Electrostatic forces on grains near asteroids and comets

Department of Aerospace Engineering, University of Maryland, 3178 Martin Hall, College Park, MD USA 20904

^* e-mail: hartzell@umd.edu

Published online: 30 June 2017

Abstract

Dust on and near the surface of small planetary bodies (e.g. asteroids, the Moon, Mars’ moons) is subject to gravity, cohesion and electrostatic forces. Due to the very low gravity on small bodies, the behavior of small dust grains is driven by non-gravitational forces. Recent work by Scheeres et al. has shown that cohesion, specifically van der Waals force, is significant for grains on asteroids. In addition to van der Waals cohesion, dust grains also experience electrostatic forces, arising from their interaction with each other (through tribocharging) and the solar wind plasma (which produces both grain charging and an external electric field). Electrostatic forces influence both the interactions of grains on the surface of small bodies as well as the dynamics of grains in the plasma sheath above the surface. While tribocharging between identical dielectric grains remains poorly understood, we have recently expanded an existing charge transfer model to consider continuous size distributions of grains and are planning an experiment to test the charge predictions produced. Additionally, we will present predictions of the size of dust grains that are capable of detaching from the surface of small bodies.