Investigation of dust transport on the lunar surface in a laboratory plasma with an electron beam

摘要

There is much evidence indicating dust levitation and transport on or near the lunar surface. Dust mobilization is likely to be caused by electrostatic forces on charged lunar dust particles. We describe a series of experiments in which a small dust patch is placed on an electrically floating graphite surface in plasma. The effects of an electron beam on electric fields above/across the dust surface are studied for understanding the mechanism leading to dust transport. When the electron beam current is comparable to the Bohm ion current and the beam energy is sufficiently large, there is a large potential difference between the dust surface and the graphite surface, which creates a horizontal electric field that leads to dust mobilization. The vertical electric field in the sheath above the dust surface also increases at about an order of magnitude, significantly increasing the dust release rate. Differing secondary electron yields of the graphite surface and the dust patch play an important role in the enhancement of the electric fields. Imaging of JSC-Mars-1 dust placed on the graphite surface shows spreading of the dust and deposition on the top of an adjacent insulating block, indicating both horizontal and vertical dust transport.