Primordial clays on Mars formed beneath a steam or supercritical atmosphere

  • Nature volume 552, pages 8891 (07 December 2017)
  • doi:10.1038/nature24657
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On Mars, clay minerals are widespread in terrains that date back to the Noachian period (4.1 billion to 3.7 billion years ago)1,2,3,4,5. It is thought that the Martian basaltic crust reacted with liquid water during this time to form hydrated clay minerals3,6. Here we propose, however, that a substantial proportion of these clays was formed when Mars’ primary crust reacted with a dense steam or supercritical atmosphere of water and carbon dioxide that was outgassed during magma ocean cooling7,8,9. We present experimental evidence that shows rapid clay formation under conditions that would have been present at the base of such an atmosphere and also deeper in the porous crust. Furthermore, we explore the fate of a primordial clay-rich layer with the help of a parameterized crustal evolution model; we find that the primordial clay is locally disrupted by impacts and buried by impact-ejected material and by erupted volcanic material, but that it survives as a mostly coherent layer at depth, with limited surface exposures. These exposures are similar to those observed in remotely sensed orbital data from Mars1,2,3,4,5. Our results can explain the present distribution of many clays on Mars, and the anomalously low density of the Martian crust in comparison with expectations.

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Thanks to M. Rutherford, T. Hiroi and J. Bosenberg for assistance with experiments and instrumental measurements. Discussions with R. Milliken were helpful in identifying clay minerals in the altered samples.

Author information


  1. Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island 02912, USA

    • Kevin M. Cannon
    • , Stephen W. Parman
    •  & John F. Mustard
  2. Department of Physics, University of Central Florida, Orlando, Florida 32816, USA

    • Kevin M. Cannon


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K.M.C. and S.W.P. conceived the study; K.M.C. undertook the alteration experiments and interpreted the results along with J.F.M.; K.M.C. developed the crustal evolution model and wrote the paper; all authors read the paper and contributed comments.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Kevin M. Cannon.

Reviewer Information Nature thanks F. McCubbin, L. Schaefer and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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