Illustration showing the core, mantle and crust of Mercury. Geologists estimate that Mercury's core occupies about 42% of its volume; in comparison, for Earth this proportion is 17%. Recent research suggests that Mercury has a molten core with a mantle of silicates, 500-700 km thick, surrounding it. Mercury's crust is believed to be 100-300 km thick based on data gathered from earth based observation, and the mariner 10 mission.