A set of dark sand dunes within the northeastern edge of a dune field in Nili Patera, a volcanic caldera in the Syrtis Major region of Mars is the focus of this HiRISE observation.

The lighter surface beneath the dunes is an ancient lava flow. The cracks in the flow probably formed when the lava cooled. Many of the cracks are dark and probably contain sand; the dark color of the dunes suggests that the sand is basaltic in composition and therefore originally derived from volcanic rock.

However, whether the sand formed from Nili Patera is not known, as it is possible the dunes have blown in from a more distal location. With two horns on one end and a rounded edge on the other, the dunes have a distinctive shape. The side of the dunes with the horns has a steeper slope — called the slip face — and the rounded side exhibits a more shallow slope. These types of dunes are called “barchans” and, in analogy with similar dunes on Earth, form in areas with limited sand supply.

The horns of the barchans point in the downwind direction, indicating that the predominant surface winds in this region blew from the east-northeast (slightly upper right in the image). Zooming into the image, one can see landslides on many dune slip faces, indicating fairy recent slope failure. Very small ripples are visible on the dunes” surfaces, showing that the winds in this region have not only blown the barchans across the lava plain, but also modified the dunes themselves. Another HiRISE image, PSP_004339_1890, shows more barchan dunes in Nili Patera, south of this area.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

The University of Arizona press release is reproduced below:

By Lori Stiles, University Communications
January 23, 2008

Mars has an ethereal, tenuous atmosphere at less than 1 percent the surface pressure of Earth, so scientists working on The University of Arizona's High Resolution Imaging Experiment, or HiRISE, are challenged to explain the complex, wind-sculpted landforms they're now seeing in unprecedented detail.


The HiRISE camera took this picture of a dune field within a
crater southwest of Hershel Crater on July 1, 2007. The orbiter
was flying 175 miles above the planet at the time.
(NASA/JPL/University of Arizona)

The HiRISE camera on NASA's Mars Reconnaissance Orbiter, the most powerful camera to orbit another planet, can see 20-inch-diameter features while flying at about 7,500 mph between 155 and 196 miles above the Martian surface. HiRISE is giving researchers eye-opening new views of wind-driven Mars geology.

One of the main questions has been if winds on present-day Mars are strong enough to form and change geological features, or if wind-constructed formations were made in the past, perhaps when wind speeds and atmospheric pressures were higher, HiRISE team members say.


The HiRISE camera found this region of Schiaparelli Basin
near the Martian equator that is a perfect tablet for the
scribblings of dust devils. Martian dust devil plumes can be
gargantuan - with a height of up to nine kilometers.
(NASA/JPL/University of Arizona)

"We're seeing what look like smaller sand bedforms on the tops of larger dunes, and, when we zoom in more, a third set of bedforms topping those," HiRISE co-investigator Nathan Bridges of the Jet Propulsion Laboratory in Pasadena, Calif., said. "On Earth, small bedforms can form and change on time scales as short as a day."

There are two kinds of "bedforms," or wind-deposited landforms. They can be sand dunes, which are typically larger and have distinct shapes. Or they can be ripples, which is sand mixed with coarser, millimeter-sized particles. Ripples are typically smaller, more linear structures.

HiRISE also shows detail in sediments deposited by winds on the lee side of rocks. Such rock "windtails" show which way the most current winds have blown, Bridges said. Such features have been seen before, but only by rovers and landers, never an orbiting camera. Researchers can now use HiRISE images to infer wind directions over the entire planet.

Scientists discovered miles-long, wind-scoured ridges called "yardangs" with the first Mars orbiter, Mariner 9, in the early 1970s, Bridges said. New HiRISE images reveal surface texture and fine-scale features that are giving scientists insight on how yardangs form.

"HiRISE is showing us just how interesting layers in yardangs are," Bridges said. "For example, we see one layer that appears to have rocks in it. You can actually see rocks in the layer, and if you look downslope, you can see rocks that we think have eroded out from that rocky layer above."

HiRISE shows that some layers in the yardangs are made of softer materials that have been modified by wind, he added. The soft material could be volcanic ash deposits, or the dried up remnants of what once were mixtures of ice and dust, or something else.

"The fact that we see layers that appear to be rocky and layers that are obviously soft says that the process that formed yardangs is no simple process but a complicated sequence of processes," Bridges said.

