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AGU: Journal of Geophysical Research, Planets

 

Index Terms

  • Planetology: Solar System Objects: Moon
  • Planetology: Solid Surface Planets: Impact phenomena (includes cratering)
  • Planetology: Solid Surface Planets: Remote sensing
  • Planetology: Solid Surface Planets: Surface materials and properties
Abstract
Cited By (4)
 

Abstract

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

Jeffrey R. Johnson

United States Geological Survey, Flagstaff, Arizona, USA

William C. Feldman

Los Alamos National Laboratory, Los Alamos, New Mexico, USA

David J. Lawrence

Los Alamos National Laboratory, Los Alamos, New Mexico, USA

Sylvestre Maurice

Observatoire Midi-Pyrénées, Toulouse, France

Timothy D. Swindle

Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA

Paul G. Lucey

Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, Honolulu, Hawaii, USA

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.

Published 28 February 2002.

Citation: Johnson, J. R., W. C. Feldman, D. J. Lawrence, S. Maurice, T. D. Swindle, and P. G. Lucey (2002), Lunar Prospector epithermal neutrons from impact craters and landing sites: Implications for surface maturity and hydrogen distribution, J. Geophys. Res., 107(E2), 5008, doi:10.1029/2000JE001430.

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