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A.A. Sickafoose, J.E. Colwell, M. Horányi, S. Robertson (LASP, Univeristy of Colorado)
There are many examples of active dust transport near surfaces in the solar system: dust grains suspended above the lunar surface, spokes observed in Saturn's rings, and recent images of infilled craters from the NEAR spacecraft at Eros. Electrostatic dust levitation and transport have also been theorized to occur on Mercury, asteroids, and comets. Dusty regoliths are produced by the interplanetary micrometeoroid flux on nearly all airless bodies in the solar system. Therefore, understanding dust charging, levitation, and dynamics above surfaces is important for interpreting remote sensing data and analyzing the evolution of most planetary surfaces. The interaction between charged dust particles and a plasma sheath above a surface is one proposed mechanism for dust levitation and transport on bodies throughout the solar system.
We report the results of experiments on the levitation and transport of dust particles in an argon plasma sheath above a flat, conducting surface. Levitation experiments are performed using monodisperse polystyrene DVB microbeads. Transport experiments are performed using JSC-1, a lunar regolith simulant, and JSC-Mars-1, a martian regolith simulant. Plasma characteristics are determined using a Langmuir probe, while the sheath potential profiles are measured by an emissive probe. Dust particles levitating above the surface of the plate are illuminated by an Ar laser and observed by a video camera. Various types and sizes of particles can levitate above the plate, and particle dynamics in the plasma sheath can be quite complex. We find that particle levitation height and corresponding charge are comparable to the values calculated from orbital motion limited (OML) theory. We also derive an equation to describe the evolution of the dust distribution on the plate as a result of transport in the plasma sheath.
This work is supported by NASA's Microgravity Fluid Physics Program and NASA's Office of Space Sciences GSRP.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.