December 18, 2007
Tunguska Simulation Shows Higher Risk From Smaller Asteroids

Smaller asteroids are more dangerous than previously thought.

ALBUQUERQUE, N.M. — The stunning amount of forest devastation at Tunguska a century ago in Siberia may have been caused by an asteroid only a fraction as large as previously published estimates, Sandia National Laboratories supercomputer simulations suggest.

“The asteroid that caused the extensive damage was much smaller than we had thought,” says Sandia principal investigator Mark Boslough of the impact that occurred June 30, 1908. “That such a small object can do this kind of destruction suggests that smaller asteroids are something to consider. Their smaller size indicates such collisions are not as improbable as we had believed.”

Because smaller asteroids approach Earth statistically more frequently than larger ones, he says, “We should be making more efforts at detecting the smaller ones than we have till now.”

We need to search harder for the larger number of smaller asteroids. Our risk of death and destruction from asteroids is larger than previously believed.

The Tunguska blast has a downward direction that amplifies its destructive effect on the surface of the Earth.

Simulations show that the material of an incoming asteroid is compressed by the increasing resistance of Earth’s atmosphere. As it penetrates deeper, the more and more resistant atmospheric wall causes it to explode as an airburst that precipitates the downward flow of heated gas.

Because of the additional energy transported toward the surface by the fireball, what scientists had thought to be an explosion between 10 and 20 megatons was more likely only three to five megatons. 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.

We should try much harder to identify the asteroids that are going to collide with the Earth in the future. The sooner we identify them the easier it will be to deflect them from their paths.

The Tunguska event felled over 80 million trees and is a topic of active research which has generated lots of cool photographs.

Share |      Randall Parker, 2007 December 18 10:42 PM  Dangers Asteroids

Geoff said at December 19, 2007 5:53 AM:

Actually I was researching something else and the Tunguska Event turned out to be the solution to my problem.

Something like looking for an egg and instead finding the chicken.



Brett Bellmore said at December 20, 2007 5:42 PM:

I agree, we desperately need a near Earth asteroid observatory. A special purpose telescope placed in solar orbit, closer to the Sun than Earth, so that it can get a well lit view of asteroids at the Earth's range from the sun, or closer, would seem to be in order. I'm continually amazed that Nasa doesn't do something like that.

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