SPECTRAL REFLECTANCE PROPERTIES OF ...

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3Department of Geosciences,. Franklin and Marshall College, P.O. Box 3003, Lancaster, Pennsylvania, USA 17604-3003. ([email protected]).
Lunar and Planetary Science XXXI

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SPECTRAL REFLECTANCE PROPERTIES OF COMMON ZEOLITES. E. A. Cloutis1, P. M. Asher2, S. A. Mertzman3, and M. Guertin1. 1Department of Geography, University of Winnipeg, 515 Portage Ave., Winnipeg, MB, Canada R3B 2E9 ([email protected]), 2Department of Geology and Geography, Georgia Southern University, P.O. Box 8149, Statesboro, Georgia, USA 30460-8149 ([email protected]). 3Department of Geosciences, Franklin and Marshall College, P.O. Box 3003, Lancaster, Pennsylvania, USA 17604-3003 ([email protected]).

Introduction: The spectral reflectance properties of a range of zeolites have been investigated. The purpose was to determine the range of spectral variability which this class of minerals exhibits and whether they exhibit diagnostic absorption bands which might permit their identification in Mars spectra. Zeolites can be formed by a number of processes, including hydrothermal alteration, and hence could be present on the Martian surface [1]. The presence and identity of zeolites on Mars would allow us to address issues of atmospheric and volatile evolution on Mars [2]. There are a number of lines of evidence supporting the plausibility of zeolites on Mars, including: their presence in terrestrial basaltic/volcanic regions [3]; presence in cold desert soils, including those derived from basalts [4,5]; and models of weathering [6]. From terrestrial analog studies and weathering models, the most important zeolites which may be present on Mars include chabazite, phillipsite, clinoptilolite, and mordenite [3-5]. Experimental Procedure: A range of zeolite samples, including those listed above, have been characterized by reflectance spectroscopy, atomic absorption/emission, wet chemistry, XRF, and XRD. The samples were obatined from the Smithsonian Institution National Museum of Natural History (NMNH). Reflec-

tance spectra were measured at the NASA-supported RELAB facility at Brown University. The spectra were measured from 0.3-26 µm relative to halon (0.32.6 µm; 5 nm spectral resolution; i=30°, e=0°) and brushed gold (2.5-26 µm; 4 cm-1 spectral resolution; i=30°, e=30°) [6]. Spectra were merged in the 2.5-2.6 µm overlap region. A variety of grain sizes were measured: