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| An examination of the first material plucked from a comet is forcing scientists to rethink the nature of the frigid emissaries from the deepest reaches of our solar system, as well as the early solar system itself.
Reporting their findings on Thursday, scientists who examined tiny grains retrieved by NASA's Stardust spacecraft from comet Wild 2 (pronounced "vilt") in 2004 found the comet, as expected, contained material from outside the solar system. But they were surprised to find minerals from near the sun as the solar system was first forming 4.6 billion years ago that somehow were expelled to the outer reaches, beyond Pluto, where comets are shaped. "It was extremely exciting," said University of Washington astronomer Donald Brownlee, who led the research published in the journal Science. "We expected the comet to be largely made out of interstellar grains, materials that formed before the solar system formed and were never really affected much by the solar system," Brownlee said in a telephone interview. Comets are small objects, perhaps the oldest in the solar system, that orbit the sun, often with a tail of dust and gas. Phil Bland of Imperial College London, another scientist involved in the research, said the solar system apparently formed in much more turbulent conditions than previously believed. The findings suggest that as the solar system was forming in a corner of the Milky Way galaxy out of a vast spinning disc of gas and dust, it mixed materials over great distances of space rather than coalescing in a more orderly fashion. 'KIND OF WACKY' "You were transporting material over really big distances. So that's kind of wacky for us as planetary scientists," Bland said in an interview. With material shooting from the innermost to the outermost regions, it seemed as if the solar system was "turning itself inside out," Brownlee said, estimating that 10 percent of the material in comets came from the inner solar system. The scientists particularly noted the discovery of calcium aluminum, among the oldest solid matter in the solar system forged close to the young sun. They also discovered magnesium olivine, found in the green sand of some Hawaiian beaches. They said Wild 2's composition seemed to differ from that of Comet Tempel 1, observed in a previous NASA mission. The Wild 2 mission was the first time scientists studied material from a comet rather than merely observing from a distance or analyzing dust particles that may or may not have come from the objects. The particles were tinier than a grain of sand and were studied at 50 laboratories worldwide. Frank Stadermann of Washington University in St. Louis, also involved in the work, said the findings showed the importance of understanding comets. "They basically have preserved the original building blocks of our solar system for 4-1/2 billion years," Stadermann said. Launched in 1999, Stardust zipped through the tail of Wild 2 in January 2004 and spent 15 minutes collecting dust. It returned a payload of thousands of tiny grains in a capsule that landed on the Utah salt flats this past January. A close encounter with Jupiter in 1974 had changed the comet's orbit to a path between Mars and Jupiter, bringing it close enough to study. Source: http://news.yahoo.com/s/nm/20061215/sc_nm/comet_dc |
what are your views on this???