Scientists since the 1970s Viking missions have puzzled over what appears to be dust covering Mars' 6-to-13-mile-high volcanoes. Near the volcanic summits, the air is about one one-thousandth of Earth's atmospheric pressure.

"HiRISE keeps showing interesting things about terrains that I expected to be uninteresting," said HiRISE principal investigator Alfred McEwen of the UA's Lunar and Planetary Laboratory. "I was surprised by the diversity of morphology of the thick dust mantles. Instead of a uniform blanket of smooth dust, there are often intricate patterns due to the action of the wind and perhaps light cementation from atmospheric volatiles."

HiRISE images show that what covers the slopes of the high Martian volcanoes are definitely dunes or ripples that appear to have an organized 'reticulate' structure possibly formed by winds blowing from multiple directions, Bridges said.

"On Earth, winds blowing from many different directions form what are called 'star dunes,' and these look somewhat like those," Bridges said. "The reticulate surface looks like a network of connected wind-blown dunes and ripples.

"The fact that the air pressure near the volcano tops is so low and the material is dust challenges us to understand what these features are," he said. "Perhaps the dust is clumping together and making sand-size material. But how this stuff can be blown around this low pressure is at the edge of our understanding of aeolian physics.

"Possibly the bedforms on the volcanoes formed under a different Martian climate in the past, when atmospheric density was greater," Bridges said. "But I'm not sure that's the case, because you can see evidence that a lot of the mantle appears to be fairly recent."

HiRISE team member Paul Geissler of the U.S. Geological Survey, in Flagstaff, Ariz., has discovered from HiRISE images that dark streaks coming from Victoria Crater are probably streaks of dark sand blown out from the crater onto the surface. Scientists had wondered if wind might have blown away lighter-colored surface material, exposing a darker underlying surface. Geissler, a member of the Mars Exploration Rover team, is comparing HiRISE images with images the Opportunity rover has taken at Victoria Crater.

Bridges is lead author on the paper titled "Windy Mars: A dynamic planet as seen by the HiRISE camera" in the Geophysical Research letters in December. McEwen is among the paper's co-authors.

Information about the Mars Reconnaissance Orbiter spacecraft is online at http://www.nasa.gov/mro. The mission is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, for the NASA Science Mission Directorate. Lockheed Martin Space Systems, based in Denver, is the prime contractor and built the spacecraft. Ball Aerospace and Technologies Corp., of Boulder, Colo., built the HiRISE camera operated by the UA.

Source: UA Press Release

The Hellas Montes are a group of mountains along the western rim of the giant Hellas Basin on Mars.

The Hellas Basin is the largest of the obvious impact craters on the Red Planet. It is very ancient and has been partially filled by sediments. The Hellas Montes are part of the eroded crater rim.

In the central part of this HiRISE image, we can see steep slopes where landslides have exposed a variety of rocks. The jumble of blocks, rather than stacks of layered sediments or lavas, is consistent with impact crater ejecta. On flatter slopes, the ground is covered with a mantling deposit that is generally considered to be ice-rich dust.

In the southern part of the image, a large circular depression—rimmed by a zone with many large boulders—is visible. This is an impact crater with a relatively thin mantling deposit on its rim.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

SUBIMAGES IN THIS OBSERVATION


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This image gives a rare glimpse of an area in the far south of Mars that is frequently obscured by clouds or covered by surface frosts.

Crescent-shaped sand dunes can be seen scattered across patterned ground. The surface patterns are made up of channels carved by carbon dioxide gas as it escapes from under the seasonal frost. The dunes were still partially frozen when this picture was taken during the vernal equinox, as the Sun moved into the northern hemisphere at the end of the southern summer. Bluish ice is visible on the steep faces of the dunes and along their bases.

Typical sand dunes on Earth and Mars gradually move downwind as sand accumulates on the upwind (convex) side and then avalanches down the steeper down-wind side, called the “slip face”. Here, the sand motion appears to be around the dunes instead. Clean patches of ground downwind of the dunes show that the surface is sheltered by the dunes, which prevent dark sand from being deposited in their lees.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

This observation shows part of a large region of layered rocks in Terby Crater, in the southern highlands of Mars. The layers show variation in thickness, brightness, and color, suggesting a diverse history.

