The role of sublimation for the formation of the northern ice cap: Resultsfrom the Mars Orbiter Laser Altimeter

The evolutionary history of the martian ice caps is practically known, and the caps are key to understanding the climatic history of Mars. Sublimation and ice flow are two hypotheses that have recently been suggested to expla in the observed form of the northern ice cap. Here we present a sublimation model and compare the shape of the cap obtained from this model with Mars Orbiter Laser Altimeter (MOLA) observations of the north polar region. This model can reproduce the shape of the cap and individual troughs. Sublimati on is an important process as are how and wind erosion. We were able to con strain the time scales of sublimation only to about two orders of magnitude (1-100 million years). This estimate depends on many unknown parameters, s uch as friction velocity and wind speed over the ice caps. These can be det ermined only by direct measurement over the surface. (C) 2000 Academic Pres s.