Temporal and Geographical Variation in Martian Surface Dust Lifting Processes

Abstract

Numerical experiments were completed examining the variability of key aspects of the Martian dust cycle and investigating their importance in predicting conditions for spacecraft atmospheric descent and landing. The dust cycle – lifting, transportation and deposition – is a significant Martian climate cycle. The geographical and temporal variation in dust lifting processes were investigated using a Martian Global Circulation Model. The geographical representation of Martian dust lifting by wind stress was used to explore the experimental impact of changes in model resolution. It was found that increasing the resolution improved the model's geographical representation of observed dust lifting regions, such as resolving important storm-forming regions in the northern hemisphere. This improvement was unanticipated in the case of changes in vertical resolution, and the horizontal resolution work identified an important length scale for dust lifting (of the order of 100 kilometres). The temporal variation of a dust lifting process was investigated through experiments focusing on the diurnal variability of Martian dust devils (small-scale convective vortices). This research compared results with published lander and rover observations and found that dust devils were more active during morning hours than anticipated, suggesting that the generally accepted description of dust devil behaviour on Mars is incomplete. Predictions were made of the atmospheric and near-surface environment encountered by the ESA ExoMars Schiaparelli landing module. The experiments produced a reasonable representation of atmospheric quantities along the descent trajectory and were able to generate similar low-altitude wind fields to those reported by the spacecraft. The global-scale model also out-performed a higher resolution mesoscale model. These findings are significant in the field of Martian climate modelling, are important for the planning of Martian dust devil observation campaigns and future missions to the planet`s surface, and will also be relevant to researchers operating atmospheric models for other planetary bodies.