, color image of central Valles Marineris, Mars showing relief of Ophir and Candor Chasmata; view toward east. The photograph is a composite of Viking high-resolution images in black and white and low-resolution images in color. Ophir Chasma on the north (left side) is approximately 300 km across and as deep as 10 km. The connected chasma or valleys of Valles Marineris may have formed from a combination of erosional collapse and structural activity. Tongues of interior layered deposits on the floor of the chasmata can be observed as well as young landslide material along the base of Ophir Chasma's north wall.

Voir l'image PIA00006: Oblique View with Altimetry of Valles Marineris sur le site de la NASA.

PIA00181: MC-21 Iapygia Region

Mars digital-image mosaic merged with color of the MC-21 quadrangle, Iapygia region of Mars. Heavily cratered and in places dissected highlands dominate the Iapygia quadrangle. The west-central part is marked by a large impact crater, Huygens. Huygens is an ancient remnant of the many large impact events that occurred during the period of heavy bombardment. The southern one-third is characterized by mountainous and knobby terrain of the northern rim of the enormous Hellas impact basin. Latitude range -30 to 0 degrees, longitude range -90 to -45 degrees.

Voir l'image PIA00181: MC-21 Iapygia Region sur le site de la NASA.

PIA00531: Viking Phase III

VIKING PHASE III - With the incredible success of the Viking missions on Mars, mission operations have progressed though a series of phases - each being funded as mission success dictated its potential. The Viking Primary Mission phase was concluded in November, 1976, when the reins were passed on to the second phase - the Viking Extended Mission. The Extended Mission successfully carried spacecraft operations through the desired period of time needed to provided a profile of a full Martian year, but would have fallen a little short of connecting and overlapping a full Martian year of Viking operations which scientists desired as a means of determining the degree of duplicity in the red planet's seasons - at least for the summer period. Without this continuation of spacecraft data acquisitions to and beyond the seasonal points when the spacecraft actually began their Mars observations, there would be no way of knowing whether the changing environmental values - such as temperatures and winds atmospheric dynamics and water vapor, surface thermal dynamics, etc. - would match up with those acquired as the spacecraft began investigations during the summer and fall of 1976. This same broad interest can be specifically pursued at the surface - where hundreds of rocks, soil drifts and other features have become extremely familiar during long-term analysis. This picture was acquired on the 690th Martian day of Lander 1 operations - 4009th picture sequence commanded of the two Viking Landers. As such, it became the first picture acquired as the third phase of Viking operations got under way - the Viking Continuation Mission. Between the start of the Continuation Mission in April, 1978, until spacecraft operations are concluded in November, the landers will acquire an additional 200 pictures. These will be used to monitor the two landscaped for the surface changes. All four cameras, two on Lander 1 and two on Lander 2, continue to operate perfectly. Both landers will also continue to monitor weather conditions - recording atmospheric pressure and its variations, daily temperature extremes, and wind behavior at the two lander locations.

Voir l'image PIA00531: Viking Phase III sur le site de la NASA.

PIA00415: Hadriaca Patera

A color image of Hadriaca Patera on the northeast rim of Hellas basin of Mars; north toward top. The scene shows a central circular depression surrounded by low radial ridges and, at the bottom of the image, the channel of Dao Vallis. A patera (Latin for shallow dish or saucer) is a volcano of broad areal extent with little vertical relief.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 27 degrees S. to 37 degrees S. and from longitude 263 degrees to 273 degrees; Mercator projection.

Hadriaca Patera is less than 2 km high, has a 60-km-diameter caldera at its center, and is surrounded by a 300-km-wide ring of low ridges. The radial ridges may be lava flows with lava channels at their crests. South of Hadriaca, Dao Vallis begins at a steep-walled depression 40 km across but forms a much shallower channel that extends 800 km southwest into the floor of the Hellas basin. The channel is very likely fluvial in origin, with the release of water being triggered by volcanic activity.

Voir l'image PIA00415: Hadriaca Patera sur le site de la NASA.

PIA00363: Soil Sample Site

High-resolution photo of the Martian surface near the Viking Lander 2 shows a few square meters (yards) at one of the possible spots for acquiring a soil sample. The sample will be collected next Saturday (September 11) by the Lander's trenching scoop and delivered to the spacecraft instruments. The rock in the right foreground is about 25 centimeters (10 inches) across. Most rocks appear to have vesicles, or small holes, in them. Such rocks on Earth can be produced by either volcanic processes or by hypervelocity impacts of meteorites. Some areas are lighter than others, suggesting the presence of two kinds of fine-grained materials, which also can be produced by both volcanic and impact processes. A nearby large impact crater, named Mie, may be the source of the rocks and fine-grained material at the landing site.

Voir l'image PIA00363: Soil Sample Site sur le site de la NASA.

PIA03166: Afternoon on Chryse Planitia - Viking Lander 1 Camera 2 Mosaic

During the Viking Mission, the Viking Lander Camera System acquired many high-resolution images of the scene at Chryse Planitia. Using individual camera events, which occurred on many days throughout the mission, computer mosaics have been created for the site as viewed by each of the two cameras on the spacecraft. Two sets of mosaics were produced of Chryse Planitia; one pair for camera 1 and 2 images acquired in the early morning and one pair for camera 1 and 2 images acquired in the mid-afternoon.

Each complete mosaiced scene extends 342.5 degrees in azimuth, and from approximately 5 degrees above the horizon to 60 degrees below. A complete mosaic incorporated approximately 15 million picture elements (pixels). This mosaic was produced in the early morning (14:00-15:30) by the Camera 2 system on Viking Lander 1. See PIA03165 for the afternoon Camera 1 mosaic and PIA03163 and PIA03164 for the morning mosaics.

Voir l'image PIA03166: Afternoon on Chryse Planitia - Viking Lander 1 Camera 2 Mosaic sur le site de la NASA.

PIA00412: Elysium

A color image of the Elysium Region of Mars; north toward top. The scene shows the Elysium Mons volcano (center), Hecates Tholus (to the north), Albor Tholus (to the south), and the depressions of Elysium Fossae. Mons is a Latin term for mountain; the term tholus designates a small mountain or dome.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 16 degrees N. to 35 degrees N. and from longitude 206 degrees to 220 degrees; Mercator projection.

The Elysium region contain the second largest volcanic complex on Mars, surpassed in size by only the Tharsis complex. Elysium Mons, whose summit elevation is 16,000 m above the Martian datum, is at the crest of a regional topographic rise that emerges steeply and abruptly from the surrounding plains. The relief of Hecates is about 6,000 m and the relief of Albor is only about 4,000 m, because Hecates is on the edge of the rise whereas Albor is on it. After degradation of ancient cratered terrain within the northern lowlands, volcanic rocks erupted from Elysium Mons, Hecates Tholus, and Albor Tholus in Elysium Planitia. Elysium Fossae are volcano/tectonic troughs that parallel graben in the area. Some troughs are connected with channels to the east indicating an interaction between volcanic and hydrothermal systems.

Voir l'image PIA00412: Elysium sur le site de la NASA.

PIA00364: Rocky Martian Plain

The rocky Martian plain surrounding Viking 2 is seen in high resolution in this 85-degree panorama sweeping from north at the left to east at right during the Martian afternoon on September 5. Large blocks litter the surface. Some are porous, sponge-like rocks like the one at the left edge (size estimate: 1 1/2 to 2 feet); others are dense and fine-grained, such as the very bright rounded block (1 to 1 1/2 feet across) toward lower right. Pebbled surface between the rocks is covered in places by small drifts of very fine material similar to drifts seen at the Viking 1 landing site some 4600 miles to the southwest. The fine-grained material is banked up behind some rocks, but wind tails seen by Viking 1 are not well-developed here. On the right horizon, flat-topped ridges or hills are illuminated by the afternoon sun. Slope of the horizon is due to the 8-degree tilt of the spacecraft.

Voir l'image PIA00364: Rocky Martian Plain sur le site de la NASA.

PIA00186: MC-26 Argyre Region

PIA00162: MC-2 Diacria Region

PIA02984: Photomosiac of Olympus Mons

PIA00165: MC-5 Ismenius Lacus Region

PIA00420: Crater Moreux

Color image of part of the Ismenius Lacus region of Mars (MC-5 quadrangle) containing the impact crater Moreux (right center); north toward top. The scene shows heavily cratered highlands in the south on relatively smooth lowland plains in the north separated by a belt of dissected terrain, containing flat-floored valleys, mesas, and buttes. This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 36 degrees N. to 50 degrees N. and from longitude 310 degrees to 340 degrees; Lambert conformal conic projection. The dissected terrain along the highlands/lowlands boundary consists of the flat-floored valleys of Deuteronilus Mensae (on left) and Prontonilus Mensae (on right) and farther north the small, rounded hills of knobby terrain. Flows on the mensae floors contain striae that run parallel to valley walls; where valleys meet, the striae merge, similar to medial moraines on glaciers. Terraces within the valley hills have been interpreted as either layered rocks or wave terraces. The knobby terrain has been interpreted as remnants of the old, densely cratered highland terrain perhaps eroded by mass wasting.

Voir l'image PIA00420: Crater Moreux sur le site de la NASA.