Sedimentary rocks on Mars are often relatively light-toned. At this site both light and dark materials are visible. Light outcrops are exposed in many places, particularly in the sides of the large mesas (flat-topped hills) in this area. Light and dark layers alternate at some levels. In several places the mesas are capped by darker rock that is breaking into boulders; these layers are probably relatively strong and resistant, and help armor the mesa against erosion.

There is also a widespread, relatively dark layer that appears to mantle much of the area and drape some of the steeper slopes. This unit is relatively young and unconsolidated. It must have been deposited after most of the erosion here had occurred since it drapes the slopes, and the patchy nature suggests that it erodes relatively easily.

In many cases it is hard to determine the nature of the layers; deposits from lakes, rivers, sand dunes, or volcanic ash can form layered deposits. It is possible that several processes have contributed to the rocks here. However, one area suggests past fluvial (stream or river) deposition.

Near the center of the image, there is a region of long, sinuous ridges, once buried and now exposed by erosion. These may be old stream beds, which can turn into ridges if the bed material is coarser or better-cemented than the rocks around it.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

This image shows high latitude terrain near the Sisyphi Montes. Patterned ground is everywhere throughout the scene, and there are several muted craters that have relaxed over time due to the presence of ground ice.

Dark splotches are also common. Using full HiRISE resolution, the dark splotches exist around boulders. It is possible that the boulders are ejecta from the freshest crater in the scene, the small crater near the top of the image. They could also be from another impact crater not in this image or be a result of a periglacial stone sorting process that leaves the large boulders isolated.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

This image shows polar pit gullies in a depression. The gullies do not appear to have been active recently, as their channels and alcoves are covered with polygonal fractures and ripples that have formed over time. The alcoves contain boulders from eroding layers up-slope. Several of the alcoves extend to the slope rim, suggesting head-ward erosion.

The rest of the scene contains abundant polygonal ground, thought to have formed by processes involving ground ice. This image is at a high latitude where polygonal terrain is common. This feature is not found in equatorial regions, which supports a relationship with ground ice because ground ice is not stable near the equator today.

There are several muted circles on the plains in the lower half of the image; these are possibly relaxed craters. If a crater forms in ice-rich ground, the ice enhances the degradation of the crater and gives the crater a “softened” appearance.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

The THEMIS instrument onboard the Mars Odyssey spacecraft identified a possible salt deposit in this area, based on the infrared colors of the ground. Salt deposits typically form when water evaporates, suggesting that this might have once been an area favorable for life on Mars.

The possible salt deposit is the slightly lighter-colored area in the center of the image. The light-colored material is found peeking out from underneath sand dunes between small ridges and knobs of more tan colored material in the enhanced color data. This suggests that the (possibly) salty layer was buried by other materials and then exposed by erosion.

This layer also exhibits a fracture pattern similar to clay-rich materials visible elsewhere on Mars. It is interesting that this layer is also relatively devoid of boulders, suggesting that it is made up of some weak material.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

The Nili Fossae are valleys that have cut into the ancient crust of Mars, exposing clay minerals. These minerals formed in the presence of water and may be the result of chemical reactions between hot water and rocks. If so, this could have been a favorable location for Martian life in ancient times.

This HiRISE image is part of a series in search for a safe place the Mars Science Laboratory rover can land. In the central part of the image, the terrain is a mix of sand dunes and relatively smooth rock exposures. There are some small knobs but very few large rocks in the area. Instead, the multi-colored rock exposures seem to be mostly a mosaic of flat fractured rock.

On the southern edge of the image, an impact crater is a potential hazard. In the northern part of the image, the scarp marking the boundary of the valley is visible.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

The Bosporos Montes make up part of the rim of the giant Argyre impact basin on Mars. The Compact Reconnaissance Imaging Spectrometer (CRISM) identified this as a location with clay minerals. Such minerals contain water and may have formed under conditions favorable for life.

This HiRISE image was taken to support the CRISM Team’s investigation of this area. While HiRISE does not have the ability to identify minerals the way CRISM can, the enhanced colors in this image are similar to those seen in other clay-containing parts of Mars.

