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Published October 2012 | public
Journal Article

Magmatic precipitation as a possible origin of Noachian clays on Mars

Abstract

Hydrous clay minerals detected on the surface of Mars have been interpreted as indicators of the hydrologic and climatic evolution of the planet. The iron- and magnesium-rich clays described in thick, extensive outcrops of Noachian crust have been proposed to originate from aqueous weathering. This would imply that liquid water was stable at the surface of early Mars, presumably when the climate was warmer and wetter. Here we show that iron- and magnesium-rich clays can alternatively form by direct precipitation from residual, water-rich magma-derived fluids. Infrared reflectance spectra from terrestrial lavas from the Mururoa Atoll (French Polynesia) that underwent this precipitation process are similar to those measured for the Noachian crust. Such an origin is also consistent with the D/H ratio of iron- and magnesium-rich clays in some martian meteorites and the widespread presence of these clays in massive basaltic lavas, breccias and regolith. We propose that the progressive degassing of the martian interior over time and the resultant increasingly water-poor magmatic fluids -and not a cooling climate- may explain the absence of clays in Hesperian-aged and more recent formations.

Additional Information

© 2012 Macmillan Publishers Limited. Received 26 April 2012; accepted 10 August 2012; published online 9 September 2012. This study was supported by the University of Poitiers, the French CNRS-INSU and by a French ANR 'Jeunes Chercheurs' programme (contract no. ANR-09-JCJC-0,106-PorousClay). We are grateful to V. F. Chevrier and B. Hynek for their comments and suggestions that have improved our manuscript. We thank S. Riffault for her contribution to the drawing of Fig. 3. Author contributions: A. Meunier conceived and headed the project. B.L.E. and F.W. contributed to the description of martian geology features and the interpretation of the petrographical characteristics of martian meteorites. The petrographical study of terrestrial basalts was performed by A. Mas and P.D. Infrared spectra were acquired and interpreted by S.P. Finally, B.L.E., F.W., A.E.A. and E.F. provided critical input to the manuscript.

Additional details

Created:
August 22, 2023
Modified:
October 26, 2023