The planet had cooled down from its original molten state, developing a solid crust and oceans created from water vapor in ... that appeared in the Precambrian era. Photograph by Joel Sartore ...

Hadean Era (4,550-3,850 mya) The Precambrian's oldest era ... producing enough energy and heat to vaporize any water or melt any rock that may be present. Gravity also helps separate heavy ...