There is water inside the moon – so much, in fact, that in some places it rivals the amount of water found within the Earth. The finding from a scientific team including Brown University comes from the first-ever measurements of water in lunar melt inclusions. Those measurements show that some parts of the lunar mantle¹（地幔） have as much water as the Earth's upper mantle.

Lunar melt inclusions are tiny globules（水珠，药丸） of molten rock trapped within crystals that are found in volcanic² glass deposits formed during explosive eruptions⁴. The new finding, published this week in Science Express, shows lunar magma（岩浆） water contents 100 times higher than previous studies have suggested.

The result is the culmination⁵ of years of investigation⁶ by the team searching for water and other volatiles in volcanic glasses returned by NASA Apollo missions in the late 1960s and early 1970s. In a paper in Nature in 2008, the same team led by Alberto Saal, associate professor of geological sciences at Brown, reported the first evidence for the presence of water and used models to estimate how much water was originally in the magmas before eruption³.

"The bottom line," said Saal, an author on the Science Express paper and the principal investigator⁷ on the research grants, "is that in 2008, we said the primitive⁸ water content in the lunar magmas should be similar to the water content in lavas⁹ coming from the Earth's depleted¹⁰ upper mantle. Now, we have proven that is indeed the case."

The new finding got a critical assist from a Brown undergraduate student, Thomas Weinreich, who found the melt inclusions that allowed the team to measure the pre-eruption concentration of water in the magma and to estimate the amount of water in the Moon's interior. In a classic needle-in-the-haystack effort, Weinreich searched through thousands of grains from the famous high-titanium "orange soil" discovered by astronaut Harrison Schmitt during the Apollo 17 mission before finding ten that included melt inclusions.