Supernovae spread radioactive fallout on Earth

Image: Supernova
An artist’s impression shows a supernova explosion in its prime. (Credit: Greg Stewart / SLAC)

Researchers say they’ve found evidence of supernova explosions that spewed radioactive fallout over Earth during the age when humanity’s ancestors were evolving into upright-walking, big-brained creatures.

One of two studies published in the journal Nature identifies deposits of radioactive iron-60 in deep-sea cores extracted from the bottom of the Indian, Pacific and Atlantic oceans. The deposits were traced back to one time frame ranging from 1.5 million to 3.2 million years ago, and another period 6.5 million to 8.7 million years ago.

The researchers behind that study, led by Anton Wallner of Australian National University, say the iron-60 was blasted toward us by “multiple supernova and massive-star events” that occurred within 325 light-years of Earth.

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By Alan Boyle

Mastermind of Cosmic Log, contributor to GeekWire and Universe Today, author of "The Case for Pluto: How a Little Planet Made a Big Difference," past president of the Council for the Advancement of Science Writing.

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