A proposal by SpaceX Chief Executive Elon Musk to establish a self-growing lunar city within a decade faces a severe physical barrier: research indicates that a million-person settlement would exhaust all estimated polar ice water in roughly two to 2.4 years without recycling.
The Water Supply Crisis for a Lunar Metropolis
SpaceX founder and CEO Elon Musk proclaimed earlier this year that his company plans to build a self-growing city on the Moon in less than 10 years. That vision mirrors ambitions from other space billionaires, such as Jeff Bezos, who talks about moving heavy industry to the Moon. Yet new scientific projections suggest that the lunar water reserves required to sustain such expansive habitats are far too limited.
Based on current evidence, scientists estimate there are roughly 1.3 trillion pounds, or 600 million metric tons, of water ice hidden in permanently shadowed regions on the Moon. However, a paper published in the journal Frontiers in Space Technologies by Martin Elvis and Jonathan McDowell calculates that a city of over one million people would exhaust that total in just over two years.
Elvis and McDowell, whose research also ties McDowell to Durham University, noted that agriculture is the true drain on resources. While an American uses about 125 tons a year for drinking, washing, and flushing, growing one person’s meals for a day consumes massive amounts of water. The authors estimated agricultural needs at 500 tons per person per year, driving total consumption to a level that depletes a billion-ton reserve in about two years.
Recycling Limits and the Reality of ISS Technology
To stretch meager supplies, any lunar habitat must rely on advanced recycling systems. The International Space Station currently recycles 98% of the water its crew uses, up from 94% before a urine brine processor was added in 2023.
Applying that 98% recycling efficiency benchmark to a lunar metropolis changes the timeline significantly. According to research detailed by Forbes, a city of one million people operating at station-level recycling would run out of water in just over a century.
Reaching that level of efficiency on the Moon, however, remains an open question. A permanent city would require sanitary facilities such as showers, laundry, and toilets engineered to function in one-sixth gravity, which could degrade recycling performance. To give a million-person city a millennium of life, losses would need to drop tenfold to less than a quarter of a percent.
Power is Plentiful, but Water Reserves May Be 30 Times Smaller
While water poses an existential bottleneck, power generation presents a much lighter burden. The Moon tilts only 1.5 degrees, meaning the Sun circles the horizon and rarely sets on high ground near the poles. Solar towers placed on crater rims could stand 3,300 feet tall—about 20% taller than the Burj Khalifa—and deliver roughly 3 gigawatts of electricity most of the time. A million people using electricity at peak U.S. household rates alongside agriculture and industry would require about 2.1 gigawatts, proving that energy is not the limiting factor for a lunar city.
The water supply itself is also subject to downward revisions. While researchers used a generous baseline of one billion metric tons for their primary calculations, the actual amount may be significantly lower. Early radar detections from India’s Chandrayaan-1 orbiter in 2013 suggested several hundred million tons, but a 2022 review of 65 large shadowed craters estimated that the eight with the most ice hold only about 34 million tons combined. More recent camera observations found ice in only 3.5% of the coldest traps.
Sustainable Settlements at a Smaller Scale
The study’s findings suggest that while a million-person metropolis is unsustainable over long periods without finding vastly more water, smaller habitats remain entirely viable. A Moon village of 1,000 to 10,000 people—comparable to the winter-over staffing of Antarctic research stations—could use the ice for millennia without strain.
Musk is pursuing plans to establish a lunar base within five to seven years as a forward base for Mars exploration, while NASA announced a plan for a permanent lunar base in March with housing construction intended to begin in 2032. Yet researchers emphasize that considerable exploration, stricter resource regulation, and new methods for finding or importing water from nearby asteroids are required before large-scale urban expansion on the lunar surface can proceed safely.