Largest in a century.


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More on today’s Russian meteorite: Largest in a century.

My earlier skepticism appears incorrect. This impact actually happened.

Note the article’s sense of outrage and panic that we aren’t looking for these types of rocks:

Although a network of telescopes watches for asteroids that might strike Earth, it is geared towards spotting larger objects — between 100 metres and a kilometre in size. “Objects like that are nearly impossible to see until a day or two before impact,” says Timothy Spahr, Director of the Minor Planet Center in Cambridge, Massachusetts, which tracks asteroids and small bodies. So far as he knows, he says, his centre also failed to spot the approaching rock.

Yet, today’s impact actually illustrates the wisdom of excluding this kind of small asteroid from searches. They aren’t big enough to do serious harm, and trying to find them would hamper searches for larger asteroids that do pose a serious risk.

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7 comments

  • Sikhote-Alin meteorite of 1947, also in Russia, so far seems to be a bit bigger, but this one is definitely way up on the list!

    http://en.wikipedia.org/wiki/Sikhote-Alin_meteorite

  • Sandra Warren

    I don’t blame you for your earlier skepticism, especially considering the former USSR’s tendency to obscure the truth about the slightest thing, and the current regime’s attempted return to that era. I had no idea that a meteor could leave a contrail.

  • There’s a famous film of an event called The Great Daylight Fireball of 1972. A person in Grand Teton National Park filmed a meteor passing through the atmosphere (there was no impact) leaving a very visible contrail.

  • My current understanding is that there is a fairly small window of between 20 and 30 meters diameter which can end up killing people. The Russian meteor was about 17 meters in diameter and didn’t kill anyone AFAIK. But you increase the diameter and you increase the mass at a cubed rate. So I think that at about 20 meters, you begin to start having deaths not just injuries.

    But above 30 meters, the cross-sectional area is large enough that we are getting 2+ days of warning which should be enough to allow for evacuations. The length of warning keeps going up to where people could easily evacuate Tunguska-sized regions in enough time.

    Larger than that and you cross over a line where it is no longer a last-minute incoming warning but an issue of whether the NEO had been detected on a previous orbit. Note: It is probably not a coincidence that one that passed us was detected almost exactly a year ago – it is probably in a very Earth-like orbit. Asteroids of that size are much more likely to be discovered centuries or millenia before they will impact Earth.

    Finally, the very large-sized asteroids (Earth-destroying) may not exist because we have telescopes large enough that they would have been found by now.

    So it is the last-minute warning of the 20-30 meter sized ones that we need to focus on.

  • Okay, now I’m seeing estimates of 10,000 tons for the incoming meteor, which is QUITE larger than the numbers I was seeing Friday. On Saturday at the Tucson Gem & Mineral Show, I actually saw a vendor selling fragments of the Sikhote-Alin meteorite. It’s a pretty safe bet they’ll be selling bits of this Chebarkul meteorite there next year!

  • trying to find them would hamper searches for larger asteroids

    This statement jumped out at me. How? Since you are looking for spots moving relative to the background; how does including smaller reflections in any way hamper finding greater reflections (especially where less light does not always mean less size?)

  • To see smaller reflections, you need higher resolution, which means you must devote money and resources to build telescopes capable of doing this. Then you have to fund their operation and the computer equipment capable of searching through this data, which because of the higher resolution will probably be produced in much greater quantity and therefore require more sophisticated equipment to analyze.

    All of this will cost money, and right now there really isn’t any money to build the telescopes and fund the operations needed to find the larger objects. To me it seems more sensible to focus our limited resources on finding the asteroids that will do serious and truly catastrophic damage. These smaller asteroids, such as the one that hit Russia on Friday, don’t fall into that category.

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