The lower part of this image shows well-defined overlapping channels, which have inverted topography (i.e., they were once low spots that have been filled in with sediments and now eroded in a such a way that they appear as topographically high regions).

The channels have a winding and intersecting geometry indicating the shifting of the channels over time, a feature consistent with the flow of water in rivers. The channels have small craters that have excavated the channel materials and ejected them to form well-defined rays. There are dark slope streaks (toward the top of the image) showing transport of fine dust down the slope of an eroded bedrock terrain.
Written by: John Grotzinger

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.