Washington DC
COSMIC rays from a nearby supernova triggered a mass extinction on Earth 2
million years ago, say researchers who have found the “smoking gun”.
In 1999, Klaus Knie and colleagues at the Technical University of Munich
discovered atoms of iron-60 in cores taken from the ocean floor. Iron-60 has a
half-life of just 1.5 million years, so the atoms must have formed recently in
geological terms.
Knie suggested that the iron was fallout from a nearby supernova about 2
million years ago—around the time many marine molluscs became extinct. But
astronomers did not know any star system…
