Ancient Supernova Caused Mass Extinction On Earth, Scientists Believe
Once upon a time, hundreds of millions of years ago, a nearby supernova may have caused a mass extinction on Earth.
We’ve all heard of the giant asteroid wiping out the dinosaurs around 66 million years ago. However, let’s go a bit further back – namely, to the end of the Devonian period, around 359 million years ago.
While us folks in the modern-day have yet to face Armageddon or the galactic pelt of a star exploding, previous Earthlings may have endured a much harsher, scarier fate.
A new study, published in the Proceedings of the National Academy of Sciences, posits a frightening history: a single supernova, or even multiple, sending Earth’s beings on course to extinction.
This wouldn’t have been like the immediate blast radius of a nuke, incinerating all who dare to be in its path. No, this is much worse; while Earth would be beyond the ‘kill distance’, the rippling shockwaves from the exploding star, or stars, would cause catastrophic damage to Earth’s atmosphere.
Brian Fields, a physicist at University of Illinois, Urbana-Champaign, who led the study, told Vice:
Of course, it is irresistible to ask what it would look like if you were lucky/unlucky enough to see it. At its brightest, it would be putting out more light than the Full Moon. The light of the Moon is spread over the face of the Moon, so it’s not a point in the sky. But the supernova would be this very concentrated dot of bright light.
Humans weren’t even close to being around at this time – they first walked the Earth around six million years ago – but around 70% of living species were killed off in this particular mass extinction.
The study explains that the impact of the supernova, emitting gamma rays and ultraviolet light, could have damaged our protective ozone layer and inevitably enabled radiation to reach ecosystems on the planet’s surface. Cosmic rays can damage genetic material, as well as increasing the odds of developing diseases like cancer, hence the need for a good ozone layer.
Discussing the likelihood of multiple supernovae, Fields added:
Massive stars are incredibly social. What we’re suggesting is that since massive stars are born in clusters, if one hits you, it’s entirely possible or even likely that another one will hit you. So maybe multiple of these punctuated extinction events at the end of the Devonian could be due to supernovae.
While the signature of a supernova has previously been detected in radioactive isotopes in the seafloor, which may have contributed to the extinction of the Megalodon shark, finding such atoms dating back to Devonian times will be a ‘tall order’, according to Fields.
Fields added: ‘I’m of the school that people can be surprisingly clever, so even if something sounds very hard, it’s better to suggest it and see if someone can be clever than not mention it. That’s the spirit with which we’re writing this.’
If, somehow, scientists managed to detect isotopes – specifically, plutonium-244 and samarium-146 – in ancient samples, it would enlighten the field of both astrophysics, geology and human history.
However, while there seems to be mention of an ‘extinction-level’ meteor every week, Fields said ‘there are no threatening supernova candidates anywhere near us now’.
He added: ‘That’s a super important point. I’m not trying to add to the misery of 2020. If you care about your descendants, then you need to worry about it on million-year timescales. But not today.’
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Proceedings of the National Academy of Sciences