This HiRISE image shows the complex, gullied western wall of a kilometer-deep impact crater in the Terra Sirenum region. This is an interesting crater because it appears to be mantled by the fluidized ejecta blanket of a slightly smaller crater just to the west.

A diverse set of gullies originate at multiple elevations along the crater wall. Prominent gullies have incised through the overlying ejecta into the upper walls to reveal numerous resistant dark layers. The floors of these gullies display a host of interesting features, including braided middle reaches, cut banks, channel bars, and stream terracing. These are all features suggestive of water flow.

Miniature gully systems, less than a kilometer long, start much further downslope than the larger gullies yet display the usual gully attributes, including theater-headed alcove source regions, incised middle reaches, and overlapping alluvial fans at their lower reaches. Detailed studies of these and other gully systems should help to elucidate the gully formation mechanisms.
Written by: Ginny Gulick

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.