EXTINCTION BY SUPERNOVA

Earth’s fossil record suggests its ozone layer took a protracted beating

One of the worst extinction events in Earth’s history may have been triggered by a supernova, the violent death of a distant star.

About 75 per cent of all species on Earth died out at the end of the Devonian Period, nearly 360 million years ago. Rocks from this era preserve many thousands of spores that appear to be scorched by ultraviolet (UV) radiation, indicating that something went seriously wrong with our protective ozone layer.

The destructive force may have come from very far afield. “Earth-based catastrophes such as large-scale volcanism and global warming can destroy the ozone layer too, but evidence for those is inconclusive for the time interval in question,” said Brian Fields, a professor of physics and astronomy at the University of Illinois at Urbana-Champaign.“Instead we propose that one or more supernovae, about 65 light years away from Earth, could have been responsible for the protracted loss of ozone.”