title: Photo-induced fractionation of water isotopomers in the Martian atmosphere.
abstract: The history and size of the water reservoirs on early Mars can be constrained using isotopic ratios of deuterium to hydrogen. We present new laboratory measurements of the ultraviolet cross-sections of H2O and its isotopomers, and modeling calculations in support of a photo-induced fractionation effect (PHIFE), that reconciles a discrepancy between past theoretical modeling and recent observations. This supports the hypothesis that Mars had an early warm atmosphere and has lost at least a 50-m global layer of water. Likely applications of PHIFE to other planetary atmospheres are sketched.
authors.affiliation: Synchrotron Radiation Research Center, Hsinchu, Taiwan.
authors.forename: B M
authors.initials: BM
authors.lastname: Cheng
authors.forename: E P
authors.initials: EP
authors.lastname: Chew
authors.forename: C P
authors.initials: CP
authors.lastname: Liu
authors.forename: M
authors.initials: M
authors.lastname: Bahou
authors.forename: Y P
authors.initials: YP
authors.lastname: Lee
authors.forename: Y L
authors.initials: YL
authors.lastname: Yung
authors.forename: M F
authors.initials: MF
authors.lastname: Gerstell
mesh_terms: D001272:Atmosphere / Q000737:chemistry*; D005591:Chemical Fractionation; D003903:Deuterium / Q000737:chemistry* / Q000528:radiation effects; D019419:Evolution, Planetary; D018559:Exobiology; D005118:Extraterrestrial Environment; D006859:Hydrogen / Q000737:chemistry* / Q000528:radiation effects; D008027:Light; D018535:Mars; D008956:Models, Chemical; D010782:Photolysis; D017356:Synchrotrons; D014867:Water / Q000032:analysis / Q000737:chemistry*
chemical_list: D014867:Water; D006859:Hydrogen; D003903:Deuterium