The light-toned mesas and plains are crisscrossed with small fractures that could have formed as a muddy clay deposit dried. However, this material is strong enough to form boulders where it has been hit by impact craters.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

Mawrth Vallis contains clay minerals that formed by chemical alteration of rocks by water. It is one of the short list of potential sites that the Mars Science Laboratory rover will land at, and the HiRISE team is working to find a safe place to land in this area.

This observation shows a wide variety of scientifically interesting terrains as well as some potential hazards for landing. The central part of the image is dominated by light-toned materials with curving fractures of many different sizes. These fractures do not have a preferred orientation, indicating that they did not form in response to some regional stress pattern.

Instead, they formed by some more uniform process, possibly the drying of a thick mud deposit or the gradual rebound of the area as the overlying material was eroded away. The scattered mounds and sand dunes may or may not prove to be a danger, but it is reassuring to see that many of the impact craters have been smoothed out with a filling of wind-blown sand.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

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Named after a 19th century French astronomer, Henry Crater is a 165 kilometer (103 mile) diameter impact crater, located in Arabia Terra on a portion of the Martian highlands extending into the northern hemisphere. This observation shows multiple layers on the edge of a mound on the floor of the crater, which is distinct from others in the immediate vicinity.

The layers represent the eroded remains of sedimentary rocks that formed from sediments deposited within the crater sometime after its formation. The origin of the sediments on the crater floor in not known but may be windblown dust and sand. The layers exhibit differences in degrees of hardness and resistance to erosion with resistant layers forming cliffs and more easily eroded layers forming ledges.

Several dark streaks are visible on slopes (see subimage). Slope streak formation is among the few known processes currently active on Mars. Streaks are believed to form by downslope movement of dust in an almost fluid-like manner (analogous to a terrestrial snow avalanche) either exposing darker underlying material or creating a darker surface by increasing its roughness.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

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Two distinctly different terrain types are visible in this image of the northern lowlands of Mars.

An older, heavily cratered landscape has been inundated by much younger flows. The valley floors are filled with flows that have relatively smooth surfaces and very few superposed impact craters.

In contrast, the mesas and hills making up the older terrain have blocky surfaces, perhaps fragmented by ancient impacts. The smooth surfaces of the flows are punctuated by curved, subparallel fractures oriented transverse to the flow direction. These cracks resemble crevasses in terrestrial glaciers and were formed when the brittle solid crust of the flow fractured as it was dragged downstream. Detailed images such as this will help determine the role ice may have played in these flows.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

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Sand dunes are among the most prominent wind-formed features found on Mars. Their morphologies depend on the winds and also on the local supply of sand grains, so they provide clues to the nature of both the Martian atmosphere and surface.

Dunes form through the accumulation of coarse sand grains carried by the wind by means of saltation, or bouncing along the surface. Monitoring the present day dune activity can help determine the timescale over which Martian rocks are eroded, as the impacting grains sandblast the surface over time. The sands of Mars must be continually replenished as the coarse grains are ground into fine dust by repeated impacts. Finding the hidden sources of fresh sand is a challenge for HiRISE.

This image was targeted at a point in Mitchell Crater in the southern highlands of Mars where sands abruptly appear and spread north. The sands seem to derive from the edge of an eroding mesa (shown here with an arrow; 8.66 kilometer, or 5.4 miles across). A close-up view of the terrain nearby suggests that boulders and sand have been excavated by erosion from beneath brighter, polygonally fractured ground (1.45 km, or 0.9 mi across).

This rocky layer may originally have been a lava flow; Martian lava flows are predominantly composed of basalt, which would account for the dark color of the sand. The polygonal pattern of the bright upper layer may be due to repeated freezing and thawing of the soil that buries the lava flow. The tracks of dust-devils are clearly visible on the smooth, sandy surface but largely vanish when they cross into the polygonally fractured terrain.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

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This observation shows part of the floor of a large impact crater in Arabia Terra. This crater formed in the distant past when a large asteroid or comet struck Mars, and has been heavily modified since formation. The crater was partially filled by sediments, forming the rock outcrops and layers visible in this image.

After this material was laid down, part of the deposits were eroded away. The central part of the image has been carved especially deeply, forming a distinct depression.

