Electrostatic Repulsion of Dust from Planetary Surfaces

TL;DR

This study experimentally investigates how electrostatic forces can lift dust particles from planetary surfaces, showing that electrostatic repulsion can facilitate dust ejection and influence atmospheric dust dynamics.

Contribution

It provides experimental evidence and a model for electrostatic dust lifting, highlighting its significance in planetary surface processes.

Findings

Electrostatic charging occurs rapidly on dust aggregates.

Repulsive electrostatic forces can overcome adhesion to lift particles.

Electrostatic effects can lower wind speed thresholds for dust saltation.

Abstract

Surfaces of planetary bodies can have strong electric fields, subjecting conductive grains to repulsive electrostatic forces. This has been proposed as mechanism to eject grains from the ground. To quantify this process, we study mm-sized basalt aggregates consisting of micrometer constituents exposed to an electric field in drop tower experiments. The dust aggregates acquire high charges on sub-second timescales while sticking to the electrodes according to the field polarity. Charging at the electrodes results in a repulsive (lifting) force and continues until repulsion overcomes adhesion and particles are lifted, moving towards the opposite electrode. Some aggregates remain attached, which is consistent with a maximum charge limit being reached, providing an electrostatic force too small to counteract adhesion. All observations are in agreement with a model of moderately conductive grains with a small but varying number of adhesive contacts to the electrodes. This supports the idea that on planetary surfaces with atmospheres, electrostatic repulsion can significantly contribute to airborne dust and sand, i.e. decrease the threshold wind speed that is required for saltation and increase the particle flux as suggested before.