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Space Science

First Evidence Found of a Comet Strike On Earth 68

Posted by samzenpus
from the big-boom dept.
mdsolar writes in with a story about evidence of a comet explosion over Egypt 28 million years ago. "Saharan glass and a brooch belonging to King Tut provide the first evidence of a comet directly impacting Earth, a new study claims. The finding may help unlock some of the mysteries surrounding the birth of our solar system. About 28 million years ago a comet exploded over Egypt, creating a 3600F (2000C) blast wave that spread out over the desert below. The fiery shockwave melted the sand, forming copious amounts of yellow silica glass scattered over 2,300 square miles (6,000 square kilometers) of the Sahara. Polished into the shape of a scarab beetle, a large piece of this glass found its way into a brooch owned by the famed Egyptian boy king Tutankhamen. 'Because there is no sign of an impact crater, it has been a mystery as to what kind of celestial event actually could have caused this debris field, but a small, black stone found lying in the middle of the glass area caught our attention,' said study co-author David Block, an astronomer at Wits University in Johannesburg, South Africa."
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First Evidence Found of a Comet Strike On Earth

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  • Not necessarily. (Score:4, Informative)

    by C0R1D4N (970153) on Monday October 14, 2013 @07:14AM (#45120265)
    Tunguska [wikipedia.org] is believed by some to be a comet not an asteroid, and since this is hardly confirmed, this is therefore the second "possible comet strike" recorded.
    • Either way we got lucky with Tunguska. I wonder if the next large airburst like that will hit a city.
      It would be absolutely horrible...
      But the fringe benefit of our space budget multiplying overnight?

      • by Cryacin (657549)
        The war against asteroids.
      • by C0R1D4N (970153) on Monday October 14, 2013 @08:10AM (#45120685)
        Maybe it will hit a joint session of congress.
      • by Kethinov (636034) on Monday October 14, 2013 @09:51AM (#45121591) Homepage Journal

        We didn't get lucky. The vast majority of the surface of the Earth is either not populated or extremely sparsely populated. The odds are strongly against such a large airburst happening to burst over any reasonably densely populated area.

      • I wonder if the next large airburst like that will hit a city.

        You don't have to wonder, I think that maps and probability theory ought to serve you well. As in, we're not in the Trantor stage yet.

        • I was under the impression that 7-11% of the Earth's landscape was inhabited. Even avoiding a 5% chance of an awful disaster counts as "lucky" to me.

          • Isn't there a difference between "inhabited" and "being a part of a city"? If half of the world lived in places with, say 500+ people per square km (quite generous for a definition of what is "urbanized area"), it would make something like 1,5% of total Earth's surface area. The definitions probably make this more than a little bit fuzzy, but if a large body hits Earth, the chances of hitting an urban area directly are tiny. The environmental effects would me much more severe - for everyone, not just for th
            • A city is just an organizational unit. As far as I know pretty much any place inhabited with people has a name for their area. I didn't however think to make the distinction between villages and cities.

              I should have put inhabited. I just meant that it was incredible that Tunguska only killed one person considering the energy and radius of the blast. Also a 1.5% chance to take out a very large number of people seems pretty high to me. Scientists that do incredibly high-level statistical calculations have the

      • Do you mean an airburst over a city like this [wikipedia.org]?

    • by AC-x (735297)

      If you RTFA you'll find it's a bit more than "hardly confirmed":

      A tiny slice of the black pebble was put through isotopic analysis, which definitely ruled out that it came from a meteor. Instead, the analysis showed that the pebble possessed the unique chemical signature of a comet, measured in terms of elements such as argon and carbon.

  • David Block should see Stargate SG-1. Everything is explained there. Too bad they left Abydos so soon.
  • Update? (Score:5, Informative)

    by Dunbal (464142) * on Monday October 14, 2013 @07:35AM (#45120403)

    'Because there is no sign of an impact crater, it has been a mystery as to what kind of celestial event actually could have caused this debris field'

    Are these people dim-witted? We had firsthand video footage of what happens when a big chunk of rock burns into the atmosphere. You get a huge multi-megaton blast like in Chelyabinsk as the meteorite breaks apart due to wanting to move faster through the atmosphere than the air can actually move out of the way... This blast IS NOT NECESSARILY THE IMPACT SITE [wikimedia.org]. It would be a rare thing for a meteorite to be headed perpendicular to the earth's surface. Extrapolating this mechanism to even larger chunks of rock, you'd expect fused sand and little lumps of meteorite, but you wouldn't expect to see the main part of the meteorite where the sand is. That thing landed far away from the blast site. Same for Tunguska - they never found anything because the "crater" is the epicenter of the shock wave, not the actual impact with the ground. All these theories of mysterious "evaporating comets" should be re-evaluated in the face of this new, modern evidence.

    • Re:Update? (Score:5, Insightful)

      by Thanshin (1188877) on Monday October 14, 2013 @07:52AM (#45120521)

      Are these people dim-witted?

      One lesson I learned from the game of Go: "If a conclusion depends on the experts being dumb or incompetent, your conclusion is most probably a step the experts already took into account and dismissed as part of their reasoning."

      This applies to a lot of fields of science.

      • Re:Update? (Score:4, Insightful)

        by SJHillman (1966756) on Monday October 14, 2013 @08:10AM (#45120675)

        Unfortunately, it only rarely seems to apply to politics.

        • Re:Update? (Score:5, Insightful)

          by Thanshin (1188877) on Monday October 14, 2013 @08:24AM (#45120843)

          For politics there's the alternative:
          "If a conclusion depends on the politician being dumb or incompetent, your conclusion is most probably a step the politician already took into account and dismissed in favor of another one that includes more cash in his pocket."

