NEEP602 Course Notes (Spring 1996)
Resources from Space
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Nature of the Exploration Problem
As a mineral deposit, the mare regolith has no counterpart in terrestrial mineral deposits, and any plan for exploring it must be adapted to its peculiar characteristics. The first of these is the structure of the regolith. The fundamental structural unit of regolith is the ejecta blanket, the material thrown out of a crater created by the impact of a body striking the surface of the Moon. In plan, each ejecta blanket was originally doughnut-shaped, the hole in the doughnut being occupied by the crater formed at the point of impact. In vertical section, each ejecta blanket had maximum thickness adjacent to the crater rim and was progressively thinner with distance from the rim. However, ejecta blankets range from very old to very young, and all older blankets have undoubtedly been disrupted, to varying degrees, by later impacts. Lateral continuity of blankets, except for the larger, youngest blankets, over substantial areas is hardly to be expected. Thus, although the regolith is layered, there will be only a very imperfect ``stratigraphy'' to use as a control on exploration.
The second characteristic that must be taken into account is the relation between contents of solar wind gases and length of exposure of the regolith to the solar wind as expressed in the ``maturity'' of the regolith. Exposure time may vary from layer to layer, hence surface scanning will not indicate gas contents in depth.
A final consideration in planning exploration is the possible scale of mining and processing operations. This will depend on what gases are sought. If only gases for life support and fuel are sought, the regolith mined annually is likely to be measured only in hundreds of thousands of tons per year. However, if mining for He-3 is undertaken, the scale of operations will be vastly enlarged. For example, if the scenario suggested by Sviatoslavsky and Jacobs (1988) is followed, mining would begin in 2015, and by 2050 production of He-3 would rise to 53.5 tonnes per year. The required rate of mining would then be about 7.6 billion tons of regolith per year, achieved by excavating regolith to a depth of 3 m over an area of about 1275 sq. km. Total area mined through 2050 would be about 14,000 sq. km. These figures are decidedly preliminary, but they indicate that establishing a reserve base for helium mining would require advance exploration on a scale not matched in any single mining enterprise on Earth.
Next: Site Selection Up: Plan of Exploration Previous: Plan of Exploration
WCSAR-TR-AR3-9301-1
Eugene N. Cameron
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