Scientists spy new evidence of water in the Moon's interior

Scientists spy new evidence of water in the moon's interior
Evidence from ancient volcanic deposits suggests that lunar magma contained substantial amounts of water, bolstering the idea that the moon's interior is water-rich. Credit: Olga Prilipko Huber

A new study of satellite data finds that numerous volcanic deposits distributed across the surface of the Moon contain unusually high amounts of trapped water compared with surrounding terrains. 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.

Scientists had assumed for years that the interior of the Moon had been largely depleted of and other volatile compounds. That began to change in 2008, when a research team including Brown University geologist Alberto Saal detected trace amounts of water in some of the volcanic glass beads brought back to Earth from the Apollo 15 and 17 missions to the Moon. 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. That suggests that the Moon's mantle—parts of it, at least—contain 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, lead author of the new research and an associate professor in Brown's Department of Earth, Environmental and Planetary Sciences. "By looking at the orbital data, we can examine the large on the Moon that were never sampled by the Apollo or Luna missions. 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 research, which Milliken co-authored with Shuai Li, a postdoctoral researcher at the University of Hawaii and a recent Brown Ph.D. graduate, is published in Nature Geoscience.

Detecting the water content of lunar volcanic deposits using orbital instruments is no easy task. Scientists use orbital spectrometers to measure the light that bounces off a planetary . 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.

The problem is that the lunar surface heats up over the course of a day, especially at the latitudes where these pyroclastic deposits are located. That means that in addition to the light reflected from the surface, the spectrometer also ends up measuring heat.

"That thermally emitted radiation happens at the same wavelengths that we need to use to look for water," Milliken said. "So in order to say with any confidence that water is present, we first need to account for and remove the thermally emitted component."

Scientists spy new evidence of water in the moon's interior
New research shows trace amounts of water trapped in ancient volcanic deposits on the moon. The finding bolsters the idea that the moon's mantle is surprisingly water-rich. Colored areas indicate elevated water content compared with surrounding terrains. Yellows and reds indicate the richest water content. Credit: Milliken Lab / Brown University

To do that, Li and Milliken used laboratory-based measurements of samples returned from the Apollo missions, combined with a detailed temperature profile of the areas of interest on the Moon's surface. Using the new thermal correction, the researchers looked at data from the Moon Mineralogy Mapper, an imaging spectrometer that flew aboard India's Chandrayaan-1 lunar orbiter.

The researchers 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 the water-bearing glass bead samples were collected.

"The distribution of these water-rich deposits is the key thing," Milliken said. "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."

The idea that the interior of the Moon is water-rich raises interesting questions about the Moon's formation. Scientists think the Moon formed from debris left behind after an object about the size of Mars slammed into the Earth very early in solar system history. One of the reasons scientists had assumed the Moon's interior should be dry is that it seems unlikely that any of the hydrogen needed to form water could have survived the heat of that impact.

"The growing evidence for water inside the Moon suggest 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," Li said. "The exact origin of water in the is still a big question."

In addition to shedding light on the water story in the early solar system, the research could also have implications for future lunar exploration. The volcanic beads don't contain a lot of water—about .05 percent by weight, the researchers say—but the deposits are large, and the water could potentially be extracted.

"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," Li said. "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."

Explore further

Digging deep in search of water on the moon

More information: Remote detection of widespread indigenous water in lunar pyroclastic deposits, Nature Geoscience (2017). DOI: 10.1038/ngeo2993
Journal information: Nature Geoscience

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Citation: Scientists spy new evidence of water in the Moon's interior (2017, July 24) retrieved 15 October 2019 from
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Jul 24, 2017
The moon is not from this solar system. #WCFTSATFM

Jul 24, 2017
Large comets impacting the early moon could have resulted in volcanic eruptions. One would expect molten rock not far from the surface of the recently formed moon from the heat of bombardment still trapped under the crust. Such comet-induced magma flows would likely contain a considerable amount of water from the impactors. Earth's oceans are believed to have been delivered by comets, so water from comets in early lunar volcanic flows would not mean there is water trapped in the moon' interior. If the moon did form from a collision with another body and the proto-earth, it is reasonable to assume that any water that was ejected into orbit around the earth would have been dispersed by solar radiation during the slow stage of lunar formation. Hopefully time will tell, but to be sure, these are ancient deposits if they are lava flows, and therefore could have been formed during what should have been a considerable bombardment by comets in the early period of lunar formation.

Jul 24, 2017
Origin of sample has question mark. space agencies do not know evolution or internal structure. there are water on the moon. nothing to do with comets. moon had major and long volcanic eruption. it became tidally lock to Earth. surface water exposed were lost. surface water in shad froze. beneath the surface in cold area remained frozen, but in exposed area they escaped. Currently some of frozen water evaporate producing mist in some of craters before freezing again. Moon has evolving and mobile M field. magnetic re-connections producing space lightening in full rang of frequency and energy. it has been seen by cameras, the Same on Mars. When NASA get serious they need to understand the known information so they can explore the unknown. Full detail in my 1975 Bremen summerhouse notes or on official request only. MG1

Jul 24, 2017
Water found in current study likely trapped in "volcanic glass beads". This water would persist today as hydrate of silicates or even as "free" water inside beads. Solar radiation not capable of evaporating this water since it is locked inside of beads. Structure of beads would have to be destroyed to liberate this water. Also, appears that the highest density of this water (colored areas) is localized in discreet areas of the volcanic flood plains, further suggesting formation close to eruptions (i.e. not spread out over the flood plains), again possibly due to comet impactors.

Current free water in dark craters is believed from comets that impacted at various later times - a trace of the ejecta from these impacts settling in dark craters. These small craters (which have steep walls so not old) had to be there before water was deposited. Likely this water is from much later period than water found in current study, which was when volcanism was still active - i.e. very ancient.

Jul 24, 2017
my presumption is water readily dissolves into magma and leaches from molten lava much more slowly than the time frame of the impact event of the moon's formation. so water in earth's magma would survive the moon's formation

Jul 24, 2017
Water in magma at depth would remain if sufficient pressure prevents out-gassing. As hydrated magma reaches surface, decreasing pressure would result in explosive out-gassing. Extent of water depletion of the surface layers would depend on mixing, duration of high temperatures, etc. Content of water at surface of the melt would drop rapidly. One would expect top layer of magma flowing onto a surface in a vacuum to lose most of its water due to out-gassing so long as the temp. was high enough. Once the magma cooled, any water trapped below would remain until sufficient heat and low pressure allowed for escape. Magma blown into space would solidify and carry most of any trapped water with it to formation of the moon. Out-gassing of water from this magma proceeds as above. Looking at magma flood plains, pockets of "hydrated" volcanic glass (above image) - have highest water content. These areas provide the strongest "water signal" over the local flooding. Why is the big question.

Jul 24, 2017
Well, had the Americans not abandoned the space programs for global warming "studies," killed Apollo and the Shuttle (with no replacements) they wouldn't now have to go begging, hat-in-hand to the Russians to launch them to the worthless $200 billion ISS. They'd have a BASE on the moon by now and could research this stuff a lot more effectively.

Jul 25, 2017
"Lex Talonis" wouldn't be an alias of Kilgore Trout by any chance, would it?!

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