The Debunker: Are Meteorites White-Hot When They Land?

by Ken Jennings

Lord Almighty, I feel my temperature rising. If you live in the Northern Hemisphere, July is the beginning of the “dog days” of summer, the hottest period of the year. But you know what’s cool on a hot day? Knowledge. Grab a tall glass of lemonade, settle down in a hammock under a shady tree, and let Jeopardy! wunderkind Ken Jennings set you straight on some shamefully persistent misinformation about hot stuff.

The Debunker: Are Meteorites White-Hot When They Land?

First of all, let’s settle this “shooting stars” thing once and for all. Feel free to make a wish on a streak of light in the night sky, but what you’re seeing is, of course, not a star. It’s a meteoroid—a small chunk of a comet or an asteroid. When the meteoroid enters the atmosphere, friction produces a burst of light and heat, which we call a meteor. If the whole thing doesn’t burn up during its descent, a fragment of rock may fall to Earth, at which point it becomes a meteorite. Got it? The order is asteroid -> meteoroid -> meteor -> meteorite.

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The Earth gains 100 tons worth of tiny meteoroid dust every day, including almost 20,000 meteorites greater than 3.5 ounces in mass. So you’d be forgiven for thinking that some of those “shooting stars” must be massive fireballs, like in a sci-fi disaster movie. Why don’t we hear more about grass fires or forest fires caused by meteorites?

Here’s the disappointing truth: when meteorites come to Earth, they don’t make a very dramatic splash. NASA explains that rocky asteroids are poor conductors of heat, so even as the outer layers of the “falling star” burn away due to atmospheric friction, the center remains quite cool. (Remember that the meteorite is coming from millions of years in deep space, at temperatures around a hundred degrees below zero.) The only times that recently fallen meteorites have been observed to be white, it’s not because they were white-hot. In fact, they were covered in frost!

Quick Quiz: Shooting Star was a 2012 EP by electronica musician Adam Young. Young records, and has charted hits like “Fireflies,” under what name?

Ken Jennings is the author of six books, most recently his Junior Genius Guides, Because I Said So!, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at ken-jennings.com or on Twitter as @KenJennings.