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Asteroid Impact Could Have Cleared the Decks for Dinosaurs'
Rise to Prominence
(From the September/October
2006 issue of StarDate magazine)
The reign of the dinosaurs ended when a mountain-sized asteroid slammed into Earth 65 million years ago, devastating the global climate. An even larger impact 185 million years earlier may have cleared the way for their rise to prominence, according to a team of geologists led by Ralph von Frese of Ohio State. The team reported evidence of the impact at an American Geophysical Union meeting in May.
In a gravity map, above, the circle indicates a dense lump of crust. (The Ohio
State University)
Von Frese discovered a dense lump of crustal rock a mile below the surface of the ice in the Wilkes Land region of Antarctica, south of Australia, in gravity maps produced by the GRACE satellite. His experience in studying craters on the Moon suggested that the feature could have been created by an impact. Airborne radar observations of the ground beneath the ice cap revealed a tall circular ridge around the dense rock about 300 miles (500 km) in diameter.
Although the case is not conclusive, the team suggests that the structure is an impact crater that was created when an asteroid 30 miles (50 km) in diameter — about five times the size of the dinosaur-killing asteroid — hit Earth about 250 million years ago.
That corresponds to “the Great Dying,” when most of the life on Earth suddenly perished. Scientists have suggested several possible causes for the mass extinction, including giant impact events, catastrophic volcanic eruptions, or a nearby supernova explosion. The dinosaurs began their rise shortly afterward.
Von Frese hopes to examine rocks from the edge of the ice shelf to confirm that
they were altered by a powerful impact. — Damond Benningfield
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