Pits along Fractures in Crater Floor Material

This image shows the degraded rim of a large impact crater which is partly filled with material that is fractured in several places, especially near the crater rim.

Pits of various sizes have formed along most of the fractures, and some of the pits have merged into elongated depressions. The association of the pits with the fractures suggests that the pits were formed by removal of material deep within the fractures. A plausible reason for the formation of these features is that the crater floor material includes substantial ground ice. When the fractures open, perhaps due to glacial-like flow of the ice-rich floor material toward the center of the crater, water ice is exposed to the Martian atmosphere.

The ice then evaporates into the dry atmosphere, enlarging the fracture at depth. As the icy "cave" grows, ice-free material near the surface collapses into the cave, forming the pits we see here.

Photo credit: NASA/JPL/University of Arizona

Note: This crater is located in the fretted terrain of Protonilus Mensae. The closest named feature to this crater is Renaudot Crater, which is to the southeast.

Capri Chasma

This VIS image shows a portion of Capri Chasma. Dunes are found on the floor of this chasma.

Photo credit: NASA/JPL/Arizona State University

Note: Capri Chasma is part of the larger Valles Marineris System, located just south of Aurorae Planum and east of Coprates Chasma.

Big Impact-Triggered Dust Avalanche

MRO's Context camera (CTX) acquired the image at lower left on 18 November 2007 and the adjacent image on 14 February 2010, showing a large new slope streak in the aureole (giant landslide deposits) of Olympus Mons.

Slope streaks (dust avalanches) are common on Mars but this one is unusually wide and it began from an unusual extended/fuzzy source area. HiRISE acquired the follow-up image (right) 31 March 2010, revealing a small, pristine impact crater (blue arrow) in the fuzzy source area, which resembles the airblast patterns seen at many other new (recent year) impact sites. We've conclude that an impact event occurred sometime between the dates of the CTX images and triggered a large dust avalanche.

Photo credit: NASA/JPL/University of Arizona

Lava Flows in the Tharsis Region

This VIS image in the Tharsis region shows a lava flow that topped the rim of an impact crater and flowed down to the floor of the crater.

Photo credit: NASA/JPL/Arizona State University

Deformed Craters and Polygons in Utopia Planitia

This image of Utopia Planitia shows some deformed craters. The crater rims are not round but elliptical and even angular.

The region is interesting because there are surface features (e.g., polygonal cracks) which suggest that water ice is close to the surface. A good example is just to the south of the featured image here. Other craters in the area appear old and eroded. Many are filled with material which could contain quantities of water ice. Were these deformed craters the result of an oblique impact or were they deformed afterwards by an as-yet unknown process?

Photo credit: NASA/JPL/University of Arizona

Intra-Crater Structure in NW Hellas Basin

This subimage from an observation by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter covers a small portion of the northwest quadrant of Hellas Basin, or Hellas Planitia, on southern Mars. With a diameter of about 2,200 kilometers (about 1,400 miles) and a depth reaching the lowest elevations on Mars, Hellas is one of the largest impact craters in the solar system.

This area of Hellas Basin has a number of unusual features which are thought to be quite old because of the high crater density. Here a crater inside Hellas has been filled with material. This may be related to volcanic activity on the northwestern rim of Hellas.

However, it might also be related to water and water ice. There is evidence elsewhere that the ground here is ice-rich. HiRISE is being used to investigate this in more detail when Hellas Basin is free from atmospheric dust.

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

Note: Fore more photos and information about this formation, see here.

Knobs near Reull Vallis

This observation shows a knob and large crater near Reull Vallis, east of the Hellas Basin. The crater's ejecta blanket abuts the base of the knob. The crater floor and ejecta are blanketed with an ice-rich mantle that is common throughout the Martian mid-latitudes.

The mantle deposits are pitted and grooved perhaps due to the sublimation of ice. This mantle is thought to have been deposited as snow around 10 million years ago during a period of high obliquity, when the planet's axis was more tilted and environmental conditions could have been more conducive to snowfall in these regions.

Several small impact craters are visible on the ejecta blanket that appear to have been filled with mantling deposits that have since been partially removed. These craters give us clues to the erosional history of the deposit. Note the fresh looking impact crater at the top of the knob. This crater does not appear to contain mantling deposits and may be much younger.

This region contains many mesas surrounded by lobate debris aprons that are thought to be ice-rich. These aprons have been interpreted as a variety of possible features including rock glaciers, ice-rich mass movements, or debris-covered glacial flows. Reull Vallis itself is filled with what is referred to as "fretted terrain," which is also thought to be ice-rich material.

