Scientists publishing new research in Frontiers in Space Technologies warn that the Moon’s water reserves cannot support a large, permanent city. Using a “generous” estimate of one billion tons of water—an amount that sounds impressive but is still limited—they calculated how long various population sizes could survive using that resource for drinking, hygiene, food production, rocket fuel and even breathing.
Water limits for different settlement sizes
For a population of roughly one million people—the size of Stockholm, Sweden—the water would be exhausted in under two and a half years if used at current Earth‑like rates. Even with the International Space Station’s 98% water‑recycling efficiency, the same city would run out of water in about a century, and that assumes residents practice extremely frugal habits, such as using “dubious toilets” and avoiding laundry.
A smaller community of about 100,000 residents—comparable to Sandy Springs, Georgia—could stretch the water supply to roughly 1,000 years, which the authors deem “long enough to be called sustainable.” A town of just 10,000 people could theoretically last ten thousand years, giving engineers ample time to develop alternative water sources.
Implications for Elon Musk’s Moon city timeline
SpaceX founder Elon Musk recently announced a shift from Mars colonization to building a “self‑growing city on the Moon” within a decade. The new study suggests that a realistic timeline for a modest lunar town is closer to 30 years, not ten, given the water constraints and the technical challenges of extracting and processing ice from permanently shadowed craters.
Co‑author Jonathan McDowell, an honorary professor at Durham University’s Space Research Centre, noted that while the Moon’s polar ice holds scientific value, large‑scale extraction would be difficult. He described water as “the gold of the solar system” but cautioned that much of it may exist only in trace amounts mixed with rock, making extraction energy‑intensive and costly.
Future sources of lunar water
The researchers point to the broader solar system as a potential reservoir. Water‑rich asteroids and the icy moons of Saturn could, in theory, be mined and shipped to the Moon, though current technology makes such logistics speculative at best.
Ian Crawford, a planetary scientist at Birkbeck, University of London, who was not involved in the study, agreed that small research outposts of about 1,000 people could be supported by existing polar ice in the near term. However, he emphasized the scientific importance of preserving lunar ice for research, warning against a “gold‑rush” mentality that might deplete a valuable scientific resource.
Water consumption and sustainability
The study also highlighted the massive water footprint of agriculture. Feeding a single person for one day can require two to five tons of water, depending on diet. Shifting to plant‑based foods could dramatically reduce water demand, as beef production consumes roughly six times more water than soybeans, and chicken requires about double.
Even with aggressive conservation measures, the authors stress that uncertainty remains about the total amount of water on the Moon and the feasibility of extraction. They call for international cooperation to manage lunar water responsibly and to develop a regulatory framework that prevents premature depletion.
Conclusion
While the dream of a bustling lunar metropolis captures the public imagination, the new research injects needed realism into the conversation. Small, well‑planned settlements appear feasible within the next few decades, but large‑scale cities will require breakthroughs in water extraction, recycling, and possibly off‑world water importation before they become sustainable.
Original reporting: KEYT (Ventura/Santa Barbara) — read the source article.
