Measuring Ripple and Dune Migration in Coprates Chasma, Valles Marineris: A Source to Sink Aeolian System on Mars?
Active aeolian systems are present across the martian surface, with active dune fields commonly found in depressions such as craters and valleys. There are many dune fields within the equatorial region of Mars, including Valles Marineris, but the effects of topography on wind regimes and consequently dune migration in Valles Marineris is poorly understood. We investigated both the ripple and dune migration in a dune field in Coprates Chasma using High Resolution Science Experiment Images (HiRISE) and Context Camera (CTX) images. Migration rates of dune brinks and ripples were measured over varying time scales, between Earth years 2007-2014. The dunes here are some of the tallest on Mars, with heights of up to 182 m. The dune brinks are migrating eastwards at a rate of 0.1-0.3 m/EY through the valley due to topographical influences on the local winds. Potential sediment sources for the dune field were identified and investigated by studying thermal inertia and mineralogy. The topographic slope related katabatic winds travel down the valley walls and converge with the dominant winds traveling through the center of the valley, causing overall eastwards dune migration. Topography is likely the dominant control on the local wind regime; slope winds travel down the sides of the valley walls and are funneled through the center of the valley. These local winds subsequently facilitate the migration of the large dunes in Coprates Chasma, thus expanding our understanding of local winds in the Martian environment.