What is Planetary core?
The '''planetary core''' is the innermost layer or layers in a [[planet]]. The [[terrestrial planet]]s (planets with a rocky surface) have a core mainly made of [[iron]] and could be a [[solid]] or a [[liquid]] layer. The [[Earth's core]] is partially liquid, while the cores of [[Mars (planet)|Mars]] and [[Venus (planet)|Venus]] are thought to be completely solid, because the cores do not make a [[magnetic field]]. The [[gas giants]] also have a core made of iron. Their cores are very small, in [[:wikt:simple:proportion|proportion]] to their large size. However, the gas giants are so large that their cores can still be larger than the Earth's core. [[Jupiter (planet)|Jupiter]]'s core is estimated to be 12 times the mass of the Earth's. A core's size can vary from each planet or other object. The [[moon]]'s core is 20% of its [[radius]], but [[Mercury (planet)|Mercury]]'s core is 75% of its radius. [[Category:Geology]] [[Category:Planets]]