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News Release June 21, 2001
GSA Release No. 01-26
Contact: Christa Stratton

A Disturbance In the "Force" Caused the K-T Impact?

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.


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:

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

Ted Nield
Geological Society of London
+44 (0) 20 7434 9944

Ann Cairns
Geological Society of America
+01 303 447 2020 ext. 1156

To view other Earth System Processes press releases, see

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