Areology

Dunes and Ripples in Valles Marineris

2012-02-13T00:00:00.031+08:00

Two types of wind-blown sedimentary deposits are pictured in this scene of the floor of Ius Chasma in the Valles Marineris.

Smaller light toned ridge-like ripples draped over the bright bedrock are visible in this subimage. Long dark sand dunes superpose the small ridges, indicating that the sand dunes formed more recently than the ridges. Earlier observations have shown that the small ridges, known as "transverse aeolian ridges" or TARs, appear to be fixed in place. They are typically found near the equator of Mars, in places where the winds alternate in direction over daily or seasonal cycles.

Detailed investigations by the MER rovers revealed that the TARs were armored by a surface layer of coarse granules left behind after the smaller particles were winnowed away by the wind. These granules are too large to be lifted by the wind and preserve the TARs from further erosion. In contrast, recent HiRISE observations show that many of the dark sand dunes on Mars are actively on the move.

From these facts, we can hypothesize the recent history of the aeolian deposits here in Ius Chasma. Unconsolidated sediments were formed in the canyon by impact fragmentation and erosion of the steep canyon walls. These sediments were eroded and shaped into dunes by the winds that blow up and down the canyon, alternating direction between day and night. Eventually the tireless winds won the battle over sediment supply, and the remaining sediments were sifted into the TARs visible in the image, oriented perpendicular to the length of the canyon (transverse to the winds).

More recently, a fresh supply of sand was introduced into the canyon that the winds have not yet had time to tame. Instead of forming simple crescent dunes, the bidirectional winds have shaped the sand into long linear dunes punctuated by short slip faces. At high resolution, we see that the linear sand dunes are ruffled along their lengths by ripples transverse to the wind directions. Ultimately, most of this sand will be swept away, leaving the TARs trapped behind.

Photo credit: NASA/JPL/University of Arizona

The Phoenix Lander After Two Mars Years

2012-02-12T00:00:00.002+08:00

This is one of a series of images to monitor frost patterns at the Phoenix landing site.

The lander and backshell are visible, but not the parachute or the dark halo around the lander which is covered by dust. (Although the lander may appear strange, we have to remember that its solar arrays have collapsed.)

This is the same appearance to the hardware as 1 Mars years ago, in 2010. For views of the lander during the active mission in 2008, see our special releases page.

Photo credit: NASA/JPL/University of Arizona

Looking for an Impact Crater on a Dune

2012-02-11T00:00:00.002+08:00

This dune field image was requested since a prior lower-resolution (THEMIS VIS) image of this area had suggested the possible presence of an impact crater on the dunes. Finding an impact crater on a dune field would be quite important: as of 2011, no craters have been found on Martian dunes, which strongly supports the hypothesis that the dune fields are very young features and either formed or have actively evolved during the last tens of thousands of years.

No crater is visible in this dune field image, which is consistent with the "active" and "fresh" appearance of these dunes: (1) they have sharp crestlines and (2) slipfaces (the downwind slope; generally pointing towards the south-southwest in this field, although there are some signs of a reversing slipface, implying that some past winds have pushed sand towards the northeast-north northeast) are generally very smooth in appearance, except for some small avalanche features (which form as sand accumulating at the upper-portion of the slipface).

The search for a dune-field crater will need to continue...

Photo credit: NASA/JPL/University of Arizona

Note: This image is located in an unnamed crater in Bosporus Planum northwest of Argyre Planitia.

Spirit Lander and Bonneville Crater in Color

2012-02-10T00:00:00.003+08:00

HiRISE has never before imaged the actual lander for the Spirit rover in color, on the west side of Bonneville Crater. The lander is still bright, but with a reddish color, probably due to a dust cover (lower left in the subimage).

A bright spot from a remnant of the heat shield is still visible on the north rim of Bonneville Crater. The backshell and parachute are still bright, but were not captured in the narrow color swath.

The rover itself can still be seen near "home plate" in the Columbia Hills, but there is no obvious sign of rover tracks--erased by the wind.

Photo credit: NASA/JPL/University of Arizona

MARSIS' Map of Mars' Northern Hemisphere

2012-02-08T00:00:00.005+08:00

A pole-to-equator map of the Martian northern hemisphere, displayed in polar stereographic projections. The map is color-coded to indicate the MARSIS mean dielectric constant of a number of geological units.

Map credit: Figure courtesy of J. Mouginot et al.

Notes: For further details see Mouginot, J., et al., "Dielectric map of the Martian northern hemisphere and the nature of plain filling materials", 2012, Geophysical Research Letters, 39, L02202. DOI:10.1029/2011GL050286 For more information, see Mars Radar Finds Possible Ocean Sediments.

Late Afternoon on Mars

2012-02-07T00:00:00.001+08:00

NASA's Mars Exploration Rover Opportunity used its panoramic camera to capture this low-light raw image during the late afternoon of the rover's 2,847th Martian day, or sol, of work on Mars (January 27, 2012).

The rover is positioned for the Mars winter at "Greeley Haven," an outcrop located on the north end of Cape York on the rim of Endeavour Crater. This site provides an approximate 15-degree northerly tilt for favorable solar energy production.

Plans for research continuing through the winter months at Greeley Haven include a radio-science investigation of the interior of Mars, inspections of mineral compositions and textures on the outcrop, and assembly of a full-circle, color panorama of the surroundings.

Photo credit: NASA/JPL-Caltech/Cornell/Arizona State University

Crater with Gullies on a Central Structure

2012-02-06T00:00:00.000+08:00

The 40-kilometer diameter unnamed crater (49 degrees North, 21 degrees East) in this image is located west of Lyot Crater and north of Deuteronilus Mensae in the Northern Plains of Mars.

As seen in the subimage, gully systems in the central structure have eroded underlying layers (undercutting) that are less resistant to erosion than the surface rock of the central structure. Previous channelized water flows likely transported the eroded sediments toward the southeast and deposited them forming the expansive debris aprons.

The formation of channels on the debris aprons supports the hypothesis that these sediments were transported down the gullies and then deposited onto the aprons by flowing water. In the larger, northernmost system, sediments have partially filled in the channel segments and winds have remobilized these sediments forming the dunes that line the gullies.

This is a stereo pair with PSP_009298_2295.

Photo credit: NASA/JPL/University of Arizona

The Floor of Toro Crater

2012-02-05T00:00:00.002+08:00

Toro Crater may have experienced hydrothermal alteration, producing diverse minerals. The mineral diversity leads to diverse color in HiRISE, especially when enhanced as in this subimage.

In general the blue and green colors indicate unaltered minerals like pyroxene and olivine, whereas the warmer colors indicate alteration into clays and other minerals. The linear north-south trending features are windblown dunes that are much younger than the bedrock.

This is a stereo pair with ESP_025344_1970.

Photo credit: NASA/JPL/University of Arizona

Active Erosion in Pasteur Crater

2012-02-04T00:00:00.001+08:00

This image shows knobs and bluffs that are being actively eroded by the Martian wind. Fine, light-toned sedimentary layering is exposed in the bedrock at the base of the cliffs.

Also in this scene are two types of unconsolidated aeolian sediments. The reddish ridges are relatively immobile, and are probably similar to granule ripples on Earth that are protected from the winds by a surface layer of coarse grains. The dark gray dunes are probably made up of fine (approximately 0.1 mm) basaltic sand. Previous HiRISE images (PSP_001756_1995, PSP_010643_1995) showed that the sand in Pasteur Crater is currently mobile.

This sand is thought to be locally derived, from dark deposits within a small crater called Euphrates that is located within Pasteur, upwind of the sand dunes. The movement of this sand contributes to the erosion of the ancient bedrock, sandblasting the formation into the knobs seen today and exposing layers that were deposited in ages past.

Photo credit: NASA/JPL/University of Arizona

Well-Preserved Crater in Terra Sabaea

2012-02-03T00:00:00.005+08:00

Shown here is a stereo pair (see the anaglyph) of a well-preserved impact crater about 6 or 7 kilometers wide from rim to rim. By well-preserved we mean that the crater has a sharp rim, deep cavity, impact morphologies preserved down to scales of tens of meters, and little sign of infilling or degradation by a range of processes (other impacts, volcanism, tectonism, icy flow, aeolian erosion and infill, etc.).

When seen at full HiRISE resolution, almost all craters on Mars do show some modification such as subsequent smaller impacts, wind-blown deposition and/or erosion, and downslope movement of material on steep slopes.

We have imaged hundreds of well-preserved impact craters on Mars ranging from 1 meter to more than 100 kilometers wide. These targets are of great interest for multiple reasons: first, we want to better understand impact cratering, a fundamental surface process. Second, such craters often contain good exposures of bedrock in the steep walls and, if the crater is large enough, in the central uplift. Just like terrestrial geologists are attracted to good bedrock outcrops like road cuts, planetary geologists are attracted to well-preserved craters.

Third, the steep slopes often reveal active processes, such as formation of gullies, boulder falls, and slope streaks that could form in a variety of ways. Some of these active processes could be related to water, since the crater may expose lenses of ice or salty water, or create deep shadows that trap volatiles, or expose salts that can extract water from the air.

This is a stereo pair with ESP_024738_1595.

Photo credit: NASA/JPL/University of Arizona

Note: This crater is located on the border of Terra Sabaea, being to the northwest of Hellas Planitia. The closest named feature is Harris Crater.

Very Fresh Impact Crater Superposing a Wrinkle Ridge in Hesperia Planum

2012-02-01T00:00:00.001+08:00

The ridge captured in this HiRISE image is called a wrinkle ridge. This wrinkle ridge is located in Hesperia Planum, a region of over two million square kilometers (over 770,000 square miles) in the southern highlands of Mars. It is located northwest of the Hellas basin and adjacent to Tyrrhena Patera and contains abundant orthogonal and intersecting wrinkle ridges.

Wrinkle ridges are long, winding topographic highs and are often characterized by a broad arch with superposed narrow asymmetric ridges. These features have also been identified on the Moon, Mercury, and Venus. Their origin is attributed to horizontal compression or shortening of the crust due to faulting and folding. They commonly have asymmetrical cross sectional profiles and an offset in elevation on either side of the ridge.

