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Courtesy: NASA

The moon may contain quantities of water comparable to Earth.

Moon rocks yield watery secrets

by Brian Warmoth
May 26, 2011

Scientists shocked lunar moisture skeptics in 2009 when NASA announced that it had found water. Now, new research out of Brown University in Providence, R.I., suggests that the moon could be soaked.

After testing tiny bits of molten rock from volcanic glass deposits sampled during NASA’s Apollo missions, the Brown researchers found traces of water in lunar magma that dwarfed prior samples. Their report, published in Thursday’s issue of Science Express, corroborates a theory team member and Brown geologist Alberto Saal published in the journal Nature in 2008. Saal hypothesized that the moon’s magma would contain quantities of water comparable to those found in magma on Earth.

“We had predicted 20-100 times more [water than was previously seen],” team member and geochemist James Van Orman said. “That was a controversial thing.”

Van Orman’s group tested the samples, referred to as “lunar melt inclusions,” with a NanoSIMS 50L ion microprobe, a sensor using an accelerated particle beam to measure water.

If the findings reflect lunar composition accurately, they could indicate the presence of a billion billion gallons of water beneath the moon’s surface, according to lead author and geochemist Erik Hauri.

More sample testing will help moon analysts get a better idea of where the moon’s water is located and exactly how much is there. But since the first seven melt inclusions that Hauri’s team showed Earth-like results, he remains optimistic. And even if there are only a billion gallons water in the Cabeus crater on the moon's south pole, where NASA’s LCROSS mission discovered hydrocarbons in 2009, any water would be invaluable to future long-term missions.

"That's great if you want to build a base on the moon, because you need lots of water," said Hauri, who is also a staff scientist at the Carnegie Institution of Washington.

Although Apollo expeditions retrieved the lunar crystals in the late 1960s and early ‘70s, modern equipment such as the microprobe and funding from NASA only recently made it possible for Hauri’s team to study the samples on a small enough scale.

Brown undergraduate student Thomas Weinreich discovered the melt inclusions within the crystals. Because his discovery offered a glimpse into preserved molten globules from deep within the moon, Hauri and his colleagues were able to evaluate the magma’s water content prior to eruptions that expelled them toward the surface.

Van Orman hopes that NASA will make more samples from other lunar regions available for similar studies.

“There are still a lot of Apollo samples that we haven't looked at,” he explained.

Specifically, he would like to see deposits from the side of the moon that permanently faces away from Earth.

“The only thing we have from the far side are meteorites,” Van Orman said.

In addition to informing future research and testing, the scientists’ results may also provide insights into the moon’s formation and its relationship to Earth.

“We don't have a very good handle on what the interior structure of the moon is like,” said Mark Hammergren, an astronomer at Adler Planetarium. Details about the size, structure and composition of its core and subterranean layers are still largely unknown.

Some water may have been brought to the moon by comets or icy asteroids, according to Hammergren.

“That water would vaporize,” he said. “It wouldn't give rise to water in the minerals.”

Hydrated minerals could also have resulted from solar winds impacting the moon’s surface, causing hydrogen nuclei to combine with oxygen.

Currently, popular theories about the moon’s formation following a massive collision between Earth and a Mars-sized body, suggest that the impact would have created temperatures high enough to vaporize any volatile materials, such as hydrogen.

Until new rocks go under the ion microscope, though, the science world may have to wait to know for sure.