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Title: DISTRIBUTION OF IRON AND TITANIUM ON THE LUNAR SURFACE FROM LUNAR PROSPECTOR GAMMA RAY SPECTRA

Abstract

No abstract prepared.

Authors:
Publication Date:
Research Org.:
Los Alamos National Lab., Los Alamos, NM (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
774348
Report Number(s):
LA-UR-01-536
TRN: US200201%%92
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Conference title not supplied, Conference location not supplied, Conference dates not supplied; Other Information: PBD: 1 Jan 2001
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DISTRIBUTION; IRON; SPECTRA; TITANIUM; MOON; SURFACES; LUNAR MATERIALS

Citation Formats

T. PRETTYMAN. DISTRIBUTION OF IRON AND TITANIUM ON THE LUNAR SURFACE FROM LUNAR PROSPECTOR GAMMA RAY SPECTRA. United States: N. p., 2001. Web.
T. PRETTYMAN. DISTRIBUTION OF IRON AND TITANIUM ON THE LUNAR SURFACE FROM LUNAR PROSPECTOR GAMMA RAY SPECTRA. United States.
T. PRETTYMAN. Mon . "DISTRIBUTION OF IRON AND TITANIUM ON THE LUNAR SURFACE FROM LUNAR PROSPECTOR GAMMA RAY SPECTRA". United States. doi:. https://www.osti.gov/servlets/purl/774348.
@article{osti_774348,
title = {DISTRIBUTION OF IRON AND TITANIUM ON THE LUNAR SURFACE FROM LUNAR PROSPECTOR GAMMA RAY SPECTRA},
author = {T. PRETTYMAN},
abstractNote = {No abstract prepared.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2001},
month = {Mon Jan 01 00:00:00 EST 2001}
}

Conference:
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  • Gamma ray pulse height spectra acquired by the Lunar Prospector (LP) Gamma-Ray Spectrometer (GRS) contain information on the abundance of major elements in the lunar surface, including O, Si, Ti, Al, Fe, Mg, Ca, K, and Th. With the exception of Th and K, prompt gamma rays produced by cosmic ray interactions with surface materials are used to determine elemental abundance. Most of these gamma rays are produced by inelastic scattering of fast neutrons and by neutron capture. The production of neutron-induced gamma rays reaches a maximum deep below the surface (e.g. {approx}140 g/cm{sup 2} for inelastic scattering and {approx}50more » g/cm{sup 2} for capture). Consequently, gamma rays sense the bulk composition of lunar materials, in contrast to optical methods [e.g. Clementine Spectral Reflectance (CSR)], which only sample the top few microns. Because most of the gamma rays are produced deep beneath the surface, few escape unscattered and the continuum of scattered gamma rays dominates the spectrum. In addition, due to the resolution of the spectrometer, there are few well-isolated peaks and peak fitting algorithms must be used to deconvolve the spectrum in order to determine the contribution of individual elements.« less
  • One of the instruments on board the recently launched Lunar Prospector spacecraft is a Gamma-Ray Spectrometer (GRS) designed to map the surface elemental composition of the Moon. Specifically, the objectives of the GRS are to map abundances of Fe, Ti, U, Th, K, Si, O and if possible Mg, Al, and Ca. The GRS consists of a bismuth germanate (BGO) crystal placed within a well shaped borated plastic scintillator anti-coincidence (ACS) shield. Events triggering only the BGO are labeled as accepted events; events triggering both the BGO and ACS are labeled as rejected events. BGO spectra for both accepted andmore » rejected events are telemetered to the ground for later analysis. Results of the study are given.« less
  • South Pole-Aitken (SPA) basin has been a target of intense study since it is one of the largest impact basins in the solar system. It is thought that SPA basin excavated deep into the lunar crust and possibly even the mantle. Such conclusions have been supported by the observed mafic and thorium composition anomalies seen across the entire basin. One of the major goals of lunar and planetary science has been to measure and understand the composition of the non-mare materials within SPA basin. It is expected that this information will help to increase our understanding of the formation andmore » differentiation processes that occurred early on the Moon.« less
  • Lunar Prospector neutron spectrometer (NS) and gamma ray spectrometer (GRS) observations have been used to map out the distribution of incompatible elements on the lunar surface. Specifically, the GRS data provide maps of the distribution of thorium and potassium while the NS data provide information on the distribution of iron and titanium, and the rare earth elements gadolinium and samarium. Using results of analysis of Celementine spectral reflectance (CSR) data, the Fe- and Ti-contributions to the NS data can be removed, leaving primarily rare earth element contributions from Gd and Sm. The Th and K maps correlate with the inferredmore » Gd and Sm maps (r {approximately} 0.93), but there are regions of significant disagreement. One of these is in the KREEP-rich circum-Imbrium ring. No clear explanation has emerged for this disagreement, though Th, K, Gd and Sm have differing degrees of incompatibility. These results clearly are important to discussions of the geochemistry of the Procellarum-Imbrium Th-rich Terrane and the South-Pole-Aitken Terrane.« less
  • The gamma rays emitted from the moon or any similar body carry information on the chemical composition of the surface layer. The elements most easily measured are K, U, Th, and major elements such as O, Si, Mg, and Fe. The expected fluxes of gamma ray lines are calculated for Four lunar compositions and one chondritic chemistry from a consideration of thc important emission mechanisms: natural radioactivity, inelastic scatter, neutron capture, and induced radioactivity. The models used for cosmic ray interactions are those of Reedy and Arnold (1972) and Lingenfelter et al. (1972). The areal resolution of the experiment ismore » calculated to be around 70-140 km under the conditions of the Apollo 15 and 16 experiments. Finally, a method is described for recovering the chemical information from the observed scintillation spectra obtained in these experiments. (auth)« less