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Sorting Out Asteroids, Comets and Meteors in the Celestial Scheme

April 08, 2002

What is an asteroid?

An asteroid is a big rock, often called a minor planet, that circles the sun. Asteroids are leftover material from the formation of the solar system and range from 580 miles across to the size of large boulders.

How are asteroids different from comets? Or meteors?

Comets are large blobs of ice and dust that streak across the sky. Meteoroids--as meteors are known while in deep space--are small objects, usually fragments of asteroids. When they enter Earth's atmosphere and produce a flash of light, they are called meteors. Meteorites are what these same rocks are called once they have fallen to the surface of the Earth.

How large are the craters that space rocks produce?

Craters are much larger than the falling asteroids or comets that produce them because of the explosive force generated by the impact. For example, the 10-mile-diameter asteroid or comet that helped kill off the dinosaurs left a 110-mile-wide crater in the Yucatan.

Source: Stephen P. Maran, "Astronomy for Dummies"

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