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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."

50 comments

  1. quite dense by Anonymous Coward · · Score: 0

    60 feet across, and 12,000 tons? Sounds pretty dense.

    1. Re:quite dense by i+kan+reed · · Score: 2

      Well, it's less than half the density of water.

    2. Re:quite dense by Ken_g6 · · Score: 2

      Wikipedia tells me that iron has a density of 7.874 g/cm^3. A 60-foot-diameter asteroid has a volume of 4/3*pi*30^3 cubic feet, or about 113100 ft^3. So, units tells me that an iron sphere that size would be about 27,800 tons. So it's not as dense as a solid iron asteroid would be.

      --
      (T>t && O(n)--) == sqrt(666)
    3. Re:quite dense by hermitdev · · Score: 2

      Not really. If you do the math, it works out to about 113,000 cubic feet (assuming a perfect sphere), meaning a roughly 203 lb/cubic foot of material, which is roughly half the density of cast iron.

    4. Re:quite dense by Vulch · · Score: 1

      If you did the sums you'd land up with about 1.75 tonnes per cubic metre, or not quite twice as dense as water. Even less if they're colonial short measure tons.

    5. Re:quite dense by i+kan+reed · · Score: 2

      You know what, that's 4 times too big, used diameter for radius. I accept any shame heaped upon me.

    6. Re:quite dense by CastrTroy · · Score: 1

      If it's less dense than water, then it would float. I highly doubt that any asteroid would actually float. Either your math is wrong (looks ok to me at first glance) or the numbers are off in the article.

      --

      Anthropic principle: We see the universe the way it is because if it were different we would not be here to see it.
    7. Re:quite dense by Anonymous Coward · · Score: 1

      I am this AC, and I stand corrected. Good thing I'm not in the asteroid-density-measuring department, or I would not do too well.

    8. 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!
    9. Re:quite dense by i+kan+reed · · Score: 2

      You know, I just default in my head to nice little 2d pictures.

    10. Re:quite dense by CastrTroy · · Score: 1

      Figured out your mistake, you're using the diameter, not the radius, actual density is about 3.4 times the density of water.

      --

      Anthropic principle: We see the universe the way it is because if it were different we would not be here to see it.
    11. Re:quite dense by Charliemopps · · Score: 2

      You know, the entire planet of Saturn would float if there were an ocean big enough to put it in ;-)
      But yea, he's wrong anyway.

    12. Re:quite dense by i+kan+reed · · Score: 1

      Yeah, I realized that too. Can I have partial credit for showing my work?

    13. Re:quite dense by Deadstick · · Score: 1

      At least somebody got it right...

    14. Re:quite dense by RenderSeven · · Score: 1

      Stop. You had me at "Saturn would float".

    15. Re:quite dense by PPH · · Score: 1

      Bedevere: "Wait. Wait ... tell me, what also floats on water?"

      Villagers: "Bread? No, no, no. Apples .... gravy ... very small rocks ..."

      Arthur: "A duck."

      Bevedere: "Exactly. So... logically ..."

      Villager: "If it ... weighs the same as a duck ... it's made of wood."

      Bevedere: "And therefore?"

      Villagers: "A witch! ..."

      --
      Have gnu, will travel.
    16. 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.

    17. Re:quite dense by Anonymous Coward · · Score: 0

      Unless it weighs as much as a duck

    18. Re: quite dense by Anonymous Coward · · Score: 0

      No. But you can make a root beer float.

    19. Re:quite dense by Anonymous Coward · · Score: 0

      You know, I just default in my head to nice little titty pictures.

  2. 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: 0

      journalistic competency

      My mind is blown, I'll have to try to read slate more often.

    2. 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.

    3. Re:Friction versus increasing pressure by snowraver1 · · Score: 1

      I'm intrigued... so does friction play no part at all then? It must have some impact.

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      Copyright 2010. All rights reserved. This comment may not be copied in any way including, but not limited to caching.
    4. Re:Friction versus increasing pressure by Charliemopps · · 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.

    5. Re:Friction versus increasing pressure by es330td · · Score: 1

      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.

    6. Re:Friction versus increasing pressure by WalksOnDirt · · Score: 2

      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.

      --
      a,e,i,o,u and sometimes w and y (at be if of up cwm by)
    7. 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.

    8. Re:Friction versus increasing pressure by Anonymous Coward · · Score: 0

      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.

      The reason it requires energy to "push through" the air is because of friction. You're not splitting molecules or atoms apart.

    9. Re:Friction versus increasing pressure by Flere+Imsaho · · Score: 1

      It's negligible. That's a fact, not friction.

