Chaotian

A proposed name for the “pre-Earth” eon – i.e., “geologic time from the origin of the Solar System to the Moon-forming impact on Earth.”

In their scientific paper, “The Eons of Chaos and Hades” [PDF], C. Goldblatt, K.J. Zahnle, N.H. Sleep, and E.G. Nisbet wrote:

We propose the Chaotian Eon to demarcate geologic time from the origin of the Solar System to the Moon-forming impact on Earth. This separates the solar system wide processes of planet formation from the subsequent divergent evolution of the inner planets.

They continued:

Planetary formation begins with the separation of solids from gas in the solar nebula and is followed by a period of hierarchic growth culminating in massive collisions between proto-planets (Chambers, 2004). For the proto-planets which became the Earth and the Moon, the last major collision was an oblique impact between a Mars-size body and the Venus-size proto-Earth, which ejected mantle material to form the Moon and left the planet molten (Canup, 2004). This cataclysm was the true birth of Earth. It separates our proposed solar system wideChaotian Eon from the subsequent stratigraphic evolution of each inner planet. Naming this eon, we emphasise that composition of the inner planets and, thus, their geology results from the chaotic interaction of planetary embryos.

Splendidly, when devising the name for this eon the authors looked to the work of Hesiod (“Verily at the first Chaos came to be”) and Milton (“Chaos Umpire sits, And by decision more imbroiles the fray By which he Reigns”).

[Tip of the titfer to The Economist]