What type of atmosphere was present on early Earth ?

Oparin of Russia and Haldane of England proposed that the first form of life could have come from pre-existing non-living organic molecules (e.g. RNA, protein, etc.) and that formation of life was preceded by chemical evolution, i.e., formation of diverse organic molecules from inorganic constituents. The conditions on earth were – high temperature, volcanic storms, reducing atmosphere containing CH₄ , NH₃ , etc.In 1953, S.L. Miller, an American scientist created similar conditions on a laboratory scale. He created electric discharge in a closed flask containing CH₄, H₂, NH₃ and water vapour at 8000C. He observed formation of amino acids. In similar experiments others observed, formation of sugars, nitrogen bases, pigment and fats. Analysis of meteorite content also revealed similar compounds indicating that similar processes are occurring elsewhere in space. With this limited evidence, the first part of the conjectured story, i.e., chemical evolution was more or less accepted. S.L. Miller created conditions similar to early Earth’s atmosphere, including electric discharge, in a laboratory experiment.