Ice sublimation on Mars. Satellite image of the surface of Mars, showing the effects of ice sublimation on a longitudinal dune in the far southern hemisphere. The ice is frozen carbon dioxide that sublimates (going directly from a solid to a gas) during the Martian spring. Here, this sublimation has eroded the surface and produced the ripple formations seen here. The bright patches are still covered in ice and the dark regions are frost-free. Imaged by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter (MRO) satellite.