This image gives a rare glimpse of an area in the far south of Mars that is frequently obscured by clouds or covered by surface frosts.

Crescent-shaped sand dunes can be seen scattered across patterned ground. The surface patterns are made up of channels carved by carbon dioxide gas as it escapes from under the seasonal frost. The dunes were still partially frozen when this picture was taken during the vernal equinox, as the Sun moved into the northern hemisphere at the end of the southern summer. Bluish ice is visible on the steep faces of the dunes and along their bases.

Typical sand dunes on Earth and Mars gradually move downwind as sand accumulates on the upwind (convex) side and then avalanches down the steeper down-wind side, called the “slip face”. Here, the sand motion appears to be around the dunes instead. Clean patches of ground downwind of the dunes show that the surface is sheltered by the dunes, which prevent dark sand from being deposited in their lees.


Written by: Paul Geissler

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.