High Sand Fluxes and Abrasion Rates on Mars Determined from HiRISE Images

Abstract

The volumetric transport rate of sand, or flux, is a fundamental parameter that controls the rate of landscape modification. This process is responsible for the movement of ripples and dunes, as well as the abrasion of rocks and landforms. Measuring sand flux on Mars was previously not possible because of the lack of high spatial and temporal resolution images, and appropriate techniques, for making displacement and accurate topographic measurements. These limitations have now been overcome because, 1) It is found that many dunes and ripples on Mars are mobile in High Resolution Imaging Science Experiment (HiRISE) images [1-4], and 2) the application of precise image registration and correlation methods permits the quantification of movement to sub-pixel precision that, when combined with topographic data, can be used to derive the sand flux. Sand transport occurs via two modes, saltation and reptation [5,6]. Saltation occurs in long hops initiated from aerodynamic shear and subsequent propagation as grains are rebounded or ejected downstream. Reptation operates via shorter hops resulting from the "splash" ejection induced by the collision of upwind saltating grains. Reptation contributes to the migration of ripples whereas both processes result in the net movement of dunes. Therefore, by knowing the rate of movement of these bedforms and their volume, the reptation and saltation flux can be estimated. Here, we measure the migration rate of sand ripples and dune lee fronts at Nili Patera, Mars. From these data, we derive the reptation and total (reptation + saltation) fluxes, respectively. The dunes have unexpectedly high sand fluxes that are like those in Victoria Valley, Antarctica, implying that rates of landscape modification on Mars and Earth are similar.

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