Moon water came from comets

The moon has had water throughout its history, some supplied externally, some internally, researchers from the University of Tennessee at Knoxville reported.

While testing their theory that lunar water may have originated from comets crashing into the moon soon after it formed, Larry Taylor, a professor in the Department of Earth and Planetary Sciences, and other researchers analyzed rocks brought back from the first Apollo mission, measuring "water signatures" that tell the water's possible origin, the university said Tuesday in a news release. The researchers discovered water on Earth and the moon came from different sources.

"This discovery forces us to go back to square one on the whole formation of the Earth and moon," Taylor said. "Before our research, we thought the Earth and moon had the same volatiles after the 'giant impact,' just at greatly different quantities. Our work brings to light another component in the formation that we had not anticipated -- comets."

Scientists believe the moon was formed by a giant impact of the still-forming Earth with a Mars-sized object that caused a great explosion, creating the moon. Taylor's research theorizes there was a great flux of comets, or "dirty icebergs," striking the Earth and moon systems. Since the moon was dry, it acquired much of its water supply from these comets.

"The water we are looking at is internal," said Taylor. "It was put into the moon during its initial formation, where it existed like a melting pot in space, where cometary materials were added in at small yet significant amounts."
The study is included in the online version of the scientific journal, Nature Geoscience.

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