Understanding Formative Winds of Intracrater Aeolian Dunes on Mars
Abstract
The modern Martian landscape is primarily dominated by aeolian processes, with dune migrations and sand fluxes comparable to terrestrial values. Despite the significantly lower atmospheric density, many of the same Earth-wind processes and transport laws still apply. Mars is also punctuated with thousands of craters, many containing active dune fields, ripples, and other aeolian landforms. Wind patterns and sediment supply within these craters determine the shape, size, and migration patterns of these dunes. Here we study the end-member atmospheric phenomena that produce these intracrater dunes: katabatic and convective winds. Both are caused by the daily heating and cooling of the near-surface atmosphere, with the former produced by nocturnal gravity flows along crater walls, and the latter by extreme free convection in the afternoon allowing geostrophic momentum transfer to the dunes. Dune orientations collected from NASA's High Resolution Imaging Experiment (HiRISE), which serve as proxies for local wind direction, are compared to slope flow directions inferred from the Mars Orbiter Laser Altimeter (MOLA) and simulated large-scale regional wind directions from the Mars Climate Database (MCD). We find no clear global preferential alignment towards either local slope flows, or non-local climate wind. We develop a simple theory for katabatic flow and the impact threshold of sediment transport, and use it to examine the propensity for katabatic vs. climatic flows to move sand. This theory reveals the relative importance of each in terms of their contribution to dune orientations on Mars. We find that latitude and seasonality play important roles in forming the aeolian dunes that inhabit Martian craters.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMEP0180005C
- Keywords:
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- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 3346 Planetary meteorology;
- ATMOSPHERIC PROCESSES;
- 5405 Atmospheres;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 5415 Erosion and weathering;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS