Two distinctly different terrain types are visible in this image of the northern lowlands of Mars.

An older, heavily cratered landscape has been inundated by much younger flows. The valley floors are filled with flows that have relatively smooth surfaces and very few superposed impact craters.

In contrast, the mesas and hills making up the older terrain have blocky surfaces, perhaps fragmented by ancient impacts. The smooth surfaces of the flows are punctuated by curved, subparallel fractures oriented transverse to the flow direction. These cracks resemble crevasses in terrestrial glaciers and were formed when the brittle solid crust of the flow fractured as it was dragged downstream. Detailed images such as this will help determine the role ice may have played in these flows.
Written by: Paul Geissler

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.