(CNN) — Simultaneous explosions of stars, called supernovae, may have led to one of Earth’s mass extinctions 359 million years ago, according to new research.
Several global extinction events occurred during the Devonian period, which lasted from 359 million to 419.2 million years ago, and also ended it. The collective events resulted in the loss of 70 to 80 percent of all animal species present during the Devonian, greatly affecting marine life.
The beginning of the Carboniferous period, occurred later, and lasted between 299 million and 359.2 million years.
No cause has previously been associated with the Devonian extinctions, but new research suggests that multiple supernovae may have caused the drop in ozone levels with the final extinction event that ended the Devonian period.
The research team focused on the boundary between the Devonian and Carboniferous periods because rocks from this time reveal something intriguing: The plant spores they contain appear to have been burned by ultraviolet light. Ozone levels in the Earth’s stratosphere also dropped at this time.
“Terrestrial catastrophes, such as large-scale volcanism and global warming, can also destroy the ozone layer, but the evidence for this is inconclusive for the time frame in question,” Brian Fields, author of the report, said in a statement. study and professor of astronomy and physics at the University of Illinois at Urbana-Champaign.
“Instead, we propose that one or more supernova explosions, some 65 light-years distant from Earth, could have been responsible for the prolonged loss of ozone.”
The “death distance” of supernovae is about 25 light years. A supernova, or multiple explosions, 65 light-years away wouldn’t decimate life on Earth, but it could hit our planet with enough radiation to damage the ozone layer and expose Earth to ultraviolet and cosmic rays.
The study was published this week in the journal Proceedings of the National Academy of Sciences.
In the impact distance
Gamma ray bursts, flares from the Sun and the impact of meteorites hitting Earth could also deplete ozone, but it doesn’t seem likely in this case.
“But these events end quickly and are unlikely to cause the lasting depletion of the ozone layer that occurred at the end of the Devonian period,” said Jesse Miller, co-author of the study and a graduate student at the University of Illinois at Urbana-Champaign, it’s a statement.
An exploding star, or several exploding stars, would cause immediate damage when hitting Earth with ultraviolet, gamma, and X rays. And about 1,000 years later, the supernova remnants would strike our solar system, radiating Earth with high levels of intense cosmics rays.
This type of damage could persist for 100,000 years, according to Adrian L. Melott, a co-author of the study and a physicist at the University of Kansas.
“Cosmic rays from such a supernova will produce muons in the atmosphere, which are a very penetrating type of radiation,” Melott said. “They could cause internal damage to large animals and organisms up to a kilometer deep in the ocean.”
There is also likely an excess of lightning, which could start wildfires and lead to climate change.
Before the mass extinction event 359 million years ago, evidence in the fossil record suggests that Earth’s biodiversity declined for 300,000 years, the other extinction events of the Devonian period.
That is why researchers believe that multiple supernovae are responsible for what happened on Earth, which is very likely.
“Very massive stars are typically born in large associations and live short lives, so they are likely to go out at the same time,” Melott said.
To show that supernovae were the cause of this mass extinction, it will be necessary to find radioactive isotopes in the rock record from this time period, such as plutonium-244 and samarium-146. Supernovae would have left traces of these in rocks and fossils on Earth.
“None of these isotopes are naturally found on Earth today, and the only way they can get here is through cosmic explosions,” said Zhenghai Liu, co-author of the study and Urbana-Champaign undergraduate student at the University of Illinois. , it’s a statement.
“When you see green bananas in Illinois, you know they’re fresh and you know they didn’t grow here,” Fields said. «Like bananas, [los isótopos] Pu-244 and Sm-146 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 therefore are the smoking weapons of a nearby supernova.
It is the latest in a series of studies written by members of this research team in recent years, which also suggest that supernovae potentially motivated the first humans to walk upright when starting forest fires and kill large marine animals at the dawn of the Pleistocene 2.6 million years ago.
“For more than a decade, my colleagues and I have been interested in the possibility of ionizing radiation events causing extinction events on Earth,” Melott said.
“The overall message from our study is that life on Earth does not exist in isolation,” Fields said. “We are citizens of a larger cosmos, and the cosmos intervenes in our lives, often imperceptibly, but sometimes fiercely.”
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