Seasonal Variations in Airflow Over the Namib Dune, Gale Crater, Mars: Implications for Dune Dynamics

Abstract

Dune length scale airflow modeling provides new insights on eolian bedform response and complex near-surface 3-D wind patterns not previously resolved by mesoscale models. At a 1-m surface resolution, Curiosity wind data are used to investigate the eolian environment of the Namib dune on Mars, providing improved seasonal constraints on grainfall, grainflow activity, and ripple migration. Based on satellite images, airflow patterns, and surface shear stress, enhanced eolian activity, and slipface advancement occurs during early springtime. Autumn and winter winds are also favorable to eolian activity, but minimal movement was detected in satellite images overlapping with wind data. During the summer, the migration of large stoss ripples on the Namib dune may augment sediment deposition on the slipface. These results provide a better understanding of the overall migration pattern of the Namib dune, which can be extrapolated to other dunes in the Bagnold Dune Field.Plain Language Summary At 1-m resolution, small-scale airflow modeling can provide new insights into sediment transport and dune migration on Mars. Coupled with wind data collected by the Curiosity rover, this study provides improved, realistic constraints on Martian sediment movement and illustrates how ripples seasonally form and migrate according to changing wind speeds and directions. The spring season with northerly winds is the most influential for dune migration based on modeling results and satellite monitoring, but the quieter summer and autumn seasons with southeasterly winds continue to facilitate ripple migration, which may help maintain slower rates of dune migration despite the opposing wind direction. Based on modeling results, the winter season with high-magnitude northerly winds should produce migration rates similar to spring, but according to satellite monitoring, dune migration stops. Small amounts of frost in between sand grains on the dune surface may be responsible for this halt in dune migration. These results can be applied to other dunes in the Bagnold Dune Field, which likely experience the same seasonal patterns in sediment transport.

Landforms Associated With the Aspect‐Controlled Exhumation of Crater‐Filling Alluvial Strata on Mars

“…We suspect that the formation of bench‐and‐slope and nose topography from the erosion of fluvial strata, rather than fluvial ridges, might be unique to crater‐filling strata. Winds in craters with actively eroding fills have been found to be unidirectional at locations, steered by crater topography (Day et al., 2016), though with seasonality (Cornwall et al., 2018). If unimodal winds are associated with a preferred direction of scarp retreat, and if eolian erosion rates are also sensitive to lithology as has been shown on Earth and Mars (Pain et al., 2007; Pain & Oilier, 1995; Williams et al., 2007), we hypothesize this may generate landforms distinct from fluvial ridges during the erosion of alluvial stratigraphy.…”