Lunar resources

The Moon bears substantial natural resources which could be exploited in the future. Potential lunar resources may encompass processable materials such as volatiles and minerals, along with geologic structures such as lava tubes that, together, might enable lunar habitation. The in-situ use of resources on the Moon may provide a means of reducing the cost and risk of lunar exploration and beyond.
Resource mapping and sample-return missions have enhanced the understanding of the potential for lunar ISRU. An assessment in 2019 concluded that knowledge was not yet sufficient to justify the commitment of large financial resources to implement an ISRU-based campaign. The determination of resource availability will drive the selection of sites for human settlement.

Overview

Lunar materials could facilitate continued exploration of the Moon, facilitate scientific and economic activity in the vicinity of both Earth and Moon, or they could be imported to the Earth's surface where they would contribute directly to the global economy. Regolith is the easiest product to obtain; it can provide radiation and micrometeoroid protection as well as construction and paving material by melting. Oxygen from lunar regolith oxides can be a source for metabolic oxygen and rocket propellant oxidizer. Water ice can provide water for radiation shielding, life-support, oxygen and rocket propellant feedstock. Volatiles from permanently shadowed craters may provide methane, ammonia, carbon dioxide and carbon monoxide. Metals and other elements for local industry may be obtained from the various minerals found in regolith.
The Moon is known to be poor in carbon and nitrogen, and rich in metals and in atomic oxygen, but their distribution and concentrations are still unknown. Further lunar exploration will reveal additional concentrations of economically useful materials, and whether or not these will be economically exploitable will depend on the value placed on them and on the energy and infrastructure available to support their extraction. For in situ resource utilization to be applied successfully on the Moon, landing site selection is imperative, as well as identifying suitable surface operations and technologies.
Scouting from lunar orbit by a few space agencies is ongoing, and landers and rovers are scouting resources and concentrations in situ.

Resources

, oxygen, and metals are abundant resources on the Moon. Elements known to be present on the lunar surface include, among others, hydrogen, oxygen, silicon, iron, magnesium, calcium, aluminium, manganese and titanium. Among the more abundant are oxygen, iron and silicon. The atomic oxygen content in the regolith is estimated at 45% by weight.
Studies from Apollo 17's Lunar Atmospheric Composition Experiment show that the lunar exosphere contains trace amounts of hydrogen, helium, argon, and possibly ammonia, carbon dioxide, and methane. Several processes can explain the presence of trace gases on the Moon: high energy photons or solar winds reacting with materials on the lunar surface, evaporation of lunar regolith, material deposits from comets and meteoroids, and out-gassing from inside the Moon. However, these are trace gases in very low concentration. The total mass of the Moon's exosphere is roughly with a surface pressure of 3×10⁻¹⁵ bar. Trace gas amounts are unlikely to be useful for in situ resource utilization.

Solar power

lasts approximately two weeks, followed by approximately two weeks of night, while both lunar poles are illuminated almost constantly. The lunar south pole features a region with crater rims exposed to near constant solar illumination, yet the interior of the craters are permanently shaded from sunlight.
Solar cells could be fabricated directly on the lunar soil by a medium-size rover with the capabilities for heating the regolith, evaporation of the appropriate semiconductor materials for the solar cell structure directly on the regolith substrate, and deposition of metallic contacts and interconnects to finish off a complete solar cell array directly on the ground. This process however requires the importation of potassium fluoride from Earth to purify the necessary materials from regolith.

Nuclear power

The Kilopower nuclear fission system is being developed for reliable electric power generation that could enable long-duration crewed bases on the Moon, Mars and destinations beyond. This system is ideal for locations on the Moon and Mars where power generation from sunlight is intermittent. Uranium and thorium are both present on the Moon, but due to the high energy density of nuclear fuels, it could be more economical to import suitable fuels from Earth rather than producing them in situ.
Radioisotope thermoelectric generators are another form of nuclear power which use the natural decay of radioisotopes rather than their induced fission. They have been used in space—including on the Moon—for decades. The usual process is to source the suitable substances from Earth, but plutonium-238 or strontium-90 could be produced on the Moon if feedstocks such as spent nuclear fuel are present. RTGs could be used to deliver power independent of available sunlight, for both lunar and non-lunar applications. RTGs do contain harmful toxic and radioactive materials, which leads to concerns of unintentional distribution of those materials in the event of an accident. Protests by the general public therefore often focus on the phaseout of RTGs, due to an overestimation of the dangers of radiation.
A more theoretical lunar resource are potential fuels for nuclear fusion. Helium-3 has received particular media attention as its abundance in lunar regolith is higher than on Earth. However, thus far nuclear fusion has not been employed by humans in a controlled fashion releasing net usable energy. Furthermore, while helium-3 is required for one possible pathway of nuclear fusion, others instead rely on nuclides which are more easily obtained on Earth, such as tritium, lithium or deuterium.

