Bacteria Made Of Star Stuff

One of the best at explaining science was Carl Sagan. One recurring theme in Sagan’s works can be seen in the quote below:

And we who embody the local eyes and ears and thoughts and feelings of the cosmos we’ve begun, at last, to wonder about our origins. Star stuff, contemplating the stars organized collections of 10 billion-billion-billion atoms contemplating the evolution of matter tracing that long path by which it arrived at consciousness here on the planet Earth and perhaps, throughout the cosmos.

Or consider the video below:

The essence of the idea is pretty simple. The elements that compose are body were originally generated in stars and spread throughout the universe in a wide variety of fashions (see this wikipedia article on stellar evolution for more) so we are fundamentally connected to the universe in a rather intimate fashion. I bring this up because it has become more than a metaphor.

Science Daily has a press release concerning material presented at the meeting of the American Physical Society. From Science Daily:

In fossil remnants of iron-loving bacteria, researchers of the Cluster of Excellence Origin and Structure of the Universe at the Technische Universitaet Muenchen (TUM), found a radioactive iron isotope that they trace back to a supernova in our cosmic neighborhood. This is the first proven biological signature of a starburst on our Earth. The age determination of the deep-drill core from the Pacific Ocean showed that the supernova must have occurred about 2.2 million years ago, roughly around the time when the modern human developed.
Most of the chemical elements have their origin in core collapse supernovae. When a star ends its life in a gigantic starburst, it throws most of its mass into space. The radioactive iron isotope Fe-60 is produced almost exclusively in such supernovae. Because its half-life of 2.62 million years is short compared to the age of our solar system, no supernova iron should be present on Earth. Therefore, any discovery of Fe-60 on Earth would indicate a supernova in our cosmic neighborhood. In the year 2004, Fe-60 was discovered on Earth for the first time in a ferromanganese crust obtained from the floor of the equatorial Pacific Ocean. Its geological dating puts the event around 2.2 million years ago.

Researchers took cores dating from 3.3-1.7 mya and processed them to dissolve fossils from magnetotactic bacteria. From there they were able to extract FE-60. Again, from Science Daily:

Finally, using the ultra sensitive accelerator mass spectrometry system at the Maier Leibnitz Laboratory in Garching, Munich, they found a tantalizing hint of Iron-60 atoms occurring around 2.2 million years ago, which matches the expected time from the ferromanganese study. “It seems reasonable to suppose that the apparent signal of Fe-60 could be remains of magnetite chains formed by bacteria on the sea floor as a starburst showered on them from the atmosphere,” Shawn Bishop says. He and his team are now preparing to analyze a second sediment drill core, containing upwards of 10 times the amount of material as the first drill core, to see if it also holds the Fe-60 signal and, if it does, to map out the shape of the signal as a function of time.

See here for more.