The global topography of Mars and implications for surface evolution

Elevations measured by the Mars Orbiter Laser Altimeter have yielded a high -accuracy global map of the topography of Mars. Dominant features include t he low northern hemisphere, the Tharsis province, and the Hellas impact bas in. The northern hemisphere depression is primarily a long-wavelength effec t that has been shaped by an internal mechanism. The topography of Tharsis consists of two broad rises. Material excavated from Hellas contributes to the high elevation of the southern hemisphere and to the scarp along the he mispheric boundary. The present topography has three major drainage centers , with the northern Lowlands being the largest. The two polar cap volumes y ield an upper limit of the present surface water inventory of 3.2 to 4.7 mi llion cubic kilometers.