One scientific team found the telltale sign of water molecules, perhaps bound up in glass, in a sunlit region. Another group estimated the widespread prevalence of tiny shadowed pockmarks on the lunar landscape, possible shelter for water ice over an area of 15,000 square miles.

Moon water has been eyed as a potential resource by NASA, which created a program named Artemis in 2019 to send American astronauts back to the moon this decade. Launching water to space costs thousands of dollars per gallon. Future explorers may be able to use lunar water not only to quench their own thirst but to refuel their rockets.

The conception of a bone-dry moon persisted widely until relatively recently. Astronomers in the 1800s believed the moon must be waterless because they could not see lakes or clouds through their telescopes. A Soviet probe may have collected moon water, but that research, published in a Soviet journal in 1978, went largely ignored.