How to Snowboard on Mars

Monday, 15 December 2014: 1:40 PM
Jim McElwaine, University of Durham, Earth Sciences, Durham, DH1, United Kingdom, Serina Diniega, NASA Jet Propulsion Laboratory, Pasadena, CA, United States, Candice J Hansen, Planetary Science Institute Albuquerque, Albuquerque, NM, United States and Mary C Bourke, Trinity College Dublin, Dublin, Ireland
Long, narrow grooves found on the slopes of martian sand dunes have
been cited as evidence of liquid water via the hypothesis that
melt-water initiated debris flows eroded channels and deposited
lateral levées. However, this theory has several short-comings for
explaining the observed morphology and activity of these linear
gullies. We present an alternative hypothesis that is consistent with
the observed morphology, location, and current activity: that blocks
of carbon dioxide ice break from over-steepened cornices as
sublimation processes destabilize the surface in the spring, and these
blocks move downslope, carving out levéed grooves of relatively
uniform width and forming terminal pits. To test this hypothesis, we
describe experiments involving water and carbon dioxide blocks on
terrestrial dunes and then compare results with the martian
features. We present a theoretical model of the initiation of block
motion due to sublimation and use this to quantitatively compare the
expected behavior of blocks on the Earth and Mars. The model
demonstrates that carbon dioxide blocks can be expected to move via
our proposed mechanism on the Earth and Mars, and the experiments show
that the motion of these blocks will naturally create the main
morphological features of linear gullies seen on Mars.