530 



Annals New York Academy of Sciences 



distribution was made abiotically by Miller-Urey type reactions in the solar 

 nebula. Such reactions are known to produce carbon chains of varying length, 

 presumably by free radical reactions. The hydrocarbons in comets and the 

 organic material in cosmic dust (Parkin et al., 1%2) may have been produced 

 in this way. Meinschein (1961) has argued that such reactions would be 

 highly nonselective, showing little preference among the billions of possible 



I.OOOr 



100- 



X 



o 

 <v 



a. 



10- 



15 



20 

 Carbon Number 



25 



Figure 9. Mass spectrum of meteoritic hydrocarbons and 2 Ijiogenic reference materials 

 (Nagy el al., 1961). The observed peak heights in the C„Ho„+.. series are probably due, 

 mainly, to parent ions of saturated hydrocarbons, although fragment ions of other substances 

 also contribute. The difference between the original Orgueil distillate and the chemically 

 separated, saturated hydrocarbon fraction indicates that large amounts of other substances 

 were present in the distillate. 



isomers. But it is essential not to equate the concepts "abiotic" and "non- 

 selective." Industrial chemical syntheses, from polyethylene to medicinals, 

 are highly selective, favoring one or a few products over the multitude of others. 

 Even Miller-Urey type reactions can be quite selective, as shown by Wilson 

 (1960). He obtained products mainly in the mass ranges Ci to C5 and C20 

 and up. Although the product distribution in that particular experiment 

 (and in the industrial Fischer-Tropsch synthesis of hydrocarbons) may not be 

 an accurate match of the Orgueil hydrocarbon distribution, one must remember 

 that only an intinitesimal fraction of the possible combinations of conditions 



