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Meteor didn't do in the dinos

The giant meteor that crashed off the coast of Mexico around 65 million years ago hit the Earth too early to explain the dinosaurs' demise and was too tame to even hurt a protist, according to a new study published today (Apr. 27) in the__ linkurl:Journal of the Geological Society.;http://intl-jgs.geoscienceworld.org/ __Some researchers, however, maintain that the study's authors are needlessly wishing away the shooting star. Image: NSF/Zina DeretskyThe linkurl:Chicxulub crater;http://en.wikipe

By | April 27, 2009

The giant meteor that crashed off the coast of Mexico around 65 million years ago hit the Earth too early to explain the dinosaurs' demise and was too tame to even hurt a protist, according to a new study published today (Apr. 27) in the__ linkurl:Journal of the Geological Society.;http://intl-jgs.geoscienceworld.org/ __Some researchers, however, maintain that the study's authors are needlessly wishing away the shooting star.
Image: NSF/Zina Deretsky
The linkurl:Chicxulub crater;http://en.wikipedia.org/wiki/Chicxulub_crater in Mexico's Yucatan peninsula has been hailed as the smoking gun that proves the theory that an asteroid impact exterminated around two-thirds of all living species, including dinosaurs, at the end of the Mesozoic era. But "we can show now for the first time that it did not cause mass extinction," linkurl:Gerta Keller,;http://www.princeton.edu/geosciences/people/display_person.xml?netid=gkeller&display=All a Princeton University paleontologist and geologist, told __The Scientist__. "It didn't kill the dinosaurs. In fact, it didn't cause much damage that we can determine from the geological record." Keller and her colleagues studied sandstone sediment in Northeastern Mexico, around 600 km from the impact crater, where ejectile debris from Chicxulub has been found. First, they characterized the deposits and showed that the asteroid impact predated the mass extinction at the Cretaceous-Tertiary (K-T) boundary by around 300,000 years. This was not in itself a new finding -- Keller previously found similar evidence in linkurl:Texas;http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V61-4MRG0CC-3&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=18c1489eacec700821657d95a8759caa and in a linkurl:core drilling;http://www.pnas.org/content/101/11/3753.long from the crater itself. But when she inspected the sediments more closely for the fossil remains of tiny protists she found what she considers the "nail in the coffin" to the asteroid-impact theory. Keller measured the diversity of the abundance of marine zooplankton called linkurl:planktic foraminifera;http://www.ucl.ac.uk/GeolSci/micropal/foram.html and showed that all 52 species that she found below the ejected Chicxulub debris were still present in the fossil record after the asteroid impact. In contrast, only 13 out of 44 species remained in the geological record following the K-T mass extinction, demonstrating that the earlier asteroid impact did not polish off the protists, and, by extension, the dinosaurs, either. In a linkurl:paper;http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6R-4TJ1HV2-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=3d926a33c92fae5d876699e94df5f37b published in the January issue of __Palaeogeography, Palaeoclimatology, Palaeoecology,__ Keller also reported similar effects on species extinction at a shallower, interior seaway in Texas. "This is definitive proof that Chicxulub could not have caused the mass extinction," said Keller. "It's just not possible with all the evidence that has come in." These finding should come as no great surprise, she added. "None of the mass extinctions in the history of the Earth were caused by impacts... but a whole bunch of them are closely associated with massive volcanic eruptions." Instead of a single devastating impact event that wiped out most of life in a geological instant, Keller said that gigantic volcanic eruptions at the linkurl:Deccan Traps;http://en.wikipedia.org/wiki/Deccan_Traps in India, possibly in conjunction with other subsequent meteor impacts, probably wrought the environmental destruction and climate change that eventually pushed most species over the edge. Other researchers, however, remain unconvinced. "[Keller] is making a mountain out of a molehill," said linkurl:Luann Becker,;http://physics-astronomy.jhu.edu/people/res_staff/ a Johns Hopkins University geochemist. "To me, it's really quibbling. When you think about geological time, even a few hundred thousand years isn't a long time and you can argue that there are some pretty big error bars on that [date estimate]." Becker argues that both the Chicxulub impact and the Deccan volcanism together facilitated the demise of life on Earth. "[Keller] seems to want to decouple the two, but unquestionably these things are linked." linkurl:Ralph Von Frese,;http://www.geology.ohio-state.edu/~vonfrese/ a geophysicist at Ohio State University in Columbus, said that the Declan eruptions "could have been energized or initiated by the impact." What's more, the oceans might have buffered the effects of the environmental destruction triggered by the asteroid impact, he noted. Thus, the marine protists might not have gone extinct right after the asteroid impact, which could explain Keller's findings. "It's a very imperfect [geological] record," he said. "I don't know that [this study] settles the issue one way or another."
**__Related stories:__***linkurl:Mass extinction effect on mammals disputed;http://www.the-scientist.com/news/display/53035/
[28th March 2007]*linkurl:'Biotic revenge' and the death of dinosaurs;http://www.the-scientist.com/article/display/7266/
[26th January 1987]
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Comments

Avatar of: MADHU THANGAVELU

MADHU THANGAVELU

Posts: 8

April 27, 2009

Wait a minute.\n\nI thought a cataclysmic event would do in creatures at the top of the food chain much, much quicker than the hardy ones at the bottom.\n(See S.J.Gould's Full House, for instance.)\n\nT.Rex, Trice and other very large dinsaurs would have perished promptly while the protists might have survived through not just the K/T event but many, many others as well.
Avatar of: Rhodri Harfoot

Rhodri Harfoot

Posts: 4

April 27, 2009

I haven't been able to find that paper on the Journal for the Geological Society page or using google scholar. The closest I can find is the one published in Palaeogeography, Palaeoclimatology, Palaeoecology referred to later in the article.\n\nCould the editors please provide actual references for papers under discussion in these articles?\n\nIncidentally, what are the chances that the Chicxulub meteor was actually a part of a multiple impact spread around the planet? Similar to the Shoemaker-Levy 9 impact on Jupiter.
Avatar of: Elie Dolgin

Elie Dolgin

Posts: 4

April 27, 2009

It might not be online yet, but the reference should be:\nJ Geol Soc 166, 393-411, 2009.\ndoi: 10.1144/0016-76492008-116\n\nElie Dolgin, Associate Editor, The Scientist
Avatar of: Rhodri Harfoot

Rhodri Harfoot

Posts: 4

April 27, 2009

Thanks for the reference.
Avatar of: anonymous poster

anonymous poster

Posts: 3

April 28, 2009

Recently,while watching a dino show,I thought how funny it is that they always situate trees and vegitation around the dino. And they always draw the vegitation to scale. I thought that since dinos were definately heavy just simply walking along they would kill vegitation by trompping over it and uproot trees in their path. Imagine a dino trying to walk through a forest. they would just plow down trees with the width of their bodies. Then this other idea came to me. Possibly gravity was a bit different then. Maybe not terribly so but enough different to prevent distruction from the weight of the masssive number of dinos trompping over vegitation. Maybe trees could bend a lot without the pulling of gravity causing them to snap. Possibly as meteors hit the ground and other planets situated themselves around us the magnetic pull of the new planets changed the gravity making it more difficult for the dinos to move about, causing distruction on vegitation causing massive new vibration on the earth on the califorinan plain that may have lead to many earthquakes, then volcanos, then the total distruction etc..

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