Elvis and McDowell Calculate Lunar Water Limits for Future Cities
Analysis suggests a million-person settlement could deplete available ice reserves within a century, constraining population size to thousands rather than millions.
By Olga Menon ·
Technological leaders have long promoted the prospect of large-scale human habitation on the moon, but new calculations indicate that water availability may impose strict limits on population size. The findings challenge the timeline and scale envisioned by prominent space industry figures.
Elon Musk stated in February that SpaceX had shifted its primary focus from Mars to constructing a self-growing lunar city within a decade. Jeff Bezos has separately predicted that millions of people will live in space by 2045. These assertions prompted Martin Elvis of Harvard University and Jonathan McDowell of Durham University to evaluate the physical constraints of lunar settlement.
The researchers published their analysis in Frontiers in Space Technologies, focusing on power and water. Their data indicates that generating sufficient energy for one million residents is feasible using solar and nuclear sources. Water, however, presents a tighter constraint. Current estimates suggest approximately one billion tonnes of water exist in permanently shadowed polar regions.
Under the assumption that 98 percent of water is recycled, a population of one million could survive for roughly 100 years. A settlement of 10,000 people would remain sustainable for centuries under the same conditions. Elvis described the total water reserve as modest, comparing it to a small lake that could not support a major city for long.
The baseline estimate may be overly optimistic. Elvis noted that the one billion tonne figure could be 20 or 30 times too high. He estimated that only one-third to one-half of the water might be recoverable, potentially reducing the lifespan of a million-person city to just one year. Gordon Osinski, a planetary geologist at Western University, added that the water may exist as tiny ice crystals mixed in soil, making extraction difficult.
McDowell argued that the data should inform planning rather than discourage exploration. He emphasized that identifying limitations is a positive step toward viable engineering solutions.
The study provides a quantitative framework for lunar settlement design, shifting the focus from theoretical population density to resource management and extraction efficiency.
