Crawford reported in 2015 that there is growing interest in the possibility that the resource base of the Solar System might in the future be used to supplement the economic resources of our own planet. As the Earth's closest celestial neighbour, the Moon is sure to feature prominently in these developments. In this paper the author reviewed what is currently known about economically exploitable resources on the Moon, while also stressing the need for continued lunar exploration.
The author found that, although it is difficult to identify any single lunar resource that will be sufficiently valuable to drive a lunar resource extraction industry on its own (notwithstanding claims sometimes made for the 3He isotope, which the author found to be exaggerated), the Moon nevertheless does possess abundant raw materials that are of potential economic interest. These are relevant to a hierarchy of future applications, beginning with the use of lunar materials to facilitate human activities on the Moon itself, and progressing to the use of lunar resources to underpin a future industrial capability within the Earth-Moon system. In this way, gradually increasing access to lunar resources may help 'bootstrap' a space-based economy from which the world economy, and possibly also the world's environment, will ultimately benefit.
The author concluded that it is clear that the Moon does possess abundant raw materials that are of potential economic value for future human activities, and especially for future activities in space. It is true that, on the basis of current knowledge, it is difficult to identify any single lunar resource that is likely to be sufficiently valuable to drive a lunar resource extraction industry which has near-term profit as an objective. In particular, the author has argued that claims for lunar 3He in this respect, through its alleged ability to make a major contribution to Earth’s future energy needs, have been exaggerated. Rather, the author has identified a hierarchy of applications for lunar resources, beginning with the use of lunar materials to facilitate human activities on the Moon itself (including scientific exploration, resource prospecting, and, perhaps, tourism), progressing to the use of lunar resources to underpin a growing industrial capability in cis-lunar space. In this way, gradually increasing access to lunar resources may help ‘bootstrap’ a space-based economy from modest beginnings on the lunar surface until much of the inner Solar System lies within the sphere of human economic activity (e.g. Wingo, 2004; Spudis and Lavoie 2011; Metzger et al. 2013).
In the fullness of time, this has the potential to yield significant economic benefits to human society on Earth by opening the world economy to external sources of energy and raw materials. Of course, the Moon is not the only source of extraterrestrial raw materials which could contribute to the development of such a space-based economy, and NEAs are often discussed in this context. However, while resources from NEAs will doubtless come to play an important role, the Moon is likely to remain of central importance because of its constant proximity, its probable concentrations of accessible volatiles (especially water ice at the poles), and the fact that diverse lunar geological processes have concentrated many economically important materials (e.g. Ti, Al, the REEs, and U) in crustal reservoirs to levels which far exceed those found in most known asteroid classes.
The Moon also has abundant energy, in the form of sunlight, to extract and process these materials in situ. Moreover, although it has long been considered that NEAs would be the preferred extraterrestrial sources for iron, nickel and the PGMs (e.g. Kargel, 1994; Elvis, 2012), the possibility that the Moon may retain partially intact iron and/or chondritic meteorites (Wingo, 2004; Wieczorek et al., 2012) means that it may become a useful source for these materials as well. This is likely to be especially true if a local infrastructure is developed to support the utilisation of other lunar materials. Indeed, it is
the fact that the lunar surface has the potential to support a growing scientific and industrial infrastructure, in a way that asteroidal surfaces do not, which is likely to make the Moon the linchpin of humanity’s future utilisation of the Solar System.
Finally, it is necessary to reiterate that the general knowledge of lunar geological evolution, and therefore of the extent to which the Moon may offer economically useful resources in addition to those identified above, is still very incomplete. Gaining a more complete picture of the Moon’s economic potential will require a much more ambitious program of lunar exploration than has been conducted to-date, and this will probably require the return of human explorers to the lunar surface. Fortunately, such a programme is under active international discussion.
In 2013 the world’s space agencies came together to develop the Global Exploration Roadmap (ISECG, 2013), which outlines possible international contributions to human and robotic missions to the Moon, NEAs and, eventually, Mars. Implementation of this Roadmap will provide many opportunities for
the detailed scientific investigation of the Moon which, in addition to numerous scientific benefits (e.g. Crawford et al., 2012, and references cited therein), will also result in a much clearer picture of lunar resource potential.
[Also see Chapter 9 of AAPG-EMD Memoir 101 (here)]