Central peaks form when a large impact crater rebounds after the initial compression stage, lifting deep bedrock up into hills or mountains. Ritchey Crater is a large (more than 100 kilometer diameter), well-preserved impact crater in the southern highlands of Mars, south of Valles Marineris.

This HiRISE color image reveals a rich diversity of colors and textures in the central region of the crater. For example, the subimage shows several densely fractured outcrops of bedrock with a range of colors due to different rock types, partially covered by dark sand dunes.

In the middle of the area is a medium-dark material that contains many bright rock fragments—perhaps breccia (broken up and randomly jumbled rocks). There are raised ridges—both straight and sinuous—which may mark fractures and channels that could have been indurated (hardened) by water-deposited minerals. The heat of the impact event could have driven hydrothermal circulation of water for many centuries.

The colors in this image are from the infrared, red, and blue-green filters, in which each color band is given a separate contrast stretch. In the cutout the colors were further enhanced in intensity to reveal more subtle variations. If a rover could land here, it would be able to study a treasure trove of diverse rocks and minerals and ancient environments.



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

How could a valley with flowing water become a high-standing ridge?

When rivers flow, they carry sediment or particles with them. The heavier and larger particles are deposited on the bottom as characteristics of the flow, such as a decrease in speed. The sediments build up and, over time, can fill in a river completely. This would typically occur on a flat plain, so that the filled-in river would be level with the surrounding banks.

As more time passes, wind erosion affects the landscape. The sediment in the valley could be more resistant to erosion, which would allow it to exist while its banks erode.

The sinuous ridge in this image, in eastern Arabia Terra in the northern hemisphere, might have been a valley with flowing water in ancient times. At the north (top) end of the image, the ridge transitions to a depression as opposed to being raised. This depression (not imaged by HiRISE) extends into a valley. The Martian valley networks are thought to have formed by flowing water billions of years ago. At the center of the right side of the image (see subimage, approximately 350 meters across) there is a branch in the ridge, which supports the valley network theory.

(A sinuous feature is one that winds about in a snake-like pattern, and a ridge is a high-standing feature.)



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 the portions of the interior slopes and central uplift of an approximately 25 kilometer (approx. 16 mile) diameter impact crater in the Terra Sabaea region of Mars.

Along the slopes of the crater walls and flowing down the central uplift are hundreds of dark slope streaks, features that are up to a few hundred meters wide and several kilometers long. They generally start at a point and widen downslope as a single streak or branch into two or more streaks.

Many hypotheses have been proposed for how they formed on the surface, such as liquid stains or flows, dry avalanching, geochemical weathering, and moisture wicking. Recent observations of dark slope streaks at 78 unique sites in HiRISE images have shown that they have topographic relief where the dark interior surface is lower than the surroundings. The relief is most apparent in images that have low sun illumination (i.e., sun low in the sky), where the dust is sufficiently thick, and along slopes facing away from the sun.

These results by Chuang et al. (2007), soon to be published in Geophysical Research Letters, indicates that material must have been removed in the formation of streaks. Their conclusion is that slope streaks are most likely formed by avalanches of dry dust, similar to previous conclusions by other authors on this subject.



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 terrain in this image is located in Amphitrites Patera, in the southern hemisphere of Mars.

A smooth mantle, apparently made of mostly fine material, covers an older underlying surface. For example, in the center of the image we can distinguish the shape of an ancient crater (roughly 3 kilometers or 1.9 miles across) that was filled by the mantling material. Subsequent erosion of this material has partly exhumed the crater. At full HiRISE resolution the smooth surface is revealed to contain criss-crossing cracks and a few scattered blocks.

The various large depressions we observe within this mantle have scalloped edges, typically with a steep pole-facing scarp and a gentle equator-facing slope. This oriented asymmetry is believed to be caused by insolation, although the precise formation process remains unknown. These scalloped depressions are typically found in zones of the mid-latitude mantle of Mars. They are generally located between 45 and 60 degrees in both hemispheres.

It is clear that these features have grown, as some of the depressions have apparently coalesced together, and their formation could involve sublimation (the process of solid material going directly to a gaseous state) of interstitial 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

This HiRISE image shows a graben (roughly 2.5 kilometers or 1.6 miles wide) cutting a ridge near Memnonia Sulci, a region of Mars west of the massive Tharsis volcanic province.

