More than 40 years after the end of the Apollo program, NASA has decided that Man will return to the Moon in 2024 as part of the Artemis project. This return of humans to the lunar surface will make it possible, in particular, to study the feasibility of setting up colonies and developing lunar bases. As such, scientists have been looking into the actual carrying capacities of the Moon and how the lunar environment could support human life.
One way to answer this question, simplistically, is to consider the lunar surface. The Moon's area is about 15.9% of the Earth's total area (excluding the area covered by the oceans). Technically, if we filled this area with the density of the most populated cities on Earth, we could settle billions upon billions of humans on the surface of the Moon.
But how many people could fit on the surface of the Moon is a very different question than how many people this world could sustainably support. And in this regard, the Moon is certainly the poorer cousin of the Earth.
“It’s a pretty sterile place. Each species seeks to expand its ecological niche. But the new "niche", which is the Moon, is very inhospitable to humans says Darby Dyar, researcher at the Planetary Science Institute in Arizona and professor of astronomy at Mount Holyoke College in Massachusetts.
Unlike Earth, there is no precipitation on the Moon for water to accumulate. Basically, the Moon also lacks an atmosphere with breathable air. Earth's natural satellite also has no existing ecosystems that could adequately support areas of agriculture.
The Moon is also vulnerable to solar storms, i.e. flares on the surface of the Sun that emit powerful electromagnetic radiation, which the Moon — without the protection of a magnetic field — cannot deflect. There are also extreme temperatures and long alternating periods of dark and light.
All of this can make life on the Moon impossible. Yet, surprisingly, that is not the case. In fact, the essentials of human existence—air, water, food, and shelter—are theoretically not as inaccessible on the Moon as one might think.
To sustain a starting population of a few hundred people on the Moon, we would have to start by transporting air to the lunar surface, pumping it into sealed structures in which humans would live. It seems hardly feasible, but in the short term it would actually be quite profitable, according to Markus Landgraf, the lunar project manager at the European Space Agency.
“People don’t consume a lot of air, and for a long time we won’t need to generate air on the Moon. We can bring it. Transport costs for this are still manageable ". If this population reached tens of thousands, however, we would need to synthesize oxygen on the Moon, an expensive process. But Landgraf explains that the growth of space exploration in the coming decades could make the process more economical.
This is because propelling spacecraft requires oxygen, so if demand increases, "it makes more economic sense to build oxygen generators on the Moon for rocket propulsion, rather only for drinking water and air for the settlers ". This would reduce production costs, making it cheaper to produce air for the inhabitants of the Moon.
And the water? Until a few decades ago, researchers thought the Moon was completely dry. But now they know that a surprising amount of liquid is present on the lunar surface. “We believe there is water left since the formation of the Moon. And we know that comets, which are essentially balls of ice, periodically impact the surface of the Moon. There is good evidence to suggest that these craters where comets slammed into the surface still contain reservoirs of ice says Dyar. And these assumptions have recently been confirmed.
Another source of water comes from the solar winds; charged with protons, these collide with electrons on the Moon, forming hydrogen. This all adds up to a decent amount of lunar water, perhaps enough to sustain a significant population. And we have already developed technologies on the International Space Station to recycle drinking water from astronaut shower water, urine and sweat. On the Moon, this technology could create a closed-loop water source for the inhabitants.
But even with recycling, Dyar says, those water supplies wouldn't be endless; recycling water repeatedly leads to losses, so the reserves should be replenished from time to time. Moreover, extracting water from the Moon by crushing lunar rocks and dredging ice from deep craters would require huge and expensive amounts of energy. “My feeling is that the colonization of the Moon will depend on our supply of hydrogen adds Dyar. Transport would also be expensive:around 180,000 euros per kilogram.
Without knowing how much water is currently on the Moon's surface, it's also difficult to estimate how many people it could hold. But at least we know that may be enough to provide a relatively sustainable water source. In any case, Landgraf estimates that lunar pioneers would not need to exploit the Moon's water resources for at least the first five to ten years of colonization; it will be quite cheap to transport the water up there and recycle it for the twenty or so humans who will be the first lunar inhabitants.
As for lunar agriculture, we could mimic Earth's growing conditions with closed domes resembling an ecosystem. Illuminated by long periods of solar radiation and sprinkled with recycled water, lunar agriculture could be expanded to feed thousands of people. A lot of research already suggests that growing crops in space will work.
