Earth Hadean temperature

The current models of the Sun suggest that its luminosity would have been some 20-30 per cent lower than its present value during the early part of the formation of the Earth. After the enormous temperatures of the Hadean period, the early precambrian may have been cooler, requiring prebiotic chemistry to occur below a layer of ice, perhaps heated by volcanic activity such as that found in geothermal vents. A layer of ice several hundreds of kilometres thick may have formed over the entire surface of the early Earth, providing protection from UV radiation and some global warming - conditions such as these may exist on the Jovian moon Europa. 

Agee, C.B., 1997. Melting temperatures of the Allende meteorite implications for a Hadean magma ocean. Phys. Earth Planet. Interior, 100, 41-7. 

Defining a representative composition for the ocean end-member in the models is particularly challenging because nearly every aspect of the physical and chemical state of the coupled ocean/atmosphere system on the early Earth (temperature, pH, elemental composition, salinity, oxidation state, etc.) is poorly understood at present and continues to generate vigoroits debate. We adopt an ocean composition that appears consistent with the cirrrently available corrstraints. The composition of the model late Hadean seawater nsed in this cormnitrrication is given in Table 1. 

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