London, June 5: Sixty-five million years ago, a meteor wiped out the dinosaurs. Now new evidence suggests an even bigger chunk of rock hurtled from space into the Earth to give birth to them.
Scientists have located a massive crater under the Antarctic ice that they believe gave rise to the evolution of dinosaurs.
The 480-km-wide crater is thought to have been created by a meteor almost as big as London. It dates back 250 million years to the time of the biggest mass extinction in Earth's history and the event that led to the first dinosaurs evolving. Such was the catastrophic nature of the extinction that up to 96 per cent of all marine creatures were killed and 70 per cent of land animals.
The strike may also have been powerful enough to have begun the break-up of the Gondwana supercontinent, which resulted in Australia sheering off and drifting northwards.
Researchers in the US located the crater more than a mile beneath the East Antarctic ice sheet at Wilkes Land, using gravity measurements from satellites and radar images from aircraft. They calculated that it would take a meteor 30 miles wide to have caused such a crater. By comparison, the meteor held to have ended the dinosaur era and created the Chicxulub crater, in Mexico, would have been six miles across.
'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.
'All the environmental changes that would have resulted from the impact would have created a highly caustic environment that was really hard to endure. So it makes sense that a lot of life went extinct at that time.'
While killing off about nine in every 10 species of animal, the mass extinction paved the way for new animals to evolve. Among the main beneficiaries were archosaurs, the immediate ancestors of dinosaurs, which came quickly to dominate the empty lands.
Within 20 million years of the mass extinction, the first primitive dinosaurs had evolved, including lagosuchus.
For 30 million years they continued to develop and spread and, when another mass extinction took place about 200 million years ago, they were perfectly poised to take over Earth. For the next 135 million years almost every land animal more than a metre long was a dinosaur and it took another meteor, 65 million years ago, to remove them.
Professor von Frese, who reported the findings of the study to the American Geophysical Union Joint Assembly, suggested the Wilkes Land meteor also gave birth to Australia.