New research explores whether astronomical phenomena were responsible for an event of extinction massive ago 359 million years, at the boundary between the periods Devonian and Carboniferous.
The study led by the professor of astronomy and physics of the University of Illinois, Urbana-Champaign, Brian Fields, and that is published in Proceedings of the National Academy of Sciences, states that cosmic rays from a nearby supernova they unleashed that extinction. Certain radioactive isotopes in the rock record of the land could confirm this scenario.
The team focused on the limit Devonian-Carboniferous because those rocks contain hundreds of thousands of generations of plant spores that appear to have been burned by ultraviolet light, evidence of an event depletion of ozone Long duration.
“The terrestrial catastrophes, such as large-scale volcanism and global warming, can also destroy the ozone layerBut the evidence for that is not conclusive for the time interval in question, “Fields said.
“Instead, we propose that a or more supernova explosions, a about 65 light years distant from Earth, they could have been responsible for the prolonged ozone loss, “he added.
“To put this in perspective, one of the closest supernova threats today is the star Betelgeuse, which is more than 600 light years from distance and well outside the 25 light-year death distance, “said the graduate student and study co-author. Adrienne Ertel, it’s a statement.
The team explored other astrophysical causes of ozone depletion, such as impacts from meteorites, solar flares and gamma ray bursts. “But these events end quickly and are unlikely to cause the lasting ozone depletion that occurred at the end of the Devonian period,” said the graduate student and study co-author. Jesse Miller.
A supernova -which is the explosion of a star-, on the other hand, deals a double blow, investigators said. The explosion immediately bathes the Earth with ultraviolet rays, X-rays and rays harmful gamma.
Later, the explosion of debris from supernova It hits the solar system, subjecting the planet to a long-lasting irradiation of cosmic rays accelerated by the supernova. Damage to land and its ozone layer can last up to 100,000 years.
However, fossil evidence indicates a 300,000-year decline in biodiversity that led to the Devonian-Carboniferous mass extinction, suggesting the possibility of multiple catastrophes, perhaps even multiple supernova explosions. “This is entirely possible,” he said. Miller.
“Massive stars generally occur in clusters with other massive stars, and other supernovae are likely to occur shortly after the first explosion,” he added.
The team said the key to proving that a supernova occurred would be to find the radioactive isotopes. plutonium-244 and samarium-146 in rocks and fossils deposited at the time of extinction. “None of these isotopes are naturally found on Earth today, and the only way they can get here is through cosmic explosions,” said the undergraduate student and co-author. Zhenghai Liu.
Radioactive species born in the supernova they are like green bananas, he said Fields. “When you see green bananas in IllinoisYou know they are fresh and that they did not grow here. Like bananas, Pu-244 y Sm-146 they break down over time. So if we find these radioisotopes on Earth today, we will know that they are fresh and not from here, the green bananas of the world of isotopes, and thus the smoking guns of a nearby supernova. “
Researchers have yet to search Pu-244 o Sm-146 on boundary rocks Devonian-Carboniferous. The team of Fields said their study aims to define patterns of evidence in the geological record that would point to supernova explosions.
“The overall message from our study is that life in the land it does not exist in isolation, “Fields said.” We are citizens of a bigger cosmos, and the cosmos intervenes in our lives, often imperceptibly, but sometimes fiercely. “
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