PIA00387: Northeast View from Viking Landing Site

This Mars view looks northeast from Viking 1 and completes the 360 panorama of the landing site begun earlier with the spacecraft's other camera. A layer of haze can be seen in the Martian sky. Large dark boulders dominate the scene. The largest boulder (center) is about 3 meters (10 feet) wide and one meter (3 feet) high. Rocks in the foreground are lighter and appear mottled. The rocks may have been derived from lava flows or stream deposits which are visible on orbiter images. These deposits may have been redistributed by impact craters. The fine material visible between the rocks has dune morphology and appears to have been deposited by wind.

Voir l'image PIA00387: Northeast View from Viking Landing Site sur le site de la NASA.

PIA00576: Martian Sunrise at Utopia Planitia

A Martian sunrise was captured in this Viking 2 Lander picture taken June 14, 1978, at the spacecraft's Utopia Planitia landing site. The data composing this image were acquired just as the Sun peaked over the horizon on the Lander's 631st sol (Martian solar day). Pictures taken at dawn (or dusk) are quite dark except where the sky is brightened above the Sun's position. The glow in the sky results as light from the Sun is scattered and preferentially absorbed by tiny particles of dust and ice in the atmosphere. When the Viking cameras are calibrated for darker scenes, the "sky glow" tends to saturate their sensitivity and produce the bright regions seen here. The "banding" and color separation effects are also artifacts, rather than real features, and are introduced because the cameras are not able to record continuous gradations of light. The cameras must represent such gradations in steps (bands) of brightness and color, and the process sometimes produces some "false" colors within the bands. The scattering of light closest to the Sun's position tends to enhance blue wavelengths. The narrowing sky glow nearer the horizon above the Sun's position occurs as a result of light extinction. At that elevation, the optical path of sunlight through the atmosphere is at its longest penetration angle, and a substantial portion of the light is simply prevented from reaching the cameras by the dust, ice particles and other material in its way.

NASA's Langley Research Center was the primary and extended mission manager; JPL assumed management for continued mission operations.

Voir l'image PIA00576: Martian Sunrise at Utopia Planitia sur le site de la NASA.

PIA00571: Ice on Mars Utopia Planitia Again

This high-resolution color photo of the surface of Mars was taken by Viking Lander 2 at its Utopia Planitia landing site on May 18, 1979, and relayed to Earth by Orbiter 1 on June 7. It shows a thin coating of water ice on the rocks and soil. The time the frost appeared corresponds almost exactly with the buildup of frost one Martian year (23 Earth months) ago. Then it remained on the surface for about 100 days. Scientists believe dust particles in the atmosphere pick up bits of solid water. That combination is not heavy enough to settle to the ground. But carbon dioxide, which makes up 95 percent of the Martian atmosphere, freezes and adheres to the particles and they become heavy enough to sink. Warmed by the Sun, the surface evaporates the carbon dioxide and returns it to the atmosphere, leaving behind the water and dust. The ice seen in this picture, like that which formed one Martian year ago, is extremely thin, perhaps no more than one-thousandth of an inch thick.

Voir l'image PIA00571: Ice on Mars Utopia Planitia Again sur le site de la NASA.

PIA00567: Sunset at the Viking Lander 1 Site

This color image of the Martian surface in the Chryse area was taken by Viking Lander 1, looking southwest, about 15 minutes before sunset on the evening of August 21. The sun is at an elevation angle of 3 or 4 degrees above the horizon and about 50 degrees clockwise from the right edge of the frame. Local topographic features are accentuated by the low lighting angle. A depression is seen near the center of the picture, just above the Lander�s leg support structure, which was not evident in previous pictures taken at higher sun angles. Just beyond the depression are large rocks about 30 centimeters (1 foot) across. The diffuse shadows are due to the sunlight that has been scattered by the dusty Martian atmosphere as a result of the long path length from the setting sun. Toward the horizon, several bright patches of bare bedrock are revealed.

Voir l'image PIA00567: Sunset at the Viking Lander 1 Site sur le site de la NASA.

PIA00398: Surface Sampler Arm

Photographic evidence of the successful series of commands to the Viking 1 lander on Mars that unlocked the surface sampler arm is seen in this picture. At lower left, to the right of a whitish area is a small oblong object -- the boom latch pin that had failed to drop out of the scoop assembly causing the mechanism to lock. With the pin free, the boom and scoop can now be used for the soil sampler experiments beginning in two days, including a search for microscopic life in the Martian soil. The boom latch pin is 0.2 inches in diameter and 3.2 inches long. The pin weights 0.44 ounces, fell from about three feet and impacted the surface at eight to nine feet per second producing a mini-crater with a dark ejecta blanket. These data will be studies to determine soil properties.

Voir l'image PIA00398: Surface Sampler Arm sur le site de la NASA.

PIA00174: MC-14 Amenthes Region

PIA00569: Bright Summer Afternoon on the Mars Utopian Planitia

A UTOPIAN BRIGHT SUMMER AFTERNOON ON MARS--Looking south from Viking 2 on September 6, the orange-red surface of the nearly level plain upon which the spacecraft sits is seen strewn with rocks as large as three feet across. Many of these rocks are porous and sponge-like, similar to some of Earth's volcanic rocks. Other rocks are coarse-grained such as the large rock at lower left. Between the rocks, the surface is blanketed with fine-grained material that, in places, is piled into small drifts and banked against some of the larger blocks. The cylindrical mast with the orange cable is the low-gain antenna used to receive commands from Earth.

Voir l'image PIA00569: Bright Summer Afternoon on the Mars Utopian Planitia sur le site de la NASA.

PIA00396: Viking Lander 2's First Picture On The Surface Of Mars

Viking 2 s first picture on the surface of Mars was taken within minutes after the spacecraft touched down on September 3. The scene reveals a wide variety of rocks littering a surface of fine-grained deposit. Boulders in the 10 to 20-centimeter (4 to 8-inch) size range-- some vesicular (holes) and some apparently fluted by wind--are common. Many of the pebbles have tabular or platy shapes, suggesting that they may be derived from layered strata. The fluted boulder just above the Lander s footpad displays a dust-covered or scraped surface, suggesting it was overturned or altered by the foot at touchdown. Just as occurred with Viking l s first picture on July 20, brightness variations at the beginning of the picture scan (left edge) probably are due to dust settling after landing. A substantial amount of fine-grained material kicked up by the descent engines has accumulated in the concave interior of the footpad. Center of the image is about 1.4 meters (5 feet) from the camera. Field of view extends 70 from left to right and 20 from top to bottom. Viking 2 landed at a region called Utopia in the northern latitudes about 7500 kilometers (4600 miles) northeast of Viking l s landing on the Chryse plain 45 days earlier.

Voir l'image PIA00396: Viking Lander 2's First Picture On The Surface Of Mars sur le site de la NASA.

PIA00391: Sand Dunes And Large Rocks Revealed By Camera 1

Sand dunes and large rocks are revealed in this panorama picture of Mars, the first photograph taken by Viking l's Camera 1 on July 23. The horizon is approximately 3 kilometers (2 miles) away. The left and right thirds of this picture are the same areas that were photographed on July 20 (Sol O) by Camera 2 and provide stereo coverage. The middle third reveals a part of the Martian surface not seen on the July 20 panorama. The late afternoon sun is high in the sky over the left side of the picture. The support struts of the S-band high-gain antenna extend to the top of the picture. The American flags are located on the two RTG (Radioisotope Thermoelectric Generator) wind screens. In the middle third of the picture, the rocky surface is covered by thick deposits of wind-blown material, forming numerous dunes. At the center of the picture on the horizon are two low hills which may be part of the rim of a distant crater. Two very large rocks are visible in the middleground; the nearer one is 3 meters (10 feet) in diameter and is 8 meters (25 feet) from the spacecraft. A cloud layer is visible halfway between the horizon and the top of the picture. The meteorology boom is located right of center. Behind it, the 'White Mesa' is visible, which could be seen on the far left side of the Sol O Camera 2 panorama. In the near ground are numerous rocks about 10 cm (4 inches) across, with horseshoe-shaped scour marks on their upwind side and wind tails in their lee. The fine-grained material in front of them contains small pits formed by impact of material kicked out by the Lander spacecraft's rocket engines.

Voir l'image PIA00391: Sand Dunes And Large Rocks Revealed By Camera 1 sur le site de la NASA.

PIA00173: MC-13 Syrtis Major Region

PIA00403: West Candor Chasma

During its examination of Mars, the Viking 1 spacecraft returned images of Valles Marineris, a huge canyon system 5,000 km long, up to 240 km wide, and 6.5 km deep, whose connected chasma or valleys may have formed from a combination of erosional collapse and structural activity. The view shows west Candor Chasma, one of the connected valleys of Valles Marineris; north toward top of frame. The image is a composite of Viking high-resolution (about 80 m/pixel or picture element) images in black and white and low resolution (about 250 m/pixel) images in color. The Viking 1 craft landed on Mars in July of 1976. West Candor Chasma occupies the westernmost part of the large west-northwest-trending trough of Candor Chasma. This section is about 150 km wide. West Candor Chasma is bordered on the north and south by straight-walled cliffs, most likely faults, and on its west by two segments of north-northeast-trending cliffs. The north wall is dissected by landslide scars forming reentrants filled with landslide debris. The south wall shows spur-and-gully morphology and smooth sections. The high-standing central mesa, informally dubbed Red Mesa has several curvilinear reentrants carved into the caprock, whose anomalously colored layers were interpreted to be caused by young hydrothermal alteration products (Geissler et al., 1993, Icarus, v. 106, p. 380-391). Light-colored lobes flow away from the top of the interior stack and then flow around and embay the same layered stack from which they originated. One of these apparent flow features is composed of at least two or perhaps even three huge, superposed, vaguely layered, very rugged, light-colored lobes as much as 100 km long, 20 km wide, and over 2 km thick. The layered deposits below the caprock also merge with a chaotic material that has local lobate fronts and overlaps landslide deposits. Hummocky material, similar in hue to wall rock, fills the southwestern-most region of west Candor Chasma and is perhaps as much as 3 km thick (Lucchitta, 1990, Icarus, v. 86, p. 476- 509). The light-colored lobes, chaotic material, and hummocky fill may be mass wasting deposits due to wholesale collapse of older interior deposits (Lucchitta, 1996, LPSC XXVII abs., p. 779- 780); this controversial idea requires that the older layered deposits were saturated with ice, perhaps from former lakes and that young volcanism and/or tectonism melted the ice and made the material flow.

