Traces of rare forms of iron and plutonium have been found at the bottom of the Pacific Ocean, after some kind of cataclysm in outer space created this radioactive stuff and sent it raining down on our planet.

The extraterrestrial debris arrived on Earth within the last 10 million years, according to a report in the journal Science. Once it hit the Pacific Ocean and settled to the bottom, nearly a mile down, the material got incorporated into layers of a rock that was later hauled up by a Japanese oil exploration company and donated to researchers. //

In his view, the new findings add to other evidence that the heaviest elements, such as plutonium, can't be generated by just regular old supernovas. "It must be some rare event, something else," says Schatz. "There are a lot of pieces of evidence that point to multiple sources. Neutron star mergers are probably one of the more important sources, but at this point it doesn't look like they can explain all the observations."