title: Atmosphere-surface interactions on Mars: delta 17O measurements of carbonate from ALH 84001.
abstract: Oxygen isotope measurements of carbonate from martian meteorite ALH 84001 (delta18O = 18.3 +/- 0.4 per mil, delta17O = 10.3 +/- 0.2 per mil, and Delta17O = 0.8 +/- 0.05 per mil) are fractionated with respect to those of silicate minerals. These measurements support the existence of two oxygen isotope reservoirs (the atmosphere and the silicate planet) on Mars at the time of carbonate growth. The cause of the atmospheric oxygen isotope anomaly may be exchange between CO2 and O(1D) produced by the photodecomposition of ozone. Atmospheric oxygen isotope compositions may be transferred to carbonate minerals by CO2-H2O exchange and mineral growth. A sink of 17O-depleted oxygen, as required by mass balance, may exist in the planetary regolith.
authors.affiliation: Department of Chemistry, University of California San Diego, 92093-0356, USA. jfarquha@ucsd.edu
authors.forename: J
authors.initials: J
authors.lastname: Farquhar
authors.forename: M H
authors.initials: MH
authors.lastname: Thiemens
authors.forename: T
authors.initials: T
authors.lastname: Jackson
mesh_terms: D001272:Atmosphere; D002245:Carbon Dioxide / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry*; D003903:Deuterium / Q000737:chemistry; D005118:Extraterrestrial Environment; D006358:Hot Temperature; D006859:Hydrogen / Q000737:chemistry; D018535:Mars; D019110:Meteoroids; D010084:Oxidation-Reduction; D010103:Oxygen Isotopes; D010126:Ozone / Q000737:chemistry; D010782:Photolysis; D014867:Water / Q000737:chemistry
chemical_list: D002254:Carbonates; D010103:Oxygen Isotopes; D014867:Water; D002245:Carbon Dioxide; D010126:Ozone; D006859:Hydrogen; D003903:Deuterium