preearth

Preearth is a term occasionally used to denote the state or period preceding Earth's formation. It is not a standard term in scientific literature; more common descriptors include proto-Earth, the solar nebula, and early planetary accretion. When used, preearth generally refers to the material and processes that preceded the emergence of a distinct Earth-like planet in the inner solar system, roughly 4.5 billion years ago.

In planetary science, the preearth phase would encompass the protoplanetary disk and the growth of planetesimals from dust grains, as well as the chemical and physical evolution of early solar-system material that later accreted into Earth. Studies of meteorites and solar-system inclusions are often used to infer the properties of this pre-Earth material, providing clues about the composition of the early inner solar system before Earth's core and crust differentiated.

Outside technical usage, preearth appears occasionally in science fiction or world-building contexts as a proper noun, or as a label for an era or setting before Earth in a fictional timeline, and sometimes as an alternative to proto-Earth in speculative writing.

See also Proto-Earth; protoplanetary disk; planet formation; meteorite; early Earth.