NEEP602 Course Notes (Spring 1996)
Resources from Space
Next: Stage 2 - Up: Plan of Exploration Previous: Site Selection
Delineation of Areas of Minable Regolith
The first step in exploration should be high-resolution photography of the target area, from a lunar orbiter. Study of high-resolution photographs of the Apollo 11 and Ranger VIII areas indicates that by far the most abundant and widely distributed obstacles to mining are craters and their ejecta halos, but that from place to place on the mare there is much variation in their number, distribution, distinctness, diameter, and depth. Figure 1 is a reduced photograph of a part of Mare Tranquillitatis that is typical of much of the area east and northeast of the Apollo 11 landing site. The largest crater is about 490 m in diameter. At least 50% of this area will be minable (see Cameron, 1992). In marked contrast is Fig. 2, which shows part of the heavily cratered belt that crosses the Ranger VIII landing area. Besides the largest craters completely shown, 600-1,000 m in diameter, there are numerous craters 100 to more than 300 m in diameter. Much of this area will be unminable by large excavating machines.
Figure 2: Lunar orbiter print II-71-H
,
reduced from original size of 39 x 53 cm.
Despite the wide range in crater characteristics, such photographs can be used to classify various portions of the target areas roughly into the following types:
- (1) Areas occupied by young craters large enough (hence deep
enough)
to have penetrated bedrock. Halos of ejecta containing blocks of rock 2 m or
more in diameter accompany many of the larger craters of this group. These
areas presumably will be unminable, at least in large part.
- (2) Areas occupied by very old craters large enough to have
penetrated bedrock but now in advanced stages of obliteration by slumping and
later impacts. These areas will have undulating topography that should present
no obstacles to mining and should be covered by regolith in excess of 3 m in
depth. No ejecta blocks with diameters in excess of 2 m in diameter (2 m is
the limit of resolution of the photographs) are visible in or around them.
- (3) Areas with craters of intermediate age that are large enough
(18 m or more in diameter) to have penetrated bedrock but show no ejecta
blocks. These craters are deeper (for a given diameter) and more distinct than
craters in areas of type 2, but less so than craters in areas of type 1.
However, they contain no ejecta blocks and have no ejecta blocks 2 m or more
in diameter around their rims. The larger, deeper ones
will probably prove to be unminable, but areas having only smaller craters may
prove minable.
The 2 m resolution limit of the photographs of the Apollo 11 and Ranger VIII areas sets a limit on their usefulness in delineating minable areas. Higher-resolution photography would alleviate this problem. The other limitation of photographs, of course, is that they do not indicate the distribution of blocks in older, buried ejecta blankets, nor do they furnish positive information on variations in depth of regolith. Nonetheless, it seems clear that high-resolution photographs can serve an important function in exploration of the mare regolith, making it possible to eliminate much ground that is physically not amenable to mining. Their usefulness will increase as interpretation of their features is checked against ground truth.
Next: Stage 2 - Up: Plan of Exploration Previous: Site Selection
WCSAR-TR-AR3-9301-1
Eugene N. Cameron
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