Characterizing Aeolian Sediment Transport on Mars Using In Situ Observations

Wind is one of the major drivers of geomorphic change on terrestrial bodies throughout our solar system. Yet, our understanding of how wind-driven, or aeolian, processes operate under different planetary regimes has been limited by what we can study here on Earth. Prior to robotic exploration of Mars, terrestrially-derived theories predicted that tenuous Martian winds would rarely, if ever, be able to mobilize surface sediment. Once spacecraft arrived at Mars, it became clear that wind was not only a major geomorphic agent, it was likely the most dominant in the planet’s recent geologic history, especially given the paucity of other active surface processes (e.g., hydrology, plate tectonics, or volcanism). Repeat “change detection” images acquired from orbital and landed cameras have provided extensive evidence of ongoing aeolian activity, despite low predicted and measured winds. Here we describe change detection experiments conducted from the Mars Science Laboratory (MSL) Curiosity rover and InSight lander on Mars. These imaging campaigns have provided key information on the nature of aeolian activity occurring under modern Martian climatic conditions. In Gale crater, change detection images have demonstrated a strong seasonality in wind, with a relatively quiescent period during the first half of the year followed by a windy period between Ls 180 – 360◦, consistent with the strong winds predicted in and around southern summer. During this season, formative winds result from a combination of enhanced Hadley flows and thermally driven slope winds, which generate strong northeasterlies at the location of the rover; over long time periods, these flows have caused significant deflation across Aeolis Palus, and have facilitated the development of large dune fields downwind at the base of Mount Sharp. Late in 2018, the InSight lander touched down five hundred kilometers north of Gale crater, in the volcanic plains of Elysium Planitia. Concurrent imaging and atmospheric monitoring have suggested that, at this location, the modern surface is relatively stable and that ongoing aeolian activity may be limited to dust entrainment during convective vortex events. Cumulatively, change detection experiments have provided an unprecedented look at active Martian surface processes, and have shed light on some of the fundamental differences that may exist between Earth and Mars