Along with advances in space exploration, we have recently seen a lot of time and money invested in technologies that could enable efficient use of space resources. And at the forefront of these efforts has been a sharp focus on finding the best way to produce oxygen on the Moon.
In October, the Australian Space Agency and NASA signed an agreement to send an Australian-made rover to the Moon under the Artemis program, with the aim of collecting lunar rocks that could ultimately provide breathable oxygen on the Moon.
Although the Moon has an atmosphere, it is very thin and is made up mostly of hydrogen, neon, and argon. It’s not the kind of gaseous mixture that could sustain oxygen-dependent mammals like humans.
That said, there is actually a lot of oxygen on the Moon. It just isn’t in gaseous form. Instead, it’s trapped inside regolith, the layer of rock and fine dust that covers the Moon’s surface. If we could extract oxygen from the regolith, would it be enough to support human life on the Moon?
The amplitude of oxygen
Oxygen can be found in many of the minerals in the soil around us. And the Moon is made up of mostly the same rocks you’ll find on Earth (albeit with a slightly larger amount of material from meteorites).
Minerals like silica, aluminum, iron, and magnesium oxides 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 a few different forms, including hard rock, dust, gravel, and stones that cover the surface. This material developed as a result of meteorites crashing into the lunar surface over countless millennia.
Some people call the surface layer of the Moon lunar “soil”, but as a soil scientist, I hesitate to use this term. Soil as we know it is a pretty magical thing that only happens on Earth. It has been created by a wide variety of organisms working on the original soil 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 imbued with remarkable physical, chemical, and biological characteristics. Meanwhile, the materials on the Moon’s surface are regolith in its original, intact form.
One substance goes in, two come out
The Moon’s regolith is made up of about 45% oxygen. But that oxygen is strongly bound to the minerals mentioned above. To break those strong bonds, we need to put energy.
You may be familiar with this if you know about electrolysis. On Earth, this process is commonly used in manufacturing, such as to produce aluminum. An electrical current is passed through a liquid form of aluminum oxide (commonly called alumina) through electrodes, to separate the aluminum from oxygen.
In this case, oxygen is produced as a by-product. On the Moon, oxygen would be the main product and the extracted aluminum (or other metal) would be a potentially useful by-product.
It is a fairly simple process, but there is a problem: it consumes a lot of energy. To be sustainable, it would need to be supported by solar power or other energy sources available on the Moon.
The extraction of oxygen from the regolith would also require substantial industrial equipment. We would first need to convert the solid metal oxide into a liquid form, either by applying heat or heat combined with solvents or electrolytes. We have the technology to do this on Earth, but moving this device to the Moon and generating enough power to run it will be a big challenge.
Earlier this year, Belgium-based startup Space Applications Services announced that it was building three experimental reactors to improve the process of producing oxygen through electrolysis. They hope to send the technology to the Moon by 2025 as part of the European Space Agency’s In Situ Resource Utilization (ISRU) mission.
How much oxygen could the Moon provide?
That said, when we do get there, how much oxygen could the Moon actually deliver? Well, quite a lot, as a result.
If we ignore the oxygen trapped in the hard rock material deeper on the Moon, and only consider the regolith, which is readily accessible on the surface, we can get some estimates.
Each cubic meter of lunar regolith contains an average of 1.4 tons of minerals, including about 630 kilograms of oxygen. NASA says that humans need to breathe about 800 grams of oxygen a day to survive. So 630 kg of oxygen would keep a person alive for about two years (or little more).
Now suppose that the average depth of the regolith on the Moon is about ten meters and that we can extract all the oxygen from this. That means 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.
This would also depend on how efficiently we managed to extract and use the oxygen. Anyway, this figure is quite amazing!
Having said that, we’ve got it pretty good here on Earth. And we should do everything we can to protect the blue planet, and its soil in particular, which continues to support all life on Earth without our trying.
This article by John Grant, professor of soil sciences, Southern Cross University is republished from The Conversation under a Creative Commons license. Read the original article.