Most of the meteoroids who enter Earth's atmosphere weigh just a few

milligrams and are very small. A meteoroid is a piece of metallic or stony debris

which is in outer space. A meteoroid only becomes a meteorite if it ever

reaches the surface of a planet. The largest meteorite ever found, Hoba, weighs

60 tons.

    An average meteoroid would enter the atmosphere between 10 and 70 km a

second. The largest meteoroids are quick to enter the atmosphere. Only

meteoroids larger than a few hundred tons are slowed very little; and large,

and rare meteoroids make craters.

    Most meteoroids are no larger than a grain of sand, and are the smallest

object orbiting the sun. Meteoroids are referred to as meteors when they enter

Earth's atmosphere. In the atmosphere most meteors completely burn up at

altitudes of between 60 and 80 miles. After the meteors burn up in the

atmosphere their remains fall to the Earth's surface as dust.