576 Annals New York Academy of Sciences 



too small in number to have supplied more than a trace of the meteoritic 

 hydrocarbons. 



Analytical data provide additional evidence against significant contamina- 

 tion of the Orgueil and Murray fragments. Benzpyrenes are common pyrolysis 

 products. The air in urban areas contains from 1.5 to 25.5 parts per trillion 

 by weight of benzpyrenes.^^ Pyrolysis products of wood include methyl 

 alcohol, ketones, organic acids, Cg and smaller alkanes, as well as olefinic 

 hydrocarbons. Colored markings usually contain pigments that absorb 

 sharply in the visual range. Wax pencils are frequently composed of wax- 

 esters or petroleum waxes. Drying oils in paints and lacquers are mixtures of 

 olefinic compounds which have carbonyl functional groups. Crude oil dis- 

 tillates and polishing oils have limited boiling point ranges and contain chiefly 

 C20 and smaller compounds. The aromatic fractions in petroleum are more 

 complex than the aromatics in recent sediments or the meteorites.^* ■^^•''^•^^ 



Analyses of the Murray and Orgueil extracts show that they contain: 

 (1) negligible concentrations of olefins (and in the Orgueil extract of benz- 

 pyrenes); (2) no substances which absorb sharply in the visual region; (3) 

 alkane and aromatic hydrocarbons which are distributed as they are in ter- 

 restrial marine sediments; (4) hydrocarbons and benzene extractable nonhy- 

 drocarbons in the same relative abundances that they are found in sedimental 

 extracts. Because the Murray contains about 5 times and the Orgueil more 

 than 50 times the amount of benzene extractable materials that is found in an 

 average sediment, it is unlikely that these extracts could have been obtained 

 from terrestrial sediments which are the only previously reported sources of 

 extracts of these compositions. The low recent organism counts'^ '^^ make it 

 improbable that terrestrial organisms were a source of the extracts. Qualita- 

 tive and quantitative considerations support the view that the Murray and 

 Orgueil carbonaceous extracts were predominantly indigenous. 



Nonbiological Sources of Hydrocarbons 



Anders^' suggests that hydrocarbons resembling those in terrestrial organ- 

 isms may have been made abiotically in the solar nebula and incorporated 

 later in the bodies of the solar system. When life evolved on Earth, he believes 

 that these hydrocarbons favored the evolution and survival of organisms which 

 could utilize and synthesize hydrocarbons of the types which are now present 

 in most solar bodies.^^ Innumerable other speculative sources of hydro- 

 carbons may be proposed. Many of these proposals are neither clearly 

 supported nor directly denied by experimental data. 



Although the extensive literature on organic reactions define what many 

 reactants will form under various conditions, our imaginations may specify 

 reactants and conditions that are either untried or unobtainable on Earth. 

 Nevertheless, organic chemistry is, in part, a record of the means that have 

 been devised by intensive study and extensive research to synthesize biotic 

 type products. This record clearly attests that it is extremely difficult by the 

 use of abiotic reactions to duplicate most of the individual biological com- 

 pounds that have carbon numbers in the range covered by the compounds in 

 the benzene extracts of carbonaceous chondrites. After failing to synthesize 

 a pristane reference, Bendoraitis et al.,^* isolated this hydrocarbon, which is a 



