Along with advances in space exploration, we have recently seen a lot of time and money invested in technologies that could enable use of space resources. And at the forefront of these efforts has been the emphasis on finding the best way to produce oxygen on the moon.
In October, the Australian Space Agency and NASA signed an agreement send an Australian-made rover to the moon as part of the Artemis program, with the aim of collecting moon rocks that could ultimately provide breathable oxygen to the moon.
Although the Moon has an atmosphere, it is very thin and composed mostly of hydrogen, neon, and argon. It’s not the kind of gas mixture that could support oxygen-dependent mammals like humans.
That said, there is actually a lot of oxygen on the Moon. It’s just not in a gaseous form. Instead, it’s trapped inside the regolith – the layer of rock and fine dust that covers the surface of the Moon. If we could extract oxygen from regolith, would that be enough to support human life on the moon?
The extent of oxygen
Oxygen can be found in many minerals in the soil around us. And the Moon is mostly made up of the same rocks you’ll find on Earth (albeit with a slightly larger amount of material coming from meteors).
Minerals such as silica, aluminum, and oxides of iron and magnesium dominate the lunar landscape. All of these minerals contain oxygen, but not in a form that our lungs can access.
On the Moon, these minerals exist in different forms, including hard rock, dust, gravel, and stones covering the surface. This material is the result of impacts from meteorites crashing into the lunar surface over countless millennia.
Some people call the Moon’s surface layer lunar âsoilâ, but as a soil scientist I hesitate to use that term. The ground as we know it is a pretty magical thing that only happens on Earth. It was created by a wide variety of organisms working on the soil’s parent material – regolith, derived from hard rock – over millions of years.
The result is a matrix of minerals that were not present in the original rocks. Earth’s soil is steeped in remarkable physical, chemical and biological characteristics. Meanwhile, the materials on the Moon’s surface are essentially regolith in its original, untouched form.
One substance goes in, two goes out
You might be familiar with this if you are familiar with electrolysis. On Earth, this process is commonly used in manufacturing, for example to produce aluminum. An electric current passes through a liquid form of aluminum oxide (commonly called alumina) via electrodes, to separate the aluminum from the oxygen.
In this case, oxygen is produced as a by-product. On the Moon, oxygen would be the main product and the aluminum (or other metal) extracted would be a potentially useful by-product.
It’s a pretty straightforward process, but there’s a catch: it’s very power hungry. To be sustainable, it should be supported by solar power or other energy sources available on the Moon.
The extraction of oxygen from regolith would also require significant industrial equipment. We should first convert the solid metal oxide to liquid form, either by applying heat or by combining heat with solvents or electrolytes. We have the technology to do this on Earth, but moving this device to the Moon – and generating enough energy to operate it – will be a tall order.
Earlier this year, Belgian startup Space Applications Services announced it was building three experimental reactors to improve the process of making oxygen by electrolysis. They plan to send the technology to the moon by 2025 as part of the European Space Agency’s In Situ Resource Use (ISRU). mission.
How Much Oxygen Could the Moon Provide?
That said, when we do manage to pull it out, how much oxygen could the Moon actually be providing? Well, a lot in the end.
If we ignore the oxygen trapped in the Moon’s deeper hard rock – and just consider the regolith that’s easily accessible on the surface – we can make some estimates.
Each cubic meter of lunar regolith contains an average of 1.4 tonnes of minerals, including about 630 kilograms of oxygen. NASA says humans need to breathe 800 grams of oxygen per day to survive. Thus, 630 kg of oxygen would keep a person alive for about two years (or a little more).
Suppose now that the average depth of the regolith on the Moon is about ten meters, and that we can extract all the oxygen from it. This means that the top ten meters of the Moon’s surface would provide enough oxygen to support the eight billion people on Earth for about 100,000 years.
It would also depend on how efficiently we were able to extract and use the oxygen. Anyway, this figure is pretty amazing!
That said, we have it pretty well here on Earth. And we must do all we can to protect the blue planet – and its soil in particular – which continues to support all life on earth without us even trying.