This depression has been a site of aeolian (wind) transport of sand in more recent times. A particularly interesting aspect of this site is that there appears to have been multiple styles of aeolian activity. Both large sand dunes (the dark hills, deep blue in the color image) and smaller ripples (sharp, light-toned narrow ridges) are visible. While ripples are often found in association with dunes, the different colors suggest that the material is not the same. (At full resolution, the surfaces of both the dunes and the large ripples are covered with much smaller ripples.)

Even where the ripples and dunes are in contact, there is a distinct contrast between the materials. In the subimage, dark sand appears to fill a trough between two large light ripples, suggesting that the dark sand has moved more recently. This could be due to different grain sizes, since certain sizes are most easily lifted by the wind.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

This observation shows a portion of Aurorae Chaos, chaotic terrain east of the Vallis Marineris canyon system. Aurorae Chaos extends from Capri and Eos Chasmata on the west into Hydraotes and Aureum Chaos on the north and east.

Chaotic terrain is thought to form from subsurface collapse following volatile release. It is possible that the Martian crust was at one time enriched in ices that became gases or liquid at relatively low temperatures upon encountering a heat source or was violently shaken. These ices existed in spaces between soil particles. If a large volume of volatiles is suddenly released, then there is a large portion of the soil volume missing. The soil cannot support itself, so it collapses.

Since chaotic terrain is often located at the head of the Martian outflow channels (giant flood plains), it is also possible that the chaotic regions are the source of the fluids that formed the outflow channels. Aurorae Chaos connects to outflow channels via other chaotic regions.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

Release date Feb 5, 2008
Latitude: 5.00 S
Longitude: 270.30 E




This image of layered deposits in Tithonium Chasma was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) at 1537 UTC (11:37 a.m. EDT) on August 31, 2007, near 5.0 degrees south latitude, 270.3 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 20 meters (66 feet) across. The region covered is just over 8.5 kilometers (5.3 miles) wide at its narrowest point.

Tithonium Chasma lies at the western end of the Valles Marineris canyon system. It extends approximately east-west for roughly 810 kilometers (503 miles), varies in width from approximately 10 to 110 kilometers (6 to 68 miles), and cuts into the Martian surface to a maximum depth of roughly 6 kilometers (4 miles). Many of the canyon-forming processes found on Mars are readily illustrated in Tithonium Chasma. These features offer a window into the geologic history of the planet.

Landslides have enlarged the canyon’s walls and formed debris deposits that ring the trough’s interior. The chasma’s floor is composed of layered deposits which may be volcanic or sedimentary in origin. One of CRISM’s tasks is to determine the mineralogy of these deposits.

The top panel in the montage above shows the location of the CRISM image on a mosaic taken by the Mars Odyssey spacecraft’s Thermal Emission Imaging System (THEMIS). The CRISM data covers an eroded terrace of these interior layered deposits, and is centered along the edge of a knob of eroded wall material just to the southwest.

The lower two images are renderings of data draped over topography without vertical exaggeration. These images provide a view of the knob’s elevation relative to the surrounding terrain. The lower left image is in infrared false color, and shows light-colored material exposed on the flanks of the layered deposits. The upper right image shows measures of the strengths of different mineral signatures in the red, green, and blue image planes, and reveals diversity in the mineral content of this light-colored material. Some areas have no signature in the data, indicating dust-like spectral properties, while other areas have signatures of monohydrated or polyhydrated sulfate. This signifies a variety of compositions within these layered deposit.

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad.
CRISM's mission: Find the spectral fingerprints of aqueous and hydrothermal deposits and map the geology, composition and stratigraphy of surface features. The instrument will also watch the seasonal variations in Martian dust and ice aerosols, and water content in surface materials — leading to new understanding of the climate.

Credit: NASA/JPL/JHUAPL/ASU

Source: CRISM

Terby Crater was suggested as a possible landing site for the Mars Science Laboratory rover mission. It is a large crater blasted into the northern rim of the gargantuan Hellas Basin. Both of these holes in the crust of Mars were formed by impacts with asteroids or comets early in the planet’s geologic history.

Large impacts excavate material from deep within the crust, allowing a rover to access rocks that otherwise would require a massive drilling rig. Since the interior of Mars is warm enough for liquid water, these rocks are of great interest in the search for possible ancient life on the Red Planet.

