The Lunar Prospector gamma-ray and neutron spectrometers

Feldman, W. C.; Barraclough, B. L.; Fuller, K. R.; Lawrence, D. J.; Maurice, S.; Miller, M.C.; Prettyman, T. H.; Binder, A. B.

doi:10.1016/s0168-9002(98)00934-6

Cited by 114 publications

(94 citation statements)

References 2 publications

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“…The Moon, Mercury, Mars, and other satellites and asteroids without an atmosphere or with a thin atmosphere are directly exposed to GCR, and secondary neutrons are produced by nuclear interactions of GCR with surface materials (Feldman et al, 1999;Brückner and Masarik, 1997;Boynton et al, 2004). The surface of larger planets such as the Earth or Venus is shielded from the exposure of GCR by thick atmospheres.…”

Section: Neutron Productionmentioning

confidence: 99%

Complexities of gamma-ray line intensities from the lunar surface

et al. 2008

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Assuming different abundances of the Apollo lunar soil samples and the average spectrum of galactic cosmic ray protons, energy spectra of neutrons and gamma rays and emission rates of gamma-ray lines from major elements have been estimated by using the reviewed Monte Carlo simulation library Geant4 and nuclear data. Previously, such libraries were not able to reproduce gamma-ray lines properly for the planetary application. Results clearly show that the emission rate of gamma rays heavily depends not only on the chemical abundance but also neutron flux within the lunar subsurface. While the intensities of gamma-ray lines are mostly proportional to elemental abundances, the intensity per unit elemental abundance can vary. Such a complex correlation is attributed to the change in neutron flux within the lunar subsurface and petrological restriction of elemental variation.

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Section: Neutron Productionmentioning

confidence: 99%

Complexities of gamma-ray line intensities from the lunar surface

et al. 2008

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“…The LP GRS measures y-rays coming from the Moon having energies from 0.35 -9 MeV [Feldman et al, 1999]. While most lunar y-rays are produced from fast and thermal neutron reactions in the lunar regolith, the 2.6 MeV y-ray is produced at the end of the radioactive decay chain from 232Th [Lederer and Shirley, 1978].…”

Section: Deriving Absolute Thorium Abundancesmentioning

confidence: 99%

High resolution measurements of absolute thorium abundances on the lunar surface

Lawrence

Feldman

Barraclough

et al. 1999

Geophysical Research Letters

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Abstract. The Lunar Prospector (LP) Gamma-Ray Spectrometer (GRS) has been used to map the global abundance of thorium on the lunar surface. A global map of absolute thorium abundances on a 2 ø by 2 ø equal-area pixel scale is presented using new detector modeling results and low altitude LP data. Because thorium is relatively abundant in KREEP-rich material, these data provide fundamental information regarding the locations and importance of terranes that are rich in KREEP bearing materials.

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“…These facts simplify greatly a description of the mechanisms that shape neutron flux distributions at energies below -1 keV. This energy range is covered by the two 3He gas-proportional counters aboard Lunar Prospector (LP) [Feldman et al, 1999]. We will therefore concentrate on this range in the present study.…”

Section: Introductionmentioning

confidence: 99%

Chemical information content of lunar thermal and epithermal neutrons

Feldman¹,

Lawrence²,

Elphic³

et al. 2000

J. Geophys. Res.

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Abstract. Simulations of equilibrium thermal and epithermal neutron flux spectra for theMoon have been studied to determine their chemical information content. Most of this information resides in a single parameter, the ratio of macroscopic absorption to energyloss cross sections. Although this parameter cannot specify the chemistry of lunar soils uniquely, it provides an index that can be used to quantitatively separate anorthositic from mafic chemistries. Hydrogen abundances can best be derived from measurements of the epithermal neutron flux, which is strongly related to its macroscopic energy-loss cross section. The ratio of thermal to epithermal neutron flux measured by Lunar Prospector is shown to agree quantitatively with simulations. This agreement is used to show that the highlands terrane on the farside of the Moon is anorthositic, containing high percentages of plagioclase and possibly a range of Mg-suite minerals with a high Mg/(Mg + Fe) atomic ratio. Our best estimate of the abundance of FeO is 2%, with an upper limit of 5%.

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The Lunar Prospector gamma-ray and neutron spectrometers

Cited by 114 publications

References 2 publications

Complexities of gamma-ray line intensities from the lunar surface

Complexities of gamma-ray line intensities from the lunar surface

High resolution measurements of absolute thorium abundances on the lunar surface

Chemical information content of lunar thermal and epithermal neutrons

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