EVALUATION OF RADIATION EFFECTS IN SPACE 



Rainer Berger 



Lockheed-California Company, Biirbank, California 



In addition to such radiation effects in space as nuclear transformations, the 

 breakage of chemical bonds and other physical phenomena, the formation of 

 chemical compounds by radiation synthesis is of great importance. 



The aspects of the synthesis of more complicated organic compounds from 

 simple predecessors are primarily to be discussed in this paper, because they 

 offer clues to the evolution of organic compounds and to some degree to ques- 

 tions connected with studies on the origin of life. 



Figure 1 illustrates the overlapping successive evolutions which occurred 

 ever since the body of the Earth accreted. It is evident how the span of chem- 

 ical evolution interacts with that of organic evolution, the period in which 

 somewhere life began. 



Radiation reactions of the kind discussed here are believed to have occurred 

 on the primitive Earth. They proceeded in the past and still do on planets, 

 their satellites, comets, meteors, and even particles of the smallness of inter- 

 stellar grains. However, each type of reaction may not be applicable every- 

 where in space. 



One of the first experiments carried out in this area of research is the dis- 

 charge experiment of Miller.' Theories of Oparin- and also Urey^ held for 

 some time that the atmosphere of the primitive Earth was essentially com- 

 posed of methane, water, ammonia, and hydrogen. When these compounds 

 were subjected to an electrical discharge in the laboratory to simulate condi- 

 tions in nature during a thunderstorm or in the proximity of corona discharges, 

 a host of different biologically important compounds was detected in the reac- 

 tion mixture. A number of the resulting compounds are listed in table 1. 



The most interesting species are the synthesized amino acids, which as is 

 generally known are the building blocks of all proteins. It is significant that 

 none of the complicated amino acids such as tryptophane or serine are produced 

 in this way (figure 2). 



A number of similar confirming experiments were performed by Abelson'* 

 who used various mixtures of H2 , CHi , CO2 , NH3 , N2 , O2 and H2O. Heyns, 

 Walter, and Meyer'^ in addition to confirming Miller's work used also HoS in 

 their investigations and obtained ammonium thiocyanate, thiourea, and thio- 

 acetamide. Pavlovskaya and Passynsky® equally checked the discharge experi- 

 ments. 



Generally speaking, amino acids were obtained from reducing mixtures only 

 containing an excess of either H2 , CH4 , CO, or NH;j . No amino acids could 

 be obtained from an oxidative environment. The mechanism of amino acid 

 production follows essentially the path of a Strecker synthesis. First HCN 

 and aldehydes are obtained in the gas phase by the action of the electrical 

 discharge, then these compounds give amino nitrilcs in the aqueous phase. 

 Finally, hydrolysis leads to the amino acids. 



The experiments on the reaction mechanism show that special conditions of 



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