The Mother Of All Impacts

dragon04 · Jun 1, 2006

Giant Crater Found: Tied to Worst Mass Extinction Ever By Robert Roy Britt Senior Science Writer posted: 01 June 2006 06:07 pm ET An apparent crater as big as Ohio has been found in Antarctica. Scientists think it was carved by a space rock that caused the greatest mass extinction on Earth, 250 million years ago. The crater, buried beneath a half-mile of ice and discovered by some serious airborne and satellite sleuthing, is more than twice as big as the one involved in the demise of the dinosaurs. The crater's location, in the Wilkes Land region of East Antarctica, south of Australia, suggests it might have instigated the breakup of the so-called Gondwana supercontinent, which pushed Australia northward, the researchers said. "This Wilkes Land impact is much bigger than the impact that killed the dinosaurs, and probably would have caused catastrophic damage at the time," said Ralph von Frese, a professor of geological sciences at Ohio State University. http://www.space.com/scienceastronomy/060601_big_crater.html <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

doubletruncation · Jun 2, 2006

It's a very interesting article. Any ideas on how they figure that it occurred 250 mya? Is it just that people have been looking for giant craters to explain the P-T extinction, and here they find one so it's hypothesized to be the cause of that event? <div class="Discussion_UserSignature"> </div>

JonClarke · Jun 2, 2006

This is very, very, very iffy! Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

spacefire · Jun 2, 2006

we get hit periodically. hopefully the meteor that killed the dynosaurs was the last one as we shall soon acquire the technological prowess to deflect asteroids. <div class="Discussion_UserSignature"> http://asteroid-invasion.blogspot.comhttp://www.solvengineer.com/asteroid-invasion.html </div>

harmonicaman · Jun 2, 2006

Doubletruncation - I think you've made a really good point! They seem to be dating this crater not by an actual examination of it's age, but by matching it too an apparent extinction event! There's a good chance that they are correct, but I agree that they are just making an educated guess. I would be more confident of the crater's actual connection to a known event if we had real measurements of its age... They are kind of putting the cart before the horse here.

silylene old · Jun 2, 2006

Very interesting, but I am going to wait for core samples. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

JonClarke · Jun 2, 2006

We don't even know it's a crater yet, just a large gravity anomaly and a vague circiular feature on radar. And people are linking to the P-T extinction, for which there is no good evidence for an impact. While drilling under ice for samples is too much to expect at this stage, where is the magnetic and seismic data for this being an impact? Where is the ejecta horizon? Lots of things are roughly circular in radar images, and GRACE is a notoriously blunt instrument. Jon This is science by pres release. Where is Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

yevaud · Jun 2, 2006

Just for the hell of it, I did some back of the envelope calculations (it's good to crack the old books from time to time). I assumed it to be some form of porous material, not ice (for no particular reason), an impact velocity of 17 km/sec (typical of an asteroidal impact), and assumed an impact angle of 45 degrees (again, no particular reason). The collision, if it really took place, struck with the energy of around 8*10^7 megatons (e.g., 3.4 *10^23 Joules). *Whew* <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

JonClarke · Jun 2, 2006

Douglas Adams might say the best bang since the big one! <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

CalliArcale · Jun 5, 2006

I agree; this seems very premature. There was another possible mega-crater discovery in the ocean somewhere (Indian, IIRC) to which the discoverers attributed the Permian extinction event. But that faded from the press awfully quickly; I suspect it was equally premature. There's less to go on than at Chixulub, at least so far. I'll wait and see. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

silylene old · Jun 5, 2006

Also, what evidence do they have that led them to the age of this proposed impact? Even if it is an impact crater, I am puzzled how they arrived at a date of 250M years ago at the Permian extinction (other than they knew an extinction occured then). <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

dragon04 · Jun 5, 2006

I just found it interesting. I found it a bit premature, but it makes one wonder just what other secrets may be locked up beneath the Antarctic ice. I fancy Antarctica as a geological time capsule. <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

grovesy · Jun 6, 2006

There is supposebly another meteorite with a diameter of more than 1000 km, is heading towards earth and is estimated to hit in 2048.

mikeemmert · Jun 6, 2006

The problem with this hypothesis is that there is no large worldwide iridium anomaly around the time of the Permian-Triassic extinction. And they have certainly looked after the Alvarez discovery about the K-T boundary clay. It seems this crater is under a considerable amount of ice. That's unfortunate, since it will make it hard to investigate. The absence of iridium for the P-T event makes it important to pin down exactly what this thing in Antarctica is. Allow me to express just a little bit of healthy skepticism here. I haven't seen the raw data.

earthseed · Jun 6, 2006

The pattern of extinction at the end of the Permian does not match what one would expect from an impact. There were two waves of extinction, and they took millions of years. There is already a "smoking gun" in the massive Siberian Traps, which covered an area of "just under 2 million square kilometres which is an area greater than that of Europe. Estimates of the original volume of the traps range from 1 million cubic km up to 4 million cubic km." I share the skepticism of this hypthesis. Time will tell.

