difficulty encountered in scaling up the process. The pilot plant test stage needs to be made for each new mineral deposit. Full Scale Mine and Plant Start Up. Invariably, problems develop at this stage. If the pilot plant tests are conducted properly, modifications of the mine and plant can be kept to a minimum. Later modifications to the plant will be made after the plant is in operation to improve its efficiency and product quality. The above four steps are essential for developing a terrestrial mining and mineral processing plant. These steps must be rigorously followed for the additional unknowns that will be encountered in extraterrestrial environments. Exploration It was noted above that the most important criterion of a potential ore is its concentration of the desired material. This stems from the difficulty, already emphasized and to be illustrated, of separating elements. It is thus highly cost-effective to find places where nature has done as much of the separation as possible. This is exploration. In terrestrial minerals exploration, samples are collected widely, almost all of which could not possibly be ore. Such sampling is carried out to establish a geologic context to find where ore might be. Seeking out such concentrated deposits of desired materials is critical before committing to the enormous risk and capital expenditure of a extraterrestrial mine. On the Moon, we have just begun to establish an economic-geology context. Basing mining and extraction scenarios on the ordinary country rock sampled at the handful of sites directly sampled in the Apollo and Luna missions, and indirectly sampled by the lunar meteorites, compromises the value of lunar fractionation. Despite the conventional wisdom in some quarters that the Moon is a dull, homogeneous rock, concentrations of common elements must certainly occur locally on the Moon, and anomalous deposits of rare elements are probable as well (e.g., Haskin et al., 1991), as the Moon is a large, complex body that underwent extensive igneous differentiation over a significant fraction of geologic time. Further telescopic exploration of the Moon is a first step, as with the current multispectral imaging of the near side of the Moon. Stereographic techniques can provide topographic information. In addition to compositional and topographic data, the surface maturity and percentage of agglutinates can be measured (e.g., Johnson, 1990). Orbital observations, however, will be needed to improve on the Earthbased data and to extend them into the near ultraviolet and infrared parts of the spectrum (e.g., Johnson, 1990). Landers and roving teleoperated or automated mappers will be needed to map, sample and analyze favorable areas found from orbit. From these sites, the best will be selected for further sampling. Samples can
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