Supernova explosions may have influenced Earth’s evolutionary history.

Astrophysicists have taken a forensic approach to a cosmic mystery, tracing radioactive elements on the seafloor back to potential supernova explosions. Their findings suggest a possible link between these cosmic events and evolutionary changes in viruses within an African lake.

The key evidence is iron-60, a radioactive isotope found in significant amounts on the seafloor. Since iron-60 decays over time, any that originally formed with Earth would have long since disappeared. Therefore, its presence today points to a more recent source, likely supernova explosions that scattered it across the planet.

To determine its age, researchers at UC Santa Cruz analyzed the iron-60 deposits and found two distinct spikes—one about 2.5 million years ago and another around 6.5 million years ago. Suspecting a cosmic origin, they mapped Earth’s position relative to nearby stellar events over the past few million years.

Currently, the solar system sits inside the Local Bubble, a vast empty region thought to have been carved out by a series of supernovae 10 to 20 million years ago. In fact, Earth likely entered this bubble about 6 million years ago, passing through its outer boundary, where radiation would have been most intense. This, in turn, could explain the older iron-60 spike.

Tracing the Source: Nearby Supernova Likely Responsible for Recent Iron-60 Spike

The more recent and pronounced spike, in fact, appears to be the result of a nearby supernova. By reconstructing the past positions of stellar clusters, the team was able to identify two possible sources: the Tucana-Horologium cluster, which was about 228 light-years away at the time, and Upper Centaurus Lupus, located roughly 457 light-years away.

Furthermore, simulations suggest that the explosion would have exposed Earth to elevated cosmic radiation for up to 100,000 years. Consequently, this influx of high-energy radiation could have caused DNA damage, potentially leading to higher cancer rates or, alternatively, mutations that drive evolutionary changes.

Such radiation exposure can be harmful, possibly contributing to extinctions, as some researchers have proposed in the case of the Megalodon. However, mutations can also accelerate evolution, altering genetic material in ways that lead to the emergence of new traits.

Researchers explored potential biological effects of radiation and discovered a study on viral diversification in Lake Tanganyika 2-3 million years ago. Lead author Caitlyn Nojiri noted the similar timing, though no direct connection can be confirmed. Future research will investigate how cosmic radiation has shaped evolution, offering insights into the search for life on other planets.

Read Original Article: New Atlas

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