A graben is a trough created when two normal faults (faults dipping at an angle, with the overhanging wall sliding downwards) opposite each other lower the block of rock in between them. They are commonly associated with the tectonically-driven extension of a region and are also found in volcanic areas. Graben occur on many planets and moons, including Earth.

In this case, the graben (running roughly east-west, indicating extension in the north-south direction) is cutting a ridge, showing that the graben is more recent. The ridge may also be tectonic in origin, representing a different epoch and different type of tectonic activity.

Relationships like this can be used to determine the sequence of events in the history of the region. The graben walls can also expose the local rocks at depth; in this case there is no obvious indication of layering.



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

Centered in this image is a high-standing mound of material that sits within a large impact crater (the edges of which are not visible). Evident are numerous dark streaks that originate in the higher elevation areas near the center of the mound.

These streaks are possibly areas where the lighter surface dust cover has been disturbed and partially stripped away, revealing a darker layer beneath the dust. The dark streaks fade fairly rapidly as layers of bright dust settle over them.



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 parial circular or ringed structure in the middle of this scene is an impact crater, approximately 3.25 kilometers (approx. 2 miles) in diameter.

Since its formation, the crater has had its southern half cut away by the formation of the gorge, called Ganges Chasma. The resulting exposure of rocks along the rim of the cliff allows planetary geologists to study a cut-away, side-view of layered rocks. This view is particularly interesting here because the rock layers of the upper plains are visible in their original form outside of the crater, and in modified form within/beneath the crater, along with structures imparted by the impact.

The floor of the crater may have been filled by lavas or other material that is more resistant to erosion than the surrounding layers, since the floor of the crater sticks out into the chasma.



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

For Immediate Release

October 19 , 2007

Above are a few examples of the "browse" products the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument obtained of areas on Mars near proposed landing sites for the 2009 Mars Science Laboratory. They include enhanced color images of West Candor chasm (A) and Nili Fossae trough (B); false color images indicating the presence of hydrated (water-containing) minerals in West Candor (C ); and clay-like (phyllosilicate) minerals in Nili Fossae (D).

CRISM is one of six science instruments on the Mars Reconnaissance Orbiter, currently circling the red planet.

Credit: NASA/JPL/JHUAPL

Click on the image for a larger version.

Scientists scouting potential landing sites for NASA's next Mars rover mission are using new data from a powerful mineral-mapping camera to narrow the site selection.

When NASA Mars Program officials and members of the Mars science community gather in California next week to pare down the list of candidate landing sites for the 2009 Mars Science Laboratory (MSL), they can refer to 125 new images from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). The images and accompanying analysis products are available on the CRISM Web site at _http://crism.jhuapl.edu/msl_landing_sites/.

Built and operated by the Johns Hopkins University Applied Physics Laboratory (APL), CRISM is one of six science instruments on NASA’s Mars Reconnaissance Orbiter, currently circling the planet.

"Since MSL will assess whether Mars ever had an environment capable of supporting life, it will have to land in an area with a mineral record indicative of past water,” says Dr. Scott Murchie, CRISM principal investigator from APL. “CRISM is critical to the selection process because it is the only instrument on MRO with the spectral power to 'see' the chemical makeup of the rocks."

One of CRISM’s main mission objectives is to find and investigate areas that were wet long enough to leave a mineral signature. Offering greater capability to map spectral variations than any similar instrument sent to another planet, CRISM can read 544 "colors" of reflected sunlight to detect minerals in the surface.

The imaging spectrometer is among MRO's cadre of advanced sensors studying Mars in unprecedented detail and contributing to the MSL landing site selection effort. This includes correlating CRISM’s spectral data with high-resolution pictures of boulders, craters, sediment layers and other surface features acquired by the High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX). "CRISM images provide the scientific criteria that will allow the MSL team to narrow its choices," Murchie says. "By combining data from the MRO instruments, we can create a complete picture of the Martian surface."

The CRISM data release consists of user-friendly, color-coded, thematic images. Different versions of each image show clays, sulfates, and unaltered minerals that help tell the story of past water and volcanic processes on Mars. The set also includes infrared images of surface brightness and enhanced visible-color composites. Each image covers a square area roughly 6 miles (10 kilometers) on a side, with a spatial resolution of approximately 66 feet (20 meters) per pixel.

