HR: 16:15h
AN: C12C-02 INVITED     [PDF]
TI: The Distribution of Near-Surface Ground Ice from Neutron and Gamma-Ray Spectroscopy on Mars, the Moon, and Mercury
AU: * Feldman, W C
EM: wfeldman@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D466, Los Alamos, NM 87545 United States
AB: Neutron and gamma-ray spectroscopy have been applied to the Moon and Mars in order to map the abundance of hydrogen within their uppermost meter of soil These investigations will be extended to Mercury using the neutron and gamma-ray spectrometers that are part of the payload of the Messenger mission. Significant enhancements in hydrogen were observed within the permanently shaded crater bottoms near both poles of the Moon using this technique and shown, through arguments of stability, to most likely be in the form of water ice [Feldman et al., J.G.R., 106, 23,231, 2001]. Simulations of the signature of hydrogen in neutrons for the measured topography at the lunar poles, yields an estimated H2O abundance of 1.5 percent by mass within the permanently-shaded areas. Radar backscatter observations from Mercury [Harmon et al., Nature, 369, 213, 1994] have discovered anomalous enhancements within permanently shaded craters near both poles of Mercury of same-sense polarization that are most readily interpreted as near-surface water ice. We will have to wait until about 2010 to verify this interpretation using neutron spectroscopy. After 1.5 years in orbit about Mars, three reservoirs of water-equivalent hydrogen have been delineated. Two of them at high northern and southern latitudes run upward of 20 percent H2O by mass, and the third at equatorial to mid latitudes extends between 2 percent and 13 percent by mass.
DE: 5462 Polar regions
DE: 6225 Mars
DE: 6235 Mercury
DE: 6250 Moon (1221)
SC: Cryosphere [C]
MN: 2003 Fall Meeting