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Asteroid impact may have helped dinosaurs dominate the world
Dinosaurs are thought to have been wiped out by the impact of an asteroid, but a new study suggests that a similar collision millions of years earlier may have ushered in the dinosaur age.
Dinosaurs are thought to have been wiped out by the impact of an asteroid, but a new study suggests that a similar collision millions of years earlier may have ushered in the dinosaur age.
In a study appearing on Friday in the journal ‘Science’, researchers say that fossil footprints, the presence of a rare mineral and evidence of a sudden growth of ferns some 200 million years ago suggest that a massive rock from outer space hit the earth and helped kill off the large reptiles that ruled the world at the time.
Once the reptiles were gone, says Paul E Olsen of Columbia University, the first author of the study, dinosaurs were able to dominate the earth for more than 135 million years, growing ever larger until they, too, were wiped out by the impact of an asteroid.
During the triassic geologic age, the dominant animals on earth were massive reptiles, mostly four-footed ancestors of the modern crocodile. They roamed a single land mass, a huge body that would later split up to form the earth`s continents.
Dinosaurs then were runty animals, and mammals were even smaller, probably skittering in fear among the rocks.
That changed 200 million years ago, at the end of the triassic and the beginning of the Jurassic age.
Fossils from the same geologic age also show a sudden bloom of ferns, the first plants to appear after the impact of a massive asteroid killed off most other vegetation. A similar spike of fern growth exists in the geologic record at the point when dinosaurs were killed off 65 million years ago.
But the major new finding is the presence of an iridium anomaly at the triassic-jurassic geologic boundary. The concentration of iridium, a chemical rare on earth but common in rocks from outer space, quadrupled at the boundary, suggesting that earth had been hit by a massive asteroid. A much richer iridium anomaly has also been found at the geologic boundary marking the extinction of dinosaurs.
Not all experts are impressed with the findings.
David King, a specialist in cosmic chemistry at the University of Arizona in Tucson, told ‘Science’ that the iridium finding is unimposing. He said that he would be more convinced by shocked quartz grains, an additional sign of an extraterrestrial impact. Further analysis could prove that the iridium came from outer space, King told ‘Science’
Olsen said that footprints preserved as fossils in what is now New Jersey, New York and Pennsylvania show that the massive reptiles abruptly disappeared and were replaced within 30,000 years by large, lumbering dinosaurs.
Bureau Report
But the major new finding is the presence of an iridium anomaly at the triassic-jurassic geologic boundary. The concentration of iridium, a chemical rare on earth but common in rocks from outer space, quadrupled at the boundary, suggesting that earth had been hit by a massive asteroid. A much richer iridium anomaly has also been found at the geologic boundary marking the extinction of dinosaurs.
Not all experts are impressed with the findings.
David King, a specialist in cosmic chemistry at the University of Arizona in Tucson, told ‘Science’ that the iridium finding is unimposing. He said that he would be more convinced by shocked quartz grains, an additional sign of an extraterrestrial impact. Further analysis could prove that the iridium came from outer space, King told ‘Science’
Olsen said that footprints preserved as fossils in what is now New Jersey, New York and Pennsylvania show that the massive reptiles abruptly disappeared and were replaced within 30,000 years by large, lumbering dinosaurs.
Bureau Report