How did heating and melting separate metal cores from rocky mantles inside asteroids?

When asteroids undergo sufficient heating, their interiors can melt, triggering geochemical processes that lead to differentiation. This process allows denser materials to separate from less-dense ones within the body.1

Specifically, when temperatures become high enough, metallic iron separates from the surrounding silicate material. Because the metallic iron is significantly denser, it sinks toward the center of the asteroid, eventually forming a distinct metallic core. This process simultaneously forces less-dense, molten material—such as basaltic lavas—toward the surface.21

The primary heat sources responsible for this internal melting are believed to be the decay of short-lived radioactive isotopes, such as aluminum-26 and iron-60. Other potential contributors to this thermal energy include heat generated by electric currents induced by early solar activity and the release of gravitational potential energy during the initial formation of the asteroids. While some asteroids remained primitive, those that experienced this differentiation provide the source material for iron meteorites, which are thought to be fragments of these metallic cores.321