Superposing or located on top of the wrinkle ridge, is a very fresh impact crater. We can tell that this crater is fresh because of its relatively sharp or crisp rim and unmodified shape. If you look closely, you can see faint rays of relatively fine material, boulders, and smaller secondary craters radiating from the crater and superposing the wrinkle ridge and older surrounding craters.

Photo credit: NASA/JPL/University of Arizona

Note: For an mp4 video clip of this area, including additional photographs, click here.

Opportunity's Three-Year Trek Across Mars

2012-01-31T00:00:00.002+08:00

During the three-year trek of NASA's Mars Rover Opportunity from Victoria crater to Endeavour crater, rover planners captured a horizon photograph at the end of each drive. 309 images taken during the 13-mile journey appear in this video.

Video credit: NASA/JPL-Caltech/Cornell/Arizona State University

Dunes in Noachis Terra

2012-01-30T00:00:00.002+08:00

This enhanced-color image shows sand dunes trapped in an impact crater in Noachis Terra, Mars. Dunes and sand ripples of various shapes and sizes display the natural beauty created by physical processes. The area covered in the image is about six-tenths of a mile (1 kilometer) across.

Sand dunes are among the most widespread wind-formed features on Mars. Their distribution and shapes are affected by changes in wind direction and wind strength. Patterns of dune erosion and deposition provide insight into the sedimentary history of the surrounding terrain.

The image is one product from an observation by the High Resolution Imaging Science Experiment (HiRISE) camera taken on November 29, 2011, at 42 degrees south latitude, 42 degrees east longitude. Other image products from the same observation are at http://www.uahirise.org/ESP_025042_1375.

Photo credit: NASA/JPL-Caltech/University of Arizona

Note: This caption is very similar to that of the recent post, Sand Dunes in Noachis Terra. Although the pictures are different, I wouldn't be surprised if both images come from the same crater.

Double Layer Ejecta in an Arabia Region Crater

2012-01-29T00:00:00.007+08:00

When impact craters form, they are generally surrounded by "ejecta": material that is thrown out from the crater by the impact and that settles onto the surrounding terrain. Sometimes there are multiple phases of material that fall to the ground (although both result from the same impact), creating the appearance of layered-ejecta.

This DLE [double layer ejecta] crater formed at the edge of an older/pre-existing crater, the rim of which deflected some of its ejecta. As it deflected the two phases of falling ejecta differently, we can use it to study how ejecta is transported and deposited. With HiRISE resolution, it may be possible for us to determine topography of the rim and then to see how high the barrier was that deflected some of the ejecta flow.

This is also an unusual crater because it is outside the Northern Plains and is relatively young.

This is a stereo pair with ESP_017356_2175.

Photo credit: NASA/JPL/University of Arizona

Notes: This crater is located along the "shore" between Arabia Terra and Chryse Planitia. The closest named feature is Cydonia Mensae to the west. Also, Note: For an mp4 video clip on this impact crater, including additional photographs, click here.

Fluvial Fan on a Crater Floor

2012-01-28T00:00:00.005+08:00

This observation shows a terrific fan-shaped deposit, beginning where the channel enters a crater. This is suggestive of a delta: a deposit that forms when water in a channel flows into a larger area (such as an ocean or a lake). As the water spreads out, it moves slower and drops the sediment that it is carrying, forming the delta. (E.g., a famous Earth example is the Nile River delta.)

The THEMIS instrument also photographed this area (I03235002), as well as the Context Camera (CTX) aboard the Mars Reconnaissance Orbiter. The resolution of HiRISE helps scientists determine the topography of the region which is needed for establishing the stratigraphic relations and flow direction of the area.

Here is a view of the terrain to the south of the craters in the full image.

Photo credit: NASA/JPL/University of Arizona

Notes: This crater is located in Tempe Terra to the west of Chryse Planitia and to the north of Kasei Valles. The closest named crater is Sytinskaya. Also, for an mp4 video clip about this crater, including additional photographs, click here.

Greeley Haven in False Color on Opportunity's Eighth Anniversary

2012-01-27T00:00:00.002+08:00

This mosaic of images taken in mid-January 2012 shows the windswept vista northward (left) to northeastward (right) from the location where NASA's Mars Exploration Rover Opportunity is spending its fifth Martian winter, an outcrop informally named "Greeley Haven."

Opportunity's Panoramic Camera (Pancam) took the component images as part of full-circle view being assembled from Greeley Haven.

The view includes sand ripples and other wind-sculpted features in the foreground and mid-field. The northern edge of the the "Cape York" segment of the rim of Endeavour Crater forms an arc across the upper half of the scene.

Opportunity landed on Mars on January 25, 2004, Universal Time and EST (January 24, PST). It has driven 21.4 miles (34.4 kilometers) as of its eighth anniversary on the planet. In late 2011, the rover team drove Opportunity up onto Greeley Haven to take advantage of the outcrop's Sun-facing slope to boost output from the rover's dusty solar panels during the Martian winter.

Research activities while at Greeley Haven include a radio-science investigation of the interior of Mars, inspections of mineral compositions and textures on the outcrop, and monitoring of wind-caused changes on scales from dunes to individual soil particles.

The image combines exposures taken through Pancam filters centered on wavelengths of 753 nanometers (near infrared), 535 nanometers (green) and 432 nanometers (violet). The view is presented in false color to make some differences between materials easier to see.

Photo credit: NASA/JPL-Caltech/Cornell/Arizona State University

Note: For a true-color image of the same view, see PIA15281: Opportunity's Eighth Anniversary View From 'Greeley Haven'.

Sand Dunes in Noachis Terra

2012-01-26T00:00:00.004+08:00

Sand dunes are among the most widespread aeolian (wind-formed) features present on Mars. Their spatial distribution and morphology are affected by changes in wind direction and wind strength. Patterns of dune erosion and deposition provide insight into the sedimentary history of the surrounding terrain.

This image shows sand dunes trapped in an impact crater in Noachis Terra. Dunes and sand ripples of various shapes and sizes, such as in this enhanced-color subimage, show the natural beauty created by physical processes.

This is a stereo pair with ESP_024976_1375.

Photo credit: NASA/JPL/University of Arizona

Notes: This crater is located a very short distance due west of Hellespontus Montes, which is to the west of Hellas Planitia. Also, for an mp4 video clip of these dunes, with additional photographs, click here.

Many Fantastically Colorful Gullies in a Fresh Impact Crater

2012-01-23T00:00:00.004+08:00

This image covers a "fresh-looking" impact crater with a diameter of about 2 kilometers (1.2 miles).

There are gullies all around the steep inner slopes of this crater (you can even see them in the shadow by enhancing the brightness of this region), at 35 degrees South latitude. Many craters at this latitude in the southern hemisphere only have gullies on the south-facing slopes, which are shadowed in the wintertime. But this is an especially pristine crater so the slopes may be particularly steep and unstable.

The enhanced color sub image shows that gullies and their deposits have many different colors. This is due to diverse rock types exposed by the crater and the fact that the gullies have been recently active, so colors have not been homogenized by overlying regolith (soil) or windblown deposits. HiRISE will monitor this site in the future to see if the gullies are currently active.

How long ago did this crater form? It appears nearly pristine, preserving meter-scale morphologies in the ejecta, and there are almost no superimposed (younger) impact craters, so it is probably less than a million years old. That means the crater formed in the most recent 0.02 percent of Mars' existence. The ejecta includes a "herringbone" texture with V-shaped features pointing to the source crater.

Photo credit: NASA/JPL/University of Arizona

Note: This small crater is located in Bosporos Planum, just northeast of Aki Crater. Also, for an mp4 video clip of this impact crater, including additional information and photographs, click here.

Gullies in Bamberg Crater

2012-01-22T00:00:00.003+08:00

This cluster of gullies is on the wall of Bamberg Crater.

The impact crater has an extremely eroded and terraced rim. However, the gullies do not have extensive aprons and overall there appears to be very little material accumulated on the crater floor -- unlike many other craters with gullies. This may indicate the gullies are young features.

However, gully formation on Mars is still not completely understood, and more information and observations are needed to improve our interpretation of these features.

Photo credit: NASA/JPL/University of Arizona

Note: For an mp4 video clip of the gullies of Bamberg Crater, including additional information and photographs, click here.

Tongue-Shaped Flow Below a Scarp in Phlegra Montes

2012-01-21T00:00:00.003+08:00

This observation shows a tongue-shaped flow of material below a scarp in Phlegra Montes, a range of curving mountains and ridges on Mars.

This type of feature is sometimes formed by a debris flow, a landslide, or the flow of ice-rich material. However, the source of the material and how it was deposited here remains unclear.

Photo credit: NASA/JPL/University of Arizona

Note: For an mp4 video clip discussing the above-mentioned area, click here.

The Floor of Beer Crater

2012-01-20T00:00:00.003+08:00

This crater was named after German astronomer Wilhelm Beer. It is an ancient crater more than 100 kilometers across, located south of Meridiani Planum.

A full-resolution color sample shows fractured bedrock with dark sand filling low areas. The circular rocky features are probably eroded impact craters and the thin linear features are windblown deposits.

The aeolian (wind) erosion and modification of this ancient surface make it difficult to deduce how the rocks were initially emplaced, but the channeled rims suggest that these could be alluvial fans: deposits carried by flowing water (probably not beer).

Photo credit: NASA/JPL/University of Arizona

Note: For an mp4 video clip discussing the floor of Beer Crater, click here.

Search for Beagle 2 Lander

2012-01-16T00:00:00.003+08:00

This is the twelfth image from HiRISE in the part of Isidis basin where the British Beagle 2 spacecraft was supposed to land around Christmas time of 2003.

All contact was lost after its separation from the Mars Express spacecraft six days before atmospheric entry. The lack of telemetry on its way to the surface means there is little information about where the spacecraft may have landed on the surface--we can only search in the region where it was expected to land if the entry, descent, and landing (EDL) sequence had been nominal. EDL was probably not nominal, but perhaps the spacecraft did land correctly and failure occurred for some other reason.

Nothing resembling the Beagle lander has been seen in any of the HiRISE images, although we aren't sure that they've been thoroughly searched. For an idea of what the Beagle 2 hardware might look like, see this web page.

