Avalanche slope angles in low-gravity environments from active Martian sand dunes

The properties of granular material have an important effect on surface landforms and processes. Recently, it has been suggested that material properties called dynamic and static angle of repose vary with gravitational acceleration, which would have a significant effect on many planetary surface processes such as crater collapse and gully formation. In order to test that hypothesis, we measured lee slopes of active aeolian sand dunes on Mars using the High Resolution Imaging Experiment (HiRISE) DTMs (Digital Terrain Model). We examined dune fields in Nili Patera, Herschel Crater, and Gale Crater. Our measurements showed that the dynamic angles of repose for the sands in these areas are 33-34° in the first region and 30-31° in the other two. These results fall within the 30° to 35° window for the dynamic angles of repose for terrestrial dunes with similar flow depths and grain properties and thus show that this angle does not significantly vary with decreasing gravity. Key Points The dynamic angle of repose of granular material does not vary with gravity Angle of dune's slipface has implications for grain roughness and angularity Slip face angle gives qualitative measure of the distance from the sand's source