Oxygen

The elemental oxygen content in the regolith is estimated at 45% by weight. Oxygen is often found in iron-rich lunar minerals and glasses as iron oxide. Such lunar minerals and glass include ilmenite, olivine, pyroxene, impact glass, and volcanic glass. Various isotopes of oxygen are present on the Moon in the form of ¹⁶O, ¹⁷O, and ¹⁸O.
At least twenty different possible processes for extracting oxygen from lunar regolith have been described, and all require high energy input: between 2–4 megawatt-years of energy to produce 1,000 tons of oxygen. While oxygen extraction from metal oxides also produces useful metals, using water as a feedstock does not. One possible method of producing oxygen from lunar soil requires two steps. The first step involves the reduction of iron oxide with hydrogen gas to form elemental iron and water. Water can then be electrolyzed to produce oxygen which can be liquified at low temperatures and stored. The amount of oxygen released depends on the iron oxide abundance in lunar minerals and glass. Oxygen production from lunar soil is a relatively fast process, occurring in a few tens of minutes. In contrast, oxygen extraction from lunar glass requires several hours.
Human oxygen consumption depends on physical activity and is affected by diet and also gravity. A commonly assumed round number for -production of humans of low to moderate physical activity assumes being exhaled per person per day. In the microgravity-environment of the International Space Station this value can be as low as per person per day. If one conservatively assumes that one mole of oxygen is consumed per mole of carbon dioxide produced 2.2 kg of carbon dioxide produced are equivalent to of oxygen consumed. The yearly oxygen need of a human would thus be roughly and per the above-mentioned energy requirements about 1.3-2.6 kilowatts would be constantly required per person to produce this amount of oxygen from lunar rocks. For comparison the average per person electricity consumption in the US in 2022 was or about 1,462 Watts.

Water

Cumulative evidence from several orbiters strongly indicate that water ice is present on the surface at the Moon poles, but mostly on the south pole region. However, results from these datasets are not always correlated. It has been determined that the cumulative area of permanently shadowed lunar surface is 13,361 km² in the northern hemisphere and 17,698 km² in the southern hemisphere, giving a total area of 31,059 km². The extent to which any or all of these permanently shadowed areas contain water ice and other volatiles is not currently known, so more data is needed about lunar ice deposits, its distribution, concentration, quantity, disposition, depth, geotechnical properties and any other characteristics necessary to design and develop extraction and processing systems. The intentional impact of the LCROSS orbiter into the crater Cabeus was monitored to analyze the resulting debris plume, and it was concluded that the water ice must be in the form of small, discrete pieces of ice distributed throughout the regolith, or as a thin coating on ice grains. This, coupled with monostatic radar observations, suggest that the water ice present in the permanently shadowed regions of lunar polar craters is unlikely to be present in the form of thick, pure ice deposits.
Water may have been delivered to the Moon over geological timescales by the regular bombardment of water-bearing comets, asteroids and meteoroids or continuously produced in situ by the hydrogen ions of the solar wind impacting oxygen-bearing minerals.
The lunar south pole features a region with crater rims exposed to near constant solar illumination, where the craters' interior are permanently shaded from sunlight, allowing for natural trapping and collection of water ice that could be mined in the future.
Water molecules can be broken down to form molecular hydrogen and molecular oxygen to be used as rocket bi-propellant or produce compounds for metallurgic and chemical production processes. Just the production of propellant, was estimated by a joint panel of industry, government and academic experts, identified a near-term annual demand of 450 metric tons of lunar-derived propellant equating to 2,450 metric tons of processed lunar water, generating US$2.4 billion of revenue annually.