Energy yields for hydrogen cyanide and formaldehyde syntheses: The hcn and amino acid concentrations in the primitive ocean

Abstract

Prebiotic electric discharge and ultraviolet light experiments are usually reported in terms of carbon yields and involve a large input of energy to maximize yields. Experiments using lower energy inputs are more realistic prebiotic models and give energy yields which can be used to estimate the relative importance of the different energy sources on the primitive earth. Simulated prebiotic atmospheres containing either CH₄, CO or CO₂ with N₂, H₂O and variable amounts of H₂ were subjected to the spark from a high frequency Tesla coil. The energy yields for the synthesis of HCN and H₂CO were estimated. CH₄ mixtures give the highest yields of HCN while H₂CO is most efficiently produced with the CO mixtures. These results are a model for atmospheric corona discharges, which are more abundant than lightning and different in character. Preliminary experiments using artificial lightning are also reported. The energy yields from these experiments combined with the corona discharge available on the earth, allows a yearly production rate to be estimated. These are compared with other experiments and model calculations. From these production rates of HCN (e.g. 100 nmoles cm⁻² yr⁻¹) and the experimental hydrolysis rates, the steady state concentration in the primitive ocean can be calculated (e.g., 4 × 10⁻⁶ M at pH 8 and 0°). A steady state amino acid concentration of 3 × 10⁻⁴ M is estimated from the HCN production rate and the rate of decomposition of the amino acids by passage through the submarine vents.