How Supernovae affects Earth

According to Astrobio, two nearby supernovae that exploded about 2.5 and eight million years ago could have resulted in a staggered depletion of Earth’s ozone layer, leading to a variety of repercussions for life on Earth.

In particular, two-and-a-half million years ago the Earth was changing dramatically. The Pliocene, which was a hot and balmy epoch, was ending and the Pleistocene, an era of repeated glaciation known as the Ice Age, was beginning. Natural variations in Earth’s orbit and wobble likely accounted for the change in climate, but the simultaneous event of a supernova could provide insight on the diversification of life during this epoch.

This supernova is thought to have occurred between 163 and 326 light years away (50–100 parsecs) from Earth. For perspective, our closest stellar neighbor, Proxima Centauri, is 4.2 light years away.

Supernovae can sterilize any nearby inhabited planets that happen to be in the path of their harmful ionizing radiation. Could nearby supernovae wreak havoc on the existing biology of our planet? One researcher wanted to find out. Dr. Brian Thomas, an astrophysicist at Washburn University in Kansas, USA, modeled the biological impacts at the Earth’s surface, based on geologic evidence of nearby supernovae 2.5 million and 8 million years ago. In his latest paper, Thomas investigated cosmic rays from the supernovae as they propagated through our atmosphere to the surface, to understand their effect on living organisms,

Looking at the fossil record during the Pliocene–Pleistocene boundary (2.5 million years ago), we see a dramatic change in the fossil record and in land cover globally. Thomas tells Astrobiology Magazine that “there were changes, especially in Africa, which went from being more forested to more grassland.”

“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,” says Thomas. “It might have been connected to this supernova.”

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