Photo: NASA/JPL/University Of Arizona Image 1 of / 44 44
Dark narrow streaks called recurring slope lineae emanating out of the walls of Garni crater on Mars. The dark streaks here are up to few hundred meters in length. They are hypothesized to be formed by flow of briny liquid water on Mars. The image is produced by draping an orthorectified (RED) image (ESP_031059_1685) on a Digital Terrain Model (DTM) of the same site produced by High Resolution Imaging Science Experiment (University of Arizona). Vertical exaggeration is 1.5.
Photo: NASA/JPL/University Of Arizona Dark narrow streaks called recurring slope lineae emanating out of...
Image 2 of 44 This undated photo provided by NASA and taken by an instrument aboard the agency's Mars Reconnaissance Orbiter shows dark, narrow, 100 meter-long streaks on the surface of Mars that scientists believe were caused by flowing streams of salty water. Researchers said Monday, Sept. 28, 2015, that the latest observations strongly support the longtime theory that salt water in liquid form flows down certain Martian slopes each summer. (NASA/JPL/University of Arizona via AP)
Photo: AP This undated photo provided by NASA and taken by an instrument... Image 3 of 44
This mosaic of images from the Mast Camera (Mastcam) instrument on NASA's Curiosity Mars rover released December 9, 2013 shows a series of sedimentary deposits in the Glenelg area of Gale Crater. NASA's rover Curiosity rover tooling around on the surface of Mars has found remnants of an ancient freshwater lake that may have supported tiny life forms, scientists said Monday. There is no water left in it, but drill tests and a chemical analysis of its fine-grained rocks by the Curiosity robot's science instruments suggest microbial life could have thrived there billions of years ago.
Photo: AFP PHOTO / NASA/JPL-Caltech/MSSS This mosaic of images from the Mast Camera (Mastcam) instrument on...
Image 4 of 44 This image provided by NASA shows shows a Martian rock outcrop near the landing site of the rover Curiosity thought to be the site of an ancient streambed, next to similar rocks shown on earth. Curiosity landed in a crater near Mars' equator on Aug. 5, 2012, on a two-year mission to study whether the environment could have been favorable for microbial life. (AP Photo/NASA)
Photo: Associated Press This image provided by NASA shows shows a Martian rock outcrop near... Image 5 of 44 See more amazing images of the red planet from NASA
Photo: NASA/JPL-Caltech/MSSS See more amazing images of the red planet from NASA Image 6 of 44
Newton Crater on Mars is a large basin formed by an asteroid impact that probably occurred more than 3 billion years ago. It is approximately 287 km (178 miles) across. The picture shown here highlights the north wall of a specific, smaller crater located in the southwestern quarter of Newton Crater. The crater of interest was also formed by an impact; it is about 7 km (4.4 mi) across, which is about seven times bigger than the famous Meteor Crater in northern Arizona in North America.
The north wall of the small crater has many narrow gullies eroded into it. These are hypothesized to have been formed by flowing water and debris flows.
Photo: NASA/JPL-Caltech/MSSS Newton Crater on Mars is a large basin formed by an asteroid impact...
Image 7 of 44 This mosaic was made from images taken at infrared wavelengths in daytime and nighttime by the Thermal Emission Imaging System (THEMIS) on Mars Odyssey orbiter. The largest crater visible (left) is Sharonov Crater and is 100 kilometers (62 miles) wide.
Photo: NASA/JPL-Caltech/University Of Arizona This mosaic was made from images taken at infrared wavelengths in... Image 8 of 44 The large impact crater known as Stickney is the largest crater on the Martian moon Phobos. Some scientists believe the grooves and crater chains are related to the formation of Stickney, whereas others think they may have formed as a result of the ejecta from impacts on Mars that later collided with Phobos. The lineated textures on the walls of Stickney and other large craters are landslides formed from materials falling into the crater interiors.
Photo: NASA/JPL-Caltech/University Of Arizona The large impact crater known as Stickney is the largest crater on... Image 9 of 44 This beautiful observation shows a gorgeous pattern of dust devil tracks. Like on Earth, they often expose materials just underneath the surface, which in this case, makes for stunning patterns.