The easiest thing to spot would be the bright parachute, if it actually deployed. The parachutes are still easy to spot at the MER and Pathfinder landing sites, so dust deposition over the past eight years probably would not disguise the bright feature over equatorial regions of Mars. At high latitudes the brightness patterns are reset each winter by the seasonal deposits of carbon-dioxide and dust, as seen at the Phoenix landing site. However, beware of bright cosmic-ray hits.

EDL on Mars is difficult! Only the United States has succeeded, with Viking 1, Viking 2, Mars Pathfinder, Spirit, Opportunity, and Phoenix. The 1999 Mars Polar Lander was a failure, as was Beagle 2 and six landing attempts by the former Soviet Union. One of the Soviet landers, Mars 3, made it to the surface and transmitted some data or noise for 20 seconds before failure. We haven't been able to locate any of the Soviet lander hardware from HiRISE images.

Searching for this hardware is like looking for a needle in a really big haystack, and we don't know what the needle looks like. In August 2012 NASA will attempt to land the biggest rover ever sent to Mars, MSL or Curiosity. HiRISE will attempt to image MSL during descent, as it did for Phoenix, and after what is hopefully a successful landing.

Photo credit: NASA/JPL/University of Arizona

Banded Wall Outcrop in Ius Chasma

2012-01-15T00:00:00.002+08:00

This area was covered in a well-known MOC image of October 1997 (AB1-01303) that shows what appears to be layered rock, deep below the Martian surface.

At the time, this was considered to be revolutionary and seemed to contradict the general view of the upper crust of Mars as being a lunar-like "megaregolith." Later coverage of this outcrop area by MOC is not particularly good and the CTX (Context Camera) coverage doesn't improve on spatial resolution much.

However, experience with other HiRISE images suggests the "layering" will be less obvious at sub-meter-per-pixel scales, but nonetheless we'll see some interesting things. This was thought to be an important area for the development of some post-Viking views of Mars. This underscores how much technology has changed since the 1970s.

Photo credit: NASA/JPL/University of Arizona

Aram Chaos

2012-01-14T00:00:00.002+08:00

The southern cap rock in Aram Chaos is situated in the Martian equatorial region, to the east of the Tharsis region.

In Ancient Greek, "chaos" meant an emptiness or void, the gap that existed between the heavens and the earth; here, we use the word to describe terrain that is jumbled and "confused." As the image shows us, Aram Chaos is actually a heavily eroded impact crater, with material on the floor that is blocky in contrast to some of the surrounding terrain.

This would be an interesting area to explore and to send a rover, because we think that water might have existed in the underground as ice.

Photo credit: NASA/JPL/University of Arizona

Defrosting Barchan Dunes

2012-01-13T00:00:00.003+08:00

This HiRISE image shows sand dunes near the eastern part of North Polar erg.

The dunes imaged here are similar to barchan dunes, commonly found in desert regions on Earth. Barchan dunes are generally crescent-shaped with a steep slip face bordered by horns oriented in the downwind direction. Barchan dunes form by winds blowing mainly in one direction and thus are good indicators of the dominant wind direction when the dunes formed.

The dunes and surrounding surface appear bright because they are covered with seasonal frost left over from the northern hemisphere winter. Sunlight is now falling on the North Polar region, and carbon dioxide frost that accumulated during winter is sublimating (going directly from solid to gas) and the surface beneath the frost is being revealed.

Composed primarily of basaltic sand, the dunes will appear dark during the northern hemisphere summer. The dark spots are areas where some of this frost has begun to sublime away, and/or where wind has exposed the underlying dark sand.

Photo credit: NASA/JPL/University of Arizona

Note: This image is located west of Olympia Mensae, and north of Louth Crater. I am not quite sure what "north polar erg" the author is referring to in the first sentence. The eastern end of the primary north polar erg, Olympia Undae, is actually on the other side of the planet. This location is much closer to the western end of Olympia Undae, although that is still some distance away. Personally, I would say that the image location is in Vastitas Borealis.

Floral-Shaped Volcano on Cerberus Fossae

2012-01-11T00:00:00.001+08:00

This is a small volcano superposed on the flanks of a larger one of the Cerberus Tholi.

This smaller feature has a single vent, aligned along a Cerberus Fossae trough, and it has flows radiating away from this vent in all directions, somewhat looking like a flower.

These flows appear somewhat darker than their surroundings, though this might be owing to roughness as much as to relative youth. Note that even at Context Camera (CTX) scale, we can see that there are some small impact craters superimposed on this feature, indicating that it is not entirely young.

This is a stereo pair with ESP_023811_1880.

Photo credit: NASA/JPL/University of Arizona

Note: Cerberus Tholi is a group of seven volcanic hills located in Elysium Planitia. Cerberus Tholi is located south of the eastern end of Cerberus Fossae, and roughly encircle Tombaugh Crater.

Transverse Aeolian Ridges in Proctor Crater

2012-01-10T00:00:00.003+08:00

Transverse Aeolian Ridges (or TARs) are small aeolian bedforms that are distinct from typical dunes or ripples. TARs are found all over Mars, and are typically located near layered terrains, or near fields of large dark dunes as they are here in Proctor Crater in the southern hemisphere.

TARS form transverse (perpendicular) to the wind direction and are thought to be composed of coarse-grained material. They also appear to be indurated (hardened) and may be much less mobile than the larger dunes.

This is a stereo pair with ESP_024515_1320.

Photo credit: NASA/JPL/University of Arizona

Lava Flow Oozing into a Crater

2012-01-09T00:00:00.018+08:00

This image captures a fairly rare situation. In general, as lava flows along, it fills in low points and holes it encounters in its path and flows around high points such as hills and ridges. In this image there are two lava flows interacting with an impact crater.

Although an impact crater approximately 3 kilometers (1.8 miles) wide such as this is a deep hole in the ground (likely a couple hundred meters or several hundred feet deep), it is surrounded by a rim crest that is actually higher than the surrounding terrain, lifted up during the powerful impact that formed the crater originally. On the south side of the crater, a smooth-surfaced lava flow (with some knobs in the southwest) has come in contact with the exterior of the crater rim, burying any sign of ejecta from the crater and covering most of the rim, almost up to the rim crest.

However, because the height of the crater rim was slightly greater than the thickness of the lava flow, the crater rim acted like a wall and prevented the deep crater from being overrun and filled with the lava. Later, however, a different, younger, heavily ridged lava flow approached the crater from the north - the thickness of this ridged lava flow is visible along its flow front in the eastern part of the image. Unlike the earlier flow, the ridged flow overtopped the crater's northeast rim, and a single lobe of lava is descending to the floor of the crater. If the rim had been any lower, or if the lava had advanced any further, the crater would have been filled and buried and we would not be lucky enough to see this snapshot of the dramatic interaction of lava with this crater.

By studying how lava reacts to obstacles and to variation in slope, like this lobe falling down the crater's inside wall, scientists may be able to learn about the thickness, viscosity (or stickiness), and strength of the lava flow, which in turn could help constrain the composition and temperature of the lava.

This is a stereo pair with ESP_024877_1465.

Photo credit: NASA/JPL/University of Arizona

Note: The location of this image is in far northeastern Terra Sirenum, northwest of Pickering Crater.

What is This Stuff?

2012-01-08T00:00:00.003+08:00

This image covers plains near Aureum Chaos. A puzzling ridged texture was first seen in an image from the Context Camera on MRO, leading to this suggestion for a HiRISE image.

In this image we can see much detail, but the origin of the surface texture is still puzzling. The enhanced color subimage helps to correlate rock units, but is also puzzling.

Here's a hypothetical geologic history that might explain this scene: layered sediments were deposited by water or airfall (including volcanic pyroclastics). A crudely polygonal patterned ground was created by stresses in the sediments, and groundwater followed the fractures and deposited minerals that cemented the sediments. This was followed by perhaps billions of years of erosion by the wind, leaving the cemented fractures as high-standing ridges.

Of course, this story is almost certainly incomplete if not totally wrong.

Photo credit: NASA/JPL/University of Arizona

Greeley Haven in False Color

2012-01-07T00:00:00.003+08:00

This mosaic was acquired by the Mars Exploration Rover Opportunity's Panoramic Camera (Pancam) on Sol 2793 (December 2, 2011). It shows a north-facing outcrop, informally named "Greeley Haven," where Opportunity will work during the rover's fifth Martian winter. The rover team chose this designation as a tribute to the influential planetary geologist Ronald Greeley (1939-2011), who was a member of the science team for the Mars rovers and many other interplanetary missions.

The site is of interest not only for its geologic features but because it has favorable northerly slopes to optimize Opportunity's solar energy as winter approaches in the southern hemisphere of Mars. After this mosaic was acquired, Opportunity backed up the slope to park at approximately 16 degrees northerly tilt and used tools on its robotic arm (Instrument Deployment Device, or IDD) to examine rock and soil targets. After deciding that the site could serve the mission well for the next several months, the team designated it as a memorial for Greeley, who taught generations of planetary scientists at Arizona State University, Tempe, until his death on October 27, 2011.

The site is near the northern tip of the "Cape York" segment of the western rim of Endeavour Crater.

The image combines exposures taken through Pancam filters centered on wavelengths of 753 nanometers (near infrared), 535 nanometers (green) and 432 nanometers (violet). The view is presented in false color to make some differences between materials easier to see.

Plans for research continuing through the months at Greeley Haven include a radio-science investigation of the interior of Mars, inspections of mineral compositions and textures on the outcrop, and assembly of a full-circle, color panorama of the surroundings. The planned full-circle image will be called the Greeley Panorama.

Photo credit: NASA/JPL-Caltech/Cornell/Arizona State University

Note: For other pictures in this series, see PIA15118: Approaching 'Greeley Haven' on Endeavour Rim, PIA15119: 'Greeley Haven' Site for Opportunity's Fifth Martian Winter and PIA15276: Locator Map for 'Greeley Haven' on Endeavour Rim.

Valley in Ismenius Lacus Region

2011-12-23T00:00:00.002+08:00

A valley extends across the center of the image, and a tributary joins it from the north, while another branch connects from the south. This branch--which resembles half of a crater--is really just a bend in the channel, much more incised than the muted valley going across the scene.

