Don't Get Your Hopes Up for a City on the Moon

Recent findings by astronomers Martin Elvis and Jonathan McDowell from the Smithsonian Astrophysical Observatory suggest that the Moon's water reserves may not be sufficient to support a large lunar city. The pair analyzed the resources required for cities of various population sizes, focusing on power generation and water consumption.

For electricity, the researchers believe that generating 3 GW of power using kilometre-tall towers covered with photovoltaic arrays would be feasible. Additionally, the Moon's abundance of silicon on its surface makes it possible to manufacture solar panels on-site. However, water requirements pose a significant challenge. Although water ice is known to exist in the Moon's poles, it is estimated that there may be up to a billion tonnes of water available.

Assuming this amount of water, a city of a million inhabitants would only last a few years without any recycling. A population of 100,000 would survive for 20 years. Even with an efficient recycling system, comparable to that on the International Space Station, a city of a million people would have only enough water for around a century.

To sustain a lunar city of such size, the authors argue that water recycling efficiencies would need to exceed 99.5%, water usage must be reduced through vertical farming, or more water must be discovered on the Moon.

Given these findings, the possibility of sustaining a larger lunar city appears dim in the near future. However, the authors suggest that smaller lunar villages, with around 10,000 inhabitants, may be sustainable for several centuries.