Thermally Driven Winds on Mars: A Review and a Slope Effect Numerical Study

Regional and local thermally driven winds are planetary boundary layer phenomena frequently observed on Mars over sloping and flat regions, when diurnal surface temperature variations are significant and large‐scale winds are sufficiently weak. In particular, slope flows are prevalent in many areas on Mars, where they can reach high speeds and have a substantial impact on the near‐surface wind patterns, pressure diurnal cycle, aeolian activity, etc. This work first reviews literature on Martian winds, listing wind speeds obtained either numerically or from in situ measurements, with special emphasis on slope flows. Second, a methodology is presented to perform numerical simulations of slope flows on Mars using the open‐source computational fluid dynamics code OpenFOAM. Slope winds are then studied in a simplified Martian mountain‐valley configuration, using realistic values for various parameters, such as the slope angle and temperature variation. The incompressible Navier‐Stokes equations with Boussinesq approximation are used, along with the k‐ɛ Reynolds‐averaged Navier‐Stokes turbulence model. Radiant heat transfer is included and proven to be paramount for a correct description of Martian slope winds. Results of velocity and temperature profiles are obtained for various slope angles. These simulations aim to provide further insight on the behavior of slope winds on Mars, to simplify the process of assessing numerous potential landing sites for upcoming missions, since these highly regular winds could be useful, for instance, for dust removal applications. Plain Language Summary Thermal winds, which are caused by differences in temperature between areas, happen frequently on Mars, namely, when the temperature changes significantly during the day and there is not much wind on a larger scale. These winds are especially common in mountains and valleys, and are then called slope winds. They can reach rather high speeds, and thus affect the winds close to the surface, the changes in air pressure throughout the day, and the movement of sand and dust. This study looks at existing information about winds on Mars, including their speeds, as obtained from measurements and/or computer simulations, with a special interest for slope winds. We then model these winds using a specialized computer code, and show how the wind speed is affected by the steepness of the slopes. These simulations help to better understand how slope winds work on Mars, which could be an asset