Voir l'image PIA00403: West Candor Chasma sur le site de la NASA.

PIA00527: Ejected Shroud on the Martian Surface

Shining on the Martian surface near the Viking 2 spacecraft is the aluminum shroud, or cover, which protected the collector head of the surface sampler instrument during Viking's year-long journey from Earth. On September 5, two days after Viking 2 landed, the surface sampler was rotated from its parked position atop the spacecraft and pointed downward about 40 degrees. The shroud was then ejected by a set of eight springs positioned around its base. It struck the porous rock at the bottom of the picture, bounced about 20 inches, hit the surface again and bounced another 20 inches. The scar left by the second bounce is faintly visible halfway between the shroud and the rock it struck. The shroud is 12 inches long and 4 1/2 inches in diameter. The large rock just beyond it is about 2 feet long and about a foot thick. At lower right is the support structure of one of the spacecraft s three landing legs.

Voir l'image PIA00527: Ejected Shroud on the Martian Surface sur le site de la NASA.

PIA00197: Center is at Latitude 30 Degrees North, Longitude 150 Degrees

Center of the orthographic projection is at latitude 30 degrees N., longitude 150 degrees. The north polar residual ice cap, which is cut by spiral-patterned troughs and surrounded by the dark lowland plains of Vastitas Borealis, is located at the top. The right-central part is dominated by the Tharsis Montes volcanoes. The most prominent of the Tharsis Montes volcanoes is the largest known volcano in the solar system, Olympus Mons. The light-colored lowland plains of Amazonis, Elysium, and Arcadia Planitiae lies north and west of Olympus Mons. The heavily cratered highlands dominate the lower one-third.

Voir l'image PIA00197: Center is at Latitude 30 Degrees North, Longitude 150 Degrees sur le site de la NASA.

PIA00190: MC-30 Mare Australe Region

Mars digital-image mosaic merged with color of the MC-30 quadrangle, Mare Australe region of Mars. The central part is dominated by a permanent residual ice cap that is enclosed by layered and troughed terrain. This cap is much smaller than the northern ice cap due to differing amounts of solar heating. The layered and troughed terrain is encircled by heavily and moderately cratered terrains that include unique depositional and erosional landforms, including large pits, troughs, and complex ridge systems. Latitude range -90 to -60 degrees, longitude range -180 to 180 degrees.

Voir l'image PIA00190: MC-30 Mare Australe Region sur le site de la NASA.

PIA00300: Olympus Mons

Shown here is a digital mosaic of Olympus Mons, the largest known volcano in the Solar System. It is 27 kilometers high, over 600 kilometers at the base, and is surrounded by a well-defined scarp that is up to 6 km high. Lava flows drape over the scarp in places. Much of the plains surrounding the volcano are covered by the ridged and grooved 'aureole' of Olympus Mons. The origin of the aureole is controversial, but may be related to gravity sliding off of the flanks of an ancestral volcano. The summit caldera (central depression) is almost 3 km deep and 25 km across. It probably formed from recurrent collapse following drainage of magma resulting from flank eruptions.

Voir l'image PIA00300: Olympus Mons sur le site de la NASA.

PIA00529: VL1 Digs A Deep Hole On Mars

VIKING LANDER DIGS A DEEP HOLE ON MARS -- This six-inch-deep, 12- inch-wide, 29-inch-long hole was dug Feb. 12 and 14 by Viking Lander 1 as the first sequence in an attempt to reach a foot beneath the surface of the red planet. The activity is in the same area where Lander 1 acquired its first soil samples last July. The trench was dug by repeatedly backhoeing in a left-right-center pattern. The backhoe teeth produced the small parallel ridges at the far end of the trench (upper left). The larger ridges running the length of the trench are material left behind during the backhoe operation. What appears to be small rocks along the ridges and in the soil at the near end of the trench are really small dirt clods. The clods and the steepness of the trench walls indicate the material is cohesive and behaves something like ordinary flour. After a later sequence, to be performed March 1 and 2, a soil sample will be taken from the bottom of the trench for inorganic soil analysis and later for biology analysis. Information about the soil taken from the bottom of the trench may help explain the weathering process on Mars and may help resolve the dilemma created by Viking findings that first suggest but then cast doubt on the possibility of life in the Martian soil. The trench shown here is a result of one of the most complex command sequences yet performed by the lander. Viking l has been operating at Chryse Planitia on Mars since it landed July 20, 1976.

Voir l'image PIA00529: VL1 Digs A Deep Hole On Mars sur le site de la NASA.

PIA00199: Candor Chasm in Valles Marineris

PIA00179: MC-19 Margaritifer Sinus Region

PIA00336: West Candor Chasm, Approximately Natural Color

This picture (centered at latitude 4 degrees S., longitude 76 degrees W.) shows parts of central Valles Marineris, including Candor Chasm (lower left), Ophir Chasm (lower right), and Hebes Chasm (upper right). Complex layered deposits in the canyons may have been deposited in lakes, and if so, are of great interest for future searches for fossil life on Mars. The pinkish deposits in Candor Chasm (enhanced color version PIA00155) may be due to hydrothermal alterations and the production of crystalline ferric oxides (Geissler et al., 1993, Icarus 106, 380). Viking Orbiter Picture Numbers 279B02 (violet), 279B10 (green), and 279B12 (red) at 240 m/pixel resolution. Picture width is 2231 km. North is 47 degrees clockwise from top.

Voir l'image PIA00336: West Candor Chasm, Approximately Natural Color sur le site de la NASA.

PIA00564: Vivid Colors of the Viking Lander 1 Scene

Viking 1 obtained this color picture of the Martian surface and sky on July 24. Camera Number 1 facing southeast, captured part of the spacecraft's gray structure in the foreground. A bright orange cable leads to one of the descent rocket engines. Orange-red surface materials cover most of the surface, apparently forming a thin veneer over darker bedrock. A zone of large dark boulders is present in the far-field. The sky has a reddish cast, which is probably due to scattering and reflection from reddish sediment suspended in the lower atmosphere. This picture has been radiometrically calibrated, using information on camera performance acquired before launch. Although the colors are very vivid, the fidelity with which the bright orange cable is reproduced suggests that the intense colors of the Martian surface are, in fact, real.

Voir l'image PIA00564: Vivid Colors of the Viking Lander 1 Scene sur le site de la NASA.

PIA00563: First Color Image From Viking Lander 1

This color picture of Mars was taken July 21--the day following Viking l's successful landing on the planet. The local time on Mars is approximately noon. The view is southeast from the Viking. Orange-red surface materials cover most of the surface, apparently forming a thin veneer over darker bedrock exposed in patches, as in the lower right. The reddish surface materials may be limonite (hydrated ferric oxide). Such weathering products form on Earth in the presence of water and an oxidizing atmosphere. The sky has a reddish cast, probably due to scattering and reflection from reddish sediment suspended in the lower atmosphere. The scene was scanned three times by the spacecraft's camera number 2, through a different color filter each time. To assist in balancing the colors, a second picture was taken of z test chart mounted on the rear of the spacecraft. Color data for these patches were adjusted until the patches were an appropriate color of gray. The same calibration was then used for the entire scene.

Voir l'image PIA00563: First Color Image From Viking Lander 1 sur le site de la NASA.

PIA00392: The Meteorology Instrument on Viking Lander 1

Those Martian weather reports, received here daily from more than 200 million miles away, start right here at Viking l's meteorology instrument. Mounted atop the extended boom, the meteorology sensors face away from the spacecraft. They stand about four feet above the surface and measure atmospheric pressure, temperature, wind velocity and wind direction. The cable parallel to the boom is connected inside the spacecraft body with the electronics for operating the sensors, reading the data and preparing it for transmission to Earth. A second Mars weather station will begin operation next month when Viking 2 lands somewhere in the planet's northern latitude Viking 2 arrives at Mars and goes into orbit tomorrow (August 7).

Voir l'image PIA00392: The Meteorology Instrument on Viking Lander 1 sur le site de la NASA.

PIA00170: MC-10 Lanae Palus Region

PIA00177: MC-17 Phoenicis Region

Mars digital-image mosaic merged with color of the MC-17 quadrangle, Phoenicis Lacus region of Mars. Two of the four largest shield volcanoes on Mars are within the northwestern part, the south half of Pavonis Mons and Arsia Mons. The eastern part includes Syria and Sinai Plana. Most of the quadrangle forms the Tharsis plateau--the highest plateau on Mars; its elevation, 10 km, is twice that of the Tibetan Plateau, the highest plateau on Earth. Also in the northeastern part is Noctis Labyrinthus, a complex system of fault valleys at the west end of Valles Marineris. The south-central part is marked by the large fault system, Claritas Fossae. Latitude range -30 to 0 degrees, longitude range 90 to 135 degrees.

