Asteroid explosions

[Mokele]

I've been poking around recently about asteroids and, more specifically, what happens when one hits us. Cratering is fairly obvious, but much of what I read concerned asteroids 'exploding' in the atmosphere, and indicates that it's fairly frequent.

 

What I'm a bit fuzzy on is exactly how an large lump of fairly inert rock can 'explode'. The first idea that comes to my head is that it's like when a piece of material under force loading finally breaks; the sudden failure produces a pressure wave which, when it reaches our ears, if percieved as sound.

 

So, is the explosion of an asteroid in the atmosphere basically a big version of the same principle, just under a lot more force and producing a much more powerful shockwave when it finally breaks under the forces it's experiencing?

 

Mokele

[5614]

I was under the impression that they 'burnt up' in out atmosphere rather than exploded.

[Ophiolite]

Meteoroids will burn up. Asteroids are far too large.

 

I suspect a lot depends upon the velocity and angle of attack. Generally the velocity will be sufficiently high so that the entire atmosphere can be penetrated in a few seconds. The compression (and heating through compression) of the air in front of the asteroid is substantial. That can be sufficient to induce stresses in the smaller bodies (metres to tens of metres) that cause them to fracture. Those on more gentle trajectories may cause less compression, but are subject to those stresses for a longer time.

[coquina]

Read this article about what an impact did to the the area that is now the Chesapeake Bay 35 million years ago.

 

http://woodshole.er.usgs.gov/epubs/bolide/

 

Here's the USGS website about research on the crater.

 

http://geology.er.usgs.gov/eespteam/crater/

[[Tycho?]]

I believe it superheats water in the rock that causes the explosion.

 

Thats what caused that huge explosion in siberia in the early 1900s. I'll look for a link.

 

edit: ah, here we are: http://en.wikipedia.org/wiki/Tunguska_event

[[Tycho?]]

I believe it superheats water in the rock that causes the explosion.

 

Thats what caused that huge explosion in siberia in the early 1900s. I'll look for a link.

 

edit: ah, here we are: http://en.wikipedia.org/wiki/Tunguska_event

[coquina]

Here's a link to Sandia Nat'l labs. They used a super computer to simulate an impact in the ocean off NYC.

 

http://www.sandia.gov/media/comethit.htm

[coquina]

Here's a link to Sandia Nat'l labs. They used a super computer to simulate an impact in the ocean off NYC.

 

http://www.sandia.gov/media/comethit.htm

[Halash]

they prolly explode becuase of pockets of methane inside the astroid exploding when they are explosed to high temps during reentry... am i right?

[Halash]

they prolly explode becuase of pockets of methane inside the astroid exploding when they are explosed to high temps during reentry... am i right?

[coquina]

http://curious.astro.cornell.edu/question.php?number=146

 

What would happen if an asteroid 10 kilometers across hit the Earth?

If an asteroid / meteorite of about 10 km in diameter hit either a) land or b) ocean, on earth, what may happen?

 

For an asteroid 10 km in diameter, it doesn't matter where it hits, ocean or dry land. Remember that the depest point in the oceans is in the Mariana Trench, and is only 11 km deep! Also, a typical speed for meteorites is around 30 kilometers per second. An asteroid 10 kilometers across is so massive that it's very hard to slow it down. Unlike smaller meteors, it will not be slowed down much by air friction. It will punch through the atmosphere like it's hardly even there. When it reaches the surface, it will smack so hard that it won't matter if it strikes ocean or land.

 

The imapact with the earth's crust will finally stop the asteroid. The energy of the impact will vaporize the asteroid and a large amount of the Earth's crust, creating a crater more than one hundred kilometers across, throwing all that rock into the air.

 

Some of this debris will be going so fast that it will fly right out of the Earth's atmosphere and go into orbit around the Earth. Most of the debris will rain back down on the Earth--every part of the Earth, not just near the impact site--heating the atmopshere until it's like the inside of an oven, triggering forest fires and cooking anything that isn't sheltered underground.

 

The combination of dust from the impact and soot from the forest fires will remain in the Earth's atmosphere for a year or so, blocking the light of the Sun. Without sunlight, much of the Earth's plantlife, on land and in the sea, will die.

 

Many species of animals--including the human race, if we aren't both lucky and resourceful!--will die out, either in the initial catastrophe, or in the ensuing years due to lack of food and the general devastation of the environment.

