Plain-looking, but important: Ferromanganese crusts collected by James Hein nearby Hawaii. [James Hein]
Posted on 12/16/2017 10:46:02 PM PST by SunkenCiv
Researchers then scoured the globe for thin layers of radioactive isotopes in rock strata and in 1999 struck figurative gold: Samples from beneath the ocean revealed some hard metallic layers, known as ferromanganese crusts that form slowly over millions of years, containing iron-60, an isotope with a half-life of 2.6 million years -- so short that the material must be much younger than Earth. The iron-60 was in a stratum laid down 2.2 million years ago. Similar layers of iron-60 have since been found elsewhere in the oceans. Astronomers have also been scouring the skies for groups of stars that could have created the blasts, with suspicion falling on two: the Scorpius-Centaurus (Sco-Cen) association, a group of more than 400 stars that would have been about 400 light-years away when the supernova occurred; and the Tucana-Horologium (Tuc-Hor) moving group which was 200 light-years away at the time.
However, the few iron-60 samples provide little information about the location of the offending supernova. In fact, in a paper posted on the arXiv.org preprint server yesterday, Ellis and colleagues argue that... Current samples "very tentatively favor" the Tuc-Hor group, Ellis says.
Today, however, Anton Wallner, a nuclear physicist at the Australian National University (ANU) in Canberra and colleagues report a new, much more detailed examination of iron-60 deposition around the globe and argue that Earth was exposed to a burst of multiple supernovae. Analyzing 120 ocean-floor samples from the Atlantic, Pacific, and Indian oceans, the team reports that iron-60 is detectable everywhere and that it doesn't seem to represent a single event, as the effected strata stretch from 1.7 million to 3.2 million years ago, as the researchers report today in Nature. "It suggests there were a series of supernovae, one after another," ...
(Excerpt) Read more at sciencemag.org ...
Plain-looking, but important: Ferromanganese crusts collected by James Hein nearby Hawaii. [James Hein]
p
my searches missed these:
Supernovae showered Earth with radioactive debris
Science Daily | 4/6/2016 | Australian National University
Posted on 04/06/2016 3:50:53 PM PDT by JimSEA
http://www.freerepublic.com/focus/chat/3418153/posts
Did a supernova two million years ago brighten the night sky and give our ancestors cancer?
Daily Mail | June 17, 2016 | Cheyenne Macdonald
Posted on 06/17/2016 4:22:29 PM PDT by rickmichaels
http://www.freerepublic.com/focus/chat/3441333/posts
related:
Explosions In Space May Have Initiated Ancient Extinction On Earth
Science Daily ^ | 4/12/05 | NASA/Goddard Space Flight Center
Posted on 04/12/2005 1:12:15 PM PDT by doc30
http://www.freerepublic.com/focus/news/1382310/posts
Supernova Storm Wiped Out Mammoths?
Discovery News | Sept. 28, 2005 | Jennifer Viegas
Posted on 10/17/2005 8:57:32 AM PDT by Fzob
http://freerepublic.com/focus/news/1503957/posts
“Similar Event Within 100 Light Years of Earth Would Be Catastrophic” —Astronomers...
The Daily Galaxy | 7/28/16
Posted on 07/28/2016 7:54:07 AM PDT by LibWhacker
http://www.freerepublic.com/focus/chat/3453933/posts
http://www.freerepublic.com/tag/supernova/index
Fried prehistoric Wooly Mammoths or Sabertooth Tiger nuggets.
Big, big container of ranch dip.
Interesting, tnx!
Thanks!
Iron 60 decays into Cobalt 60 (beta emission), which is pretty nasty stuff. The stuff that they would use as a jacket for a nuclear weapon if they wanted to sterilize a target. Fortunately it has a relatively short half-life and Iron 60 has a much longer half-life so Cobalt 60 is produced very slowly.
Thanks!
“... a series of supernovae, one after another..”
This is why advanced civilizations don’t live on the surfaces of planets, especially those located inside the bright region of the galaxy where there are neighboring stars which can create sterilizing events with a reach of hundreds of light years.
The vast majority of civilizations are probably completely virtual and hosted by computing complexes inside enormous shells built around red dwarfs (for energy) and moved to the dark outer fringes of the galaxy. Unless there is such a thing as free energy, in which case the red dwarf is optional.
Billions and billions of these shells are probably way out there in the darkness beyond the glowing section of the Milky Way, with their virtual civilizations safe from supernovas and magnetars and discovery by hostiles. The shells probably have no emissions or signature of any kind except for local gravity.
Obviously there has to be some non-virtual agencies which construct, maintain and program the computing complexes. Probably AIs and robots, from non-biological civilizations which very long ago “boot-loaded” from biological civilizations which are now extinct. We’re in the midst of the same process ourselves.
A non-biological civilization would no doubt exploit virtualization as the best way to make use of limited resources, in the same manner as we create a number of virtual servers inside one hardware server. So rather than exist as a planet of physical manufactured beings, a non-biological civilization would just build a big computer and everyone would live inside the software, in virtual form, while believing they are real beings living in a real world.
And the answer to the next logical question is probably...Yes. We ourselves are one of those virtual civilizations, by nearly insurmountable odds.
Thats the only signature of supernova blasts? How did the iron get under the ocean....shouldnt there be some on land? Or in recent uplifted mountain stratigraphic layers?
Great idea for a novel - Asimov led the way for it, but might make an interesting Sci-Fi read.....
There is some I’m sure, but it would be hard to find. Erosion would carry it into the sea.
It doesn't take that long, from an astronomical perspective, or even a geological perspective, to go from knapping stone blades to moving individual atoms using scanning tunnelling electron microscopes. Supernovae just don't happen often enough to keep civilizations from reaching advanced states. The main constraint for us is distance -- we don't yet have the technology for interstellar flight (interplanetary flight is possible but not practical); once that hurdle is behind, the next constraint is each other. We'll probably find a hair-trigger hostility just waiting for us to try our first steps.
Land material is “usually” one of two types: Exposed (upper surface few meters) that are very recent material (mountain building and upthrust eroded material), very-very old material (Canadian shield and Australian rocks 3.5 to 4 billion years old), or edges of faults and upthrusts exposing many layers from recent to medium (20,000 year to 65 million year old) ages. The Grand Canyon goes back hundreds of millions of years from surface to the depths, the dinosaur fossils in the Badlands of ND are exposing now rocks and fossils from 200 MYA, along with debris exposed tens of years ago. Finding that small layer of the right rock in the middle of the erosion before, during and after the assumed supernova is hard. Access to the rocks is easier. But two million years of deposits could be almost any thickness of material depending on your specific 100 foot location.
Ocean floor debris tends to be more slowly moving as sits still in the “mud” as the ocean floors separate. So mud and debris slowly accumulate on top, but the ocean abyssal plain is “nice and flat” over much of the earth. It makes studying this kind of effect a little easier.
“We’ll probably find a hair-trigger hostility just waiting for us to try our first steps.”
We already have, and it was triggered from going no farther than the moon.
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