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The first X-ray diffraction measurements on Mars

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      The X-ray diffraction/X-ray fluorescence instrument CheMin on the Curiosity rover is a shoebox-sized device using transmission geometry and an energy-discriminating CCD detector. The instrument has returned the first X-ray diffraction data for soil and drilled samples from Mars outcrops, revealing a suite of primary basaltic minerals, amorphous components and varied hydrous alteration products including phyllosilicates.


      The Mars Science Laboratory landed in Gale crater on Mars in August 2012, and the Curiosity rover then began field studies on its drive toward Mount Sharp, a central peak made of ancient sediments. CheMin is one of ten instruments on or inside the rover, all designed to provide detailed information on the rocks, soils and atmosphere in this region. CheMin is a miniaturized X-ray diffraction/X-ray fluorescence (XRD/XRF) instrument that uses transmission geometry with an energy-discriminating CCD detector. CheMin uses onboard standards for XRD and XRF calibration, and beryl:quartz mixtures constitute the primary XRD standards. Four samples have been analysed by CheMin, namely a soil sample, two samples drilled from mudstones and a sample drilled from a sandstone. Rietveld and full-pattern analysis of the XRD data reveal a complex mineralogy, with contributions from parent igneous rocks, amorphous components and several minerals relating to aqueous alteration. In particular, the mudstone samples all contain one or more phyllosilicates consistent with alteration in liquid water. In addition to quantitative mineralogy, Rietveld refinements also provide unit-cell parameters for the major phases, which can be used to infer the chemical compositions of individual minerals and, by difference, the composition of the amorphous component.

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      Author and article information

      [a ]Geological Sciences, Indiana University, 1001 E. 10th Street, Bloomington, IN 47405, USA
      [b ]NASA Ames Research Center, USA
      [c ]Planetary Science Institute, USA
      [d ]inXitu, USA
      [e ]University of Hawaii at Manoa, USA
      [f ]Chesapeake Energy, USA
      [g ]NASA Jet Propulsion Laboratory, USA
      [h ]University of Arizona, USA
      [i ]Arizona State University, USA
      [j ]CNRS, France
      [k ]NASA Johnson Space Center, USA
      [l ]Lunar and Planetary Institute, USA
      Author notes
      Correspondence e-mail: bish@
      International Union of Crystallography
      01 November 2014
      21 October 2014
      21 October 2014
      : 1
      : Pt 6 ( publisher-idID: m140600 )
      : 514-522
      25485131 4224469 yu5005 10.1107/S2052252514021150 IUCRAJ S2052252514021150
      © David Bish et al. 2014

      This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

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