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Science 3 July 2009:
Vol. 325. no. 5936, pp. 58 - 61
DOI: 10.1126/science.1172339

Reports

H2O at the Phoenix Landing Site

P. H. Smith,1,* L. K. Tamppari,2 R. E. Arvidson,3 D. Bass,2 D. Blaney,2 W. V. Boynton,1 A. Carswell,4 D. C. Catling,5 B. C. Clark,6 T. Duck,7 E. DeJong,2 D. Fisher,8 W. Goetz,9 H. P. Gunnlaugsson,10 M. H. Hecht,2 V. Hipkin,11 J. Hoffman,12 S. F. Hviid,9 H. U. Keller,9 S. P. Kounaves,13 C. F. Lange,14 M. T. Lemmon,15 M. B. Madsen,16 W. J. Markiewicz,9 J. Marshall,17 C. P. McKay,18 M. T. Mellon,19 D. W. Ming,20 R. V. Morris,20 W. T. Pike,21 N. Renno,22 U. Staufer,23 C. Stoker,18 P. Taylor,24 J. A. Whiteway,24 A. P. Zent18

The Phoenix mission investigated patterned ground and weather in the northern arctic region of Mars for 5 months starting 25 May 2008 (solar longitude between 76.5° and 148°). A shallow ice table was uncovered by the robotic arm in the center and edge of a nearby polygon at depths of 5 to 18 centimeters. In late summer, snowfall and frost blanketed the surface at night; H2O ice and vapor constantly interacted with the soil. The soil was alkaline (pH = 7.7) and contained CaCO3, aqueous minerals, and salts up to several weight percent in the indurated surface soil. Their formation likely required the presence of water.

1 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
2 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
3 Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA.
4 Optech Incorporated, Vaughan, Ontario L4K 5Z8, Canada.
5 University of Bristol, Bristol BS8 1RJ, UK, and Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA.
6 Space Science Institute, Boulder, CO 80301, USA.
7 Dalhousie University, Halifax, Nova Scotia B3H 1Z9, Canada.
8 Geological Survey of Canada and University of Ottawa, Ottawa, Ontario K1A 0E8, Canada.
9 Max Planck Institute for Solar System Research, 31791 Katlenburg-Lindau, Germany.
10 Institute of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark.
11 Canadian Space Agency, Saint-Hubert, Quebec J3Y 8Y9, Canada.
12 University of Texas–Dallas, Richardson, TX 75080, USA.
13 Tufts University, Medford, MA 02155, USA.
14 University of Alberta, Edmonton, Alberta T6G 2H1, Canada.
15 Texas A&M University, College Station, TX 77843, USA.
16 Earth and Planetary Physics, University of Copenhagen, 2100 Copenhagen, Denmark.
17 SETI Institute, Mountain View, CA 94043, USA.
18 NASA Ames Research Center, Mountain View, CA 94035, USA.
19 University of Colorado, Boulder, CO 80309, USA.
20 NASA Johnson Space Center, Houston, TX 77058, USA.
21 University of Michigan, Ann Arbor, MI 48109, USA.
22 Imperial College, London SW7 2AZ, UK.
23 Institute of Microtechnology, University of Neuchâtel, 2002 Neuchâtel, Switzerland, and Micro and Nano Engineering Laboratory, Delft University of Technology, 2628 CD Delft, Netherlands.
24 York University, Toronto, Ontario M3J 1P3, Canada.

* To whom correspondence should be addressed. E-mail: psmith{at}lpl.arizona.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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