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May 16, 2014: How does sand move on Mars? Possible solutions to some long-standing mysteries

Posted on Mar 20, 2014 in Seminars

Jasper Kok (UCLA)

Much of the martian surface is covered by dunes, ripples, and other features formed by saltation, the blowing of sand by wind. In addition, Mars’ atmosphere is loaded with large quantities of mineral dust, much of which is likely emitted by saltation occurring in the ubiquitous Martian dust storms and dust devils. Yet, despite the obvious importance of sand transport to shaping the climate and surface of Mars, several enigmatic questions remain regarding the occurrence and properties of martian saltation. Foremost among these is the puzzling finding that both lander measurements and atmospheric circulation models indicate that wind speeds on Mars rarely exceed the threshold wind speed required to initiate saltation. How then does sand transport appear to be so common on Mars? Furthermore, bedforms observed by rovers contain particles so small that they should be easily suspended by turbulence and thus would be unable to form bedforms. Finally, the minimal size of martian dunes is over an order of magnitude smaller than would be expected from scaling up terrestrial analog dunes. Starting from the basic physics of saltation, this talk provides some possible solutions to these varied mysteries surrounding sand movement on Mars.