astroguard · Jun 6, 2006

<blockquote>In reply to:<hr />CalliArcale wrote: There was another possible mega-crater discovery in the ocean somewhere (Indian, IIRC) to which the discoverers attributed the Permian extinction event.<hr /></blockquote>That was Bedout Crater off the northern shore of Western Australia. There were some initial objections to it being categorised as an impact (rather than volcanic) crater, but those appear to have been dismissed satisfactorily.

mikeemmert · Jun 6, 2006

Hi, earthseed, this weekend I was kindly provided with a copy of the June, 2006 Scientific American, which had an article on "Supervolcanoes". They were specifically discussing Yellowstone National Park and Long Valley, California. The ash release in these events was about 750-1000 km^3 (compared to Mt. St. Helens' 1/2 km^3), obviously less than the Siberian Traps. These American supervolcanoes caused extinctions within about 180 km of the events. Life (for the Yellowstone event) was severely stressed as far away as Texas. Much of this has been known since the 1950's. What's new in this month's analysis was that they were able to determine the global effects from analysis of the oxygen-17 content of certain deposits. These events severly depleted the ozone layer - but life survived. Apparently organisms resist ultraviolet light much better than was once believed. The article concluded that, one, this particular kind of event will probably not happen in our lifetimes, and two, that the eruptions in Yellowstone and Long Valley did not cause mass extinctions. But the Siberian Traps and Deccan Traps were three orders of magnitude larger. Because time has been eating away the evidence from the P-T extinction event, not much is known about it. Sea level receded several hundred meters and, more importantly, the oxygen content of the atmosphere was reduced from 36% (higher than today's 21%) to as little as 6%, making the air nearly as low in oxygen as that in the Himalayas today. The P-T event is the only mass extinction that took out large numbers of insects.<blockquote>In reply to:<hr />There is already a "smoking gun" in the massive Siberian Traps<hr /></blockquote>Well, that gun's pretty hot, I'll allow, but it ain't smokin yet. I would like to see a better chain of evidence. The investigation of the Permian-Triassic extinction is by no means over. I tend to believe the Siberian Traps t

dragon04 · Jun 7, 2006

The problem with this hypothesis is that there is no large worldwide iridium anomaly around the time of the Permian-Triassic extinction. Very good point. Doesn't rule out a cometary impct though, correct? Couldn't it also be the mother of all calderas? I'm thinking in terms of the Yellowstone Basin. However, I don't know if the geology of antarctica would lend to or dispute such a theory. <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

JonClarke · Jun 7, 2006

That part of Antarctica is, I think, largely high grade metamorphic terrains. Not a good place to find calderas. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

earthseed · Jun 7, 2006

Wikipedia does a good job covering the end Permian extinction. They even discuss the supposed Antarctic impact. The estimated age of between 100 and 500 million years ago does not add to my confidence in this theory. They also mention a methane hydrate release. That get used to explain everything, with no evidence ever provided. A warming of 5 degrees did not cause a serious mass extinction during the Paleocene Eocene Thermal Maximum, so why should it (if it happened at all) in the Permian? By the way, there is some doubt that the PETM was caused by methane, as is commonly assumed. The only cause they missed was dark matter clumps, probably for good reason.

mikeemmert · Jun 9, 2006

...(mikeemmert) there is no large worldwide iridium anomaly around the time of the Permian-Triassic extinction. Dragon04 <blockquote>In reply to:<hr /> Doesn't rule out a cometary impct though, correct?<hr /></blockquote>Well...actually, yeah, it does, if this is a crater the size of Ohio. Asteroidal and cometary material start out with a "chronditic" mixture. Take all teh elements in the Sun and subtract all the helium and that hydrogen not in compounds like water or methane or ammonia or etc. Objects from the outer solar system have this mixture. Those from the inner solar system have this mixture minus water, methane, and ammonia and etc., anything that boils off. Iridium (+gold, platinum, etc.) is present in both asteroids and comets. Although a smaller percentage of a comet, it is still significant and is far more than enough to leave an easily detectable tracer for a crater the size of Ohio.

yevaud · Jun 9, 2006

Ørsted verifies regional magnetic anomalies of the Antarctic lithosphere Abstract Initial magnetic measurements from the Ørsted satellite reveal lithospheric anomalies over the Antarctic that are similar to those obtained by Magsat. Accordingly, lithospheric anomalies can be extracted from the Ørsted data, despite the much greater operational altitude of Ørsted (650–865 km) relative to Magsat (350–550 km). Furthermore, these correspondences confirm the lithospheric origins for the resulting small-amplitude anomalies in the satellite data. In studies of the Antarctic lithosphere, the Magsat data particularly were limited by the large relative uncertainties of their lithospheric components. These uncertainties occurred because the short nearly seven-month mission more than 20 years ago collected data over austral high summer and early fall when the contaminating large-amplitude external field effects were at a maximum. Therefore, the recent and more numerous Ørsted measurements greatly facilitate our efforts to separate effectively the core, lithospheric, and external field components for enhanced studies of the Antarctic lithosphere. Published 3 August 2002. American Geophysical Union This picture from a Boston Globe article denotes Antartica. Thicker ice sheets are represented by red; thinner in blue/green/yellow. The crater in question is in the bottom right, circled. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

The Mother Of All Impacts

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