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37 研究表明2500万年前流星曾碰撞过地球
DATE=4-18-01
TITLE=SCIENCE REPORT - Meteor Collision With Earth
BYLINE=Jill Moss
(Start at 59")This is the VOA Special English Science Report.
American researchers have discovered new (1) evidence that suggests a huge space (2) rock crashed into Earth two- hundred- fifty- million years ago. The discovery was published in Science magazine. Luann Becker of the University of Washington led the study. She estimates the space rock, or meteor, was between six and twelve kilometers across. She also says the energy released by the (3) meteor could have equaled an earthquake measuring twelve on the Richter Scale.
Researchers believe the force of the crash may have caused (4) volcanoes to explode and spread liquid rock. Huge clouds of dust and dirt probably flew into the air. Researchers say this likely caused chemical acid rain and a warming of the Earth's atmosphere.
The researchers also believe the changes caused by the crash killed almost all the plants and animals on Earth. The researchers estimate ninety percent of all ocean life was killed and seventy percent of all land animals disappeared. They say this mass extinction happened within one- hundred- thousand years. The researchers also suspect this mass extinction marks the separation of two early periods in Earth's history. Scientist had long believed that the end of the (5) Permian period and beginning of the Triassic period began with a meteor crash. However, there has been little evidence of this until now.
In their study, the researchers found carbon (6) molecules trapped in rocks dating back to the Permian period. The molecules are called Fullerenes, or Buckyballs. They contain gases that are found only in space. Mizz Becker says buckyballs form under extreme pressure, such as when a meteor hits the Earth's surface. Based on her research, she says the force of the meteor hitting the Earth spread buckyballs around the planet. Scientists found these molecules in rocks from China and Japan.
No huge hole has been found to mark where the meteor crashed. Some scientists think it happened in Western Australia. Mizz Becker disagrees. She says the event happened so long ago that any hole made by a meteor has been smoothed back into the Earth's surface.
Researchers say the Buckyball molecules should ease any disbelief that a mass (7) extinction happened more than two hundred-fifty million years ago.
This VOA Special English Science Report was written by Jill Moss. This is Bill White.
注释：
(1) evidence[ 5evidEns ]n.明显,根据, [物]证据, 证物
(2) rock[ rCk ]n.岩石, 暗礁,v.摇摆
(3) meteor[ 5mi:tjE ]n.流星, 大气现象
(4) volcano[ vCl5keinEu ]n.火山
(5) permian [5pE:miEn] a.[地]二叠纪的n.二叠纪
(6) molecule[ 5mClikju:l, 5mEu- ]n.[化]分子, 些微
(7) extinction[ iks5tiNkFEn ]n.消失, 消灭 [物]消光
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