A team of scientists working on two continents has discovered that a series of five craters on Europe and North America form a chain, indicating the breakup and subsequent impact of a comet or asteroid that collided with Earth approximately 214 million years ago.
The impacts may have contributed to a mass extinction that occurred at the end of the Triassic period–one of the five greatest mass extinctions in history.
The work, by scientists at the University of Chicago, the University of New Brunswick (Canada) and The Open University (Milton Keynes, U.K.) is published in a paper in the Thursday, March 12, issue of the journal Nature.
“When scientists observed the impacts of the pieces of Comet Shoemaker-Levy 9 on Jupiter in July 1994, they said that the impact of a fragmented comet could never happen here on Earth because the Earth’s gravitational field is too weak to break a comet into pieces,” said David Rowley, University of Chicago Associate Professor in Geophysical Sciences. “But our studies of these five craters provide compelling evidence that this happened at least once, and there’s no reason it couldn’t have happened more than that.”
Rowley’s colleagues, John Spray, a structural geologist from the University of New Brunswick, and Simon Kelley from The Open University, were interested in the relationship between impact craters of similar ages. Kelley had developed a technique to date such craters more precisely–using laser argon/argon dating of the glass formed by localized heating of the rock. They asked Rowley to help figure out how the craters were aligned when the impacts occurred–because of plate tectonics, the continents have moved extensively in the last 214 million years.
Rowley, a principal investigator for the University of Chicago’s
Paleogeographic Atlas Project, which is compiling an atlas of the
paleogeography and paleoclimate of th
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Contact: Diana Steele
d-steele@uchicago.edu
773-702-8366
University of Chicago Medical Center
12-Mar-1998