Illinois: Exploding Stars May Have Caused Mass Extinction on Earth

[bystander]

Exploding Stars May Have Caused Mass Extinction on Earth
University of Illinois, Urbana-Champaign | 2020 Aug 19

A team of researchers led by professor Brian Fields hypothesizes that a supernova about 65 light-years away may have contributed to the ozone depletion and subsequent mass extinction of the late Devonian Period, 359 million years ago. Pictured is a simulation of a nearby supernova colliding with and compressing the solar wind. Earth’s orbit, the blue dashed circle, and the Sun, red dot, are shown for scale. Graphic Courtesy: Jesse Miller

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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 ... explores the possibility of astronomical events being responsible for an extinction event that occurred 359 million years ago, at the boundary between the Devonian and Carboniferous periods. ... The team concentrated on 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. ...

The team explored other astrophysical causes for ozone depletion, such as meteorite impacts, solar eruptions and gamma-ray bursts. “But these events end quickly and are unlikely to cause the long-lasting ozone depletion that happened at the end of the Devonian period,” said ... Jesse Miller.

A supernova, on the other hand, delivers a one-two punch, the researchers said. The explosion immediately bathes Earth with damaging UV, X-rays and gamma rays. Later, the blast of supernova debris slams into the solar system, subjecting the planet to long-lived irradiation from cosmic rays accelerated by the supernova. The damage to Earth and its ozone layer can last for up to 100,000 years. ...

Supernova Triggers for End-Devonian Extinctions ~ Brian D. Fields et al

• Proceedings of the NAS (online 18 Aug 2020) DOI: 10.1073/pnas.2013774117
• arXiv.org > astro-ph > arXiv:2007.01887 > 03 Jul 2020

[BDanielMayfield]

Iridium in the CT boundary layer was key to cinching the case for an impact doing in the dinosaurs. Here's what could do so for this theory:

The team said the key to proving that a supernova occurred would be to find the radioactive isotopes plutonium-244 and samarium-146 in the rocks and fossils deposited at the time of extinction. “Neither of these isotopes occurs naturally on Earth today, and the only way they can get here is via cosmic explosions,” said undergraduate student and co-author Zhenghai Liu.

The radioactive species born in the supernova are like green bananas, Fields said. “When you see green bananas in Illinois, you know they are fresh, and you know they did not grow here. Like bananas, Pu-244 and Sm-146 decay over time. So if we find these radioisotopes on Earth today, we know they are fresh and not from here – the green bananas of the isotope world – and thus the smoking guns of a nearby supernova.”

Researchers have yet to search for Pu-244 or Sm-146 in rocks from the Devonian-Carboniferous boundary. Fields’ team said its study aims to define the patterns of evidence in the geological record that would point to supernova explosions.

[neufer]

Exploding Stars May Have Caused Mass Extinction on Earth
University of Illinois, Urbana-Champaign | 2020 Aug 19

A new study ... explores the possibility of astronomical events being responsible for an extinction event that occurred 359 million years ago, at the boundary between the Devonian and Carboniferous periods. ... The team concentrated on 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. ...

The team said the key to proving that a supernova occurred would be to find the radioactive isotopes plutonium-244 and samarium-146 in the rocks and fossils deposited at the time of extinction. “Neither of these isotopes occurs naturally on Earth today, and the only way they can get here is via cosmic explosions,” said undergraduate student and co-author Zhenghai Liu. The radioactive species born in the supernova are like green bananas, Fields said. “When you see green bananas in Illinois, you know they are fresh, and you know they did not grow here. Like bananas, Pu-244 and Sm-146 decay over time. So if we find these radioisotopes on Earth today, we know they are fresh and not from here – the green bananas of the isotope world – and thus the smoking guns of a nearby supernova.” Researchers have yet to search for Pu-244 or Sm-146 in rocks from the Devonian-Carboniferous boundary. Fields’ team said its study aims to define the patterns of evidence in the geological record that would point to supernova explosions.

But a certain Samarium (half life 68 million years), as he travelled, came where the plant spores were. When he saw them he was moved with compassion, came to the plant spores, and bound up their wounds, pouring on oil and wine.