Voir l'image PIA00177: MC-17 Phoenicis Region sur le site de la NASA.

PIA00338: Claritas Fossae, Approximately Natural Color

Syria Planum-centered volcanism and tectonism produced fractures, narrow to broad grabens, large scarps, and broad fold and thrust ridges that deformed a basement complex. Picture is centered at latitude 29 degrees S., longitude 101 degree W. The region appears to have been mantled by materials of unknown origin. Colors seen in the enhanced color version (PIA00154) are due to variable proportions of dust and sand and possibly to different kinds of weathering or alterations. Viking Orbiter Picture Numbers 421A42 (violet), 421A48 (green), and 421A50 (red) at 106 m/pixel resolution. Picture width is 117 km. North is 101 degree clockwise from top.

Voir l'image PIA00338: Claritas Fossae, Approximately Natural Color sur le site de la NASA.

PIA00395: The Collector Head Of Viking Lander 1's Surface Sampler

The collector head of Viking l's surface sampler is full of Martian soil destined for the gas chromatograph mass spectrometer, the instrument which analyzes the surface material for the presence of organic molecules. The material was scooped out of the surface on August 3, but the sampler arm stopped operating while transporting it to the instrument. The Martian soil will be deposited into the instrument's processor today. The surface sampler is operating properly, but the cause of last week's problem is not yet known. This picture, taken Monday (August 9), was made for operational purposes, focusing on the collector head. Hence, the out-of-focus view of the Martian surface.

Voir l'image PIA00395: The Collector Head Of Viking Lander 1's Surface Sampler sur le site de la NASA.

PIA00193: Latitude 90 Degrees North to 90 Degrees South and Longitude 0 Degrees to 180 Degrees

The coordinates of the Lambert azimuthal equal area projection are latitude 90 degrees N. to 90 degrees S. and longitude 0 degree to 180 degrees. Both polar residual ice caps are seen at top and bottom. The central part is dominated by the four largest and youngest volcanoes on Mars--Olympus, Arsia, Pavonis, and Ascraeus Montes--and by a vast system of canyons several thousand kilometers long--Valles Marineris. Directly to the northeast of Valles Marineris, several large outflow channels terminate at a dark depression, Chryse basin. The lower-right corner is marked by the large Argyre basin, defined by an expanse of light-colored plains 800 km across.

Voir l'image PIA00193: Latitude 90 Degrees North to 90 Degrees South and Longitude 0 Degrees to 180 Degrees sur le site de la NASA.

PIA00407: Global Color Views of Mars

About 1000 Viking Orbiter red- and violet-filter images have been processed to provide global color coverage of Mars at a scale of 1 km/pixel. Individual image frames acquired during a single spacecraft revolution were first processed through radiometric calibration, cosmetic cleanup, geometric control, reprojection, and mosaicing. We have produced a total of 57 "single-rev" mosaics. All of the mosaics are geometrically tied to the Mars Digital Image Mosaic, a black-and-white base map with a scale of 231 m/pixel. We selected a subset of single-rev mosaics that provide the best global coverage (least atmospheric obscuration and seasonal frost); photometric normalization was applied to remove atmospheric effects and normalize the variations in illumination and viewing angles. Finally, these normalized mosaics were combined into global mosaics. Global coverage is about 98% complete in the red-filter mosaic and 95% complete in the violet-filter mosaic. Gaps were filled by interpolation. A green-filter image was synthesized from an average of the red and violet filter data to complete a 3-color set. The Viking Orbiters acquired actual green-filter images for only about half of the Martian surface. The final mosaic has been reprojected into several map projections. The orthographic view shown here is centered at 20 degrees latitude and 60 degrees longitude. The orthographic view is most like the view seen by a distant observer looking through a telescope. The color balance selected for these images was designed to be close to natural color for the bright reddish regions such as Tharsis and Arabia, but the data have been "stretched" such that the relatively dark regions appear darker and less reddish that their natural appearance. This stretching allows us to better see the color and brightness variations on Mars, which are related to the composition or physical structure of the surface materials, which include volcanic lava flows, wind- and water-deposited sedimentary rocks, and (at the poles) ice caps. The north polar cap is visible in this projection at the top of the image, the great equatorial canyon system (Valles Marineris) below center, and four huge Tharsis volcanoes (and several smaller ones) at left. Also note heavy impact cratering of the highlands (bottom and right portions of this mosaic) and the younger, less heavily cratered terrains elsewhere.

Voir l'image PIA00407: Global Color Views of Mars sur le site de la NASA.

PIA00145: Surface Sampler Arm Acquiring Sample

Operation of the surface sampler in obtaining Martian soil for Viking 2's molecular analysis experiment last Saturday (September 25) was closely monitored by one of the Lander cameras because of the precision required in trenching the small area--8 by 9 inches-surrounded by rocks. Dubbed 'Bonneville Salt Flats,' the exposure of thin crust appeared unique in contrast with surrounding materials and became a prime target for organic analysis in spite of potential hazards. Large rock in foreground is 8 inches high. At left, the sampler scoop has touched the surface, missing the rock at upper left by a comfortable 6 inches, and the backhoe has penetrated the surface about one-half inch. The scoop was then pulled back to sample the desired point and (second photo) the backhoe furrowed the surface pulling a piece of thin crust toward the spacecraft. The initial touchdown and retraction sequence was used to avoid a collision between a rock in the shadow of the arm and a plate joining the arm and scoop. The rock was cleared by 2 to 3 inches. The third picture was taken 8 minutes after the scoop touched the surface and shows that the collector head has acquired a quantity of soil. With surface sampler withdrawn (right), the foot-long trench is seen between the rocks. The trench is three inches wide and about 1 1/2 to 2 inches deep. The scoop reached to within 3 inches of the rock at far end of trench. Penetration appears to have left a cavernous opening roofed by the crust and only about one inch of undisturbed crust separates the deformed surface and the rock.

Voir l'image PIA00145: Surface Sampler Arm Acquiring Sample sur le site de la NASA.

PIA00194: Latitude 90 Degrees North to 90 Degrees South and Longitude -180 Degrees to 0 Degrees

The coordinates of the Lambert azimuthal equal area projection are latitude 90 degrees N. to 90 degrees S. and longitude -180 degrees to 0 degrees. The north polar residual ice cap of the Planum Boreum region, which is cut by spiral-patterned troughs, is located at top. The upper part is marked by large depression, Isidis basin, which contains light-colored plains. The upper part also includes the light-colored smooth plains of Elysium Planitia and dark plains of Vastitas Borealis. Together, these form a vast expanse of contiguous plains. Toward the bottom, on the other hand, the southern hemisphere is almost entirely made up of heavily cratered highlands. Toward the bottom, a conspicuous, relatively bright circular depression marks the ancient large Hellas impact basin.

Voir l'image PIA00194: Latitude 90 Degrees North to 90 Degrees South and Longitude -180 Degrees to 0 Degrees sur le site de la NASA.

PIA00409: Alba Patera

A color image of the Alba Patera region of Mars; north toward top. The scene shows a central circular depression surrounded by splays of fractures, named Alba Fossae (west of Alba Patera) and Tantalus Fossae (east of Alba Patera). A patera (Latin for shallow dish or saucer) is a volcano of broad areal extent with little vertical relief; a fossa is a linear depression.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 30 degrees N. to 50 degrees N. and from longitude 95 degrees to 125 degrees; Lambert projection.

Alba Patera has a 100-km-diameter caldera at its center surrounded by a fracture ring. In total, the approximately 1,200- km-diameter Alba Patera far exceeds any other known volcano in areal extent; it covers eight times the area of Olympus Mons (the highest volcano in the Solar System) but reaches only about 6 km in height. The patera lies directly north of the Tharsis bulge, which encompasses the most intensely and most recently active volcanic region of the planet. The fossae of the Alba area are fault-bound graben that can be traced south through the Tharsis bulge and therefore likely formed by upwarping of the Tharsis bulge as well as the coeval upwelling of Alba Pateria magma.

Voir l'image PIA00409: Alba Patera sur le site de la NASA.

PIA00005: Oblique View of Valles Marineris

An oblique, color image of central Valles Marineris, Mars showing relief of Ophir and Candor Chasmata; view toward north. The photograph is a composite of Viking high-resolution images in black and white and low-resolution images in color. Ophir Chasma on the north is approximately 300 km across and as deep as 10 km. The connected chasma or valleys of Valles Marineris may have formed from a combination of erosional collapse and structural activity. Tongues of interior layered deposits on the floor of the chasmata can be observed as well as young landslide material along the base of Ophir Chasma's north wall.

Voir l'image PIA00005: Oblique View of Valles Marineris sur le site de la NASA.

PIA00418: Chryse Outflow Channel

A color image of the south Chryse basin Valles Marineris outflow channels on Mars; north toward top. The scene shows on the southwest corner the chaotic terrain of the east part of Valles Marineris and two of its related canyons: Eos and Capri Chasmata (south to north). Ganges Chasma lies directly north. The chaos in the southern part of the image gives rise to several outflow channels, Shalbatana, Simud, Tiu, and Ares Valles (left to right), that drained north into the Chryse basin. The mouth of Ares Valles is the site of the Mars Pathfinder lander.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 20 degrees S. to 20 degrees N. and from longitude 15 degrees to 53 degrees; Mercator projection.

