Search for Supernova $^{60}$Fe in the Earth's Fossil 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 $^{60}$Fe in a deep-sea ferromanganese crust. The signature for this supernova event should also reside in magnetite (Fe$_3$O$_4$) magnetofossils 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 60Fe fraction as $^{60}$Fe/Fe $= 3.6 \times 10^{-15}$. This value sits comfortably within the sensitivity limit of present accelerator mass spectrometry (AMS) capabilities. This talk will detail the present status of our $^{60}$Fe AMS search in magnetofossils and (possibly) show our initial results.