Mars: Letters

Nature 436, 62-65 (7 July 2005) | doi:10.1038/nature03807; Received 23 November 2004; Accepted 29 April 2005

Indication of drier periods on Mars from the chemistry and mineralogy of atmospheric dust

Walter Goetz1, Preben Bertelsen2, Charlotte S. Binau2, Haraldur P. Gunnlaugsson3, Stubbe F. Hviid1, Kjartan M. Kinch3, Daniel E. Madsen2, Morten B. Madsen2, Malte Olsen2, Ralf Gellert4,5, Göstar Klingelhöfer5, Douglas W. Ming6, Richard V. Morris6, Rudolf Rieder4, Daniel S. Rodionov5,7, Paulo A. de Souza, Jr5,8, Christian Schröder5, Steve W. Squyres9, Tom Wdowiak10 & Albert Yen11

The ubiquitous atmospheric dust on Mars is well mixed by periodic global dust storms, and such dust carries information about the environment in which it once formed and hence about the history of water on Mars1. The Mars Exploration Rovers have permanent magnets to collect atmospheric dust for investigation by instruments on the rovers2, 3. Here we report results from Mössbauer spectroscopy and X-ray fluorescence of dust particles captured from the martian atmosphere by the magnets. The dust on the magnets contains magnetite and olivine; this indicates a basaltic origin of the dust and shows that magnetite, not maghemite, is the mineral mainly responsible for the magnetic properties of the dust. Furthermore, the dust on the magnets contains some ferric oxides, probably including nanocrystalline phases, so some alteration or oxidation of the basaltic dust seems to have occurred. The presence of olivine indicates that liquid water did not play a dominant role in the processes that formed the atmospheric dust.

  1. Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, D-37191, Germany
  2. Niels Bohr Institute, University of Copenhagen, Copenhagen, DK-2100, Denmark
  3. Institute of Physics and Astronomy, University of Aarhus, Aarhus, DK-8000, Denmark
  4. Max-Planck-Institut für Chemie, Mainz, D-55128, Germany
  5. Institut für Anorganische und Analytische Chemie, J. Gutenberg Universität, Mainz, D-55128, Germany
  6. NASA Johnson Space Center, Houston, Texas 77058, USA
  7. Space Research institute IKI, Moscow, Russia
  8. Companhia Vale do Rio Doce, 29090-900 Vitória, ES, Brazil
  9. Cornell University, Ithaca, New York 14853, USA
  10. University of Alabama, Birmingham, Alabama 35203, USA
  11. Jet Propulsion Laboratory—California Institute of Technology, Pasadena, California 91109, USA

Correspondence to: Walter Goetz1 Correspondence and requests for materials should be addressed to W.G. (Email: goetz@mps.mpg.de)

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