A mostly solid layer of Earth lying beneath the crust and above the core; consisting mostly of iron, magnesium, silicon, and oxygen. On other planets and moons, the mantle is the layer between the crust and core. Mantles contain information about a planet's total composition, a key parameter in understanding planet formation and how the planets vary in composition with distance from the Sun. A second definition of mantle is a smooth blanket of surface material (generally fine-grained, sometimes layered) that was deposited by some process such as wind or water and that now obscures the underlying land.