[meteorite-list] Chaos Clues To Dino Demise

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:44:14 2004
Message-ID: <200106271652.JAA04757_at_zagami.jpl.nasa.gov>

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

Chaos clues to dino demise
By Helen Briggs
BBC News
June 27, 2001

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.

Chaos theory

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.

'Tenuous' link

The research, presented at the Earth System Processes meeting in Edinburgh,
UK, has received a mixed reaction from other experts.

Professor Mark Bailey of the Armagh Observatory, Armagh, said the asteroid
link appeared tenuous, but not impossible.

"[It] relies not least on the assumption that the killer projectile was an
asteroid and not a comet," he told BBC News Online.

"Nevertheless, the idea that the resonant frequencies of the Solar System
change chaotically on time-scales of tens to hundreds of millions of years
(albeit only slowly and by relatively small amounts) is an interesting one
which adds yet another wrinkle to the story of our changing Solar System."

Professor Carlos Frenk, an astrophysicist at the University of Durham, UK,
said the theory appeared plausible.

"If these calculations are correct, they are very revealing of the unusual
past behaviour of the Solar System," he told BBC News Online.

"The past history of the Solar System was not as quiet as we thought - this
very unusual chaotic behaviour may have happened on our doorstep."
Received on Wed 27 Jun 2001 12:52:25 PM PDT