HR: 0800h
AN: P51D-0948    [Abstracts]
TI: Hyperarid Soils in the Atacama Desert: A Terrestrial Guide to Mars Soil Formation
AU: * Amundson, R
EM: earthy@nature.berkeley.edu
AF: Division of Ecosystem Sciences, 137 Mulford Hall University of California, Berkeley, CA 94720 United States
AU: Stephanie, E
EM: saewing@nature.berkeley.edu
AF: Division of Ecosystem Sciences, 137 Mulford Hall University of California, Berkeley, CA 94720 United States
AU: Justine, O
EM: jowen@nature.berkeley.edu
AF: Division of Ecosystem Sciences, 137 Mulford Hall University of California, Berkeley, CA 94720 United States
AU: Brad, S
EM: skimars@earthlink.net
AF: SETI Institute, MS 245-3 NASA Ames Research Center, Moffett Field, CA 94720 United States
AU: Nishiizumi, K
EM: kuni@ssl.berkeley.edu
AF: Space Sciences Lab, 7 Gauss Way University of California, Berkeley, CA 94720 United States
AU: William, D
EM: bill@eps.berkeley.edu
AF: Earth and Planetary Science, McCone Hall University of California, Berkeley, CA 94720 United States
AU: Chris, M
EM: cmckay@mail.arc.nasa.gov
AF: Space Science Division, MS 245-3 NASA Ames Research Center, Moffett Field, CA 94720 United States
AB: Hyperarid soils on Earth provide a framework for interpreting the growing Mars regolith database and for developing testable hypotheses for the origin of Mars soils. On Earth, dust and aerosol deposition are strongly coupled with soil formation. Long term atmospheric deposition in the Atacama Desert, coupled with small and highly stochastic rain and fog events, produce a set of soil features diagnostic of pedogenic processes and indicative of the direction of liquid water flow: (1) Extreme hyperaridity results in the retention of nearly all atmospheric inputs within the upper 3 m of the soil profile, but the infrequent rainfall events vertically separate salts by solubility, forming polygonally cracked, sulfate-cemented near-surface crusts which overlie variably concentrated layers of the more soluble chloride, nitrate, and Na-sulfate salts. (2) Pedogenic sulfates in the Atacama desert exhibit unique depth-dependent S, O and Ca isotope trends caused by isotopic fractionation during downward aqueous migration and chemical reaction. (3) Pedogenic sulfates and nitrates contain a distinctive mass independent O isotope signal indicative of a tropospheric origin, and in the case of nitrate, the retention of this signal persists only under near-abiotic conditions. Taken together, the morphology and the depth-dependent chemical and isotopic composition of hyperarid soils provides quantitative information on the origin of solutes, direction of water flow, and degree of biological activity. Depth-dependent measures of these parameters on Mars can therefore be used to test a pedogenic hypothesis for the origin of the widely distributed sulfate layers and can be used to design experiments for future missions that may more fully illuminate the history of Mars surface processes.
DE: 0486 Soils/pedology (1865)
DE: 0488 Sulfur cycling
DE: 5415 Erosion and weathering
SC: Planetary Sciences [P]
MN: Fall Meeting 2005