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A group of Australian researchers working in Antarctica have discovered star dust in freshly melted snow, discovering large amounts of a rare isotope called iron 60 that is not found in the world on Earth.
The study, published in the journal Physical Review Letters, made it possible to exclude any possibility of the presence of iron 60 in the snow, caused by human action, and revealed that it had been delivered to Earth by a type of rock in interstellar fall.
The most abundant element of the Earth is iron, but iron 60 contains four more neutrons than the well-known element. The experts argued that Iron 60 may be in the Earth's crust, but that its source could not be identical to the new discovery, as it was in the snow that had accumulated over the last few decades.
The team collected 500 kg of Antarctic snow around the Kohnen station, sent it to Munich, melted it and analyzed it. The solid components were separated from the melt water and treated with different chemical methods.
"Our analyzes have allowed us to exclude iron sources 60 from cosmic radiation, nuclear weapons tests or reactor accidents," says study author Dominik Koll. "Since there are no natural sources for this radioactive isotope on Earth, we knew that Iron 60 had to come from a supernova."
The site gave further clues about the origin of this isotope. The snow in which she was found was at most 20 years old, and the researchers felt that they could not come from far away in the cosmos, otherwise they would have dissipated.
"If the gas cloud hypothesis is correct, materials from ice cores over 40,000 years old will not contain interstellar iron-60," says Koll. "This would allow us to verify the transition from the solar system to the gas cloud – it would be a breakthrough for researchers working on the solar system environment."
The researchers said the source of Iron 60 should be a supernova, "not close enough to kill us, but not too far to be diluted in space," Koll explained. Particles were probably collected during the passage of the Earth through the local interstellar cloud, a space region of 30 light-years wide crossed by our solar system, he said.
Nevertheless, it is necessary to continue research to understand where and when Iron 60 arrived on Earth – its half-life of 2.6 million years – said Koll, will require more data and more cores. deeper ice to reach the older dust.
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