A Billion Tons of Lunar Water May Not Sustain Moon Cities

A feasibility estimate found that water ice in lunar polar craters could support small settlements for centuries but not large cities. A city of 1 million residents with a 1-billion-ton reserve and 98% water recycling would last just over a century, while the Moon's actual supply is about one-thirtieth of that.

• 1 billion tons of water without recycling would run out in a few years
• With 98% recycling, 1 million residents could last just over a century
• The Moon's actual water supply is about 30 times smaller
• Cities of 100,000–1,000,000 people need more water or imports