Concerning the dissipation of electrically charged objects in the shadowed lunar polar regions

Abstract

NASA recently suggested the construction of a lunar outpost at the south pole near the rim of Shackleton crater. While there are a number of advantages to such a base, the region will have periods of time when there is limited or no solar illumination ‐ thereby reducing photoelectric and solar wind plasma currents compared to most of the lunar dayside. As a consequence of this reduction in environmental currents, we find that human systems charged by contact electrification with the regolith (e.g., roving, excavation) will have increased difficulty in removing accumulated electric charge. This situation is especially true within the cold, shadowed regions adjacent to the terminator (such as within Shackleton crater itself) where there are essentially no photoelectric currents, vastly reduced plasma currents (due to the local wake) and a highly‐reduced regolith conductivity. In essence, there is no pathway for accumulated charge to “leak away” or dissipate, thereby creating an electrostatic hazard. Calculated dissipation timescales are found to be ∼1 millisecond in the weakly sunlit terminator region and dayside but could approach 100's of seconds in the “current‐starved” shadowed regions.