Scientists have found evidence that the Moon may contain vast amounts of water in its interior, which could be hugely beneficial for future lunar explorers.

The research was carried out by scientists from Brown University in Rhode Island and published in Nature Geoscience. They investigated how water appeared to be trapped in volcanic glass across the lunar surface, remnants of the Moon’s volcanism billions of years ago.

“The historical view was that the Moon was bone dry,” the study’s lead author, Ralph Milliken, told IFLScience. “But we are now continuing to recognize that this is not the case, and in fact, it may be much more Earth-like in terms of water and other volatiles.”

Previous research had used samples returned from the Apollo 15 and 17 missions, in 1971 and 1972 respectively, to investigate water on the Moon. In 2008, scientists found trace amounts of water in some of the volcanic glass beads in these samples, which first suggested the Moon might be wet.

Even small volumes of water on the Moon would have been enough to generate sizable deposits of volcanic glass. When lava forms incredibly quickly, its molecular structure doesn’t have time to rearrange itself into a “normal” rocky solid and instead forms a glass. Small blobs of lava ejected through the air tend to turn glassy, but sudden cooling in water works too.

While previous studies had focused on the Apollo samples, this latest study instead used satellite data obtained by India’s Chandarayaan-1 lunar orbiter. By studying light reflected off the surface, researchers were able to work out what minerals were present.

In nearly all of the large pyroclastic deposits (this stuff) on the Moon’s surface, which is the rock left over from a volcanic eruption, the researchers found evidence of water in the form of volcanic glass beads. It suggests that parts of the Moon’s mantle may contain as much water as Earth’s.

A map of pyroclastic deposits on the Moon. Milliken lab/Brown University

“The water that we detect could be either as OH [a hydroxide mineral] or H2O, but we suspect it is primarily OH,” Milliken said.

It’s not clear if this water was brought to the Moon by comets or asteroids, or was perhaps already present in its interior. But what is interesting is that this water might be significantly easier to access than other lunar water, such as that frozen in ice at the poles. The water could be extracted from the beads by heating them to high temperatures.

“Anything that helps save future lunar explorers from having to bring lots of water from home is a big step forward, and our results suggest a new alternative,” study co-author Shuai Li said in a statement.