Time resolved 2 million year old supernova activity discovered in Earth's microfossil record

TL;DR

This study detects a 60Fe isotope signal in Earth's microfossil record, indicating nearby supernova activity occurred between 2.8 and 1.7 million years ago, revealing a new method to trace cosmic events through sediment analysis.

Contribution

It introduces a novel approach using magnetofossils in ocean sediments to time-resolve supernova debris deposition over millions of years.

Findings

Detected a 60Fe signal between 2.8 and 1.7 million years ago.

Established a link between supernova activity and Earth's sediment record.

Demonstrated the use of magnetofossils as carriers of extraterrestrial isotopic signatures.

Abstract

Massive stars, which terminate their evolution as core collapse supernovae, are theoretically predicted to eject more than 1E-5 solar masses of the radioisotope 60Fe. If such an event occurs sufficiently close to our solar system, traces of the supernova debris could be deposited on Earth. Herein, we report a time resolved 60Fe signal residing, at least partially, in a biogenic reservoir. Using accelerator mass spectrometry, this signal was found through the direct detection of live 60Fe atoms contained within secondary iron oxides, among which are magnetofossils, the fossilized chains of magnetite crystals produced by magnetotactic bacteria. The magnetofossils were chemically extracted from two Pacific Ocean sediment drill cores. Our results show that the 60Fe signal onset occurs around 2.6 Ma to 2.8 Ma, near the lower Pleistocene boundary, terminates around 1.7 Ma, and peaks at about 2.2 Ma.