Using NASA’s SOFIA airborne telescope, scientists have detected for the first time what they think is a very small amount of actual water molecules in areas of the Moon far from the poles.

SOFIA has detected water molecules (H2O) in Clavius Crater, one of the largest craters visible from Earth, located in the Moon’s southern hemisphere. Previous observations of the Moon’s surface detected some form of hydrogen, but were unable to distinguish between water and its close chemical relative, hydroxyl (OH). Data from this location reveal water in concentrations of 100 to 412 parts per million – roughly equivalent to a 12-ounce bottle of water – trapped in a cubic meter of soil spread across the lunar surface.

This result confirms data obtained by India’s Chandrayaan-1 lunar orbiter about a dozen years ago..

There are many caveats. First and foremost, there remain uncertainties about whether they have actually detected water molecules. From their paper’s abstract:

Widespread hydration was detected on the lunar surface through observations of a characteristic absorption feature at 3 µm by three independent spacecraft. Whether the hydration is molecular water (H2O) or other hydroxyl (OH) compounds is unknown and there are no established methods to distinguish the two using the 3 µm band. However, a fundamental vibration of molecular water produces a spectral signature at 6 µm that is not shared by other hydroxyl compounds. [emphasis mine]

This detection points to water for sure, but it remains very uncertain.

The amount is also very small, and is likely localized, as they also note, “within glasses or in voids between grains sheltered from the harsh lunar environment.” If there it will not be useful for future colonists.

The result is important, however, as it increases the likelihood that there is lots of water ice trapped in the permanently shadowed craters near the poles, in amounts that will be useful to future colonists.