The south Chryse outflow channels are cut an average of 1 km into the cratered highland terrain. This terrain is about 9 km above datum near Valles Marineris and steadily decreases in elevation to 1 km below datum in the Chryse basin. Shalbatana is relatively narrow (10 km wide) but can reach 3 km in depth. The channel begins at a 2- to 3-km-deep circular depression within a large impact crater, whose floor is partly covered by a chaotic material, and ends in Simud Valles. Tiu and Simud Valles consist of a complex of connected channel floors and chaotic terrain and extend as far south as and connect to eastern Valles Marineris. Ares Vallis originates from discontinuous patches of chaotic terrain within large craters. In the Chryse basin the Ares channel forks; one branch continues northwest into central Chryse Planitia (Latin for plain) and the other extends north into eastern Chryse Planitia.

Voir l'image PIA00418: Chryse Outflow Channel sur le site de la NASA.

PIA00411: Apollinaris Patera

A color image of the Apollinaris Patera Region of Mars; north toward top. The scene shows the 80-km-wide central caldera of Apollinaris, a plume of young flows extending south down the flank of the volcano, a cliff and chaotic terrain west of the volcano, and the surrounding younger deposits of the Medusae Fossae Formation (north and east). A patera (Latin for shallow dish or saucer) is a volcano of broad areal extent with little vertical relief.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 12 degrees S. to 6 degrees S. and from longitude 182 degrees to 189 degrees; Mercator projection.

Apollinaris Patera is an isolated volcano (about 400 km across) lying on the Martian highlands just north of Gusev impact crater and the termination of Ma'adim Vallis. After the main edifice was built, eruption continued on the volcano's southern flank to form a broad ridge overlapping the original shield. Breakdown of ice-rich materials formed chaos on its western edge. Finally the friable materials (possible ash?) of the Medusae Fossae Fm were deposited.

Voir l'image PIA00411: Apollinaris Patera sur le site de la NASA.

PIA03165: Afternoon on Chryse Planitia - Viking Lander 1 Camera 1 Mosaic

Each complete mosaiced scene extends 342.5 degrees in azimuth, and from approximately 5 degrees above the horizon to 60 degrees below. A complete mosaic incorporated approximately 15 million picture elements (pixels). This mosaic was produced in the early morning (14:00-15:30) by the Camera 1 system on Viking Lander 1. See PIA03166 for the afternoon Camera 2 mosaic and PIA03163 and PIA03164 for the morning mosaics.

Voir l'image PIA03165: Afternoon on Chryse Planitia - Viking Lander 1 Camera 1 Mosaic sur le site de la NASA.

PIA00185: MC-25 Thaumasia Region

Mars digital-image mosaic merged with color of the MC-25 quadrangle, Thaumasia region of Mars. In the northern part, a prominent physiographic feature, Thaumasia plateau, includes a complex array of small- and large-scale faults and ridges and ancient volcanoes. Channel systems, upturned beds, and large troughs occur in places along the southern edge of the plateau. In the southern part, the lowlands that surround the plateau include heavily cratered highland terrain and relatively smooth, low plains. The east-central part is marked by a relatively young large impact crater, Lowell. Lowell is one of several large, relatively young impact events on Mars that followed the period of heavy bombardment. Latitude range -65 to -30 degrees, longitude range 60 to 120 degrees.

Voir l'image PIA00185: MC-25 Thaumasia Region sur le site de la NASA.

PIA00154: Claritas Fossae (Enhanced Color)

Syria Planum-centered volcanism and tectonism produced fractures, narrow to broad grabens, large scarps, and broad fold and thrust ridges that deformed a basement complex. Picture is centered at latitude 29 degrees S., longitude 101 degrees W. The region appears to have been mantled by materials of unknown origin. Colors seen are due to variable proportions of dust and sand and possibly to different kinds of weathering or alterations. Viking Orbiter Picture Numbers 421A42 (violet), 421A48 (green), and 421A50 (red) at 106 m/pixel resolution. Picture width is 117 km. North is 101 degrees clockwise from top.

Voir l'image PIA00154: Claritas Fossae (Enhanced Color) sur le site de la NASA.

PIA00182: MC-22 Mare Tyrrhenum Region

PIA00532: Surface Changes in Chryse Planitia

At the conclusion of the Viking Continuation Mission (May to November, 1978), all four cameras on the Viking Landers - two on each spacecraft - continued to function normally. During the two and one-half years since the landers touched down on Mars, images totaled 2,255 for Viking Lander 1 and 2,016 for Viking Lander 2. The surface around the landers was completely photographed by the end of 1976; subsequent images acquired during 1977-1978 have concentrated on searching for changes in the scene - changes which can be used to infer both the types of erosive processes which modify the landscape around the landers and the rates at which these processes may occur. The major surface changes have included the water-ice snow seen by Lander 2 during the winter at Utopia Planitia, and a thin dust layer deposited at both sites during the dust storms of 1977. The most recently identified change occurred at Chryse Planitia between VL-1 sols 767 (Sept. 16, 1978) and 771 (Sept. 20, 1978) as seen in the lower photo. Picture at top, selected to show similar lighting conditions, was taken during sol 25 (August 15, 1976). The change (A) appears as a small circle-like formation on the side of a drift in the lee, or downwind, side of Whale Rock. This is believed to have been a small-scale landslide of an unstable dust layer which had accumulated behind the rock. Interpretation of this feature would be difficult without an earlier change (B) near Big Joe, a slump which occurred between sols 74 and 183. The new slump is approximately 25- 35 meters from the lander, and just under a meter across. The slumping probably was initiated by the daily heating and cooling of the surface by solar radiation. More importantly, it is now believed that, based on the repeated occurrence of such slumping features, a dust layer which overlies the surface may in fact be redistributed fairly regularly during periods of high wind activity. There are no obvious indications of fossil slump features, therefore similar features must be destroyed on a regular basis. After the end of February, when Viking operations essentially terminate, Lander 1 will continue preselected observations over a period of possibly up to 10 years, following the instructions stored in its computer memory. Earth commands will be required only to initiate data transmission to Earth. During this time, it is now anticipated that one of the yearly planetwide global dust storms may reach an intensity necessary to shift the dust cover around the lander significantly.

Voir l'image PIA00532: Surface Changes in Chryse Planitia sur le site de la NASA.

PIA00153: Reull Valles (Enhanced Color)

A conspicuous fretted channel, Reull Valles, which dissects wall deposits of the large Hellas impact basin, trends southeast towards the basin floor. Center of picture is at latitude 42 degrees S., longitude 258 degrees W. Fretted channels are wide, flat-floored channels with steep walls, which may be runoff channels that have been modified and enlarged by masswasting. Many nearby hills and mountains are surrounded by lobate debris aprons, which may have formed by slow creep of rock deposits aided by the presence of near-surface ice. Layering is exposed in the channel and crater walls. The color variations of the surface are very bland in this region; most of the variations seen are due to atmospheric scattering. Viking Orbiter Picture Numbers 126A08 (violet), 126A16 (green), and 126A24 (red) at 157 m/pixel resolution. Picture width is 161 km. North is 112 degrees clockwise from top.

Voir l'image PIA00153: Reull Valles (Enhanced Color) sur le site de la NASA.

PIA00416: Hellas Planitia

A color image of the Hellas Planitia region of Mars; north toward top. The scene shows the Hellas plain within the 1,800- km-diameter Hellas basin, an ancient impact basin (and the largest basin on Mars) formed when a large projectile (asteroid, comet, meteor) hit the surface.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 60 degrees S. to 20 degrees S. and from longitude 250 degrees to 320 degrees. Mercator projection is used between latitudes 20 degrees S. and 30 degrees S.; Lambert projection is used below latitude 30 degrees S.

The exact diameter of the ancient Hellas basin is difficult to determine because large portions of the rim are missing to the northeast and southwest. In addition several large patera or low volcanoes (Tyrrhena, Hadriaca, Amphitrites) occur along or near the rim and their flows have partially buried the older impact deposits. Outside the rim are several large, arcuate, inward-facing escarpments which could be remnants of multiple rings. The plains of Hellas are very complex; fluvial channels drain into the basin and the plains have been described as being a mixture of fluvial, lacustrine, glacial, eolian, and volcanic deposits. Frequent dust storms occur within the basin.

Voir l'image PIA00416: Hellas Planitia sur le site de la NASA.

PIA01141: Geologic 'Face on Mars' Formation

NASA's Viking 1 Orbiter spacecraft photographed this region in the northern latitudes of Mars on July 25, 1976 while searching for a landing site for the Viking 2 Lander. The speckled appearance of the image is due to missing data, called bit errors, caused by problems in transmission of the photographic data from Mars to Earth. Bit errors comprise part of one of the 'eyes' and 'nostrils' on the eroded rock that resembles a human face near the center of the image. Shadows in the rock formation give the illusion of a nose and mouth. Planetary geologists attribute the origin of the formation to purely natural processes. The feature is 1.5 kilometers (one mile) across, with the sun angle at approximately 20 degrees. The picture was taken from a range of 1,873 kilometers (1,162 miles).

Voir l'image PIA01141: Geologic 'Face on Mars' Formation sur le site de la NASA.

