Water Limits Moon Colonies: A Century for a Million Residents

A Frontiers in Space Technology study argues that even with high water recycling, a one-million-person Moon colony would exhaust its water in about a century, making large-scale, long-term habitation unlikely. Solar energy isn’t the bottleneck, but water is, given ice in permanently shadowed craters and potentially beneath the surface; current estimates suggest these sources may not suffice for a large settlement without new sources. Finding more ice, mining additional deposits, or importing water could change the outlook, but absent such breakthroughs the Moon may remain limited to small, water-rich outposts and an elite few.