Web Sites Devoted To Meteoritics Asteroids , comets , and meteoroids are small solar system bodies composed of rock and ice. They are believed to be debris left over from the formation of our solar system about four and a half billion years ago. While relatively small in size compared to the planets, these small bodies have participated significantly in shaping the surfaces of all solid bodies in the solar system. The study of these objects is called meteoritics. A meteoroid denotes a solid body in interplanetary space before it reaches the Earth's atmosphere.
Most meteors result from meteoroids no more than a few centimeters in diameter.
A larger meteoroid which survives the fiery passage through the Earth's atmosphere as a meteor and strikes the Earth's surface is called a meteorite . Theodor Abrahamsen's photo at the right captures a Perseid meteor on August 12, 1986. Several countries have issued postage stamps about meteors and meteorites . Asteroids range in diameter from a meter up to 933 kilometers for the largest known asteroid, Ceres. Most asteroids orbit the sun in the main asteroid belt , a flat ring which lies between the orbits of the fourth planet Mars and the fifth planet Jupiter.