Viscous flow rates of icy topography on the north polar layered deposits of Mars

We investigate the importance of viscous flow in shaping topography at the north polar layered deposits (NPLD) of Mars by using finite element modeling to calculate the distribution of stresses and flow velocities. Present-day impact craters on the NPLD are too small and cold for viscous relaxation to have been an important mechanism in controlling their current dimensions; this effect may be ignored when analyzing crater size-frequency distributions. Scarps at the NPLD margins, where avalanches of dust and carbon dioxide frost occur, are sufficiently steep, high, and warm to experience significant viscous flow. We find flow velocities at the base of these steep scarps on the order of tens to hundreds of cm/yr, which are fast enough to significantly affect their slope over kiloyear timescales. Alternatively, the scarps could be close to steady state in which observed block falls provide a competing effect to viscous flow.