This image shows part of the margin of a pedestal crater. A pedestal crater is a crater with its ejecta standing above the surrounding terrain. These form when an impact crater ejects material which forms a resistant layer. This resistant blanket coats material around the crater, which is thus eroded more slowly than the rest of the region. The result is that both the crater and its ejecta blanket stand above the surroundings.

At this site, only a small part of the edge of the ejecta is visible. The ejecta is eroding, leaving a ragged edge with some detached mesas and buttes. The uppermost layer in the small cliffs is clearly strong and erosion-resistant, as it forms steep and even overhanging edges, ultimately breaking up into boulders which fall down the slopes. This layer armors the underlying material against erosion. Sites like this offer the opportunity to study units of rock that otherwise might have been erased by erosion.
Written by: Colin Dundas

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.