PIA00166: MC-6 Casius Region

PIA02987: Photomosiac of the Tharsis Region

Viking 1 Orbiter color mosaic of the eastern Tharsis region on Mars. At left, from top to bottom, are the three 25 km high volcanic shields, Ascraeus Mons, Pavonis Mons, and Arsia Mons. The shield at upper right is Tharsis Tholus. The canyon system at lower right is Noctis Labyrinthus, the westernmost extension of Valles Marineris. The smooth area at bottom center is Syria Planum. The distance between the calderas of Ascraeus and Pavonis Mons is 800 km. North is up. The images used to produce this mosaic were taken during orbit 1334 on 22 February 1980. (Viking 1 Orbiter MG01N104-334S0)

Voir l'image PIA02987: Photomosiac of the Tharsis Region sur le site de la NASA.

PIA00384: Debris Kicked Up By Impact of A Protective Cover from Viking Lander 1

The patch of dark material toward the top of this picture (arrow) taken by the Viking 1 Lander is the debris kicked up by the impact of a protective cover ejected from the spacecraft at 1 a.m. today. The cylindrical cover, which bounced out of view of the camera, protects the scoop at the end of the soil sampler arm. (The scoop will dig into the Martian surface for the first time on July 28). Dust and debris atop the footpad remains as it was seen in the Lander's first picture taken immediately after landing two days ago. No wind modification is apparent. On the surface, a variety of block sizes, shapes and tones are seen, and some rocks are Partially buried.

Voir l'image PIA00384: Debris Kicked Up By Impact of A Protective Cover from Viking Lander 1 sur le site de la NASA.

PIA00383: First Panoramic View From The Surface Of Mars

First panoramic view by Viking 1 from the surface of Mars. The out of focus spacecraft component toward left center is the housing for the Viking sample arm, which is not yet deployed. Parallel lines in the sky are an artifact and are not real features. However, the change of brightness from horizon towards zenith and towards the right (west) is accurately reflected in this picture, taken in late Martian afternoon. At the horizon to the left is a plateau-like prominence much brighter than the foreground material between the rocks. The horizon features are approximately three kilometers (1.8 miles) away. At left is a collection of fine-grained material reminiscent of sand dunes. The dark sinuous markings in left foreground are of unknown origin. Some unidentified shapes can be perceived on the hilly eminence at the horizon towards the right. A horizontal cloud stratum can be made out halfway from the horizon to the top of the picture. At left is seen the low gain antenna for receipt of commands from the Earth. The projections on or near the horizon may represent the rims distant impact craters. In right foreground are color charts for Lander camera calibration, a mirror for the Viking magnetic properties experiment and part of a grid on the top of the Lander body. At upper right is the high gain dish antenna for direct communication between landed spacecraft and Earth. Toward the right edge is an array of smooth fine-grained material which shows some hint of ripple structure and may be the beginning of a large dune field off to the right of the picture, which joins with dunes seen at the top left in this 300� panoramic view. Some of the rocks appear to be undercut on one side and partially buried by drifting sand on the other.

Voir l'image PIA00383: First Panoramic View From The Surface Of Mars sur le site de la NASA.

PIA00424: East Candor Chasma

East Candor Chasma occupies the eastern part of the large west-northwest-trending trough of Candor Chasma. This section is about 150 km wide. East Candor Chasma is bordered on the north and south by walled cliffs, most likely faults. The walls may have been dissected by landslides forming reentrants; one area on the north wall shows what appears to be landslide debris. Both walls show spur-and-gully morphology and smooth sections. In the lower part of the image northwest-trending, linear depressions on the plateau are younger graben or fault valleys that cut the south wall.

Material central to the chasma shows layering in places and has been locally eroded by the wind to form flutes and ridges. These interior layered deposits have curvilinear reentrants carved into them, and in one locale a lobe flows away from the top of the interior deposit. The lobe may be mass-wasting deposits due to collapse of older interior deposits (Lucchitta, 1996, LPSC XXVII abs., p. 779- 780); this controversial idea requires that the older layered deposits were saturated with ice, perhaps from former lakes, and that young volcanism and/or tectonism melted the ice and made the material flow.

Voir l'image PIA00424: East Candor Chasma sur le site de la NASA.

PIA00161: MC-1 Mare Boreum Region

PIA00572: Big Joe in the Chryse Planitia

Near the Viking 1 Lander on the Chryse Plains of Mars, 'Big Joe' stands a silent vigil. This large, often-photographed dark rock has a topping of reddish fine-grained silt that spills down its sides. It is about 2 meters (6.6 feet) long and lies about 8 meters (26 feet) from the spacecraft. The rough texture of the sides shows it to be coarse grained. Big Joe appears to be part of a field of large blocks that has a roughly circular alignment and which may be part of the rim of an ancient degraded crater. Some of the other blocks of the field can be seen to the left, extending out toward the horizon, perhaps 1.5 kilometers (1 mile) away. Drifts of fine-grained material cover the surface to the right and left of Big Joe. The part of the Lander that is visible in the lower left is the cover of the nuclear power supply.

Voir l'image PIA00572: Big Joe in the Chryse Planitia sur le site de la NASA.

PIA00168: MC-8 Amazonis Region

Mars digital-image mosaic merged with color of the MC-8 quadrangle, Amazonis region of Mars. The central part, which is dominated by light-colored, relatively smooth to hummocky plains of Amazonis Planitia, is partly bounded to the east by the western flank of the largest known volcano in the solar system, Olympus Mons, and its associated aureole deposits. Moderately cratered knobby terrain is west of the plains of Amazonis Planitia. Latitude range 0 to 30 degrees, longitude range 135 to 180 degrees.

Voir l'image PIA00168: MC-8 Amazonis Region sur le site de la NASA.

PIA00408: Tharsis

A color image of the Tharsis region of Mars; north toward top. The scene shows the Tharsis bulge, a huge ridge covered by the 3 large aligned Tharsis Montes shield volcanoes (from lower left to right): Arsia, Pavonis, and Ascraeus Mons. To the left of the Tharsis Montes lies the huge Olympus Mons shield volcano, followed clockwise by Alba Patera (north center), several smaller volcanoes, and the linear depressions of Mareotis and Tempe Fossae (upper right).

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 50 degrees N. to 20 degrees S. and from longitude 85 degrees to 150 degrees. Mercator projection is used between latitudes 20 degrees S. and 30 degrees N.; Lambert projection is used above latitude 30 degrees N.

The Tharsis bulge encompasses the most intensely and most recently active volcanic region of the planet. Each Tharsis Montes volcano is 350-400 km in diameter and about 17 km above the surrounding plain. The volcanoes are about 700 km apart and appear to be above a major northeast-trending fracture zone along the bulge, now buried by volcanic deposits. Olympus Mons (left center) is the largest known volcano in the Solar System. It is 27 km high, over 600 km at the base, and is surrounded by a well-defined scarp that is up to 6 km high. The summit calderas (central depressions) of all four volcanoes probably formed from recurrent collapse following drainage of magma resulting from flank eruptions. 1,600-km-diameter Alba Patera (north center) far exceeds any other known volcano in areal extent; it covers eight times the area of Olympus Mons but reaches only about 6 km in height. Fossae (linear depressions) of the Tharsis area are fault-bound graben formed by upwarping of the Tharsis bulge.

Voir l'image PIA00408: Tharsis sur le site de la NASA.

PIA00525: High-Resolution Mosaic - Mars Rocky Horizon

ON A CLEAR DAY ON MARS, you can see tens of thousands of rocks. Two high-resolution scans by one of Viking 2's cameras were mosaiced to create this scene looking northeast to the horizon some three kilometers (two miles) away. The rock in the lower right corner is 10 inches across. The largest rock near the center of the picture is about two feet long and one foot high. What appears to be a small channel winds from upper left to lower right. Slope of the horizon is due to the eight-degree tilt of landed spacecraft.

Voir l'image PIA00525: High-Resolution Mosaic - Mars Rocky Horizon sur le site de la NASA.

PIA00195: Center is at Latitude 30 Degrees South, Longitude 90 Degrees

Center of the orthographic projection is at latitude 30 degrees S., longitude 90 degrees. The top half is dominated by the Tharsis Montes volcanoes, the large Alba Patera shield volcano, the dark Chryse basin, and a vast canyon system, Valles Marineris. In the central part, a prominent physiographic feature, Thaumasia plateau, includes a complex array of small- and large-scale faults and ridges and ancient volcanoes. The large conspicuous Argyre basin, southeast of the Thaumasia plateau, contains a broad expanse of light-colored plains 800 km across. The permanent south polar ice cap is located near the bottom.

Voir l'image PIA00195: Center is at Latitude 30 Degrees South, Longitude 90 Degrees sur le site de la NASA.

PIA00192: Center is at Latitude 30 Degrees North, Longitude 30 Degrees

Center of the orthographic projection is at latitude 30 degrees N., longitude 30 degrees. The north polar residual ice cap, which is cut by spiral-patterned troughs, is located at the top. The central part is characterized by a dark depression, Chryse basin, where several large outflow channels terminate. The lower-left corner is marked by a vast system of canyons, Valles Marineris, which extends eastward for several thousand kilometers.

Voir l'image PIA00192: Center is at Latitude 30 Degrees North, Longitude 30 Degrees sur le site de la NASA.

