ORIGIN OF FREE OXYGEN 61 



THE ASTRONOMER S VIEW 



Before finishing this chapter, we may well look into one other aspect 

 of the origin of life on earth, although it is not biological. This is the 

 astronomical viewpoint. A short review can, indeed, be added here, 

 because astronomers and biologists are very much in agreement 

 on this matter. Both in the complete volume on the Moscow Sym- 

 posium of the I.U.B., and in Florkin (1960), several papers on the 

 astronomical aspects have appeared. The main result is that at 

 present various cosmological theories exist, starting either from an 

 original 'hot earth' or from an original Void earth'. Both are, how- 

 ever, compatible with modern biological views on the origin of life 

 on earth through natural causes. This follows from the fact that, 

 astronomically speaking, the earth was well finished before the pos- 

 sibility arose for an origin of life. 



There is, however, one interesting point here, in relation to the 

 free oxygen of our atmosphere. According to astronomers, our earth 

 is too small, it lacks enough mass and consequently has not the re- 

 quisite force of gravity, to retain permanently free oxygen. A planet 

 like ours ought not to have any appreciable free oxygen in its atmos- 

 phere, because, even if it had been there originally, the escape rate 

 from the higher parts of the atmosphere into interstellar space is far 

 too high. Only through a process resembling, for example, the organic 

 assimilation of carbon dioxide, by which free oxygen is constantly 

 released into the atsmosphere, is an oxygenic atmosphere to be ex- 

 pected. Consequently, astronomers are agreeable to the supposition 

 that all free oxygen in our atmosphere at present is of biogenetic 

 origin, formed through assimilation in plants, by dissociation of 

 carbon dioxide. 



