Dr. Brad Sutter

December 22, 2006

"Geochemistry and Mineralogy of Atacama Desert Soils: A Possible Mars Soil Analog"

NNA05CS54A

The geochemistry and mineralogy of Atacama Desert soils is being examined in order to understand sulfur and chlorine, and possible carbonate and nitrate, abundance and distributions in Mars soils, and their relation to soil water activity. The soil formation mechanisms operating in the Atacama that have led to the presence of carbonate and the accumulation of nitrate, sulfate, and chloride in the Atacama soils are being determined. Soil sampling sites will be selected in the Atacama Desert from 24 o S to 27 oS along an arid humid gradient corridor. By choosing soils along the arid-humid gradient, changes in soil properties will be examined as a function of climate. Soils toward the south receive ~15 mm y -1 while soils towards the north receive 2 mm decade -1

Total chemical analyses of soil and rock at the Atacama soil sites will include Si, Al, Fe, Mn, Ca, Mg, K, Na, Zr, Cl, Ti, C, S, nitrate-N, ammonium-N, and inorganic C (carbonate). Mass-balance determinations of selected elements (e.g., Si, Al, S, and Cl) combined with soil strain analyses will provide further information regarding the extent and nature of geochemical weathering processes and soil volume changes that have occurred with soil development in the Atacama (Brimhall and Dietrich, 1987; Chadwick et al., 1990). The mineralogy of each soil sample along with surface rock material will be analyzed by X-ray diffraction (XRD). Mineralogical analyses will indicate what degrees of aqueous activity the soils have experienced.