Frosted ground and the southern hemisphere in late fall. This image was acquired within two weeks of the winter solstice, when the sub-solar latitude is at its northernmost position. At this location in time, the sun barely peaks over the horizon in the mid-afternoon, when MRO passes overhead, and carbon dioxide frost is building up on most of the surface. In enhanced color, the frost appears blue. The surface that face north receive more heat from the sun and appear reddish, indicating less frost is present. There may also be a small amount of water frost on the surface. Mars is very different from Earth, and that its main atmosphere component can condense onto the surface. The nitrogen that dominates Earth's atmosphere never condenses onto the surface, although nitrogen in the atmospheres of frigid triton and Pluto do form surface frost and ice.