Craters as sand traps: Dynamics, history, and morphology of modern sand transport in an active Martian dune field


Kirby D. Runyon; Jean-Philippe Avouac

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Aeolian transport of sand is abundant on modern-day Mars, as revealed by remote sensing measurements of the motion of dunes, and of the meter-scale ripples that mantle them. We study a large-scale natural sand trap within the Meroe Patera dune field: a 1.8-km diameter crater which features a dune-free “shadow” in its lee. We compare the volume of sand trapped within this crater to the sand volume that would be expected to cover the area of the crater and its dune-free shadow behind it if the crater were not present. We find that the crater holds less sand than this “missing” volume would predict, implying that sand escapes from the crater over time, and that there likely is not a population of sand grains moving through the Meroe dune field with enough energy to skip over dune slipfaces, such as via suspension. Modern day imagery shows an apparent lack of sand escaping from the Meroe crater, however, suggesting that changes in the wind regime at the site may have allowed sand to escape in the past. Alternatively, if strong winds are impacting the upwind-facing crater wall in the modern day, it is possible that a portion of the sand blown into the crater is rapidly blown out over the downwind wall with a flux too high to permit accumulation and bedform formation. The persistence of an altered dune morphology all the way to the far downwind edge of the dune field suggests consistent wind conditions over the time of the crater-dune field interaction. The dune field in this area is ~14,000 years old, and the formation of the crater predates the arrival of the dunes.


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Sand dune and ripple migration rates, dune and ripple sizes and fluxes, and dune positions downwind for Meroe Patera dune field, Mars.

Uploaded by runyokd1 on Sept. 6, 2019, 7:59 p.m.
Last modified Sept. 6, 2019, 7:59 p.m.