Richard C. Elphic

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Maps of epithermal- and fast-neutron fluxes measured by Lunar Prospector were used to search for deposits enriched in hydrogen at both lunar poles. Depressions in epithermal fluxes were observed close to permanently shaded areas at both poles. The peak depression at the North Pole is 4.6 percent below the average epithermal flux intensity at lower(More)
Lunar Prospector gamma-ray spectrometer spectra along with counting rate maps of thorium, potassium, and iron delineate large compositional variations over the lunar surface. Thorium and potassium are highly concentrated in and around the nearside western maria and less so in the South Pole-Aitken basin. Counting rate maps of iron gamma-rays show a surface(More)
Global distributions of thermal, epithermal, and fast neutron fluxes have been mapped during late southern summer/northern winter using the Mars Odyssey Neutron Spectrometer. These fluxes are selectively sensitive to the vertical and lateral spatial distributions of H and CO2 in the uppermost meter of the martian surface. Poleward of +/-60 degrees latitude(More)
[1] Neutron data observed using the Neutron Spectrometer aboard 2001 Mars Odyssey provide a lower limit to the global inventory of Martian water-equivalent hydrogen. Hydrogen-rich deposits ranging between about 20% and 100% water-equivalent by mass are found poleward of ±50 latitude, and less rich, but significant, deposits are found at near-equatorial(More)
Measurements of absolute thorium abundances on the lunar surface are presented using both the highand low-altitude data taken with the Lunar Prospector Gamma-Ray Spectrometer. An analysis of the uncertainties shows that the measured uncertainties are < 0.5 μg/g and are close to the theoretical limit of Poisson statistics. Currently, the overall systematic(More)
Introduction: In recent years, a number of studies [1,2,3] have been published using data from the Lunar Prospector Neutron Spectrometer (LP-NS) to identify and quantify anomalously high hydrogen abundances near the poles of the Moon, which may be in the form of water ice. If water ice is indeed present at the lunar poles in high enough abundance, this(More)
The ability to locate and characterize icy deposits and other hydrogenous materials on the Moon and Mars will help us understand the distribution of water and, therefore, possible habitats at Mars, and may help us locate primitive prebiotic compounds at the Moon's poles. We have developed a rover-borne neutron probe that localizes a near-surface icy deposit(More)
Diviner Lunar Radiometer Experiment surface-temperature maps reveal the existence of widespread surface and near-surface cryogenic regions that extend beyond the boundaries of persistent shadow. The Lunar Crater Observation and Sensing Satellite (LCROSS) struck one of the coldest of these regions, where subsurface temperatures are estimated to be 38 kelvin.(More)
In Earth's environment, the observed polar outflow rate for O(+) ions, the main source of oxygen above gravitational escape energy, corresponds to the loss of approximately 18% of the present-day atmospheric oxygen over 3 billion years. However, part of this apparent loss can actually be returned to the atmosphere. Examining loss rates of four escape routes(More)
Introduction: We now have information from the fully reduced Lunar Prospector Neutron Spectrometers. Interpretation of these data yields distributions of rare earth elements (REE) Sm and Gd [1], major oxides and hydrogen on the Moon. Once both contributions of REE and major oxides are accounted for, we can construct the first global map of hydrogen(More)