Asteroids are classified as small metallic, rocky bodies that orbit around the sun. They do not have atmospheres and are too small to be called planets. The main collection of asteroids in our solar system is in the aptly named asteroid belt. This belt is found between Mars and Jupiter and contains millions of asteroids. Asteroids range from the very large (1000km diameter) to the size of pebbles. Giuseppe Piazzi is credited with discovering the first asteroid when he discovered the dwarf planet he named Ceres in 1801. The composition of the asteroids was not known until much later and even today it is not well understood.
What are asteroids made of?
Generally speaking there are 3 main types of asteroids; C-type, S-type, and M-type. These names relate directly to the general composition of an asteroid. C-Type asteroids are the most common type of asteroid and are rich in carbon. They are said to be comprised of the same substances as the sun (without the volatile gases). The second most common asteroid is the S-type, which have a stony and metallic iron composition. M-type asteroids are comprised largely of metallic iron with smaller amounts of other metals like nickel, palladium, iridium, gold, platinum and other precious metals. A rare type of asteroid called the V-type is not common in the asteroid belt, but these are comprised of basalt.
Interestingly, the different types of asteroids take a different place in the asteroid belt. C-type asteroids are found in large concentrations in the outer belt. M-type are found in the middle region, while S-type asteroids are mainly in the inner asteroid belt.