The 300-mile-wide crater lies hidden more than a mile beneath the East Antarctic Ice Sheet.
And the gravity measurements that reveal its existence suggest that it could date back about 250 million years - the time of the Permian-Triassic extinction, when almost all animal life on the planet died out.
The crater lies in the Wilkes Land region of East Antarctica, south of Australia.
Its size and location also suggest that it could have begun the break-up of the Gondwana supercontinent by creating the tectonic rift that pushed Australia northward.
The international team believe that the Permian-Triassic extinction paved the way for the dinosaurs to rise to prominence.
This new crater is more than twice the size of the Chicxulub crater in the Yucatan peninsula, which marks the impact that may have ultimately killed the dinosaurs 65 million years ago
The Wilkes Land meteor is thought to be four or five times bigger than the Chicxulub meteor.
"This Wilkes Land impact is much bigger than the impact that killed the dinosaurs, and probably would have caused catastrophic damage at the time," said Ralph von Frese, a professor of geological sciences at Ohio State University.
He and Laramie Potts, a postdoctoral researcher in geological sciences, led the team that discovered the crater.
They collaborated with other Ohio State and NASA scientists, as well as international partners from Russia and Korea.
The scientists used gravity fluctuations measured by NASA's GRACE satellites to peer beneath Antarctica's icy surface.
"We compared two completely different data sets taken under different conditions, and they matched up," von Frese said.
They reported their preliminary results in a recent poster session at the American Geophysical Union Joint Assembly meeting in Baltimore.
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Date Published: June 02, 2006
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