Supernovae Could Have Caused Mass Extinctions On Earth

Posted: May 23 2018, 4:20pm CDT | by , Updated: May 23 2018, 5:34pm CDT, in News | Latest Science News

Supernovae could have Caused Mass Extinctions on Earth
The ultraviolet radiation from a nearby supernova may have resulted in changes in life on Earth. Credit: David Aguilar (CfA)

New study says that supernovae likely caused decrease in Earth's ozone layer, which also affected its atmosphere

Researchers say they may have found the cause of mass extinctions on Earth. Two nearby supernovae that exploded about 2.5 and 8 million years ago would have reduced ozone layer and affected life on Earth. In particular, the supernova exploding two-and-a-half million years ago led to dramatic changes on Earth. Around that time, Pliocene epoch was ending and glacial period of Pleistocene was set to begin. The follow-up investigation based on computer modeling shows that a supernova contributed to that change. The particular supernova occurred between 163 and 326 light years away from Earth, which is a relatively short distance on cosmic scale. To put it into perspective, our closest neighbor star, Proxima Centauri, is 4.2 light years away.

At a certain distance, supernovae can expose a planet with a long-lasting flux of cosmic radiation and destroy its atmosphere and these radiations likely brought significant changes on Earth’s biology.

To understand their effect on living organisms, researchers developed a computer model and investigated cosmic rays from the supernovae as they entered our atmosphere and reached the surface. Researchers know that a dramatic change in fossil record occurred during the Pliocene–Pleistocene boundary (2.5 million years ago), especially in Africa. The geologic record of that period also showed an elevated global concentration of iron-60, which is a radioactive isotope produced during a supernova.

“We are interested in how exploding stars affect life on Earth, and it turns out a few million years ago there were changes in the things that were living at the time. It might have been connected to this supernova.” Dr. Brian Thomas, an astrophysicist at Washburn University in Kansas said.

Although Pliocene–Pleistocene boundary was marked by no major mass extinction event, there was a change in the abundance of species and vegetation during that period. The boosted exposure to cosmic rays from a nearby supernova was likely responsible for the substantial effects on Earth’s atmosphere, specifically the ozone layer.

Researchers suggest that cosmic rays from supernovae would not destroy everything in their paths all at once. The intergalactic medium slows down the arrival of cosmic rays and continues to alter their interaction with Earth’s atmosphere over the course of hundreds of thousands of years. New model showed that ozone depletion peaked every 300 years after the initial particles from a supernova penetrated our atmosphere and this depleted ozone layer could be a concern for life on the surface.

Dr. Dimitra Atri, a computational physicist at the Blue Marble Space Institute of Science in Seattle says. “This work is an important step towards understanding the impact of nearby supernovae on our biosphere.”

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<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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