Martian Dust

Newman, Clare E.; Bertrand, Tanguy; Fenton, Lori K.; Guzewich, Scott D.; Jackson, Brian; Lewis, Stephen; Mischna, Michael A.; Montabone, Luca and Wellington, Danika (2021). Martian Dust. Reference Module in Earth Systems and Environmental Sciences, Elsevier.

DOI: https://doi.org/10.1016/B978-0-12-818234-5.00143-7

Abstract

The Martian dust cycle is the primary driver of atmospheric and surface variability in the arid, low-surface pressure climate of present-day Mars. Martian dust is ubiquitous across the surface, produces Mars's characteristic rusty color, and, in the modern era, may derive primarily from one huge, wind-eroded sedimentary deposit. Lofted dust absorbs solar radiation, increasing atmospheric temperatures, and emits thermal radiation, warming the surface at night. Rearrangement of surface dust via dust lifting and deposition modifies albedo, hence patterns of surface heating. Strong winds and dust devils are likely the main causes of dust lifting, although it is unknown whether most dust is lifted directly by winds (as individual grains or aggregates) or via saltation of sand-sized particles. Other key unknowns include threshold wind stresses for particle motion, how dust fluxes relate to atmospheric conditions, and how dust is transported through the boundary layer. Positive feedbacks between dust lifting, radiative heating, and circulation strength and surface winds give rise to rapid increases in dust lifting that produce dust storms. Some storms remain local and only last a few sols, others expand to become regional, while global storms are produced by multiple regional storms merging and/or new lifting sites developing across Mars. Global storms, which last several Earth months and occur three times per Mars decade on average, have the greatest impact on climate: strengthening the global circulation, modifying atmospheric waves, and transporting more dust and water vapor to high altitudes. Yet the strong interannual variability in storm occurrence, onset timing, and location, remain poorly understood. Improved observations of dust lifting, boundary layer processes, and ice nucleation on dust particles, plus greater understanding of the role of surface dust availability and dust-ice coupling, are needed to better represent major storms in Mars climate models. Monitoring the evolution of dust storms continuously and simultaneously at global scale from orbit is required to better understand the processes and feedbacks responsible for their growth and decay. In addition, such observations are needed to provide initial conditions for future Mars weather forecasting systems.

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