The exploding stars 2.6 million years ago may have contributed to the mass extinction event that swept the prehistoric oceans of the planet, wiping out creatures like the giant shark known as Megalodon, according to a new scientific article.
Cosmic particles from these supernovae have stuck the surface of the planet to such high levels, researchers at the University of Kansas say. They may have caused cancer in large marine organisms to spike.
Among the casualties was the megalodon – a shark the size of a bus – that disappeared from the fossil record during this period.
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The theory was led by a team led by Dr. Adrian Mutotte, a physicist at the University of Kansas, trying to join points between different strands of research.
"There really was not a good explanation for eliminating the maritime epidemic," he said. "It can be one, it's changing this paradigm – we know something happened and when it happened, then for the first time we really can dig and look things up in a definite way."
In order to arrive at this hypothesis, Dr. Malot was based on his knowledge of historical supernovae and evidence of their influence on Earth.
Ancient terrestrial antique iron-isotopes 60 – radioactive forms of iron – provided a crucial clue.
Publication of the findings in the journal Astrobiology, Dr. Motot argued that there was no other way for these materials to reach Earth except for a supernova, that is, they provided the "knock-off" evidence for these events.
Further support comes from the structure of the surrounding universe. Earth sits on the edge of something that called the local bubble – a vast area of hot, compressed gas that astronomers think is due to a series of supernova explosions – the explosion of stars that reached the end of their lives.
Due to the structure of this bubble, it is possible that the Earth could have been bathed in cosmic rays when the explosion had jumped on the ends, up to 100,000 years.
During this time, particles called muons were falling in large numbers on the surface of the earth.
Moons – basic particles like very heavy electrons – penetrate deep into living organisms, including humans, and are responsible for about a fifth of the dosage we receive.
Usually this is not a big problem, but with exposure of muon grown by hundreds of times Dr. Melott and his colleagues think it could lead to an increase in mutation rates and cancer.
Larger animals were particularly sensitive, as they would perceive a greater amount of radiation.
"We estimated that the cancer rate would rise by about 50 percent to something the size of a person – and the bigger it gets, the worse it will be," Dr. Melot said.
This could explain why Megalodon, as well as a third of the other large sea creatures, were unable to survive into the next period of the planet's history, known as the Pleistocene.
Previous work suggested supernovae around this time can also kill the small creatures vital to ocean health by damaging the ozone layer and allowing a surge of UV light inside.
Dr. Melotte said his work, which illustrates the effect of star explosions during this key period in Earth's history, was "another piece of a puzzle."
Often, mass extinction events are associated with dramatic changes in Earth's climate, such as the "Great Death" 252 million years ago, which resulted from soaring temperatures and oxygen levels falling in the oceans.
Although the cosmic rays to bomb the atmosphere may also be related to a changing climate, the authors of the study admit this "controversial claim".