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Inside-Out Study Challenges Theory About Comet Chemistry
Paris (AFP) July 11, 2007 A dying comet has prompted astronomers to take issue with a mainstream theory about the impact of "space weather" on these enigmatic wanderers of the Solar System. Comets are fragile clusters of dust, ice and carbon-based molecules that are believed to be primitive material left over from the building of our star system. A common expectation is that the outer layers of comets must undergo change as the aeons pass. They are bashed by cosmic rays from deep space, by solar particles and by huge changes in temperature as they swing around the Sun and head back into the chilly depths of the Solar System. In theory, this "weathering" should be especially pronounced in so-called short-period comets, which return every few years, as opposed to counterparts that can take centuries to loop around the Sun. But astronomers in the United States, seizing a unique chance after a short-period comet broke up, say cometary chemistry appears to be the same, inside and out. They looked at Comet 73P/Schwassmann-Wachmann 3 -- 73P for short -- which returns around the Sun every 5.3 years. In 1995, 73P experienced a catastrophic breakup, disintegrating into 68 large fragments, two of which were hundreds of metres (yards) across. Last year, 73P, escorted by its disparate family, zipped by close to Earth, enabling the astronomers to glimpse the chemical composition of the two big chunks, using spectrometers at the giant observatory at Mauna Kea, Hawaii. They found that, unlike most comets, the fragments were low in complex volatile ices, such as acetylene, methanol and ammonia, which suggests they were unusually primordial in origin. And contrary to expectation, the fragments were found to be chemically very similar, inside and externally, which challenges the weathering theory. The paper, led by Johns Hopkins University's Neil Dello Russo, appears in Thursday's Nature, the weekly British science journal.
Source: Agence France-Presse Related Links Johns Hopkins University Asteroid and Comet Mission News, Science and Technology
New Clovis-Age Comet Impact Theory
Eugene, OR (SPX) May 23, 2007Two University of Oregon researchers are on a multi-institutional 26-member team proposing a startling new theory: that an extraterrestrial impact, possibly a comet, set off a 1,000-year-long cold spell and wiped out or fragmented the prehistoric Clovis culture and a variety of animal genera across North America almost 13,000 years ago. |
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