Thermal creep assisted dust lifting on Mars: Wind tunnel experiments for the entrainment threshold velocity

In this work we present laboratory measurements on the reduction of the threshold friction velocity necessary for lifting dust if the dust bed is illuminated. Insolation of a porous soil establishes a temperature gradient. At low ambient pressure this gradient leads to thermal creep gas flow within the soil. This flow leads to a sub-surface overpressure which supports lift imposed by wind. The wind tunnel was run with Mojave Mars Simulant and air at 3, 6 and 9 mbar, to cover most of the pressure range at martian surface levels. Our first measurements imply that the insolation of the martian surface can reduce the entrainment threshold velocity between 4 % and 19 % for the conditions sampled with our experiments. An insolation activated soil might therefore provide additional support for aeolian particle transport at low wind speeds.