Image PSP_001926_2185 shows part of an unnamed crater located in the Northern Plains.

The intriguing landforms in the floor of this crater are known as "concentric crater fill." Such landforms are found at high latitudes (approximately above 30^o from the equator), where theoretical calculations indicate that ice may exist under the surface, mixed with rocks and soil. Examples of concentric crater fill were first observed in the 1970s, in images acquired by cameras on board the Viking orbiters.

The roughly concentric ridges and throughs in the crater's floor are believed to result from compression caused by viscous flow of a thick mixture of rocks, soils, and ice inward from the crater's walls.

Impact craters with concentric fill are usually shallower than other craters. The crater shown here is approximately 12 km (7.5 miles) in diameter, and 200-400 m (220-440 yards) deep; other Martian craters of similar diameter but without concentric fill may be as deep as 700 m (765 yards). Unlike in "regular" craters, the slopes of the walls of craters with concentric fill tend to be convex, and the crater's rim is more rounded.

All these characteristics are consistent with deformation of an ice-rock mixture similar to what's observed in rock glaciers on Earth.
Written by: Sara Martinez-Alonso

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.