Planetary differentiation

Planetary differentiation is the process by which a rocky or icy body separates into layers of distinct composition and density shortly after formation. As a newborn planet or large moon accumulates heat from radioactive decay and gravitational compression, denser materials (primarily iron and other metals) sink toward the center, while lighter silicates and volatiles rise outward. This creates a layered structure: a metallic core, rocky mantle, and thin crust.

The process was crucial in shaping terrestrial worlds. Earth's differentiation, occurring within the first 50 million years, produced its iron core and established the conditions for plate tectonics, magnetism, and life-supporting chemistry. Smaller bodies like asteroids either differentiated partially or not at all, depending on their size and heating history—a key reason meteorites tell us so much about the solar system's infancy.

Differentiation fundamentally altered planetary evolution: it concentrated heat-producing elements, powered long-lived geological activity, and influenced the composition available for atmospheres and surfaces. Modern understanding relies on seismology, meteorite analysis, and computer modeling of heat flow and material behavior.

Related

Core (geology), Crust (geology), Moon, Asteroid, Meteorite, Solar system formation