Photo credit: NASA/JPL/University of Arizona

Ganges Chasma

This VIS image of Ganges Chasma shows where a large portion of the canyon wall has given way and formed a landslide deposit. Large landslides deposits are common features in Valles Marineris and the surrounding chasmata.

Photo credit: NASA/JPL/Arizona State University

Light-Toned Rocks inside a Crater

This approximately 20 kilometer diameter impact crater is located just to the south of Coprates Chasma in Valles Marineris.

Near the center of the crater are some light-toned rocks. These rocks are very jumbled and broken up rather than flat-lying and layered. These observations suggest that the light-toned rocks once existed below the current terrain and were brought up by the process that created the crater.

Several other craters around Valles Marineris also reveal light-toned rocks in their central peaks suggesting that the light-toned rocks are a regional unit that is buried beneath the lava plains that now surround Valles Marineris.

Photo credit: NASA/JPL/University of Arizona

Rhabon Valles

This VIS image shows a portion of Rhabon Valles, a channel south of Uranius Mons.

Photo credit: NASA/JPL/Arizona State University

Endeavour Crater on the Horizon

NASA's Mars Exploration Rover Opportunity used its panoramic camera (Pancam) to capture this view of the rim of Endeavour crater, the rover's destination in a multi-year traverse along the sandy Martian landscape. The image was taken during the 2,226 Martian day, or sol, of Opportunity's mission on Mars (April 28, 2010).

Endeavour is 21 kilometers (13 miles) in diameter, about 25 times wider than Victoria crater, the last major crater Opportunity visited. This image shows an outcrop of rocks at the foot of the rover and beyond these rocks rippled dunes, which are about 20 centimeters (8 inches) tall. The west rim of Endeavour, about 13 kilometers (8 miles) away, appears on the left on the horizon. The rim of smaller, more-distant Iazu crater, which is 7 kilometers (4 miles) in diameter and about 35 kilometers (22 miles) away, is on the far right. On the horizon in between is a blanket of material ejected from the impact that created Iazu crater, and darker features that are portions of the west and southwest rim of Endeavour.

Opportunity began a marathon from Victoria to Endeavour in September 2008 after spending two years exploring Victoria. The intended route, about 19 kilometers (12 miles) long, has headed south before turning east in order to bypass potentially hazardous sand ripples to the east, larger than the ripples in this image.

This approximately true-color view combines three exposures taken through filters admitting wavelengths of 750 nanometers, 530 nanometers and 430 nanometers.

Photo credit: NASA/JPL-Caltech/Cornell University

Coprates Crater in Coprates Chasma

Impact craters can be created anywhere on the surface of Mars at any time. This crater is located on the floor of Coprates Chasma.

Photo credit: NASA/JPL/Arizona State University

Reading the Geologic Record

This observation shows a series of parallel layers eroding into peculiar knobs and hills.

These sedimentary rocks were imaged on the floor of a large crater located at 8.8 degrees North, 358.3 degrees East. Similar rock units are found within several nearby craters also imaged by HiRISE, as seen in images PSP_001902_1890, ESP_013611_1910, and PSP_002733_1880. The occurrence of similar layers in each of these locations may indicate that they were once part of a much more extensive geologic unit that has now been largely eroded away.

One particularly interesting aspect of the layers in this image is their repetitive nature. Each layer appears to be nearly the same thickness throughout the outcrop, as has also been observed in other nearby layered units. This cyclic nature points to a formation process which occurred repeatedly, building up the deposit layer by layer. However, the exact formation mechanism and the climate cycle possibly responsible for forming the layers here remain unknown.

Studying the record exposed in rocks like these can help reveal secrets of the ancient Martian climate.

Photo credit: NASA/JPL/University of Arizona

Note: This crater is located in the Arabia Terra region; the closest named landmark to this crater is Marth Crater.

Orbital View of Opportunity's Region

This view of an area about 140 kilometers (about 90 miles) wide in the Meridiani Planum region of Mars shows the region around NASA's Mars Exploration Rover Opportunity. Opportunity, in the seventh year of its exploration of Mars, is in the upper central portion of the image, on multi-year trek from Victoria crater toward the much larger Endeavour crater. In April 2010, Opportunity captured views of the rims of Endeavour crater and the more distant Iazu crater on the horizon to southeast from the rover. (See PIA13081 and PIA13080.) The rover's position relative to those craters is indicated here.

This view is a mosaic of daytime infrared images taken by the Thermal Emission Imaging System (THEMIS) camera on NASA's Mars Odyssey orbiter.

