Impact crater in Arcadia Planitia, Mars, satellite image. This terraced impact crater has two distinct terraces. This implies that there are three layers of material, differing in strength, on the surface, with the terracing occurring at the boundaries of the materials. The different materials are probably layers of ice (weak) and rock (strong). Image obtained by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter (MRO) on 11th August 2013.