Archaeologica.org

Tunguska Blast Was a Small Asteroid
December 19, 2007

The Tunguska event, an explosion on June 30, 1908, cleared an 800-sq.-mi. swath of Siberian forest. Was it a UFO crash? An alien weapons test? Now, Sandia National Laboratories has released its own explanation for the Tunguska event. Using supercomputers to create a 3D simulation of the explosion, the Department of Energy-funded nuke lab has determined that Tunguska was, indeed, the explosion of a relatively small asteroid.
The researchers caution that we should be keeping watch for many more small, potentially earth-impacting asteroids than we are currently tracking.

The simulation videos are well worth checking out — they show a fireball slamming into the earth from the asteroid's air burst: http://www.sandia.gov/news/resources/re ... eroid.html.

Ohmigod!

Do we have any early warning system?

Yeah.

Someone shouts "Look out!"

Someone shouts "Look out!"

Or if you're really short of time try 'Duck!'

The physical size of the asteroid, says Boslough, depends upon its speed and whether it is porous or nonporous, icy or waterless, and other material characteristics.

At last! It's about time astronomers mentioned this, asteroids can be carbonaceous, nickel/iron, or stony, and perhaps combinations of the above.
A carbonaceous one would be extremely unlikely to survive an atmospheric collision, and a nickel/iron one would be unlikely to explode.
Aside from size or structure velocity is of the greatest importance. The same object striking on the equater in the same direction as the Earth's rotation and in phase with our orbit would be less destructive than if it struck out of phase.
What's happend to Monk by the way, haven't heard from him for some time?

I think he still has to work for a living. Doesn't get to sit around like us old farts, all day.

Doesn't know what he's missing does he Min?