Meteoroids, meteors, meteorites, comets. All interchangeable words for basically the same thing, right? A rock flinging through the night sky. Simple enough –
– but wrong. There’s a reason these four phenomenon all have different names. True, they all stem from roughly the same thing, but their progression through our solar system – and occasionally our atmosphere – requires a change in terminology. This article will explain the difference between meteoroids, meteors, meteorites and comets, and why knowing the difference is important.
Meteoroids are clumps of debris moving through the solar system, often at incredibly high speeds. Meteoroids, by contrast with much larger asteroids – indeed, some asteroids can reach incredible incredible sizes, a constant subject for outer space disaster fiction in particular – are quite small, usually reaching the size of a small boulder at largest. Given their size and distance from the Earth, meteoroids are not typically visible from the planet’s surface.
Meteors, by contrast, are often visible from Earth. They are, in a sense, the second stage of a meteoroid, one that has gotten too close to the planet’s atmosphere and is beginning to burn up upon entry. The visible streak left behind by a meteor is the effect the atmosphere has on the descending object and, typically, that which will burn it up, long before it hits the planet. Particularly bright meteors are known as fireballs.
Not every meteor perishes during the descent to the Earth, however, and those that survive the trip become the last of the lot: meteorites. These rocks manage to hit the planet and remain intact, though usually much diminished from their original size thanks to the wearing effect of the atmosphere. Meteorites can come from meteoroids and asteroids alike, and to the casual eye don’t look much different from normal rocks. (Here’s a quick, painless web page for identifying potential meteorites.)
Where do comets fit into this progression? They’re still chunks of debris soaring through the solar system at great speeds, but comets, unlike the above rocky formations, also include a substantial amount of ice and frozen gas in their makeup. When they get close enough to the sun the solar radiation reacts with the core of the comet, sublimating the ice back into a gas. This rapid change causes the comet to adopt a bright coma and, typically, a streaking tail. Comets are just as capable of striking celestial bodies like the Earth, and thus are no less dangerous than any of the other objects noted above – they’re just prettier.
Despite the distressing prospects of any of these bodies striking the planet, there are plenty of perfectly harmless meteor showers every year, and though there are no accurate numbers it’s surmised that thousands upon thousands of meteors streak into the atmosphere and dissipate before hitting the Earth. So fret not, as these rocks from the sky are not a major threat.