          • by steelfood (895457)

            That's exactly it. The question is not, do they even know what they are doing. The question is, what are their motivations. And public service is not a motivation for anybody in the field.

            Once you realize that politics is a way for charismatic but otherwise useless individuals to earn a living, then the reasoning behind their actions are clearer. They're functionally no different than used car salesmen, conmen, investment bankers, or MBA's, and serve little other purpose than to leech off society (or in the

          • Bob's Political Razor: "Of two similarly plausible explanations for a politician's action, the most cynical is usually true."

            --
            I call dead presidents by their first names, before they get into my pants

      • At first the prior post "Are these people dim-witted? " seemed to make sense.

        Then I thought for 30 more seconds and realized; if there is an "explosion" of a comet, doesn't that means the energy of that event "blows up" the comet? It's not like skipping a stone across a pond, because the water isn't exploding when the rock makes its little hops. So yes, you should see debris from the comet in a trajectory from the point of the explosive impact of the air (or whatever) if there is enough energy to cause a 36

    • If you actually bothered to read the article and absorb the information presented, you will see why they ruled out a meteor air-burst. The small stone they recovered from the tektite region did not match stony or iron meteorite material, but cometary material. Therefore they concluded the object that detonated in the air above the tektite region was a comet, not a meteor.

    • It would be a rare thing for a meteorite to be headed perpendicular to the earth's surface
      .

      I realize this is slightly off-topic to this thread, but I witnessed something a few years back that was probably this. Two of us were on our backs watching the night sky when we both saw something glow, expand into a "light circle" maybe half as wide as a full moon, then go away -- all in about one second.

      It had the "timing" of a 'shooting star', but it did not have the arc.

      I tried searching on Google to see

      • One other thing I realized some time later is that, had this been a 'shooting star', we could have been watching something that then hit us. Sobering. I realize the probabilities are ridiculously low, but still they are (were) there.
        .

        This was no hallucination either. Perfectly clear night. Plenty of other stars, and 'shooting stars' visible. Both of us saw it. No alcohol or equivalent involved.

      • by Sockatume (732728)

        Probably a satellite flare.

      • by xupere (1680472)

        I'm not saying it was aliens ...

      • Swamp gas refracting the light from Venus? Definitely not a supernova though. Those last much longer than a second. One that flashed that brilliantly would have lasted a long while and would have been widely reported. For comparison, SN 1054, which formed the Crab Nebula, was visible to the eye for two years (according to Chinese records).

    • by Sockatume (732728)

      Maybe they're not idiots, but being scientists rather than Slashdot commenters they were unwilling to jump to specific conclusions on the basis of "look at teh youtubes, morans" and block caps?

  • by Overzeetop (214511) on Monday October 14, 2013 @07:41AM (#45120441) Journal

    Really? The whole middle east and north Africa turned into a sheet of glass instantaneously?
    Tell me more about this "comet strike" you are proposing...

    • by Anonymous Coward

      Really? The whole middle east and north Africa turned into a sheet of glass instantaneously?
      Tell me more about this "comet strike" you are proposing...

      That means that oil is not the most abundant material in the middle east. Under the sand is a lifetime supply of glass for the whole planet!

  • by gravis777 (123605) on Monday October 14, 2013 @07:53AM (#45120529)

    In the headline, it impacted, first sentence it exploded, Second it impacted, fourth it exploded.... So did it impact or explode in the atmosphere? Or did the explosion result in chunks impacting?

    • Or did the explosion result in chunks impacting?

      To call sand-grain-sized remnants 'chunks' may be a scaling error, but yeah - BANG! -> rain of particulates, likely near-microscopic, over rather a large area.

    • by dsvick (987919)

      Maybe they mean "impact" as in had an effect on. I'm pretty it is just bad writing though ... just trying to give them an out ...

    • The quick answer -- again with 30 seconds of thought on the matter; is both.

      It impacted the air and exploded above the ground.

      Could have been fine burning through the stratosphere, but then it hit that heavy cloud, smog or a duck -- whatever it was, it was the last straw for that asteroid...

  • by Anonymous Coward

    Far as I was aware even a few thousand years ago the Sahara was meant to be have been somewhat green with the change caused by the Himalayas rising. Maybe wrong but I'm sure 28 million years ago it wasn't a desert so why is there fused sand?

    • by stjobe (78285) on Monday October 14, 2013 @08:45AM (#45121047) Homepage

      Wikipedia [wikipedia.org] is only a few key-presses away, you know:

      The climate of the Sahara has undergone enormous variations between wet and dry over the last few hundred thousand years.[15] This is due to a 41000 year cycle in which the tilt of the earth changes between 22 and 24.5.[16] At present (2000 AD), we are in a dry period, but it is expected that the Sahara will become green again in 15000 years (17000 AD).
      During the last glacial period, the Sahara was even bigger than it is today, extending south beyond its current boundaries.[17] The end of the glacial period brought more rain to the Sahara, from about 8000 BC to 6000 BC, perhaps because of low pressure areas over the collapsing ice sheets to the north.[18]

      (emphasis mine)

      • I had the same thought...but the problem is, you're off by many orders of magnitude. From TFS, the comet was 28 million years ago; Wikipedia was discussing climate on the order of tens of thousands of years. No dice.
        • by devent (1627873)

          I think there is a 41000 year cycle. 28 million years ego would be -682 cycles, because that's an even number, 28 million years ego was a dry cycle like today.

  • Is this the same stuff as the black stone in the Kaaba?

  • The blast turning sand into glass makes since. Our "USA" first atomic bomb blast created a sheet of glass under the blast. So comet/asteroid is a tossup could have been either or both.

God may be subtle, but he isn't plain mean. -- Albert Einstein

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