"The data products that we have generated for all the proposed MSL landing sites are scaled in a similar manner. This should make it easy for scientists and the public alike to distinguish between landing sites that possess a wide range of rock types, from ones that do not," says APL's Dr. Olivier Barnouin-Jha, who with Dr. Frank Seelos (also of APL) assembled the products in this release. "Going to a location with greater rock diversity will ensure that MSL significantly enhances our understanding of the geological history of Mars, including the history of water."

CRISM has mapped more than half the planet in its low-resolution mode since MRO’s two-year science mission began in November 2006, in addition to making more than 2,500 high-resolution observations of the surface and nearly 3,000 atmospheric observations.

APL, which has built more than 150 spacecraft instruments over the past four decades, led the effort to develop, integrate, and test CRISM. The CRISM team includes experts from universities, government agencies and small businesses in the United States and abroad; visit _http://crism.jhuapl.edu for more information. Information about the Mars Reconnaissance Orbiter and Mars Science Laboratory missions is available online at _http://mars.jpl.nasa.gov/. The Jet Propulsion Laboratory, a division of the California Institute of Technology, manages the MRO mission for the NASA Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor and built the MRO spacecraft.

Media Contact:

Michael Buckley
(240) 228-7536
Michael.buckley@jhuapl.edu

Source: CRISM - News Center

Dazzled by the beauty of the strange features in the Athabasca Valles channel system on Mars, geologist Windy Jaeger pondered their origin. In a new paper, she concludes that lava filled the channel system to the brim and then drained away leaving a thin coating of hard lava rock to preserve the underlying landscape. Other unique features indicating that massive lava flows once filled the channels are hydrovolcanic cones that formed when water met lava and boiled explosively, leaving behind small, conical and ring-shaped features visible in and around the dune field (upper left).

Source: NASA - Mars Reconnaissance Orbiter - Images

This image shows some dark slope streaks where small impact craters are visible at their apexes. These craters have little splashes of dark ejecta, which indicate that they were throwing up the same dark-toned material that the slope streak has revealed.

These dark slope streaks and the medium-toned one to the left show longitudinal ridges that are indicators of the flow of material during the slope streak event. Older, almost completely faded slope streaks can be seen to source off of the crater in the upper right corner of this portion of the image.



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 layering at the base of the south polar layered deposits exposed on a scarp. The south polar layered deposits are composed primarily of water ice with a small amount of dust.

The layers were laid down over a large area near the south pole, probably over the past few million years. They are believed to record recent global climate changes on Mars in much the same way that polar ice in Greenland and Antarctica provide information about varying climatic conditions on Earth.

Some of the layers have an irregular or wavy appearance. This may have been caused by the flow or deformation of the ice at some point in the past, in addition to uneven erosion. A few layers also appear to be converging or to be truncated (center of image). These are called unconformities. Unconformities form when an episode of erosion removes all or parts of existing layers and is later followed by more deposition. Surface fractures, channels, knobs and other features, along with the obscuration of layer contacts, point to a comicated recent history, but also make it difficult to characterize indiviual layers.



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 plains northwest of Juventae Chasma, one of the Martian canyons that are part of the equatorial Valles Marineris system. The two most noticeable features in this scene are craters on mesas (plateaus) and raised, winding ridges.

The raised ridges are inverted channels. It is likely that liquid water, either pure or salt water, flowed through these channels. The channels are raised because streams transport sediment as they flow, deposit the heavier sediment on the stream floor, and, eventually fill in once their water supply dwindles. Over time, wind erosion modifies a landscape, and this has played an important role on these plains. It eroded the land around the channels leaving the remnant channels exposed and standing high. The channels did not erode as much since they were more resistant, possibly because the deposited sediment had cemented together.

The craters on mesas are also evidence of active wind erosion. When craters form, they eject material out onto the surrounding landscape. It appears that several of the craters’ ejecta visible here cemented, making the ejecta more resistant to erosion and leaving them standing high as craters on plateaus.

The subimage (approximately 1120 meters across) shows a juncture of two of the inverted channels. It is likely that the water flowed from the left to the right of the scene, because channels usually join rather than divert unless there is an obvious obstacle in the way. No such obstacle is seen here, but one might have been present when the stream originally flowed. However, there is no way of knowing this.



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 streamlined features in the northwest Tharsis region. The trough running diagonally to the left near the bottom of the image is part of the Jovis Fossae, a series of parallel troughs.

Streamlined features are carved by catastrophic floods. When a flood encounters an object, it diverts around it and erodes material in its path. One great example of a streamlined island is at the top left of the image between the branch of the channels. The flow was likely from the right to the left, as suggested by the fact that the island tapers off to the left. Part of the island stands higher than the rest. This section was probably higher than the floodwaters reached.

