The Formation of the Earth 53 



The presence of such abiogenic, cosmic methane, though perhaps only in the 

 distant past, perhaps in the first stages of the emission of gases from the interior 

 of the Earth, may be inferred from its presence on the other planets, in meteorites 

 and from what are now known to be the essential features of the process of 

 formation of the Earth. From the fact that methane is present in eruptive 

 formations it also follows that abiogenic methane must, up till now, have been 

 given off from the interior to a greater or lesser extent. 



It is hard to estimate the overall quantity of hydrocarbons and abiogenic 

 organic compounds in general which was present in the whole volume of the 

 Earth in the past and the quantity it now contains. It is, however, clear, from 

 the evidence adduced already, that this quantity may be very large. This circum- 

 stance is one of the incentives to a search for ways in which petroleum could 

 have been formed abiogenically. The main stimulus to such a search is the fact 

 that analysis of geological data concerning the conditions under which petroleum 

 has been laid down and concerning the distribution of natural gases in the Earth 

 suggests that petroleums are of purely abiogenic origin [40, 41]. 



The ironic way in which Hoyle [30] referred to the organic theory of the 

 formation of petroleum and the absence from his book of serious discussion of 

 the possibility of its inorganic origin evoked a protest from Link, the president 

 of the American Association of Petroleum Geologists [42]. That there is a serious 

 basis for working out a non-organic theory of the formation of petroleum is 

 evident from, for example, the fact that that eminent specialist on the question 

 of the formation of petroleum. Prof. V. D. Porfir'ev has changed his earlier 

 opinion and now embraces the non-organic theory [43]. At the same time we 

 must draw attention to the perfectly correct appeal by Link for a reconciliation 

 between the views of representatives of related scientific disciplines. 



As Mueller pointed out, even before the formation of meteorites, that is to 

 say, in the very earliest stages of the evolution of the dust-gas cloud, hydro- 

 carbons could polymerize, forming the hydrocarbon compounds wliich are 

 present now in the carbonaceous chondrites. Thus, it was not only methane, 

 but also these more complicated compounds which entered into the composition 

 of the Earth from the very beginning. Such of these compotmds as are not 

 now present in the interior of the Earth probably broke down long ago into 

 simpler ones owing to the high temperatures which now prevail there. How- 

 ever, such of them as managed to move outwards towards the surface while the 

 temperature was still moderate could have undergone further complication and 

 polymerization during their journey towards the surface. 



Finally, when they emerged on to the surface of the Earth they were exposed 

 to new possibilities. According to Siiss, the photodissociation of methane in the 

 presence of water vapour indicates a possible mode of synthesis of the most 

 diverse organic substances. Evaluation of these comphcated questions of organic 

 chemistry is outside the sphere of competence of astronomers and geophysicists. 

 Chemists must play the main part here. 



Nevertheless, the evidence of contemporary astronomy and geophysics leads 

 to two conclusions which seem to me important for the problem of the origin 

 of fife. In the first place, organic compounds of varying degrees of complexity 



