In the geologic record the Chaotianeon is unofficially proposed to denote the time preceding the solidification of the Earth's crust and the formation of Earth's moon. As proposed, it precedes the Hadean eon and is earliest eon in Earth's history as a planet.
The end of Chaotian was marked by the hypothetical collision of the proto-Earth and a planet-sized body named Theia, leading to the formation of the Moon.
This geological era designation was proposed by NASA scientists at the Ames Research Center in 2010 to formalize terminology in the earliest stages of Earth's history.
The NASA proposal divides the Chaotian into the Eochaotian and Neochaotian eras, which are in turn proposed to be divided into the Nephelean and Erebrean, and Hyperitian and Titanomachean periods, respectively.