Atmospheric composition of Hadean–early Archean Earth: The importance of CO

The mantle was probably oxidized early, during and shortly after accretion, and so the early atmosphere of Earth was likely dominated by CO2 and N2, not by CH4 and NH3. CO2 declined from multibar levels during the early Hadean to perhaps a few tenths of a bar by the mid- to late Archean. Published geochemical constraints on Archean CO2 concentrations from paleosols are highly uncertain, and those from banded iron formations are probably invalid. Thus, CO2 could have been sufficiently abundant during the Archean to have provided most of the greenhouse...