There is evidence of mass wasting (gravity moving dry materials off high-standing regions onto low-lying regions), visible where a series of ridges appear to be piling up near the floor of the bend.

The terrain surrounding the valley has craters of a range of ages, judging by their different states of degradation. One small fresh crater near the right side of the image has dark, high-standing rays extending from it. A larger more degraded crater is located in the bottom third of the image. A great deal of material has flowed off the crater walls into its center. It is likely that ground ice aided the movement of this material.

Photo credit: NASA/JPL/University of Arizona

Note: The location of this image, Ismenius Lacus, lies in the larger region of Arabia Terra and is located northeast of Cerulli Crater.

Radargram of Mars' North Polar Plateau

2011-12-21T00:00:00.006+08:00

The upper panel is a radargram profile from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), showing data from the subsurface of Mars in the ice-rich north polar plateau of Mars. It shows layers detected to a depth of about 1.5 miles (2.7 kilometers) beneath the surface in a transect about 930 miles (1,500 kilometers) long. A basal unit of a sand- and dust-rich icy material comprises more than half of the bulk of the polar plateau in this radargram profile. Its base can be traced from beneath the Olympia Undae sand sea at left, across the entire polar stack, to the margin of the Rupes Tenuis plateau at right, where there are no overlying north polar layered deposits (NPLD). The vertical dimension is time delay of radio-signal echo. The apparent deepening of the basal unit's lower boundary at the center is an artifact of the slowing of the radar wave in the icy material. In fact, the lower boundary is nearly flat.

The lower panel shows the path of the spacecraft ground track while these radar observations were being made, on a topographical map derived from Mars Orbiter Laser Altimeter data. Total relief in the topography from highest (red) to lowest (purple) is 1.7 miles (2.7 kilometers).

Image credit: ESA/NASA/JPL-Caltech/Univ. of Rome/ASI/GSFC

Note: For more information, see MARSIS Completes Measurement Campaign Over Martian North Pole.

Faults in Ius Chasma

2011-12-19T00:00:00.000+08:00

Ius Chasma is one of many steep-sided interconnected depressions (chasmata) that comprise Valles Marineris, the largest canyon system in the Solar System.

The chasma is approximately 900 kilometers long and is located in western Valles Marineris. The floor of Ius Chasma is between 8 to 10 kilometers deep and is divided by a prominent east-west trending ridge known as Geryon Montes.

The region in this image is located (approximately 7.8 degrees South, 279.5 degrees East) on the floor of Ius Chasma. A variety of light and medium-toned terrains and layered units of different rock types comprise the chasma floor. Prominent faults of various sizes have displaced and deformed these layered units and outcrops, some in a spectacular fashion.

The ejecta of small fresh-appearing impact craters formed in the light-toned units reveal the existence of a darker (likely basaltic) underlying substrate. Linear dunes are located on top of the lighter-tone outcropping units and are ubiquitous on the chasma floor. These dunes are oriented in a north-south direction and indicate prevailing westerly winds through the canyon.

Photo credit: NASA/JPL/University of Arizona

Fresh Crater North of Tharsis Region

2011-12-18T00:00:00.002+08:00

This impact crater is approximately one kilometer in diameter. The ejecta blanket (remnants of the material from the original impact) is still visible indicating that the crater may be very fresh.

But what do we mean by the word "fresh," or even "recent," as some craters are described? When talking about craters on Mars, both terms are relative: the impact that created the crater in this observation could have occurred millions of years ago! We can often differentiate between older and younger craters by looking at their rims. A crater rim that appears more defined or sharp, versus one that is clearly eroded, indicates the former is more recent, or "fresh."

The Tharsis region on Mars is home to some of the largest shield volcanoes on the Red Planet, including the largest, Olympus Mons.

This is a stereo pair with ESP_019140_2310.

Photo credit: NASA/JPL/University of Arizona

Layering in Central Candor Chasma

2011-12-17T00:00:00.001+08:00

This HiRISE image shows faulted layered deposits in a part of Valles Marineris called Candor Chasma.

Often faults cut through the layered material in this area, indicating that the rocks underwent stress causing them to crack and shift in position after they were deposited.

This area also has a high abundance of hematite. Hematite is a mineral that can precipitate out of water, so its presence on Mars is of special interest for understanding the distant past.

Photo credit: NASA/JPL/University of Arizona

Spring Fans Bursting from Cracks in Ice

2011-12-16T00:00:00.001+08:00

Sand dunes in the north polar region of Mars are covered every winter by a layer of carbon dioxide ice (dry ice). In the springtime the ice on the dunes cracks, often in polygonal patterns.

Once the ice layer has cracked the sand below can escape. It may be blown downwind, landing in fan-shaped deposits on top of the seasonal layer of ice. It may also slide down the sides of the dunes, often the case when the ice ruptures at the crest of the dune.

Photo credit: NASA/JPL/University of Arizona

Note: This image is located in Olympia Undae to the northeast of Dokka Crater.

Crater in Utopia Rupes

2011-12-14T00:00:00.002+08:00

The objective of this observation is to examine features of a mid-latitude crater.

In the Context Camera (CTX) image (P18_008030_2217) of this area, the crater floor has hollows and a high density of pits. The wall has the shape of the alcoves of gullies with the lower part covered up. Perhaps this crater once had gullies, but is now filled up.

Photo credit: NASA/JPL/University of Arizona

Note: This crater is located in the Utopia Rupes region of western Utopia Planitia.

Meanders and Tributaries in Ridge Form in the Zephyria Region

2011-12-13T00:00:00.002+08:00

This observation reveals two obvious features. The smaller, narrow ridges oriented vertically are yardangs, which are created by wind erosion; the wind strips away the surrounding terrain, and the ridges remain because they contain more hardened material.

The second feature—the inverted, meandering channel snaking through the image—is caused by similar processes. This was once a river bed that meandered due to changes in topography. As the river flowed, sediments were deposited on its floor, and over time, these sediments became hardened, so when the wind later stripped away the surrounding terrain, the hardened sediments remained, leaving an inverted form.

Photo credit: NASA/JPL/University of Arizona

Interacting Fossae Segments East of Athabasca Valles

2011-12-12T00:00:00.002+08:00

Athabasca Valles starts suddenly along the Cerberus Fossae and flows southwest for approximately 400 kilometers. The source region is divided into two lobes, each roughly centered on the fossae.

Understanding the possible volume and flux of water in the ancient past may help in learning how the flood channel formed.

Photo credit: NASA/JPL/University of Arizona

Shoemaker Ridge

2011-12-11T00:00:00.001+08:00

The feature informally named "Shoemaker Ridge" in the "Cape York" segment of the western rim of Endeavour Crater includes outcrops that are likely impact breccias. Impact breccias are a type of jumbled rock previously examined by NASA's Mars Exploration Rover Opportunity at the "Chester Lake" target on Cape York. The view looks northward toward the southern edge of Shoemaker Ridge.

This image combines exposures taken by Opportunity's Panoramic Camera (Pancam) through three different color filters during the 2,715th Martian day, or sol, of the rover's work on Mars (September 13, 2011). It is presented in false color to emphasize differences among materials in the rock and soil. The filters used are centered on wavelengths of 753 nanometers (near infrared), 535 nanometers (green) and 412 nanometers (violet).

Most of Cape York is covered in densely packed basaltic sands with small embedded rock clasts. Outcrops are exposed particularly on the inboard, or southeast, side of the cape. The name Shoemaker Ridge pays tribute to one of the founding fathers of planetary geology, Eugene Shoemaker.

Photo credit: NASA/JPL-Caltech/Cornell/Arizona State University

Note: An annotated version of the above image can be found here.

Homestake Vein

2011-12-10T00:00:00.006+08:00

This false-color view of a mineral vein called "Homestake" comes from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity. The vein is about the width of a thumb and about 18 inches (45 centimeters) long. Opportunity examined it in November 2011 and found it to be rich in calcium and sulfur, possibly the calcium-sulfate mineral gypsum.

"Homestake" is near the edge of the "Cape York" segment of the western rim of Endeavour Crater.

Exposures combined into this view were taken through Pancam filters admitting light with wavelengths centered at 753 nanometers (near infrared), 535 nanometers (green) and 432 nanometers (violet). The view is presented in false color to make some differences between materials easier to see.

The exposures were taken during the 2,769th Martian day, or sol, of Opportunity's career on Mars (November 7, 2011).

Photo credit: NASA/JPL-Caltech/Cornell/ASU

Note: For other pictures of Homestake Vein, see PIA15033: 'Homestake' Vein in Color, PIA15035: Close-up View of 'Homestake' Vein, PIA15036: Western Edge of 'Cape York,' with Bright Vein and http://photojournal.jpl.nasa.gov/catalog/PIA15037. Also, see the NASA Science News article, "Slam Dunk" Sign of Ancient Water on Mars.

Dunes in Vastitas Borealis

2011-12-09T00:00:00.001+08:00

This scene is from early spring in the northern hemisphere of Mars. These barchan dunes are covered with a layer of seasonal carbon dioxide ice (dry ice). Bluish cracks in the ice are visible across the top of some of the dunes.

Dark fan-shaped deposits around the edges of the dunes are at spots where the ice has sublimated (gone directly from ice to gas) and the ice layer has ruptured, allowing the sand from the dune to escape out from under the ice. The sand is then free to be blown by the wind.

This image is one product from an observation by the High Resolution Imaging Science Experiment (HiRISE) camera taken on September 30, 2011, at 73.3 degrees north latitude, 355.1 degrees east longitude. Other image products from the same observation are at http://www.uahirise.org/ESP_024265_2535.

Photo credit: NASA/JPL-Caltech/University of Arizona

Remnant of Unconformable Deposit in Electris

2011-12-06T00:00:00.002+08:00

The Electris region of Mars contains some interesting features, such as the raised-relief blocks of material visible in this image.

One goal of this observation is to try to determine the origin of what's called the "mantling deposit." How was this deposit placed here? What types of geologic processes have acted to form the deposit? An image at high resolution can help provide details on the thickness and subtle variations within this deposit that can give us information on its origin and what erosional processes it has experienced.

This is a stereo pair with ESP_024074_1425.

Photo credit: NASA/JPL/University of Arizona

Note: This image lies in the midst the of the Gorgonum Chaos, which is in Terra Sirenum.

