115 



These research areas overlap the research interests of scientists 

 in the solar-energy conversion field who are actively exploring metal 

 surfaces and minerals which, in the presence of light, will photolyze 

 water and reduce carbon dioxide and nitrogen. Therefore collabora- 

 tion in this area should be encouraged between prebiotic chemists 

 and scientists attempting to capture solar energy by chemical means. 



Recent studies suggest clays, mineral surfaces, and metal ions 

 had important roles in activating organic molecules for reaction, and 

 stabilizing polymers by binding them to surfaces and then catalyzing 

 condensation reactions. The oxidation state of the metal ion used is 

 critically important and it should be compatible with the expected 

 oxidation level of the metal ion in the presence of the reducing 

 environment of the primitive Earth. Further research on catalysis and 

 absorption by inorganic substances may help explain why only a 

 limited group of organic molecules were included in living systems. 



Many compounds with UV and visible chromophores are 

 produced in experiments which simulate chemical transformations 

 on the primitive Earth. In only a few instances the role of UV light in 

 the further transformation of these compounds has been investi- 

 gated. Since light in the UV-visible range was one of the most potent 

 energy sources impinging on the primitive Earth, this area of research 

 merits more extensive investigation. Of particular importance is the 

 possibility of utilizing the light energy to drive reactions that would 

 normally be energetically unfavorable, such as peptide or nucleotide 

 bond formation. 



It was recently observed that the sulfate in sea water is reduced 

 to sulfide when it comes in contact with molten portions of the 

 Earth's crust at the Galapagos Rift. This sulfide is emitted as H 2 S or 

 metal sulfides from these thermal vents. The ease of reduction of 

 sulfate suggests that most of the sulfur on the primitive Earth was in 

 the sulfide oxidation state. The role of sulfide ion and insoluble 

 metal sulfides in chemical evolution deserves more detailed investiga- 

 tion. The pronounced (nucleophilic) reactivity of the sulfide ion 

 could result in a marked change in the reaction pathways observed in 

 its absence. 



A case for a role of HCN in chemical evolution has been estab- 

 lished by previous research. Purines, pyrimidines, and amino acids 

 have been synthesized from HCN. Further analysis of the mono- 

 melic building blocks formed from HCN merits investigation. This 



