Martian dunes indicative of wind regime shift in line with end of ice age

Orbital observations suggest that Mars underwent a recent 'ice age' (roughly 0.4-2.1 million years ago), during which a latitude-dependent ice-dust mantle (LDM)1,2 was emplaced. A subsequent decrease in obliquity amplitude resulted in the emergence of an 'interglacial period'1,3 during which the lowermost latitude LDM ice4-6 was etched and removed, returning it to the polar cap. These observations are consistent with polar cap stratigraphy1,7, but lower- to mid-latitude in situ surface observations in support of a glacial-interglacial transition that can be reconciled with mesoscale and global atmospheric circulation models8 is lacking. Here we present a suite of measurements obtained by the Zhurong rover during its traverse across the southern LDM region in Utopia Planitia, Mars. We find evidence for a stratigraphic sequence involving initial barchan dune formation, indicative of north-easterly winds, cementation of dune sediments, followed by their erosion by north-westerly winds, eroding the barchan dunes and producing distinctive longitudinal dunes, with the transition in wind regime consistent with the end of the ice age. The results are compatible with the Martian polar stratigraphic record and will help improve our understanding of the ancient climate history of Mars9.

From Macro- to Microscale: A combined modelling approach for near-surface wind flow on Mars at sub-dune length-scales

The processes that initiate and sustain sediment transport which contribute to the modification of aeolian deposits in Mars’ low-density atmosphere are still not fully understood despite recent atmospheric modelling. However, detailed microscale wind flow modelling, using Computational Fluid Dynamics at a resolution of <2 m, provides insights into the near-surface processes that cannot be modeled using larger-scale atmospheric modeling. Such Computational Fluid Dynamics simulations cannot by themselves account for regional-scale atmospheric circulations or flow modifications induced by regional km-scale topography, although realistic fine-scale mesoscale atmospheric modeling can. Using the output parameters from mesoscale simulations to inform the input conditions for the Computational Fluid Dynamics microscale simulations provides a practical approach to simulate near-surface wind flow and its relationship to very small-scale topographic features on Mars, particularly in areas which lack in situ rover data. This paper sets out a series of integrated techniques to enable a multi-scale modelling approach for surface airflow to derive surface airflow dynamics at a (dune) landform scale using High Resolution Imaging Science Experiment derived topographic data. The work therefore provides a more informed and realistic Computational Fluid Dynamics microscale modelling method, which will provide more detailed insight into the surface wind forcing of aeolian transport patterns on martian surfaces such as dunes.