Dunes within a crater on Mars are visible in this HiRISE image. This crater is located in the southern hemisphere where it was winter at the time this image was taken.

This observation documents new seasonal processes occurring on dunes at this latitude, as well as other interesting phenomena. The bright tones are interpreted as carbon dioxode or water frost. This is generally concentrated on the east-facing slopes of the dunes, which are in shadow and therefore cooler. Some dark spots on the dunes may be areas that have defrosted more than surrounding terrain.

Landslides and dark-toned streaks are seen on many of the west-facing dune slopes. The general dune morphology indicates formation by westerly winds. However, zooming in on the image shows smaller scale ripples that appear to have been formed by winds blowing from the south and north.

Written by: Nathan Bridges/Kelly Kolb

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.