Could super fast, super durable asteroid enter low atmosphere in Earth and leave?

[phemark]

Hi,

While doing aerobreaks in KSP, question popped up in my head:

(Please use these two assumptions:

Asteroid is super durable/indestructible.

Asteroid's PE is in the middle of Pacific ocean - (so flat spot on Earth))

Could an asteroid, of any mass, coming super fast from deep within space, get into Earth's orbit and leave it? (I think it probably could in upper levels of atmosphere.)

However, could it reach 1-100 meters above Pacific's sea level, and then escape? What speed would be needed? Is this speed achievable in the universe?

If yes, could we ignore the assumption of indestructible asteroid, or is there no material in universe that would bare this stress?

Thanks for your theory crafting:)

[Urban_K]

Inside atmosphere and leave? Yes:

http://en.wikipedia.org/wiki/Grand_Teton_Meteor

[phemark]

Inside atmosphere and leave? Yes:

http://en.wikipedia.org/wiki/Grand_Teton_Meteor

Thanks for this.

Now moving to hypothetical example - instead of 57km, could asteroid come closer than 1km (or as close as 1 meter), and then leave? What speed,mass and durability an asteroid would need to be?

[Ralathon]

It is absolutely possible, but its going to be very hard to figure out exact numbers.

Aerodynamic drag is a very complicated problem that depends on a ridiculous number of variables. Your results will vary based on the shape of your asteroid, the size, the surface roughness, local weather, the phase of the moon etc etc etc. Calculating how such an object behaves is the cutting edge of computational fluid mechanics.

Whether or not the asteroid 'survives' depends on the size. Heat capacity scales to the 3th power of radius, so a big asteroid can soak up more heat before it burns up. So I'm fairly sure that something a few dozen km across will survive, but again I can't give you exact numbers.

[phemark]

It is absolutely possible, but its going to be very hard to figure out exact numbers.

Aerodynamic drag is a very complicated problem that depends on a ridiculous number of variables. Your results will vary based on the shape of your asteroid, the size, the surface roughness, local weather, the phase of the moon etc etc etc. Calculating how such an object behaves is the cutting edge of computational fluid mechanics.

Whether or not the asteroid 'survives' depends on the size. Heat capacity scales to the 3th power of radius, so a big asteroid can soak up more heat before it burns up. So I'm fairly sure that something a few dozen km across will survive, but again I can't give you exact numbers.

Sounds cool:)

I wonder if anyone have a possibility to run these simulations.

Follow up question:

Assume that this happens, and Asteroid 10-100km wide fly by's by Pacific ocean at 1 meter altitude and leaves at very high speed. What would happen? Would water move a lot? Would atmosphere heat up a lot? Would it shift? What if same thing happened 100m above the city (but didnt touch it)?

(Sorry for many answers, but I'm very curious:D)

[Ralathon]

Sounds cool:)

I wonder if anyone have a possibility to run these simulations.

Follow up question:

Assume that this happens, and Asteroid 10-100km wide fly by's by Pacific ocean at 1 meter altitude and leaves at very high speed. What would happen? Would water move a lot? Would atmosphere heat up a lot? Would it shift? What if same thing happened 100m above the city (but didnt touch it)?

(Sorry for many answers, but I'm very curious:D)

The result is equivalent to a few thousand nuclear bombs going off above your head. The radiant heat alone will vaporize a large part of the surface (whether it's water or city). The Tunguska event was caused by a body of less than a 100 meters. So the energy carried by a body a few km in size is enormous. It likely causes a mass extinction equivalent to the one that offed the dinosaurs.

[Idobox]

Don't forget you have a massive chunk of rock traveling faster than escape velocity at sea level. The shockwave would be absolutely massive.

[phemark]

Wow, so asteroid, which woundnt even hit the surface, would still make us all extinct.

I imagined massive shockwave, but maybe not at this magnitude:)

[-Velocity-]

The result is equivalent to a few thousand nuclear bombs going off above your head. The radiant heat alone will vaporize a large part of the surface (whether it's water or city). The Tunguska event was caused by a body of less than a 100 meters. So the energy carried by a body a few km in size is enormous. It likely causes a mass extinction equivalent to the one that offed the dinosaurs.

