Search for Supernova [sup 60]fe in the Earth's Microfossil Record

Approximately 2.8 Myr before the present our planet was subjected to the debris of a supernova explosion. The terrestrial proxy for this event was the discovery of live atoms of Fe-60 in a deep-sea ferromanganese crust. The signature for this supernova event should also reside in magnetite (Fe3O4) microfossils produced by magnetotactic bacteria extant at the time of the Earth-supernova interaction, provided the bacteria preferentially uptake iron from fine-grained iron oxides and ferric hydroxides. Using empirically derived microfossil concentrations in a deep-sea drill core, we deduce a conservative estimate of the Fe-60 fraction as Fe-60/Fe approximate to 3.6x10(-15). This value sits comfortably within the sensitivity limit of present accelerator mass spectrometry capabilities.