INCOMING!: метеорита в Челябинске, Russian Meteor - February 2013 Options

[volcanopele]

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

[dvandorn]

I can certainly see how there was a pretty big explosion in the air, there is a rather extreme pulse of light and then the contrail sort of vanishes. But -- a 500 megaton explosion only 18 km up, over a populated town, and all we had from that was a bunch of broken glass? I mean, that's more powerful of an explosion than the Tsar Bomba, the largest thermonuclear explosion that has ever been accomplished, and that explosion caused the clouds to move at hundreds of miles an hour away from the blast at distances of 20 to 30 miles. I sure don't see that kind of immense airburst in the videos of the bolide....

-the other Doug


Edit:
oops -- just reviewed the figures, and either I misread the megatonnage the first time through or Mongo adjusted his figures. Still, a 5 MT bomb packs an awfully big punch...

[ugordan]

Still, a 5 MT bomb packs an awfully big punch...

Tunguska was in recent years re-estimated to have been around something like that. This clearly had to be less. How much less depends on the actual altitude of the "airburst". At 10 km, a Hiroshima-type burst seems plausible to me. To be in the megaton range, it would have had to be significantly higher up, otherwise I'd expect much more extensive damage below. But these are all just my W.A.G.s...

NASA is estimating this to be around a 15 meter object and they're calling this one the biggest one after Tunguska. Doesn't say what their estimates are based on.

[Mongo]

NASA is estimating this to be around a 15 meter object and they're calling this one the biggest one after Tunguska. Doesn't say what their estimates are based on.

The impact effects website gives the following results for a 15m object with density adjusted to produce a 1 kPa overpressure at a realistic distance given the videos. Total mass would be about 13,000 tonnes for an energy release of 830 KT.

Your Inputs:
Distance from Impact: 15.00 km ( = 9.32 miles )
Projectile diameter: 15.00 meters ( = 49.20 feet )
Projectile Density: 7200 kg/m3
Impact Velocity: 30.00 km per second ( = 18.60 miles per second )

Energy:
Energy before atmospheric entry: 5.73 x 10^15 Joules = 1.37 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 140.0 years

Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundreths of a degree).
The impact does not shift the Earth's orbit noticeably.

Atmospheric Entry:
The projectile begins to breakup at an altitude of 28500 meters = 93400 ft
The projectile bursts into a cloud of fragments at an altitude of 16200 meters = 53100 ft
The residual velocity of the projectile fragments after the burst is 18.8 km/s = 11.7 miles/s
The energy of the airburst is 3.47 x 10^15 Joules = 0.83 MegaTons
Large fragments strike the surface and may create a crater strewn field. A more careful treatment of atmospheric entry is required to accurately estimate the size-frequency distribution of meteoroid fragments and predict the number and size of craters formed.

Air Blast:
The air blast will arrive approximately 1.11 minutes after impact.
Peak Overpressure: 1050 Pa = 0.0105 bars = 0.149 psi
Max wind velocity: 2.47 m/s = 5.52 mph
Sound Intensity: 60 dB (Loud as heavy traffic)