This article was first published by The Conversation. Space.com's Expert voices: Op-Ed and Insights was contributed by the publication.
Southern Cross University, John Grant, Lecturer, Soil Science
We've seen a lot of money and time invested in technologies that can allow for efficient space resource utilization. This is in addition to advances made in space exploration. The focus has been on how to make oxygen on the moon.
The Australian Space Agency and NASA agreed to send a rover made in Australia to the Moon under the Artemis program. This rover will be used to collect lunar rocks which could eventually provide oxygen to the moon.
The moon has an atmosphere, but it is very thin and mostly composed of hydrogen, neon, and argon. It is not the type of gaseous mixture that would sustain oxygen-dependent mammals like humans.
Despite this, the moon actually has plenty of oxygen. It's just not in a gaseous state. It's instead trapped in regolith, the layer of rock and fine powder that covers the surface of the moon. Would it be enough oxygen to sustain human life on the Moon if we could extract oxygen from regolith?
Similar: Moon photos taken by NASA's Lunar Reconnaissance Orbiter
The range of oxygen
Many minerals found in the earth's ground contain oxygen. The moon is made mostly of the same rocks as Earth, although it contains a little more material from meteorites.
The moon's surface is dominated by minerals such as silica and aluminum. These minerals all contain oxygen, but they are not in the form that our lungs can absorb.
These minerals can be found on the moon in many forms, including hard rock, dust and gravel, as well as covering the surface with stones. Over countless millennia, meteorites have crashed into the lunar surface.
Although some people refer to the moon's surface as "soil," I hesitate to use that term as a soil scientist. It is a magical, only on Earth-created substance that we call soil. Over millions of years, it was created by many organisms that worked on soil's parent material, regolith.
This results in a matrix of minerals that are not found in the original rocks. The soil of Earth is rich in remarkable biological, chemical, and physical characteristics. The moon's surface, however, is largely made up of regolith, which is its original, unaltered form.
Two substances go in, one goes out
About 45% of the moon's regolith contains oxygen. However, that oxygen is tightly bound to the minerals listed above. We need energy to break down these strong bonds.
This might sound familiar if you are familiar with electrolysis. This process is used to make aluminum. To separate aluminum from oxygen, an electrical current is passed through the liquid form of aluminum oxide (commonly known as alumina) via electrodes.
The oxygen is produced as an afterproduct in this instance. The oxygen on the moon would be the main product, while the aluminum (or any other metal) would be a byproduct.
Although it is quite straightforward, it is very energy-hungry. It would have to be powered by solar energy, or other sources of energy from the moon in order to be sustainable.
It would require significant industrial equipment to extract oxygen from regolith. First, we would need to convert solid metal oxide into liquid form by heating it or using heat combined with solvents and electrolytes. Although we have the technology to do it on Earth, moving the apparatus to the Moon and creating enough energy to power it will prove difficult.
Space Applications Services, a Belgian startup, announced earlier this year that it was building three experimental reactors for improving the process of electrolysis to make oxygen. The European Space Agency's in situ resource utilization (ISRU mission) will see them send the technology to orbit by 2025.
An astronaut using an instrument to reach the surface of the Moon. NASA image credit
How much oxygen could the Moon provide?
However, how much oxygen can the moon deliver if we are able to do it? It turns out, quite a bit.
We can make some estimates if we forget about oxygen trapped in moon's harder rock material and instead consider regolith, which is readily accessible on the surface.
On average, each cubic meter lunar regolith contains about 1.4 tonnes of minerals. This includes approximately 630 kilograms oxygen. NASA states that humans require 800 grams of oxygen per day to live. A person would need to breathe 630 kilograms of oxygen per day to stay alive for approximately two years.
Let's say that the average depth of moon regolith is about ten metres and that it can be extracted all the oxygen. This means that the top ten metres of the moon's crust would contain enough oxygen to sustain all 8 billion people for around 100,000 years.
It would also depend on how efficiently we extracted and used oxygen. This figure is amazing, however.
However, it is quite good on Earth. We should protect the blue planet and its soil, which continue to support all terrestrial life.
This article was republished by The Conversation under Creative Commons. You can read the original article.
Follow Expert Voices on Facebook and Twitter to follow all the debates and issues. These views are the author's and may not reflect those of the publisher.