Boundary condition controls on the high-sand-flux regions of Mars.

Matthew Chojnacki,Maria E Banks,Lori K Fenton,Anna C Urso

doi:10.1130/g45793.1

Matthew Chojnacki, Maria E Banks + Show 2 more

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https://doi.org/10.1130/g45793.1

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Abstract

Wind has been an enduring geologic agent throughout the history of Mars, but it is often unclear where and why sediment is mobile in the current epoch. We investigated whether eolian bed-form (dune and ripple) transport rates are depressed or enhanced in some areas by local or regional boundary conditions (e.g., topography, sand supply/availability). Bedform heights, migration rates, and sand fluxes all span two to three orders of magnitude across Mars, but we found that areas with the highest sand fluxes are concentrated in three regions: Syrtis Major, Hellespontus Montes, and the north polar erg. All regions are located near prominent transition zones of topography (e.g., basins, polar caps) and thermophysical properties (e.g., albedo variations); these are not known to be critical terrestrial boundary conditions. The two regions adjacent to major impact basins (Hellas and Isidis Planitia) showed radially outward upslope winds driving sand movement, although seasonally reversing wind regimes were also observed. The northern polar dunes yielded the highest known fluxes on the planet, driven by summer katabatic winds modulated by the seasonal CO2 cap retreat-processes not known to affect terrestrial dunes. In contrast, southern dune fields (<45°S) were less mobile, likely as a result of seasonal frost and ground ice suppressing sand availability. Results suggest that, unlike on Earth, large-scale topographic and thermophysical variabilities play a leading role in driving sand fluxes on Mars.

Highlights

For most of the history of Mars, eolian processes have been one of the leading factors in landscape evolution, in contrast to Earth and early Mars, where aqueous processes prevailed
Mars, finding that the largest fluxes are driven by boundary conditions distinct from those on Earth
The locations of Syrtis Major, Hellespontus Montes, and the north polar erg are all near prominent topographic boundaries, which have strong thermal gradients that likely contribute to seasonal winds and, in turn, high sand mobility

Summary

Introduction

For most of the history of Mars, eolian processes have been one of the leading factors in landscape evolution, in contrast to Earth and early Mars, where aqueous processes prevailed. The numerous extraneous environmental factors on planetary bodies with atmospheres (e.g., transport capacity, sand supply, topography) operate nonlinearly to produce self-organized bed forms that evolve in response to environmental conditions (e.g., Kocurek and Lancaster, 1999; Ewing and Kocurek, 2010). Recognition of these underlying boundary conditions can provide insight into landscape evolution on Mars because eolian processes have played a major role there for most of its history (Armstrong and Leovy, 2005)

Results

Discussion

Conclusion