Gamma-ray burst may have caused mass extinction 440 million years ago

April 4th, 2009 - 12:47 pm ICT by ANI  

National Geographic Washington, April 4 (ANI): A new study has suggested that a brilliant burst of gamma rays may have caused a mass extinction event on Earth 440 million years ago, and a similar celestial catastrophe could happen again in the future.

Most gamma-ray bursts are thought to be streams of high-energy radiation produced when the core of a very massive star collapses.

According to a report in National Geographic News, the new computer model shows that a gamma-ray burst aimed at Earth could deplete the ozone layer, cause acid rain, and initiate a round of global cooling from as far as 6,500 light-years away.

Such a disaster may have been responsible for the mass die-off of 70 percent of the marine creatures that thrived during the Ordovician period (488 to 443 million years ago), suggests study leader Brian Thomas, an astrophysicist at Washburn University in Kansas.

The simulation also shows that a significant gamma-ray burst is likely to go off within range of Earth every billion years or so, although the stream of radiation would have to be lined up just right to affect the planet.

Currently WR104, a massive star 8,000 light-years away in the constellation Sagittarius, is in position to be a potential threat, according to Thomas.

Study author Thomas’ former graduate advisor, Adrian Melott, first proposed in 2004 that a gamma-ray burst near Earth wiped out Ordovician life.

Since then, both researchers have been tackling pieces of the puzzle.

According to their newest models, gamma radiation from a nearby burst would quickly deplete much of Earth’s protective ozone layer, allowing increased ultraviolet radiation (UV) from the sun to reach the surface.

In the longer term, chemical reactions in the atmosphere would produce dark, nitrogen-based gases that would block the sun’s heat and trigger global cooling, even as the gamma rays continued to deplete ozone and let in UV rays, the authors suggesedt.

Some of the pollution would fall as damaging acid rain, which can severely disrupt ecosystems.

The atmosphere might be able to recover within a decade, and a rise in DNA damage caused by increased UV exposure might pass after a few months or years, the researchers note.

“But other biological impacts-such as reduced ocean productivity-could linger for an unknown length of time,” Thomas said. (ANI)

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