62 



ETERNITY OF LIFE 



lOOKm. I ROCKET 

 I 



from samples of frozen subsoil obtained from a depth of two 



to seven metres. This implies growth after 1,000 to 3,000 



years of refrigeration. L. Kriss" studied the frozen subsoil 



of Kolyuchin and Wrangel 



Islands and made some very 



cautious inferences. Although 



he too found viable micro- 

 cocci at these levels he con- 

 sidered it perfectly possible 



that these had fallen there 



from the upper levels where 



they were also present. 

 Thus the problem of the 



possibility of micro-organisms 



being preserved in a viable 



state at low temperatures for 



thousands of years cannot be 



considered to be conclusively 



solved. Nevertheless, one 



cannot reach the opposite 



conclusion that bacteria and 



their spores would necessarily 



be destroyed at temperatures 



near to absolute zero. 



It seems, however, that the greatest menace to bacteria 

 and their spores in outer space is not so much the cold as 

 the radiations which pass through it. Even at the end of 

 last century it was established that by no means all the 

 radiations of which sunlight is composed reach the surface 

 of the Earth. Part of the light is absorbed by the atmosphere. 

 This absorption affects particularly the ultraviolet radiations 

 which are invisible to the eye but are very active chemically. 

 Only radiations having a wavelength of not less than 3,000 A 

 reach the surface of the Earth. It is only by going up high 

 mountains that one can establish the presence of ultraviolet 

 light with a wavelength of 2,900 A. All the short-wave radia- 

 tion is absorbed by the atmosphere and does not reach the 

 surface of the Earth. However, outside the atmosphere, inter- 

 planetary and interstellar space are penetrated by radiations 

 having wavelengths of 1,000-2,000 A. These radiations are 



Fig. 2. 



Diagram of levels of the 

 atmosphere. 



