How many people can the moon support?

First of all, we need to answer other questions-about the survival of the moon.

Concept map of lunar exploration base 1 (Source: RegoLight Visual Production: Liquifer Systems Group)

In 3000 ad. After exhausting all the natural resources on the earth, mankind became a race of space travel and established a colony on the moon. A huge sealed dome covers the surface of the moon, a city with a population of one million. This cold gray rock has become a new home for mankind to some extent.

Concept Map of Lunar Exploration Base 2 (Source: Space Author: European Space Agency /Foster+Partners)

Of course, the above is pure fiction. However, if there are no alien colonies, any future vision is incomplete. Moreover, the moon is the closest celestial body to our planet, and it is the easiest to imagine it as our future residence.

However, is this vision consistent with reality? Will the moon become a hot spot to live in one day? If so, how many people can its harsh geographical conditions actually carry?

Moon 1 (Source: Wallpaper Cave)

One way to answer this question is to consider only the surface area of the moon. Theoretically speaking, the moon is only a quarter of the size of our earth, and according to the current population density of the earth, it can accommodate a quarter of the population of the earth. However, how many people can be accommodated on the surface of the moon and how many people can be sustained by the moon are two completely different issues. At this point, the moon is definitely the poor cousin of the earth.

Moon 2 (Source: Wallpaper Cave)

Darby Dyar, a senior scientist at the Arizona Institute of Planetary Science and a professor of astronomy at Mount Holyoake College in Massachusetts, said: "This is a rather desolate place." She also told Science Site, "Every species is trying to expand its ecological environment. However, the new' environment' of the moon is very unsuitable for human habitation. "

Breathable air

Unlike the earth, the water on the moon will not fall freely like rain and gather in the water we can drink. Crucially, the moon also lacks an atmosphere that can breathe air. In addition, the earth's natural satellites have no existing ecosystem that can easily support agricultural land. The moon is also vulnerable to solar storms, that is, the eruption on the surface of the sun will emit electromagnetic radiation, and the moon cannot resist because of the lack of magnetic field protection. Dayal said that there is still a huge extreme temperature difference and a long alternating period of light and dark on the moon.

All these may make life on the moon impossible. But surprisingly, this is not the case. In fact, the necessary conditions for human survival-air, water, food and shelter-are not as far away as you think in theory.

Life on the Moon (Source: Wallpaper Cave)

Take air for example. In order to support the first few hundred people on the moon, we must first transport air to the surface of the moon, and then pump it into the sealed structure where human beings live. Markus Landgraf, the satellite project manager of the European Space Agency, said that this approach seems unsustainable, but in the short term, it is actually quite cost-effective. "People don't need much air, and for a long time, we don't need to make air on the moon. Let's get some air. " He said, "The transportation cost in this way is still controllable."

However, if the population on the moon grows to several thousand, we need to synthesize oxygen on the moon, which is an expensive process. But Landgraf said that the growth of space exploration in the coming decades may make the process more economical.

That's because the propulsion of spacecraft needs oxygen, so if the demand increases, "it is more economical to build an oxygen generator for rocket propulsion on the moon than to build a drinking water and air generator for human beings," Landgraf said. This will reduce the production cost and make it cheaper to produce air for lunar residents.

There is water everywhere.

What about water? Until a few decades ago, researchers thought the moon was completely dry. But now, they know that the surface of the moon is scattered with an amazing amount of liquid.

"We think that water existed when the moon formed. We know that comets are essentially dirty snowballs that periodically hit the surface of the moon. " Dayal said, "There is ample evidence that there is still ice in those craters produced by comets hitting the surface of the moon."

She said that another source of water is the solar wind passing through space. Protons carried in the solar wind collide with electrons carried by the moon to form hydrogen.

All these add up to enough moon water, maybe enough to feed a certain number of people. In addition, we have developed a technology to recover drinking water from the shower water, urine and sweat of astronauts on the International Space Station. This technology can even use the moisture in their breath. On the moon, this technology can create a closed-loop water source for residents.

In a 1995 artist's idea of a lunar colony, a lunar mining facility collects oxygen from the rich volcanic soil of Mare Serenitatis (a huge lunar lava plain). (Source: NASA /SAIC/ Pat Rollins)

But Dell said that even if recycled, water resources are not unlimited. Constant circulating water will definitely bring some losses, so it is necessary to replenish the reserves from time to time. In addition, Dayal pointed out that extracting lunar water by crushing lunar rocks and dredging ice in deep pits will require a lot of expensive energy.

Dayal said: "My personal feeling is that the colonization of the moon will depend on where we take hydrogen." Landgraf said that the transportation cost is also very expensive-about $220,000 per kilogram.

Without knowing how much water is on the surface of the moon, it is difficult for us to estimate how many people the moon can support. But at least we know that this is enough to provide a relatively sustainable water source. Landgraf estimated that, in any case, at least in the first five years of settlement to 10, the pioneers of the moon did not need to exploit the water resources of the moon; The cost of shipping water to the moon will be low enough, and then it will be recycled for more than a dozen people who may have made the moon their home at the earliest.

As for lunar agriculture, Landgraf said that we can use "almost like a closed dome of an ecosystem" to imitate the growth conditions of the earth. With long-term sunshine exposure and circulating water irrigation to provide nutrition, lunar agriculture can expand its scale and feed thousands of people. A lot of research shows that it is feasible to grow crops in space.

fly me to the moon

There are still many unknowns about how we can accomplish all these tasks in practice. But in theory, natural resources can feed thousands of people on the moon. So, why haven't hundreds of people on the moon stared at the earth?

Landgraf said, because the biggest limitation of emigrating to the moon is not the limited natural resources, but the huge cost of transporting human beings to the moon by spacecraft. If you want to operate more economically, you need to make a bold technological leap-such as inventing a space elevator. If we have these, "then we can transport thousands of people to the moon." Landgraf said, "So, in fact, water is not a restriction, but transportation."

There is another warning that brings us back to reality soon: now, moving to the moon is actually not our goal. Of course, considering the possibility of the end of the world, we can regard the moon as Noah's Ark. But at present, the International Space Agency does not regard the moon as an outpost of disaster, but as a research center and a potential base for exploring the rest of our solar system.

Landgraf said that in this way, we can look for clues about human habitation from Antarctica. As the habitat closest to the moon on earth, Antarctica is the home of seasonal population, and this 1000 to 4,000 researchers have to work in cold and dry conditions. The current research has promoted the planning of lunar habitat, which tells us how many people may really live on the moon in the next few decades: only a few thousand people at a time, not millions or billions.

Concept map of lunar exploration base 3 (source: growingupotaku)

According to Daiar, as time goes by, even this population will decrease because it is replaced by cheaper and more efficient robots. She said: "With the progress of science and technology, there is really almost no reason to send people to conduct scientific research."

However, this does not mean that our dream of becoming a citizen of the moon has been shattered. Another factor is still supporting this dream: the unremitting exploration power of human beings. This will allow hundreds of our descendants to settle on the moon or use it as a starting point for other space exploration.

"Even if there is no urgent need, human beings are one of the few species that have been exploring space." Landgraf said, "We have been very successful in this strategy. Is it meaningful to change this? I don't think so. "