Mars: Letters

Nature 436, 66-69 (7 July 2005) | doi:10.1038/nature03640; Received 18 November 2004; Accepted 8 April 2005

Water alteration of rocks and soils on Mars at the Spirit rover site in Gusev crater

Larry A. Haskin1,18, Alian Wang1, Bradley L. Jolliff1, Harry Y. McSween2, Benton C. Clark3, David J. Des Marais4, Scott M. McLennan5, Nicholas J. Tosca5, Joel A. Hurowitz5, Jack D. Farmer6, Albert Yen7, Steve W. Squyres8, Raymond E. Arvidson1, Göstar Klingelhöfer9, Christian Schröder9, Paulo A. de Souza, Jr10, Douglas W. Ming11, Ralf Gellert12, Jutta Zipfel12, Johannes Brückner12, James F. Bell, III8, Kenneth Herkenhoff13, Phil R. Christensen6, Steve Ruff6, Diana Blaney7, Steven Gorevan14, Nathalie A. Cabrol15, Larry Crumpler16, John Grant17 & Lawrence Soderblom13

Gusev crater was selected as the landing site for the Spirit rover because of the possibility that it once held a lake. Thus one of the rover's tasks was to search for evidence of lake sediments1. However, the plains at the landing site were found to be covered by a regolith composed of olivine-rich basaltic rock and windblown 'global' dust2. The analyses of three rock interiors exposed by the rock abrasion tool showed that they are similar to one another, consistent with having originated from a common lava flow3, 4, 5, 6, 7, 8. Here we report the investigation of soils, rock coatings and rock interiors by the Spirit rover from sol (martian day) 1 to sol 156, from its landing site to the base of the Columbia hills. The physical and chemical characteristics of the materials analysed provide evidence for limited but unequivocal interaction between water and the volcanic rocks of the Gusev plains. This evidence includes the softness of rock interiors that contain anomalously high concentrations of sulphur, chlorine and bromine relative to terrestrial basalts and martian meteorites9; sulphur, chlorine and ferric iron enrichments in multilayer coatings on the light-toned rock Mazatzal; high bromine concentration in filled vugs and veins within the plains basalts; positive correlations between magnesium, sulphur and other salt components in trench soils; and decoupling of sulphur, chlorine and bromine concentrations in trench soils compared to Gusev surface soils, indicating chemical mobility and separation.

  1. Department of Earth and Planetary Sciences, Washington University in Saint Louis, Missouri 63130, USA
  2. Department of Earth & Planetary Sciences, University of Tennessee, Knoxville, Tennessee 37996, USA
  3. Lockheed Martin Space Systems, Littleton, Colorado 80125, USA
  4. Exobiology Branch, MS 239-4, NASA Ames Research Center, Moffett Field, California 94035, USA
  5. Department of Geosciences, State University of New York, Stony Brook, New York 11794-2100, USA
  6. Department of Geological Sciences, Arizona State University, Box 876305, Tempe, Arizona 85287, USA
  7. JPL, 4800 Oak Grove Drive, Pasadena, California 91109, USA
  8. Cornell University, 428 Space Science Buildings, Ithaca, New York 14853, USA
  9. Institut für Anorganische und Analytische Chemie, Johannes Gutenberg-Universität, Staudinger Weg 9, D-55128 Mainz, Germany
  10. Companhia Vale do Rio Doce, 20030-900 Rio de Janeiro, RJ, Brazil
  11. NASA JSC, MC KR, 2101 NASA Parkway, Houston, Texas 77058, USA
  12. Abteilung Kosmochemie, Max-Planck-Institut für Chemie, Postfach 3060, Mainz, Germany
  13. USGS Flagstaff, 2255 North Gemini Drive, Flagstaff, Arizona 86001, USA
  14. Honeybee Robotics, New York, New York 10012, USA
  15. SETI Institute and Space Science Division, MS 245-3, NASA Ames Research Center, Moffett Field, California 94035, USA
  16. New Mexico Museum of Natural History and Science, 1801 Mountain Road, Albuquerque, New Mexico 87104, USA
  17. Smithsonian Institution, Washington DC 20024, USA
  18. ‡Deceased

Correspondence to: Alian Wang1 Correspondence and requests for materials should be addressed to A.W. (Email: alianw@levee.wustl.edu).

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