New comet could be source of Earth's water

Ocean water, long believed to have come from icy comets beyond Neptune, may have originated in asteroids found in warmer regions much closer to Earth, according to astronomers in Hawaii.

Ocean water, long believed to have come from icy comets beyond Neptune, may have originated in asteroids found in warmer regions much closer to Earth, according to astronomers in Hawaii.

Two astronomers at the University of Hawaii found traces of water in an asteroid-like object floating in the solar system near Jupiter. It was a rare discovery in an area so close to the sun and, until know, believed to be orbited only by dry asteroids.

Prof David Jewitt and graduate student Henry Hsieh, who reported the findings, believe that a collision dug a hole into the three asteroids, exposing their liquid interior.

“We think that the water has been buried below the surface of asteroids,” Hsieh said. “It’s basically been preserved this whole time by being buried, shielded from the sun.”

Jewitt and Hsieh spotted the objects last November using the 26ft Gemini North telescope atop Mauna Kea volcano on the Big Island. Their study will appear in Thursday’s edition of Science Express, the online edition of the journal Science, which will feature the research in an April print edition.

Because the Earth is believed to have formed too hot to hold water, scientists have long turned to the icy comets as the leading candidates to have brought water to Earth. But recent analysis has shown that comet water differs from ocean water, Jewitt says.

“If you just melted a bunch of comets they would not look like the oceans,” he said.

That means that asteroids could turn out to be the main source of Earth’s water, even though they have been historically considered to be “bone-dry” rocks, according to Jewitt.

Astronomers are now waiting for the powerful Pan-STARRS telescope to be built on Haleakala on Maui so they can hopefully find and conduct more studies on the icy asteroids.

“This thing will survey the whole sky repeatedly,” Jewitt said of the telescope, which will begin collecting data later this year. “It will find, we think, hundreds or thousands of these objects.”

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