There is another streamlined island about one third of the way down the image. This island is very narrow, and its shape is also consistent with the flood coming from the right.

This island has a couple of dark slope streaks, as does an elongated mesa near the Jovis fossa (trough) at the bottom of the image. It is thought that small impacts and rockfalls can initiate the dust avalanches that are currently believed to form the slope streaks. The dark material for the slope streaks probably came from the dark layers visible at the top of the mesa; see subimage, approximately 300 meters (328 yards) across.



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 a crater with a wind streak in the southwest Tharsis region.

The crater is a relatively pristine one that has not experienced extensive modification as seen by the existence of its steep slopes and raised rims. However, it has gone through some changes, such as the small crater on its south rim and the dunes on its floor.

The wind streak to the left of the crater indicates that the wind was coming from the northeast/east direction(the right of the image) when this crater formed. The wind caused the crater’s ejecta to be deposited in the downwind direction. The crater in the middle of the wind streak (see subimage, approximately 350 meters across), existed before the crater with the wind streak formed. There is a thin veneer of the larger crater’s ejecta on top of the smaller crater; also, there are ejecta blocks from the large crater’s impact visible on top of the smaller crater.

It is unknown what makes the wind streak two-toned with a darker halo surrounding the brighter interior. It is possible that the particles in the wind streak have different average sizes and that light scattering makes one set of particles appear brighter.



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 a scarp exposing the south polar layered deposits (SPLD). The polar layered deposits are thought to record recent climate variations on Mars, similar to ice ages on Earth.

Radar data indicate that the SPLD are ice-rich, with variations in dust contamination likely causing the layering visible here. HiRISE images of the SPLD will help to unravel Mars' climate history, but this image illustrates how this effort is complicated.

The development of surface features, by erosion, deposition, or modification of the surface, makes it difficult to determine the characteristics of the layers themselves. Some of the layers appear wavy, perhaps due to folding, flow, or uneven erosion since they were laid down. Short, branching, often radial channel systems are cut into the surface of the layers in places. These may be related to "spiders," thought to be formed as carbon dioxide gas flows along the surface when the seasonal polar cap sublimates in the spring. Pits and polygonal fractures are visible on the layers as well.

Apparently this exposure of SPLD is relatively old, as these features probably take many years to form. While these features are interesting in their own right, they disturb the SPLD outcrops and make it more difficult to measure the thickness of layers and compare them to other outcrops of SPLD.



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 part of the floor of Rabe Crater, a large (108 kilometers, or 67 miles in diameter) impact crater in the Southern Highlands.

Dark dunes&emdash;accumulations of wind blown sand&emdash;cover part of crater's floor, and contrast with the surrounding bright-colored outcrops. The extreme close-up view reveals a thumbprint-like texture of smaller ridges and troughs covering the surfaces of the larger dunes. These smaller ripples are also formed and shaped by blowing wind in the thin atmosphere of Mars.

One puzzling question is why the dunes are dark compared with the relative bright layered material contained within the crater. The probable answer is that the source of the dark sand is not local to this crater; rather, this topographic depression has acted as a sand trap that has collected material being transported by winds blowing across the plains outside the crater.



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 ancient cratered highlands of the southern hemisphere of Mars has an intriguing and complex history as it has been riddled with impact craters and modified by volcanic processes and by the wind.

Additionally, it is one of the most heavily dissected terrains on Mars exhibiting the densest population of valley networks: old dried up channels and valleys that may have been formed by surface runoff, the seepage of ground water, or both.

Recently, the Thermal Emission Imaging System (THEMIS) aboard Mars Odyssey (MO), in conjunction with spectral data from the Thermal Emission Spectrometer (TES) aboard the Mars Global Surveyor (MGS) have revealed the presence of a unique surface deposit that may be rich in chloride salts formed from the presence of liquid water. Three separate missions (MGS, MO and MRO) have come to reveal the composition and nature of these unique deposits, which, although they occur as relatively small deposits (less than 25 square kilometers) are widely distributed in Noachian (most ancient) terrains with fewer occurrences in the Hesperian (middle geologic time) terrains.

