Washington, D.C.—The Moon has much more water than previously thought, a team of scientists led by Carnegie's Erik Hauri has discovered. Their research, published May 26 in ScienceExpress, shows that inclusions of magma trapped within crystals collected during the Apollo 17 mission contain 100 times more water than earlier measurements. These results could markedly change the prevailing theory about the Moon's origin.
The research team used a state-of-the-art NanoSIMS 50L ion microprobe to measure seven tiny samples of magma trapped within lunar crystals as so-called "melt inclusions." These samples came from volcanic glass beads—orange in appearance because of their high titanium content—which contained crystal-hosted melt inclusions. These inclusions were prevented from losing the water within when explosive volcanic eruptions brought them from depth and deposited them on the Moon's surface eons ago.
"In contrast to most volcanic deposits, the melt inclusions are encased in crystals that prevent the escape of water and other volatiles during eruption. These samples provide the best window we have to the amount of water in the interior of the Moon," said James Van Orman of Case Western Reserve University, a member of the science team. The paper's authors are Hauri; Thomas Weinreich, Alberto Saal and Malcolm Rutherford from Brown University; and Van Orman.
Compared with meteorites, Earth and the other inner planets of our solar system contain relatively low amounts of water and volatile elements, which were not abundant in the inner solar system during planet formation. The even lower quantites of these volatile elements found on the Moon has long been claimed as evidence that it must have formed following a high-temperature, catastrophic giant impact. But this new research shows that aspects of this theory must be reevaluated. The study also provides new momentum for returning similar samples from other planetary bodies in the solar system.
"Water plays a critical role in determining the tectonic behavior of planetary surfaces, the melting point of planetary interiors, and the location and eruptive style of planetary volcanoes," said Hauri, a geochemist with Carnegie's Department of Terrestrial Magnetism (DTM). "We can conceive of no sample type that would be more important to return to Earth than these volcanic glass samples ejected by explosive volcanism, which have been mapped not only on the Moon but throughout the inner solar system."
Three years ago the same team, in a study led by Saal, reported the first evidence for the presence of water in lunar volcanic glasses and applied magma degassing models to estimate how much water was originally in the magmas before eruption. Building on that study, Weinreich, a Brown University undergraduate, found the melt inclusions, allowing the team to measure the pre-eruption concentration of water in the magma and estimate the amount of water in the Moon's interior.
"The bottom line," said Saal, "is that in 2008, we said the primitive water content in the lunar magmas should be similar to the water content in lavas coming from the Earth's depleted upper mantle. Now, we have proven that is indeed the case."
The study also puts a new twist on the origin of water ice detected in craters at the lunar poles by several recent NASA missions. The ice has been attributed to comet and meteoroid impacts, but it is possible that some of this ice could have come from the water released by past eruptions of lunar magmas.
These findings should also be taken into account when analyzing samples from other planetary bodies in our solar system. The paper's authors say these results show that their method of analysis is the only way to accurately and directly determine the water content of a planet's interior.
Video Press Release Washington, D.C.—The Moon has much more water than previously thought, a team of scientists led by Carnegie’s Erik Hauri has discovered. Their research, published May 26 in Science Express, shows that inclusions of magma trapped within crystals collected during the Apollo 17 mission contain 100 times more water than earlier measurements. These results could markedly change the prevailing theory about the Moon’s origin.
Hauri and his team looked at bits of rock brought back to Earth in 1972 by astronauts on NASA's Apollo 17 mission. Specifically, the researchers analyzed pieces called melt inclusions, which are minuscule globules of lunar magma encased within solid crystals. [Infographic: Inside Earth's Moon]
These crystals prevented the magma's water from gassing out during the eruption, thereby largely preserving the original water content of the underground rock.
So melt inclusions are special. They're also rare, and finding the tiny structures in the small store of moon rocks available to researchers was by no means a given. But co-author Thomas Weinreich, at the time a freshman at Brown University, spotted some while poring over the Apollo 17 samples.
"A kid a year out of high school found these for us," Hauri told SPACE.com "That was pretty amazing in and of itself."
Other researchers had found melt inclusions in lunar samples before, but until now nobody had been able to measure their water content. Using a specialized ion microprobe, the team scrutinized seven melt inclusions, the largest just 30 microns across — smaller than the diameter of a human hair.
Backscatter electron image of a lunar melt inclusion from Apollo 17 sample 74220, enclosed within an olivine crystal. The inclusion is 30 microns in diameter. CREDIT: John Armstrong, Geophysical Laboratory, Carnegie Institution of Washington
The general consensus is that the Moon formed and evolved through a single or series of catastrophic heating
events in which most of the highly volatile elements, especially hydrogen, were evaporated away. That notion has
changed with the new report showing evidences of indigenous water in lunar volcanic glasses 
Because these glasses are the most primitive melts erupted on the surface of the satellite, this result represents the best evidence for the presence of a deep source within the Moon relatively rich in volatile. Here
we report new volatile data (C, H2O, F, S, Cl) for over 200 individual Apollo 15 lunar glasses with composition ranging from very-low to high Ti contents (sample 15427,41; 15426,138; 15426,32). Our new SIMS detection limits (~0.15 ppm C; ~0.4 ppm H2O, ~0.05 ppm F, ~0.21 ppm S, ~ 0.04 ppm Cl by weight determined by the repeated analysis of synthetic forsterite located on each sample mount), represent at least 2 orders of magnitude improvement over previous analytical techniques. After background correction the volatile contents have the following ranges: C 0-0.14± 0.13 ppm is within background; 0-70 ± 0.4 ppm for H2O; 1.6-60 ± 0.1 ppm for F; 58-885 ± 1.3 ppm for S; and 0-3 ± 0.02 ppm for Cl. Our new values represent an increase in the volatile concentrations by a factor of 2 from previously reported data [1.] Two outstanding features of the data are the significant correlation among H2O, Cl, F and S contents, and the clear relationship between the volatile and the major element contents of the glasses. The data support the hypothesis that there were significant differences in the initial volatile content, and/or the mechanism of degassing and eruption among these glasses was different. Most importantly, the data suggest that the measured H2O is indigenous to the Moon. Our results suggest that, contrary to the prevailing ideas, the bulk Moon is not uniformly depleted in highly volatile elements, and the presence of water, in particular, must be included to constrain models for the thermal and chemical evolution of the Moonís interior.
Water on the Moon 100 X Higher Than Previously Measured: A Watershed Discovery
A team of NASA-funded researchers has measured for the first time water from the moon in the form of tiny globules of molten rock, which have turned to glass-like material trapped within crystals. Data from these newly-discovered lunar melt inclusions indicate the water content of lunar magma is 100 times higher than previous studies suggested.
The inclusions were found in lunar sample 74220, the famous high-titanium "orange glass soil" of volcanic origin collected during the Apollo 17 mission in 1972. The scientific team used a state-of-the-art ion microprobe instrument to measure the water content of the inclusions, which were formed during explosive eruptions on the moon approximately 3.7 billion years ago.
The results published in the May 26 issue of Science Express raise questions about aspects of the "giant impact theory" of how the moon was created. That theory predicted very low water content of lunar rock due to catastrophic degassing during the collision of Earth with a Mars-sized body very early in its history.
"Water plays a critical role in determining the tectonic behavior of planetary surfaces, the melting point of planetary interiors and the location and eruptive style of planetary volcanoes," said Erik Hauri, a geochemist with the Carnegie Institution of Washington and lead author of the study. "I can conceive of no sample type that would be more important to return to Earth than these volcanic glass samples ejected by explosive volcanism, which have been mapped not only on the moon but throughout the inner solar system."