WASHINGTON – University of Maryland, College Park researchers working with NASA may have discovered clues to the origins of life on Earth — water on the surface of a comet.
“(This study) confirms that the water for life on Earth could have come from comets,” Michael A’Hearn, principal investigator of the mission.
The researchers are part of NASA’s Deep Impact project and published their findings Thursday in the online version of the journal Science. Their discovery came from a probe that smashed into the comet Tempel 1 last summer and found ice in three small pockets on the comet’s nucleus, or solid body.
Surprisingly, the data showed more ice than expected lies below the comet’s surface, A’Hearn said.
“What we have discovered is where the water is,” A’Hearn said. “Most of it is below the surface — that is the big discovery of this project.”
Another major revelation of the mission is that comets contain a large amount of life-giving organic material, A’Hearn said. Scientists have long been confident that comets contained a large amount of water, but they were unsure how much organic material comets harbored.
“(This finding) suggests that comets are still viable sources of water and organic material,” said Jessica Sunshine, lead author of the Science article and a chief scientist at Science Applications International Corp. “We don’t have a quick answer, but (these results) are another piece of the puzzle.”
Deciphering the composition of comets may yield clues to the origin of the solar system an estimated 4.5 billion years ago. Scientists hold that comets, which are generally made of ice, gases and dust, have not changed significantly since then.
Researchers are next going to try to pinpoint the location of the ice below the comet’s surface, Sunshine said. Before the mission, most scientists thought the bulk of the water would be on the surface — not under it.
“The common expectation was that water would be all over the surface,” Sunshine said. “But what we found was that it was in small, discrete areas.”
The surface ice covered less than one-half of 1 percent of the surface area, she said. The impact from the probe revealed that much more ice lay beneath.
Researchers will meet Monday and Tuesday to try to review the data and gain a better understanding of the comet’s composition, A’Hearn said. According to current data, about three-quarters of the comet is empty space.
Because scientists have combed through only about 10 percent of the data, more revelations should be forthcoming, A’Hearn said. By the end of March, he said, scientists will likely unlock the next major piece of the puzzle.
In the meantime, the researchers will publish “big-picture” studies regarding their findings in Icarus, a planetary journal of the American Astronomical Society.
The $330 mission was launched a year ago and the probe struck Tempel 1 on July 4 about 83 million miles from Earth. Tempel 1, which at 45 square miles is about two-thirds the size of the District of Columbia, was discovered in 1867. It travels on an elliptical path between Mars and Jupiter, orbiting the sun once every 5.5 years.
The project’s success has established the Deep Impact team as a contender for NASA’s next major comet project in 2008. A’Hearn said his team will submit a proposal to explore the comet Boethin at a cost of about $30 million.
“Before our impact, NASA wasn’t even going to let us propose,” A’Hearn said. “Now they’ve seen the public is interested.”
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