This HiRISE image shows a section of Arcadia Planitia, part of the northern plains of Mars. The plains are extremely smooth at large scale. As seen here, they are knobby and rough up close. The surface texture is likely related to several processes involving subsurface ground ice.

Sublimation (a direct transition from ice to gas, without melting to form liquid water) may be partly responsible; large parts of the Martian mid-latitudes have been mantled with a layer believed to be icy dust. This ice is now being lost in the current dry climate causing the ground to collapse slightly, leaving behind a knobby surface.

Another indication of icy ground is the array of cracks found in several parts of the image. These cracks are due to seasonal thermal contraction of frozen ground, creating stresses that fracture the surface. The cracks can form geometric patterns that interact with topography. Such fracture patterns are one of the most common landform in permafrost on Earth. There are also a few large, enigmatic mounds which may be ice-related; these are currently being studied by the HiRISE team.
Written by: Colin Dundas

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.