Light induced erosion of dusty planetesimals and Mars: μg experiments

Abstract

In a number of recent experiments it was found that dust beds continuously eject small, micron sized particles under illumination at low ambient pressure. The ejection is caused by temperature gradients within the illuminated dust bed, which induce lifting forces based on thermal creep or photophoresis. In microgravity experiments we observed that the ejection rate depends inversely on the gravity level. Therefore, the effect is much more effecient in low gravity environments. This mechanism can help to understand processing of dust in protoplanetary disks, where it leads to the ejection of particles from an inward drifting body which would be lost to the star otherwise. The mechanism also supports entrainment of dust into the martian atmosphere. Windspeeds are in general too low to pick up dust from the surface by gas drag alone. In contrast to gas drag light induced drag increases in strength at low ambient pressure and has a maximum in the mbar range prevailing on Mars. The interplay of gas drag and light induced lift might explain the existence of dust devils and dust storms on Mars.