What is the difference between an asteroid, a comet, a meteor and a meteorite?
Same sky, four words: the difference is mostly about size, ice and where the thing happens to be.
▶ Start the storyThese four words describe the same family of space rocks, and they differ in three ways: size, ice, and where the object is at that moment.
Start with the objects in space. An asteroid is a rocky, metallic or sometimes icy body with no atmosphere, roughly a metre across or bigger. A meteoroid is the small version, from a grain of dust-like debris up to about a metre wide. A comet is different in kind rather than size: it is an icy body that warms and releases gas when it passes close to the Sun, and that gas can make a glowing tail. Asteroids are more like rocks and form no tail.
Asteroid
- Rocky, metallic or icy, no atmosphere
- Roughly a metre or larger
- Forms no tail
- Most orbit between Mars and Jupiter
Comet
- Icy body that releases gas near the Sun
- Can grow a coma and a tail
- Short-period ones come from the
- Long-period ones come from the
The other two words describe what happens when one of these things meets Earth. The visible streak of light when something enters our atmosphere is a meteor. If a piece survives the fall and lands, what is left is a meteorite. So a single rock can be a meteoroid in space, a meteor in the sky and a meteorite on the ground.
This is not rare. An estimated 25 million meteoroids and bits of dust enter the atmosphere every day, adding up to about 15,000 tonnes a year. Almost all burn up as faint streaks. In 2008 astronomers spotted a 4-metre asteroid, 2008 TC3, heading for Earth, and it struck a remote area of northern Sudan the next day. It was the first time a meteoroid had been tracked in space before it hit.
The line between asteroid and comet is not perfectly sharp: some bodies in the asteroid belt have been found to behave like comets.
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Recap
In space it is a meteoroid or an asteroid, in the sky it is a meteor, and on the ground it is a meteorite; comets are the icy ones with tails.
💡 A trick to remember it · Meteor is in the air, meteorite is on the ground you can stand on, and a comet is the one with the tail.
Surprising fact · About 25 million meteoroids and dust particles enter Earth's atmosphere every day, around 15,000 tonnes a year.
Sources (3)
No source, no claim. Every fact in this lesson (14 claims) cites at least one of these.