SESSION I. DISCUSSION 113 



A. I. Lebedinskiï (U.S.S.R.): 



The successful solution of the problem of the origin of Ufe on the Earth may be made 

 far easier by a study of the conditions under which Hfe exists on Mars. 



The hypothesis that Ufe exists on Mars rests quite firmly on the fact that we can observe 

 seasonal changes in the colouring of the various parts of the planet which we call seas 

 and canals. 



The form in which life exists on Mars is undoubtedly very different from that of life 

 on the Earth and is probably essentially anaerobic as there is no appreciable amount of 

 free oxygen on Mars. A marked shortage of water must also be considered as a definite 

 pecuharity of the Martian biosphere. 



Both the Earth and Mars were undoubtedly formed by the gradual acquisition, over a 

 long period, of cold bodies falling on their surfaces. 



The possibihty of the so-called 'hot' origin of the planets is open to the most crushing 

 criticism but this, of course, falls outside the scope of such a short communication. In 

 the course of the 'cold' formation of planets, both the Earth and Mars were made up of 

 particles from which all gaseous components had been given off by prolonged vacuum 

 distillation at temperatures close to o ° C. Water and gaseous products could be given off 

 from such particles when they had fallen on to the Earth either by heating them strongly 

 or under the action of high pressure. 



This giving off of water and gases could occur, in part, owing to the effect of meteoritic 

 bodies faUing on the surface of the planet; but it probably took place, for the most part, 

 under the influence of high pressure in the interior with a gradual migration to the surface 

 of the Earth of water and gases, along with the products of volcanic eruptions. 



All these cosmogenic considerations lead to a belief in a great similarity in composition 

 between the eruptive products on the Earth and those on Mars. Probably the conditions 

 for dissipation of the atmosphere were also very similar on both planets, for the rate of 

 dissipation is determined by the temperature of the superficial layers of the ionosphere 

 which are in radiative equilibrivun with the ultraviolet radiations of the sun responsible 

 for ionizing them. 



We may, therefore, postulate the presence, on the surface of Mars, of enough water 



to fill the oceans to the same depth as those of the Earth or, at least, to half that depth. 



The differences between the atmosphere and oceans of the Earth and those of Mars 



must have been mainly caused by the different climate and different results of the activity 



of the biosphere. 



In the cold Martian climate the mean temperature of the soil at all latitudes is below 



G ° C and therefore water can exist there only in the solid phase, in the form of under- 



grotmd deposits of ice and everlastingly frozen soils, in which the ice carmot be observed. 



What can be observed is a small amount of water on the polar caps and this is the 



water which takes part in the seasonal cycle. 



The biosphere which has developed on Mars dviring the short hours of diurnal thawing 

 must have evolved far more slowly than that on the Earth and has probably not yet 

 succeeded in creating an oxygen-rich atmosphere. 



It is even more surprising that on Mars we find practically the same partial density 

 of carbon dioxide as on the Earth. It is hard to explain this coincidence in any other way 

 than by the activity of the biosphere. 



The impermeabiUty of the contemporary Martian atmosphere to ultraviolet rays is 

 due not to absorption by oxygen, as on the Earth, but to absorption by carbon dioxide. 

 Thus the limit of the wavelength of light which can pass through is about 1900 A and, 

 surprisingly, this corresponds with the short-wave limit of the band of mitogenic rays. 

 The idea suggests itself that the abihty of organisms to reflect and absorb mitogenic rays 

 is a relic from the time when there was neither oxygen nor ozone in the atmosphere of 

 the Earth. 



I. S. Shklovskiï (U.S.S.R.): 



I cannot agree with the point of view of Academician V. G. Fesenkov that the mass 

 of the primaeval Earth was far greater than the mass of the Earth today because it was 

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