Electrostatic Dust Control and Collection on Planetary Surfaces

The Significance of Dust: Dust studies have already been identified as crucial components of missions to the Moon, Mars, asteroids, and Mercury over the next decade [1,2]. Detailed study of the physical and chemical nature of the fine particulate portion of regoliths of planetary bodies is a key to understanding micrometeorite bombardment and the nature of re-golith formation [e.g., 3]. The Problematic Nature of Dust: During Apollo landings, extensive locally-induced stirring of the re-golith caused dust to be suspended long enough to come into contact with conducting surfaces [4,5]. Dust behaved like abrasive Velcro: it adhered to everything and attempts to remove it by simply brushing did not remove fines (<10 µ) and resulted in severe abrasion. Lunar fines, because of their electrostatic charging, were relatively difficult to collect in sample bags along with other size range particles. Within hours, seals were broken, samples contaminated, and portions of the samples, especially fines, lost [6]. Because of this difficulty, details on lunar dust are relatively sparse [7,8]. These issues must be resolved for future missions (4,5,6). The lunar regolith is an impact-generated soil-like layer above bedrock dominated by particles ranging in size from centimeter to submicron scales [7,8]. Extensive remelting generates abrasive shard-like particles which are highly irregular , angular, sharp, elongated (1:3 axis length ratio), and with high specific surface area (8 times as much surface area as a population of spheres with equivalent particle size distribution). Particles have reentrant hook-like projections, are highly anisotropic, porous, and compressible, aligning along long axes. Ten to twenty percent of the collected soil particles, called the lunar fines, or dust, are below 10 microns in size. Fines are systematically less mafic in composition, higher in silicic and felsic components [7,9,10]. Metallic iron abundance and magnetic susceptibility increase with decreasing grain size in mare soils [6]. A question remains as to how much variation in magnetic susceptibility is present among all lunar fines, including highland and mixed highland/mare soils, as well as non-lunar fines. The strategies initially implemented to deal with lunar dust failed [4,5]. A currently proposed strategy based increased magnetic susceptibility in lunar fines [6] may not work uniformly well for fines of non-mare, or non-lunar, composition. The successful strategy will deal with dust dynamics resulting from interaction between mechanical and electrostatic forces. Electrostatic Nature of Dust: Fields, charged particles , and dust particle interactions on the Moon are complex, their interactions …