title: Deuterium on Venus:  observations from Earth.
abstract: Absorption lines of HDO and H2O have been detected in a 0.23-wave number resolution spectrum of the dark side of Venus in the interval 2.34 to 2.43 micrometers, where the atmosphere is sounded in the altitude range from 32 to 42 kilometers (8 to 3 bars).  The resulting value of the deuterium-to-hydrogen ratio (D/H) is 120 +/- 40 times the telluric ratio, providing unequivocal confirmation of in situ Pioneer Venus mass spectrometer measurements that were in apparent conflict with an upper limit set from International Ultraviolet Explorer spectra.  The 100-fold enrichment of the D/H ratio on Venus compared to Earth is thus a fundamental constraint on models for its atmospheric evolution.
authors.affiliation: Département de Recherche Spatiale, Observatoire de Paris, Meudon, France.
authors.forename: C
authors.initials: C
authors.lastname: de Bergh
authors.forename: B
authors.initials: B
authors.lastname: Bézard
authors.forename: T
authors.initials: T
authors.lastname: Owen
authors.forename: D
authors.initials: D
authors.lastname: Crisp
authors.lastname: Maillard J-P
authors.forename: B L
authors.initials: BL
authors.lastname: Lutz
mesh_terms: D001272:Atmosphere; D002245:Carbon Dioxide / Q000032:analysis; D003903:Deuterium / Q000032:analysis* / Q000737:chemistry*; D005118:Extraterrestrial Environment; D006859:Hydrogen / Q000032:analysis / Q000737:chemistry; D008962:Models, Theoretical; D013056:Spectrophotometry, Ultraviolet; D018536:Venus; D014867:Water / Q000032:analysis / Q000737:chemistry
chemical_list: D014867:Water; D002245:Carbon Dioxide; D006859:Hydrogen; D003903:Deuterium