asteroid impact

Asteroids

Scientists Come to a Conclusion: Asteroid Killed the Dinosaurs

4 Mar , 2010 by

Over the years, scientists have debated the cause of the mass extinction that wiped out the dinosaurs 65 million years ago. Now, a panel of 41 international experts says it’s official: a massive asteroid around 15 kilometers wide slamming into Earth at Chicxulub, Mexico is the culprit. After surveying a wide variety of evidence for the competing theories, the panel said the telling evidence was the structures preserved in the interior of the crater. Computer models predicted how much rock was vaporized or ejected by the impact. “Our work lets us visualize the astonishing events of the few minutes after impact,” said Dr. Penny Barton, who led the group. “The front of the asteroid hit the Earth while the far side was still out in the upper atmosphere, punching a hole though the Earth’s atmosphere.”

The Cretaceous-Paleogene extinction was one of the biggest in earth’s history and geologic evidence of the impact has been discovered in rock layers from this time period, around the world. While the impact is widely accepted as the cause for the mass extinction, some critics disagreed, saying, for example, that the microfossils from the Gulf of Mexico show that the impact occurred well before the extinction and could not have been its primary cause.

The massive volcanism that produced the Deccan traps of India around this time has also been proposed as the main cause of the extinction. But in the panel’s review, the computer models synthesized the geologic evidence that support the impact hypothesis. The models showed that such an impact would have instantly caused devastating shock waves, a large heat pulse and tsunamis around the globe.

Moreover, a release of larger amounts of dust, debris and gases would have led to a prolonged cooling of Earth’s surface, low light levels and ocean acidification that would have decimated photosynthesizing plants and the species that relied on them.

The asteroid is believed to have hit Earth with a force one billion times more powerful than the atomic bomb at Hiroshima. It would have blasted material at high velocity into the atmosphere, triggering a chain of events that caused a global winter, wiping out much of life on Earth in a matter of days.

“As the asteroid vaporized explosively,” said Barton, from the University of Cambridge in the UK, “it created a crater 30 km deep and 100 km across, with sides as high as the Himalayas. However within only two minutes the sides collapsed inwards and the deepest parts of the crater rebounded upwards to leave a wide, shallow hollow.

“These terrifying events led to darkness and a global winter, resulting in the extinction of more than 70% of known species. The tiny shrew-like mammals which were around at that time proved better adapted to survival than the cumbersome dinosaurs, and the removal of these dominant animals paved the way for the radiation of the mammals and eventual emergence of humans on Earth.”

The team’s paper was published in the journal Science.

Sources: University of Cambridge


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Torbjorn Larsson OM
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Torbjorn Larsson OM
March 4, 2010 4:21 PM
“The tiny shrew-like mammals which were around at that time proved better adapted to survival than the cumbersome dinosaurs, and the removal of these dominant animals paved the way for the radiation of the mammals” Not only a teleological argument without any respect for the existence of likelihoods whatsoever, but wrong through and through: – “the cumbersome dinosaurs” not only survived, but did so better than mammals, since the number of species today (of birds) outnumber the mammals 2:1. [IIRC, ~ 6 000 species vs ~ 3 000.] – These “dominant animals” didn’t dominate the skies or the seas. But the parallel extinction of pterosaurs led to the dinosaurs subsequent dominance of the skies. (And the parallel extinction… Read more »
microverses
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microverses
March 4, 2010 3:28 PM

So 15km wide and….how what are the other dimensions? 60+km long to be hitting the surface and still in the upper atmosphere?

Something is amiss here or I’m blind to some info in this.

Help?

Manu
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Manu
March 4, 2010 3:36 PM

“paved the way for the … eventual emergence of humans on Earth”
So slightly teleological argument.

Andy F
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March 4, 2010 3:37 PM

For those interested in further reading on the Chicxulub impact, may I suggest ‘T. Rex and the Crater of Doom’ by Walter Alvarez, one of the scientists involved in the great scientific detective story surrounding the KT extinction.

It’s a sobering thought that up to 1975 it was thought that craters were mainly volcanic in origin (both on the Moon and Earth). Then came Alavarez’s work and Gene Shoemaker and his wife who realised that Meteor Crater in Arizona, for example was caused by an impact.

Everything changed in 1994 with Shoemaker Levy 9’s impact on Jupiter… and the rest is history (a bit like poor old T Rex!!!)

Jorge
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Jorge
March 4, 2010 3:50 PM

Here’s a curiosity: would this impact be strong enough to blast Earth material out of Earth’s gravitational well? Could there be Terran asteroids out there, originated in Chicxulub?

Torbjorn Larsson OM
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Torbjorn Larsson OM
March 4, 2010 4:29 PM

Um, sorry about the bad spelling. Also about confusing two concepts of dominance (number of species vs number of large species).

Craigboy
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Craigboy
March 4, 2010 5:05 PM

This isn’t news, the dinosaurs have known this for years.

Jlazor
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Jlazor
March 4, 2010 6:10 PM

Jorge just had an awesome insight! Are there Terran asteroids? Where are they? What information could we gain from them?

