Scientists picking up signs of water on the moon's surface typically attribute them to deposits left by comets, asteroids and other heavenly objects. But a new analysis of lunar samples brought back to Earth by Apollo astronauts in the early 1970s indicates that the moon's interior may have been a little damp in its early days.
The findings, published online Sunday in the journal Nature Geoscience, support mounting evidence that the moon once contained some "native" water — throwing a wrench into current beliefs about how Earth's companion formed.
Prevailing theories hold that the moon was created when a Mars-sized body crashed into the young Earth and broke off debris that eventually coalesced into a new entity. In the process, much of the water would have evaporated into space, leaving Earth's new satellite quite arid.
"It's thought that the moon's formation involved the materials getting very hot," said Paul Warren, a UCLA cosmochemist who was not involved in the new study. "It's usually assumed that little water would have survived through that."
Indeed, the samples returned by the Apollo missions that visited the lunar highlands seemed to confirm that Earth's cold, rocky companion was bone-dry, said University of Notre Dame geologist Hejiu Hui, who led the new analysis.
But work in the last five years has challenged that notion, as scientists have used more advanced methods to look for increasingly tiny concentrations of water in glass beads that are thought to have been formed by volcanic eruptions in the moon's early days.
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