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

Posted by Soulskill on from the can-i-interest-you-in-some-meteorite-insurance dept.

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."

6 of 50 comments (clear)

  1. Friction versus increasing pressure by mc6809e · · Score: 5, Insightful

    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.

    1. Re:Friction versus increasing pressure by Anonymous Coward · · Score: 3, Informative

      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.

    2. Re:Friction versus increasing pressure by Anonymous Coward · · Score: 5, Informative

      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.

  2. Re:quite dense by Samantha+Wright · · Score: 5, Informative

    Eight times. The shame shall be heaped upon you because it is eight times too big, not four. Flatlander chauvinist pig!

    --
    Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
  3. Missed a paper reference by hubie · · Score: 5, Informative

    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

  4. Re:quite dense by Anonymous Coward · · Score: 3, Interesting

    I have a small piece of Chelyabinsk in my meteorite collection, It's a stony, not an iron, although it does have enough iron-nickel chondrules in it to be attracted by a magnet.

    Yeah, density of about 3.4 gm/cm^3 is about right. (My piece, at just over 10gms, is about 3 cc.)

    A 60-foot diameter iron is about what carved out the mile-wide Barringer (aka Meteor) Crater in Arizona. Irons tend not to airburst, or if they do, do it lower down in the atmosphere. It may also have been travelling faster.