When a comet approaches the sun, its heat causes the gas and ice to vaporize and form a bright tail. An asteroid is usually a small rocky body, about 10 to 1000 km in diameter. Most asteroids orbit the sun between Mars and Jupiter in an area called the asteroid belt. Most asteroids are made of silicate rocks and minerals with a little metal, but some are mostly metal. A meteorite is an ancient primitive rock, most of which come from asteroids.
Meteorites represent the building blocks of planets and, in some cases, life.
I think comets are very cool. Sue, age 12 Dear Sue, Comets are the oldest, most primitive bodies in the Solar System. They are remnants preserved from the earliest days of star and planetary formation. From what scientists know of their composition, comets may provide clues about the building blocks of life and of our Solar System. The impact of a large comet could cause major changes in the climate of a planet or a moon.