Nearby supernova could destroy large animals millions of years ago
Despite the fact that the earth floats in the void, it is not in a vacuum. The planet is constantly bombarded with all sorts of things from space, including a daily flow of micrometeorites and radiation flux of the Sun and more distant stars. Sometimes things from space can maim or kill us - think of the giant asteroid that wiped out the dinosaurs. Often stellar dust particles fall on the Earth and the Moon, and then peacefully settling, remaining buried as long as scientists do not dig them.
Supernova destroys species?
If dark matter exists, it is likely to fall into the latter category. If the hypothetical weakly interacting massive particles (WIMPs) are real, their collision with the conventional material may leave traces in fossils in the depths of the earth formations. Earlier we wrote that a group of physicists has proposed just such a way to search for dark matter.
But the search for debris in the world has a long history. Other scientists have demonstrated that it is possible to find fossils astrophysical particles in the Earth's crust. Some researchers speculate about how these cosmic events affect the Earth - they could change the course of evolution. A new study suggests that the energetic particles exploding stars may have contributed to the extinction of many representatives of megafauna, including prehistoric monster - Megalodon shark, which died out around the same time. "An interesting coincidence," said Adrian Melott, an astrophysicist at the University of Kansas and author of the new work.
When a star dies, its guts fly to outer space. Among these star residues are isotopes, or variants, of elements such as iron. One of these isotopes, iron-60, is rare on Earth but abundant present in supernovae. In 2016 and 2017 for Astrophysics have discovered iron-60 on the seabed of the Earth and the Moon, and attributed its origin to two ancient supernovae in the galactic vicinity of the earth. According to scientists, one event occurred at approximately 2, 6 million years ago, and the other - from 6, 5 to 8, 7 million years ago.
"A lot of things would have left a certain residue," said Melott. But the iron-60 leaves. "This is a direct allusion to the incident."
Armed with such a hint, Melott turned to the question on which scholars have speculated since the 1950s at least how these supernovae can affect the Earth and to life here? In his new article, he describes how a supernova can produce a stream of subatomic particle - muon - which can damage DNA, leading to widespread mutations of organisms and even to the extinction of species.
Muons is a kind of super-heavy electrons. They can swim more easily through the atmosphere than protons and electrons. "They fall to the ground, get on you, some of them will interact with you and damage your DNA," says Melott. "They are in a perfect position to influence the terrestrial life." Melott suggested that a supernova about 2 and 6 million years ago, could increase the flux of muons flowing through the atmosphere a few hundred times. He and his colleagues estimated that the incidence of cancer would be increased by 50% for the animals the size of the person. Melott says that the mammoth or Megalodon - which is the size of a school bus - the radiation dose could be even worse.
The idea that supernovae can influence life on Earth, is not something new. Paleontologist Otto Schindewolf back in the 1950s suggested that supernovae could cause mutations in large animals. But his theory has not gained popularity. In 1968, CDB astronomers KD Terry and William H. Tucker suggested that mass extinctions could have been caused by explosions of stars nearby, and since then this theory has been accessed several times.
However, most of the theories put the cause of extinction of climate change, rather than direct mutation. Explosions supernew may destroy the ozone layer, which may damage the marine plankton and coral reefs. Supernovae can also generate an excess of cosmic rays, which can lead to the formation of clouds, and they, in turn, to the "winter of cosmic rays," says Henrik Svensmark of the Technical University of Denmark.
Svensmark work shows that the geological data of the Earth in some cases coincide with the expected flux of cosmic rays associated with a supernova. And in the 1995 Physics John Ellis and David Schramm concluded that catastrophic supernovae can be expected every few hundred million years, according to the mass extinction rates. As for Melotta the hypothesis that a single supernova 2, 6 million years ago led directly to the loss of species, he gives some evidence. On the border of Pliocene and Pleistocene 2, 6 million years ago and became extinct about 36% of marine species, mainly in coastal waters. Larger animals had to catch the higher dose of muons in those regions.
But unlike iron-60 and WIMPs, muons left little trace in the fossil record, which makes a direct link between muons and extinction almost impossible to prove. "These muons would have left no trace," says Melott.
Even if the showers of muon and iron-60 from dying stars can not be directly linked to extinctions, their presence demonstrates a profound truth: The earth and all that is in it, too, is part of the universe. Stars can keep the answers to the puzzle of our destiny.
What do you think, whether we have an explosion of a supernova waiting and the subsequent extinction of species? Tell us in our chatting in a telegram.