Density and composition

Mercury is thought to be one of the densest planets in the solar system. This high density suggests that Mercury is dominated by an iron core, which makes up 70 per cent of the planet by mass. During 2007, a team of astronomers announced that they had evidence suggesting that some of the core is molten. The discovery was made by bouncing radio waves off the planet and analysing the return signals.

A thin layer or mantle surrounds the core, which is mainly silica rock (30%). Little is known about Mercury's crust, but it is thought to extend down less than 100 kilometres. The crust seems to have cooled rapidly once formed, and is solid enough to preserve surface features.

Mercury is about one-third the size of Earth and has a little more than one-third the gravity of Earth. A 75 kg person on Earth has a weight of 735 N, but on Mercury the same person would weigh 247 N.

Orbital plane -

4880 km

Thin crust

Mantle

Thick core

Orbital plane -

4880 km

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