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Science

Meteor Seen as Causing Extinctions on Earth 67

Posted by michael from the proximity-defense-system-needed dept.
An anonymous reader writes "From the NY Times (I think you may have to register): About three dozen minuscule shards of rock unearthed in Antarctica may be the fragments of a meteor that killed most life on Earth 250 million years ago, scientists are reporting today. These rocks have yielded soccer-ball-shaped molecules known as buckyballs containing extraterrestrial gases, as well as grains of quartz with fractures that indicate a tremendous shock. The extinction 250 million years ago, in a period known as the Permian-Triassic boundary, was the largest of all. About 90 percent of species disappeared."
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Meteor Seen as Causing Extinctions on Earth More

Meteor Seen as Causing Extinctions on Earth

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  • Pre-emptive correction (Score:3, Informative)

    by the morgawr ( 670303 ) on Friday November 21, 2003 @03:56PM (#7531755) Homepage Journal
    No this was not the extinction that killed the dinosaurs. This occured earlier in time.
    • Right. Dinosaurs disappeared 65 million years ago, this was 250. But going by the time period referenced, Permian-Triassic, isn't the Triassic about when the Dinosaurs first stared to appear?
      • Yes, but I don't know how far into the Triassic that would be. Maybe google can help us: Try the first link [google.com]

        From the lecture: "By Late Triassic (and maybe during the Middle Triassic), true dinosaurs finally appear"

        • yeah, I don't remember the Permian era and the article talks about the boundary between the two, so likely it's very early Triassic.
          • Paraphrased from palaeos [palaeos.com] (a little further down on that google query):

            Time scale works like this (from larger to smaller): Eon -> Era -> Period -> Epoch -> Age

            The Permian was the last period of the Paleozoic Era(which ending with the mass extinction). This was followed by the Mesozoic Era (whose first period was the Triassic). While Dinosaurs first appeared in the Triassic they become dominant during the Jurassic. Dinosaurs first appeared in the Carnian age (227 to 221 million years ago, dur

      • Yes, basically this event was what gave room for dinosaurs (and other new families) to develop. Much like whatever event caused dinosaurs to disappear gave room for development of more advanced mammals, eventually humans.

        I wonder what will take the dominant role after we humans are finished with Earth (we're in a perioid of very rapid extinction of species, thanks to human activity, and I don't really see the direction changing any time soon...)

      • Re:Pre-emptive correction (Score:4, Informative)

        by kalidasa ( 577403 ) * on Friday November 21, 2003 @05:52PM (#7532893) Journal

        The dino extinction is called the K-T extinction, for Cretaceous/Tertiary (it makes sense in German, I imagine), and the one in question would be the P-T extinction, for Permian/Triassic. So this is the previous huge mass extinction event to the K-T extinction. The Dinosauria branch off from the Reptilia in early Triassic, and all Dinosauria except the Aves die off at the K-T event.

        The P-T was bigger than the K-T.

  • Naturally-occurring Buckyballs? (Score:3, Interesting)

    by GTRacer ( 234395 ) <gtracer308@@@yahoo...com> on Friday November 21, 2003 @03:56PM (#7531760) Homepage Journal
    I mean, I remember reading about fullerenes in Discover like 10 years ago, but I never knew they could occur naturally, or in the case of a cataclysmic impact, spontaneously.

    I thought it took precise conditions to get them to form. And for these to have captured gases inside...

    Weird...

    GTRacer
    - Go-o-o-o-al!

  • Another article (Score:3, Informative)

    by DjReagan ( 143826 ) on Friday November 21, 2003 @04:00PM (#7531799)
    The BBC had an article [bbc.co.uk] on this also.

  • Impact-caused volcanic activity (Score:3, Interesting)

    by Vaevictis666 ( 680137 ) on Friday November 21, 2003 @04:05PM (#7531846)
    If the evidence for an impact does become more compelling, that would raise another geological mystery, whether meteor impacts can set off huge volcanic eruptions. Huge eruptions in India coincided with the Yucatan meteor impact 65 million years ago, and Dr. Basu sees a clear link between the Antarctic shards and the Siberian eruptions.

    Something to note is that both cases here involves a meteor impact on the opposite side of the earth from the eruptions. Coincidence?

    • Not coincidence at all.

      If there's an impact on one side of a sphere (or oblate spheroid, the Earth) shockwaves are going to travel along the surface boundary. As the waves radiate away from the impact site, they end up converging on the opposite side of the sphere (the antipode).

      If the eruptions are directly linked to the impact and the tectonic stresses from it, the stress is greatest at the impact site and second greatest at the antipode of the impact site.

      The new Scientific American has a great artic
    • Something to note is that both cases here involves a meteor impact on the opposite side of the earth from the eruptions. Coincidence?

      Coincidence? Nope. When a spherical body like the earth or any other of the terrestrial planets is hit by a suficiently large meteor the shockwave is focused by the spherical shape and arrive at the exact opposite side of the planet resulting in a massive earthquake (actually 3, one from each of the three types of vibrations (sound) that travel through the earth with differ

      • Your hypothesis has a few problems..

        a) The Earth is not perfectly spherical, and it is distinctly non-Isotropic.

        b) You need to include some calculations on how much energy would actually be available from the known crater. Even under generous assumptions, we are looking at a magnitude 10.5 earthquake at best.

        c) Surface waves are strongly attenuated in the crust, which is strongly anisotropic. The energy arriving at the other side of the planet would be negligable. P and S waves would not be focusse

        • The energy from the impact is not the problem. I was not assuming that the energy from the meteor strike formed the volcanic eruptions in India, but only that the seismic vibrations influenced the upper mantle causing more extensive melting than is usually the case (the asthenosphere is partially molten, or at least very close to the solidus as P and S wave velocities are lower in this part of the mantle). It is therefore possible that a large vibration could influence this part of the mantle.

          I agree that
  • ... that these really really large extinctions happen all the time throughout history and we're essentially in a cycle. Ie... nothing.. then something.. then more somethings.. then dinosaurs then us... then we all die somehow (meteor ... nuclear war... etc) and it starts all over again.

    Technically I see no reason why this can't be true, since the time span is so long between mass extinctions (not like the dinosaurs one but more like the one described in this article where almost all life is destroyed),
    • any evidence of a previous civilization or life forms would eventually degrade into basic elements.
      The problem is that they don't fully degrade. That's what the Pabodie expedition to the Antarctic discovered in 1931.

  • I know slashdot is slow on getting news but...

    250 million years? ;)
  • what you can smuggle through customs.
  • This animation [harvard.edu] shows the known minor planets in the Inner Solar System presently.

    This page [nasa.gov] updates regularly on newly discovered objects.
    There are many more to be found. Though the risk of an impact like the one believed to have been involved is very slight.

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