title: Stable isotope measurements of martian atmospheric CO2 at the Phoenix landing site.
abstract: Carbon dioxide is a primary component of the martian atmosphere and reacts readily with water and silicate rocks. Thus, the stable isotopic composition of CO2 can reveal much about the history of volatiles on the planet. The Mars Phoenix spacecraft measurements of carbon isotopes [referenced to the Vienna Pee Dee belemnite (VPDB)] [delta13C(VPDB) = -2.5 +/- 4.3 per mil (per thousand)] and oxygen isotopes [referenced to the Vienna standard mean ocean water (VSMOW)] (delta18O(VSMOW) = 31.0 +/- 5.7 per thousand), reported here, indicate that CO2 is heavily influenced by modern volcanic degassing and equilibration with liquid water. When combined with data from the martian meteorites, a general model can be constructed that constrains the history of water, volcanism, atmospheric evolution, and weathering on Mars. This suggests that low-temperature water-rock interaction has been dominant throughout martian history, carbonate formation is active and ongoing, and recent volcanic degassing has played a substantial role in the composition of the modern atmosphere.
authors.affiliation: Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, TX 77058, USA. paul.b.niles@nasa.gov
authors.forename: Paul B
authors.initials: PB
authors.lastname: Niles
authors.forename: William V
authors.initials: WV
authors.lastname: Boynton
authors.forename: John H
authors.initials: JH
authors.lastname: Hoffman
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Ming
authors.forename: Dave
authors.initials: D
authors.lastname: Hamara
mesh_terms: D001272:Atmosphere; D002245:Carbon Dioxide / Q000032:analysis*; D002247:Carbon Isotopes / Q000032:analysis; D002254:Carbonates; D019419:Evolution, Planetary; D005118:Extraterrestrial Environment; D018535:Mars; D019110:Meteoroids; D010103:Oxygen Isotopes / Q000032:analysis; D018531:Spacecraft; D013696:Temperature; D013995:Time; D018707:Volcanic Eruptions; D014867:Water
chemical_list: D002247:Carbon Isotopes; D002254:Carbonates; D010103:Oxygen Isotopes; D014867:Water; D002245:Carbon Dioxide