This image shows a part of a central mound in an impact crater in Arabia Terra. At low resolution, the mound is relatively smooth and featureless, although elsewhere in the mound a Mars Orbiter Camera (MOC) image shows fine layers.

The mound is broad, filling much of the crater, although it now appears to be eroding. Images like this can be used to explore the nature of the deposit, and provide clues about how it formed. At high resolution the material still appears relatively uniform and featureless, without boulders or obvious fine layers. This indicates a relatively weak, fine-grained material.

The large, elongated features in the image are yardangs. These are characteristic of aeolian (wind) erosion. They form roughly parallel with the direction of the prevailing wind, and the streamlined shape (often compared with the hull of a boat) is created by persistent flow from this direction.

Yardangs on Earth often form from relatively unconsolidated material, supporting the inference made from the appearance of the deposit.
Written by: Colin Dundas

All of the images produced by HiRISE and accessible on this site are within the public domain: there are no restrictions on their usage by anyone in the public, including news or science organizations. We do ask for a credit line where possible: Image: NASA/JPL/University of Arizona

For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.