December 1, 1998
Drs. Jeffrey R. Johnson of the U.S. Geological Survey in Flagstaff, Arizona; Timothy S. Swindle of the University of Arizona's Lunar and Planetary Laboratory in Tucson; and Paul G. Lucey of the University of Hawaii's Institute of Geophysics and Planetology in Honolulu have developed a helium-3 map of the Moon based on a combination of factors they have analyzed. Their research will be published in a forthcoming issue of Geophysical Research Letters, a publication of the American Geophysical Union, as "Estimated Solar Wind-Implanted Helium-3 Distribution On The Moon."
The factors taken into account by the researchers in mapping the likely abundance of helium-3 in a given area are the exposure age of the Moon's surface matter, or regolith; the relative amount of charged particles, including helium-3, arriving from the Sun (the solar wind); and the titanium content of the lunar soil. The mineral ilmenite [FeTiO3], composed of iron, titanium, and oxygen, retains helium much better than other major lunar materials. The older soils should be better sources of helium-3, they report, because they have been exposed to the solar wind longer and contain greater amounts of fine-grained aggregates that absorb helium-3. Also, solar wind-implanted particles are more abundant on the far side, because the Earth shields the Moon's near side from the solar wind for a portion of each solar orbit.
The scientists estimate that the greatest amounts of helium- 3 will be found on the far side maria, or "seas," of the Moon, due to the higher solar wind, and in nearside areas with high concentrations of titanium dioxide [TiO2]. Their hypothesis is based on analysis of rock samples brought back by Apollo astronauts and mineralogic maps produced by the Clementine spacecraft. They expect to refine their maps with new elemental composition maps produced by the Lunar Prospector spacecraft.
Notes:
"3He" is written with the numeral "3" as a superscript. The numerals in "FeTiO3" and "TiO2" are subscripts.
A color figure accompanies this paper. Click on Document 'cover3.tif'
Photocaption:
"Simple cylindrical projections (left side of images corresponds to 180
West longitude; 30 degree grid shown) of (a) solar wind fluence
model; (b) Clementine 750 mm mosaic; (c ) TiO2 abundance map
from Lucey et. al. (1996) displayed from 0-7 weight percent; and
(d) 3He abundance map displayed from 1-10 ppb (see text for
details)."
National Space Society
Lecture series:
Tuesday, August 11th 1998
Some fusion propulsion concepts for space travel have matured to a level where we can estimate the fuel and propellant needs for various space mission scenarios. A solar system colonization/outpost strategy is assumed to take place in the 2nd and 3rd quarters of the 21st Century. NASA, and others, have identified the moon as a candidate source for large quantities of helium-3, which is needed for fusion-electric power. The energy content of helium-3 is so high that one space shuttle returning to Earth with 20 tons of helium-3 represents $320 billion (1991 $) to an Earth-based energy market. 20-tones per year (under the assumed colonization strategy) is the approximate amount of helium-3 required to support growth of one colony on Mars and outposts at each of the gas-giant planets. Estimated propellant requirements for the solar system colonization strategy are extremely huge amounts, and means to minimize these resource requirements will be discussed. On the positive side, it is determined that nuclear fusion can provide a robust transportation infrastructure to sustain a major solar system colonization effort in the 2nd and 3rd quarters of the 21st Century.
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