Asteroid data:
Diameter: 1km
Speed: 20km/s
Angle: 45
Composition: Mainly iron
Explosion: More than 100000 megatons of TNT

What would happen if an asteroid with a diameter of one kilometer would hit Estonian capital Tallinn, right in the middle of the city?

Luckily the probability of such an event is really small because asteroids of that size find their way to earth roughly once in a million years.

To the world as a whole, it would have little impact (aside of emotional because i know you guys would miss me ). But for Estonia it would mean utter devastation. Instead of Tallinn there would a rougly 19 kilometer hole in the ground with a depth of around 7 km. The explosion would cause a fireball with a diameter of 13kilometers and the the fireball would last for over 3 minutes. Tartu, which is situated roughly 200km from Tallinn would also be devastated, people would suffer 3rd degree burns, trees and grass would catch fire. In addition, the explosion would cause an 8 degree earthquake which would reach Tartu in 36 seconds after the impact.

And even that wouldnt be the end of it. 10 minutes after the impact, the shockwave would reach Tartu, destroying what is left from the previous events. The winds would reach speeds of 100m/s.

Our neighbours wouldnt be safe either, Helsinki would be totally devastated and they would face an even greater damage from a giant Tsunami. (The rough distance between Helsinki and Tallinn is 90km) The Tsunami would also reach Stockholm.

This cenario was created by using a programm created by the scientist of Arizona University.

Heh...yeah, relatively small things colliding with earth at that speed can cause insane damage. I actually watched a NGC program on probability of such an impact, if we would/could see it coming and what we could do about it.

Interestingly, most major space agencies have been developing means of decreasing their dangerousness and/or destroying them before they hit earth for years. The movie Armageddon was based on one of the scenarios.

If you're into that shit you should read up on the Tunguska event...MASSIVE explosion caused by (probably) a meteorite exploding just before impact.

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

100,000 megatons of TNT, probably. That's usually what measures really explosive events like nuclear weapons. Hiroshima was around 20kilotons of tnt, if I remember correctly. The largest nuclear bomb was in the 25 gigaton range, I think. The above asteroid would unleash 100 gigatons.

But, doesn't that imply that if we hit this asteroid with a 100 gigaton nuclear weapon that we'd vaporize the sucker? If we could create 25 gigaton nukes in the 60s, then surely we could make 100 gigaton nukes now.

That would only work if it truly vaporized the thing. Even when an asteroid breaks up/explodes, its debris tend to stay on the same (crash) course.

So if you're break up something of a km into a hundred pieces of 10 metres you'd avoid a massive impact but you would also create a deadly hail with smaller but no less deadly impacts if they'd be heading for a densely populated area.

Probably still better than one huge blast, but obviously not ideal.

heh...as long as the pieces are small enough to burn up in the atmosphere, no big deal. Ideally though you wouldn't hit the asteroid head on or close to the planet. Instead hit it from the side and a decent distance away... that way you deflect it off course to hopefully miss the planet entirely. Shattering it would be a bonus (less chance of it being a major threat in the future).

Then again, these things are like mostly metal, right? So they probably wouldn't shatter like rock, they'd just melt. Still, if you hit it from the side all the boiling metal should create enough lateral thrust to hopefully move it off an impact course. Either that or we could use nukes to steer it into Iran or something.

Hehehe...according to that NGC show they can actually vary pretty much in their make-up. Some are solid-ish, others are mushy. They even talked about a scenario in which an asteroid would 'swallow' a warhead. Awesome. Space porn!

But seriously, they're usually a bunch of space garbage encased in ice.

http://www.enchantedlearning.com/subjec ... tion.shtml

ah, cool. Well, ice is good. Boiling it off with a nuke would work. Whatever, we need a bunch of nukes in orbit. In orbit around the moon would be even better. Or sitting in a lagrange point.

Oh God...why'd you post that link bastard? Now I have to read it because I can't stand not knowing what it means

hehe... lagrange points are cool. A lot cooler than geosynchronous orbits.