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Xu Wang: Plasma-Dust Interactions at Airless Planetary Bodies

NASA-SSERVI’s Institute for Modeling Plasmas, Atmospheres and Cosmic Dust (IMPACT)
Laboratory for Atmospheric and Space Physics (LASP)
University of Colorado – Boulder

Space is filled with plasma and cosmic dust particles. Their interactions cause dust particles to be charged and coexist with plasma, forming a ‘dusty plasma’. Dusty plasma exists across the universe, such as in protoplanetary disks, planetary rings, comet dust tails and the Earth’s high-altitude noctilucent clouds. Airless bodies, including the Moon, asteroids, most moons of other planets and distant comets, spread throughout our solar system. Many of these bodies are covered by a layer of fine dust particles, called regolith. Due to direct interactions with solar wind plasma or magnetospheric plasmas as well as solar radiation, dust particles on the regolith surface are charged and may be mobilized, lofted and transported due to the electrostatic force.

The first possible evidence of electrostatic dust lofting/transport was the observations of the ‘lunar horizon glow’ by several Surveyor landers back to the Apollo era. Since then, many other observations on the Moon and other airless bodies have been related to such electrostatic phenomenon. Laboratory and theoretical works have been conducted to study dust charging and transport on surfaces. However, the fundamental mechanism about how dust can obtain enough charge to be lofted remained unsolved for five decades. Recently, a new charging theory developed based on the advanced laboratory experiments has revolutionized our understanding. Several important properties of electrostatically lofted dust have been characterized through laboratory experiments, which provide more insight into the role of electrostatic dust transport in the surface evolution of airless bodies across the solar system. Driven by these laboratory discoveries, a new dust instrument – Electrostatic Dust Analyzer is under development, which aims to find ground truth about this phenomenon on the lunar surface. These scientific results also enable the development of a new dust mitigation technology for future lunar and Martian surface exploration.