Nov. 25, 2003

Contact: Adrian Melott, Physics and Astronomy, (785) 864-3037; Bruce Lieberman, Physics and Astronomy; (785) 864-2741.

KU research supports explosive hypothesis about extinction

LAWRENCE -- A group of University of Kansas researchers is receiving national attention for research on whether an unparalleled explosion caused one of the great mass extinctions on Earth.

Adrian Melott, professor of physics and astronomy, and Bruce Lieberman, associate professor of geology and courtesy professor in ecology and evolutionary biology, are examining data to support whether gamma ray bursts, or GRBs, were responsible for an ice age and extinction at the end of the Ordovician era, more than 440 million years ago.

"It appears that the bursts are a serious danger, although not something you would expect to hit us very often -- maybe every few hundred million years," Melott said.

The proposal has met with enthusiasm so far and has been reported in Nature and New Scientist.

A GRB, which occurs when a giant star collapses into a black hole, is the most powerful explosion known. During such a collapse, the stars fire gamma ray beams powerful enough to be detected from across the universe.

Sparked by a conversation about GRBs with Mikhail Medvedev, assistant professor of physics and astronomy, Melott began considering whether such an astronomical event would address long-unanswered questions about one of the great mass extinctions on Earth. He put together a group that includes Medvedev; Lieberman; Larry Martin, professor and senior curator at the KU Natural History Museum; Claude Laird, courtesy assistant professor of physics and astronomy; Brian Thomas, graduate student in physics and astronomy; and three scientists at NASA Goddard Space Flight Center.

Although scientists agree that asteroids probably have been responsible for some extinctions -- including the dinosaurs about 65 million years ago -- there never has been a definitive explanation of what happened at the end of the late Ordovician period, when about 70 percent of all species on Earth became extinct.

Although several years ago other researchers first presented the possibility of a hypothetical GRB-mediated extinction, Melott and Lieberman are putting together a case that connects it to a particular event.

Working together and with other colleagues, Melott and Lieberman considered the patterns of extinction among species of trilobites, arthropods that existed in a wide range of depths in the oceans. According to data analyzed by Lieberman, the effect on trilobites depended on the depth of each species' habitat.

"We see certain patterns in the fossil record of those that go extinct and those that survive," Lieberman said. "Those that tend to go extinct lived in shallow water and died at a much higher rate than those that burrowed deep into the sediment or lived in deeper water."

The researchers say the hypothesis shows promise for at least two reasons.

First, if a GRB destroyed the earth's ozone layer, radiation would have had a greater effect on species in shallow water, which is supported by Lieberman's fossil data.

Second, the data explains why the Ordovician period ended with an ice age. Until now, scientists haven't agreed why an ice age would have occurred on the heels of an era when the climate was very warm. Melott said atmospheric changes brought on by a GRB could have blocked the sun's rays for an extended period, contributing to global cooling.

"We have a double whammy here because we can explain both the depth-dependence and the ice age," Melott said.

Melott said the team is seeking funding to support further research that wouldn't depend on data collected elsewhere.

Lieberman said their research also could have contemporary applications.

"On a smaller scale, we can recognize the detrimental effect that the depletion of the ozone layer might have," he said.

For more information, contact Melott at (785) 864-3037 or, or Bruce Lieberman at (785) 864-2741 or


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