Supernova Left Its Mark In Ancient Bacteria 37
ananyo writes "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. Scientists have found the isotope iron-60, which does not form on Earth, in a sediment core from the eastern equatorial Pacific Ocean, dating to between about 1.7 million and 3.3 million years ago. The iron-60, which appears in layers dated to around 2.2 million years ago, could be the remains of magnetite 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."
One supernova of many in Local Bubble (Score:5, Informative)
Our solar system resides in an area of our galaxy called the "Local Bubble" [wikipedia.org], roughly a few hundred lightyears across. This region is very empty compared to the average interstellar medium in the galaxy, as a result of a large number of supernovae that blew out a sort of cavity in our interstellar neck of the woods long ago. In actual structure it's more of an irregular "Local Chimney" [solstation.com] going right through the galactic disc rather than a spherical bubble.
As a result, pinning the cause of TFA's observations to a single supernova is not all that simple, as supernovae were very common in the Sun's general neighborhood in our galactic past..
Here's a nice graphic of the larger features in and around our local bubble [nasa.gov]. It's a fascinating subject if you enjoy understanding our location in a galactic context.
Re:One supernova of many in Local Bubble (Score:2, Informative)
It's one of the few (to me) persuasive arguments that life might be quite rare
Rare? What are you talking about? The Earth gets blasted by supernovas, and all we get is some minor deposits in a geological layer. Not even a major extinction. Nothing.
I would say it shows that life is much more resilient than people think. And the Local Bubble just shows how common it must be.
If anything, I would not be surprised if there is active and viable life forms living underground on Mars. Atmosphere blown away? No problem! Just live underground. All life needs is some catalysts, chemicals and a temperature gradient keeping these chemicals in a proper state.