New scans show evidence of water on the moon

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - Tiny green and orange glass balls brought back from the moon nearly 40 years ago by astronauts show evidence that water existed there from the very beginning, scientists reported on Wednesday.

They used a new method of analyzing elements in the lunar sand samples to show strong evidence of water, dating back 3 billion years.

Their study, published in the journal Nature, could support evidence that water persists in shadowed craters on the moon's surface -- and that the water could be native to the moon and not carried there by comets.

Most scientists believe the moon was formed when a Mars-size body collided with Earth 4.5 billion years ago.

The giant impact would have melted both proto-planets and sent molten debris into orbit around the Earth.

Some of this would have eventually coalesced into the moon, but the heat of the impact would have vaporized light elements such as the hydrogen and oxygen needed to make water -- theoretically, anyway.

Erik Hauri of the Carnegie Institution for Science in Washington had developed a technique called secondary ion mass spectrometry or SIMS, which could detect minute amounts of elements in samples. His team was using it to find evidence of water in the Earth's molten mantle.

"Then one day I said, 'Look, why don't we go and try it on the moon glass?'" Alberto Saal of Brown University, who helped lead the study, said in a telephone interview.