ASTEROID TYPES

The differences between four main categories of these space rocks explained

253 Mathilde C-type Carbonaceous

They’re so dark due to their carbonblack surfaces that even the largest require a telescope to detect. They consist mostly of clay and silicate rocks and account for more than

75 per cent of all asteroids. Most of these ancient space rocks orbit in the outermost regions of the asteroid belt.

433 Eros S-type Stony

This class of asteroids orbit the inner asteroid belt and are primarily composed of stony materials, metallic nickel-iron as well as iron and magnesium silicates. S-types are the second most common asteroids and are also among the brightest – some larger examples, such as 7 Iris, can be spotted with binoculars.

21 Lutetia M-type Metallic

M-types are pure metal, or mixtures of metal and small amounts of stone, and have originated from the cores of planetary bodies that have been broken apart by impacts. Most are metallic, comprising largely of nickeliron, and they are found in the middle region of the asteroid belt.

4 Vesta V-type Vestoid

V-types have similar surface properties to 4 Vesta, one of the largest asteroids in the

Solar System. They’re not so different in composition to S-type, also made from stony iron and chondrites, but they contain higher levels of silicon-aluminium oxides called pyroxenes. They are a reddish colour.