Sheyna Gifford

Oct 7th 2022

Using Lunar Soil to Make Oxygen on the Moon


With NASA planning to bring astronauts back to the moon by 2024 and make lunar missions sustainable by 2028, the space race part two is on. The challenge this round? Go there to stay. In the drive to produce water, power, fuel and food, we’re going to tap into every readily available resource: lunar soil, solar energy and even somewhat threadbare helium, neon and hydrogen atmosphere clinging to our moon’s rugged surface. It’s all up for grabs, but what can we do with it?

For starters: We can make oxygen on the moon.

Lighting Up the Night: Making Oxygen and Power on the Moon

Making something out of nothing usually involves breaking the laws of physics — making oxygen on the moon only involves using water to break up lunar soil.

To make oxygen on the moon, researchers at Nanjing University recently proposed using a process a bit like terrestrial photosynthesis. The process starts with lunar soil, which is rich in iron and titanium. Thanks to the presence of those elements, when scientists added water to lunar soil samples returned by the Chang’e 5 moon rover, it kicked off a very useful chemical reaction. As has been observed in some places on Earth, including Antarctica, iron in the water-hungry soil donated electrons to the oxygen and hydrogen in the water. The result: both O2 and H2 were released.

The research team noted that with this simple maneuver, the lunar samples readily produced not only breathable air, but also a potential source of fuel. In a future lunar base, carbon dioxide from astronauts’ exhaled breath could be added to the H2 released by rehydrated lunar soil. Under the right conditions, H2 and CO2 create methane. Methane is a component of rocket fuel.

If future denizens of the moon’s surface add even more oxygen and hydrogen to the methane mix, they might make methanol — which is toxic to humans if ingested, but also an excellent source of energy. If burned purely, methanol returns all of its original components in the form of water and carbon dioxide. This kind of combustion on Earth is the basis for gasoline engines, among other things. It could be used as a similar source of propellant on the moon or simply stored until more water and carbon dioxide are needed. If there are no leaks in the system, this kind of process would make a future lunar base more energy-independent than most homes in America.

This is one possible approach to making oxygen on the moon, and has the advantage of not requiring an external power source. In this reaction, the lunar loam itself acts as a battery. But this method of turning the moon’s resources into humanity’s air and water 238,855 miles (384,400 km) from home is not the only one, not by a long shot. Another approach involves cooking lunar soil instead of adding water to it.

An Alternative to Extraterrestrial Photosynthesis

Part of the reason that the iron in lunar soil is ready and able to give up oxygen when hydrated is that this iron is bound up with oxygen in the form of iron oxide. Another pairing, silicon oxide, the most abundant component of sand, is plentiful on the moon. Like iron oxide, silicon dioxide (SiO2 or silica) has been shown to release oxygen when heated. In previous eras, silicon dioxide was a problem for lunar explorers. It is fine, sticky and reactive. Silica from lunar dust clung to the Apollo astronaut suits, followed the crew into their cabins and even gave astronaut Jack Schmitt a nasty case of nasal congestion.

This time around, the gun-powder-smelling lunar dust could be a source of easier breathing instead of clogged sinuses. For this second process to successfully leach the O2 out of SiO2, it takes two steps instead of one, but, as a bonus, does not require adding precious water. Quite the contrary: it requires hydrogen and methane. As luck and science would have it, the first process described here, where lunar samples are rehydrated, produces both. So both processes could come in handy, depending on whether the lunar base is rich in water or rich in hydrogen at any given time. Both processes require carbon dioxide. Fortunately, owing to the respiratory efforts of every human being on the moon, future lunar bases are likely to be well-supplied with CO2.

Making Moonshine

The moon shines brightly in our sky partly because of the SiO2 its surface — SiO2 that tends to burn rapidly in the presence of oxygen or anything reactive. Last time we went to the moon, those same shining dust particles clogged up spacesuit visors, coated equipment and cut through all of the seals on the supposedly air-tight containers the Apollo astronauts used to collect lunar samples. Nothing on the moon was safe from it. This time, building habitats and life support systems that survive long-term with minimal support from Earth is going to require that we do more than survive the lunar dust. Settling on our nearest satellite for the long haul is going to require us to dig in and master it.

Cooking or hydrating lunar soil to make oxygen on the moon is not just a matter of breathing, but of using chemistry to turn the tables on one of the most confounding substances humankind as encountered in space to date. Neutralizing reactive lunar soil with water or heat converts an explorer’s natural enemy into an invaluable friend: one that could fuel lunar exploration for generations to come.

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