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Supernovae May Explain Mass Extinctions of Marine Animals During Pliocene Era (theregister.co.uk)
"The Register has an article on the possibility that a supernova or a series of them could explain a mass die-off of marine animals around 2.6 million years ago," writes Slashdot reader KindMind. From the report: A gigantic supernova explosion may have triggered mass extinctions for creatures living in Earth's prehistoric oceans some 2.6 million years ago, according to new research published in Astrobiology. Marine animals like the megalodon [...] suddenly disappeared during the late Pliocene. Around the same time, scientists [...] noticed a peak in the iron-60 isotope in ancient seabeds. "As far back as the mid-1990s, people said, "Hey, look for iron-60. It's a telltale because there's no other way for it to get to Earth but from a supernova.' Because iron-60 is radioactive, if it was formed with the Earth it would be long gone by now. So, it had to have been rained down on us" explained Adrian Melott, lead author of the paper and a physics and astronomy professor at the University of Kansas.
The team believes that a supernova located 150 light years away set of a chain of supernovae bursts and covered the Earth in a shroud of deadly cosmic ray radiation. This was amplified, Melott said, because the Solar System is right on the edge of an area of the interstellar medium called the Local Bubble. The Local Bubble extends about 300 light years across and contains the two main clouds of dust and gas: Local Interstellar Cloud and the G-Cloud. As the supernovae ejected cosmic rays, these beams of energetic particles would have repeatedly bounced off the clouds to create a "cosmic-ray bath" that could have lasted 10,000 to 100,000 years. Some of that radiation such as cosmic ray muons would have leaked onto Earth, and over time it could have led to genetic mutations and cancers [that would have caused animals like the megalodon to die off prematurely].
The team believes that a supernova located 150 light years away set of a chain of supernovae bursts and covered the Earth in a shroud of deadly cosmic ray radiation. This was amplified, Melott said, because the Solar System is right on the edge of an area of the interstellar medium called the Local Bubble. The Local Bubble extends about 300 light years across and contains the two main clouds of dust and gas: Local Interstellar Cloud and the G-Cloud. As the supernovae ejected cosmic rays, these beams of energetic particles would have repeatedly bounced off the clouds to create a "cosmic-ray bath" that could have lasted 10,000 to 100,000 years. Some of that radiation such as cosmic ray muons would have leaked onto Earth, and over time it could have led to genetic mutations and cancers [that would have caused animals like the megalodon to die off prematurely].
Bob: Er, so that other stuff over there ... how do you know that didn't rain down on us?.
Joe: I hate you.
Seriously?
Location in strata, total amount, distrbution with other elements.
But your Iron-60....
Okay, a layer of a specific element is found in a thin layer of sediment that isn't found elsewhere. You can then try to figure where it might have come from. Iron is a good candidate for a supernova, because Iron creation is the end of the fusion process right before a star goes supernova.
The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.