Lunar prospector epithermal neutrons from impact craters and landing sites: Implications for surface maturity and hydrogen distribution

Jeffrey R. Johnson, William C. Feldman, David J. Lawrence, Sylvestre Maurice, Timothy D. Swindle, Paul G. Lucey

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Initial studies of neutron spectrometer data returned by Lunar Prospector concentrated on the discovery of enhanced hydrogen abundances near both lunar poles. However, the nonpolar data exhibit intriguing patterns that appear spatially correlated with surface features such as young impact craters (e.g., Tycho). Such immature crater materials may have low hydrogen contents because of their relative lack of exposure to solar wind-implanted volatiles. We tested this hypothesis by comparing epithermal* neutron counts (i.e., epithermal -0.057 × thermal neutrons) for Copernican-age craters classified as relatively young, intermediate, and old (as determined by previous studies of Clementine optical maturity variations). The epithermal* counts of the crater and continuous ejecta regions suggest that the youngest impact materials are relatively devoid of hydrogen in the upper 1 m of regolith. We also show that the mean hydrogen contents measured in Apollo and Luna landing site samples are only moderately well correlated to the epithermal* neutron counts at the landing sites, likely owing to the effects of rare earth elements. These results suggest that further work is required to define better how hydrogen distribution can be revealed by epithermal neutrons in order to understand more fully the nature and sources (e.g., solar wind, meteorite impacts) of volatiles in the lunar regolith.

Original languageEnglish (US)
Pages (from-to)3-1-3-8
JournalJournal of Geophysical Research E: Planets
Volume107
Issue number2
DOIs
StatePublished - Jan 1 2002

Keywords

  • Apollo
  • Epithermal
  • Hydrogen
  • Impact craters
  • Landing sites
  • Lunar Prospector
  • Neutrons

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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