Below is an annotated version of the above mosaic:

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

Gullied Trough in Noachis Terra

This observation shows gullies in a semi-circular trough in Noachis Terra. The gullies are observed to face all directions.

It is interesting to note that the gully morphology seen here depends on the orientation of the gullies. The morphology differences are most pronounced on the sunlit slope, with the gullies facing south (down) being more deeply incised than those facing the west. It is unknown what caused the different gully morphologies, but there are several possibilities.

Gullies are proposed to form at locations determined by the availability of a forming liquid (thought to be water) and/or the amount of insolation the slope receives, among other factors. It is possible that the deeper gullies experienced more erosional events or that their erosional events were more effective for undetermined reasons. It is also possible that the gullies formed at different times such that they did not have the same amount of water — either for an individual flow or total — available to them. Also, the underlying topography could make the gullies appear relatively more incised without this actually being the case.

The majority of the gullies on both sides of the trough appear to originate at a boulder-rich layer visible in the subimage. The layer appears dark on the sunlit slope because the boulders sticking out from the slopes cast shadows. If these gullies formed by water from the subsurface, then it is possible that this layer is a permeable layer that conducted water to the surface. The layer is deteriorating and traveling down slope in the form of boulders. These boulders can clearly be seen in the alcoves of the gullies on both sides of the trough.

Note that the alternating stripes on the left side of the image are an artifact from camera noise. They are not real features.

Photo credit: NASA/JPL/University of Arizona

Galaxias Fossae

The fracture system in this VIS image is part of Galaxias Fossae, a series of fractures on the northern part of the Elysium Mons volcanic complex.

Photo credit: NASA/JPL/Arizona State University

Newly-Formed Slope Streaks

This observation features three newly-formed slope streaks. These are features which occur on crater walls, hills, and other slopes on Mars.

They always begin at a point source and widen downslope, sometimes weaving around existing topographic features (such as dunes or craters), but other times they flow over them. Many slope streaks do not show topographic relief in available images, and there are no observable deposits of displaced materials surrounding their borders.

In general, slope streaks tend to be many hundreds of meters long and less than 200 meters wide. They are observed in varying shades of darkness, where lighter-toned streaks appear to be older than darker ones. The formation mechanism responsible for slope streaks is still under debate; theories range from dry dust avalanches (most widely-accepted theory) to briney water seepage.

Slope streak formation is among the few surface processes known to be currently active on Mars, making slope streaks some of the youngest features on Mars. A comparison of this HiRISE image with MOC image E04-01817 shows that three new slope streaks have formed during the six years separating these images (2001 - 2007). The shortest time frame in which new slope streaks have been observed to form is six months (MOC images SP2-37303 and E02-02379), though it is not yet known how long it actually takes for a slope streak to form.

Photo credits: NASA/JPL/University of Arizona; MOC Image E04-01817: NASA/JPL/Malin Space Science Systems.

Note: These slope streaks are located in Amazonis Planitia to the northwest of Eumenides Dorsum.

Juventae Chasma

Baetis Chasma is a chasmata near Valles Marineris. It is not directly connected to Valles Marineris, but contains some of the same features seen in the larger chasmata. Dunes are prevalent on the floor of this portion of Juventae Chasma.

Photo credit: NASA/JPL/Arizona State University

Proctor Crater Dune Field

This observation shows the edge of a dark dune field on the floor of Proctor Crater, a 150 kilometer diameter crater in the southern highlands of Mars.

The subimage is a close-up view of the dark dunes. These dunes are most likely composed of basaltic sand that has collected on the bottom of the crater. Superimposed on their surface are smaller secondary dunes which are commonly seen on terrestrial dunes of this size. Near the crests of the dark dunes are bright patches of frost. Dark spots within the frost patches are areas where defrosting is occurring.

Many smaller and brighter bed forms, most likely small dunes or granule ripples, cover the substrate between the larger dark dunes as well as most of the floor of Proctor Crater. In many locations, large boulders are seen on the same surfaces as the bright bed forms. The dark dunes stratigraphically overlie the small bright bed forms indicating that the darker dunes formed more recently.

However in several areas, the dark dunes appear to influence the orientation of the small bright dunes, possibly by wind flowing around the larger dunes, suggesting that both dark and bright bed forms are coeval.

Photo credit: NASA/JPL/University of Arizona

Note: Proctor Crater is located in the Noachis Terra region, to the west of Hellas Planitia.

Ascraeus Mons

This VIS image shows part of the northeastern flank of Ascraeus Mons, one of the large Tharsis volcanoes. The channels were carved by lava, not by water.

Photo credit: NASA/JPL/Arizona State University