A nearby supernova explosion could destroy large animals millions of years ago.
Although the Earth is floating in the void, itnot in a vacuum. The planet is constantly bombarded with all sorts of things from space, including the daily flow of micrometeorites and the flow of radiation from the Sun and more distant stars. Sometimes things from space can cripple or kill us - remember that giant asteroid that destroyed the dinosaurs. More often star motes fall to the Earth and the Moon, and then peacefully settling, remaining buried until scientists uncover them.
If dark matter exists, it is more likelyall, belongs to the latter category. If hypothetical weakly interacting massive particles (wimps) are real, their collisions with ordinary matter can leave traces in the fossils in the depths of the earth’s rocks. Earlier we already wrote that a group of physicists proposed just such a way to search for dark matter.
But the search for space junk on Earth haslong story. Other scientists have demonstrated that fossil fossils of astrophysical particles can be found in the earth's crust. Some researchers reflect on how these cosmic events affect the Earth - because they could change the course of evolution. The new study suggests that the energy particles of an exploding star may have contributed to the extinction of many representatives of the megafauna, including the prehistoric monster - the megalodon shark, which died out at about the same time.
“An interesting coincidence,” says Adrian Melotte, an astrophysicist from the University of Kansas and author of the new work.
When a star dies, its guts fly apart.space. Among these stellar remnants are isotopes, or variants of elements such as iron. One of these isotopes, iron-60, is rarely found on Earth, but is abundant in supernovae. In 2016 and 2017, astrophysicists discovered iron-60 on the seabed of the Earth and on the Moon, and attributed its origin to two ancient supernovae in the galactic environs of the Earth. According to scientists, one event occurred about 2.6 million years ago, and another - from 6.5 to 8.7 million years ago.
"Many things would not have left a definite draft," says Melott. But iron-60 leaves. "This is a direct allusion to the incident."
Armed with such a hint, Melott turned toA question that scientists have been thinking about since the 1950s at a minimum: how could these supernovae affect the Earth and life here? In his new article, he describes how a supernova can produce a stream of subatomic particles — muons — that can damage DNA, leading to widespread mutations of organisms and even extinction of species.
Muons are a kind of super-heavy electrons. They can swim through the atmosphere of the Earth even easier than protons and electrons. "They fall to the ground, fall on you, some of them will interact with you and damage your DNA," says Melotte. "They are in an excellent position to influence terrestrial life."
Melotte suggested that the supernova is about 2.6a million years ago could increase the flux of muons flowing through the atmosphere several hundred times. Together with his colleagues, he calculated that the incidence of cancer could increase by 50% for animals the size of a man. Melotte says that for a mammoth or megalodon - which is about the size of a school bus - the radiation dose could be even worse.
The idea that supernovae can affect lifeon 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, the astronomers KD Terry and U.H. Tucker suggested that mass extinctions could have been caused by explosions of stars nearby, and since then this theory has been addressed several times.
However, most theories pose reasonsclimate change extinctions, not direct mutations. Supernova explosions can destroy the ozone layer of the Earth, which can damage 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," said Henrik Svensmark of the Technical University of Denmark.
The work of Svensmark shows that geologicalEarth data in some cases coincide with the expected flux of cosmic rays associated with a supernova. And in the work of 1995, physicists John Ellis and David Schramm came to the conclusion that catastrophic supernovae can be expected every few hundred million years in accordance with the rate of mass extinction.
As for the Melotte hypothesis thata single supernova 2.6 million years ago led directly to the extinction of the species, he cites several evidence. At the border of the Pliocene and Pleistocene 2.6 million years ago, about 36% of marine species became extinct, mostly in coastal waters. Larger animals should have caught a higher dose of muons in those regions.
But unlike iron-60 and wimps, muonspractically do not leave traces in the fossils, which makes a direct link between muons and extinctions almost impossible to prove. “These muons would leave no trace,” Melott says.
Even if torrents of muons and iron-60 from dyingstars can not be directly linked to extinction, their presence demonstrates a profound truth: the Earth, as well as everything on it, is also part of the universe. Stars can hold answers to the riddles of our destiny.
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The best place to search for dark matter can be the bowels of the Earth.