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Antarctic Blast Made Australia, Room For Dinosaurs
Agent Provocateur writes "Posted on the Science Daily site is a story from Ohio State University about a massive Antarctic blast that may have contributed to the Permian-Triassic extinction." From the article: "Its size and location -- in the Wilkes Land region of East Antarctica, south of Australia -- also suggest that it could have begun the breakup of the Gondwana supercontinent by creating the tectonic rift that pushed Australia northward. Scientists believe that the Permian-Triassic extinction paved the way for the dinosaurs to rise to prominence. The Wilkes Land crater is more than twice the size of the Chicxulub crater in the Yucatan peninsula, which marks the impact that may have ultimately killed the dinosaurs 65 million years ago. The Chicxulub meteor is thought to have been 6 miles wide, while the Wilkes Land meteor could have been up to 30 miles wide -- four or five times wider."
This is what always gets me about those Hollywood disaster movies. The BBC calls this The Day the Earth Nearly Died. And yet, as we can see, it didn't. Somehow, The Day After Tomorrow seems kind of pathetic in comparison.
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I'd tend to assume that any impact that size would be extremely unlikely to genreate the right conditions for the formation of life. We're talking about the kind of kinetic energy here that can boil oceans on impact, which would tend to foul up any chances of life emerging.
The conditions we currently think led to abiogenesis (the pre-evolutionary formation of life) weren't cataclysmic, they were merely improbably chemical reactions that might have arisen on the primordial earth - just a matter of something with a low probability having a few hundred million years to occur by chance in, in an environment with no pre-existing competeing lifeforms and plenty of potential habitat.
Now mind you, any major change in the ecology will open up new niches for creatures to evolve into, so in that sense an impact "creates new life", but that is exactly what the article is talking about. The mass die off precipitated by such an impact let the dinosaurs get started. The cretaceous die off got rid of the dinosaurs in turn, and let mammals take the top spot.
Erotic is when you use a feather. Exotic is when you use the whole chicken.
But the situation is much murkier with the Permian extinctions. Last I'd heard, we have yet to find clear evidence of an impact in the form of iridium, a dust layer or shocked quartz. So that sheds some doubt on the idea of an impact. Even if this is an impact crater, we don't know for certain that it dates to the time of the end-Permian mass extinctions: obviously, if it didn't occur at the same time as those extinctions, it couldn't have caused them. Given that the researchers are using radar and gravitometry, how do they know how old it is? You need to either do radiometric dating or look at the fossils to tell how old the underlying and overlying rocks are.
There is also some evidence that the Permian extinctions may have been drawn out, with several bouts of extinction occurring over the course of a million years or so, again that doesn't fit with an meteorite/comet impact. Anyhow, it might have been an impact, and it might not have been. It's still a mystery and probably will be for quite a while.
Indeed. The dating is completely arbitrary. All that we know is that it is not very old.
It may in fact end up being simultaneous with Chicxulub which by most recent estimates was not enough in itself to kill of the dinosaurs. Something else helped it.
So the "mummy dinosaur says to toddler dinosaur: what goes around comes around" joke will have to wait for now.
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The cretaceous die off got rid of the dinosaurs in turn, and let mammals take the top spot.
It wasn't quite like that. The die-off simply got rid of most large animals (probably the ones that couldn't burrow or hide in some way to avoid several hours of intense heat after the impact). Some small dinosaurs carried on fine - today we call them birds! Also, for some periods in wasn't mammals that took the top spot - large birds have often been the major predators. Things are far, far more interesting that suggested by this statement.
It's been done in the Arctic Ocean, Nature reported recently.
"The results are unexpected. Not only did the Arctic heat up to an extent that is inexplicable by current climate models, say the researchers, it also seems that the North Pole began to cool at about the same time as the Antarctic. This timing suggests that climate was being driven by a global factor, such as atmospheric levels of greenhouse gases, rather than something more local, such as geological upheaval."
I hope I didn't brain my damage.
I am jut a bit lost here, how do they use gravimetric data to say with the certainty the article seems to suggest that this is an impact crater?
As far as I know from my the few classes I have had on gravimetric data without the help of other data you are usually pretty lost. It would be very difficult to say how deep, what size and what weight anamoly the gravimetric anomily has and even more make out it's shape.
Furthermore with these gravimetric data taken from a satelite and not from the surface you get even more "meaned data" (less precise) being further away from the anamoly I can figure, of course they probably have a huge data set and also extremely precise instrumentation at the satelite in space, maybe that makes up for the distance in some ways, but for now I remain very sceptical.
Another thing that makes me wonder is why they don't talk about doing seismic or seismologic checks to confirm their theory. I actually thought that there was a few seismic stations places in this region, if this anamoly is as huge as the article suggests then I would think it should be pretty clearly visible in the seismic data.
Anyhow gravimetrics is certainly not my area of expertise. I would if someone out there is able to show me where I go wrong if that is the case, then I'd be grateful.
Slashdoters are technical sorts so I don't think it's too pendantic to note that a meteor is a flash of light caused by a meteorite.
Comparing the widths of the meteorites is a lot less interesting than realizing that the mass ratio is about 125:1. Actually I suspect that the mass was estimated first from the size of the crater and then the diameter calculated, converted from metric to American, and the word "diameter" changed to the more easily understood "width".
Nate
A couple of years ago an entirely different impact crater was discovered in Australia, with preliminary dating indicating that it happened at about the same time as this one. It, too, is huge -- not as monstrous as this here Antarctica sockdollager, but apparently about as apocalyptic as the one that reputedly KO'd the dinosaurs. Considering the history of our Solar System, I don't think that a multiple-impact armaggedon is at all out of the question. Hell, maybe we'll find even more impact craters, and have to come to the conclusion that it was some kind of supersized rain of fire that reset the planetary ecology switch.
And then, of course, we shouldn't forget about the largest volcanic eruption in the history of the planet that sparked up at just about the same time, too. An area roughly the size of Scandinavia simply melted into a mass of sulfurous, poisonous, volcanic goo for a couple of million years before settling down. I'm not terribly firm on my Permian Era geography, but I'd be willing to bet that the Siberian Traps event was pretty close to the opposite side of the planet at the time of the impacts.
Thus the "Siberian Traps", which formed at about the same time as the Permian Extinction. All we need to solidify that speculation is to study the positions of the continents at that time (not where they have drifted to, today).
I think the two areas were (approximately) at quadrature - 90 degrees apart, not in opposition.
More evidence for this sort of Double Disaster comes from the Chixulub impact, which, when it happened, it is known that India was on the opposite side of the world, and the "Deccan Traps" were formed at the same time as the K-T boundary.
Both the end Cretaceous extinctions and the Chixulub impact occurred after the start of the Deccan traps episode. Dinosaur skeletons (too complete to be re-worked bones) have been known from palaeosol horizons (literally ancient soil) between lava flows since the 1890s. Similarly, evidence of the Chixulub impact has been reported from between other lavas.
The "contre coup" theory of Large Igneous Province triggering doesn't get much support from my fellow geologists. It's theoretically possible, but no reasonable clear examples have been reported. Meanwhile a considerable number of examples of long-drawn-out internal processes leading to Large Igneous Province formation without extraterrestrial input have been documented.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"