This HiRISE infrared color sub-image (approximately 900 meters wide) shown here is part of one such deposit in an ancient partially buried unnamed crater in Terra Cimmeria, that shows this deposit in a light-toned almost fleshy color. The deposit appears to be relatively thin and occurs in low-lying areas. It is also heavily pockmarked and discontinuous, possibly from removal of the material by erosion. Both of these aspects suggest that the deposit is indeed very old.

The presence of such salts is intriguing, and strongly suggests that conditions were favorable for water near or at the surface in the geologic past. Polygonal cracks can be observed in this image and other images of these deposits elsewhere on Mars (PSP_003160_1410) and are similar to desiccation cracks (formed from the rapid evaporation and drying of a wet surface) and indicate that these may were more likely deposited at the surface. However, the volume and duration the water required for these deposits is still being investigated.



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 target was suggested by Jonna Sotelo Douglas in Tucson, Arizona. She writes: "This image is of the confluence of the Nigral and Uzboi Valles and part of the southern rim of Luki crater. The confluence area is marked with dunes, boulders, and other types of sediment formations. As the elevation lowers from the crater wall, the area smoothes out. There are gullies on both sides of the crater wall."

Nirgal and Uzboi Valles are two valleys to the north of the Argyre impact basin in the southern hemisphere. At this location, the smaller channel, Nirgal Vallis, empties out into the larger Uzboi Vallis.

Most of the features in this image are covered by the dust that is ubiquitous on Mars, hiding the original fluvial features. However, a small patch of resistant outcrop can be observed on the southern side of the crater rim. These appear as white patches that are draped by the darker wind-blown rippled sand (see subimage 1). Even the resistant outcrop has been modified by wind, giving it a pockmarked or scalloped texture.

Layering can be seen in the resistant outcrops and in the gullied inner wall of the crater (see subimage 2). These layers may have been fluvial, volcanic, or aeolian (wind-blown). Given their presence within the valley floor, these may represent some of the sedimentary layers deposited by water when it flowed through the valley.



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 North Meridiani.

For more information about the mission and a timeline, visit the MSL Web site.



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 a terraced fan (center left) located adjacent to a short valley. Terraced fans are rare deposits on Mars: they have only been seen in a few dozen locations.

On Earth, terraced fans are found in alluvial environments and in deltas. When water flowing down steep slopes, such as mountains or hills, encounters a flatter surface, the sediments carried by the water are deposited along the shallow slopes to form alluvial fans. Deltas can also produce terraced fans when water from rivers and streams meets oceans or lakes; a delta deposit results at the contact between the confined, fast-moving water (river/stream) and the open body of water (ocean/lake).

The fact that this Martian terraced fan is found adjacent to a valley supports the hypothesis that water was the mechanism that transported and deposited the material that now forms the fan. It is unclear, however, if this fan formed in an alluvial or deltaic environment, or by some other process.



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 Ariadnes Colles (updated landing ellipse location).

For more information about the mission and a timeline, visit the MSL Web site.



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 a large outcrop of layered rock in Tithonium Chasma, a part of the Valles Marineris trough system.

Light, layered sediments are found at many sites on the floor of Valles Marineris. Observations drawn from this image will help understand the history of deposition at this location, and can be compared with nearby related rocks.

A light-toned unit (tan in the RGB color image) is found through most of the image. At high resolution, this unit often shows thin layers; it resembles light deposits found at many other sites. The light-toned materials are overlain by a dark unit (blue in the RBG color) that may have been deposited over the lighter rock much later. Variations in tone and color may indicate deviations in rock properties, such as the source material, cementation, or deposition process; in some cases they may simply be due to varying amounts of dust cover.

It is still unclear how the layered rocks in Valles Marineris formed. They might be sediments laid down in lakes or streams, wind-deposited, or volcanic materials. All of these processes can form layered rocks on Earth.

The dark material in the western part of the image appears to have once been a continuous layer over the current topography, now being eroded; if it was indeed draped, rather than laid down horizontally, it was most likely formed by dust or volcanic ash settling uniformly out of the atmosphere.



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 suggested by Andras Sik's SUPERNOVA astronomy and space research class at the Alternative Secondary School of Economics in Budapest, Hungary.

They interpret the image: "During local springtime, a varying albedo pattern can be observed on the surface of dark intracrater dune fields in the southern polar region of Mars. The origin of dark dune spots and the dark slope streaks emanating from them is yet uncertain. There are several possible explanations for these phenomena, like "sublimation of carbon-dioxide frost cover", "dusty carbon-dioxide gas eruptions through the frost cover" and "transient liquid water-formation under layered water-ice/carbon dioxide-ice cover". In this HiRISE image the distribution of dark streaks are not chaotic and their shapes are not fan-like; rather they are composed of confined, dozen-hundred meter long branches which follow the local topography and have accumulation zones at their end."

