title: Primordial argon isotope fractionation in the atmosphere of Mars measured by the SAM instrument onCuriosityand implications for atmospheric loss.
abstract: [1] The quadrupole mass spectrometer of the Sample Analysis at Mars (SAM) instrument onCuriosityrover has made the first high-precision measurement of the nonradiogenic argon isotope ratio in the atmosphere of Mars. The resulting value of36Ar/38Ar = 4.2 ± 0.1 is highly significant for it provides excellent evidence that "Mars" meteorites are indeed of Martian origin, and it points to a significant loss of argon of at least 50% and perhaps as high as 85-95% from the atmosphere of Mars in the past 4 billion years. Taken together with the isotopic fractionations in N, C, H, and O measured by SAM, these results imply a substantial loss of atmosphere from Mars in the posthydrodynamic escape phase.
authors.affiliation: Department of Atmospheric, Oceanic and Space Sciences, University of Michigan Ann Arbor, Michigan, USA.
authors.forename: Sushil K
authors.initials: SK
authors.lastname: Atreya
authors.affiliation: Goddard Space Flight Center Greenbelt, Maryland, USA.
authors.forename: Melissa G
authors.initials: MG
authors.lastname: Trainer
authors.affiliation: Goddard Space Flight Center Greenbelt, Maryland, USA.
authors.forename: Heather B
authors.initials: HB
authors.lastname: Franz
authors.affiliation: Department of Atmospheric, Oceanic and Space Sciences, University of Michigan Ann Arbor, Michigan, USA.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Wong
authors.affiliation: Concordia College Moorhead, Minnesota, USA.
authors.forename: Heidi L K
authors.initials: HL
authors.lastname: Manning
authors.affiliation: Goddard Space Flight Center Greenbelt, Maryland, USA.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Malespin
authors.affiliation: Goddard Space Flight Center Greenbelt, Maryland, USA.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Mahaffy
authors.affiliation: Goddard Space Flight Center Greenbelt, Maryland, USA.
authors.forename: Pamela G
authors.initials: PG
authors.lastname: Conrad
authors.affiliation: Goddard Space Flight Center Greenbelt, Maryland, USA.
authors.forename: Anna E
authors.initials: AE
authors.lastname: Brunner
authors.affiliation: School of Science, Rensselaer Polytechnic Institute Troy, New York, USA.
authors.forename: Laurie A
authors.initials: LA
authors.lastname: Leshin
authors.affiliation: NASA Johnson Space Center Houston, Texas, USA.
authors.forename: John H
authors.initials: JH
authors.lastname: Jones
authors.affiliation: Jet Propulsion Laboratory, California Institute of Technology Pasadena, California, USA.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Webster
authors.affiliation: University of Hawai'i at Mānoa Honolulu, Hawaii, USA.
authors.forename: Tobias C
authors.initials: TC
authors.lastname: Owen
authors.affiliation: University of Minnesota Minneapolis, Minnesota, USA.
authors.forename: Robert O
authors.initials: RO
authors.lastname: Pepin
authors.affiliation: Universidad Nacional Autónoma de México México, Mexico.
authors.forename: R
authors.initials: R
authors.lastname: Navarro-González
keywords: Mars; argon isotopes; atmospheric loss; habitability; planetary atmospheres; solar system
references.citation: Science. 1976 Aug 27;193(4255):801-3
references.pmid: 17747783
references.citation: Science. 1976 Oct 1;194(4260):76-8
references.pmid: 17793083
references.citation: Science. 2013 Jul 19;341(6143):263-6
references.pmid: 23869014
references.citation: Science. 2013 Sep 27;341(6153):1238937
references.pmid: 24072926