But this disturbance is more mysterious than Darth Vader. UCLA scientists
don’t know exactly what it was, but they believe it occurred within the
Solar System 65 million years ago. The ensuing pandemonium upset Solar
System dynamics causing Mercury, Earth, and Mars to go off course.

“We speculate that it may also have perturbed asteroids in the inner part of
the asteroid belt, throwing one or more of them into Earth-crossing orbits,”
explained Bruce Runnegar, Director of UCLA’s Center for Astrobiology. “Thus,
the ultimate cause of the K-T impact — and demise of the dinosaurs — may
have been a chaos-induced change in Solar System dynamics.”

Runnegar will present the team’s findings at the Earth Systems Processes
conference on Wednesday, June 27, in Edinburgh, Scotland. The Geological
Society of America and the Geological Society of London will co-convene the
June 24-28 meeting.

The other team members, Ferenc Varadi, a UCLA geophysicist, and Michael Ghil,
the Director of UCLA’s Institute of Geophysics and Planetary Physics, have
worked for years on chaos in the Solar System and, in particular, the role
of in-step motions known as resonances in giving rise to the chaos. This
earlier work on resonances and chaos among the planets and the asteroids
prepared the ground for the present tantalizing results.

“In order to better understand the history of the inner Solar System over
hundreds of millions of years, we carried out several accurate, long-term,
numerical simulations of the orbits of the nine major planets using physical
models with increasing complexity,” Runnegar said. “Our best calculations
show that the dynamical state of the inner Solar System changed abruptly
about 65 million years ago.” Ghil added: “It is possible that it was a
transition through a special kind of resonance that produced the abrupt
change at the K-T boundary.”

While scientists generally accept that there was indeed an extraterrestrial
impact 65 million years ago (at the Cretaceous/Tertiary or K-T boundary) that
wiped out most living species on Earth, they do not agree on the nature of
what caused that impact.

Was it an asteroid? Was it a comet? Now at least we have a better idea and
a vital clue to what really happened with this Earth-shaking event so many
millions of years ago.

CONTACT INFORMATION

During the Earth System Processes meeting, June 25-28, contact the GSA/GSL
Newsroom at the Edinburgh International Conference Centre for assistance
and to arrange for interviews: +44 (0) 131 519 4134

Ted Nield, GSL Science and Communications Officer
Ann Cairns, GSA Director of Communications

The abstract for this presentation is available at:
http://gsa.confex.com/gsa/2001ESP/finalprogram/abstract_8024.htm

Post-meeting contact information:

Bruce Runnegar

Institute of Geophysics and Planetary Physics

University of California

Los Angeles, CA 90095-1567, USA

Office Phone: +01 310 206 1738

runnegar@ucla.edu

Ted Nield

Geological Society of London

+44 (0) 20 7434 9944

ted.nield@geolsoc.org.uk

Ann Cairns

Geological Society of America

+01 303 447 2020 ext. 1156

acairns@geosociety.org