Hephaestian Type terrestrial planet. These are worlds that are highly active geologically due to their initial stages of formation. This is the stage in which the planetary crust first forms, and the planet becomes geologically differentiated. In their earliest stages, such planets may have a short-lived primary atmosphere, most of which will soon be lost due to Jeans escape, sputtering and/or impact.
Text by John M. Dollan in his Planet Classification List
Initially published on 24 October 2001.