Photo: NASA/JPL-Caltech/University Of Arizona This beautiful observation shows a gorgeous pattern of dust devil... Image 10 of 44
Sand dunes are among the most widespread aeolian features present on Mars. Their spatial distribution and morphology are sensitive to subtle shifts in wind circulation patterns and wind strengths. These provide clues to the sedimentary history of the surrounding terrain.
What's fascinating about this image is the ridges running the length of the dunes here, creating the spectacular illusion that we're looking at millipedes. This is a good example of what's called "pareidolia," where we see things that really are not there.
Photo: NASA/JPL-Caltech/University Of Arizona Sand dunes are among the most widespread aeolian features present...
Image 11 of 44 This is an image of a central pit of an impact crater in the Martian ancient highlands. The central uplifts of large impact craters often collapse to form pits on Mars, but they are still structural uplifts and often expose deep bedrock with diverse rock types that have a variety of colors. This enhanced color sub-image displays colorful streaks where the bedrock is eroding, moving downhill a bit, and then getting swept by the wind.
Photo: NASA/JPL-Caltech/University Of Arizona/HI-RISE Team This is an image of a central pit of an impact crater in the... Image 12 of 44
Crystalline gray hematite (Fe2O3) was first detected on Mars using the Thermal Emission Spectrometer (TES). The landing site for the Mars Exploration Rover (MER) Opportunity was chosen at one of these hematite sites in Meridiani Planum.
After landing and driving around on the surface, scientists discovered that the hematite occurred in millimeter-size rounded particles that were concentrated along the upper surfaces of the soils.
Photo: NASA/JPL-Caltech/University Of Arizona Crystalline gray hematite (Fe2O3) was first detected on Mars using...
Image 13 of 44 Mars's seasonal polar caps are composed primarily of carbon-dioxide frost. This frost sublimates (changes from solid directly to gas) in the spring, boosting the pressure of Mars's thin atmosphere. In the fall, the carbon dioxide condenses, causing the polar caps to reach as far as ~55 degrees latitude by late winter. In the study of seasonal processes we observe the caps as they increase and decrease in size to investigate both large-scale effects on Mars as well as the local details of the sublimation and condensation processes. By learning about current processes on a local level we can learn more about how to interpret the geological record of climate changes on Mars.
Photo: NASA/JPL-Caltech/University Of Arizona Mars's seasonal polar caps are composed primarily of carbon-dioxide... Image 14 of 44
The European Space Agency's (ESA's) Mars Express obtained this view of an unnamed impact crater located on Vastitas Borealis, a broad plain that covers much of Mars's far northern latitudes. The circular patch of bright material located at the center of the crater is residual water ice. The colors are very close to natural, but the vertical relief of the topography is exaggerated three times. This patch of ice is present all year round, remaining after frozen carbon dioxide overlaying it disappears during the Martian summer.
Photo: ESA/DLR/Freie Universitat Berlin (G. Neukum) The European Space Agency's (ESA's) Mars Express obtained this view...
Image 15 of 44 Billions of years ago, floodwaters emerged from Echus Chasma on the northern side of Valles Marineris, the "Grand Canyon" of Mars. The waters then poured across the landscape as they headed for the northern lowlands, carving a giant channel named Kasei Valles. In the scene here, the floodwaters moved generally left to right, dividing and merging to erode a network of linked channels. Where the floods encountered hills and craters in their path, they often left a streamlined mesa behind the feature, pointing like a pennant downstream. False colors display the nature of the ground surface. Areas in cool tints have more fine-grain materials (such as sand and dust) at the surface, while redder tints indicate areas with harder sediments and outcrops of rock.
Photo: NASA/JPL-Caltech/University Of Arizona/HI-RISE Billions of years ago, floodwaters emerged from Echus Chasma on the... Image 16 of 44 This unnamed impact crater is about 8 kilometers in diameter and contains numerous gullies. A bright deposit was found to form on the lower slopes of one of them in recent time. Scientists questioned whether this was an indication of liquid water or dry materials (sand) flowing down the side of the crater. After analysis, the presence of liquid water in this flow event cannot be ruled out, but the available evidence is consistent with a dry granular flow.
Photo: NASA/JPL-Caltech/University Of Arizona HiRISE Science Team This unnamed impact crater is about 8 kilometers in diameter and... Image 17 of 44
This image reveals exposed layers in Noctis Labyrinthus which may contain signatures of iron bearing sulfates and phyllosilcate (clay) minerals.
