An unexpected radioactive discovery beneath the Pacific Ocean seabed may provide researchers with a new global geologic time marker. According to a study published on February 10th in the journal Nature Communications, this previously unknown isotopic accumulation may be the result of cosmic disruptions caused by an ancient, near-Earth supernova.

Beryllium-10 is a radioactive isotope that is continuously produced by cosmic rays interacting with Earth's atmosphere. When it rains from the atmosphere and settles in the ocean, the isotope becomes incorporated into the extremely slow growth of some deep metal-rich crusts.

Earth must have experienced something exceptional 10 million years ago. Our study of rock samples from the floor of the Pacific Ocean has found a strange increase in the radioactive isotope beryllium