Edited Mars Reconnaissance Orbiter image of subliming ice on Mars, along with a nice crater in the middle. Grayscale version from NASA.

Edited Mars Reconnaissance Orbiter image of dark markings, probably dust devil tracks, in Promethei Terra.

Edited Mars Reconnaissance Orbiter image of erosion in Cerberus Fossae.

Edited Mars Reconnaissance Orbiter image of part of Mount Sharp in Gale Crater along with the Curiosity Rover a little above the center of the image. Color/processing variant. The small yellow circle shows where Curiosity can be seen.

Edited Mars Reconnaissance Orbiter image of light-toned deposits in Orson Welles Crater.

Edited Mars Reconnaissance Orbiter PR image of a layer of rocky material cut by some process (perhaps flowing water a billion or two years ago) and now filled by sand dunes.

Edited Mars Reconnaissance Orbiter image of subliming ice on Mars, along with a nice crater in the middle. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of snow (I presume carbon dioxide snow but certainly could be wrong) on the tops of sand dunes on Mars. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of erosion in Cerberus Fossae. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of a criss-crossed landscape with fresh craters near the top of the image. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of a 360 meter crater in layered deposits in Mars' north polar region. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of part of Mount Sharp in Gale Crater along with the Curiosity Rover a little above the center of the image. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of ridges in Meridiani Planum. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of Curiosity in Gale Crater. This is a red channel (and only the red channel, but spread to green and blue as well, so it appears grayscale) context image for the set. Inverted grayscale variant.

Edited Mars Reconnaissance Orbiter image of Barchan sand dunes and bedrock.

Image source: photojournal.jpl.nasa.gov/catalog/PIA21934

Original caption: On the west (left) side of this image from NASA's Mars Reconnaissance Orbiter, fairly textbook-looking barchan sand dunes sit atop the bedrock. Barchan dunes pointing in the opposite direction are just a few kilometers away to the east.

In between these opposing barchan dunes are star dunes. Barchan dunes form when the sand-moving wind is fairly unidirectional. Star dunes, in contrast, form when the sand-moving wind comes from multiple directions -- not all at once, but from varying directions at different times of day or year.

Where is the sand coming from? As with most places on Mars...well, that's an area of on-going research. But the star dunes are telling us that this area seems to be accumulating sand.

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.

Image Credit:

NASA/JPL-Caltech/Univ. of Arizona

Image Addition Date:

2017-09-04

Edited Mars Reconnaissance Orbiter image of layered bedrock in the Meridiani Region. Inverted grayscale variant.

Edited Mars Reconnaissance Orbiter image of rocky ridges at least partially formed and shaped by flowing wind. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of uplifted light-toned blocks. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of Libya Montes, a possible landing site for a future probe. Processing variant.

Original caption: Proposed Site for Future Exploration in Libya Montes

The Libya Montes are a highland terrain on Mars up-lifted by the giant impact that created the Isidis basin to the north.

NASA/JPL/University of Arizona (273 km above the surface, less than 5 km top to bottom and north is to the right.)

Source: www.uahirise.org/ESP_022970_1835

Edited Mars Reconnaissance Orbiter image of a monitoring campaign of slopes in Cerberus Fossae.

Edited Mars Reconnaissance Orbiter image of layers in Eberswalde Crater on Mars.

Edited Mars Reconnaissance Orbiter image of part of the floor of Noctis Labyrinthus (one of the best-named places in the Solar System). Processing variant.

Edited Mars Reconnaissance Orbiter image of a depression in Utopia Planitia. Grayscale version.

NASA has a program that lets members of the general public suggest areas of Mars to be imaged by MRO and I suggested this site - this is the second area that I've suggested that NASA has selected to be imaged. Please see www.uahirise.org/hiwish/ for more information.

Edited Mars Reconnaissance Orbiter image of the steep scarp on the edge of the north polar ice cap. Color/processing variant.

Image source: www.uahirise.org/ESP_054663_2650

Original caption: HiRISE has been re-imaging regions first photographed in 2006 through 2007, six Mars years ago. This long baseline allows us to see large, rare changes as well as many smaller changes.

One of the most actively changing areas on Mars are the steep edges of the North Polar layered deposits. This image shows many new ice blocks compared to an earlier image in December 2006. An animation shows one example, where a section of ice cliff collapsed. The older image (acquired in bin-2 mode) is not as sharp as the newer one.

Written by: Alfred McEwen (audio: Tre Gibbs) (25 June 2018)

Edited Mars Reconnaissance Orbiter image of subliming ice on Mars, along with a nice crater in the middle. Grayscale version from NASA. Processing variant.

