Posted on 11/24/2004 1:22:08 PM PST by Phsstpok
Published online: 02 November 2004; | doi:10.1038/news041101-5
Supernova debris found on Earth
Mark Peplow
Ancient explosion may have affected climate and, possibly, human evolution.
Cosmic fallout from an exploding star dusted the Earth about 2.8 million years ago, and may have triggered a change in climate that affected the course of human evolution. The evidence comes from an unusual form of iron that was blasted through space by a supernova before eventually settling into the rocky crust beneath the Pacific Ocean.
Gunther Korschinek, a physicist from the Technical University of Munich in Germany, leads a team who in 1999 found the first deposits of supernova matter on Earth1. But it was impossible to date the supernova accurately from those samples, because the material was distributed through several different layers of rock.
The team has now analysed a different piece of ocean crust, where the supernova detritus is concentrated into a clear band of rock that can be accurately dated. The researchers found small but significant amounts of an isotope called iron-60 in the rock, which could only have come from a supernova.
"We've looked at all the possibilities and we can't find anything else that could produce such quantities," Korschinek says. The researchers report their results in the latest issue of Physical Review Letters2.
"It represents an experimental triumph and a milestone in this field," says Brian Fields, an astrophysicist from University of Illinois at Urbana-Champaign. He argues that the result marks the birth of a completely new area of research, which he calls "supernova archaeology"3.
Close shave
Comets and meteorites also deliver matter to Earth, but they always come from within our Solar System. Supernovae are the only known source of interstellar debris. "The very fact that a supernova can dump material on the Earth is, to my mind, rather spectacular. It demonstrates that the Earth is not independent of its cosmic environment," says Fields.
When the iron-60 arrived from space, it was evenly distributed all over the Earth. But the signatures are only detectable in crust that has lain undisturbed for millions of years, such as certain parts of the Pacific Ocean floor. This particular crust was taken from an area a few hundred kilometres southeast of the Hawaiian Islands in 1980. It was collected by oceanographers who were investigating the rocks as a potential source of rare mineral ores.
Korschinek estimates that the supernova was between about 100 and 200 light years away and happened 2.8 million years ago, give or take 300,000 years. The explosion can't have been too close to Earth, or it would have delivered enough radiation to cause mass extinctions. Conversely, if the supernova was any further away, more of the iron-60 would have been filtered out by the thin wisps of matter drifting between the stars.
Cooling rays
This means the supernova would have been at the right distance to spray out a stream of cosmic rays that could have increased the cloud cover on Earth. Korschinek calculates that there may have been 15% more cosmic rays arriving on Earth than normal for at least 100,000 years. This is not enough to actually kill anything, but was perhaps sufficient to change the Earth's climate.
The increase in cloudiness would have cooled the surface, tying up water as ice at the poles and leading to a dryer climate in Africa. Climate records in rock cores match the dates of the supernova event.
"Some people believe this climate change in Africa was a driving force in our own evolution," adds Korschinek. The argument is that a drier climate in the continent would have forced humans to adapt4, and to spread out to other, wetter areas.
The team is now looking for other unusual isotopes in the crust sample, which may reveal more about the type of star that caused the supernova. But there are probably 10,000 times fewer of these atoms than of the iron-60, says Korschinek, so they will be extremely difficult to measure. "We're sweating, and I don't know if we will succeed," he says.
Actually, many elements are formed in stars long before they go nova or supernova. Once hydrogen fuel is depleted, stars start fusing helium into carbon and oxygen, then those elements are subsequently fused into even heavier elements such as nitrogen and silicon, finally culminating in iron. All elements heavier than iron are formed in supernova explosions. The fact that Earth is rich in those heavy elements is proof that the primordial dust cloud of our solar system was enriched by supernova explosions, which also probably started the initial gravitational collapse of the dust cloud.
Yeah, These are the same guys that interpret the constitution to BAN GOD from the public discourse!
I have always been under impression that EARTH itself was Supernova Debris.
You know, creationists have been claiming the death of evolution for more than a century now. I guess y'all assume you might be right one day.
Tens of thousands of biologists are not holding their breaths, however.
"Impossible! The earth is only 3,000 years old.< /creationism >"
Creationism is a much wider field and encompasses far more views and theories than that. Earth being changed to become more receptive to human life as a result of super nova matter distribution could fall into both progressive and theistic views of Creationism.
The Imminent Demise of Evolution. (The endless crisis.)
It wasn't really a Supernova it was 69' Nova SS with a 454. At 5500 rpm a rod went through the side of the block, allowing some pieces of cast iron, Valvoline 20-50w and Prestone Anti-freeze to be expelled into the atmospere and along the side of the road. Also causing a noticable decrease in forward velocity. But no scientific facts of change in human evolution, except maybe on not using old connecting rods in a high h.p. engine.
..predicting the past is no trick.
Just need to know the bias of who's doing the 'predicting' of what has already happened.
The curve of binding energy. :-)
Sorry if I misrepresented the creationist viewpoint.
I was trying to be funny. (Dang, failed again!)
Anyway, I believe the Bible. God did it!
Supergiant stars have short life in cosmic terms, like 100 million years. Smaller the star, the longer itn will live because it is burning less fuel. It is likely that billions of years ago, there were supernovas not too far from our Solar System. When supergian stars exploded, they produce heavy elements like iron to uranium. When stars have iron appearing, it is sign it will start to die and go supernova. If a supernova happened near us, we would be bombarded with deadly gamma and cosmic rays. It would kill almost all life on this planet.
Not exactly true, (other than the man-made elements) there are fusions that create elements
just above iron, but obviously a pittance compared to iron.
I agree. It is impossible to date anything with any type of isotope unless you have something that you can prove was made at the date you are looking at. A million years, a billion years or 50 years... it does not make any difference unless you already have a sample that was also made at that time. This is all intellectual BS.
I think ancient SUV debris was also found in the rock layers.
The fusion of iron consumes more energy than it releases, so it doesn't occur except in the case of supernova explosions, with their enormous neutron flux bombarding iron atoms to form heavier elements.
I've heard that heavier elements can form in the accretion disks of black holes, but that's the exception that proves the rule.
What where you referring to?
Beef eating SUV owners.
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