Iron-60 Discovered In Pacific Ocean Floor From Supernova, Not Micrometeorites

A supernova iron, the iron-60, was suggested to be found in sediment cores taken from the Pacific Ocean floor according to a team of researchers from Germany and Austria. The team describes the analysis of the core samples and explains the evidence they hold of an ancient supernova in a paper published in Proceedings of the National Academy of Sciences.

Iron-60 is extremely rare on this planet according to the researchers. It has a half-life of just over two and a half million years. This means that any iron-60 present just before the Earth was formed would have disappeared a long time ago.

Since there is no known natural means to produce the iron-60, the logical origin of this type of iron today would be the arrival from space, Phys. Org reported. Previous research has shown that micrometeorites and materials sent millions of miles across space due to a supernova may possibly be the sources of the iron.

The study started when one of the team members discovered an information about magnetotactic bacteria that lives in ocean sediments. This type of bacteria absorbs iron and as sediments build, the bacteria die and leave bits of iron behind the layers of the sediments. Since these sediment layers may have been built millions of years ago, it is possible that they contain a type of iron from space millions of years ago including the iron-60, Physics World reported.

The team of researchers obtained core samples taken from the Pacific Ocean and searched its content of iron-60. Among the more common iron-56 and other materials, the researchers used an accelerator mass that is capable of isolating single atoms. The team found the concentration levels of iron-60 from single atoms broken to small clusters of atoms. Findings show that the greatest concentrations were from a time approximately 2.2 million years ago, which coincides with a massive marine die-off.

The researchers hypothesize that the iron-60 is more likely from a supernova rather than micrometeorites. It is because micrometeorites tend to harbor iron in magnetite or silicate not from hydroxides, where magnetotactic bacteria absorb iron from.