Life Sciences in the Space Program 



much simpler processes. At some fundamental level, interactions between 

 nucleotides and amino acids leading to the formation of peptide bonds were 

 essential, and these interactions are likely to have originated during prebiological 

 evolution. Theoretical and experimental evidence should continue to be sought for 

 specific interactions that can be related to codonic or anti-codonic relationships 

 and to the ability of nucleotides to catalyze the synthesis of peptide bonds. 



Findings for Prebiological Evolution 



• Knowledge of the conditions on the early Earth is essential for the 

 development of physical-chemical models for the origin of metabolic and 

 generic systems. Major uncertainties persist, however, because a geological rec- 

 ord is lacking. 



• Mars continues to be the prime target in the search for evidence of 

 prebiological evolution and fossil extraterrestrial life in the solar system. 



• Much progress has been made on the synthesis of prebiological monomers and 

 oligomers based on methane-rich planetary atmospheres, but little has been 

 done to assess the possible origins of organic compounds in carbon-dioxide- 

 rich surface environments. The development of model chemical systems capable 

 of metabolic function in either type of environment has been largely unex- 

 plored. 



• As candidates for the first self-replicating systems capable of both metabolic and 

 genetic function, the potentiality of RNA-like molecules has been heightened by 

 the discovery that RNA has catalytic properties, while the alternative of clay 

 minerals has received relatively little experimental emphasis. 



Recommendations 



• Research programs in the Life Sciences and Solar System Exploration 

 Divisions of OSSA should direct theoretical studies of planetary phenomena, 

 such as accretionary impacts and the origin and evolution of the atmosphere, 

 oceans, tectonic regimes, and climate, toward determining the range of 

 physical and chemical conditions that may have evolved during the first 

 billion years of Earth history in the near-surface regions of the oceans and 

 the atmosphere and the hydrothermal environments on land and under the 

 sea. 



• The Life Sciences and Solar System Exploration Divisions of OSSA should 

 pursue vigorous programs of remote observations, ground-based research, 

 and exploration of extraterrestrial bodies — Mars, Venus, the Moon, the 

 primitive asteroids and comets, and the satellites of the Giant Planets, 

 especially Titan — with emphasis on acquisition and study of samples 

 returned from Mars, to fill the gap in Earth's geologic record and to 

 determine the limitations on prebiological evolution elsewhere in the solar 

 system. 



• The Exobiology Program should continue on a broad front to support 

 research on the prebiological evolution of functional complexity leading 





