83 



ane, ammonia, and hydrogen. They favored a model for the atmo- 

 sphere provided from volcanic outgassing. It was dominated by 

 carbon dioxide, nitrogen, and water vapor; Abelson argued that 

 "volatiles from outgassing interacted with the alkaline crust to form 

 an ocean having a pH 8-9 and to produce an atmosphere consisting 

 of CO, C0 2 , N 2 , and H 2 ." A series of experiments were initiated in a 

 mildly reducing atmosphere. 



CO, N 2 , H 2 — Electric discharges acting on this mixture of gases 

 are not particularly effective in amino acid synthesis, but HCN is 

 produced in significant amounts. Glycine is produced in fair yield, 

 but only small amounts of higher amino acids are formed. However, 

 formaldehyde, which is important in the prebiotic synthesis of 

 sugars, is obtained in large amounts. 



C0 2 , N 2 , H 2 — The C0 2 is more oxidized than the CO, but the 

 excess H makes it a reduced mixture. As with CO + N 2 + H 2 , the 

 amino acid synthesis is quite low with electric discharges unless 

 H 2 /C0 2 ratio is >2. In this case glycine is produced in fair yield, 

 but again very few of the higher amino acids are formed. 



CO, H 2 — This mixture is used commercially in the Fischer- 

 Tropsch reaction to make hydrocarbons in high yields. The reaction 

 requires a catalyst, usually Fe or Ni supported on silica, a tempera- 

 ture of 200°-400°C, and a short contact time. Depending on the 

 conditions, aliphatic hydrocarbons, aromatic hydrocarbons, alcohols, 

 and acids can be produced. If NH 3 is added to the CO + H 2 , then 

 amino acids, purines, and pyrimidines can be formed. The interme- 

 diates in these reactions are not known, but it is likely that HCN is 

 involved together with others. 



CO, H 2 — Electric discharges are not effective with this mix- 

 ture, but UV light that is absorbed by the water (<1849 A) results in 

 the production of formaldehyde and other aldehydes, alcohols, and 

 acids. The yields are fair. The mechanism seems to involve splitting 

 the H 2 to H + OH with the OH converting the CO to C0 2 and the 

 H reducing another molecule of CO. 



The amount of hydrogen needed in the synthesis outlined 

 above, except in the CO, H 2 experiment, is still very high and it 

 does not fare well with present ideas about the atmosphere of the 

 early Earth. 



