title: Constraints on Vesta's elemental composition: Fast neutron measurements by Dawn's gamma ray and neutron detector.
abstract: Surface composition information from Vesta is reported using fast neutron data collected by the gamma ray and neutron detector on the Dawn spacecraft. After correcting for variations due to hydrogen, fast neutrons show a compositional dynamic range and spatial variability that is consistent with variations in average atomic mass from howardite, eucrite, and diogenite (HED) meteorites. These data provide additional compositional evidence that Vesta is the parent body to HED meteorites. A subset of fast neutron data having lower statistical precision show spatial variations that are consistent with a 400 ppm variability in hydrogen concentrations across Vesta and supports the idea that Vesta's hydrogen is due to long-term delivery of carbonaceous chondrite material.
authors.affiliation: The Johns Hopkins University Applied Physics Laboratory Laurel, Maryland, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Lawrence
authors.affiliation: The Johns Hopkins University Applied Physics Laboratory Laurel, Maryland, USA.
authors.forename: Patrick N
authors.initials: PN
authors.lastname: Peplowski
authors.affiliation: Planetary Science Institute Tucson, Arizona, USA.
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Prettyman
authors.affiliation: Planetary Science Institute Tucson, Arizona, USA.
authors.forename: William C
authors.initials: WC
authors.lastname: Feldman
authors.affiliation: The Johns Hopkins University Applied Physics Laboratory Laurel, Maryland, USA.
authors.forename: David
authors.initials: D
authors.lastname: Bazell
authors.affiliation: NASA Johnson Space Center Houston, Texas, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Mittlefehldt
authors.affiliation: Planetary Science Institute Tucson, Arizona, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Reedy
authors.affiliation: Planetary Science Institute Tucson, Arizona, USA.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Yamashita