For tens of millions of years whatonly the oceans of the Earth were not inhabited by giants: 2,200-pound turtles, sea cows the size of a whale, sharks, the size of a bus. But about 2.6 million years ago, they all began to die out en masse. Today this period is described as the extinction of the marine megafauna of the Pliocene. Then, over a short period, more than a third of incredible-sized living creatures, including the megalodon, a shark up to 25 meters long, died out. Scientists still can not understand what caused the incident.
According to the researchers, definitely one ofThe main factors were climate change. Started a new ice age. Ice displaced warm water, thereby reducing food reserves for large individuals. However, climate change may not be the only cause of what happened.
In the preprint of the article stored on the site arxiv.org and being prepared for publication in the first issue of the journal Astrobiology for 2019, the opinion is being taken that the most important factor contributing to the mass extinction of sea giants were exploding stars.
A group of scientists led by Adrian Melotta professor of physics and astronomy from the University of Kansas argues that the period of the beginning of the mass death of marine life on Earth coincides with the period of the appearance of a supernova or perhaps even a whole chain of small supernovae nearby. And if these explosions were really strong enough, then they could flood the Earth with their radiation and cause an increasing number of mutations and cancers of the fauna on our planet. Moreover, the process lasted several hundred years. And the bigger the animal was, say the researchers, the worse it was for him under the influence of so much radiation.
"We calculated that the likelihood of developing cancer ina living body the size of a man could increase to about 50 percent. And the more you are, the worse for you. For the same elephant or whale, the radiation dose would be even higher, ”Melott writes.
The basis of the assumption of Melott and his colleaguesA study of 2016, during which traces of the isotope of iron-60, a radioactive variant of iron with a half-life of about 2.6 million years, were found in ancient sediments of the seabed. If these radioactive isotopes were formed with the Earth, then “they would have been gone for a long time,” says Melotte. Thus, the only explanation for their presence on the planet is “outside bombardment” several million years ago.
Scientists who published their research in 2016year, they associate the detected isotopes with a series of supernova explosions that occurred 8.7-1.7 million years ago, approximately 325 light years from Earth. According to Melotte, supernovae flared up far enough to cause significant damage to our planet, but at the same time close enough to Earth so that it could be in the way of their residual radioactive radiation.
During star explosions, part of the discardedradiation could take the form of muons, which have a similar structure to electrons. However, the difference between them is huge. Muons are two hundred times more massive than electrons and are capable of penetrating far enough into the Earth hundreds of kilometers, and, of course, into the very depths of the oceans. Hence the theory arises that after the explosion of a star and after such a flow of muons hit our planet, the marine fauna could unwittingly come into contact with these radioactive particles that caused mutations and death of animals.
Cosmic radiation combined with otherknown factors, such as climate change, could be one of the reasons for the changes, which eventually dragged the sea migrants to the bottom. Melotte notes that the evidence for supernovae (or supernovae) near the Earth at that time is only “one of the pieces of the puzzle,” which will help solve the mystery of the extinction of sea monsters on Earth. Perhaps we will never know what exactly killed the megalodon, but while scientists are looking into the depths of the sea, it might also be worthwhile to turn their gaze to the stars.
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