This is an enhanced-color view generated from images acquired by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter (MRO).
Photo: NASA/JPL-Caltech/University Of Arizona This image reveals exposed layers in Noctis Labyrinthus which may...
Image 18 of 44
When the Mars Exploration Rover, Opportunity, landed on Meridiani Planum in January 2004, it quickly found what it had been sent from Earth to find: evidence of liquid water in the Martian past. Opportunity was targeted on Meridiani because remote sensing from orbit by the Thermal Emission Spectrometer (TES) on NASA's Mars Global Surveyor showed that portions of Meridiani contain up to 20 percent gray crystalline hematite at the surface. Hematite is an iron-oxide mineral, and on Earth the gray crystalline variety forms mostly in association with liquid water.
On the ground, Opportunity discovered the hematite lies within BB-sized spherules, dubbed "blueberries" by scientists. Blueberries that litter the surface at the landing site are embedded within outcrops of soft, layered sandstone rocks.
As geologists reconstruct it, the blueberries formed when strongly acidic groundwater drenched the basaltic sandstone, which was rich in goethite, another iron-bearing mineral. The water altered the goethite into hematite, forming spherules within the rocks. Then, over unknown ages, as the acid-rotted sandstones weathered away, the tougher spherules came free and collected on the surface.
Photo: NASA/JPL-Caltech/Arizona State University When the Mars Exploration Rover, Opportunity, landed on Meridiani...
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A towering dust devil casts a serpentine shadow over the Martian surface in this image acquired by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.
The scene is a late-spring afternoon in the Amazonis Planitia region of northern Mars. The view covers an area about four-tenths of a mile (644 meters) across. North is toward the top. The length of the dusty whirlwind's shadow indicates that the dust plume reaches more than half a mile (800 meters) in height. The plume is about 30 yards or meters in diameter.
A westerly breeze partway up the height of the dust devil produced a delicate arc in the plume. The image was taken during the time of Martian year when the planet is farthest from the sun. Just as on Earth, winds on Mars are powered by solar heating. Exposure to the sun's rays declines during this season, yet even now, dust devils act relentlessly to clean the surface of freshly deposited dust, a little at a time.
Photo: NASA/JPL-Caltech/University Of Arizona A towering dust devil casts a serpentine shadow over the Martian...
Image 20 of 44 Shortly after midnight Sunday morning (5 April 1998 12:39 AM PST), the Mars Orbiter Camera (MOC) on the Mars Global Surveyor (MGS) spacecraft successfully acquired a high resolution image of the "Face on Mars" feature in the Cydonia region.
Photo: NASA/JPL-Caltech/MSSS Shortly after midnight Sunday morning (5 April 1998 12:39 AM PST),... Image 21 of 44
The enhanced-color image taken by the microscopic imager on the Mars Exploration Rover Spirit shows the rock dubbed "Mazatzal" after a portion of its surface was brushed clean by the rover's rock abrasion tool. This image was taken at Gusev Crater.
Photo: NASA/JPL-Caltech The enhanced-color image taken by the microscopic imager on the...
Image 22 of 44
The battered region of Arabia Terra is among the oldest terrain on Mars. A dense patchwork of craters from countless impacts testifies to the landscape's ancient age, dating back billions of years.
In eastern Arabia lies an anonymous crater, 120 kilometers (75 miles) across. The floor of this crater contains a large exposure of rocky material, a field of dark sand dunes, and numerous patches of what is probably fine-grained sand. The shape of the dunes hints that prevailing winds have come from different directions over the years.
Fine-grained materials, such as dust and the smallest sand particles, heat up quickly by day and cool off equally quickly at night. However, coarser materials-bigger sand particles, gravel, hardened sediments, and rocks- respond more slowly to the same daily cycle.
This means that when THEMIS views these coarse materials late in the Martian night, they appear warmer than the pools and patches of finegrain sand. In the image here, areas that are cold at night appear in blue tints, while the warmer areas show in yellows, oranges, and reds.
Photo: NASA/JPL-Caltech/University Of Arizona/HI-RISE The battered region of Arabia Terra is among the oldest terrain on...
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What triggered a Martian landslide?
