Mars by Viking, 1975 through 1987.

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.

Spacecraft: Viking Orbiter 1

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.

Spacecraft: Viking Orbiter 1

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.

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.

Mars digital-image mosaic merged with color of the MC-9 quadrangle, Tharsis region of Mars. Three of the four largest shield volcanoes on Mars--Olympus, Ascraeus, and Pavonis Montes--lie within the Tharsis quadrangle, together with several smaller shields. The north-central part is marked by highly faulted terrain of Ceraunius Fossae. Latitude range 0 to 30 degrees, longitude range 90 to 135 degrees.

Mars digital-image mosaic merged with color of the MC-10 quadrangle, Lanae Palus region of Mars. The western part is dominated by lava flows of the Tharsis region. The central part includes ridged terrain of Lunae Planum. The west and north borders of Lunae Planum are dissected by the large, relatively young outflow channel, Kasei Vallis, which terminates in Chryse Planitia. Latitude range 0 to 30 degrees, longitude range 45 to 90 degrees.

Mars digital-image mosaic merged with color of the MC-11 quadrangle, Oxia Palus region of Mars. Heavily cratered highlands of the southeastern two-thirds are cut by several large outflow channels. These channels terminate at the dark large depression, Chryse basin, which contain relatively smooth plains in the northwestern part. Latitude range 0 to 30 degrees, longitude range 0 to 45 degrees.

Mars digital-image mosaic merged with color of the MC-12 quadrangle, Arabia region of Mars. Heavily cratered highlands dominate the Arabia quadrangle. The northeastern part is marked by a large impact crater, Cassini. Cassini is an ancient remnant of the many large impact events that occurred during the period of heavy bombardment. Latitude range 0 to 30 degrees, longitude range -45 to 0 degrees.

Mars digital-image mosaic merged with color of the MC-13 quadrangle, Syrtis Major region of Mars. The central part is dominated by dark dust and lava flows of the Syrtis Major Planitia region. These lava flows are partly bounded to the east by a large depression, Isidis basin, which contains smooth plains, and to the west and north by heavily cratered and moderately faulted highlands. Latitude range 0 to 30 degrees, longitude range -90 to -45 degrees.

Mars digital-image mosaic merged with color of the MC-14 quadrangle, Amenthes region of Mars. The southern part includes heavily cratered highlands. The northern part is dominated by relatively smooth plains of Elysium Planitia and the eastern half of the Isidis basin. Latitude range 0 to 30 degrees, longitude range -135 to -90 degrees.

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.

Mars digital-image mosaic merged with color of the MC-16 quadrangle, Memnonia region of Mars. Heavily cratered highlands in the southern two-thirds are cut in the northeastern part by a large outflow channel, Mangala Vallis. The highlands are bounded to the north by undulating wind-eroded deposits and to the east by lava flows of the Tharsis region. Latitude range -30 to 0 degrees, longitude range 135 to 180 degrees.

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.

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.

Mars digital-image mosaic merged with color of the MC-19 quadrangle, Margaritifer Sinus region of Mars. Heavily cratered highlands, which dominate the Margaritifer Sinus quadrangle, are marked by large expanses of chaotic terrain. In the northwestern part, the major rift zone of Valles Marineris connects with a broad canyon filled with chaotic terrain. Latitude range -30 to 0, longitude range 0 to 45 degrees.

Mars digital-image mosaic merged with color of the MC-20 quadrangle, Sinus Sabeus region of Mars. Heavily cratered highlands dominate the Sinus Sabeus quadrangle. The northern part is marked by a large impact crater, Schiaparelli. Schiaparelli is an ancient remnant of the many large impact events that occurred during the period of heavy bombardment. Latitude range -30 to 0 degrees, longitude range -45 to 0.

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.

Mars digital-image mosaic merged with color of the MC-22 quadrangle, Mare Tyrrhenum region of Mars. Heavily cratered highlands dominate the Mare Tyrrhenum quadrangle. The central part is marked by a large shield volcano, Tyrrhena Patera, and associated ridged plains of Hesperia Planum that probably are made up of basaltic lava flows. Latitude range -30 to 0 degrees, longitude range -135 to -90 degrees.

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.

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.

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.

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.

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.

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.

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.

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. 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Photo from Viking Lander 2 shows late-winter frost on the ground on Mars around the lander. The view is southeast over the top of Lander 2, and shows patches of frost around dark rocks. The surface is reddish-brown; the dark rocks vary in size from 10 centimeters (four inches) to 76 centimeters (30 inches) in diameter. This picture was obtained Sept. 25, 1977. The frost deposits were detected for the first time 12 Martian days (sols) earlier in a black-and-white image. Color differences between the white frost and the reddish soil confirm that we are observing frost. The Lander Imaging Team is trying to determine if frost deposits routinely form due to cold night temperatures, then disappear during the warmer daytime. Preliminary analysis, however, indicates the frost was on the ground for some time and is disappearing over many days. That suggests to scientists that the frost is not frozen carbon dioxide (dry ice) but is more likely a carbon dioxide clathrate (six parts water to one part carbon dioxide). Detailed studies of the frost formation and disappearance, in conjunction with temperature measurements from the lander's meteorology experiment, should be able to confirm or deny that hypothesis, scientists say.

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.

Color mosaic of Olympus Mons volcano on Mars from the Viking 1 Orbiter. The mosaic was created using images from orbit 735 taken 22 June 1978. Olympus Mons is about 600 km in diameter and the summit caldera is 24 km above the surrounding plains. The complex aureole terrain is visible at the top of the frame. North is up. (Viking 1 Orbiter MH20N133-735A)

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)

This mosaic of Mars is a compilation of images captured by the Viking Orbiter 1. 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.