On the issue of the origin of the supernova, scientists have no idea (Image source: Center for Astrophysics | Harvard & Smithsonian)

A new study led by the University of Illinois, Urbana-Champaign astronomy and physics professor Brian Fields explores the possibility that astronomical events might have been responsible for an extinction event 359 million years ago, at the boundary between the Devonian and Carboniferous periods. The paper is published in the National Academy of Sciences Proceedings.

The team focused on the Devonian-Carboniferous border, as those rocks contain hundreds of thousands of generations of plant spores that appear to be sunburned by ultraviolet light — evidence of a long-lasting ozone depletion event.

Supernova delivers a one-two punch, the investigators said. The explosion bathes Earth instantly with harmful UV, X-ray, and gamma rays. The explosion of supernova debris eventually crashes into the solar system, subjecting the earth to long-lived irradiation from supernova-accelerated cosmic rays. The damage to Earth and its ozone layer can take up to 100,000 years to last.

However, fossil evidence suggests a 300,000-year collapse in biodiversity prior to the mass extinction of the Devonian-Carboniferous, indicating the possibility of numerous catastrophes, possibly even numerous supernovae.

On the issue of the origin of the supernova, scientists have no idea. The authors note that finding either Plutonium-244 and Samarium-146 long-lived, radioactive isotopes in the rocks and fossils preserved at the time of extinction would indicate a supernova origin. That’s because nowadays no isotope occurs naturally on Earth, and it would have needed a cosmic explosion to get here. Also, they are assuming that the cosmic rays of the supernova may have arrived in a completely different direction (or directions) from where they were produced.

The University of Illinois at Urbana-Champaign notes that other astrophysical causes for ozone depletion, such as meteorite impacts, solar eruptions, and gamma-ray bursts, will quickly end and are unlikely to cause the long-lasting depletion of ozone that occurred at the end of the Devonian period.