Gypsum, bassanite, and anhydrite at Gale crater, Mars

David T. Vaniman, Germán M. Martínez, Elizabeth B. Rampe, Thomas F. Bristow, David F. Blake, Albert S. Yen, Douglas W. Ming, William Rapin, Pierre Yves Meslin, John Michael Morookian, Robert T. Downs, Steve J. Chipera, Richard V. Morris, Shaunna M. Morrison, Allan H. Treiman, Cherie N. Achilles, Kevin Robertson, John P. Grotzinger, Robert M. Hazen, Roger C. WiensDawn Y. Sumner

Research output: Contribution to journalArticlepeer-review

93 Scopus citations


Analyses by the CheMin X-ray diffraction instrument on Mars Science Laboratory show that gypsum, bassanite, and anhydrite are common minerals at Gale crater. Warm conditions (∼6 to 30 °C) within CheMin drive gypsum dehydration to bassanite; measured surface temperatures and modeled temperature depth profiles indicate that near-equatorial warm-season surface heating can also cause gypsum dehydration to bassanite. By accounting for instrumental dehydration effects we are able to quantify the in situ abundances of Ca-sulfate phases in sedimentary rocks and in eolian sands at Gale crater. All three Ca-sulfate minerals occur together in some sedimentary rocks and their abundances and associations vary stratigraphically. Several Ca-sulfate diagenetic events are indicated. Salinity-driven anhydrite precipitation at temperatures below ∼50 °C may be supported by co-occurrence of more soluble salts. An alternative pathway to anhydrite via dehydration might be possible, but if so would likely be limited to warmer near-equatorial dark eolian sands that presently contain only anhydrite. The polyphase Ca-sulfate associations at Gale crater reflect limited opportunities for equilibration, and they presage mixed salt associations anticipated in higher strata that are more sulfate-rich and may mark local or global environmental change. Mineral transformations within CheMin also provide a better understanding of changes that might occur in samples returned from Mars.

Original languageEnglish (US)
Pages (from-to)1011-1020
Number of pages10
JournalAmerican Mineralogist
Issue number7
StatePublished - Jul 26 2018


  • Gypsum
  • Mars
  • Martian Rocks and Minerals
  • Meteorites
  • Orbiters
  • Perspectives from Rovers
  • X-ray diffraction
  • bassanite anhydrite

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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