About 444 million years ago, more than half of all marine invertebrates were wiped out at the end of the Ordovician era in the third worst mass extinction in history.

A couple of years ago, Brian Thomas at the University of Kansas pointed out that this holocaust could have been caused by a nearby supernova zapping the Earth with gamma rays. A 10 second burst of gamma rays, they said, would have done for about half Earth’s ozone layer, leaving life here more or less unprotected from the Sun’s harmful UV rays for 10 years or more.

Organisms living deep beneath the waves would, of course, have been protected from UV rays anyway but those nearer the surface would have been wiped out within that time. What makes Thomas’ idea interesting is that the geological record seems to indicate that species living nearer the surface were hardest hit in the Ordovician extinction.

Today, Thomas and a pal give us an update based on more detailed simulations. They say the geological data is consistent with a gamma ray burst somewhere over the South Pole.

And this also allows them to predict that any large land mass well above the equator would have been shielded from the burst and so the geological record there ought to be different. Thomas suggests that northern China would be as good a place as any to start looking.

Better get digging.

Ref: arxiv.org/abs/0809.0899: Late Ordovician Geographic Patterns of Extinction Compared with Simulations of Astrophysical Ionizing Radiation Damage

This entry was posted on Thursday, September 11th, 2008 at 12:52 am and is filed under Changin' the world, Hellraisin'. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.