COMPOSITIONALLY VARIED ROCK DUST PARTICLES AS TERRESTRIAL ANALOGUES TO MARS MATERIALS: DETERMINING ELECTROSTATIC CHARGE PROPERTIES USING THE E-SPART ANALYZER

NASA missions to Mars confirm presence of surficial particles, as well as dramatic periods of aeolian reworking. Dust deposition on, or infiltration into, exploration equipment such as spacecraft, robotic explorers, solar panel power supplies, and even spacesuits, can pose significant problems such as diminished power collection, short circuits / discharges, and added weight. We report results conducted initially as a high school science fair project [1] and a study now part of an undergraduate research experience. The E-SPART analyzer [2] uses oscillating particles in an acoustic or electric field, or by simultaneous application of both fields. Real time measurement of particle motion is done using laser Doppler velocimetry and/or image analyses [3]. The Materials Group at UALR is developing a miniature, digitally controlled ESPART analyzer where the AC drive frequency is varied depending upon particle size and electrostatic charge distribution. This makes it possible to work with 0.5 – 30 micrometer particle sizes at zero to saturation charge levels, depending upon particle sizes present and environmental conditions. The unit was used for this undergraduate research project first by evaluating Mars dust stimulant JCS Mars-1 [4]. We add our data to that determined using other techniques and conditions [5][6][7] . Since more is now know about the Mars surface compositions from images and data collected by Spirit and Opportunity, we also present particle size and electrostatic results for mechanically eroded particles derived from various terrestrial materials (including quartz and gypsum sands, bauxite, and shale). Aerodynamic particle sizes range from 1 to 50 microns, with charge densities less than 75 micro-Coulombs per gram. Ref: [1] Williams, W. J. W. , et al. (2004) Geo Soc Amer Abs with Prog, Vol. 36, No. 5, Abs# 180-9. [2] Mazumder, M. K. et al. (1991) IEEE Trans and Indust. Appl, 27, No. 4, 611-619. [3] Mazumder et al. (2004) LPS XXXV, Abstract #2022. [4] Allen, C. C. et al. (1998) Proc Conf Amer Soc Civ Eng, 469-476. [5] Zoltán, S. et al. (2002) J. Geophys. Res, 107 (E11), 15-1 to 15-8. [6] Buhler, C. R. et al. (2002) Proceedings of the 39th Space Congress," Cape Canaveral. [7] Fabian, A. et al. (2001) IEEE Trans Plas Sci, 29, No. 2.