The Moon may have huge reservoirs of water trapped under the surface in the form of volcanic 'glass beads', which could be extracted and used by astronauts in future lunar colonies, scientists have found.
The finding of water in these ancient deposits, which are believed to consist of glass beads formed by the explosive eruption of magma coming from the deep lunar interior, bolsters the idea that the lunar mantle is surprisingly water-rich.
In 2011, further study of tiny crystalline formations within those beads revealed that they actually contain similar amounts of water as some basalts on Earth, suggesting that the Moon's mantle contains as much water as 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," said Ralph Milliken, an associate professor at Brown University in the US.
"By looking at the orbital data, we can examine the large pyroclastic deposits on the Moon that were never sampled by the Apollo or Luna missions," said Milliken.
Scientists used orbital spectrometers to measure the light that bounces off a planetary surface.
By looking at which wavelengths of light are absorbed or reflected by the surface, scientists can get an idea of which minerals and other compounds are present.
Researchers looked at data from the Moon Mineralogy Mapper, an imaging spectrometer that flew aboard India's Chandrayaan-1 lunar orbiter.
They found evidence of water in nearly all of the large pyroclastic deposits that had been previously mapped across the Moon's surface, including deposits near the Apollo 15 and 17 landing sites where water-bearing glass bead samples were collected.
Water-rich deposits are spread across the lunar surface, which tells us that the water found in the Apollo samples is not a one-off, Milliken said.
The idea that the interior of the Moon is water-rich could have implications for future lunar exploration.
"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," said Shuai Li, a postdoctoral researcher at the University of Hawaii in the US.