The Moon’s top layer alone has enough oxygen to sustain 8 billion people for 100,000 years
John Grant, Lecturer in Soil Science, Southern
Cross University
Disclosure statement
John Grant is affiliated with the human race and as
such he has a vested interest in maintaining their ongoing existence. He,
therefore, tends to advocate for planet earth, the natural home of the human
race. He also has strong feelings for soil which plays a critical role in
earth's ecosystems and which has nurtured the emotional, physical, and
spiritual health of human beings since their first beginnings.
Alongside advances in space exploration, we’ve
recently seen much time and money invested into technologies that could allow
effective space resource utilisation. And at the forefront of these efforts has
been a laser-sharp focus on finding the best way to produce oxygen on the Moon.
In October, the Australian Space Agency and NASA
signed a deal to send an Australian-made rover to the Moon under the Artemis
program, with a goal to collect lunar rocks that could ultimately provide
breathable oxygen on the Moon.
Although the Moon does have an atmosphere, it’s
very thin and composed mostly of hydrogen, neon and argon. It’s not the sort of
gaseous mixture that could sustain oxygen-dependent mammals such as humans.
That said, there is actually plenty of oxygen on
the Moon. 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. If we could
extract oxygen from regolith, would it be enough to support human life on the
Moon?
Oxygen can be found in many of the minerals in the
ground around us. 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.
On the Moon these minerals exist in a few different
forms including hard rock, dust, gravel and stones covering the surface. This
material has resulted from the impacts of meteorites crashing into the lunar
surface over countless millennia.
Some people call the Moon’s surface layer lunar
“soil”, but as a soil scientist I’m hesitant to use this term. Soil as we know
it is pretty magical stuff that only occurs on Earth. It has been created by a
vast array 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 which 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 is basically regolith in its original, untouched form.
One substance goes in, two come out
The Moon’s regolith is made up of approximately 45%
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.
You might be familiar with this if you know about
electrolysis. 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 case, the oxygen is produced as a
byproduct. On the Moon, the oxygen would be the main product and the aluminium
(or other metal) extracted would be a potentially useful byproduct.
It’s a pretty straightforward process, but there is
a catch: it’s very energy hungry. To be sustainable, it would need to be
supported by solar energy or other energy sources available on the Moon.
There are multiple alumina (aluminium oxide)
refineries in Australia, including this one pictured in Gladstone, Queensland.
Aluminium is produced in two stages. Before pure aluminium can be released
using electrolysis (in what is known as the Hall-Heroult process), alumina
refineries must first refine naturally occurring bauxite ore to extract the
alumina (from which pure aluminium is later retrieved). Dave Hunt/AAP
Extracting oxygen from regolith would also require
substantial industrial equipment. We’d need to first convert solid metal oxide
into 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 apparatus
to the Moon – and generating enough energy to run it – will be a mighty
challenge.
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. They expect to send the
technology to the Moon by 2025 as part of the European Space Agency’s in-situ
resource utilisation (ISRU) mission.
How much oxygen could the Moon provide?
That said, when we do manage to pull it off, how
much oxygen might the Moon actually deliver? Well, quite a lot as it turns out.
If we ignore oxygen tied up in the Moon’s deeper
hard rock material — and just consider regolith which is easily accessible on the
surface — we can come up with some estimates.
Each cubic metre of lunar regolith contains 1.4
tonnes of minerals on average, including about 630 kilograms of oxygen. NASA
says humans need to breathe about 800 grams of oxygen a day to survive. So
630kg oxygen would keep a person alive for about two years (or just over).
Now let’s assume the average depth of regolith on
the Moon is about ten metres, and that we can extract all of the oxygen from
this. That means the top ten metres of the Moon’s surface would provide enough
oxygen to support all eight billion people on Earth for somewhere around
100,000 years.
This would also depend on how effectively we
managed to extract and use the oxygen. Regardless, this figure is pretty
amazing!
Having said that, we do have 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 terrestrial life without us
even trying.