Search for Supernova 60Fe in the Fossil Record

Cosmic production sites for substantial amounts of 60Fe are limited to two: Type II core collapse supernovae, the death throes of massive stars; and carbon-deflagration Type Ia supernovae, which are the result of the complete disruption of a carbon-oxygen white dwarf having exceeded the Chandrasekhar mass limit. Stellar models predict both sites can produce up to 10-4 solar masses of 60Fe; while gamma-ray astronomy studies, viewing the inner portion of our Galaxy known to harbour massive stars, have detected the two characteristic gamma-rays of 60Fe ß-decay. Thus, 60Fe is a proxy for supernova events. Its existence on Earth was previously discovered at the Munich universities’ Maier-Leibnitz-Laboratory, using accelerator mass spectrometry (AMS), in a deep-sea ferromanganese crust, implicating a past interaction of the Earth with the debris of a nearby supernova. We have obtained a deep sea drill core with sufficient quantities of iron-bearing microfossils that, themselves, should also contain the signature of this supernova event. We propose to search for live 60Fe atoms in these microfossils using AMS at the Maier-Leibnitz laboratory, Garching. Discovery of 60Fe in this reservoir would help further constrain the received terrestrial 60Fe flux and mark the first time a cosmic event has been discovered in the fossil record.

DFG Programme Research Grants