Mercury (planet) 2015. The "BepiColombo" spacecraft will arrive at Mercury in 2025. Mercury appears to have a solid silicate crust and mantle overlying a solid, iron sulfide outer core layer, a deeper liquid core layer, and possibly a solid inner core. Mercury is one of four terrestrial planets in the Solar System, and is a rocky body like Earth. It is the smallest planet in the Solar System, with an equatorial radius of . Mercury is also smaller—albeit more massive—than the largest natural satellites in the Solar System, Ganymede and Titan. Mercury consists of approximately 70% metallic and 30% silicate material. Mercury's
Extraterrestrial liquid water the existence of a sub-ice ocean is inferred from the measurements of the magnetic field of Jupiter. Since conductors moving through a magnetic field produce a counter-electromotive field, the presence of the water below the surface was deduced from the change in magnetic field as the moon passed from the northern to southern magnetic hemisphere of Jupiter. Thomas Gold has posited that many Solar System bodies could potentially hold groundwater below the surface. It is thought that liquid water may exist in the Martian subsurface. Research suggests that in the past there was liquid water flowing on the surface, creating