Phlegra Montes

2011-12-05T00:00:00.002+08:00

Phlegra Montes is a range of gently curving mountains and ridges on Mars. They extend from the northeastern portion of the Elysium volcanic province to the northern lowlands. The High-Resolution Stereo Camera on ESA’s Mars Express collected the data for these images on 1 June 2011 during orbit 9465. This perspective view has been calculated from the Digital Terrain Model derived from the stereo channels.

Photo credit: ESA/DLR/FU Berlin (G. Neukum)

Gullies in Acidalia Planitia

2011-12-04T00:00:00.002+08:00

This observation covers gullies that were previously identified in the walls of a crater in a MOC image (E0502675).

Do these gullies have features that can be interpreted as characteristic of snow and/or ice melting? At HiRISE resolution, questions like this can possibly be answered.

HiRISE often re-images areas to track seasonal changes, so we expect to monitor these gullies for changes at intervals during several Mars years.

Photo credit: NASA/JPL/University of Arizona

Note: These gullies are in a crater in Acidalia Planitia, to the northeast of Gamboa Crater.

Gully and Dunes

2011-12-03T00:00:00.000+08:00

An earlier observation (ESP_019969_1215) of the same area shows a very interesting feature: a defrosting gully and dunes, with distinct defrosting spots along the gully channel.

Since HiRISE can re-image certain areas over time, this area seems like a worthwhile place to monitor the defrosting process and hopefully gain a deeper understanding of it. This observation was taken at the end of southern summer and will serve as a baseline for observing the gully defrosting next southern spring.

Photo credit: NASA/JPL/University of Arizona

Note: This image is taken in an unnamed crater southwest of Argyre Planitia.

Bright and Dark Terrain in Noctis Labyrinthus

2011-12-02T00:00:00.001+08:00

This image shows the transitional terrain where the linear troughs and rounded pits of Noctis Labyrinthus merge with the larger chasmata of Valles Marineris. Unusual bright blocks can be seen beneath a layered dark mantle.

The bright blocks also have some layering and show hydration features in CRISM spectra. The bright blocks are jagged and irregular in shape, perhaps because they represent impact material or because they are partially obscured beneath a dark mantle so we cannot see their full extent.

The dark mantle consists of aeolian (wind-driven) material (as evidenced by linear ripples) as well as a finely layered unit. The dark layered mantle does not show any hydration features in CRISM spectra so perhaps it represents multiple events of wind deposition where each time this material was laid down it became a distinct layer.

This is a stereo pair with PSP_006692_1740.

Photo credit: NASA/JPL/University of Arizona

Cross Section of Gale Crater

2011-12-01T00:00:00.000+08:00

This artist's impression of Mars' Gale Crater depicts a cross section through the mountain in the middle of the crater, from a viewpoint looking toward the southeast. The rover Curiosity of NASA's Mars Science Laboratory mission will land in Gale Crater in August 2012. The landing area is on or near an alluvial fan indicated in blue. A key factor in selection of Gale as the mission's landing site is the existence of clay minerals in a layer near the base of the mountain, within driving range of the landing site. The location of the clay minerals is indicated as the green band through the cross section of the mountain. The image uses two-fold vertical exaggeration to emphasize the area's topography. The crater's diameter is 96 miles (154 kilometers).

The image combines elevation data from the High Resolution Stereo Camera on the European Space Agency's Mars Express orbiter, image data from the Context Camera on NASA's Mars Reconnaissance Orbiter, and color information from Viking Orbiter imagery.

Image Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS

Changes in the Tilt of Mars' Axis

2011-11-30T00:00:00.001+08:00

Modern-day Mars experiences cyclical changes in climate and, consequently, ice distribution. Unlike Earth, the obliquity (or tilt) of Mars changes substantially on timescales of hundreds of thousands to millions of years. At present day obliquity of about 25-degree tilt on Mars' rotational axis, ice is present in relatively modest quantities at the north and south poles (top left). This schematic shows that ice builds up near the equator at high obliquities (top right) and the poles grow larger at very low obliquities (bottom) (References: Laskar et al., 2002; Head et al., 2003).

Illustration credit: NASA/JPL-Caltech

Topography of Gale Crater

2011-11-29T00:00:00.002+08:00

Color coding in this image of Gale Crater on Mars represents differences in elevation. The vertical difference from a low point inside the landing ellipse for NASA's Mars Science Laboratory (yellow dot) to a high point on the mountain inside the crater (red dot) is about 3 miles (5 kilometers).

Image credit: NASA/JPL-Caltech

Eberswalde Crater

2011-11-28T00:00:00.000+08:00

Eberswalde crater on Mars formed more than 3.7 billion years ago. The rim of the crater is intact only in the north-eastern part. The rest has been buried by ejecta from the larger, more recent Holden impact crater nearby. The image was acquired by Mars Express around 25°S/326°E during orbit 7208 on 15 August 2009. The images have a ground resolution of about 22m per pixel.

Photo credit: ESA/DLR/FU Berlin (G. Neukum)

Launch of the Mars Science Laboratory ("Curiosity")

2011-11-27T01:00:00.001+08:00

I need to get to bed, but I first wanted to add two videos of the Mars Rover Curiosity launching successfully from Cape Canaveral today. Captions for the videos will come later. This first video is from NASAtelevision:

This second video is a much longer version:

Buried Ice Under Fresh Crater

2011-11-27T00:00:00.002+08:00

Recent small craters discovered by the High Resolution Imaging Science Experiment camera on NASA's Mars Reconnaissance Orbiter expose buried ice in the middle latitudes of Mars. This ice is a record of past climate change. Not stable today, it was deposited during a period of different obliquity, or tilt, of the planet's axis.

This image is one product from HiRISE observation ESP_011337_2360.

Photo credit: NASA/JPL-Caltech/Univ. of Arizona

Notes: This crater was formed in 2008. In the larger images of the area taken by HiRISE (see the link above), the crater appears as a tiny white splotch. In the image shown above, the other tiny craters are presumably secondary craters caused by ejecta from the primary (large) impact crater.

Nirgal Vallis

2011-11-26T12:00:00.000+08:00

This view of channels on Mars came from NASA's Mariner 9 orbiter. In 1971, Mariner 9 became the first spacecraft to enter orbit around Mars.

Photo credit: NASA/JPL-Caltech

Note: Obviously, as the note on the photograph mentions, this image is of part of Nirgal Vallis.

Clay Minerals in Mawrth Vallis

2011-11-26T00:00:00.002+08:00

Thick stacks of clay minerals indicate chemical alteration of thick stacks of rock by interaction with liquid water on ancient Mars. Aluminum clays overlying iron/magnesium clays here in the ancient terrains of Mawrth Vallis indicate a change in environmental conditions. Aluminum clays may form by near-surface leaching while iron/magnesium clays may form in the subsurface. The image is from the High Resolution Imaging Science Experiment camera on NASA's Mars Reconnaissance Orbiter. (References: Wray et al., 2008; Loizeau et al., 2010.)

Photo credit: NASA/JPL-Caltech/University of Arizona

Sulfates and Clays in Columbus Crater

2011-11-25T00:00:00.000+08:00

Sulfates are found overlying clay minerals in sediments within Columbus Crater, a depression that likely hosted a lake in the past. Sulfate salt deposits ring the crater like a bathtub ring and were deposited after the clays, as the lake dried out. The image combines information from two instruments on NASA's Mars Reconnaissance Orbiter, the Compact Reconnaissance Imaging Spectrometer for Mars and the Context Camera. (Reference: Wray et al., 2011.)

Photo credit: NASA/JPL-Caltech/MSSS/JHU-APL

Topography of Mars

2011-11-24T00:00:00.001+08:00

Color coding in this image of Mars represents differences in elevation, measured by the Mars Orbiter Laser Altimeter on NASA's Mars Global Surveyor. While surface liquid water is rare and ephemeral on modern Mars, the topography of Mars reveals large, ancient valley networks and outflow channels. These are evidence that liquid water was more common and played a much more important role in Mars' past.

Image credit: NASA/JPL-Caltech

Note: The view of this map is somewhat unusual; we are looking from the north to the south. The "blue land" to the left is Acidalia Planitia (dark blue) and Chryse Planitia (light blue). The "green land" on the far left limb is Arabia Terra, while the green and yellow land to the middle right is Lunae Planum (lower right) and Xanthe Terra (upper middle right, with the large craters). The long blue and green streak in the "red land" is Valles Marineris; that leads to the various chasmata and chaotic terrains that lie near the top (southernmost) limb of the planet. The green "dogleg" at the bottom right is Echus Chasma (far right) and Kasei Valles (middle right), which flowed into Chryse Planitia.

Moving Sand Dunes in the Martian North Polar Region

2011-11-21T00:00:00.001+08:00

A dune in the northern polar region of Mars shows significant changes between two images taken on June 25, 2008 and May 21, 2010 by NASA's Mars Reconnaissance Orbiter. This motion includes landslides and sand advancing at the dune front (upper left); changes in the position of the rest of the dune boundary relative to the fixed, underlying terrain; and changes in the position of ripples on the dune surface.

This is one of several sites where the orbiter has observed shifting sand dunes and ripples. Previously, scientists thought sand on Mars was mostly immobile. It took the mission's High Resolution Imaging Science Experiment (HiRISE) to take sharp enough images to finally see the movement.

While dust is easily blown around the Red Planet, its thin atmosphere means that strong winds are required to move grains of sand.

Photo credit: NASA/JPL-Caltech/University of Arizona/JHUAPL

Note: For an animated GIF file that shows the movement of the sand dunes over time, see here. I am not sure exactly where this image is located other than the very generic "northern polar region," so I am not attempting to link to any specific location.

Blowing in the Martian Wind

2011-11-20T00:00:00.000+08:00

A rippled patch of sand in Becquerel Crater on Mars moved about two meters (about two yards) between November 24, 2006 and September 5, 2010, as observed in these images taken by NASA's Mars Reconnaissance Orbiter. The white line tracks the displacement between two ripples. Becquerel Crater is located just north of the equator in the Arabia Terra region.

