Supernova may account for aquatic dinosaur extinction


LAWRENCE, Kan. – A University of Kansas discovery shows a supernova may have been to blame for an extinction event that took place almost 360 million years ago.

The University of Kansas says in a paper published Aug. 18 in PNAS, three of its researches and their colleagues explain such a scenario for end-Devonian extinctions.

“For more than a decade, my colleagues and I have been interested in the possibility of ionizing radiation events causing extinction events on Earth,” said Adrian Melott, professor emeritus of physics & astronomy at the University of Kansas.

KU says previous findings point to the final extinction event of the Devonian happening simultaneously with a drop in ozone in Earth’s atmosphere.

“When I heard about the evidence for ozone depletion at the end–Devonian, it triggered thoughts about the possibility of a chain of nearby supernovae,” Melott said.

According to KU, previous research pointed to other possible causes for the ozone depletion like global warming, but n to astrophysical sources like exploding stars.

KU says, however, a fellow KU researcher’s findings suggest otherwise. It says Brian Thomas, an adjunct researcher in physics and astronomy and professor of physics at Washburn University, shows that atmospheric warming and the resulting injection of water into the lower stratosphere, which is suggested as a way to cause the ozone depletion, were not tenable.

KU says further, another of its researchers, Bruce Lieberman’s findings point to an astrophysical cause. It says Lieberman, who is a professor of ecology and evolutionary biology, previously emphasized that the end-Devonian extinctions had been part of a long period of diversity decline. It says the prolonged decline was followed by evidence of pollen malformations which suggest ionizing radiation as the cause.

Melott says that left a series of supernovae as the only reasonable possibility.

According to KU, the researchers estimate the supernovae which triggered the events to be around 60 light-years away. It says to give context, Betelgeuse, a future supernova getting much attention for its recent behavior, is about 600 light-years away.

The researchers say the supernovae that triggered the end-Devonian extinction would have been close enough to cause radiation damage on Earth, but not close enough for life-threatening damage.

“The cosmic rays from such a supernova will produce muons in the atmosphere, which are a very penetrating kind of radiation,” Melott said. “They could cause internal damage in large animals and in organisms up to a half-mile down in the ocean.”

According to Melott, the major ionization of the lower atmosphere could have led to a lot of lightning, which could start fires and change the climate.

KU says the researchers’ collaborators on the paper come from the University of Illinois, King’s College London, European Organization for Nuclear Research, Estonia’s National Institute of Chemical Physics and Biophysics and the U.S. Air Force Academy.