Elemental mapping by Dawn reveals exogenic H in Vesta's regolith

Thomas H. Prettyman, David W. Mittlefehldt, Naoyuki Yamashita, David J. Lawrence, Andrew W. Beck, William C. Feldman, Timothy J. McCoy, Harry Y. McSween, Michael J. Toplis, Timothy N. Titus, Pasquale Tricarico, Robert C. Reedy, John S. Hendricks, Olivier Forni, Lucille Le Corre, Jian Yang Li, Hugau Mizzon, Vishnu Reddy, Carol A. Raymond, Christopher T. Russell

Research output: Contribution to journalArticlepeer-review

180 Scopus citations

Abstract

Using Dawn's Gamma Ray and Neutron Detector, we tested models of Vesta's evolution based on studies of howardite, eucrite, and diogenite (HED) meteorites. Global Fe/O and Fe/Si ratios are consistent with HED compositions. Neutron measurements confirm that a thick, diogenitic lower crust is exposed in the Rheasilvia basin, which is consistent with global magmatic differentiation. Vesta's regolith contains substantial amounts of hydrogen. The highest hydrogen concentrations coincide with older, low-albedo regions near the equator, where water ice is unstable. The young, Rheasilvia basin contains the lowest concentrations. These observations are consistent with gradual accumulation of hydrogen by infall of carbonaceous chondrites - observed as clasts in some howardites - and subsequent removal or burial of this material by large impacts.

Original languageEnglish (US)
Pages (from-to)242-246
Number of pages5
JournalScience
Volume338
Issue number6104
DOIs
StatePublished - Oct 12 2012
Externally publishedYes

ASJC Scopus subject areas

  • General

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