This is one of several sites where the orbiter has observed shifting sand dunes and ripples. Previously, scientists thought sand on Mars was mostly immobile. It took the mission's High Resolution Imaging Science Experiment (HiRISE) to take sharp enough images to finally see the movement.

While dust is easily blown around the Red Planet, its thin atmosphere means that strong winds are required to move grains of sand.

Photo credit: NASA/JPL-Caltech/University of Arizona/JHUAPL

Note: For an animated GIF file that shows the movement of the sand over time, see here.

MAVEN

2011-11-19T12:00:00.000+08:00

This artist's concept depicts NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft near Mars. MAVEN is in development for launch in 2013 and will be the first mission devoted to understanding the Martian upper atmosphere. The mission's principal investigator is Bruce Jakosky from the Laboratory for Atmospheric and Space Physics at the University of Colorado.

The goal of MAVEN is to determine the role that loss of atmospheric gas to space played in changing the Martian climate through time. MAVEN will determine how much of the Martian atmosphere has been lost over time by measuring the current rate of escape to space and gathering enough information about the relevant processes to allow extrapolation backward in time.

Illustration credit: NASA

Rippling Dune Front in Herschel Crater

2011-11-19T00:00:00.003+08:00

A rippled dune front in Herschel Crater on Mars moved an average of about two meters (about two yards) between March 3, 2007 and December 1, 2010, as seen in these images from NASA's Mars Reconnaissance Orbiter. Note that the pattern of ripples on the dune surface has changed completely between the two images. Herschel Crater is located just south of the equator in the cratered highlands.

This is one of several sites where the orbiter has observed shifting sand dunes and ripples. Previously, scientists thought sand on Mars was mostly immobile. It took the mission's High Resolution Imaging Science Experiment (HiRISE) to take sharp enough images to finally see the movement.

While dust is easily blown around the Red Planet, its thin atmosphere means that strong winds are required to move grains of sand.

Photo credit: NASA/JPL-Caltech/University of Arizona/JHUAPL

Notes: For an animated GIF file that shows the movement of the dune over time, see here. Also, for more pictures, including animated GIFs of shifting sand dunes in Herschel Crater, see PIA14877: Shifting Sand in Herschel Crater and PIA14879: Rippling Dune Front in Herschel Crater on Mars.

Wrinkle Ridges in Eastern Meridiani Planum

2011-11-16T00:00:00.003+08:00

This wrinkle ridge crosses through a mound of layered material that's been exposed by erosion.

This observation poses an excellent opportunity to look at the internal structure of a wrinkle ridge. We can compare the topography and internal structure of this wrinkle ridge at this location to exposures in other terrain to see if the local bedrock has a noticeable effect on ridge morphology or growth.

The layers also represent stratigraphic markers that we know were once continuous - examining faults that cross-cut and offset layers can yield good information about the amount and direction of movement that took place along that fault.

This is a stereo pair with ESP_020850_1845.

Photo credit: NASA/JPL/University of Arizona

Note: This image is located in eastern Meridiani Planum; the closest named feature to this site is Schiaparelli Crater to the southeast.

Light-Toned Layered Rocks in Arabia and East Xanthe Regions

2011-11-15T00:00:00.002+08:00

The banding in this image has been interpreted based on MOC images to be layering. A critical goal of this observation is to provide points of comparison with HiRISE full resolution coverage and CRISM infrared spectra of light-toned rock outcrops in other areas of the Mawrth Vallis region.

The dark terrain at the north end of the image is heavily cratered and has thus been there (at the surface) longer than the brighter terrain in the rest of the image. But is it older, as heavily cratered terrain often indicates?

The dark terrain appears to be higher in elevation, which in layered terrain usually means that it is actually younger than the bright terrain (lower layers are deposited first). One possibility is that the bright terrain used to be covered with the darker material also, but that that darker material has been stripped off and removed, revealing the brighter layers and terrain below. If this is indeed the case, then the low bright terrain could actually be older and it has fewer craters only because it has been more recently exposed to the surface. Clues to this are small high-standing knobs throughout the bright terrain that could be remnants of once more-widespread higher topography.

Also, the larger circular to oval patches, or "islands" of smooth dark material within the bright material are also high-standing. They may be old impact craters, exterior to which erosion has removed dark terrain, but interior to which the crater walls or some hardening process has protected the dark terrain from erosion. Such terrain is called "inverted topography" because a crater depression which was once empty and low has become filled, and the material outside of the crater has been removed while the material inside the crater hasn't - producing relief opposite to that of the original landscape.

Photo credit: NASA/JPL/University of Arizona

Gullies and Lobate Material in a Crater in the Nereidum Montes

2011-11-14T00:00:00.001+08:00

This image includes a crater that has been heavily influenced by later geologic processes.

First of all, terrain-altering or -burying processes have eliminated much of the pattern of ejecta that surrounds fresh craters. The crater also appears fairly flat-floored with short walls (not very deep) for its size, indicating material has filled it in. These modifying effects may be due to deposition and activity of ice-rich or other mantling sediments deposited at some point in the past.

Finally, the crater clearly exhibits gullies starting on its northern wall and extending to its center. The arc-shaped ridge inside the southern edge of the crater, partially buried by the filling material, is particularly curious - it could be a wind-caused or other accumulation of crater-fill material.

One of the rationales for acquiring an image of this location is to investigate the relationship between these features; HiRISE's full resolution can provide better details of the terrain.

Photo credit: NASA/JPL/University of Arizona

Note: This crater lies in the Nereidum Montes, which is the mountainous terrain to the northwest of Argyre Planitia.

Tharsis Tholus

2011-11-13T00:00:00.003+08:00

Tharsis Tholis towers 8 km above the surrounding terrain with a base that stretches 155 x 125 km and a central caldera measuring 32 x 34 km. The image was created using a Digital Terrain Model (DTM) obtained from the High Resolution Stereo Camera on ESA’s Mars Express spacecraft. Elevation data from the DTM is color-coded: purple indicates the lowest lying regions and beige the highest. The scale is in meters. In these images, the relief has been exaggerated by a factor of three.

Photo credit: ESA/DLR/FU Berlin (G. Neukum)

Note: For more information (and a lot of other, great images), see Battered Tharsis Tholus Volcano on Mars.

Mars Science Laboratory atop the Atlas V

2011-11-12T00:00:00.000+08:00

In the Vertical Integration Facility at Space Launch Complex 41, the payload fairing containing NASA's Mars Science Laboratory spacecraft was attached to its Atlas V rocket on November 3, 2011.

The spacecraft was prepared for launch in the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center. Its components include a car-sized rover, Curiosity, which has 10 science instruments designed to search for evidence about whether Mars has had environments favorable to microbial life, including the chemical ingredients for life.

Launch of the Mars Science Laboratory aboard a United Launch Alliance Atlas V rocket is planned for November 25 from Space Launch Complex 41 on Cape Canaveral Air Force Station.

Lava Coating, Flood-Carved Kasei Valles

2011-11-11T00:00:00.000+08:00

This HiRISE image covers a small part of the gigantic 1,780 kilometer (1,100 mile long) set of flood-carved channels on Mars called Kasei Valles. The focus of this image is a much narrower channel that was cut into the floor of the large channel system.

It is interesting to compare this lava-coated channel to a similar feature called Athabasca Valles. Both channels appear to have been cut by a flood of some fluid, and then coated with a thin layer of lava. In the case of Athabasca Valles, the fluid that carved the channel and the lava came out of the same fissure in the ground. Every channel is completely coated with lava, allowing the possibility that Athabasca Valles was carved by lava.

However, at Kasei Valles, the lava and the flood carving fluid came from two different places. The valleys were carved by floods, presumably of very muddy water, released from Echus Chasma. The lava in Kasei Valles only coats the lowermost part of the huge valleys and comes from a source between the huge Tharsis volcanoes.

As HiRISE collects more images, we are able to expand our understanding of Mars by comparing and contrasting key features.

Photo credit: NASA/JPL/University of Arizona

Avalanche at Olympia Rupes

2011-11-07T00:00:00.002+08:00

Since HiRISE first started finding avalanches on Mars, we have continued searching for them in the most likely places: steep cliffs at the edges of the layered deposits at the North Pole.

These layers are exposed in the scarp face that cuts through them diagonally across this subimage. The bright smoother material at the lower left is at the top of the cliff, and here we have caught another avalanche as it falls down the steep slope towards the upper right of the image.

A large (approximately 200 meters or 600 feet across) cloud of reddish dust has been kicked up at the base of the scarp. Fine tendrils of bright wisps are visible farther up the cliff face—these may be individual falls of material, before spreading out as the avalanche plummets downward.

This might allow scientists to figure out the exact location of the start of the avalanche; for example, which layer it originally came from and how far it fell. This information will help narrow down what triggers these falls: is it seasonal temperature changes in the ice layers, gusts of wind passing over loosened rocks in steep slopes, or something else entirely?

In the upcoming season of spring in the northern hemisphere, HiRISE will be searching for even more of these events in order to better understand when and where they happen, and why.

Photo credit: NASA/JPL/University of Arizona

Note: The above image is taken along the long Olympia Rupes that is at the edge of Planum Boreum. The closest named feature is Puyo Crater, which lies to the southwest of this image.

Rafting Rocks

2011-11-06T00:00:00.002+08:00

This image shows some interesting features where smoother, dark areas with straight sides are separated by narrow channels of higher material.

This is especially clear in the southern portion of the image (rotated so north is at approximately 11 o'clock, 3.2 kilometers or 2 miles across). It looks as if a flat solid surface broke up, and then the individual pieces were rafted apart.

In other areas of Mars, similar features formed when a layer of lava solidified on top of still-molten rock. The solid layer at the surface broke apart either when it contracted as it cooled, or when the liquid below it flowed and dragged along the bottom of the top layer of solid rock.

However, this area of the Hellas basin is not expected to have any volcanic activity. Hellas is a huge, old impact crater, filled with sediments and heavily eroded. In addition, there are subtle differences in the textures here that make this look different from the plate-like lava we find in other areas of Mars. Instead, perhaps something similar happened, but with a mixture of ice and rock instead of lava.

It's possible that a freezing mudflow was pulled apart here, with a frozen upper layer breaking and rafting apart on top of slushy material. When the underlying slushy ice later froze, it would have expanded and been squeezed up between the plates, creating the raised ridges between them.