Yes, but it wouldn't deposit ALL of its energy if it re-escaped into space. It might actually retain most of its energy, and only lose like a tenth of it to Earth's atmosphere, if this hypothetical super-durable asteroid were large enough. Still, 1/10th of 100,000,000 atomic bombs is still a lot

Still, it's never gonna happen.

[Horn Brain]

The amount of air that an object can push aside at hypersonic speed is something like it's own mass. This is Newton's impact depth approximation and it works pretty well. This works out to be a relationship between the density of an asteroid that can pierce a given column of air and it's radius. If you look up air mass, you'll see that at the horizon, the column of air you're looking through has about 38 times as much mass as the column of air directly over your head, which has an areal density of about (sea level density) * (atmospheric scale height). So 2*38*(sea level density)*(atmospheric scale height) is about 824 tons per meter squared of cross-sectional density for an asteroid.

Since the asteroid's mean cross-sectional density is approximately (4/3)*(density)*(radius) (divide mass of a sphere by pi r^2), we get a relationship between asteroid density and minimum radius to pierce the atmosphere. The denser the asteroid (x axis) the smaller it can be (in meters on the y axis). If we have an iron asteroid, the radius would have to be around 80 km.

That's the minimum size from a purely momentum-based view. It may have to be bigger to handle the heat load, it may have to be unphysically strong to avoid being ripped apart. If you notice, this 160 km rock sitting 1m off the surface of the ocean has its top in space. So it's pretty much not going to happen the way you're imagining it.

Edited April 11, 2014 by Horn Brain
factor of ten

[Moar Boosters]

if it's travelling fast enough for our atmosphere to not slow it down below escape velocity, you've gotta consider Newtons laws.

It would accelerate large amounts of the atmosphere it interacts with to escape velocity, so if it's big enough it could literally blow half our atmosphere out into space.

Some theories point to something similar happening to Mars several billion years ago, turning a once oxygen and water rich planet into what we see today.

[lajoswinkler]

Here's a thought for you all. You know those shiny, huge meteors we call bolides? They're caused by pebble-sized meteoroids. You can calculate the rough area they're exciting into a glistening shine.

Now imagine a 1 km body, with orders of magnitude more surface area. Do you know what would happen? Almost anyone who would be able to see it would be fried to death just because of the heat radiation of the entry. It would be like a trail of continuous flash, brighter than a fairly large atomic exploxion. It would cause everything in its path to erupt into flames even before it impacts. An atomic bomb flashes and then its luminosity drops down very fast. This would be a continuous brightness. A mayhem.

[phemark]

Thanks for all the theory guys, interesting stuff

[Idobox]

The amount of air that an object can push aside at hypersonic speed is something like it's own mass. This is Newton's impact depth approximation and it works pretty well. This works out to be a relationship between the density of an asteroid that can pierce a given column of air and it's radius. If you look up air mass, you'll see that at the horizon, the column of air you're looking through has about 38 times as much mass as the column of air directly over your head, which has an areal density of about (sea level density) * (atmospheric scale height). So 2*38*(sea level density)*(atmospheric scale height) is about 824 tons per meter squared of cross-sectional density for an asteroid.

Since the asteroid's mean cross-sectional density is approximately (4/3)*(density)*(radius) (divide mass of a sphere by pi r^2), we get a relationship between asteroid density and minimum radius to pierce the atmosphere. The denser the asteroid (x axis) the smaller it can be (in meters on the y axis). If we have an iron asteroid, the radius would have to be around 80 km.

That's the minimum size from a purely momentum-based view. It may have to be bigger to handle the heat load, it may have to be unphysically strong to avoid being ripped apart. If you notice, this 160 km rock sitting 1m off the surface of the ocean has its top in space. So it's pretty much not going to happen the way you're imagining it.

You are assuming a straight trajectory tangential to the ocean. In real life, you would get serious lift from the shock-waves bouncing on the surface, so you could have a V or U-shaped trajectory that would go through a lighter air column. That would still make a very big asteroid.

[Starwhip]

The answer is yes. In theory. The answer is always "yes" in theory. Will it ever happen? Probably not.

[TheDataMiner]

Imagine if you were the poor fisherman who ducked just in time for the asteroid to singe your hair

[Skyler4856]

Imagine if you were the poor fisherman who ducked just in time for the asteroid to singe your hair

Reminds me of a story I heard awhile back about a cow being dropped from a plane