title: Distribution of hydrogen in the near surface of Mars: evidence for subsurface ice deposits.
abstract: Using the Gamma-Ray Spectrometer on the Mars Odyssey, we have identified two regions near the poles that are enriched in hydrogen. The data indicate the presence of a subsurface layer enriched in hydrogen overlain by a hydrogen-poor layer. The thickness of the upper layer decreases with decreasing distance to the pole, ranging from a column density of about 150 grams per square centimeter at -42 degrees latitude to about 40 grams per square centimeter at -77 degrees. The hydrogen-rich regions correlate with regions of predicted ice stability. We suggest that the host of the hydrogen in the subsurface layer is ice, which constitutes 35 +/- 15% of the layer by weight.
authors.affiliation: Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA. wboynton@lpl.arizona.edu
authors.forename: W V
authors.initials: WV
authors.lastname: Boynton
authors.forename: W C
authors.initials: WC
authors.lastname: Feldman
authors.forename: S W
authors.initials: SW
authors.lastname: Squyres
authors.forename: T H
authors.initials: TH
authors.lastname: Prettyman
authors.forename: J
authors.initials: J
authors.lastname: Bruckner
authors.forename: L G
authors.initials: LG
authors.lastname: Evans
authors.forename: R C
authors.initials: RC
authors.lastname: Reedy
authors.forename: R
authors.initials: R
authors.lastname: Starr
authors.forename: J R
authors.initials: JR
authors.lastname: Arnold
authors.forename: D M
authors.initials: DM
authors.lastname: Drake
authors.forename: P A J
authors.initials: PA
authors.lastname: Englert
authors.forename: A E
authors.initials: AE
authors.lastname: Metzger
authors.forename: Igor
authors.initials: I
authors.lastname: Mitrofanov
authors.forename: J I
authors.initials: JI
authors.lastname: Trombka
authors.forename: C
authors.initials: C
authors.lastname: D'Uston
authors.forename: H
authors.initials: H
authors.lastname: Wanke
authors.forename: O
authors.initials: O
authors.lastname: Gasnault
authors.forename: D K
authors.initials: DK
authors.lastname: Hamara
authors.forename: D M
authors.initials: DM
authors.lastname: Janes
authors.forename: R L
authors.initials: RL
authors.lastname: Marcialis
authors.forename: S
authors.initials: S
authors.lastname: Maurice
authors.forename: I
authors.initials: I
authors.lastname: Mikheeva
authors.forename: G J
authors.initials: GJ
authors.lastname: Taylor
authors.forename: R
authors.initials: R
authors.lastname: Tokar
authors.forename: C
authors.initials: C
authors.lastname: Shinohara
mesh_terms: D001272:Atmosphere; D004367:Dry Ice; D005118:Extraterrestrial Environment; D005720:Gamma Rays; D006859:Hydrogen; D007053:Ice; D018535:Mars; D008962:Models, Theoretical; D009502:Neutrons; D018531:Spacecraft; D013051:Spectrometry, Gamma; D013057:Spectrum Analysis; D014867:Water
chemical_list: D004367:Dry Ice; D007053:Ice; D014867:Water; D006859:Hydrogen