138 



SIMPLER ORGANIC SUBSTANCES 



Table i 



Time and 

 Process Occurring 



Pliases and 

 Objects 



Chemical 

 Composition 



Temperature 



1 . Solar dust cloud. 



Gas 



Formation of Sun and Dust 

 disc of gas and dust. 



Hj, inert gases, CH^ 



Silicates, FeO, FeS, 

 little metallic iron, 

 solid H,0, NH3. 



<^o°C 



2. Preprotoplanet and 

 early protoplanet. 



Accumulation of 

 planetesimals and 

 substance of the 

 Moon. 



Gas 



Dust 



H2, inert gases, H^O, 

 NH„ CH,. 



Silicates, FeO, FeS. 



Planetesimals 



Silicates, FeO, FeS, 

 hydrated minerals, 

 NH.Cl, solid H,0 

 and NH,. 



o°C 



3. High-temperature 

 stage. Reduction of 

 iron oxides. Loss of 

 gases and volatilised 

 silicates. 



Gas 



Hj, inert gases, H,0, 

 N„ CH,, H,S, vola- 

 tilised silicates. 



Large planetesi-FeO, hydrated min- 

 mals erals, FeS, NH.Cl, 



some metallic iron. 

 C, Fe,C, TiN. 



Small planetesi- Silicates, metallic 

 mals iron, C, Fe^C, TiN, 



some FeS. 



2,ooo°C 



4. Second low-tem- 

 perature stage. Final 

 accumulation of the 

 Earth. 



Gas 



Mostly lost. Small 

 amounts of H^, 

 H3O, N„ CH,. 

 HjS, inert gases. 



Planetesimals Same as stage 3. 



o°C 



5. Final stage. Earth Moon 

 and Moon complete. 



Earth 



Atmosphere 



Silicates, a little metal- Space o°C 

 lie iron. 



45% metallic iron; 

 55% silicates. 



HjO, CH^, Hj, 

 N,^NH3. 



Earth < goo'C 

 going to 

 present 

 temperature 



(After Urey, IV. 60, p. 217.) 



