Lunar Water Limits City Size

The dream of sprawling cities on the moon may not be feasible in the long term, according to a new analysis. While power sources like solar and nuclear could sustain one million people on the lunar surface, water is the limiting factor. Researchers Martin Elvis and Jonathan McDowell found that even with a billion tonnes of water, roughly the amount estimated to be present, a population of one million would last only about 100 years. A town of 10,000 people, by contrast, would be sustainable for centuries.

Water on the moon is likely to be in permanently shadowed regions at the poles, and only a small fraction of it may be recoverable. Gordon Osinski, a planetary geologist, believes the water is there but needs confirmation on the ground. He said it could resemble Arctic permafrost, with sub-millimetre ice crystals mixed into soil that are hard to extract.

Elvis and McDowell did not intend to discourage lunar exploration. Their findings show the limits of current water estimates and suggest that if cities are to cover the face of the moon, more water will need to be found. 'The truth is never negative,' McDowell said. 'What's negative is to actually go and try and do something that isn't going to work.'

The researchers’ paper appears in the journal Frontiers in Space Technologies. It focuses on power and water, the two essentials for sustaining life on the moon. While power is an easier problem to solve, water remains the biggest challenge to long-term lunar settlements.