      --
      It gripped her hand gently. 'Regret is for humans,' it said.
    10. Re:Friction versus increasing pressure by steelfood · · Score: 1

      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.

      --
      "If a nation expects to be ignorant and free in a state of civilization, it expects what never was and never will be."
    11. Re:Friction versus increasing pressure by dbIII · · Score: 1

      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).

    12. Re:Friction versus increasing pressure by Anonymous Coward · · Score: 0

      And the resulting exhaust pattern is freaky too. Mach diamonds are the visible result of pressure waves in the exhaust formed by and bouncing off the density change at the flame boundary and only form in a supersonic flow.

    13. Re:Friction versus increasing pressure by Anonymous Coward · · Score: 0

      This theory still doesn't explain the explosion of asteroids coming in. It doesn't explain the explosion of Sun Grazing Comets. It doesn't explain much at all. The total value of the compressed air in front of the Asteroid is essentially nothing in the energy of the explosion. The shock wave, the explosion everyting are explained quite well in electrical charge differentials between Earth and the rock coming in. The heat of its entry is relatively trival and is accounted for in the melt of the surface. It doesn't produce an explosion!

    14. Re:Friction versus increasing pressure by Anonymous Coward · · Score: 0

      It's not friction, it's compressibility. Friction exists, but the increase in temperature in front of a moving body is the result of compressing the air to its stagnation pressure (air is stagnant in the boundary layer).

  3. Since the Earth's surface by Nutria · · Score: 1

    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...

    --
    "I don't know, therefore Aliens" Wafflebox1
    1. Re:Since the Earth's surface by Anonymous Coward · · Score: 0

      Yes, but a detection can be made with infrasound detectors, and those seems to have a large scale of detection
      http://www.space.com/19860-russia-meteor-explosion-largest-detected.html
      I wonder if the data from these detectors are able to back-up the claim that there is more Chelyabinsk-sized impact.

    2. Re:Since the Earth's surface by hubie · · Score: 2
      The 20-year frequency estimate uses and extends the infrasound-based estimates. From the Brown et. al. paper:

      Using our best estimate for the Chelyabinsk airburst energy, of about 500 kt, we have estimated the bolide flux at the Earth over the period from 1994 to mid-2013. This estimate is based on 20 years of total global coverage by the US government or infrasound sensors, more than doubling the earlier time coverage.

    3. Re:Since the Earth's surface by nevermindme · · Score: 1

      I think we have great global coverage from the USGS in the form of seismic networks and the DOD in the form of SONAR and Early Warning from 1970 onwards making it 40 years of coverage that should pretty much cover all but the poles with at least two types 2 instruments. Still wondering why the timeframe is from only 1994... but I can guess the post test moratorium data is near 100% public.

    4. Re:Since the Earth's surface by MichaelSmith · · Score: 1

      And Antarctica, Greenland...

      --
      http://michaelsmith.id.au
    5. Re:Since the Earth's surface by Big+Hairy+Ian · · Score: 1

      Don't forget Sheffield :D

      --

      Build a Man a Fire, and He'll Be Warm for a Day. Set a Man on Fire, and He'll Be Warm for the Rest of His Life.

    6. Re:Since the Earth's surface by Big+Hairy+Ian · · Score: 1

      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.

      --

      Build a Man a Fire, and He'll Be Warm for a Day. Set a Man on Fire, and He'll Be Warm for the Rest of His Life.

  4. I just spotted a meteor literally just there. by Anonymous Coward · · Score: 1

    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 Russia, yeah, you bet your ass I freaked out a bit.

    Also, may as well post this while I am passing by.
    Best of the best clips from the Russian Meteor and Impact it had.
    Crazy stuff indeed.
    I sure hope nothing out there screwed up the generally stable meteor and asteroid belts, the last thing we need right now is the solar system screwing with our jump to the actual space age where we have an actual presence and not stupid silly satellites. That's baby steps, that isn't space stage, what's wrong with you?
    Would you class the bronze age as when some dude accidentally kicked a lump of rock with metals in it? Course you wouldn't.
    But really, it is fairly worrying.
    I guess at least the good thing is they are actively looking in to it now. Hell, they even made a committee. Damned rocks gonna get UN sanctions on them if they keep that up.

  5. 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

  6. Beta update! by Anonymous Coward · · Score: 0

    The reply function finally works in beta iterface as anonymus and layout also got better, fuck yeah! :D

  7. Has MSNBC blames global warming yet? by gelfling · · Score: 1

    Or have the just blame the Republicans?

  8. I have an idea by slashmydots · · Score: 1

    Let's pre-emptively invade space!

  9. Obligatory by Anonymous Coward · · Score: 0

    You know what, that's 4 times too big

    That's what she said!