Landslides are common features in canyons on both Earth and Mars, and they happen the same way. Erosion undermines a canyon wall until abruptly millions of tons of rock come crashing down. In the case seen here, the impact of a meteorite landing near the edge of the canyon may have done more than just blast a crater 6.5 kilometers (4 miles) wide. The impact may also have triggered the massive landslide, either at the time of impact or shortly after.
Photo: NASA/JPL-Caltech/University Of Arizona/HI-RISE What triggered a Martian landslide?
Landslides are common...
Image 24 of 44
Gale Crater forms a large natural repository for much of Martian geologic history. This ancient impact scar has a diameter of about 154 kilometers (96 miles) and lies close to where the cratered highlands drop off onto the northern lowlands in Elysium. Based on its size and state of preservation, scientists estimate Gale formed over 3 billion years ago.
What draws scientific interest the most is a big mound of layered debris filling about a third of the crater's floor. Wrapping around the crater's central peak-visible at lower right in the image-the mound stands about 5.5 kilometers (3.4 miles) higher than the northern crater floor and about 4.5 kilometers (2.8 miles) above the southern floor. The mound's highest parts even rise somewhat higher than Gale's southern rim.
Photo: NASA/JPL-Caltech/University Of Arizona/HI-RISE Gale Crater forms a large natural repository for much of Martian...
Image 25 of 44 This crater, formed in 2008, exposes shallow, clean ice that is not uncommon in the middle-to-high latitudes on Mars. Sublimation, the process that occurs when a solid changes into a gas without an intermediary liquid stage, creates an ice-free layer on the surface that may be several feet deep, hiding the ice underneath until exposed by an impact.
Photo: NASA/JPL-Caltech/University Of Arizona This crater, formed in 2008, exposes shallow, clean ice that is not... Image 26 of 44 Part of a multispectral THEMIS infrared image of Nili Patera caldera on Syrtis Major has been superimposed on a high-resolution THEMIS visual image. The dacite flow (magenta) and the volcanic cone associated with it have a composition distinct from the basaltic lavas that comprise most of the caldera floor (blue). Small outliers of dacitic material lie east of the cone. Image width is 16 kilometers (10 miles).
Photo: NASA/JPL-Caltech/Arizona State University Part of a multispectral THEMIS infrared image of Nili Patera... Image 27 of 44
NASA Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings on the 1,506th through 1,510th Martian days, or sols, of Opportunity's mission on Mars (April 19-23, 2008). North is at the top.
This view is presented as a vertical projection with geometric seam correction. The site is within an alcove called "Duck Bay" in the western portion of Victoria Crater. Victoria Crater is about 800 meters (half a mile) wide. Opportunity had descended into the crater at the top of Duck Bay 7 months earlier. By the time the rover acquired this view, it had examined rock layers inside the rim.
Opportunity was headed for a closer look at the base of a promontory called "Cape Verde," the cliff at about the 2-o'clock position of this image, before leaving Victoria. The face of Cape Verde is about 6 meters (20 feet) tall. Just clockwise from Cape Verde is the main bowl of Victoria Crater, with sand dunes at the bottom. A promontory called "Cabo Frio," at the southern side of Duck Bay, stands near the 6-o'clock position of the image.
Photo: NASA/JPL-Caltech NASA Mars Exploration Rover Opportunity used its navigation camera...
Image 28 of 44
This observation shows erosional features on light-toned rocks in Aram Chaos, a crater near the equator of Mars that has been nearly filled with sedimentary rocks. In enhanced color, the sediments are very distinctive. The rocks show a sharp change in color partway down the slope, indicating a change in the properties of the rock, probably to a different composition.
The erosional features have alcoves with aprons downslope, and in some cases have hints of channels, potentially due to abrasion by falling debris. These morphologies bear some resemblance to gullies commonly found in the mid-latitudes, which are often thought to have formed due to erosion by liquid water from melting snow. Near the equator, however, snowmelt in Mars' recent climate is less likely.
Photo: NASA/JPL-Caltech/University Of Arizona This observation shows erosional features on light-toned rocks in...
Image 29 of 44 This mosaic was acquired on Sol 36 (February 8, 2004) by the Spirit rover's panoramic camera (Pancam). Spirit performed measurements on a rock called "Adirondack," which is visible at the top of this mosaic. This false color image brings out subtle color differences in the scene.
