MEXICO:Scientists have tracked down the asteroid thought likely to have put paid to the dinosaurs 65 million years ago. The culprit is very likely to have been a large chunk of the Baptistina asteroid, knocked free after a huge asteroid collision 160 million years ago.
Few scientists dispute the theory that the dinosaurs exited this world after a rocky asteroid several kilometres across struck the Earth. The impact changed the world's climate for hundreds of years, caused mass extinctions and left an impressive signature - the crater at Chicxulub, Mexico, which is 180km in diameter.
Now a group of scientists from the US and the Czech Republic have revealed that the dinosaurs' nemesis was one of some 170,000 large bodies created when an asteroid about 60km across smashed into the 170km-wide Baptistina asteroid.
Asteroids are found in a belt which rings the Sun in an orbit between that of Mars and Jupiter. It is unclear whether the belt represents a former planet which broke into smithereens or is made up of leftovers from when the solar system formed.
Asteroids sometimes jostle out of position, their orbits perturbed by large planets such as Jupiter, and when they do collisions result.
The research team, writing in the journal Nature, suggest that Baptistina orbited in the innermost region of the asteroid belt and was struck and broke into an "asteroid family" perhaps 160 million years ago.
This means the writing was on the wall for the dinosaurs as many as 100 million years before their extinction.
The fragments were eventually pulled out of orbit to drift into a "dynamical superhighway" where they could escape the belt to career across the Earth's path.
The researchers point to a known doubling of asteroid impacts recorded on the Earth and on the Moon about 100 million years ago, suggesting that the Baptistina family was the cause. Chicxulub is "90 per cent likely" to have been caused by a family member and it is 70 per cent likely that another Baptistina refugee knocked the 85km-diameter Tycho crater into the lunar surface 108 million years ago.