Gamma-ray burst linked to mass extinction
440-million-year-old fossils hint at cosmic explosion.
24 September 2003
PHILIP BALL

Some 440 million years ago, a nearby gamma-ray burst may have extinguished much of life on Earth, say US astronomers.

Adrian Melott, of the University of Kansas in Lawrence, and colleagues reckon that the fossil record of the end of the Ordovician period fits with how such a cosmic explosion a few thousand light years away could have altered the environment. At that time, more than 100 families of marine invertebrates died out; it was the second most devastating mass extinction in our planet's history.

The possibility of life on Earth being affected by cosmic events has been long recognized. Giant asteroid impacts have been proposed as a cause of global wildfires and climate cooling that could have been behind events such as the extinction of the dinosaurs 65 million years ago...

The rest is here at Nature.