A Supernova Explosion Altered Virus Evolution 2.5 Million Years Ago
Along the East African Rift, Lake Tanganyika lies in isolation among towering mountains. The lake is more than 400 miles long and is the deepest lake on the continent.
It holds 16 percent of all the freshwater in the world. Around two to three million years ago, the number of viruses infecting fish in the lake saw a dramatic increase.
Researchers from the University of California, Santa Cruz, suggest that the sudden growth was triggered by the explosion of a distant star. The team analyzed iron isotopes to identify a 2.5-million-year-old supernova.
They linked the explosion to a surge of radiation that hit Earth around the same time and asserted that the blast was strong enough to break the DNA of living organisms, possibly causing the viruses in Lake Tanganyika to mutate into new species.
The researchers first examined iron-60, a radioactive form of iron produced by exploding stars, on the seafloor. They found that the iron-60 was of two different ages. Some had formed 2.5 million years ago, while others formed 6.5 million years ago.
Then, they traced the past movements of celestial bodies to determine the origin of the iron. Currently, our solar system is located in an open space called the Local Bubble.
About 6.5 million years ago, the Earth entered this bubble and passed through its exterior rich with stardust, which was how the older iron-60 made it onto the planet.
Between two and three million years ago, a nearby star exploded, spilling the newer radioactive iron onto our planet.
“The iron-60 is a way to trace back when the supernovae were occurring,” said Caitlyn Nojiri, a co-author of the study and a recent undergraduate student who is now applying for a Ph.D. in astrophysics. “From two to three million years ago, we think that a supernova happened nearby.”
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The team simulated what that supernova was like and discovered that it battered the Earth with cosmic rays for 100,000 years following the explosion.
The model clearly explained the previous spike in radiation on Earth around that time, solving a mystery that had stumped astronomers for years.
The supernova simulation raised other questions because the force of the cosmic rays was powerful enough to break DNA strands.
Since radiation can damage DNA, the event could have accelerated evolutionary changes or led to cell mutations.
The authors also studied virus diversity in one of Africa’s Rift Valley lakes and noticed that the timeframe for increased diversity in viruses lined up with when the supernova took place.
They cannot confirm if the events are connected, but it certainly is quite a coincidence. It just goes to show how something so far away can cause such a drastic effect here on Earth.
The details of the full study were published in Astrophysical Journal Letters.
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