Assuming that there was liquid water present, the oceans of the early Earth likely covered almost the entire surface due to the lack of continent formation in the Hadean. The composition of this global ocean is difficult to predict, but it likely contained both inorganic and organic species. Prebiotic organic material in the ocean was likely comprised primarily of small, monomeric molecules in relatively dilute concentrations (the so-called “prebiotic soup”) although local pockets of increased molecular complexity and concentration would have existed. The majority of the inorganic species were probably ionic species from salts, with total concentrations thought to be higher than that of today, perhaps roughly 1.5 to 2 times higher. The composition of the ions present in the early ocean is a matter of debate, however. ( Sodium ) Na+ is generally agreed to have been an important species in the early oceans. Many assume that NaCl was the major salt as it is now, but some have suggested that, rather than chloride, bicarbonate may have been the predominant counterion. Adding to the uncertainty, the pH of the early oceans is not well constrained, with estimates ranging from a pH of 4 to 9. While very little can be said about the likely conditions of the early ocean with much certainty, the presence of a global ocean would have provided a large, bulk aqueous medium in which prebiotic chemistry could occur.
The early Sun’s lower luminosity but relatively larger output of UV radiation coupled with the lack of UV screening by the Earth’s atmosphere ensured that the early Earth’s surface was bathed in significantly more high-energy
light relative to today. This in conjunction with the variety of auspicious environments (aqueous, interfacial, and gaseous) present on the early Earth would have allowed for a wide-variety of photochemical processes to occur.