Photo: NASA/JPL-Caltech/Cornell This mosaic was acquired on Sol 36 (February 8, 2004) by the Spirit... Image 30 of 44 This image shows two small tributaries, just east of where they join Shalbatana Vallis.
Photo: NASA/JPL-Caltech/Arizona State University This image shows two small tributaries, just east of where they... Image 31 of 44
This mosaic image of Valles Marineris - colored to resemble the martian surface - comes from the Thermal Emission Imaging System (THEMIS), a visible-light and infrared-sensing camera on NASA's Mars OdyssGeologists think Valles Marineris began to open along geological faults about 3.5 billion years ago. The faulting was caused by the tectonic activity that accompanied the growth of the giant volcanoes in Tharsis, lying just to the west. As molten rock (magma) pushed into Tharsis from below, the entire region rose, and the surrounding crustal rocks stretched and broke into faults and fractures.
As cracks opened, the ground sank, much as the keystone in an arch drops when the ends of the arch move apart. The faulting also opened paths for subsurface water to escape, undermining the ground and enlarging the fracture zone. In countless places, the valley's steep, newly exposed walls became unstable, causing landslides that widened the canyon further. It's not clear when the valley's growth stopped - and in places even today small landslides undoubtedly occur. But it appears the main activity came to a halt roughly 2 billion years ago.
Photo: NASA/JPL-Caltech/Arizona State University Ey Orbiter. This mosaic image of Valles Marineris - colored to resemble the...
Image 32 of 44 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image portrays a plethora of dark streaks created by passing dust devils during early summer in the martian southern hemisphere. The picture covers an area about 3 km (1.9 mi) wide near 40.2°S, 237.7°W. Sunlight illuminates the scene from the upper left.
Photo: NASA/JPL-Caltech/Malin Space Science Systems This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image... Image 33 of 44 This picture was taken during the Martian summer with only small patches of ice remaining at the surface; they show up as bright, somewhat blue, spots on slopes that provide some shading from the Sun. Geologists would classify these dunes as "sand-starved" because the ground between the dunes has almost no sand. This surface shows a pattern of cracks that is typical of the permafrost's seasonal expansion and contraction. It is also possible that this subsurface ice exists inside the dunes. If so, the dunes are not currently moving and are being "stabilized" by this ice.
Photo: NASA/JPL-Caltech/University Of Arizona This picture was taken during the Martian summer with only small... Image 34 of 44
From a distance, the floor of this crater looks like a giant honeycomb or spider web. The intersecting shapes, or polygons, commonly occur in the northern lowlands of Mars. The polygons in this "patterned ground" are easy to see because their edges are bound by troughs or ridges covered by bright frost relative to their darker, frost-free interiors. Patterned ground on Mars is thought to form as the result of cyclic thermal contraction cracking in the permanently frozen ground.
Scientists study polygonally-patterned ground on Mars because the occurrence and physical characteristics of the polygons helps us understand the recent and past distribution of ice (frozen water) in the shallow subsurface. These features also provide clues about climate conditions.
Photo: NASA/JPL-Caltech/University Of Arizona From a distance, the floor of this crater looks like a giant...
Image 35 of 44 Fans and ribbons of dark sand dunes creep across the floor of Bunge Crater in response to winds blowing from the direction at the top of the picture. The frame is about 14 kilometers (9 miles) wide. This image was taken in January 2006 by the Thermal Emission Imaging System instrument on NASA's Mars Odyssey orbiter and posted in a special December 2010 set marking the occasion of Odyssey becoming the longest-working Mars spacecraft in history. The pictured location on Mars is 33.8 degrees south latitude, 311.4 degrees east longitude.
Photo: NASA/JPL-Caltech/Arizona State University Fans and ribbons of dark sand dunes creep across the floor of Bunge... Image 36 of 44
This is a small volcano superimposed on the flanks of a larger one of the Cerberus Tholi.
This smaller feature has a single vent opening, aligned along a Cerberus Fossae trough, and it has lava flows radiating away from this vent in all directions, resembling a flower. These flows appear somewhat darker than their surroundings, though this might be due to roughness as much as to the flow’s relative youth. Note that there are some small impact craters superimposed on this feature, indicating that these flows are not entirely young.
Photo: NASA/JPL-Caltech/University Of Arizona This is a small volcano superimposed on the flanks of a larger one...
