HiRISE: Icy surface of the north polar cap

At Mars’ north pole is a dome of icy layers ranging up to 2 kilometers thick, roughly analogous to the Earth’s ice caps in Greenland or Antarctica. Although not visible here, the dome is characterized by incised spiraling troughs that reveal sequences of layers thought to reflect varying climate conditions over the time they were originally deposited. This image is of an area on the top surface of the polar dome between the troughs — vast, generally smooth, flat plains composed of a thin layer of very pure water ice….. [More at link]