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This image was acquired on January 2, 2014 by NASA's Mars Reconnaissance Orbiter. Dune fields located among canyon wall slopes are also known as "wall dune fields" and are further identified as either climbing or falling. Falling dunes are defined as large bedforms with lee faces on the downhill side-indicating that this is the direction of their migration-and on moderate slopes greater than 10 to 12 degrees. (A lee face is the the down-wind side of a dune.)

On Earth and Mars, these types of dunes are largely controlled by what is called "microtopography." Physical obstacles can accelerate and decelerate airflow, create turbulence, potentially enhancing erosion, deposition, and/or transport of dune sediment.

This class of dune morphology is relatively rare across Mars. However, falling dunes (like these) and climbing fields are frequently located among the spur-and-gully walls in the Melas and Coprates chasmata (see the paper here). Here is one example, of active falling dunes on this large massif in east Coprates Chasma.

Additional information: ESP_053739_1650, Digital terrain map

The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 27.7 centimeters (10.9 inches) per pixel (with 1 x 1 binning); objects on the order of 83 centimeters (32.7 inches) across are resolved.] North is up.

This is a stereo pair with ESP_035278_1655.

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 Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.