Dynamics of electrostatically lofted dust on airless planetary bodies
Résumé
The dynamics of lofted dust on airless bodies have been the subject of much study since the 1960s, when the lunar horizon glow was first observed. Lofted dust dynamics have important implications for the evolution of an airless body's surface properties. To date, most of these studies have had to rely on assumptions of initial conditions of the lofted dust grains due to a lack of experimental results. In this paper, we present a study of lofted dust grains, making use of initial conditions obtained from recent laboratory results. Additionally, we distinguish between photoemission rates from isolated dust grains and from the bulk regolith. We explore dust lofting dynamics across a large size range of dust grains (0.1 to 10 μm) and the surface gravity of their parent bodies (0.0001 to 1 lunar g). Charging and lofting results reveal a complex interplay between the grain size, gravity, initial charge, and the various charging currents. It is shown that the sheath electric field becomes increasingly significant in the lofted dust dynamics as the gravitational field decreases. Due to the initial negative charge of dust grains lofted from a positively charged regolith surface, their lofting heights are found to be generally reduced compared to uncharged grains with similar initial speeds. We show that micron-sized dust grains can be lofted to high altitudes and even escape from smaller bodies, leading to the loss of fine-grained materials from the surface.