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Chelyabinsk-Sized Asteroid Impacts May Be More Common Than We Thought 50

The Bad Astronomer writes "Using data from the Feb. 15, 2013 asteroid impact over Russia, scientists have determined that we may be hit by objects in this size range (10 — 50 meters across) more often than we previously thought, something like once every 20 years (abstract). They also found the Chelyabinsk asteroid was likely a single rock about 19 meters (60 feet) across, had a mass of 12,000 tons, and was criss-crossed with internal fractures which aided in its breakup as it rammed through the Earth's atmosphere."
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Chelyabinsk-Sized Asteroid Impacts May Be More Common Than We Thought

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  • by mc6809e ( 214243 ) on Wednesday November 06, 2013 @05:23PM (#45349309)

    It's nice to see that the author didn't buy into the myth that it's friction which causes the increase in temperature as a fast moving body move through the atmosphere.

    "As this main mass plummeted through our atmosphere at a speed of 20 kilometers per second â" dozens of times faster than a rifle bullet â" the huge pressure it generated compressed the air in front of it, heating it up."

    That kind of journalistic competency it worth noting.

    • Re: (Score:3, Informative)

      by Anonymous Coward

      Phil Plait is a well-known astronomer. I'd say he's probably an astronomer first, a writer second. So one shouldn't be too surprised by his accuracy.

    • I'm intrigued... so does friction play no part at all then? It must have some impact.
      • Re: (Score:2, Insightful)

        Well the reason there is a pressure wave in front of the asteroid at all is due to friction. If it were frictionless it would simply pass through the atmosphere without disturbing it. This is more semantics with the english language than making any scientific point.

        • by Anonymous Coward on Wednesday November 06, 2013 @08:51PM (#45351757)

          No and no. Even if it were frictionless, the air molecules would still have to get out of the way. The object is moving at Mach 25 or more, 25 times faster than the air molecules can get out of the way (ie, the speed of sound) easily. Therefore the air compresses. Hypersonic fluid dynamics is completely unlike subsonic fluid dynamics.

          Friction doesn't (well, hardly) enter into it.

          Neither does semantics. You're wrong, and so are the dummies who up-moderated you.

          • by dbIII ( 701233 )

            Hypersonic fluid dynamics is completely unlike subsonic fluid dynamics

            The thing that really brought that home to me is hypersonic nozzles. Subsonic nozzles go in (like a hose nozzle), hypersonic nozzles go out (like one of the Saturn V main engines).

        • It's not merely semantic. There's far more depth of information in the article's description, and hence far more accuracy.

          It's the difference between saying that someone was killed by a gallon of water versus saying that the person drowned. The former is factually correct, but not nearly as accurate.

      • by es330td ( 964170 )
        Friction does have a part, but not as much. Think about a car traveling at very high speed. While drag on the car of the air going past is non-zero, it is much less a factor than the energy required to push through the air ahead of the car.
      • It's negligible. That's a fact, not friction.

    • It's nice to see that the author didn't buy into the myth that it's friction ...

      You've just described one way that friction works, not that it doesn't apply.

  • is 71% water, such impacts should be around 2.45x as frequent as observed. Then add in the ones that impact in the Sahara and Australian Outback...

    • And Antarctica, Greenland...

      • Don't forget Sheffield :D
      • Actually Antarctica will get relatively few as it presents an oblique angle to most of the asteroids the hit earth. Bear in mind that 95% of asteroid strikes are at dawn local time as it's just as much the earth slamming into the asteroid as the asteroid hitting earth.
  • I had just posted above me spotting a meteor above my town there, lasted around 3.3 seconds. Longest I have seen, most I have seen were 1.3s at best.
    And it was a bright one too, none of these crappy weak streaks that vanish in to nothing, it was brighter than a typical helicopters search light in the distance, brighter than 3 planes worth of lights.

    They have been increasing in frequency I've noticed over the years. And that sudden 3.3s meteor at that brightness, especially after that crap that happened in

  • by hubie ( 108345 ) on Wednesday November 06, 2013 @06:44PM (#45350323)

    The Slate article mentions there were two Nature papers, but the article summary above only gives a link to one. The papers are:

    This one came up with 20 year frequency for these sized events: A 500-kiloton airburst over Chelyabinsk and an enhanced hazard from small impactors []

    This one looked a bunch of YouTube videos and analyzed how it broke up as it went through the atmosphere:The trajectory, structure and origin of the Chelyabinsk asteroidal impactor []

  • Or have the just blame the Republicans?

  • Let's pre-emptively invade space!

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