If there are any, they are probably beyond our reach in the dark reaches of space, but maybe Mars has some. Reverse panspermia anyone?

kettythomasan
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kettythomasan
March 5, 2010 2:22 AM

I’m guessing that the initial impact transmitted so much energy that the “solid” layers of earth that were impacted were either liquefied or suspended enough to act like a fluid for a short time, and that a wave of earth traveled and persisted for a measurable amount of time — thus an initial crater with a final crater of different size and shape.Pandora accessories

RUF
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RUF
March 4, 2010 11:07 PM

Computer models CANNOT be used to conclusively prove anything. It reflects bias of the programmmer, confirming his suspisions. Models also cannot account for anything which may be totally unknown to the person programming the model.

2stepbay
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2stepbay
March 5, 2010 12:36 AM

I find it fascinating many gigantic creatures occupied terra firma for over 250 million years, yet seemingly were abruptly handed their hat and shown the cosmic door. So much for seniority privileges. wink

250 million years is a daunting amount of time, yet a mere 2% of the Universe’s approximate age. Time for sleep…overwhelm just kicked in.

Astrofiend
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Astrofiend
March 5, 2010 3:07 AM

Torbjorn Larsson OM Says:
March 4th, 2010 at 4:21 pm

Well, at least one of your points is somewhat contentious. There has never been too firm a connection between modern birds and dinosaurs, and a few recent studies which I can’t be bothered tracking down seem to cast further serious doubt over it.

Seeing as I’m not providing any sources, feel free to take this as you will. I simply can’t be bothered trying to find them at the moment, though I did give them a cursory glance a while ago…

Torbjorn Larsson OM
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Torbjorn Larsson OM
March 5, 2010 7:24 AM
feel free to take this as you will. Well, as since Jorge says, the evidence is really, really solid on that one, I won’t take it at all. But FWIW, here are some references on the current crackpot contenders: Here and here. As Nash notes, these have never reached the technical literature, and there are reasons for that: If you’ve ever read anything about the history of bird origin theories, you’ll know that birds were originally linked with other dinosaurs back in the late 1800s, most famously by Thomas Huxley. This view remained fairly popular until the 1920s when Gerhard Heilmann’s book The Origin of Birds was published in English. Heilmann argued that birds could not have descended… Read more »
Jorge
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Jorge
March 5, 2010 4:27 AM

Sorry, Astrofiend, the evidence that birds are just winged dinosaurs is rock solid (pun intended). There are numerous anatomical hints to it, but the major evidence comes from the fossil record. Like relatively recent discoveries of raptor-like dinosaurs covered in feathers. Feathered animals much less bird-like than the Archaeropteryx (but still with plenty of bird-like characteristics other than the feathers) pretty much prove the connection.

Paul Eaton-Jones
Member
March 5, 2010 6:49 AM

It’s not so much the models that have led to this conclusion more that the tektites deposits further from the impact site are dated from the time of the impact. The deposits studied ‘in situ’ having being violently churned up have given a date 300,000 years too soon. The Deccan Traps were spread over 1.5 million years and no appreciable change occurred in the ecosystem in th efirst half million years.

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
March 5, 2010 7:04 AM

If there are any, they are probably beyond our reach in the dark reaches of space,

Why no, they are probably on the Moon, since they would orbit the Earth and there’s that giant fly swatter right in the middle of the road.

Other places to search would be the NEOs and perhaps our Lagrange points.

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
March 5, 2010 7:08 AM

Computer models CANNOT be used to conclusively prove anything.

Let us parse this:

– “Computer models CANNOT be used to” = I have never heard about theories and don’t know that/how they can be tested to desired remaining uncertainty.

– “conclusively” = I have never heard about theories and don’t know that/how they can be tested to desired remaining uncertainty.

– “conclusively” = I have never heard about theories and don’t know that/how they can be tested to desired remaining uncertainty.

Okay, thanks, we got it already at the “CANNOT” shout of crank fame.

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
March 5, 2010 7:33 AM

Oops, commenting that much, so of course need to put up a correction: the 2nd “conclusively” in my reply to RUF should of course be “prove”.

In some sense “proving” is a convenient shorthand for the procedure of testing.

But more aptly that would be “disproving” anyway, passing a test gives either a falsification or a quantifiable uncertainty but no “proof”. And the use of “prove” is nowadays a pretty dead giveaway that there is a quasi-inductivist in the house, pretending science is math and math isn’t empirical but “platonic” or some such nonsense.

I swear, next time I see someone claiming that science “prove” stuff, I’m going to scream.

Aodhhan
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Aodhhan
March 5, 2010 8:35 AM
The computer model used for this research is pretty much dead on. The model uses physics to come up with the answers to this scenario. The results are then checked against physical findings in order to figure accuracy. For instance, the model will say some of the ejecta would have been melted and would land as far away as point x. It would also provide the amount of certain ejecta at certain distances. Since we know the actual physical findings, if the model comes up with the same numbers then you know the data is reliable. They probably had at least 10 checks like this to test for accuracy. This doesn’t mean your sceptism about the findings aren’t… Read more »
Spoodle58
Member
March 5, 2010 9:21 AM

Rubbish. How can the 41 international experts explain the evidence in the fossil record that dinosaur species where becoming extinct millions of years before the asteroid impact .

The fossil record shows us that dinosaur species types had dropped from 30 plus to about 7 species types from 60 million years ago to 65 million years ago.

The asteroid impact occurred when dinosaurs where already basically extinct.

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