This observation from NASA's Mars Reconnaissance Orbiter shows an excellent example of what is called 'fretted terrain,' termed so because of the eroded appearance of the surface.

This observation shows an excellent example of what is called "fretted terrain," termed so because of the eroded appearance of the surface.

What causes this kind of terrain? One explanation is the sublimation of subsurface ground ice that goes directly from a solid state to a gaseous one. When that occurs, the material is removed and the ground can collapse in a jumbled pattern. The curving ridges and lineations could be indicative of slow movement of the ice-rich material, perhaps in a way that has similarities to rock glaciers on Earth.

HiRISE is one of six instruments on NASA's Mars Reconnaissance Orbiter. The University of Arizona, Tucson, operates the orbiter's HiRISE camera, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter Project for the NASA Science Mission Directorate, Washington.

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