Image 37 of 44 On May 19th, 2005, NASA's Mars Exploration Rover Spirit captured this stunning view as the Sun sank below the rim of Gusev crater on Mars.
Photo: NASA/JPL-Caltech/Texas A&M/Cornell On May 19th, 2005, NASA's Mars Exploration Rover Spirit captured... Image 38 of 44
NASA's Mars Exploration Rover Spirit acquired this false-color image on Mars during the rover's 746th Martian day, or sol, after using the rock abrasion tool to brush the surfaces of rock targets informally named "Stars" (left) and "Crawfords" (right). Small streaks of dust extend for several centimeters behind the small rock chips and pebbles in the dusty, red soils. Because the rover was looking southwest when this image was taken, the wind streaks indicate that the dominant wind direction was from the southeast.
Stars and Crawfords are on a rock outcrop located on top of "Home Plate." The outcrop is informally named "James 'Cool Papa' Bell," after a Negro League Baseball Hall of Famer who played for both the Pittsburgh Crawfords and the Kansas City Stars. To some science team members, the two brushed spots resemble the eyes of a face, with rocks below and between the eyes as a nose and layered rocks at the bottom of the image as a mouth.
Photo: NASA/JPL-Caltech/USGS/Cornell University NASA's Mars Exploration Rover Spirit acquired this false-color...
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Dunes are often found on crater floors. In the winter, at high northern latitudes, the terrain is covered by carbon-dioxide ice (dry ice). In the spring, as this seasonal ice sublimes, many unusual features unique to Mars are visible.
On the floor of this crater where there are no dunes, the ice forms an uninterrupted layer. On the dunes, however, dark streaks form as surface material from below the ice is mobilized and deposited on top of the ice. In some cases this mobile material probably slides down the steep face of the dune, while in other cases it may be literally blown out in a process of gas release-similar to removing a cork from a champagne bottle.
Photo: NASA/JPL-Caltech/University Of Arizona Dunes are often found on crater floors. In the winter, at high...
Image 40 of 44 NASA's Mars Exploration Rover Opportunity used its panoramic camera to record this eastward horizon view on the 2,407th Martian day, or sol, of the rover's work on Mars (October 31, 2010). The view is presented in false color to make differences in surface materials more visible. A portion of Endeavour Crater's eastern rim, nearly 30 kilometers (19 miles) in the distance, is visible over the Meridiani Planum.
Photo: NASA/JPL-Caltech/Cornell NASA's Mars Exploration Rover Opportunity used its panoramic camera... Image 41 of 44
On the southwest edge of the immense volcanic region of Tharsis, lava from its giant volcanoes flowed down to meet the old cratered landscape of Terra Sirenum. Scientists cannot say how many years separate the flows from the terrain they engulfed, but the relationship between the two tells a complex tale. This false-color mosaic image combines separate frames taken by the Thermal Emission Imaging System (THEMIS), a special camera on NASA's Mars Odyssey
Photo: NASA/JPL-Caltech/University Of Arizona On the southwest edge of the immense volcanic region of Tharsis,...
Image 42 of 44 A false-color mosaic focuses on one junction in Noctis Labyrinthus where Mars canyons meet to form a depression 4,000 meters (13,000 feet) deep.
Photo: NASA/JPL-Caltech/University Of Arizona A false-color mosaic focuses on one junction in Noctis Labyrinthus... Image 43 of 44
This observation shows a portion of the wall (light-toned material) and floor of a trough in the Acheron Fossae region of Mars. Many dark and light-toned slope streaks are visible on the wall of the trough surrounded by dunes. Slope streak formation is among the few known processes currently active on Mars. While the mechanism of formation and triggering is debated, they are most commonly believed to form by downslope movement of extremely dry sand or very fine-grained dust in an almost fluidlike manner (analogous to a terrestrial snow avalanche) exposing darker underlying material.
Some of the slope streaks show evidence that downslope movement is being diverted around obstacles, such as large boulders, and a few appear to originate at boulders or clumps of rocky material. These slope streaks, as well as others on the planet, do not have deposits of displaced material at their downslope ends. The darkest slope streaks are youngest and can be seen to cross cut and lie on top of the older and lighter-toned streaks. The lighter-toned streaks are believed to be dark streaks that are lightening with time as new dust is deposited on their surface.