As this HiRISE image shows, Terby Crater is interesting for additional reasons. The curving ridges most prominent near the center of the image look like stream channels. However, unlike normal channels, the interior is higher than the surroundings. One way features like this form on Earth is called “topographic inversion.” Stream beds can become lined with larger gravels or cobbles, making them quite resistant to erosion, so with time, the surroundings are removed and the originally low channel is left standing high (and dry).

Another way similar features form is when a stream is flowing underneath a glacier. In this case the liquid water is confined by ice on either side and the sediments can build up. When the ice is removed, a ridge of these sediments is left behind. These are called “eskers” by geologists. While further examination of this and similar HiRISE images may be able to distinguish between these possibilities, a rover would allow more detailed studies.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

This image was taken in support of imaging by the Context (CTX) camera onboard the Mars Reconnaissance Orbiter and is an example of how the different instruments cooperate. Trumpler Crater is in the far southern part of the Martian highlands.

This HiRISE image shows a frozen terrain typical at these latitudes. The surface is mantled by a deposit that is postulated to be largely a mix of dust and ice. However, many of the higher hills have had this mantle removed and the older rocks are exposed. In some parts of Mars there is good evidence for ice having flowed from higher to lower ground, but there is no such evidence here. Perhaps the mantling deposit never formed on the tops of these hills or it was preferentially removed from these places.

In the flatter locations, the mantling deposit is completely covered by small cracks that form a polygonal network. These are clearest in the southern part of the image, where the sun is almost parallel to the surface, producing dramatic shadows. Such polygons are a common feature in permafrost.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

Olympus Mons is the largest volcano in the Solar System and is thought to have been active in the relatively recent past (which on Mars means many millions of years ago). While this towering giant gets a lot of the attention, it is surrounded by a vast field of other volcanic features. This HiRISE image takes a close look at one set of intriguing landforms: small cones.

Cones similar to these are found atop the freshest lava flows on Mars in Athabasca Valles. In that location, HiRISE found proof that they formed by steam exploding through the lava flow. The steam was produced by boiling water (or ice) in the ground underneath the lava flow. Could the same thing have happened here?

Unfortunately, HiRISE finds that this area north of Olympus Mons is covered in a thick layer of dust. While the wonderful resolution of HiRISE reveals details of the ripples in the dust, it cannot show us what is underneath the dust. Therefore we cannot prove that these cones formed the same was as the Athabasca Valles cones. They could be small volcanic vents, but it is unlikely that so many small eruptions would have taken place so close together.

However, since we cannot show that the ground under the dust is lava, we cannot rule out non-volcanic processes. Still, the similarity in the shapes and sizes of these cones to the ones in Athabasca Valles leaves open the possibility that water and lava interacted explosively here.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

This observation shows a wrinkle ridge in Solis Planum, located in the Thaumasia region of Mars, a high-elevation volcanic plain located south of the Valles Marineris canyon system and east of the Tharsis volcanic complex. Solis Planum contains some of the most distinct and well studied arrays of wrinkle ridges on Mars.

Wrinkle ridges are long, winding topographic highs and are often characterized by a broad arch topped with a crenulated ridge. These features have been identified on many other planetary bodies such as the Moon, Mercury, and Venus. On Mars, they are many tens to hundreds of kilometers long, tens of kilometers wide, and have a relief of a few hundred meters. Wrinkle ridges are most commonly believed to form from horizontal compression or shortening of the crust due to faulting and are often located in volcanic plains. They commonly have asymmetrical cross sectional profiles and an offset in elevation on either side of the ridge. Large dunes are also visible bordering the wrinkle ridge.

The reddish colors seen in this image most likely indicate the presence of dust (or indurated dust) and the darker, bluish colors most likely indicate the presence of larger rocks and boulders on the wrinkle ridge.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

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Steve Halla’s class at Leap Academy Charter High School in Camden, NJ, suggested this image, a region near the intersection of Elysium Chasma and Hyblaeus Chasma. The class suggested that seeing a cross-section of Hyblaeus Chasma in the walls of Elysium Chasma might shed light on the mechanism(s) that formed it.

