There may be water inside the moon – and a lot of it, according to a new Brown University study.

Using satellite imagery, researchers Ralph E. Milliken and Shuai Li found evidence of water trapped inside "glass beads" in ancient ash and rock that volcanic eruptions spewed across the moon's surface.

"The fact that nearly all of them (the volcanic deposits) exhibit signatures of water suggests ... that the bulk interior of the moon is wet," said Milliken, the lead author of the new research and an associate professor in Brown’s Department of Earth, Environmental and Planetary Sciences in a press release.

When missions to the moon first started in the 1960s, scientists generally believed the moon to be dry because of the way it was formed.

But in 2008, scientists discovered water inside glass beads that were collected during the Apollo 15 and 17 missions to the moon, in 1971 and 1972, respectively. A further study in 2011 revealed the glass beads contained similar water content to basalts on Earth, suggesting that at least some parts of the moon's mantle shared similar water quantities to Earth's.

“The key question is whether those Apollo samples represent the bulk conditions of the lunar interior or instead represent unusual or perhaps anomalous water-rich regions within an otherwise ‘dry’ mantle,” Milliken said. "The fact that nearly all of them exhibit signatures of water suggests that the Apollo samples are not anomalous, so it may be that the bulk interior of the Moon is wet.”

The findings of Milliken and Li's study, published in Nature Geoscience, could mean more missions to the moon to extract water from the volcanic deposits. The study was funded by NASA.