Mercury is the Solar System’s smallest planet, but its metallic core fills about 85 per cent of its radius, leaving a rocky shell so thin that cooling has crumpled the surface into cliffs hundreds of kilometres long

Mercury is the smallest planet in the Solar System, but most of the distance from its centre to its surface passes through metal. NASA puts the radius of Mercury’s metallic core at about 2,074 kilometres, compared with a planetary radius of 2,440 kilometres. That is roughly 85 per cent of the planet’s radius. The percentage [...] The post Mercury is the Solar System’s smallest planet, but its metallic core fills about 85 per cent of its radius, leaving a rocky shell so thin that cooling has crum