Search for supernova-produced 60Fe in a marine sediment

TL;DR

This study investigates the presence of supernova-produced 60Fe in marine sediments to verify previous findings from FeMn crusts, finding no peak in sediments but confirming signals in crusts, raising questions about detection methods.

Contribution

The paper provides a direct measurement of 60Fe in marine sediments, challenging prior interpretations from FeMn crusts and discussing potential reasons for discrepancies.

Findings

No 60Fe peak detected in marine sediment from 1.7 to 3.2 Myr ago.

Confirmation of 60Fe signal in FeMn crusts using the same chemistry.

Discussion on possible causes for the discrepancy between sediment and crust measurements.

Abstract

An 60Fe peak in a deep-sea FeMn crust has been interpreted as due to the signature left by the ejecta of a supernova explosion close to the solar system 2.8 +/- 0.4 Myr ago [Knie et al., Phys. Rev. Lett. 93, 171103 (2004)]. To confirm this interpretation with better time resolution and obtain a more direct flux estimate, we measured 60Fe concentrations along a dated marine sediment. We find no 60Fe peak at the expected level from 1.7 to 3.2 Myr ago. However, applying the same chemistry used for the sediment, we confirm the 60Fe signal in the FeMn crust. The cause of the discrepancy is discussed.