Photo credit: NASA/JPL/University of Arizona

Diverse Layers and Mineralogy near Mawrth Vallis

2011-11-05T00:00:00.002+08:00

This HiRISE image shows diverse layers in a region near Mawrth Vallis, a channel that was probably carved by water in Mars' ancient past. The color subimage shows details of layers exposed in a crater wall.

Tannish to white tones are apparent, which may be reflective of differences in mineralogy. CRISM, a spectrometer on MRO, has detected clays in Mawrth, so the layers here may be clay-rich.

Clays contain water, indicating that this region may have been wet in the past. The subimage also shows polygonal-like textures on some of the layered rock. These may be dessication polygons formed when the wet clays dried. The dark patches on the layers are sand dunes.

Photo credit: NASA/JPL/University of Arizona

Gullies on the South Wall of Dao Vallis near the Confluence with Niger Vallis

2011-11-04T00:00:00.002+08:00

Dao Vallis is an outflow channel that begins on the southeastern flank of the broad low-relief volcano Hadriaca Patera and extends in a southwestwardly direction across the southern highlands for approximately 1000 kilometers ending near Hellas basin. Outflow channels are generally thought to result from the catastrophic release of enormous amounts of ground water that create floods that scour the surface over periods of days to several months.

This image shows the south wall of Dao Vallis just upstream of the confluence with Niger Vallis. The gullies that flow into Dao Vallis begin just below the top of the valley wall and erode through the upper rock layers. Gully deposits appear to overlap the material that fills the valley floor. This valley fill material was likely ice-rich and flowed down the wall or valley similar to slow moving glacial material on Earth.

Located beyond the gullies on the valley floor is an intriguing crater-like feature surrounded by concentric fractures. These fractures would allow ice to sublimate into the atmosphere from the subsurface materials causing progressive collapse of the crater walls and resulting in the formation of the interior hummocky terrain. Fine-grained sediments are trapped by the hummocky terrain and are reworked by local winds forming dunes on the central portion of the crater floor.

Photo credit: NASA/JPL/University of Arizona

Oraibi Crater

2011-10-25T00:00:00.003+08:00

Oraibi crater is about 32 km across and situated in Ares Vallis on Mars. The crater is filled with sediments and its southern rim has been eroded by water. The image was acquired by the HRSC instrument on Mars Express at about 16°N/327°E during orbit 9393 on 11 May 2011. The images have a ground resolution of 15 m per pixel. North is to the right in this image and south to the left.

Photo credit: ESA/DLR/FU Berlin (G. Neukum)

Four New Names Approved for use on Mars

2011-10-24T18:00:00.002+08:00

From the USGS Astrogeology Science Center:

The names Corozal, Palikir, Raga, and Tivat have been approved for use on Mars. For more information, see the maps of Mars in the Gazetteer of Planetary Nomenclature.

Note: Corozal is a small crater located within a much larger unnamed crater in Terra Cimmeria, and is named for the town of Corozal, Belize. Palikir Crater is also a small crater, but located in the southern half of Newton Crater; it is named for the capital of the Federated States of Micronesia. Raga Crater is located in western Aonia Terra, to the southwest of Icaria Planum, and is named for a town in South Sudan. Tivat Crater is located in Noachis Terra, and is northeast of Asimov Crater. It is named for a town in Montenegro.

Mysterious Color-Changing Dust Devil Track

2011-10-24T00:00:00.001+08:00

Dust devils leave tracks behind them that create the beautiful swirling patterns visible here (approximately 0.5 kilometers, or 0.3 miles across) and in many other images of dust-covered terrain. Suction created by the air rotating in a whirlwind removes a thin layer of light-colored dust from the Martian surface, leaving behind dark lines in the dust devil's path.

That's what usually happens. In this case, however, there is an unusual streak that appears brighter at one end (approximately 0.6 kilometers or 0.4 miles across, and north is roughly upwards).

The bright streak could be a deposit of light-colored material that the dust devil dropped for some reason: maybe the dust devil died out right at this spot. Or it could be that at this particular location, the underlying dune is brighter than the dust on top of it, so when the dust devil removed the surface layer, a brighter layer below was revealed. Or there could be some other explanation we haven't even thought of yet!

Numerous small slope streaks are also visible in this image; for example, on the left side of the subimage, white arrow. These are thought to occur when a thin layer of dust avalanches downhill, revealing darker material beneath. Over time, these streaks, like dust devil tracks, slowly brighten to match their surroundings, as dust is deposited from the atmosphere to cover them.

Photo credit: NASA/JPL/University of Arizona

Note: This image is located in an impact crater northwest of Antoniadi Crater.

Possible Newest Segment of Cerberus Fossae

2011-10-23T00:00:00.000+08:00

This small fossa segment cuts the channel of Athabasca Valles, and post-dates the youngest of Mars' outflow channels. A "fossa" is a cavity or depression.

Floods of water and lava are thought to have emanated from the larger fossae nearby, perhaps forming the Athabasca channel and later filling it with lava. Comparison with the larger fossa segments at the Athabasca Valles head may reveal whether this will be a source of a future flood.

Photo credit: NASA/JPL/University of Arizona

The Millipedes of Mars?

2011-10-22T00:00:00.000+08:00

HiRISE observations like this one are used to aid in classification and volume estimates of dunes in the USGS global dune database.

Sand dunes are among the most widespread aeolian features present on Mars. Their spatial distribution and morphology are sensitive to subtle shifts in wind circulation patterns and wind strengths. These provide clues to the sedimentary history of the surrounding terrain.

What's fascinating about this image is the ridges running the length of the dunes here, creating the spectacular illusion that we're looking at millipedes. This is a good example of what's called "pareidolia," where we see things that really are not there.

Luckily, the power of HiRISE helps us see formations in greater detail to know we're seeing impressive dune ridge formations and not insects!

Photo credit: NASA/JPL/University of Arizona

Note: The location of these dunes is in the region west of the Hellespontus Montes, southeast of Rabe Crater.

Lobate Flow Features in the Northwest Hellas Rim

2011-10-21T00:00:00.001+08:00

This image, taken by HiRISE, shows a lobate tongue on the northwest Hellas rim.

Lobate features such as these are located in the mid-latitudes (30-60 degrees), indicative of viscous flow, are reminiscent of terrestrial glaciers and have long-been interpreted as evidence for subsurface ice.

Recent ground-penetrating radar observations by SHARAD of other lobate features in this latitude belt also support the notion that these features have cores with ice.

Photo credit: NASA/JPL/University of Arizona

Note: This landscape is located somewhat to the northeast of Hellespontus Montes.

Sinuous Ridge in Malea Planum

2011-10-17T00:00:00.001+08:00

This area of Malea Planum is covered by bright dust and dark lines. These lines formed by swirling winds known as dust devils that move across the surface removing the dust cover and revealing the darker rock materials beneath.

In the lower half of this image there is a faint sinuous, broad bouldery unit. Although largely dust covered, this sinuous unit may mark the location of a stream that once flowed across the plains. The stream may have later been filled by a lava flow or other bouldery material that was more resistant to erosion than the surrounding terrains forming what is known as an inverted stream. Since this time dust has largely filled in this terrain.

Photo credit: NASA/JPL/University of Arizona

Artynia Catena

2011-10-16T00:00:00.000+08:00

This observation shows an impressive chain of pits along the southernmost tip of the chain in Artynia Catena, located on the northwestern flank of the volcano, Alba Patera.

These pits form in fracture along its southern most extent. The fracture is part of a larger fracture system that is radial to the volcano and suggests that it is related to the formation of the volcano. Therefore, this chain of pits may have formed from the withdrawal of subsurface magma and subsequent partial collapse of the overlying material into the fracture.

Another explanation may be that subsurface water/ice may have preferentially formed along these fractures and subsequent removal of ice-rich material by sublimation resulted in partial collapse of surface materials forming the pit chain.

Photo credit: NASA/JPL/University of Arizona

Scarp in Aurorae Chaos

2011-10-15T00:00:00.002+08:00

Aurorae Chaos is a large irregular depression consisting of jumbled uplifted blocks, knobs, mounds and isolated mesas known as chaotic terrains.

These areas of chaos are the source regions for the catastrophic releases of ground water thought to have formed the outflow channels. Aurorae Chaos extends to Eos, Capri and Gangis Chasma to the south and east and to Simud and Tiu Vallis to the north as well as to other chaotic terrains west of Margaritifer Chaos.

Along the southeastern part of the image is a prominent scarp. The elevated region to the right is likely a remnant mesa of original terrain. The lower elevation region to the west and north are areas where ground water was likely released and forming conduits flowed out of the chaotic terrain towards Simud and Tiu Valles.

Photo credit: NASA/JPL/University of Arizona

Changes to Sand Dunes in Syrtis Major

2011-10-14T00:00:00.000+08:00

Now that HiRISE has been returning data from its primary science orbit at Mars since 2006, it has been able to document changes in the position of sand dunes and ripples on the surface.

Shown here is one example, illustrating changes in sand dunes, located within a crater in Syrtis Major, from December 16, 2007 (HiRISE image PSP_006501_2005) to September 11, 2011 (ESP_024025_2005, this image).

The time interval is approximately two Mars years, such that lighting geometry is very similar in the two images. In addition, the MRO spacecraft took both images at nearly the same roll angle. With the similar lighting and viewing geometry, changes can be readily seen. Subimage 1 shows a series of zoomed views, starting from part of the dune field and then zeroing in on the slip face of one dune. Subimage 2, an animated GIF, shows how the dune slip face, and ripples on dune surface, have changed over two Mars years.

The dune appears to have moved a couple of meters. This demonstrates that this region of Mars has winds strong enough to move significant volumes of sand.

Photo credit: NASA/JPL/University of Arizona

Note: This large crater is located on the northwestern "shore" of Isidis Planitia; the closest named feature is Jezero Crater, which lies to the southwest.

Approaching Endeavour Crater, Sol 2,680

2011-10-13T00:00:00.002+08:00

This image from the navigation camera on NASA's Mars Exploration Rover Opportunity shows the view ahead on the day before the rover reached the rim of Endeavour crater. It was taken during the 2,680th Martian day, or sol, of the rover's work on Mars.

