Ophir Chasma forms the northern portion of the vast Mars canyon system Valles Marineris, and this image, acquired on Aug. 10, 2015, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter, features a small part of its wall and floor.

The wall rock shows many sedimentary layers and the floor is covered with wind-blown ridges, which are intermediate in size between sand ripples and sand dunes. Rocks protruding on the floor could be volcanic intrusions of once-molten magma that pushed aside the surrounding sedimentary layers and “froze” in place.

Images like this can help geologists study the formation mechanisms of large tectonic systems like Valles Marineris. (The word “tectonics” does not mean the same thing as “plate tectonics.” Tectonics simply refers to large stresses and strains in a planet’s crust. Plate tectonics is the main type of tectonics that Earth has; Mars does not have plate tectonics.)

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

The High Resolution Imaging Science Experiment (HiRISE) camera aboard NASA's Mars Reconnaissance Orbiter often takes images of Martian sand dunes to study the mobile soils. These images provide information about erosion and movement of surface material, about wind and weather patterns, even about the soil grains and grain sizes. However, looking past the dunes, these images also reveal the nature of the substrate beneath.

Within the spaces between the dunes, a resistant and highly fractured surface is revealed. The fractured ground is resistant to erosion by the wind, and suggests the material is bedrock that is now shattered by a history of bending stresses or temperature changes, such as cooling, for example.

Alternately, the surface may be a sedimentary layer that was once wet and shrunk and fractured as it dried, like gigantic mud cracks. In either case, the relative small and indistinct fractures have trapped the dark dune sand marching overhead. Now the fractures have become quite distinct, allowing us to examine the orientation and spacing of the fractures to learn more about the processes that formed them.

This view is one image product from HiRISE observation ESP_042223_1890, taken July 30, 2015, at 2:33 p.m. local Mars time, 8.719 degrees north latitude, 67.347 degrees east longitude.

HiRISE is one of six instruments on the Mars Reconnaissance Orbiter. The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colorado. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, built the orbiter and collaborates with JPL to operate it.