¹Andrew G. Tomkins, ¹Lara Bowlt, ^2,3Matthew Genge, ¹Siobhan A. Wilson, ⁴Helen E. A. Brand, ^1,4,5Jeremy L. Wykes

¹School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria 3800, Australia
²Impact and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, Exhibition Road, London SW7 2AZ, UK
³Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 2BT, UK
⁴Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168, Australia
⁵¹Department of Earth and Planetary Sciences, Macquarie University, North Ryde, New South Wales 2113, Australia

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Reference
Tomkins AG, Bowlt L, Genge M, Wilson SA, Brand HEA, Wykes JL (2016) Ancient micrometeorites suggestive of an oxygen-rich Archaean upper atmosphere. Nature 533, 235–238
Link to Article [doi:10.1038/nature17678]

^1,2J. T. Williams, ^1,3C. K. Shearer, ^1,2Z. D. Sharp, ^1,3P. V. Burger, ^3,4F. M. McCubbin, ^1,3A. R. Santos, ^1,3C. B. Agee, ⁵K. D. McKeegan
¹Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA
²Center for Stable Isotopes, University of New Mexico, Albuquerque, New Mexico, USA
³Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, USA
⁴NASA Johnson Space Center, Mailcode XI2, Houston, Texas, USA
⁵Department of Earth, Planetary, and Space Sciences, UCLA, Los Angeles, California, USA

The Martian meteorites record a wide diversity of environments, processes, and ages. Much work has been done to decipher potential mantle sources for Martian magmas and their interactions with crustal and surface environments. Chlorine isotopes provide a unique opportunity to assess interactions between Martian mantle-derived magmas and the crust. We have measured the Cl-isotopic composition of 17 samples that span the range of known ages, Martian environments, and mantle reservoirs. The 37Cl of the Martian mantle, as represented by the olivine-phyric shergottites, NWA 2737 (chassignite), and Shergotty (basaltic shergottite), has a low value of approximately −3.8‰. This value is lower than that of all other planetary bodies measured thus far. The Martian crust, as represented by regolith breccia NWA 7034, is variably enriched in the heavy isotope of Cl. This enrichment is reflective of preferential loss of 35Cl to space. Most basaltic shergottites (less Shergotty), nakhlites, Chassigny, and Allan Hills 84001 lie on a continuum between the Martian mantle and crust. This intermediate range is explained by mechanical mixing through impact, fluid interaction, and assimilation-fractional crystallization.

Williams JT, Shearer CK, Sharp ZD, Burger PV, McCubbin FM, Santos AR, Agee CB, McKeegan KD (2016) The chlorine isotopic composition of Martian meteorites 1: Chlorine isotope composition of Martian mantle and crustal reservoirs and their interactions. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12647]
Published by arrangement with John Wiley & Sons