Photo: NASA/JPL-Caltech/University Of Arizona This observation shows a portion of the wall (light-toned material)...
Image 44 of 44 Life on Mars? NASA says planet appears to have flowing water 1 / 44 Back to Gallery CAPE CANAVERAL, Fla. (AP) — Mars appears to be flowing with rivulets of salty water, at least in the summer, scientists reported Monday in a finding that boosts the odds of life on the red planet.
"It suggests that it would be possible for there to be life today on Mars," NASA's science mission chief, John Grunsfeld , said at a news conference.
Scientists in 2008 confirmed the existence of frozen water on Mars. Now instruments aboard NASA's Mars Reconnaissance Orbiter have yielded the strongest evidence yet that salt water in liquid form trickles down certain Martian slopes each summer, according to the researchers.
Related Stories Stargazers witness rare event in supermoon eclipse Latest Pluto photos show a cryptic, scaly planet NASA shares massive Martian panorama on anniversary of latest landing "Mars is not the dry, arid planet that we thought of in the past," said Jim Green , director of planetary science for NASA. "Under certain circumstances, liquid water has been found on Mars."
The rivulets — if that's what they are, since the evidence for their existence is indirect — are about 12 to 15 feet wide and 300 feet or more long, scientists said.
"What we're dealing with is wet soil, thin layers of wet soil, not standing water," said Alfred McEwen of the University of Arizona at Tucson, the principal scientist for the Mars Reconnaissance Orbiter's high-resolution imaging experiment.
Because liquid water is essential to life, the findings could have major implications for the possibility of Martian life. The researchers said in the journal Nature Geoscience that further exploration is warranted to determine whether microscopic life exists on the planet.
McEwen said he, for one, believes the possibility of life on Mars to be "very high," though it would be microbial and somewhere in the Martian crust.
The presence of liquid water could also make life easier for astronauts visiting or living on Mars. Water could be used for drinking and for creating oxygen and rocket fuel. NASA's goal is to send humans there in the 2030s.
The evidence of flowing water consists largely of dark, narrow streaks on the surface that tend to appear and grow during the warmest Martian months and fade the rest of the year.
Mars is extremely cold even in summer, and the streaks are in places where the temperature is as low as minus-10 degrees Fahrenheit. But salt can lower the freezing point of water and melt ice.
The source of the water is a mystery. Scientists noted it could be melting ice, an underground aquifer, water vapor from the thin Martian atmosphere, or some combination.
McEwen said that there appears to be a "significant volume" of water, speculating it could fill many Olympic swimming pools, but that it is spread thin.
The streaks were spotted by the orbiter's high-resolution, telescopic camera. Another on-board instrument detected the chemical signature of salt compounds combined with water.
Michael Meyer , lead scientist for NASA's Mars exploration program, said the only definitive way for now to determine whether there's life on Mars is to collect rocks and soil for analysis on Earth — something a U.S. lander set to lift off in 2020 will do.
Now that scientists know what they're looking for, a better, more methodical search can be carried out, Green said.
"Water is one of the most precious resources necessary for a human mission to the red planet," said Rep. Lamar Smith , R-Texas, chairman of the House science, space and technology committee. "The more evidence we find of it, the more encouraged I am for future Mars missions."
Present-day Mars is nothing like ancient Mars. Three billion years ago and more, our most Earthlike neighbor had a huge ocean, but something radical happened, and exactly what remains a mystery.
The idea of water — and life — on Mars has been irresistible to earthlings for generations.
In 1877, Italian astronomer Giovanni Schiaparelli spied what he called "canali" on Mars — Italian for "channels" — but the word was mistranslated to "canals" in English, causing imaginations to run wild. In the early 1900s, amateur astronomer Percival Lowell claimed to have spotted irrigation canals and theorized they were built by Martians.
In 2008, NASA's Phoenix spacecraft landed on Mars and confirmed the long-suspected presence of ice in the soil. The Mars Reconnaissance Orbiter has been circling the planet since 2006.
The lead author of the research paper, Lujendra Ojha, is a Ph.D. candidate at Georgia Institute of Technology .
For NASA, at least, the timing couldn't be better. This Friday, the NASA-approved movie "The Martian" has its premiere.