We are learning a great deal from the enigmatic dark spots that are found throughout the south polar region. These dark spots may have resulted from cold gas jets that form by sublimation of the ice bringing entrained dust to the surface. Small dark streaks may have formed by avalanches of sand or they may be patches of coarse-grained ice that are clear enough so that the dark material below the ice is visible.

The color image also provides helpful clues to understand this process. Bright white frost can be seen covering the surface. This frost is a probably a combination of frozen water and carbon dioxide ice. These bright patches are particularly prevalent along dune slip faces and around dark spots.



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 part of a relatively small (14 kilometers, or 9 miles across) unnamed impact crater in Noachis Terra. The lobate-shaped crater's ejecta, gullies in its walls, and "concentric crater fill" in the crater's floor may be indicative of the presence of water and ice at some point during its history.

The subimage of a CTX context image of this same crater shows the typical lobate ejecta pattern characteristic of rampart craters, indicating that ice- or water-rich materials were excavated at the time of impact. According to this theory, the rock ejected from the crater mixed with the water and water vapor, and thus flowed more easily along the surface. Another possible interpretation is that fine-grained rocky material mixed with air and formed the rampart pattern in the absence of water.

The gullies shown in this image are similar to terrestrial gullies produced by flowing water. The current Martian climate would not allow for liquid water to be stable at the surface for extended periods of time, though. It is so cold (in the order of -70^oC or -90^oF) that the water would freeze, and then it would sublimate quickly, because the air is very dry and thin (the atmospheric pressure is on average less than 1/100 of that on Earth). These gullies could have formed under a different climate, or perhaps they were carved by short-lived streams; they could also have been produced by dry landslides.

"Concentric crater fill," crater-interior deposits that form concentric ridges, is found at high latitudes (approximately above 30 degrees from the equator). Theoretical calculations indicate that ice may exist under the surface at such high latitudes, mixed with rocks and soil. The roughly concentric ridges and troughs in this crater's floor may have been produced by compression caused by viscous flow of a thick mixture of rocks, soils, and ice inward from the crater's walls.



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 internal layering in the south polar layered deposits exposed on a scarp. The south polar layered deposits are composed primarily of water ice with a small amount of dust. Variations in dust content most likely control the erosion of the layers.

Some layers have an irregular wavy appearance that may have been caused by flow of the ice in the past when the now-exposed ice was still buried. It is currently too cold at the surface in the south polar region of Mars for significant flow to be occurring today. Other layers appear to be converging and some are truncated and may represent unconformities (see subimage). Unconformities form when a previous episode of erosion removes all or part of a layer and is later followed by more deposition.

The layers were laid down over a large area near the south pole, probably over the past few million years. They are believed to record recent global climate changes and oscillations on Mars in much the same way that polar ice in Greenland and Antarctica provide information about varying climatic conditions on Earth.



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 part of the floor of a large crater in Terra Tyrrhena. Here, dark mesas contrast with light-colored, topographically lower outcrops.

The mesas have sharp cliffs, indicating the dark materials are not loose, but rather consolidated; layering is also visible along the cliffs. The underlying light materials are also layered and profusely fractured. Their superposition relationship indicates that the light materials are older than the dark, mesa-forming materials.

The image also shows a number of crest-like features criss-crossing the landscape. The fact that their relief is so prominent indicates they are more resistent to erosion (harder) than their surroundings. These crests could be indurated fractures (fractures cemented by fluids) or dikes. Dikes are tabular intrusions of rock formed when underground magma is injected along fractures.

The lowest regions in the image are covered by dark-colored dunes (see for instance the NW or upper left section of the image). These are possibly accumulations of fine-grained materials eroded-out from the mesas.



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 several parallel segments of the Cerberus Fossae. This is a system of fissures formed by extension and stretching of the near-surface of Mars. It is associated with some of the most recent large-scale events on the planet.

The Athabasca Valles channel system has its source at one segment of the Cerberus Fossae. This channel was most likely carved by a massive flood of water, perhaps released by the same tectonic processes which formed the fossae. Cerberus Fossae then extruded a large lava flow that draped Athabasca Valles. HiRISE images were recently used to describe details of this history in a paper published in the journal Science (Jaeger et al., Science, volume 317).

