title: HDO in the Martian atmosphere:  implications for the abundance of crustal water.
abstract: The physical and chemical processes that lead to the preferential escape of hydrogen over deuterium in the Martian atmosphere are studied in detail using a one-dimensional photochemical model.  Comparison of our theory with recent observations of HDO suggests that, averaged over the planet, Mars contains 0.2 m of crustal water that is exchangeable with the atmosphere.  Our estimate is considerably lower than recent estimates of subsurface water on Mars based on geomorphological analysis of Viking images.  The estimate can be reconciled if only a small fraction of crustal water can exchange with the atmosphere.
authors.affiliation: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena 91125, USA.
authors.forename: Y L
authors.initials: YL
authors.lastname: Yung
authors.forename: J S
authors.initials: JS
authors.lastname: Wen
authors.forename: J P
authors.initials: JP
authors.lastname: Pinto
authors.forename: M
authors.initials: M
authors.lastname: Allen
authors.forename: K K
authors.initials: KK
authors.lastname: Pierce
authors.forename: S
authors.initials: S
authors.lastname: Paulson
mesh_terms: D001272:Atmosphere; D003903:Deuterium / Q000032:analysis*; D005118:Extraterrestrial Environment; D055593:Geological Phenomena; D005844:Geology; D006859:Hydrogen / Q000032:analysis*; D018535:Mars; D008956:Models, Chemical; D010777:Photochemistry; D018531:Spacecraft; D014867:Water / Q000032:analysis / Q000737:chemistry*
chemical_list: D014867:Water; D006859:Hydrogen; D003903:Deuterium