 

The last time this happened was 65 million years ago, when an asteroid struck the Earth, creating the Chicxulub Crater in Mexico and causing the extinction of the dinosaurs. On average, an asteroid this size strikes the Earth every 50 to 100 million years.

 

 

July 2002, Britt Scharringhausen (more by Britt Scharringhausen)

 

 

Pieces of the impactor are not generally found. Instead, the tell tale debris from a large impactor are pieces of glassy material that were melted by the impact and thrown through the atmosphere. They are called "tektites".

 

Here's a site from the Georgia Mineral Society where you can read about them:

http://www.gamineral.org/Tektites.htm

[coquina]

http://curious.astro.cornell.edu/question.php?number=146

 

What would happen if an asteroid 10 kilometers across hit the Earth?

If an asteroid / meteorite of about 10 km in diameter hit either a) land or b) ocean, on earth, what may happen?

 

For an asteroid 10 km in diameter, it doesn't matter where it hits, ocean or dry land. Remember that the depest point in the oceans is in the Mariana Trench, and is only 11 km deep! Also, a typical speed for meteorites is around 30 kilometers per second. An asteroid 10 kilometers across is so massive that it's very hard to slow it down. Unlike smaller meteors, it will not be slowed down much by air friction. It will punch through the atmosphere like it's hardly even there. When it reaches the surface, it will smack so hard that it won't matter if it strikes ocean or land.

 

The imapact with the earth's crust will finally stop the asteroid. The energy of the impact will vaporize the asteroid and a large amount of the Earth's crust, creating a crater more than one hundred kilometers across, throwing all that rock into the air.

 

Some of this debris will be going so fast that it will fly right out of the Earth's atmosphere and go into orbit around the Earth. Most of the debris will rain back down on the Earth--every part of the Earth, not just near the impact site--heating the atmopshere until it's like the inside of an oven, triggering forest fires and cooking anything that isn't sheltered underground.

 

The combination of dust from the impact and soot from the forest fires will remain in the Earth's atmosphere for a year or so, blocking the light of the Sun. Without sunlight, much of the Earth's plantlife, on land and in the sea, will die.

 

Many species of animals--including the human race, if we aren't both lucky and resourceful!--will die out, either in the initial catastrophe, or in the ensuing years due to lack of food and the general devastation of the environment.

 

The last time this happened was 65 million years ago, when an asteroid struck the Earth, creating the Chicxulub Crater in Mexico and causing the extinction of the dinosaurs. On average, an asteroid this size strikes the Earth every 50 to 100 million years.

 

 

July 2002, Britt Scharringhausen (more by Britt Scharringhausen)

 

 

Pieces of the impactor are not generally found. Instead, the tell tale debris from a large impactor are pieces of glassy material that were melted by the impact and thrown through the atmosphere. They are called "tektites".

 

Here's a site from the Georgia Mineral Society where you can read about them:

http://www.gamineral.org/Tektites.htm

[Mokele]

As much as I appreciate the information on impacts, I was actually refering to instances in which the asteroid "explodes" during it's descent, before it actually impacts.

[Mokele]

As much as I appreciate the information on impacts, I was actually refering to instances in which the asteroid "explodes" during it's descent, before it actually impacts.

[coquina]

These objects enter the atmosphere at incredibly high rates of speed - from 20 to 70 km per second.

 

Here's a program you can play with to simulate the effects of an impact.

http://www.lpl.arizona.edu/impacteffects/

 

In the example I put in, the explanation said the object started to "break up" upon entering the atmosphere, rather than "exploding" - I think the explosion/vaporization comes later - right before impact. But if you're talking about an entry speed of 70 km per second "later" is rather insignificant.

[coquina]

These objects enter the atmosphere at incredibly high rates of speed - from 20 to 70 km per second.

 

Here's a program you can play with to simulate the effects of an impact.

http://www.lpl.arizona.edu/impacteffects/

 

In the example I put in, the explanation said the object started to "break up" upon entering the atmosphere, rather than "exploding" - I think the explosion/vaporization comes later - right before impact. But if you're talking about an entry speed of 70 km per second "later" is rather insignificant.

[JohnB]

I believe it superheats water in the rock that causes the explosion.

Tycho, I've always had trouble with that explanation. While I agree it would cause a bang, in the case of Tunguska we are talking 10-15 Megatons in power.

 

Getting a 10 megaton blast from superheated steam just doesn't sound credible. We are talking about a bang 500 times bigger than Hiroshima.

 

I don't know what it was, but a rock exploding from internal steam pressure? It just doesn't ring true.

