Dark C (carbonaceous) asteroids, which make up most asteroids and are in the outer belt, are C-type (chondrite) asteroids are most common, making up about 75 percent of known asteroids. They are very dark in appearance and probably consist of clay and silicate rocks. They are among the most ancient objects in the solar system. Their composition is thought to be similar to the sun, but depleted in hydrogen, helium, and other volatiles. C-type asteroids mainly are in the asteroid belt's outer regions.
Bright S (silicaceous) asteroids and are in the inner belt, closer to Mars. S-types (stony) are made up of silicate materials and nickel-iron, and accounts for about 17 percent of known asteroids. They are brighter than C-type and they dominate the inner asteroid belt.
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Bright M (metallic) asteroids, M-types (metallic) are made from nickel and iron and accounts for about 8 percent of known asteroids. They are brighter than C-type and they can be found in the asteroid belt's middle region.
