The Role of Eolian Processes in Forming Surface Featuresof the Martian Polar Layered Deposits

The major topographic features of the martian polar layered deposits include the conspicuous spiral troughs, subtle undulations, broad reentrants (chasma), steep, arcuate scarps, and dune fields. A prominent role for eolian processes in the formation of all of these features is proposed. Strong katabatic winds occur on the north polar cap, producing widespread frost streaks. These cold drainage winds are analogous to those on the terrestrial Antarctic cap. In the chasmae convergent katabatic winds create yardangs and erode arcuate scarps in the layered deposits that are also the source for local dune fields migrating outward from the polar cap. The chasmae are postulated to originate by long-term erosion by katabatic wind. Wind plays a role in formation of the troughs and scarps primarily through removal of dust freed from exposed layered deposits by ablation of ice on defrosted equator-facing slopes. The undulations are created by interaction between surface erosion or deposition of perennial ice and standing waves in the shallow katabatic windflow. The south polar layered deposits exhibit topographic features similar to those at the north polar cap, but erosion and depositional processes creating these features may be inactive during the current epoch because of the lack of an extensive perennial ice cover and associated katabatic wind. c © 2000 Academic Press