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Science 3 July 2009:
Vol. 325. no. 5936, pp. 64 - 67
DOI: 10.1126/science.1172466
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Reports

Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site

M. H. Hecht,1,* S. P. Kounaves,2 R. C. Quinn,3 S. J. West,4 S. M. M. Young,2,{dagger} D. W. Ming,5 D. C. Catling,6,7 B. C. Clark,8 W. V. Boynton,9 J. Hoffman,10 L. P. DeFlores,1 K. Gospodinova,2 J. Kapit,2 P. H. Smith9

The Wet Chemistry Laboratory on the Phoenix Mars Lander performed aqueous chemical analyses of martian soil from the polygon-patterned northern plains of the Vastitas Borealis. The solutions contained ~10 mM of dissolved salts with 0.4 to 0.6% perchlorate (ClO4) by mass leached from each sample. The remaining anions included small concentrations of chloride, bicarbonate, and possibly sulfate. Cations were dominated by Mg2+ and Na+, with small contributions from K+ and Ca2+. A moderately alkaline pH of 7.7 ± 0.5 was measured, consistent with a carbonate-buffered solution. Samples analyzed from the surface and the excavated boundary of the ~5-centimeter-deep ice table showed no significant difference in soluble chemistry.

1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
2 Department of Chemistry, Tufts University, Medford, MA 02155, USA.
3 SETI Institute, NASA Ames Research Center, Moffett Field, CA 94035, USA.
4 Invensys Process Systems, Foxboro, MA 02035, USA.
5 Astromaterials Research and Exploration Science Directorate, NASA Johnson Space Center, Houston, TX 77058, USA.
6 Department of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol BS8 1RJ, UK.
7 Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA.
8 Space Science Institute, Boulder, CO 80301, USA.
9 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
10 Department of Physics, University of Texas at Dallas, Richardson, TX 95080, USA.

{dagger} Present address: Chemistry Department, University of New Hampshire, Durham, NH 03824, USA.

* To whom correspondence should be addressed. E-mail: michael.h.hecht{at}jpl.nasa.gov

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
H2O at the Phoenix Landing Site.
P. H. Smith, L. K. Tamppari, R. E. Arvidson, D. Bass, D. Blaney, W. V. Boynton, A. Carswell, D. C. Catling, B. C. Clark, T. Duck, et al. (2009)
Science 325, 58-61
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Science. ISSN 0036-8075 (print), 1095-9203 (online)