 

An interesting side note to Tunguska is that there was no increase in backgroung radiation, but the plants in the area are showing genetic deformities. Unusual.

[JohnB]

I believe it superheats water in the rock that causes the explosion.

Tycho, I've always had trouble with that explanation. While I agree it would cause a bang, in the case of Tunguska we are talking 10-15 Megatons in power.

 

Getting a 10 megaton blast from superheated steam just doesn't sound credible. We are talking about a bang 500 times bigger than Hiroshima.

 

I don't know what it was, but a rock exploding from internal steam pressure? It just doesn't ring true.

 

An interesting side note to Tunguska is that there was no increase in backgroung radiation, but the plants in the area are showing genetic deformities. Unusual.

[us.2u]

That's awesome & indeed scary I guess each day we see the morning sun we should smile at it & say thank-you well here's a big smile from me; to our mother earth I won't look at doom & gloom; but just share this planet with my children wey-hey wishing you all a great week....us.2u

[Guest ImpFetus]

Ok here my hypothesis on it: if you came down through an atmosphere at several km a second you would be vaporized! Same goes for a meteor, at least its outer surface, as it enters the atmosphere the strain on it could cause it to break apart, especially if this is a small asteroid made of dust, sand or small pebbles or a small comet made of dirty snow. Breaking up increasing it surface area allowing a lot more rock to get vaporized quicker, now if we are talking about a meteor that disintegrates into dust or sand and that material then instantly vaporizes, all the kinetic energy of the meteor has been transferred as heat in to the air, and thus KABOOM!

[JohnB]

But as the rock broke up, the small particles would decelerate faster than the main body and therefore be moved away from it. They wouldn't be in the one place to go "Bang".

 

I'm sure that I've read that meteors do indeed explode in much the way you describe, but a Megaton range explosion? That's where I have problems.

[Ophiolite]

I'm sure that I've read that meteors do indeed explode in much the way you describe, but a Megaton range explosion? That's where I have problems.

Kinetic energy, the energy of motion, is determined by this equation:

 

Kinetic Energy = 1/2 mv^2

 

Where m is the mass in kilograms and v is the velocity in metres/second

 

Take a typical bolide, say 50m in diameter, with a mass in the region of 200,000,000 kgs, coming in at say 30 kms/second. That computes to a K.E. of 9E+16 joules. Convert from joules to megatons(I megaton = 4.18 E+15 joules) gives you a yield of approximately 20 megatons TNT equivalent.

 

Problem solved?

[[Tycho?]]

Kinetic energy' date=' the energy of motion, is determined by this equation:

 

Kinetic Energy = 1/2 mv^2

 

Where m is the mass in kilograms and v is the velocity in metres/second

 

Take a typical bolide, say 50m in diameter, with a mass in the region of 200,000,000 kgs, coming in at say 30 kms/second. That computes to a K.E. of 9E+16 joules. Convert from joules to megatons(I megaton = 4.18 E+15 joules) gives you a yield of approximately 20 megatons TNT equivalent.

 

Problem solved?[/quote']

 

The above is quite large for a meteorite, most that hit the earth are far smaller. It does get the point across though, since velocity is squared, and these objects are moving through space, they have a huge amount of energy behind them.

[Ophiolite]

'']The above is quite large for a meteorite, most that hit the earth are far smaller. It does get the point across though, since velocity is squared, and these objects are moving through space, they have a huge amount of energy behind them.

Absolutely, but if you recall JohnB was bothered by the reported energy for the Tunguska event, so I picked something that would deliver a comparable energy. I believe current thinking has Tunguska down as a comet, and I assumed an iron meteorite, so the Tunguska bolide, with lower density, would have been somewhat larger.

[coquina]

Ophie - can you estimate the megatonnage of the Chesapeake Bay impactor based on the following info?

 

I have spoken with the scientists that are doing this research and I asked them what the best guess was on the size of the impactor - they told me about 3 miles in diameter. They don't know the incoming speed - somewhere between 20 and 70 km/sec.

 

From the article - describing the size of the crater:

The bolide carved a roughly circular crater twice the size of the state of Rhode Island (~6400 km2), and nearly as deep as the Grand Canyon (1.3 km deep).

 

More background info:

http://woodshole.er.usgs.gov/epubs/bolide/ancient_cataclysm.html

 

 

http://woodshole.er.usgs.gov/epubs/bolide/faulting.html

 

There is evidence that it created a tsunami that went all the way to the foot of the Blue Ridge Mountains - 150 miles inland.