Surprisingly, the uppermost layer of the lunar surface contains a lot of oxygen.
Along with advancements in space exploration, significant time and money has recently been invested in technologies that could allow for successful space resource utilization. At the core of these efforts has been a laser-like concentration on determining the optimum approach to manufacture oxygen on the Moon.
The Australian Space Agency and NASA struck an agreement in October to deploy an Australian-made rover to the Moon as part of the Artemis mission, with the goal of collecting lunar rocks that could eventually produce breathable oxygen on the Moon.
Although the Moon has an atmosphere, it is very thin and largely made up of hydrogen, neon, and argon. It’s not the kind of gaseous combination that can support oxygen-dependent mammals like humans.
Having said that, there is plenty of oxygen on the Moon. It’s just not in a gaseous state. Instead, it’s encased in regolith, a layer of rock and fine dust that covers the Moon’s surface. Is it possible to extract enough oxygen from regolith to sustain human life on the Moon?
The range of oxygen
Many minerals discovered in the ground around us contain oxygen. And the Moon is primarily composed of the same rocks found on Earth (although with a slightly greater amount of material that came from meteors).
The Moon’s surface is dominated by minerals such as silica, aluminum, iron, and magnesium oxides. All of these minerals include oxygen, but not in the form that our lungs can use.
These minerals can be found on the Moon in a variety of forms, including hard rock, dust, gravel, and stones that cover the surface. This substance is the consequence of countless millennia of meteorite collisions on the lunar surface.
Some people refer to the Moon’s surface layer as “soil,” but as a soil scientist, I’m cautious to use that phrase. Soil, as we know it, is a miraculous substance that only exists on Earth. Over millions of years, a diverse range of species worked on the soil’s parent material – regolith, which is produced from hard rock – to build it.
The end result is a mineral matrix that was not present in the original rocks. The soil on Earth has exceptional physical, chemical, and biological properties. Meanwhile, the materials on the Moon’s surface are essentially regolith in its natural, unaltered state.
One substance enters, and two substances exit.
The regolith on the Moon is around 45 percent oxygen. However, that oxygen is strongly bonded with the aforementioned minerals. We must use energy in order to break those powerful relationships.
If you’re familiar with electrolysis, you might recognize this. This method is extensively employed in manufacturing on Earth, such as the production of aluminum. To separate the aluminium from the oxygen, an electrical current is conducted through a liquid form of aluminium oxide (usually known as alumina) via electrodes.
The oxygen is produced as a byproduct in this situation. The principal product on the Moon would be oxygen, with the aluminium (or other metal) extracted as a potentially useful byproduct.
It’s a simple operation, but there’s a catch: it consumes a lot of energy. It would need to be supported by solar energy or other energy sources available on the Moon in order to be sustainable.
Extraction of oxygen from regolith would also necessitate large amounts of industrial equipment. We’d need to transform solid metal oxide into liquid form first, either by applying heat or by combining heat with solvents or electrolytes. We have the capability to achieve this on Earth, but transporting this gear to the Moon – and generating enough energy to power it – will be a formidable task.
Earlier this year, Belgium-based startup Space Applications Services announced the construction of three experimental reactors to improve the electrolysis process of producing oxygen. They plan to launch the device to the Moon by 2025 as part of the European Space Agency’s in-situ resource utilization (ISRU) project.
How much oxygen could be provided by the Moon?
Having said that, how much oxygen might the Moon actually provide if we manage to pull it off? As it turns out, quite a bit.
We can make some estimates if we ignore the oxygen trapped in the Moon’s subsurface hard rock material and only examine regolith, which is easily accessible on the surface.
On average, each cubic metre of lunar regolith contains 1.4 tonnes of minerals, including around 630 kg of oxygen. According to NASA, humans require approximately 800 grams of oxygen every day to exist. So 630kg of oxygen would be enough to keep a human alive for around two years (or just over).
Let us now assume that the average depth of regolith on the Moon is around 10 meters and that we can extract all of the oxygen from it. That is, the top ten metres of the Moon’s surface would produce enough oxygen to sustain all eight billion people on Earth for around 100,000 years.
This would also be dependent on how well we were able to collect and use the oxygen. Regardless, this figure is incredible!
However, we do have it fairly well here on Earth. And we must do everything in our power to conserve the blue planet, particularly its soil, which sustains all terrestrial life without our intervention.
Southern Cross University Lecturer in Soil Science, John Grant
