Electrostatic lofting of dust aggregates near the terminator of airless bodies and its implication for the formation of exozodiacal disks

Abstract

Our current knowledge of launching dust grains from the surfaces of airless bodies appears to contradict in situ observations of dust grains that are lofted off the surface of the Moon. We tackle the issue of high grain stickiness where cohesive forces estimated for compact spherical grains restrict the detachment of the grains from the surfaces of airless bodies. We show that electrostatic forces on irregular grains with rough surfaces, in particular, aggregates of the grains could overcome their cohesive forces, provided that their surfaces are hydroxylated. We also discuss the dynamical consequences of the detachment as to the possibility of grains׳ hovering over the surfaces of airless bodies. Our results suggest that lofting and hovering of lunar agglutinates take place near the terminator of the Moon but not above the surface of asteroid 25143 Itokawa. The application of our results to extrasolar systems reveals a novel mechanism for the supply of dust aggregates into exozodiacal disks around bright main-sequence stars by electrostatic lofting and subsequent radiative blow-out of the aggregates from sub-km sized airless bodies in the orbit around the stars.