Definition: Meteorites are pieces of solar system debris that have fallen to Earth from space. Prior to reaching Earth's surface, a meteorite is called a "meteor" or "meteoroid.")
Composition: Rock or metal
Size: Most meteorites are tiny, smaller than grains of sand, and vaporize as they pass through the earth's atmosphere. Larger meteorites may be as great as a few miles wide, such as one 65 million years ago that may have wiped out the dinosaurs. The largest intact meteorite found in the USA is the Williamette Meteorite, at 15 and a half tons.