Mercury is the smallest planet in the Solar System. It is also the closest planet to the Sun. Mercury’s orbit around the Sun takes about 87.97 Earth days. This is the shortest of all planets in the Solar System.
Mercury appears to have a solid silicate crust and mantle overlying a solid, iron sulfide outer core layer, a deeper liquid core later and a solid inner core.
Mercury is one of the four terrestrial planets in the Solar System, along with Venus, Earth and mars. Mercury is also a rocky body, like the Earth. It is the smallest planet in the Solar System, with an equatorial radius of 1,516 miles. Mercury is also smaller than the largest natural satellites in the Solar System: Ganymede and Titan. Mercury consists of approximately 70% metallic and 30% silicate material. Mercury’s density is the 2nd highest in the Solar System, behind the Earth.
Mercury’s density (5.427 g/cm3) can be used to infer details of its inner structure. Scientists believe that for Mercury to have such a high density, its core must be large and rich in iron.
Geologists estimate that the core of Mercury occupies about 55% of its volume. 2007 research suggests that Mercury has a molten core. Surrounding the core, is a 310-430 mile mantle consisting of silicates. Based on data from Mariner 10, and Earth-based observation, Mercury’s crust is estimated to be 22 miles thick. Mercury’s surface has numerous narrow ridges. They extend up several hundred kilometers in length. It is believed that these were formed as Mercury’s core and mantle cooled and contracted when the crust had already solidified.
Mercury’s core has a higher iron content than any other major planet in the Solar System. There have been several theories attempting to explain this.