In situ measurement of atmospheric krypton and xenon on Mars with Mars Science Laboratory

• Published in: Earth and planetary science letters Vol. 454; no. C; pp. 1 - 9
• Main Authors: Conrad, P.G., Malespin, C.A., Franz, H.B., Pepin, R.O., Trainer, M.G., Schwenzer, S.P., Atreya, S.K., Freissinet, C., Jones, J.H., Manning, H., Owen, T., Pavlov, A.A., Wiens, R.C., Wong, M.H., Mahaffy, P.R.
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center Elsevier B.V 15-11-2016; Elsevier
• Subjects: ASTRONOMY AND ASTROPHYSICS; Atmospherics; GEOSCIENCES; Inorganic, Organic And Physical Chemistry; Krypton; Lunar And Planetary Science And Exploration; Mars (planet); Mars atmosphere; Mars craters; Mars evolution; Mars meteorites; Mars Science Laboratory; Martian meteorites; SNC meteorites; Solar Physics; Spallation; Statistics And Probability; Xenon; Mars Science Laboratory; Mars evolution; Mars meteorites; xenon; Mars atmosphere; krypton
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2016.08.028

Mars Science Laboratory's Sample Analysis at Mars (SAM) investigation has measured all of the stable isotopes of the heavy noble gases krypton and xenon in the martian atmosphere, in situ, from the Curiosity Rover at Gale Crater, Mars. Previous knowledge of martian atmospheric krypton and xenon isotope ratios has been based upon a combination of the Viking mission's krypton and xenon detections and measurements of noble gas isotope ratios in martian meteorites. However, the meteorite measurements reveal an impure mixture of atmospheric, mantle, and spallation contributions. The xenon and krypton isotopic measurements reported here include the complete set of stable isotopes, unmeasured by Viking. The new results generally agree with Mars meteorite measurements but also provide a unique opportunity to identify various non-atmospheric heavy noble gas components in the meteorites. Kr isotopic measurements define a solar-like atmospheric composition, but deviating from the solar wind pattern at 80Kr and 82Kr in a manner consistent with contributions originating from neutron capture in Br. The Xe measurements suggest an intriguing possibility that isotopes lighter than 132Xe have been enriched to varying degrees by spallation and neutron capture products degassed to the atmosphere from the regolith, and a model is constructed to explore this possibility. Such a spallation component, however, is not apparent in atmospheric Xe trapped in the glassy phases of martian meteorites.
•In situ measurement of all stable isotopes of Kr and Xe in the atmosphere of Mars.•A new benchmark for untangling the sources of Kr and Xe in SNC meteorites.•Light isotope enrichments indicate neutron-capture contributions to atmospheric Kr.•Xe isotopic elevations suggest presence of spallation and neutron-capture products.