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Spectral identification of hydrated sulfates on Mars and comparison with acidic environments on Earth

Published online by Cambridge University Press:  10 June 2005

Janice L. Bishop
Affiliation:
SETI Institute, 515 N. Whisman Road, Mountain View, CA 94043, USA e-mail: jbishop@seti.org NASA-Ames Research Center, Exobiology Branch, Moffett Field, CA 94035, USA
M. Darby Dyar
Affiliation:
Mount Holyoke College, 50 College Street, South Hadley, MA 01075, USA
Melissa D. Lane
Affiliation:
Planetary Science Institute, 1700 E. Fort Lowell Rd., Suite 106, Tucson, AZ 85719, USA
Jillian F. Banfield
Affiliation:
Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA

Abstract

We interpret recent spectral data of Mars collected by the Mars Exploration Rovers to contain substantial evidence of sulfate minerals and aqueous processes. We present visible/near-infrared (VNIR), mid-IR and Mössbauer spectra of several iron sulfate minerals and two acid mine drainage (AMD) samples collected from the Iron Mountain site and compare these combined data with the recent spectra of Mars. We suggest that the sulfates on Mars are produced via aqueous oxidation of sulfides known to be present on Mars from Martian meteorites. The sulfate-rich rock outcrops observed in Meridiani Planum may have formed in an acidic environment similar to AMD environments on Earth. Because microorganisms are typically involved in the oxidation of sulfides to sulfates in terrestrial AMD sites, sulfate-rich rock outcrops on Mars may be a good location to search for evidence of life on that planet. Whether or not life evolved on Mars, following the trail of sulfate minerals is likely to lead to aqueous processes and chemical weathering. Our results imply that sulfate minerals formed in Martian soils via chemical weathering, perhaps over very long time periods, and that sulfate minerals precipitated following aqueous oxidation of sulfides to form the outcrop rocks at Meridiani Planum.

Type
Research Article
Copyright
2005 Cambridge University Press

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