The primordial atmosphere of the primitive earth contained the following substances :
H2
Water vapour
NH3
CH4
Earth was formed approximately 4.5 billion years ago. As it cooled down, a primitive atmosphere was created by the outgassing of early volcanoes. The early atmosphere contained no oxygen and could not support most of the life forms. In addition to the molten lava flowing into the ocean, some of the chemicals viz., H2, CH4, NH3, CO2 and water vapourwere supposedly washed down by the rains into the ocean.