A layered stack of dusty ice up to 2 miles (3 kilometers) thick lies at the north pole of Mars, as seen by the Mars Reconnaissance Orbiter.
Troughs in the ice deposits reveal different inner layers that are thought to indicate climate changes on Mars when the layers were formed. This particular scarp face sits at the start of a large canyon known as Chasma Boreale, which cuts through the polar layered deposits.
The section of layered deposits here also reflects unusual layers of sand as well as layers of dusty ice. Terrain features called cross-beds appear in the sandy layer, indicating that each layer was originally a dune field that later became covered with ice.
-- NASA/JPL/University of Arizona and SPACE.com Staff
Credit: NASA/JPL/University of Arizona