[Rockhounds] Exploding stars may have caused mass extinction on Earth, study shows

[Kreigh Tomaszewski]

Imagine reading by the light of an exploded star, brighter than a full
moon—it might be fun to think about, but this scene is the prelude to a
disaster when the radiation devastates life as we know it. Killer cosmic
rays from nearby supernovae could be the culprit behind at least one mass
extinction event, researchers said, and finding certain radioactive
isotopes in Earth's rock record could confirm this scenario.

A new study led by University of Illinois, Urbana-Champaign astronomy and
physics professor Brian Fields explores the possibility that astronomical
events were responsible for an extinction event 359 million years ago, at
the boundary between the Devonian and Carboniferous periods.

The paper is published in the *Proceedings of the National Academy of
Sciences*.

The team concentrated on the Devonian-Carboniferous boundary because those
rocks contain hundreds of thousands of generations of plant spores that
appear to be sunburnt by ultraviolet light—evidence of a long-lasting
ozone-depletion event.

"Earth-based catastrophes such as large-scale volcanism and global warming
can destroy the ozone layer <https://phys.org/tags/ozone+layer/>, too, but
evidence for those is inconclusive for the time interval in question,"
Fields said. "Instead, we propose that one or more supernova
<https://phys.org/tags/supernova/> explosions, about 65 light-years away
from Earth, could have been responsible for the protracted loss of ozone."

https://phys.org/news/2020-08-stars-mass-extinction-earth.html