With Curiosity roving Mars and probing its surface and atmosphere — the latter via the Rover Environmental Monitoring System (REMS) — Martian climatology has come of age. Indeed, the REMS provides a wealth of weather data such as humidity, pressure, temperature and wind speed.
However, compared with how the Earth's weather is monitored, Martian in situ meteorological data remains extremely scarce. An alternative handle on understanding winds on Mars is provided by looking at sand dunes — specifically, how ripple patterns evolve and dune orientations change over time.
Derek Jackson and colleagues investigated a dunefield in the Proctor Crater area, located in the southern highlands of Mars. The authors performed computational fluid dynamics modelling and reverse engineered the occurring dune dynamics by comparing photos of the area taken two Mars years (3.8 Earth years) apart by the HiRISE camera onboard the Mars Reconnaissance Orbiter satellite. The main finding is a poor correlation between dune ridge orientation and sand-transporting winds (inferred from ripple migration): the overall dune shapes are mostly unaffected by the prevailing winds. In other words, dunes steer the winds, rather than vice versa. The formation of dunes must therefore be due to earlier, different climate conditions — suggesting Martian climate change.
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Verberck, B. Martian dune dynamics. Nature Phys 11, 987 (2015). https://doi.org/10.1038/nphys3603
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DOI: https://doi.org/10.1038/nphys3603