PIA00176: MC-16 Memnonia Region

PIA00339: Memnonia Fossae, Approximately Natural Color

Tharsis-centered volcanic and tectonic activity resulted in the formation of radial grabens of Memnonia Fossae, which cut materials of the ancient cratered highlands and the relatively young, highland-embaying lava flows from the Tharsis volcanoes. Center of picture is at latitude 16 degrees S., longitude 142 degrees W. Natural color version shows albedo variations and uniform colors. The enhanced color version (PIA00151, following decorrelation stretch), however, reveals a diversity of subtle color variations; many of the color variations may be due to different lava flow units and variable amounts of weathering, possible alteration by water, and eolian redistributions. Viking Orbiter Picture Numbers 41B52 (green), 41b54 (red), and 41B56 (blue) at 198 m/pixel resolution. Picture width is 206 km. North is 119 degrees counter-clockwise from top.

Voir l'image PIA00339: Memnonia Fossae, Approximately Natural Color sur le site de la NASA.

PIA04304: The Target

PIA00393: Martian Dune Field

This spectacular picture of the Martian landscape by the Viking 1 Lander shows a dune field with features remarkably similar to many seen in the deserts of Earth. The dramatic early morning lighting - 7:30 a.m. local Mars time--reveals subtle details and shading. Taken yesterday (August 3) by the Lander s camera #1, the picture covers 100 , looking northeast at left and southeast at right. Viking scientists have studied areas very much like the one in this view in Mexico and in California (Kelso, Death Valley, Yuma). The sharp dune crests indicate the most recent wind storms capable of moving sand over the dunes in the general direction from upper left to lower right. Small deposits downwind of rocks also indicate this wind direction. Large boulder at left is about eight meters (25 feet) from the spacecraft and measures about one by three meters (3 by 10 feet). The meteorology boom, which supports Viking s miniature weather station, cuts through the picture s center. The sun rose two hours earlier and is about 30 above the horizon near the center of the picture.

Voir l'image PIA00393: Martian Dune Field sur le site de la NASA.

PIA00171: MC-11 Oxia Palus Region

PIA00178: MC-18 Coprates Region

Mars digital-image mosaic merged with color of the MC-18 quadrangle, Coprates region of Mars. Moderately cratered and faulted highland ridged plains in the northern and southern parts are cut by the prominent Valles Marineris chasma system, which reaches depths of 10 km and extends in an east-southeast direction for about 2,500 km across the quadrangle. The long, central canyons appear to be large, fault-bounded rifts, whereas some of the isolated, northern canyons are the sources of large outflow channels. Latitude range -30 to 0 degrees, longitude range 45 to 90 degrees.

Voir l'image PIA00178: MC-18 Coprates Region sur le site de la NASA.

PIA00337: Melas Chasm, Approximately Natural Color

This picture (centered at latitude 10 degrees S., longitude 74 degrees W.) shows much of Melas Chasm and a portion of Candor Chasm (upper right) in central Valles Marineris. Several interesting compositional units can be seen in the enhanced-color image (PIA00156): white materials (center-right) may consist of carbonates or some other evaporite deposit, pinkish materials (upper right) may be relatively rich in crystalline iron oxides, and greenish materials (lower left) correspond to dark sand dunes. Viking Orbiter Picture Numbers 279B41 (violet), 279B49 (green), and 279B51 (red) at 257 m/pixel resolution. Picture width is 261 km. North is 50 degrees clockwise from top.

Voir l'image PIA00337: Melas Chasm, Approximately Natural Color sur le site de la NASA.

PIA00169: Mc-9 Tharsis Region

PIA00425: Ophir Chasma

This point-perspective, digital image, centered at latitude 4 degrees S., longitude 71 degrees, is a composite of Viking 1 Orbiter high-resolution (about 80 m/pixel or picture element) images in black and white and low-resolution (about 250 m/pixel) images in color; no vertical exaggeration. The Viking 1 craft landed on Mars in July of 1976.

Ophir Chasma is a large west-northwest-trending trough about 100 km wide. The Chasma is bordered by 4 km high walled cliffs, most likely faults, that show spur-and-gully morphology and smooth sections. The walls have been dissected by landslides forming reentrants; one area (upper left) on the north wall shows a young landslide about 100 km wide. The volume of the landslide debris is more than 1000 times greater than that from the May 18, 1980 debris avalanche from Mount St. Helens. The longitudinal grooves seen in the foreground are thought to be due to differential shear and lateral spreading at high velocities. The landslide passes between mounds of interior layered deposits on the floor of the chasma.

Voir l'image PIA00425: Ophir Chasma sur le site de la NASA.

PIA00382: First Panoramic View From The Surface Of Mars

First panoramic view by Viking 1 from the surface of Mars. (Top): The out-of-focus spacecraft component toward left center is the housing for the Viking sample arm, which is not yet deployed. Parallel lines in the sky are an artifact and are not real features. However, the change of brightness from horizon towards zenith and towards the right (west) is accurately reflected in this picture, taken in late Martian afternoon. At the horizon to the left is a plateau-like prominence much brighter than the foreground material between the rocks. The horizon features are approximately three kilometers (1.8 miles) away. At left is a collection of fine-grained material reminiscent of sand dunes. The dark sinuous markings in left foreground are of unknown origin. Some unidentified shapes can be perceived on the hilly eminence at the horizon towards the right. Patches of bright sand can be discerned among the rocks and boulders in middle distance. In right fore-ground are two peculiarly shaped rocks which may possibly be ventifacts produced by wind abrasion on Mars. A horizontal cloud stratum can be made out halfway from the horizon to the top of the picture. (Bottom): At left is seen the low gain antenna for receipt of commands from the Earth. The projections on or near the horizon may represent the rims distant impact craters. In right foreground are color charts for Lander camera calibration, a mirror for the Viking magnetic properties experiment and part of a grid on the top of the Lander body. At upper right is the high-gain dish antenna for direct communication between landed space-craft and Earth. Toward the right edge is an array of smooth fine-grained material which shows some hint of ripple structure and may be the beginning of a large dune field off to the right of the picture, which joins with dunes seen at the top left in this 300 panoramic view. Some of the rocks appear to be undercut on one side and partially buried by drifting sand on the other.

Voir l'image PIA00382: First Panoramic View From The Surface Of Mars sur le site de la NASA.

PIA00167: MC-7 Cebrenia Region

PIA00092: Syrtis Major Hemisphere

This mosaic is composed of about 100 red- and violet- filter Viking Orbiter images, digitally mosaiced in an orthographic projection at a scale of 1 km/pixel. The images were acquired in 1980 during early northern summer on Mars (Ls = 75 degrees). The center of this image is near latitude 0 degree, longitude 310 degree, and the limits of this mosaic are approximately latitude -60 to 60 degrees and longitude 260 to 350 degrees. The color variations have been enhanced by a factor of two, and the large-scale brightness variations (mostly due to sun-angle variations) have been normalized by large-scale filtering. The large circular area with a bright yellow color (in this rendition) located in the upper left area of the image is known as Arabia. The boundary between the ancient, heavily-cratered southern highlands and the younger northern plains occurs far to the north (latitude 40 degrees) on this side of the planet, just north of Arabia. The dark blue area to the right of Arabia, called Syrtis Major Planum, is a low-relief volcanic shield of probable basaltic composition. The bright yellow area to the right of Syrtis Major Isidis Planitia, an ancient impact basin. Bright white areas to the south, including the Hellas impact basin at lower right, are covered by carbon dioxide frost.

Voir l'image PIA00092: Syrtis Major Hemisphere sur le site de la NASA.

PIA00385: High Resolution Image From Viking Lander 1

Viking 1 took this high-resolution picture today, its third day on Mars. Distance from the camera to the nearfield (bottom) is about 4 meters (13 feet); to the horizon, about 3 kilometers (1.8 miles). The photo shows numerous angular blocks ranging in size from a few centimeters to several meters. The surface between the blocks is composed of fine-grained material. Accumulation of some fine-grained material behind blocks indicates wind deposition of dust and sand downwind of obstacles. The large block on the horizon is about 4 meters (13 feet) wide. Distance across the horizon is about 34 meters (110 feet).

Voir l'image PIA00385: High Resolution Image From Viking Lander 1 sur le site de la NASA.

PIA00422: Valles Marineris

A color image of Valles Marineris, the great canyon of Mars; north toward top. The scene shows the entire canyon system, over 3,000 km long and averaging 8 km deep, extending from Noctis Labyrinthus, the arcuate system of graben to the west, to the chaotic terrain to the east.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color; Mercator projection. The image extends from latitude 0 degrees to 20 degrees S. and from longitude 45 degrees to 102.5 degrees.

The connected chasma or valleys of Valles Marineris may have formed from a combination of erosional collapse and structural activity. Layers of material in the eastern canyons might consist of carbonates deposited in ancient lakes. Huge ancient river channels began from Valles Marineris and from adjacent canyons and ran north. Many of the channels flowed north into Chryse Basin, which contains the site of the Viking 1 Lander and the future site of the Mars Pathfinder Lander.

Voir l'image PIA00422: Valles Marineris sur le site de la NASA.

PIA00183: MC-23 Aeolis Region

Mars digital-image mosaic merged with color of the MC-23 quadrangle, Aeolis region of Mars. The southern part is dominated by heavily cratered highlands that are cut by two large channels having features characteristic of terrestrial river beds. The highlands are separated from the northern plains of Elysium Planitia by a highly dissected, discontinuous northwest trending scarp. The northeastern part is marked by a large shield volcano, Apollinaris Patera. Latitude range - 30 to 0 degrees, longitude range -180 to -135 degrees.

Voir l'image PIA00183: MC-23 Aeolis Region sur le site de la NASA.

