The Earth's inner core is primarily made up of an iron-nickel alloy. It consists mostly of iron (about 80%) with nickel making up about 5-15%, along with small amounts of lighter elements such as sulfur, oxygen, silicon, or other unidentified lighter elements. The inner core is solid due to the extremely high pressure despite its very high temperature, comparable to the surface of the Sun. It is believed to contain iron in a crystalline form known as ε-iron with a hexagonal close-packed structure, which can incorporate small amounts of nickel and other elements. In summary, the main materials composing the inner core are:
- Iron (major component)
- Nickel (secondary component)
- Small percentages of lighter elements such as sulfur, oxygen, and silicon
These conclusions come from seismic studies, laboratory experiments, and analysis of the chemistry of Earth's materials and meteorites, as direct sampling is not possible.
