Horanyi, Mihaly - LUNAR IMPACT EJECTA CLOUDS OBSERVED BY LDEX

Abstract: 
The Lunar Dust Experiment (LDEX) onboard the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission successfully mapped the spatial and temporal variability of the dust size and density distributions in the lunar environment. LDEX reliably detected and measured the mass of submicron and micron sized dust grains, while in lunar orbit from 10/6/2013 - 4/17/2014. LDEX also measured the current from low-energy ions and collective charges from dust impacts that are below the detection threshold for individual dust detection, enabling the search for the putative population of grains with radii ~ 0.1 micron lofted over the terminator regions by plasma effects. LDEX has identified and characterized the dust ejecta cloud that is maintained by the sporadic micrometeoroid bombardment of the lunar surface. The density of the dust ejecta cloud increases with decreasing altitude, and shows significant enhancements during meteor showers. LDEX found no evidence of the plasma-lofted particles, and put strict new upper limits on the density of the high-altitude small grains. 
The discovery and detailed understanding of the lunar ejecta cloud opens new pathways to learn about the dust populations comprising the sporadic background and the meteor showers, as well as the response of the lunar regolith as function of the mass and speed of the bombarding particles.  The collected data will be further used to improve dust hazard models for the near-Earth environment. Ejecta clouds, similar to that observed around the Moon are likely to be present at other objects that are possible targets for future human exploration: asteroids, and the Martian Moons Phobos and Deimos.  An LDEX-type instrument on precursor missions will greatly contribute to the safety of the crew and the mission to these targets.