PIA00533: Ice On Mars

ICE ON MARS AGAIN -- This high-resolution photo of the surface of Mars was taken by Viking Lander 2 at its Utopia Planitia landing site on May 18, 1979 and relayed to Earth by Viking Orbiter 1 on June 7. It shows a thin coating of water ice on the rocks and soil. The time the frost appeared corresponds almost exactly with the buildup of frost one Martian year (23 Earth months) ago. Then it remained on the surface for about 100 days. Scientists believe dust particles in the atmosphere pick up bits of solid water. That combination is not heavy enough to settle to the ground. But carbon dioxide, which makes up 95 percent of the Martian atmosphere, freezes and adheres to the particles and they become heavy enough to sink. Warmed by the Sun the surface evaporates the carbon dioxide and returns it to the atmosphere leaving behind the water and dust. The ice seen in this picture, like that which formed one Martian year ago is extremely thin perhaps no more than one-thousandth of an inch thick.

Voir l'image PIA00533: Ice On Mars sur le site de la NASA.

PIA00152: North Polar Cap Margin (natural color (top) and enhanced color (bottom))

Water ice mixed with dust form the residual north polar ice cap (brown color). Seasonal frost of relatively pure ice (white color) partly blankets the polar deposits. A large trough, which is occupied by linear sand dunes (dark band), exposes polar layered deposits. The layered deposits hold a partial record of the history of atmospheric activity and climate of Mars. Center of picture is at latitude 82 degrees N., longitude 84 degrees W. Viking Orbiter Picture Numbers 82B11-12 (violet), 82B15-16 (green), and 82B17-18 (red) at 53 m/pixel resolution. Picture width is 106 km. North is 6 degrees counter-clockwise from top.

Voir l'image PIA00152: North Polar Cap Margin (natural color (top) and enhanced color (bottom)) sur le site de la NASA.

PIA00417: Nilosyrtis Mensae

A color image of part of the Nilosyrtis Mensae region of Mars containing the impact craters Antoniadi and Baldet (south to north) in the lower left corner; north toward top. The scene shows heavily cratered highlands on the south separated from the relatively smooth lowland plains on the northeast corner by a belt of dissected terrain, containing flat-floored valleys, mesas, buttes, and channels. The channels are (left to right) Auqakuh and Huo Hsing Valles; Nili Fossae lie in lower right corner of image.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 20 degrees N. to 40 degrees N. and from longitude 280 degrees to 305 degrees. Mercator projection is used below 30 degrees N.; Lambert projection is used above 30 degrees N.

The dissected terrain along the highlands/lowlands boundary consist of the flat-floored valleys (mensae) and farther north the small, rounded hills of knobby terrain. Flows on the mensa floors contain striae that run parallel to valley walls; where valleys meet, the striae merge, similar to medial moraines on glaciers. Terraces within the valley hills have been interpreted as either layer rocks or wave terraces. The knobby terrain has been interpreted as remnants of the old, densely cratered highland terrain perhaps eroded by mass wasting. Auqakuh and Huo Hsing Valles and Nili Fossae are fretted channels and linear depressions that likely formed by sapping and mass wasting along lines of structural weakness.

Voir l'image PIA00417: Nilosyrtis Mensae sur le site de la NASA.

PIA03163: Morning on Chryse Planitia - Viking Lander 1 Camera 1 Mosaic

Each complete mosaiced scene extends 342.5 degrees in azimuth, and from approximately 5 degrees above the horizon to 60 degrees below. A complete mosaic incorporated approximately 15 million picture elements (pixels). This mosaic was produced in the early morning (7:00-8:00) by the Camera 1 system on Viking Lander 1. See PIA03164 for the morning Camera 2 mosaic and PIA03165 and PIA03166 for the afternoon mosaics.

Voir l'image PIA03163: Morning on Chryse Planitia - Viking Lander 1 Camera 1 Mosaic sur le site de la NASA.

PIA00410: Amphitrites Patera

A color image of the Amphitrites Patera region of Mars; north toward top. The scene shows several indistinct ring structures and radial ridges of an old volcano named Amphitrites Patera. A patera (Latin for shallow dish or saucer) is a volcano of broad areal extent with little vertical relief.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 55 degrees S. to 62 degrees S. and from longitude 292 degrees to 311 degrees; Lambert projection.

Amphitrites Patera is a 138-km-diameter feature on the south rim of Hellas impact basin and is one of many indistinct ring structures in the area. The location of the paterae in this area of Hellas indicates that their source magma may have been influenced by the transition fractures of the basin. The radial ridges of Amphitrites extend for about 400 km north into the Hellas basin.

Voir l'image PIA00410: Amphitrites Patera sur le site de la NASA.

PIA03164: Morning on Chryse Planitia - Viking Lander 1 Camera 2 Mosaic

This mosaic was produced in the early morning (7:00-8:00) by the Camera 2 system on Viking Lander 1. See PIA03163 for the morning Camera 1 mosaic and PIA03165 and PIA03166 for the afternoon mosaics.

Voir l'image PIA03164: Morning on Chryse Planitia - Viking Lander 1 Camera 2 Mosaic sur le site de la NASA.

PIA00184: MC-24 Phaethontis Region

PIA00155: West Candor Chasm (Enhanced Color)

This picture (centered at latitude 4 degrees S., longitude 76 degrees W.) shows areas of central Valles Marineris, including Candor Chasm (lower left), Ophir Chasm (lower right), and Hebes Chasm (upper right). Complex layered deposits in the canyons may have been deposited in lakes, and if so, are of great interest for future searches for fossil life on Mars. The pinkish deposits in Candor Chasm may be due to hydrothermal alterations and the production of crystalline ferric oxides (Geissler et al., 1993, Icarus 106,380). Viking Orbiter Picture Numbers 279B02 (violet), 279B10 (green), and 279B12 (red) at 240 m/pixel resolution. Picture width is 231 km. North is 47 degrees clockwise from top.

Voir l'image PIA00155: West Candor Chasm (Enhanced Color) sur le site de la NASA.

PIA00003: Valles Marineris Hemisphere

Mosaic composed of 102 Viking Orbiter images of Mars, covering nearly a full hemisphere of the planet (approximate latitude -55 to 60 degrees, longitude 30 to 130 degrees). The mosaic is in a point-perspective projection with a scale of about 1 km/pixel. The color variations have been enhanced by a factor of about two, and the large-scale brightness variations (mostly due to sun-angle variations) have been normalized by large-scale filtering. The center of the scene shows the entire Valles Marineris canyon system, over 3,000 km long and up to 8 km deep, extending from Noctis Labyrinthus, the arcuate system of graben to the west, to the chaotic terrain to the east. Bright white layers of material in the eastern canyons may consist of carbonates deposited in ancient lakes. Huge ancient river channels begin from the chaotic terrain and from north-central canyons and run north. Many of the channels flowed into a basin called Acidalia Planitia, which is the dark area in the extreme north of this picture. The Viking 1 landing site (Mutch Memorial Station) is located in Chryse Planitia, south of Acidalia Planitia. The three Tharsis volcanoes (dark red spots), each about 25 km high, are visible to the west. The large crater with two prominent rings located at the bottom of this image is named Lowell, after the Flagstaff astronomer. The images were acquired by Viking Orbiter 1 in 1980 during early northern summer on Mars (Ls = 70 degrees); the atmosphere was relatively dust-free. A variety of clouds appear as bright blue streaks and hazes, and probably consist of water ice. Long, linear clouds north of central Valles Marineris appear to emanate from impact craters.

Voir l'image PIA00003: Valles Marineris Hemisphere sur le site de la NASA.

PIA00004: Schiaparelli Hemisphere

This mosaic is composed of about 100 red- and violet- filter Viking Orbiter images, digitally mosaiced in an orthographic projection at a scale of 1 km/pixel. The images were acquired in 1980 during mid northern summer on Mars (Ls = 89 degrees). The center of the image is near the impact crater Schiaparelli (latitude -3 degrees, longitude 343 degrees). The limits of this mosaic are approximately latitude -60 to 60 degrees and longitude 280 to 30 degrees. The color variations have been enhanced by a factor of two, and the large-scale brightness variations (mostly due to sun-angle variations) have been normalized by large-scale filtering. The large circular area with a bright yellow color (in this rendition) is known as Arabia. The boundary between the ancient, heavily-cratered southern highlands and the younger northern plains occurs far to the north (latitude 40 degrees) on this side of the planet, just north of Arabia. The dark streaks with bright margins emanating from craters in the Oxia Palus region (to the left of Arabia) are caused by erosion and/or deposition by the wind. The dark blue area on the far right, called Syrtis Major Planum, is a low-relief volcanic shield of probable basaltic composition. Bright white areas to the south, including the Hellas impact basin at the lower right, are covered by carbon dioxide frost.

Voir l'image PIA00004: Schiaparelli Hemisphere sur le site de la NASA.

PIA00419: Scamander Vallis

A color image of Scamander Vallis on Mars; north toward top. The scene shows heavily cratered highlands dissected by the slightly sinuous gully of Scamander Vallis. The channel begins by dissecting a steep slope of an impact crater wall and abruptly ends about 180 km north of the crater.

This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 13 degrees N. to 19 degrees N. and from longitude 330 degrees to 332 degrees; Mercator projection.

The lack of tributaries, fairly straight path, and steep walls of the channel suggest spring sapping as a mode of origin. The abrupt termination may have resulted from burial by younger deposits or perhaps the flows percolated into the surface materials and continued underground.

Voir l'image PIA00419: Scamander Vallis sur le site de la NASA.