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Last Updated: Wednesday, 5 September 2007, 22:31 GMT 23:31 UK
Space pile-up 'condemned dinos'
The collision would have occurred in the asteroid belt

A colossal collision in space 160 million years ago set the dinosaurs on the path to extinction, a study claims.

An asteroid pile-up sent debris swirling around the Solar System, including a chunk that later smashed into Earth wiping out the great beasts.

Other fragments crashed into the Moon, Venus and Mars, gouging out some of their most dominant impact craters, a US-Czech research team believes.

Its study, based on computer modelling, is reported in the journal Nature.

"We believe there is a direct connection between this break-up event, the asteroid shower it produced and the very large impact that occurred 65 million years ago that is thought to have wiped out the dinosaurs," Dr Bill Bottke from the Southwest Research Institute, Boulder, Colorado, US, told BBC News.

Rock swarm

A number of studies have considered what appears to have been an increase in asteroid strikes on Earth in the last 100-200 million years - something like a doubling over the long-term norm.

Dr Bottke and his colleagues have attempted to show that this surge was probably triggered by the catastrophic disruption of a 170km-wide rock in the asteroid belt between Mars and Jupiter about 160 million years ago.

The mountainous object's break-up - induced by a collision with a space rock under half its size - resulted in the cluster of fragments visible today and known as the Baptistina family, they say.

It is thought the dinosaurs could not cope with the impact's effects

The researchers have modelled the evolution of this cluster and concluded that it would have lost many of its original members to the inner Solar System.

The analysis shows, the team says, that one large shard from the break-up probably created the 85km-wide Tycho impact crater on the Moon 108 million years ago.

But even more likely, they contend, is that a still larger fragment dug out the 180km-wide Chicxulub crater off what is today the Yucatan Peninsula of Mexico.

This is the impact scar many scientists link to the Cretaceous/Tertiary Mass Extinction, which saw the dinosaurs disappear into the fossil record.

'Inevitable' outcome

"The [Baptistina] break-up event took place very close to what one might describe as a 'dynamical superhighway', a way for objects to escape the asteroid belt - and many of them did so," explained Dr Bottke.

"These fragments began to wander the region where the Earth and Moon are located; and in fact, so many escaped that it became almost inevitable that some of the larger pieces were going to hit the planets of the inner Solar System."

The Chicxulub crater has left its mark on Mexico

Chemical analysis of projectile material connected to the Chicxulub event is also said to tie its impactor to the type of rocks that make up the Baptistina family.

Philippe Claeys and Steve Goderis from the Free University of Brussels, Belgium, write a commentary on the research in Nature.

They say that unless a rogue comet came from the outer edge of the Solar System ("a rather unlikely event"), the Baptistina asteroid family remains a likely source for the Chicxulub impactor.

"It is a poignant thought that the Baptistina collision some 160 million years ago sealed the fate of the late-Cretaceous dinosaurs well before most of them had evolved," they write.

Dr Bottke's colleagues on the study were David Vokrouhlicky and David Nesvorny.




SEE ALSO
UK plan to track asteroid threat
31 Aug 07 |  Science/Nature
Jupiter shield's mixed blessing
28 Aug 07 |  Science/Nature
Dinosaurs' slow rise to dominance
19 Jul 07 |  Science/Nature
Delay for Nasa asteroid mission
09 Jul 07 |  Science/Nature
Team makes Tunguska crater claim
26 Jun 07 |  Science/Nature
Dino crater viewed from space
10 Mar 03 |  Science/Nature

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