Types of asteroids

Most asteroids can be classified into one of three groups: C-type, S-type and M-type.

More than three quarters of known asteroids belong to the carbonaceous (carbon-rich) C-group. Very dark and mostly made of carbon, C-group asteroids are thought to be the most ancient, reflecting the very materials that existed when the Solar System formed. They mostly live in the outer regions of the main asteroid belt. 

Next, around a fifth of known asteroids are siliceous (or stony) S-group, composed of silicate rocks, including metal-bearing minerals. Many S-group asteroids shine fairly bright, and they are mostly found in the inner regions of the main asteroid belt. 

Most of the rest can be categorised into the M-group. Their composition is highly diverse. Some of them are expected to be rocky, whilst others are thought to consist of metals like nickel and iron. This latter type could be fragments of larger bodies that once had liquid cores, before they were shattered in collisions long ago. M-group asteroids can vary from very dark to very bright.

Discover more about asteroids here.