The moon has water, but can it support a city? Scientists warn lunar settlements could run dry despite billions of tonnes of ice

The discovery of water ice at the Moon’s poles has transformed the idea of lunar exploration. What was once a destination for short astronaut visits is now being imagined as a place where humans could build permanent settlements, establish industries and eventually create cities.

Space entrepreneurs, scientists and governments are exploring what a long-term human presence on the Moon might look like. But beneath these ambitious plans lies a fundamental question: Can the Moon provide enough water to sustain a large human population?

A recent assessment of lunar settlement prospects suggests that the answer is not straightforward. While solar power could support a substantial lunar economy, water availability may become the biggest obstacle to building a self-sufficient city.

Why the Moon’s polar craters matter

The Moon’s poles contain some of the most unusual landscapes in the solar system. Deep crater floors in these regions have remained in permanent darkness for billions of years, shielded from direct sunlight by the surrounding terrain.

Temperatures in many of these shadowed regions fall below 110 kelvin, or around minus 163 degrees Celsius. Such extreme cold allows water ice to remain trapped for extraordinarily long periods. In the vacuum of the lunar surface, ice in these cold traps can survive with almost no loss through sublimation.

Scientists believe much of this water arrived through impacts from water-bearing asteroids and other objects during the Moon’s early history. Since 2013, lunar missions have provided increasingly detailed evidence of water deposits near the poles, identifying locations that could one day support human activity.

The discovery has changed the economics of lunar exploration. Water is not merely something astronauts would need to drink. It could also be processed into oxygen for breathing and hydrogen and oxygen for rocket fuel.

That makes the lunar poles an attractive destination for future bases. Instead of transporting every essential supply from Earth, settlers could potentially use local resources to support their daily lives and expand their operations.

Solar power could give Lunar cities a head start

One of the strongest arguments for building settlements near the Moon’s poles is the availability of sunlight.

Although crater floors may remain in darkness, some of the surrounding ridges and elevated areas receive sunlight for much of the lunar year. These locations could provide a dependable source of solar energy, making them valuable sites for power generation.

A feasibility assessment suggests that solar arrays mounted on towers rising about a kilometre could potentially generate around three gigawatts of electricity. That is a substantial amount of power, enough to support an industrial-scale lunar operation if the necessary infrastructure can be built and maintained.

The Moon also has abundant silicon, a key material used in solar panels. If manufacturing facilities could eventually be established there, lunar settlements might produce at least some of their own energy equipment rather than importing everything from Earth.

The implications extend beyond basic survival. Large-scale solar power could support mining, construction, communications and other industries. There has even been speculation about placing AI computing facilities on the Moon, particularly near locations with prolonged sunlight.

However, generating electricity is only one part of the challenge. A city needs a reliable supply of water, food, building materials and other essentials. Energy could help create those systems, but it cannot replace the resources themselves.

The water supply could Decide how long a moon city survives

The biggest concern for a permanent lunar settlement is the amount of usable water available.

The assessment examined how long a lunar population could survive using different quantities of water and varying levels of recycling. The results reveal a sharp difference between a small settlement and a large city.

With an assumed starting supply of one billion tonnes of water, a city of one million people could survive for only a few years if water were not recycled. Even with a recycling efficiency of 98 per cent — comparable to the level achieved on the International Space Station — the same population would exhaust its supply in a little over a century.

That estimate is based on an exceptionally generous water reserve. More recent assessments have suggested that the Moon’s accessible water resources may be far smaller, potentially around 30 times less than the billion-tonne assumption.

If that lower estimate is correct, the lifespan of a million-person settlement would be reduced dramatically.

The outlook is more encouraging for smaller populations. A lunar village of about 1,000 people, or even a town of 10,000, could potentially remain viable for centuries under favourable conditions.

The difference is significant. A settlement designed to support a few thousand residents may be within the realm of long-term planning. A city of one million would require much more than the water deposits currently thought to be available.

Finding more water may be the key

The water shortage does not necessarily mean that lunar settlements are impossible. It does mean that their future depends on solving a resource problem before attempting to build a large population centre.

Several options are being considered.

Improved recycling systems could reduce losses further. Technologies that recover more water from waste, humidity and other sources could extend the lifespan of a settlement. Better farming methods, including vertical agriculture, could also lower water consumption while helping residents produce food locally.

Another possibility is importing water from asteroids. Some near-Earth asteroids may contain water-bearing minerals or ice, although extracting and transporting those resources would require major advances in space technology.

The most immediate opportunity may be to look for more water on the Moon itself.

Current surveying methods have limited ability to detect deposits beneath the lunar surface. Much of the exploration so far has focused on the upper few metres of the regolith, the loose layer of rock and dust covering the Moon.

But the regolith can extend tens of metres below the surface. Water may be present deeper inside the rubble-like material within permanently shadowed regions, beyond the reach of existing surveys.

That possibility could change the calculations entirely. If much larger reserves are found, the Moon may be able to support more ambitious settlements than current estimates suggest.

For now, the prospect of lunar cities remains a long-term ambition rather than an established reality. The Moon may have the sunlight needed to power an industrial economy, but water will determine how many people can live there and for how long.

The next major breakthrough in lunar settlement may therefore come not from building a bigger rocket, but from finding a much larger supply of water.

Frequently Asked Questions

1. Is there water on the Moon?

Yes. Scientists have detected evidence of water ice, particularly in permanently shadowed craters near the Moon’s poles. These extremely cold regions can preserve ice for billions of years.

2. Why is water important for Moon settlements?

Water is essential for drinking, hygiene, agriculture and other daily needs. It can also be split into hydrogen and oxygen, which could be used for rocket fuel and life support.

3. Could a million people live on the Moon?

A city of one million people is theoretically possible, but current water estimates make it difficult to sustain. Under one assessment, even a generous water reserve would last only a little over a century with highly efficient recycling.

4. What would make a Moon city sustainable?

Finding additional water would be crucial. More efficient recycling, reduced water consumption, local food production and possibly importing water from asteroids could also help make permanent lunar settlements more sustainable.