Thin flows cover the plains just north of the source region for the Athabasca Valles channel system. The flows are mostly confined by a scarp (cliff) in the northwest corner of the image.

The more heavily cratered terrain above the scarp is part of a tectonic ridge known as a wrinkle ridge. A few flows can be seen atop the wrinkle ridge, but they are not as ubiquitous as those on the plains below. The flows on the plains frequently intersect, with younger ones cutting across older ones.

The prominent dark swathes along their edges have particularly rough textures. The darker shade is due to thousands of shadows cast by small bumps on the surface, which HiRISE is able to resolve. Dozens of bright, narrow rifts (cracks) zigzag across the flows. They appear bright because they are filled with light-toned, windblown material. Wind-sculpted knobs and ridges of similar light-toned material are scattered throughout the imaged area.

The orientations of the ridges indicate that the winds primarily blow from the southeast. Several impact craters are captured in this image, the largest being about 50 meters (160 feet) in diameter. Many bear the distinctive bright rays characteristic of secondary craters associated with the larger impact crater, Zunil.

Some craters penetrated the surface of the flows, and the boulders strewn around them suggest that the material they excavated was rocky.
Written by: W. L. Jaeger

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.