Environments for chemical evolution on the primitive Earth

It has been pointed out that the total amounts of carbon and nitrogen now present on the surface of the Earth, if dissolved in the present oceans, would produce a rather dilute solution (see for example Miller and Orgel, 1974). If all of the carbon were to be converted to formaldehyde, or all of the nitrogen to HCN, the maximum concentrations attainable would be about IM and 0.2M, respectively. Of course, it is extremely improbable that concentrations approaching these could ever have existed. It is clear that when the likely composition of the primitive atmosphere is taken into con- 

Free formaldehyde could only accumulate over areas where relatively little HCN was being produced. This suggests a seasonal variation, or perhaps even an oceanic environment. Although the concentration problem for formaldehyde is less severe than for HCN, there would still be a formidable problem. Stratification of the primitive ocean would have reduced the effects of dilution by making only the upper 100—200 m readily accessible to the atmosphere (compare Weyl, 1968). A global ocean as suggested by Hargraves (1976) as a consequence of the early formation of a thin sialic crust, would 

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