INCOMING!: метеорита в Челябинске, Russian Meteor - February 2013 |
INCOMING!: метеорита в Челябинске, Russian Meteor - February 2013 |
Feb 15 2013, 07:01 AM
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Senior Member Group: Moderator Posts: 3233 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
Looks like a small meteoroid decided to spoil 2012 DA14's big day by exploding over Russia...
http://zyalt.livejournal.com/722930.html?nojs=1 -------------------- &@^^!% Jim! I'm a geologist, not a physicist!
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Feb 16 2013, 09:30 AM
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#2
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Member Group: Members Posts: 282 Joined: 18-June 04 Member No.: 84 |
If it exploded/disintegrated that high above the ground, I would say people in the region had a VERY lucky escape. The Tunguska bolide is thought to have exploded 6-10km above ground. If this had done the same, I think we would have had a major disaster.
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Feb 16 2013, 01:33 PM
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#3
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Member Group: Members Posts: 723 Joined: 13-June 04 Member No.: 82 |
If it exploded/disintegrated that high above the ground, I would say people in the region had a VERY lucky escape. The Tunguska bolide is thought to have exploded 6-10km above ground. If this had done the same, I think we would have had a major disaster. From the science blog Dynamics of Cats: QUOTE Air has density of about 10^-3, at ground level decreasing approximately exponentially with scale height, and the scale height is of order 10 km. Therefore meteors tend to break up at 10-20 km altitude if they don’t make it to the ground. A 1 m rock needs to sweep a path of over 2 km through the air to stop effectively, a 12 m rock needs about 24 km of air to stop. So a rock that big coming straight down will likely hit the ground.
The Chelyabinsk meteor came in at a shallow angle, and so traversed a column of air long enough to brake it and break it. This is very fortunate, or we’d have had a ground detonation of a few hundred kilotons and likely mass casualties. Most of the injuries seem to have been from broken glass, consistent with reports of other large explosions. Glass breaks from overpressure of about 1/4 PSI – and as the bomb damage calculator (below) shows, that overpressure goes out to about 20 km radius (for ground detonations which this was not). Here we had an air detonation (worse) but with the energy spread out over a linear track, not deposited instantaneously at a point (both better and worse). Hence the damage was consistent along the track and for tens of km either side of it, but nowhere was there a point or line of extreme destruction. A little bit higher energy impact, steeper impact angle, faster speed or bigger rock, and there would have been a zone of severe damage surrounded by an elongated annulus of the moderate damage actually seen, and there would have been many deaths. |
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