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From: RSchatte@aol.com Date: Wed, 26 Nov 1997 21:35:43 -0500 (EST) Fwd Date: Thu, 27 Nov 1997 08:01:01 -0500 Subject: Scientists Describe Asteroid Impact --------------------- Forwarded message: Subj: Scientists Describe Asteroid Impact Date: 97-11-26 13:11:08 EST From: AOL News Scientists Describe Asteroid Impact .c The Associated Press By PETER JAMES SPIELMANN SYDNEY, Australia (AP) - An asteroid that tumbled through space for eons blasted into the sea off Antarctica more than 2 million years ago with the force of ``a cosmic bomb,'' a multinational team of scientists said in a research paper published Wednesday. Striking the Bellingshausen Sea with the explosive power of 100 billion tons of TNT, the asteroid Eltanin blew a column of water 3 miles high and punched a temporary ``oceanic crater'' in the sea, according to the paper, which appeared in the British science journal Nature. The researchers estimate the asteroid was at least six-tenths of a mile and possibly up to 2 1/2 miles in diameter. The blast in the ocean did not leave a crater on the seabed, but a similar strike on land would have left a hole 9 to 25 miles across. Eltanin, the only asteroid ever known to have hit water, triggered waves 65 to 130 feet high, ``devastating mega-tsunamis'' that swamped the coasts of South America and Antarctica. ``The tsunami ... destroys enormous, large areas. ... In the Pacific Rim there are signs of such things,'' one of the lead researchers, Rainer Gersonde of the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, told The Associated Press in a telephone interview Wednesday. Sediment spread up to 2,500 miles away and dust, vapor and salts wafted around the world. Enough debris and hot vapors were emitted to possibly damage the Earth's ozone layer, the researchers said. ``The dust and vapor probably caused a major change in climate, but whether that persisted or was for just a few years, we just don't know,'' said Karsten Gohl, a geologist from Macquarie University in Sydney who worked on the project. There is no evidence that the climatic change caused the extinction of any species. New seismic and deep-sea surveys conducted in 1995 by the German research ship Polarstern enabled the scientists to accurately date the blast to the late Pliocene period, 2.15 million years ago, and to gauge its effects. The blast was well after the Northern Hemisphere's Ice Age began but ``close to one of the strongest cooling events in this time period,'' the researchers' paper said. ``It might be that this strong cooling was related to the impact,'' Gersonde told the AP. The fallout from the blast may explain the ``Sirius enigma,'' the puzzle of why marine fossils are found high above sea level in the Transantarctic Mountains. The researchers believe fallout from the steam and vapor cloud dropped micro-fossils directly on the mountains, an idea that geologist Peter Barrett at Victoria University of Wellington, New Zealand, called ``reasonably plausible.'' David Harwood at the University of Nebraska, an expert on the Sirius fossils, conceded that the fallout theory ``has potential'' but said some Sirius deposits do not fit the model. He is among those who think moving ice sheets may have scoured fossil deposits and redeposited them in unexpected sites. The Eltanin impact was a medium blast, as asteroids go. About 65 million years ago, a 6-mile-wide asteroid crashed into an area near Mexico's Yucatan Peninsula, creating a 112-mile-wide crater. Some scientists believe this event kicked up enough dust to blot out the sun, killing more than 80 percent of all animals on Earth and leading to the extinction of the dinosaurs. But rocks far smaller than Eltanin can cause massive damage: A meteorite only 150 feet across created Arizona's Meteor Crater, 4,000 feet wide and 600 feet deep. A rock just 30 feet across, hitting Earth from outer space, releases energy equal to about five Hiroshima-sized bombs. Although the Earth's surface is 70 percent water, Eltanin is the only asteroid to strike the ocean that scientists know about, compared with about 140 known to have hit land, Jan Smits of the Research School of Sedimentary Geology at Amsterdam's Vrije University noted in a commentary on the research in Nature. ``Where might the traces of these events be hiding?'' Smits asked. Besides Gersonde, in Germany, researchers on the project included Frank Kyte at the Institute of Geophysics and Planetary Physics at UCLA and scientists from the Department of Geology at the University of Salamanca in Spain; Macquarie University's School of Earth Sciences in Sydney; and the U.S. Naval Research Lab in Washington. Eltanin is named for the U.S. research ship that brought up deep sea samples in 1965 that later were found to contain iridium, an element in asteroids. AP-NY-11-26-97 1307EST Copyright 1997 The Associated Press. The information contained in the AP news report may not be published, broadcast, rewritten or otherwise distributed without prior written authority of The Associated Press.
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