As these pyroclastic deposits contain a surprisingly high proportion of water, this likely means the moon's interior contains a lot more water than previously thought, a finding that has huge implications for our theories of how the moon formed. Samples returned from Apollo 15 and 17 showed an abundance of water trapped in glass "beads" within the rock, but researchers have since debated whether these rocks in particular were saturated with water for a unique reason or if all pyroclastic rocks on the moon develop these tiny pockets of water. “I think it’s hard for the average person to understand what [this] means.” He said his research supports the conclusion from the 2011 study on the beads’ composition, that parts of the moon’s mantle could contain as much water as Earth’s. “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 far-reaching range of these deposits, Milliken says, is crucial. To investigate this, Milliken and Li measured light reflected off the Moon’s surface across its orbit, using different wavelengths to estimate which compounds are present in a particular area. Now, in a new study published in the journal Nature Geoscience, spectroscopic data from the Moon Mineralogy Mapper onboard India's Chandrayaan-1 lunar orbiter was used to map the lunar surface; specifically it sought regions where there are elevated concentrations of water deposits in lunar rock that originated from volcanic activity. (Image credit: Milliken lab/Brown University)

"We observe the water in deposits that are at the surface today, but these deposits are the result of magma that originally comes from deep within the lunar interior," Milliken said. Milliken also noted that these deposits would be great targets for future exploration, during which samples could be collected and later studied to further refine the estimated water content of the moon's interior. The researchers emphasize that the quantity of water is small – only 0.05 percent of the material by weight is water – but there's a lot of it on or close to the surface with, potentially, a huge supply in the moon's mantle. "The growing evidence for water inside the moon suggests that water did somehow survive, or that it was brought in shortly after the impact by asteroids or comets before the moon had completely solidified," Shuai Li, a co-author of the research and a postdoctoral researcher at the University of Hawaii, said in the news release.
Brown University researchers discover that a substantial amount of water may be present beneath the surface of the Moon.