In the RGB false-color, this image shows a striking contrast. The plains are a generally bland beige, while the floors of the fissures are bright blue. Since the fissure walls are cutting through the lava which makes up the plains, the blue color probably indicates relatively dust-free exposed rock, while the beige is due to dust coating the level plains. Although the Cerberus Fossae released lava in places, at this site there is no evidence for a vent and the fissures have simply cut through pre-existing lava.



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 suggested by Vishal Bhalerao, a mechanical engineering student, from the K.K. Wagh Institute of Engineering Education in Maharashtra, India.

The image captures a small crater in the southern hemisphere near the south pole.

Much of the ground surface is covered by polygonal fractures, common in high-latitude areas. This suggests there is (or was) ice just below the surface at this location. There are also yardangs (long landforms sculpted by the wind) and dunes within the crater suggesting aeolian activity. Aeolian (wind-driven) processes are currently very active on the surface of Mars.

The dark and light patches at the top of the image are probably related to sublimation of carbon dioxide ice at this location.



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 captures an impact crater on the surface of Amphitrites Patera, an ancient volcano on the southern margin of the giant Hellas Basin. The Hellas Basin was formed by a very large impact into the southern highlands early in the geologic history of Mars. The basin has a number of volcanoes along its margin, perhaps because magma could take advantage of the deep cracks in the crust that resulted from the impact.

Amphitrites Patera is far enough south to approach the Martian "antarctic" and there is evidence for large amounts of ice in the ground. As in the polar regions of Earth, the icy ground (permafrost) is able to move and be modified by a variety of processes. In this case, the rim of the small impact crater is filled with a honeycomb of cracks. These are likely to have formed where dust- and soil-covered ice or ice cemented soil was cracked by thermal contraction in the winter. Subsequently, the underlying ice was able to escape into the atmosphere (sublimate) allowing the ground along the cracks to collapse. The only place where large boulders are visible is along the rim of the crater; this is probably where the boulders were not so deeply buried by the icy layer.

The Martian atmosphere was dusty at the time this image was acquired, so small imperfections in the processing are very visible in the standard image products. The cutout was specially processed to remove these artifacts.



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 plains speckled with craters in north Sinus Meridiani, a dark albedo feature.

Several of the craters have wind streaks off their southwest rims. This indicates that recently, the wind has been dominantly coming from the northeast in this region. As the wind blows, it erodes material off the crater rims, and this material can be deposited downwind, as seen here in the form of streaks. Eventually the craters' rims will be completely eroded and just faint circular features will remain.

There is a bright mesa at the top of the image that also has a very prominent wind streak. The subimage (approximately 1 kilometer across) shows the bright mesa located at the top right of the image. Part of the wind streak is visible in the lower left.

This streak can also be seen in color (see PSP_005370_1845_RGB), where the streak appears redder than its surroundings. Differences in color result from differences in composition and/or particle sizes. The western edge of the mesa appears in this color product to be tinted red, similar in tone to the mesa's wind streak.



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 several gullies along the southern wall of unnamed crater in the eastern Hellas region of Mars. This particular crater has gullies on both the polar and equatorial-facing walls.

The gully floors appear to be filled with rough-textured, somewhat knobby-looking materials. As multiple gullies located upslope feed into a single gully reaching the crater floor, the materials have converged to form a large deposit. Lineations parallel to apparent flow direction are evident on the textured surface.

It's not clear if liquid flows carved the gullies at this location, but the eastern Hellas region is well known for its abundant ice-rich flow features, such as lobate debris aprons at the base of knobs and massifs. Thus, the gully floor materials may have also incorporated ice at some time in the recent past and moved downslope as possible glacial-like 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

This observation shows a sequence of layered sedimentary rocks exposed along the wall of Ganges Chasma.

Ganges Chasma is in the northeast part of the Valles Marineris system and cuts through surrounding plains interpreted to have been resurfaced by flowing lava. The Chasma is believed to have formed due to the collapse of plateau rocks along fault systems.

The plateau above the chasma is at the left side of the image and the wall of the trough descends to the east.

The layered sequence consists of many beds that are generally horizontal and laterally continuous. Some more pronounced layers appear to be weathering to form large-scale boulders (see subimage). Many thinner layers are apparent near the top of the wall. Material has also formed spurs and ridges along the wall of the 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