Most debris on crater walls slides straight downhill. In this HiRISE image we see examples of boulders that have bounced downhill, not necessarily vertically.

A prominent example looks like a dotted line from the top of the crater wall where the boulder took off to the crater floor where it finally came to rest.

Numerous boulders have slid partway down toward the crater floor, which is covered by sand dunes. This is actually a small crater (~1 km wide) within an un-named but much larger ~30 km crater.

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.