This image shows a beautifully preserved alluvial fan located on the southern interior wall of Holden Crater.

The ridges on the fan surface radiate from the apex and are "inverted channels" that once supplied the fan with sediment. The scalloped distal edges show an impressive cross-section through a layered sequence providing scientists with insight into the geologic history of this crater and climate conditions on early Mars.

As detailed by Grant et al. (Geology, 2008) from previously released adjacent images (PSP_003077_1530, PSP_00344_1530 and others), Holden provides evidence for two very different types of water-rich depositional environments on ancient Mars. The older, lower layers in the fan are thin, continuous and clay-rich and were likely deposited in long-standing body of water. By contrast, the younger units at the top of the fan are very jumbled and are characteristic of sediment that was deposited in shorter-lived, higher-energy floods.

Holden Crater is one of six remaining landing site candidates for NASA's Mars Science Laboratory rover, a mission scheduled for launch in 2011.
Written by: Sharon Purdy

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.