It is one of 309 images included in a video record of Opportunity's three-year journey of more than 13 miles (21 kilometers) to reach Endeavour from its last previous major destination, Victoria crater.

Photo credit: NASA/JPL-Caltech

Crater with Surrounding Bench in Sinus Meridiani

2011-10-10T00:00:00.004+08:00

This image is located within Northern Sinus Meridiani, a region of ridged terrains and extensive stratigraphic layering.

Originally identified in a Mars Orbiter Camera image (MOC), this 10-kilometer (approximately 6 miles) diameter crater is surrounded by a prominent bench. As this HiRISE image shows, there is extensive layering in the upper cap units.

The bench formed because these layered surface units are eroding at a faster rate than the more resistant underlying materials that comprise the rest of the crater.

This is a stereo pair with ESP_023593_1845.

Photo credit: NASA/JPL/University of Arizona

Light-Toned Layered Rock Outcrop in Ladon Valles

2011-10-09T00:00:00.001+08:00

Ladon Vallis, an approximately 600 kilometer (370 mile) long outflow channel, is part of a larger system that begins in Argyre basin to the south and extends northwards across the Southern Highlands towards the larger Ares Vallis outflow system. This image shows part of Ladon Vallis that is located within Ladon basin.

Here the extensive laterally continuous outcrops of layered light-tone units and deposits contrasts sharply with the darker-toned materials that cover the channel floor. Dark-toned dunes partly infill fractures and impact craters.

These extensive layers may have resulted from ponding of water and sediments that flowed into the basin from Ladon Vallis. Subsequent episodic flood events out of the basin to the north may have eroded and exposed the pre-existing sedimentary layers.

Photo credit: NASA/JPL/University of Arizona

Colorful Central Peak in Noachis Terra

2011-10-08T00:00:00.000+08:00

Small impact craters retain their original bowl shape, but once a crater is large enough that the force of gravity on the slopes of the crater wall is greater than the strength of the target material, the wall collapses inward to form a central peak.

On Mars, the transition between simple (bowl-shaped) and complex craters is observed to occur at about 7-kilometer diameter. The formation of central peaks in complex craters brings up material from deep beneath the Martian surface. Therefore, central peaks of complex craters are good places to look for ancient rocks.

The colorful rocks exposed in the central peak visible in this image probably reflect variations in mineral content that were caused by water activity early in Mars' history. The CRISM hyperspectral image that was taken at the same time as this HiRISE image may show evidence for the various types of minerals that presumably are responsible for the colors visible here.

Photo credit: NASA/JPL/University of Arizona

Note: This crater is located in northwestern Noachis Terra, east of Nectaris Fossae and south of Saravan Crater.

Dunes in Richardson Crater

2011-10-07T00:00:00.002+08:00

Richardson Crater is well-known among Mars scientists for its spectacular dunes.

These dunes are located around -72 degrees in latitude; if they were on Earth they'd be well south of the Antarctic Circle! Because of their extreme southern positioning, they endure dramatic temperature changes over the course of the Martian year. The HiRISE team attempts to monitor this area as these dunes get covered by seasonal frost in the fall and defrost in the spring, taking multiple images over the same locations in order to better understand the structure and evolution of these beautiful landforms.

This image was taken close to the Southern hemisphere autumnal equinox, the end of Southern Hemisphere summer and beginning of autumn. Unlike that observed on Earth, the frost seen on the Richardson Crater dunes is composed of carbon dioxide, and sublimates (goes directly from a solid to a gas) rather than melts. At the time of this image, the frost has likely disappeared to its greatest extent and will begin to re-accumulate soon.

Wide, dark streaks are visible extending from the crests of the dunes, likely due to movement of material as the dunes defrosted or to wind transportation of surface particles. Numerous dust devil tracks are still visible as thin, dark, criss-crossing marks, although these will gradually be covered by carbon dioxide frost as Southern hemisphere winter sets in.

The subimage is approximately 1 kilometer (about 0.62 miles) across.

To see the previous image taken at this same location, taken in early Southern Hemisphere spring as the dunes were thawing, see ESP_011785_1075.

To take a look at other impressive dunes from various locations within Richardson Crater, see ESP_012774_1080, PSP_004230_1080, and ESP_012985_1075.

Photo credit: NASA/JPL/University of Arizona

Note: Here is the Italian translation of the above caption (Spettacolari Dune Nel Cratere Richardson), the Spanish translation (Espectaculares Dunas en el Cráter Richardson), and the Portuguese translation (Dunas Espetaculares na Cratera Richardson).

Phobos

2011-10-04T00:00:00.001+08:00

Mars Express obtained these views of Phobos, the largest of the Martian moons, when it flew by on 9 January 2011, passing at a distance of 100 km.

This sequence shows 5 HRSC-channels, orbit 8974: (left to right) stereo S1 (4.1 m/pixel), photometric P1 (8.1 m/pixel), nadir ND (3.9 m/pixel), photometric p2 (8.2 m/pixel), stereo S2 (4.3 m/pixel).

Photo credit: ESA/DLR/FU Berlin (G. Neukum)

Tithonium Chasma

2011-10-03T00:00:00.001+08:00

This complicated landscape of craters, slopes, and boulders is in an area called Tithonium Chasma, a large trough that is itself a part of the more well-known canyon system Valles Marineris.

Scientists are interested in imaging canyons such as these because they provide a view "under" the surrounding Martian surface to potentially older material beneath (similar to the Grand Canyon on Earth). This image shows the floor of the trough, although the walls of this canyon have also been imaged previously (see PSP_007562_1745 for one example of the walls of Tithonium Chasma).

Evidence from the CRISM instrument, a spectrometer also aboard Mars Reconnaissance Orbiter, suggests sulfates and iron oxides exist in this general region, in the form of layered deposits. (Murchie, S. et al. 2009. A synthesis of Martian aqueous mineralogy after 1 Mars year of observations from the Mars Reconnaissance Orbiter. Journal of Geophysical Research: 114.) It is unknown how far these deposits may extend beneath the surface.

Photo credit: NASA/JPL/University of Arizona

Layered Yardangs

2011-10-02T00:00:00.001+08:00

This observation shows terrain on the floor of a large, degraded crater. Many sharp ridges are visible across the image, all of them aligned in a similar direction. There are patches of dark sand in the low areas between the ridges and on the ridge slopes.

What creates these sharp ridges? This layered terrain has been sculpted by the wind. The aligned ridges are called yardangs, which are formed in areas where the dominant erosional force is the wind. Yardangs are also found on Earth, usually in very dry areas.

The subimage shows a closeup of some yardangs.

This is a stereo pair with ESP_023051_1865.

Photo credit: NASA/JPL/University of Arizona

Note: This crater is located south of Tikhonravov Crater in Terra Sabaea.

Gullies and Curved Ridges at the Base of Crater Walls

2011-10-01T00:00:00.000+08:00

This southern mid-latitude crater is typical of other small craters in this latitude band, containing both gullies on its walls and arcuate ridges at the base of the walls.

These features appear inter-related and their orientation on the crater wall can be associated with the latitude of the crater. Craters at latitudes between about -30 and -44 degrees (in the Southern hemisphere) typically have pole-facing gullies and curved ridges. Craters at latitudes between -44 degrees and -60 degrees (as is this one at -47 degrees) typically have these features on equator-facing walls, or on the east and west walls. This is thought to relate to changes in the obliquity of Mars.

These features likely formed during a period of high obliquity (tens of millions of years ago). During this time, it is thought that snowfall was deposited in these mid-latitude regions, and the high tilt of the planet led to higher degrees of solar insolation on the different crater walls, causing the snow to melt and form gullies. The arcuate ridges are thought to be moraines, or remnants of snowpacked ice flowing down the crater wall and onto the crater floor.

Photo credit: NASA/JPL/University of Arizona

Note: This crater is located slightly to the southwest of Hellas Planitia; the closest named crater to this site is Matara Crater.

A Network of Dust Devil Tracks

2011-09-30T00:00:00.002+08:00

The entire area in this image has been recently crossed by multiple dust devils. This area was probably initially covered by a layer of bright dust.

Dust devils (small tornado-like vortices common in many places on Mars) then lifted the dust into atmospheric suspension as they moved along the surface, exposing darker, less dusty material below. Some areas in this image have more boulders than others, but the dust devil tracks cross them without being much affected.

Photo credit: NASA/JPL/University of Arizona

Note: The location of this image is just east of Wallace Crater, which itself is slightly to the southeast of Hellas Planitia.

Rocas Coloridas en Terra Sabaea

2011-09-29T00:00:00.001+08:00

Esta zona de las antiguas tierras altas australes ha sido modificada por la tectónica, es decir, por fallas y pliegues que afectan a las unidades de roca.

Esta imagen también es interesante vista a través de los colores de la HiRISE. Estos (mejorados en la subimagen) indican la variedad de minerales que hay presentes. Esta región fue objetivo del CRISM para estudiar con más detalle la detección de olivino que se había hecho previamente. El olivino, un mineral volcánico, da los colores verdes y azules que se aprecian en la imagen de la HiRISE.

Colorful Rocks in Terra Sabaea

This area of the ancient southern highlands has been modified by tectonics, i.e., faults and folds that affect the rock units.

This image is also interesting view through the colors of the HiRISE. These (enhanced in the subpicture) indicate the variety of minerals that are present. This region was the target of CRISM to study in more detail the detection of olivine that had been done previously. Olivine, a volcanic mineral, giving the green and blue colors that are seen in the HiRISE image.

Photo credit: NASA/JPL/La Universidad de Arizona

Note: This location is about halfway between Hellas Planitia (which is due south) and Harris Crater, which is slightly to the north-northeast.

Small Mounds in Chryse Planitia

2011-09-26T00:00:00.012+08:00

This HiRISE image shows a group of cones, shield-like features, and round mounds. They are a few hundred meters to kilometers in diameter. Possible origins include sedimentary (mud) volcanism and magmatic volcanism. HiRISE data are essential for evaluating these hypotheses.

Photo credit: NASA/JPL/University of Arizona

Note: This image is located in southern Chryse Planitia, north of the "mouth" of Simud Valles, and about halfway between the landing sites of Viking 1 and Pathfinder.