Key Takeaways:
- The Moon’s thin atmosphere isn’t breathable for humans, but there’s a lot of oxygen trapped in lunar rocks (regolith).
- Regolith contains oxygen in minerals like oxides, but it’s not readily usable.
- Extracting oxygen from regolith is similar to electrolysis on Earth, but requires a lot of energy.
- The Moon has enough oxygen in its surface layer to sustain all humans on Earth for 100,000 years (if we can efficiently extract it).
- Despite the potential of lunar oxygen, Earth remains the ideal place for humans due to its natural resources.
Alongside advances in space exploration, we’ve recently seen much time and money invested into technologies that could allow effective space resource utilisation. The primary focus of these activities has been to determine the most efficient method of producing oxygen on the Moon.
The Moon does have an atmosphere, but it is extremely thin and primarily made up of argon, neon, and hydrogen. This isn’t the kind of gaseous mixture that oxygen-dependent mammals like humans could survive on.
Nevertheless, the Moon has a great deal of oxygen. It just isn’t in a gaseous form. Instead it’s trapped inside regolith — the layer of rock and fine dust that covers the Moon’s surface. Would there be sufficient oxygen in regolith for human habitation on the moon?
The breadth of oxygen
Numerous minerals in the earth around us contain oxygen. And the Moon is mostly made of the same rocks you’ll find on Earth (although with a slightly greater amount of material that came from meteors).
Minerals such as silica, aluminium, and iron and magnesium oxides dominate the Moon’s landscape. All of these minerals contain oxygen, but not in a form our lungs can access.
These minerals can be found on the Moon in a variety of forms, such as hard rock, dust, gravel, and stones that cover the surface. Over countless millennia, meteorites have crashed into the lunar surface, creating this material.
As a soil scientist, I’m hesitant to refer to the surface layer of the Moon as “soil” despite the fact that some people do. Soil as we know it is pretty magical stuff that only occurs on Earth. Over millions of years, a wide variety of organisms worked on the regolith, which is derived from hard rock, to create the soil.
The result is a matrix of minerals which were not present in the original rocks. The soil on Earth possesses extraordinary physical, chemical, and biological properties. Meanwhile, the materials on the Moon’s surface is basically regolith in its original, untouched form.
One substance goes in, two come out
About 45% of the regolith on the Moon is composed of oxygen. But that oxygen is tightly bound into the minerals mentioned above. In order to break apart those strong bonds, we need to put in energy.
If you are familiar with electrolysis, you may recognize this. On Earth this process is commonly used in manufacturing, such as to produce aluminium. An electrical current is passed through a liquid form of aluminium oxide (commonly called alumina) via electrodes, to separate the aluminium from the oxygen.
In this instance, the byproduct is the production of oxygen. On the Moon, the oxygen would be the main product and the aluminium (or other metal) extracted would be a potentially useful byproduct.
Although the process is fairly simple, there is a catch: it uses a lot of energy. It would require the support of solar energy or other lunar energy sources in order to be sustainable.
Extracting oxygen from regolith would also require substantial industrial equipment. Firstly, we would have to melt the solid metal oxide and either apply heat alone or in combination with solvents or electrolytes. While we have the technology to accomplish this on Earth, getting this equipment to the moon and producing enough energy to power it will be extremely difficult.
Earlier this year, Belgium-based startup Space Applications Services announced it was building three experimental reactors to improve the process of making oxygen via electrolysis. As part of the in-situ resource utilisation (ISRU) mission of the European Space Agency, they plan to send the technology to the Moon by 2025.
How much oxygen could the Moon provide?
Still, how much oxygen could the Moon really provide if we could pull it off? Actually, it turns out to be quite a bit.
We can estimate certain things if we just take into account the easily accessible regolith on the surface and ignore the oxygen bound up in the deeper hard rock material of the Moon.
Lunar regolith has an average of 1.4 tonnes of minerals per cubic meter, including roughly 630 kg of oxygen. According to NASA, in order to survive, humans require about 800 grams of oxygen per day. Thus, a person could survive for roughly two years (or slightly longer) on 630 kg of oxygen.
Let’s now assume that we can extract all of the oxygen from the regolith, which is found on the Moon at an average depth of about ten meters. This implies that for approximately 100,000 years, the upper ten meters of the Moon’s surface would supply enough oxygen to sustain all eight billion people on Earth.
This would also depend on how effectively we managed to extract and use the oxygen. In any case, this figure is truly remarkable!
That being said, life on Earth is actually rather nice for us. And since the blue planet—and its soil in particular—continues to sustain all terrestrial life without our help, we ought to exert every effort to preserve it.
