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News item about Ordovician extinction

Phil

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Thanks Melissa,

Well, I'd always thought the Ordovician extinction was due to a global ice-age and widespread glaciation. I wonder if the two theories have been combined somehow? Maybe the gamma-ray burst could have triggered the ice-age in some way? Must try and find the whole text.

It's always fun to think of 'what if' scenarios. Imagine if there had been no Ordovician extinction? Would the giant orthoconic nautiloids have survived for much longer? Would the ammonoids have appeared? Hmm........
 

monty

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Phil said:
Well, I'd always thought the Ordovician extinction was due to a global ice-age and widespread glaciation. I wonder if the two theories have been combined somehow? Maybe the gamma-ray burst could have triggered the ice-age in some way? Must try and find the whole text.
Here's the full text:

http://xxx.arxiv.org/abs/astro-ph/0309415

This is the URL mentioned in the NASA press release. It has pretty pictures:

http://www.nasa.gov/vision/universe/starsgalaxies/gammaray_extinction.html

the first author's web page is

http://kusmos.phsx.ku.edu/~melott/Melott.html

It sounds like they believe that UV exposure caused the extinction, and there doesn't appear to be any notion of a correlated ice age (although I only read the conclusion section in detail).
 

Architeuthoceras

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From the NASA link

Dr. Bruce Lieberman, a paleontologist at the University of Kansas, originated the idea that a gamma-ray burst specifically could have caused the great Ordovician extinction, 200 million years before the dinosaurs. An ice age is thought to have caused this extinction. But a gamma-ray burst could have caused a fast die-out early on and also could have triggered the significant drop in surface temperature on Earth.
 

monty

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Architeuthoceras said:
From the NASA link
oops. I should've read a little more closely before posting... had to finish my taxes, though...:oops:
 
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Good paper, good hypothesis.

To piggyback on this paper, this is related to Carl Sagan's "nuclear winter" theory. In the book Cosmos, Sagan proposed that the dust scattered by high-yeild thermonuclear devices would lead to global cooling and a corresponding ice age. Now, while the dust by itself would remain for some time, Sagan went on to describe the conversion of atmospheric nitrogen into ozone-depleting oxides of Nitrogen (NOx) which would further scatter light and cool the Earth even more. The situation given here is less extreme (no nuclear bombs), but a nasty blow to a world dependent on photosynthesis and where a majority of your life is shallow water planktonic-dependent. We're talking a massive amount of devastation in a very short (geologically-speaking) amount of time.

This is a good hypothesis. Hmm... if it were within a 6000 ly distance, that would put it relatively in our neighborhood. Such a burst might be traced back to a supermassive start collapsing into a neutron star or black hole, both of which can be detected, even this long after the initial event. As far as local black holes are considered, the only one of which I know is Cygnus X-1, but that's a cool 11,000 light years from us. Neutron stars exist in decent numbers. But I'm only an amateur astronomer, so what do I know?

Its a good hypothesis. Any alternatives out there?

Thanks for the food for thought.

John
 

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