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Space
pile-up 'condemned dinos' 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.
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.
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. 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.
"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." 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. (news.bbc.co.uk) |
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Other fragments crashed into
the Moon, Venus and Mars, gouging out some of their most dominant impact
craters, a US-Czech research team believes. 
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. 