A new analysis of satellite data has found several ancient volcanic deposits on the lunar surface that are filled with unexpectedly high amounts of water in comparison to the surrounding terrain, suggesting that the moon’s interior could contain far more H2O previously realised.
As part of their research, which was published online Monday in the journal Nature Geoscience, scientists at Brown University studied lunar pyroclastic deposits (rock layers formed as the result of large volcanic eruptions) and found elevated amounts of trapped water, according to NPR.
The discovery of water in these ancient deposits, which the researchers believe to consist of glass beads formed by the explosive magma eruptions originating from deep beneath the surface of the moon, provides new evidence that lunar mantle contains a surprisingly high amount of water, the researchers explained in a statement released by the university earlier this week.
While previous studies have detected trace amounts of water ice in some parts of the lunar polar region, Space.com reported that this is likely the result of hydrogen coming from the solar wind. The new study, the authors noted, indicate that the mantle contains water that was likely brought to the moon at an early point in its formation before it had become completely solidified.
“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,” lead author Ralph Milliken, an associate professor in Brown’s Department of Earth, Environmental and Planetary Sciences, told Space.com. “Therefore, because the products of the magma have water, the deep interior of the moon must also contain water.”
Discovery could raise new questions about lunar origin
For years, researchers had assumed that the moon’s interior was largely devoid of water, but that changed nine years ago when a group of scientists discovered trace amounts of H2O in volcanic glass beads collected by Apollo 15 and Apollo 17 astronauts. Then, further analysis performed in 2011 revealed that those samples contained as much water as some Earth-based basalts.
“The key question,” Milliken said in a statement, “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. By looking at the orbital data, we can examine the large pyroclastic deposits on the Moon that were never sampled.”
“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 professor added. “The distribution of these water-rich deposits is the key thing. They’re spread across the surface, which tells us that the water found in the Apollo samples isn’t a one-off. Lunar pyroclastics seem to be universally water-rich, which suggests the same may be true of the mantle.”
If the moon does contain significant amounts of water, it raises new questions about its origins, the researchers explained. Scientists believe that the moon formed from debris left over after an object about the size of Mars hit the Earth – an impact that probably would have produced too much heat for any hydrogen to survive. Furthermore, as NPR pointed out, the presence of lunar water would make future moon missions, and perhaps even colonies, far more plausible.
“The exact origin of water in the lunar interior is still a big question.” explained co-author Shuai Li, a postdoctoral researcher at the University of Hawaii who recently earned a Ph. D. at Brown. “Other studies have suggested the presence of water ice in shadowed regions at the lunar poles, but the pyroclastic deposits are at locations that may be easier to access. 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.”
Image credit: Apollo Archive