Fewer Asteroids Threaten the Earth

[Fraser]

SUMMARY: Researchers have built a computer simulation that better predicts how large asteroids will interact with the Earth's atmosphere. They found that more asteroids blow up in the atmosphere than previously thought, reducing the risk of them hitting populated areas or causing tidal waves. Their model says that an asteroid has to be 200 metres in diameter or above before it can get through the atmosphere, and these only hit the Earth once every 170,000 years.

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[GOURDHEAD]

Ah-h-h-h-h what unparalleled hubris allows one to think he can sufficiently accurately model a system of the level of complexity of an asteroid impacting the Earth through its atmosphere. So many variables over such large ranges will pertain. Any result will occasionally be correct and no result will always pertain.

Can anyone help me understand what causes these objects to explode prior to impacting with the surface? My thinking is limited by the oversimplified model which assumes that the thermal conductivity of asteroidal material is less effective than the ablative processes, so I would expect the asteroid, in most cases, to lose its external material via crumbling or ablation before enough heat was passed to its interior to cause the explosion. Is there something about atmospheric buffeting that I don't understand?