Detecting Supernova Dust on the Earth's Sea Floor with AMS

An ⁶⁰Fe anomaly was detected with accelerator mass spectrometry (AMS) - a very sensitive method to measure extremely low isotopic ratios - in a 2 Myr old layer of a ferromanganese crust (Knie et al., 2004). This signal is assumed to be of supernova origin and might be linked to the observation of our solar system being located in a Region of thin, hot interstellar medium. This region, called the Local Bubble, was presumably formed by multiple supernova explosions starting 14 Myr ago. Calculations suggest that at least one of these supernovae occured close enough to the solar system to leave a detectable ⁶⁰Fe trace on Earth.
New AMS measurements are performed in deep-sea sediments from the Pacific Ocean. An international collaboration of different AMS facilities searches for signatures of the long-lived radionuclides ²⁶Al, ⁵³Mn, and ⁶⁰Fe in a time range from 1.7 to 3.1 Myr. Magnetostratigraphic dating of the samples is confirmed by measurements of the cosmogenic radionuclide ¹⁰Be. All ¹⁰Be and ²⁶Al measurements are finished, ⁵³Mn and ⁶⁰Fe is in progress. First results will be presented and discussed.