A cross-section of Hyblaeu Chasma is visible in the first subimage. The chasm seems to be filled with a resistant light-toned layer, about 200 meters thick (likely consisting of cemented windblown sand and dust) forming a mantling unit and overlying more resistant boulder-rich layers. The sand and dust was likely blown into Hyblaeu Chasma after it was formed by tectonic processes, possibly in combination with fluvial processes. The chasmata were subsequently broadened by hillslope erosion: boulders are strewn along the top of this dusty mantling unit. Slumping, possibly caused by faulting, along the southern wall of Hyblaeus is visible at the intersection with Elysium Chasma.

This image also shows a number of dark streaks along the walls of Elysium Chasma, further to the south. One fresh-appearing streak divides around a slight ridge in the second subimage (about 1 kilometer across). Other smaller, fainter, possibly older streaks have formed on either side of this ridge, producing a herringbone-like pattern. A number of explanations have been suggested for these streaks, including the idea that they are formed by dry avalanches of dust.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

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This image shows raised ridges on a plain to the north of Juventae Chasma. Juventae Chasma, a canyon that is part of the Valles Marineris system, stretches for 180 kilometers (110 miles) east-west and 250 km (155 mi) north-south. Several examples of raised features have been identified on the plains near this canyon.

The raised ridges in this image (see subimage) have been explained as former stream channels that are now preserved in inverted relief. On Earth, inverted relief occurs when former depressions become elevated because materials that fill the depressions are more resistant to erosion than the surrounding terrain. For example, a depression may become filled with lava that is more resistant to erosion than the surrounding surface; gravel or boulders transported in a high energy flow protect underlying material from erosion, or sediments deposited by a flowing stream become cemented.

In this location, it is most likely that water, pure or salt water, once flowed through these channels and deposited sediments that eventually filled the channels and became cemented by some chemical precipitating from the flowing water. Over time, wind eroded the surrounding surface leaving the remnant channels exposed as raised ridges.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

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This image covers the eastern part of an unnamed crater located in the northern lowlands, showing features such as gullies, arcuate (bow-like) ridges, and scalloped terrain, that may indicate the presence of ice-rich materials near the surface.

As the CTX context subimage shows, the crater has gullies in its northern half (equator-facing slopes); no gullies are apparent in the southern half (pole-facing slopes). This observation is in agreement with theories proposing that some Martian gullies could form by melting of an ice rich-mantle deposited under different climatic conditions. Such ice-rich materials would be especially unstable in equator-facing slopes, where they would be exposed to maximum insolation (solar illumination).

The HiRISE image also shows arcuate ridges where the crater’s slopes meet the floor. These ridges are 10-to-30 meter (30-to-100 feet) wide and can be followed for hundreds of meters (yards). They are similar to terrestrial features produced by mass wasting of ice-rich materials.

This HiRISE subimage (358 x 266 m or 392 x 291 yards) shows incipient scalloped terrain in the southern slopes of the crater. Scalloped terrain—depressions with scalloped edges and polygonal fractures—has been interpreted as a sign of surface caving, perhaps due to sublimation (evaporation) of underlying ice.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

Layering is visible along the floor of a trough in Noctis Labyrinthis. The troughs in this area appear to be collapse pits and faults that extend across western Valles Marineris, the largest canyon system in the Solar System. Upwelling of the Tharsis Plateau causing extension in this region, and along with water drainage may explain the trough formation.

Layering is commonly seen along the upper walls of these troughs but in some cases, like this HiRISE image, layering is also visible along the floors of the trough. The layering along the floor could either represent rocks deposited before the trough formed that only became exposed by the removal of overlying material, or the layered material was deposited inside the trough after it already existed. Volcanism and aeolian activity could have deposited the layers, although water activity cannot be ruled out, especially if the layers formed before the trough exposed them.

Thicker layered deposits also exist within the larger troughs of Valles Marineris and their origins are also being explored and debated.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

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Seen here is the eastern edge of a dune field in a large, degraded crater in the southern hemisphere. Similar to other dunes on Mars, these dunes are dark-toned and contain gullies.

Gullies are features found on slopes and dunes in the mid-latitudes of both hemispheres. Both slope and dune gullies were initially suggested to be a result of liquid water from the surface or subsurface. Slope and dune gullies usually have different morphologies: dune gullies are more linear and have levees bordering their channels. They typically have no distinguishable, or very small, alcove and debris aprons. Slope gullies, on the other hand, often have deeply incised alcoves and channels that exhibit fluvial characteristics such as streamlined islands.

