Sediment in a deep-sea core may hold radioactive iron spewed by a distant supernova 2.2 million years ago and preserved in the fossilized remains of iron-loving bacteria. If confirmed, the iron traces would be the first biological signature of a specific exploding star.
Oceanic sediment contains an iron isotope that ancient bacteria accumulated 2.2 million years ago when debris rained on Earth from a supernova explosion. Shown are the remnants of a much younger supernova remnant, Cassiopeia A, shown in a composite image from three NASA observatories.
Shawn Bishop, a physicist at the Technical University of Munich in Germany, reported preliminary findings on 14 April at a meeting of the American Physical Society in Denver, Colorado.
In 2004, scientists reported finding the isotope iron-60, which does not form on Earth, in a piece of sea floor from the Pacific Ocean1. They calculated how long ago this radioactive isotope had arrived by using the rate at which it decays over time. The culprit, they concluded, was a supernova in the cosmic neighbourhood.
Bishop wondered if he could find signs of that explosion in the fossil record on Earth2. Some natural candidates are certain species of bacteria that gather iron from their environment to create 100-nanometre-wide magnetic crystals, which the microbes use to orient themselves within Earth’s magnetic field so that they can navigate to their preferred conditions. These 'magnetotactic' bacteria live in sea-floor sediments.
So Bishop and his colleagues acquired parts of a sediment core from the eastern equatorial Pacific Ocean, dating to between about 1.7 million and 3.3 million years ago. They took sediment samples from strata corresponding to periods roughly 100,000 years apart, and treated them with a chemical technique that extracts iron-60 but not iron from nonbiological sources, such as soil washing off the continents. The scientists then ran the samples through a mass spectrometer to see if any iron-60 was present.
And it was. “It looks like there’s something there,” Bishop told reporters at the Denver meeting. The levels of iron-60 are minuscule, but the only place they seem to appear is in layers dated to around 2.2 million years ago. This apparent signal of iron-60, Bishop said, could be the remains of magnetite (Fe3O4) chains formed by bacteria on the sea floor as radioactive supernova debris showered on them from the atmosphere, after crossing inter-stellar space at nearly the speed of light.
No one is sure what particular star might have exploded at this time, although one paper points to suspects in the Scorpius–Centaurus stellar association, at a distance of about 130 parsecs (424 light years) from the Sun3.
“I’m really excited about this,” says Brian Thomas, an astrophysicist at Washburn University in Topeka, Kansas, who was not involved in the work. “The nice thing is that it’s directly tied to a specific event.”“For me, philosophically, the charm is that this is sitting in the fossil record of our planet,” Bishop says. He and his team are now working on a second core, also from the Pacific, to see if it too holds the iron-60 signal.
Alexandra Witze | Nature
Breaking the optical bandwidth record of stable pulsed lasers
24.01.2017 | Institut national de la recherche scientifique - INRS
European XFEL prepares for user operation: Researchers can hand in first proposals for experiments
24.01.2017 | European XFEL GmbH
A Swedish-German team of researchers has cleared up a key process for the artificial production of silk. With the help of the intense X-rays from DESY's...
For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.
According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
24.01.2017 | Physics and Astronomy
24.01.2017 | Life Sciences
24.01.2017 | Health and Medicine