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Lunar & Martian Mineralogy

Background - Lunar & Martian Mineral Prospecting

Prospecting can be either speculative or directed - parallels can be drawn between automated robot prospectors (using inference grids) and human prospectors from the frontier days. The California and Alaska gold rushes were examples of directed prospecting - they had maps, evidence of gold, and knowledge of where to look for gold after following the maps. The speculative prospectors were those who only had the desire to find assayable claims, without maps or mineral evidence - they wandered about looking in streambeds, faultlines, and rockfalls without any predetermined mineral in mind, looking for mineral "markers".

Most of the initial prospecting on Luna or Mars will be, by necessity, directed. That is, the prospecting robot fleet will be directed towards areas with a high likelihood of minerals necessary to the colony. As the habitat becomes more established, it can include more speculative prospecting.

The prospecting task itself can be split into two mineral-related areas, industrial and strategic. Industrial minerals are those mined primarily for local (Lunar/Martian) construction and infrastructure use, while strategic minerals, as on Earth, comprise those that are technologically important and commercially viable.

These four combinations of prospecting types and tasks will need different levels of complexity in their inference grids, especially at the supervisory level.

LUNAR MINERALS

There are, at present, 35 validated [MinDat] mineral species on the Moon

The primary prospecting will be for water/ice - however, most of the water/ice deposits mapped by earlier missions are either at both poles or in permanently shadowed craters. As the proposed Lunar landing site is not known, it's likely the prospecting robot fleet would instead prospect for other industrial minerals.

Industrial-mineral prospecting would appear to be fairly straightforward. The minerals are available in large amounts and widely disseminated, simplifying the supervisory-level inference grid data.

A lot of the Moon's surface rock is anorthite (a plagioclastic feldspar) - the aluminum-calcium silicate endmember of the anorthite-albite (aluminum-sodium silicate) series and a common rock-forming mineral here on earth and especially on the moon. It's almost 20% (18.97%) aluminum and would be the primary ore for aluminum (it's a secondary aluminum ore on earth, where bauxite is economically infeasible to process) and calcium. In addition to construction uses, aluminum would also be used for wiring - copper is not present to any appreciable extent on either Luna or Mars (and, as are most construction materials, is not cost-effective to transport). Aluminum wire, of course, is also a lot easier to solder/weld in lunar atmosphere as the oxide doesn't form.

Anorthite, besides being a lunar aluminum-calcium ore, is the raw material for aluminosilicate glass [see the Artemis Project]. It does require a relatively high-temperature (1550C) furnace, though.

Also, anorthite would be useful as a "spraycrete", a sprayed-on slurry that would harden quickly in the lunar atmosphere. It could be applied to mylar sheeting for above-ground enclosures for both thermal insulation and micrometeorite protection.

The lunar maria are composed of basalt, a dark fine-grained rock comprising the plagioclastic feldspars (mostly anorthite in this case), pyroxenes, and olivine. The maria contain the vast majority of the moon's iron (the impacted meteorites comprise the rest) - only around 15% iron by weight and in a more difficult form to extract.

Strategic minerals, on the other hand, are either uncommon, well beneath the lunar surface, or very localized. For example, GPR, magnetometer, and gravimetric instrumentation (among others) would be needed to prospect for buried mass concentrations (mascons); nickel-iron or platinum-group minerals (PGM) meteorites. Since the Moon has a cold core (the radioactive heating caused by 26Al early in the Moon's formation - the "giant accretion" theory - was enough to coalesce a basaltic core and allow early meteorite impacts to create the basaltic maria), mascons could be found anywhere. Because 26Al has a short (geologically-speaking) half-life of only 730 Kyrs, the Moon's core has long since cooled off - thus there's no volcanism or plate tectonics to bring minerals up from deep underground.

Chromite (chromium iron oxide) has been found in the breccia (cemented aggregates) at Fra Mauro (Apollo 14), Mare Tranquillitas, and aluminian chromite at Mare Tranquillitas from which chromium can be recovered. There's ilmenite (iron titanium oxide) at Fra Mauro, Mare Fecunditatis, Mare Tranquillitas and rutile (titanium dioxide) at Fra Mauro from which titanium can be recovered - there's also niobian rutile, if enough of that is available, would certainly be a commodity (for the niobium, used in superconductors and stainless steels). Troilite (iron II sulfide) has been found in the Taurus-Littrow Valley (Apollo 17).

Sampling on the lurnar surface may be more difficult than it appears. Most of the surface is coated with finely divided dust (regolith), but because of the hard vacuum, the coefficient of friction may be at least 60 times higher than the same dust under normal atmosphere - thus requiring sampling tool surfaces to be coated (with Teflon or similar material) to reduce the forces necessary to obtain samples. Conversely, even though the average lunar density is relatively low (anorthite's S.G. is 2.73), the layer immediately beneath the dust is so compacted due to micrometeoritic vibration, that Apollo mission core sampler bits seized up and could not be extracted. Also, of course, the lunar temperature extremes (-170C to +140C) necessitate equipment being designed accordingly.

MARTIAN MINERALS

There are maybe a dozen or so (identified) minerals on Mars - most of them with significant iron content: So, again, the industrial mineral prospecting - iron for construction - should be relatively easy; the iron hydoxy(oxides) are everywhere. Maghemite is strongly magnetic, which might add a magnetics dataset to the inference grid..

The gypsum deposit extent is unknown - if enough is available, then it could be used for insulation, drywall, and water extraction.

It's not known if there are any strategic minerals on Mars.

The information above was gleaned from various information sources - see our Related Information.