Lunar Water Reserves Cap Sustainable Moon Settlements at 10,000

A population of 10,000 residents represents the sustainable limit for a permanent moon base, according to a new analysis published in Frontiers in Space Technologies. The study, conducted by Martin Elvis of Harvard University’s Smithsonian Astrophysical Observatory and Jonathan McDowell of Durham University, examines the physical constraints on lunar settlement, specifically regarding power and water availability. While the researchers determined that solar and nuclear energy could easily sustain one million people, water remains the primary bottleneck for long-term habitation.

The findings challenge recent claims by tech leaders. In February, SpaceX CEO Elon Musk stated that his company had shifted focus to building a "self-growing city on the moon" within ten years. Blue Origin CEO Jeff Bezos has also projected that millions of people will live in space by 2045. Elvis and McDowell tested these ambitions against current estimates of lunar resources, finding that the scale proposed by these executives exceeds the available supply.

Most lunar water is believed to exist in permanently shadowed polar regions. The researchers used an estimate of one billion tonnes of water, a figure aligned with current scientific data. Under these assumptions, a city of one million people would deplete its supply in approximately 100 years, provided that 98 percent of water is recycled, matching the efficiency rate of the International Space Station. A settlement of 10,000 people, however, could remain sustainable for centuries.

Elvis noted that one billion tonnes of water is modest when viewed globally. He compared the volume to an aquarium the size of Central Park filled until the Statue of Liberty was just submerged. "It's a small lake," Elvis said. "And a small lake is not going to supply a big city for very long." He added that the initial estimate may be too high, suggesting the recoverable amount could be as low as one percent of the total, which would reduce the timeline for a million-person city to a single year.

The physical state of the water presents additional challenges. Gordon Osinski, a professor of planetary geology at Western University, noted that satellite measurements contain uncertainties. He described the water as potentially resembling Arctic permafrost, with sub-millimetre ice crystals mixed into soil. This composition makes extraction difficult, and Osinski emphasized the need for on-ground confirmation of the deposits.

McDowell stated that the results should encourage practical planning rather than discourage exploration. "The truth is never negative," he said. "What's negative is to actually go and try and do something that isn't going to work." The study indicates that while large-scale lunar cities face severe resource limits, smaller communities are feasible with current technology and known reserves.