120 HISTORY OF THE OCEANS 



Astronomical studies of the surface of the stars, interstellar gaseous 

 dust, atmospheres of other planets, meteorites, and comets prove 

 the necessity for the formation of the first hydrocarbons during the 

 formative stages of our planet and its subsequent evolution. The 

 question is merely which of many possible ways was this accom- 

 plished. 



It is now generally accepted in astronomy that the earth, as 

 well as the other planets of the solar system, arose from gigantic 

 nebulae of gas and dust which once surrounded the sun. Study of 

 the chemical composition of this gaseous dust shows the presence 

 of methane and perhaps more complex hydrocarbons. However, 

 with careful physicochemical analyses of phenomena occurring 

 during the formation of planets, Urey showed that when the clouds 

 of gas and dust particles became aggregated into protoplanets and 

 planets, a considerable amount of methane and other volatile gases 

 must have disappeared from the vicinity of the earth to the region 

 of large planets where they may be found today. According to 

 Urey, graphite and carbides were the chief forms of carbon in the 

 emergent earth. From these, hydrocarbons must have been 

 synthesized abiogenetically during the formation of the earth's 

 crust, particularly at the time when carbides could react with 

 hydrated rocks in the deeper layers of the earth's crust. However, 

 although the formation of the earth's crust began early in the 

 development of our planet, it cannot be considered complete even 

 now. Hence, even today we may expect to find processes for the 

 formation of simple hydrocarbons in the deeper layers of the 

 lithosphere, where reducing conditions prevail and where all traces 

 of life are lacking. 



Many geological observations seem to justify this supposition. 

 The processes for the abiogenetic synthesis of hydrocarbons is now 

 taking place, although on a very limited scale. Hydrocarbons in 

 the basement rocks are isolated from living organisms or any 

 products of their decomposition. Here, in granite fissures, such 

 gases as methane, ethane, propane, and small amounts of liquid 

 hydrocarbons occur. These could have arisen only abiogenetically. 



Because these hydrocarbon deposits are usually of no com- 

 mercial value, geologists have given them little attention. Never- 



