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Something NEW in the extinction debate



Yes, you might not think it possible, but:

 http://news.bbc.co.uk/hi/english/sci/tech/newsid_1409000/1409305.stm

A mysterious disturbance in the forces at the heart of the Solar System
could have triggered the asteroid that wiped out the dinosaurs.
              
This intriguing new theory has been put forward by scientists who have
calculated the paths of the planets over the past 100 million years.
              
A US team believes a change in the dynamics of the Solar System caused
Mercury, the Earth and Mars to veer off course.
              
This could have pushed a giant asteroid towards our planet, spelling
downfall for most living things, 65 million years ago.
              
The idea has been floated by a team of astrobiologists at the University
of California, Los Angeles (UCLA), based on simulations of the historical
positions of the major planets.
              
"Our best calculations show that the dynamical state of the inner Solar
System changed abruptly about 65 million years ago," said Bruce Runnegar,
director of UCLA's centre for Astrobiology.

The event modified the average orbit of Mercury, Mars and the Earth in
significant ways, he said, possibly perturbing asteroids in the inner part
of the asteroid belt and throwing one or more of them into Earth-crossing
orbits.
              
"Thus, the ultimate cause of the K-T impact [and the demise of the
dinosaurs] may have been caused by a chaos-induced change in Solar System
dynamics," Dr Runnegar told BBC News Online.
              
The basis of the theory, deduced by team members Ferenc Varadi and Michael
Ghil, is chaos in the Solar System.

Under this scenario, a small shift in the orbit of one or more planets
could destabilise much of the Solar System.  To test their theory, the
researchers simulated the orbits of the major planets, working back in
history over tens of millions of years.
              
To their surprise, computer models pointed to a change in the dynamics of
the inner Solar System at the time of the K-T (Cretaceous-Tertiary) mass
extinction, about 65 million years ago, when many plants and animals
suddenly became extinct.
              
Dr Runnegar said they were now carrying out further studies to test their
theory.
              
"At the moment the link with the dinosaurs is based on a coincidence in
time and a plausible mechanism," he added.