What is highly unusual about this dune field is that one of its gullies has the morphology of a slope gully (approximately 3 kilometers across)! This dune gully has a very incised alcove, what appears to be streamlined islands on the channel floor, and a large, feathery debris apron.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

This image shows an outcrop of light-toned rock in Eos Chaos, a knobby region which transitions into the Eos Chasma. The outcrop is exposed in the wall of a mesa (a flat-topped, steep-sided plateau).

The outcrop is prominent in the eastern part of the image. Most of the material is light and shows many small scarps or benches. In places these appear to indicate boundaries between layers, but they are often discontinuous. The light material is buried by a thin mantle of dark material in places; the dark material is from other rock layers—possibly those above the outcrop&mdashand has fallen or been blown over the light rock.

Near the top of the outcrop, there is a distinctive layer that appears as a dark band at low resolution. At the full resolution of HiRISE, this appears to be a layer breaking up into angular boulders, indicating different rock properties than the underlying light rock. There does appear to be some light material above this layer, suggesting that the process that deposited the light material continued for some time.

Ultimately, the mesa is capped by a thin veneer of dark material with a rippled texture, forming most of the southern part of the image. These ripples likely formed by wind blowing sand or dust, but they may have become indurated (hardened) enough to become inactive, since they are not found within small craters on the mesa top.

The light deposits could have formed by a variety of processes. Proposed deposition mechanisms for light-toned sediments on Mars include those from rivers or lakes, volcanic ash or wind-blown sand or dust. The dark boulder-rich band is also of uncertain origin, but it is likely harder rock, more resistant to erosion.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

HiRISE image of a proposed landing site for the Mars Science Laboratory (MSL) in Nili Fossae Trough.



POSTSCRIPT
For information about NASA and agency programs on the Web, visit: _http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.

Source: HiRISE

Release date Feb 14, 2008
Latitude: 3.61 S
Longitude: 333.73 E




This image of layered deposits in Aureum Chaos was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on June 6, 2007 at 0347 UTC (11:47 p.m. EDT on June 5, 2007), near 3.5 degrees south latitude, 333.25 degrees east longitude. The CRISM image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 40 meters (132 feet) across. The region covered is just over 10 kilometers (6 miles) wide at its narrowest point.

Aureum Chaos lies in the eastern part of the Valles Marineris canyon system, southwest of a 280 kilometer (174 mile) diameter, highly modified impact crater called Aram Chaos. Both regions hold examples of chaotic terrain that is characterized by randomly oriented, large-scale mesas and knobs. In this region of Mars, these features range in size from a few kilometers to tens of kilometers wide and tend to be heavily eroded. As its name implies, chaotic terrain is extremely irregular. It is most likely the result of collapsed surface material that settled when subsurface ice, water, or magma was released.

The top panel in the montage above shows the location of the CRISM image on a mosaic taken by the Mars Odyssey spacecraft’s Thermal Emission Imaging System (THEMIS). The CRISM data cover an area riddled with knobs. The lower two images were constructed by draping CRISM images over topography and exaggerating the vertical scale to better illustrate the region’s topography. The upper right is an infrared, false color image that reveals layered deposits of a light-colored material along the flanks of several knobs. The lower-left image reveals the mineralogical composition of these layers, with yellow representing monohydrated sulfates (sulfates with one water molecule incorporated into each molecule of the mineral) and blue polyhydrated sulfates (sulfates with multiple waters per mineral molecule). There are two possible explanations for the compositional banding. The first is deposition of mono- and polyhydrated sulfates in alternating layers. The second is deposition of just one sulfate type, and subsequently its alteration by weathering at the exposed, eroded surface. Further observations will better determine the origin of these complex banded sulfate deposits.

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad.
CRISM's mission: Find the spectral fingerprints of aqueous and hydrothermal deposits and map the geology, composition and stratigraphy of surface features. The instrument will also watch the seasonal variations in Martian dust and ice aerosols, and water content in surface materials — leading to new understanding of the climate.

Credit: NASA/JPL/JHUAPL/ASU

Source: CRISM

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This image shows dunes in an unnamed crater in the west Arabia Terra region. The rim of the crater lies to the south of the image and a dark, toned