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

TL;DR

This study demonstrates that insolation-induced thermal creep within Martian soil can lower the wind speed needed for dust lifting, potentially aiding dust transport on Mars.

Contribution

It provides experimental evidence that thermal creep from insolation reduces the dust entrainment threshold on Mars, a factor previously unquantified.

Findings

Insolation reduces threshold velocity by 4-19%.

Thermal creep supports dust lifting at low wind speeds.

Experiments conducted at Mars-like pressures with Mojave Mars Simulant.

Abstract

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.