This image shows rocks on the floor of Iani Chaos, a region of collapsed and disorganized terrain. The chaotic terrains on Mars may have been the sources of floodwaters that carved the giant outflow channels. They typically contain irregular hills like the one in the center of this image. In some cases, they also have light-toned rocks exposed on the floors. The point of interest is to determine whether these rocks predate the chaos or formed after the collapse; however, the contacts may be obscured by later material mantling the ground.

Edited Mars Reconnaissance Orbiter image of a dichotomy boundary in the Aeolis Region of Mars. Color variant.

Edited Mars Reconnaissance Orbiter image of part of the floor of Noctis Labyrinthus (one of the best-named places in the Solar System).

Edited Mars Reconnaissance Orbiter image of sand dunes on what looks like bedrock.

Edited Mars Reconnaissance Orbiter image of tracks left by dust devils on Mars. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of sand dunes on Mars (looking a lot like sand dunes in Africa).

Edited Mars Reconnaissance Oribter image of volcanic cones in the Cydonia Colles region of Mars. Color/processing variant. Processing variant.

Edited Mars Reconnaissance Orbiter image of sand dunes in Hyperborei Cavi. (I love Martian names.) Color/processing variant.

Edited Mars Reconnaissance Orbiter image of light-toned layers in Tithonium Chasma.

Original caption: Tithonium Chasma is a part of Valles Marineris, the largest canyon in the Solar System. If Valles Marineris was located on Earth, at more than 4,000 kilometers long and 200 kilometers wide, it would span across almost the entire United States. Tithonium Chasma is approximately 800 kilometers long. A “chasma”, as defined by the International Astronomical Union, is an elongate, steep-sided depression.

The walls of canyons often contain bedrock exposing numerous layers. In some regions, light-toned layered deposits erode faster than the darker-toned ones. The layered deposits in the canyons are of great interest to scientists, as these exposures may shed light on past water activity on Mars. The CRISM instrument on MRO indicates the presence of sulfates, hydrated sulfates, and iron oxides in Tithonium Chasma. Because sulfates generally form from water, the light-toned sulfate rich deposits in the canyons may contain traces of ancient life.

The mid-section of this image is an excellent example of the numerous layered deposits, known as interior layered deposits. The exact nature of their formation is still unclear. However, some layered regions display parallelism between strata while other regions are more chaotic, possibly due to past tectonic activity. Lobe-shaped deposits are associated with depositional morphologies, considered indicative of possible periglacial activity.

Overall, the morphological and lithological features we see today are the result of numerous geological processes, indicating that Mars experienced a diverse and more active geological past.

Written by: Elizabeth Silber, Livio Tornabene, and Kayle Hansen (12 August 2015)

Edited Mars Reconnaissance Orbiter image of sample terrain in Noctis Fossae. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of ejecta from a crater in Meridiani Planum. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of subliming ice on Mars, along with a nice crater in the middle. Cropped (showing the crater), color/processing variant.

Edited Mars Reconnaissance Orbiter image of erosion in Cerberus Fossae. Color/processing variant.

This proposed future Mars landing site in Acidalia Planitia targets densely occurring mounds thought to be "mud" volcanoes.

Mud volcanoes are geological structures formed when a mixture of gas, liquid and fine-grained rock (or mud) is forced to the surface from several meters to kilometers underground. Scientists are targeting these mud volcanoes because the sediments, brought from depth, could contain organic materials that might provide evidence for possible past and present microbial life on Mars.

Edited Mars Reconnaissance Orbiter image of fractured mounds and cracks in part of Elysium Planitia. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of rocky outcroppings in Mawrth Vallis on Mars. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of part of Mount Sharp in Gale Crater along with the Curiosity Rover a little above the center of the image.

Edited Mars Reconnaissance Orbiter image of part of Mawrth Vallis on Mars. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of a tilted block of terrain set in a general subsidence south of Orson Wells Crater on Mars.

Edited Mars Reconnaissance Orbiter image of sand dunes being monitored for changes in Lyot Crater.

Edited Mars Reconnaissance Orbiter image of a crater floor in Tempe Fossae. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of Hamelin Crater. Inverted grayscale variant.

Original caption: Hamelin Crater

This image straddles Hamelin with another crater, which is only 90 km northeast of the original landing site selected for Viking Lander 1 in Chryse Planitia. Hamelin shows the raised edge or rampart around the ejecta blanket that is characteristic of many craters in this area.

NASA/JPL/University of Arizona (284 km above the surface, less than x km top to bottom and north is to the right.)

Source: www.uahirise.org/ESP_020904_2005

Edited Mars Reconnaissance Orbiter image of ejecta from a crater in Meridiani Planum. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of mineralogy in Acidalia Planitia.

Edited Mars Reconnaissance Orbiter context image of erosion in Cerberus Fossae. Inverted grayscale variant.