Geologic map of the Lunae Palus Quadrangle of Mars

Mars presents two different terrains, a highly cratered surface that lies mostly in the southern hemisphere and sparsely cratered plains that lie mostly in the northern hemisphere. The cause of the dichotomy is a still unsolved fundamental problem of Martian geology, analogous to the problem of continents and ocean basins in terrestrial geology. The present features of the plains in particular reflect a varied history in which superficially similar landforms may have had very different origins. The Lunae Palus quadrangle is occupied mainly by plains and their variety is perhaps more evident than elsewhere. This map demarcates units inferred to have different geologic histories on the basis of their appearance in Mariner 9 wide- and narrow-angle television frames.