This image from the HiRISE camera aboard the Mars Reconnaissance Orbiter shows an “inverted” crater within an ice-rich debris apron just south of a mountain on Mars. Ice deposits beneath and within the soil – recently discovered using ground-penetrating radar – cause the terrain to move, distorting the landforms within it over time. As the ice sublimates and refreezes the ground around it shifts, resulting in folds, grooves…and sometimes the deformation of craters. Here’s another such example.
Read more on the University of Arizona’s HiRISE site.
Image: NASA/JPL/University of Arizona