Mercury's internal structure. Cutaway computer artwork showing the different layers that make up the structure of the planet Mercury. Geologists estimate that Mercury's core (grey) 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 (orange) of silicates, 500-700 km thick, surrounding it. Mercury's crust (surface, brown) is believed to be 100-300 km thick based on data gathered from earth based observation, and the mariner 10 mission.