Tunguska Explosion

For those of you who don't know, the Tunguska explosion is a large explosion that took place in an isolated area of Russia in 1908. From what I read and heard, the scientific community believes that the explosion was caused by a meteor or asteroid that exploded 5 to 10 kilometers above the area.

My question is: What is the physical or chemical process by which a meteor or asteroid would explode so close to the surface of the Earth? I can understand how the heat, stress, and pressure of entry can cause it to vaporize, or disintegrate, but I don't understand how it would explode. Can anybody provide an explanation?

 

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Tunguska meteorite Physics:

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result of: "blasts of four fragments and heat radiation influence by ballistic shock wave's surface"

 

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How about two intuitions, rather than an explanation:

Have you ever felt the buffeting of turbulence outside a car window at highway speed? The comet was being hit with self-generated shock waves, like being hit with big hammers, from several directions at once. If you slam a walnut between two invisible sledgehammers in midair, how would you describe what you see the walnut do?

Comets hold a lot of water. The pressure spike from entering the atmosphere at high speed - not just the friction on the outside, but the compression in the middle from decelleration and ambient air pressure - heats the water throughout the comet and vaporizes some of it. That is explosive.

Just two mental pictures, for intuition.

 

so it was a comet and not a meteor?

 

comet:

A celestial body, observed only in that part of its orbit that is relatively close to the sun, having a head consisting of a solid nucleus surrounded by a nebulous coma up to 2.4 million kilometers (1.5 million miles) in diameter and an elongated curved vapor tail arising from the coma when sufficiently close to the sun. Comets are thought to consist chiefly of ammonia, methane, carbon dioxide, and water.

meteor: The streak of light seen when a meteoroid enters into the Earth's atmosphere, where it burns up as a result of friction.

 

Tunguska accident...was no ordinary on all accords

it was a nuclear explosion within this body.

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As to speculate for what it really was ... I lean towards the side that it was a UFO, spaceship precisely. The reason I believe so is because of the way this thing exploded and its trajectory.

 

So it was a comet that turned into a meteor?

 

we wouldn't know if it was a comet and it became a meteor somewhat...only raging nuclear fire and shock waves hit the ground and pines below.

 

iceaura,

If this was the case, wouldn't the comet just break up instead of explode? Also, if this is the true then why do other large comets and asteroids hit the surface of the Earth without blowing up (like the one that caused the extinction of the dinosaurs)? For the majority of asteroids and comets, if they're small they burn up in the atmosphere, and if they're large they hit the surface. What's so special about the Tunguska asteroid/comet that caused it to blow up just above the surface?

I would imagine that the outside of the comet would be much hotter than the inside, causing the ice on the outside to boil probably even before the ice in the center begins to melt. In this case, there would be no pressure on the inside to cause an explosion.

As for compression due to acceleration, wouldn't the compression be greatest when the comet/asteroid first hits the outer atmosphere, and not when it almost reaches the surface? Also, wouldn't the compression cause the ice of the comet to crack, thereby resulting in the disintegration of the comet?

The only way I can see for a comet/asteroid to explode so violently so close to the Earth's surface would be if the comet/asteroid was constructed like a cooking pot where the outside is a very strong metal with a high melting point and the inside was water or a gas. This structure would allow pressure to grow on the inside, while the shell holds the pressure in until the pressure reaches a certain point. Unfortunately, comets and asteroids aren't constructed this way.

 

Orleander,

A meteor is a meteoroid that has entered the atmosphere and is burning up. A meteoroid is a rock composed mainly of iron. An asteroid is a large meteoroid.

A comet is composed mostly of frozen water and other gases. Only a meteoroid that enters the atmosphere is considered a meteor. A comet that enters the atmosphere would still be a comet.

 

When I was kid a large (or flashy, anyway) meteor exploded at the end of its trail one night - made a bang, or maybe that was sonic boom - some pieces kept going. People talked about it for a while.

It might no be all that rare.

I would expect it to take a while for the middle to heat up to boiling, and the pressure to increase dramatically as thicker air braked it harder. The Tunguska comet blew up at 6 - 8 kilometres.

Seems like a lot would depend on its approach angle.

http://www.springerlink.com/content/v3742lw45q383171/ These guys have some stuff figured out.

 

iceaura,

Interesting. Now that you mentioned it, as a meteor slows down in the atmosphere and reaches the speed of sound, a sonic boom would occur which might cause it to break up. The only problem is that there is a pretty big difference between a meteor breaking up, with chunks flying in different directions, and a meteor exploding. As far as I know, there were no meteor pieces found in the Tunguska region after the explosion. It appears that whatever it was, it was completely vaporized.

 

Dragon: What makes you think anyone has a clue about the trajectory?

The way it exploded.What do you mean by that? How many ways are there for something to explode?

Why not Post your thoughts in the pseudo science forum and not bring UFO speculation here.

 

I think I see what the op means. Why does a comet catastrophically disrupt instead of coming down in one piece? The drag on lots of little pieces is greater than on one big piece. (proportional to surface area more than cross section) Drag determines the rate of conversion of kinetic energy to heat. So when a comet starts to come apart heating (the 'wattage' as is were) can spike rapidly and accelerate further breakup. Boom.

 

Actually, I think it was a combination of the heat wearing away at the asteroid and making it more brittle when the sonic boom shattered it. Sonic booms go in all directions, so it wouldn't surprise me it was in the middle of the atmosphere when the sonic boom happened, which shattered the already fragile meteor, creating an area of high air pressure momentarily. The shockwave from the explosion combined with the high air pressure probably flattened the trees while the noise, which started in the middle of the atmosphere, spread across the world. Does that sound likely?

And it has been said that meteors that have a high rate of descent, which have never been in an atmosphere, would be like a sub going to crush depth. In other words, it can't with stand the sudden change in pressure and implodes.

 

A group of researchers believe they have actually found an impact crater from a part of the body that remained after the airburst. It is in the form of a lake with an unusual bed topography and a possible object in the bottom that can be picked up by seismic reflection:
http://www.blackwell-synergy.com/doi/pdf/10.1111/j.1365-3121.2007.00742.x
http://www-th.bo.infn.it/tunguska/

 

There were some subsidiary explosion epicenters - eight or nine of them, IIRC (three or four, according to the link above) - marked on the ground, and still visible. The thing apparently broke up, either from the first explosion or just before it, and the pieces blew up as well. At least, that's what it looks like.

If it was mostly dirty ice, as many comets are, with only a small central water-saturated rock core (mostly destroyed in the explosion) we wouldn't expect to find many pieces.

The sonic boom itself would not have affected it - but it was being subjected to large buffieting forces , adding to the pressure spike from decelleration and increasing atmospheric pressure.

 

Nothing can be ruled out, every known possibilty has to be considered!
UFO's ,comets, meteors, scalar weapons etc.

 

...Tesla's death ray....