This image shows the changing seasonal frost patterns on Louth Crater, located at latitude 70 N. This crater contains a mound covered by water frost that persists throughout the year, which is unusual for this latitude.

The seasonal carbon dioxide frost deposited during northern winter can also reach this latitude. At the time this image was acquired in northern spring, the carbon dioxide frost is in the process of sublimating back into the atmosphere.

There are sand dunes near the edge of the mound, which become clear of frost in the summer. This subimage shows a comparison of these dunes acquired in late northern summer ( PSP_001700_2505, top) with the newer image. It is hard to believe this is the same piece of ground because the brightness patterns are so different due to the large temperature changes throughout the year.
Written by: Alfred McEwen

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.