four requirements must have existed for chemical evolution: 1.little or no O 2 – Earth’s early atmosphere was probably strongly reducing which would cause any free oxygen to react and form oxides and be removed from the atmosphere 2.a source of energy – early Earth was a place of high energy violent thunderstorms with torrential rainfall widespread volcanic activity bombardment from meteorites (caused cataclysmic changes in crust, ocean, and atmosphere) intense radiation (including UV radiation, since there was no ozone layer and younger suns emit more UV light)
