Science & Technology

Despite the Fireball, Meteorites Probably Aren't Hot

What happens when a meteorite hits Earth? If movies are to be believed, a meteorite is a fiery death ball that hurtles through the air with alarming speed until it slams into the ground in an explosion of molten rock and flaming debris that creates an impact crater where it finally rests, red-hot and smoldering. According to science, however, the reality is a little less exciting: Meteorites probably aren't hot when they hit the ground.

What's Really Going On

First things first: Space is cold. Really cold. Barely three degrees above absolute zero cold. That means that the chunks of rock we know as meteoroids are in a deep freeze. When that meteoroid begins hurtling through our atmosphere (and becomes a meteor), they begin to glow with such brilliance that they're visible for hundreds of miles. But it's not the meteor itself that glows; it's the air around it, through something called ram pressure — that is, the compression in the air caused by the meteor's forward motion. Compression makes air heat up, and that's why a falling meteor looks red-hot.

Still, hot air must heat up the meteor, right? Right! But for most meteors, that's only on the outside. The outer layers can get so hot that they melt, but they're quickly blown off in a phenomenon known as ablation. That likely leaves behind un-melted rock that's just warm, at best. There's also the fact that although a meteor's speed peaks at thousands of kilometers per hour, all that air pressure slows it down considerably before it hits the ground, giving it — and the air around it — plenty of time to cool down. Once it lands (and becomes a meteorite), it's a comfortably lukewarm temperature.

You might have noticed that there are a lot of "likelies" and "probablies" in this explanation. That's because very few people have actually touched a meteor right after it lands. Those who have report temperatures that are all over the map: Some meteors were indeed hot, others were cold enough for frost to form on the surface. But these reports are just testimony from individuals; there's never been a scientific survey of many meteorite falls to see what condition they've been in when they land.

What Goes Down Must Come Up

Like many naturally occurring phenomena, humans have borrowed this one for themselves. Spacecraft actually take advantage of the same ablation phenomenon that meteorites experience to protect their delicate equipment from getting too hot. Modern heat shields are large, rounded surfaces covered in a material designed to burn off like the outer layers of a meteor, leaving the cargo and people inside comfortably warm instead of molten hot. 

Get stories like this one in your inbox or your headphones: sign up for our daily email and subscribe to the Curiosity Daily podcast.

They don't come from the sky, but the pieces in this Moon Rock Kit are the next best thing. The kit comes with six hand samples of rocks and minerals similar to those you'd find on the moon. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Ashley Hamer December 30, 2016

Curiosity uses cookies to improve site performance, for analytics and for advertising. By continuing to use our site, you accept our use of cookies, our Privacy Policy and Terms of Use.