This image covers the southern slope of an old impact crater inside a larger and still older crater, in the Martian highlands.

Valley networks are often found on the most ancient Martian terrains, suggesting that Mars was a very different world more than 3 billion years ago. There are two prominent valleys near the center of the image that merge into a single northeast-trending valley (i.e., going to the upper right; be sure to look at the map-projected images that have north up.) There are bright ripples on the floors of the valleys. Although water may have carved these valleys long ago, the ripples are much more recent features created by the wind, which is channelized by the topography.

The terrain is heavily covered by dust or other wind-blown materials, muting the underlying surface features. Bright lines behind some boulders and other topography are called “wind tails” and are deposited in the lee of obstacles, thereby indicating wind direction (most wind tails here seem to extend to the north-northwest from obstacles, indicating winds from the south-southeast). Small, sharp impact craters are best vsibile over the smooth mantled regions; these craters probably formed in just the past few million years, which is very recent in geologic time.
Written by: Alfred

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.