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Carbonates in the Martian meteorite Allan Hills 84001 formed at 18 ± 4 °C in a near-surface aqueous environment

Halevy, Itay and Fischer, Woodward W. and Eiler, John M. (2011) Carbonates in the Martian meteorite Allan Hills 84001 formed at 18 ± 4 °C in a near-surface aqueous environment. Proceedings of the National Academy of Sciences of the United States of America, 108 (41). pp. 16895-16899. ISSN 0027-8424. PMCID PMC3193235.

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Despite evidence for liquid water at the surface of Mars during the Noachian epoch, the temperature of early aqueous environments has been impossible to establish, raising questions of whether the surface of Mars was ever warmer than today. We address this problem by determining the precipitation temperature of secondary carbonate minerals preserved in the oldest known sample of Mars’ crust—the approximately 4.1 billion-year-old meteorite Allan Hills 84001 (ALH84001). The formation environment of these carbonates, which are constrained to be slightly younger than the crystallization age of the rock (i.e., 3.9 to 4.0 billion years), has been poorly understood, hindering insight into the hydrologic and carbon cycles of earliest Mars. Using “clumped” isotope thermometry we find that the carbonates in ALH84001 precipitated at a temperature of approximately 18 °C, with water and carbon dioxide derived from the ancient Martian atmosphere. Furthermore, covarying carbonate carbon and oxygen isotope ratios are constrained to have formed at constant, low temperatures, pointing to deposition from a gradually evaporating, subsurface water body—likely a shallow aquifer (meters to tens of meters below the surface). Despite the mild temperatures, the apparently ephemeral nature of water in this environment leaves open the question of its habitability.

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Fischer, Woodward W.0000-0002-8836-3054
Additional Information:© 2011 National Academy of Sciences. Edited by Mark H. Thiemens, University of California San Diego, La Jolla, CA, and approved September 2, 2011 (received for review June 10, 2011). Published online before print October 3, 2011. We thank N. Kitchen for assistance with the isotopic analyses. We thank two anonymous reviewers for valuable comments that have improved this work. I.H. was funded by a Texaco Postdoctoral Fellowship (Division of Geological and Planetary Sciences, Caltech). J.M.E. acknowledges funding from National Aeronautics and Space Administration and National Science Foundation-Division of Earth Sciences. Author contributions: I.H. and J.M.E. designed research; I.H. performed research; I.H. contributed new reagents/analytic tools; I.H., W.W.F., and J.M.E. analyzed data; and I.H., W.W.F., and J.M.E. wrote the paper.
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Caltech Division of Geological and Planetary Sciences Texaco Postdoctoral Fellowship UNSPECIFIED
Issue or Number:41
PubMed Central ID:PMC3193235
Record Number:CaltechAUTHORS:20111107-115454537
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:27653
Deposited By: Jason Perez
Deposited On:08 Nov 2011 19:21
Last Modified:03 Oct 2019 03:25

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