
This map centered on the north pole of Mars is based on gamma rays from the element hydrogen--mainly in the form of water ice. Regions of high ice content are shown in violet and blue and those low in ice content are shown in red. The very ice-rich region at the north pole is due to a permanent polar cap of water ice on the surface. Elsewhere in this region, the ice is buried under several to a few tens of centimeters of dry soil. (Image Credit: NASA/JPL/UA)