About 360 million years ago, an immense mass extinction decimated about 50% of all genera of living beings and marked the end of the Devonian period. It was one of the five great extinctions in the history of our planet, but its exact cause is still unknown.
A new study, led by astrophysicist Brian Fields of the University of Illinois at Urbana-Champaign, USA, raises an intriguing possibility: the cause would be the explosion of a star, a supernova.
Supernovae are the most intense explosions in the known universe. For a moment, about a week, they become billions of times brighter than our Sun. In addition to spreading chemical elements throughout the universe, they emit a large amount of radiation, in the form of visible light, X-rays and ultraviolet rays, which they can have serious consequences for any biosphere that is unlucky enough to be too close.
Trilobites were some of the animals that inhabited Earth in the late Devonian. Source: Ars Technica
Fields and his team suggest that a dramatic drop in the ozone level in the Earth’s atmosphere, which coincides with the extinction at the end of the Devonian, was caused by the effects of radiation emitted by a supernova 65 light years from us.
Since the 1950s, scientists have speculated that supernovae may cause mass extinctions, with a “lethal radius” of about 25 light years. But the study suggests that even more distant stars can have damaging effects on life on Earth, both instantaneous and long term.
“Supernovae are immediate sources of ionizing radiation, in the form of extreme ultraviolet, x-rays and gamma rays,” says the article. “But on larger timescales, the interaction of the explosion with the gas around the star generates a shock wave that accelerates elementary particles, producing cosmic rays. These particles are magnetically confined to the remains of the supernova, and should bathe the Earth for about 100 thousand years “, says the team.
Supernova remnant in the crab nebula. Source: Nasa / Hubble Space Telescope
These cosmic rays would be intense enough to destroy the ozone layer, causing lasting damage, due to radiation, to life forms within the terrestrial biosphere. What has paralleled the loss of diversity and deformation of plant spores in fossils on the border of the Devonian and Carbonfero periods, some 360 million years ago.
One way of proving the theory would be to find elements of elements such as plutnium-244 and samrio-146. “None of these isotopes occur naturally on Earth today, and the only way they get here is by cosmic explosions.
Source: Science Alert