After Hours

Fires in the skies

Why are meteorites an unlikely cause of earthbound explosions or fires?

We asked why so-called scorching-hot, high-velocity meteorites are an unlikely cause of earthbound fires and explosions, despite numerous unconfirmed reports to the contrary.

As opposed to what you may have seen in the movies, meteorites are not terribly warm when they hit the ground, and some are even frost-coated. Untrained observers assume that since meteors in the upper atmosphere are visible due to combustion, earth-impacting meteorites must be hot as well. The reality is quite the opposite.

First of all, friction causes the combustion visible from meteors, but it's friction from air rubbing against air—not air rubbing against the meteorite. Meteorites strike the atmosphere at roughly 30,000 miles per hour. At that rate, the air can't move out of the meteorite's way fast enough, creating compression in front of it.

This compression heats the air to the point of combustion, creating the familiar image of a shooting star. But the combustion never actually touches the meteorite. The compression happens so fast that it creates a pocket of relatively cool, slow air between the meteorite and the compressed air, a phenomenon called standoff shock.

The transferred heat literally peels layers off the space rock as part of a process called ablation. With the hot layers peeled away, the core of the meteorite remains cool, thanks to exposure to the vacuum of space. High-altitude air may chill it further once it slows down enough to shed its combustive fireball.

By the time meteorites hit earth, they're moving at perhaps only 200 mph, and they can be as cold as hail or snow. When meteorites have caused documented damage, it's been because of their speed and mass, not their temperature. Even then, reports have usually proven unreliable.

Perhaps the most widely cited example of the first confirmed meteorite injury is the case of Ann Hodges of Sylacauga, AL. On Nov. 30, 1954, Hodges suffered a bruised hip after a meteorite blasted a hole in her roof and ricocheted into her.

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