14 HAROLD C. UREY 



ported glacial drift toward the equator. Since much of the surface was covered 

 with ice, carbon dioxide could not have reacted with the surface rocks and must 

 have remained in the atmosphere. Hence, high concentrations of carbon dioxide 

 would have reached the high atmosphere and the escape of atomic oxygen must 

 have been very rapid. When most of the water was lost, the carbon dioxide could 

 have reacted with the rocks and disappeared and the present situation with httle 

 water and carbon dioxide would have developed. 



The evidence in regard to the development of the Martian atmosphere does 

 not preclude the existence of life on the planet providing oxygen in large amounts 

 has escaped from the planet. It is Ukely that this is the case. The general chemical 

 development should have been similar to that occurring on the Earth during 



its early history. 



CONCLUSION 



It is probable that the three planets, Venus, Earth and Mars, all originated 



with substantial amounts of water on their surfaces. The estimated temperatures 



are such as not to be prohibitive for the evolution and maintenance of Ufe. 



This paper is a brief summary of certain parts of a much more detailed survey 

 of the problem of atmospheres which will appear in the Handbuch der Physik, 

 where detailed arguments for many points mentioned will be given and where 

 more detailed references will appear. 



REFERENCES 



1. J. B. S. Haldane, The Origin of Life. Rationalist Annual, 1929. 



2. A. I. Oparin, The Origin of Life. Macmillan, New York, 1938. 



3. N. W. PiRiE, New Biol, 16, 41, 1954. 



4. J. D. Bernal, The Physical Basis of Life. Routledge & Kegan Paul, London, 195 1. 



5. S. Arrhenius, Ann. Nat.-{u.Kultur)phil., 9, 22, 1910. 



6. J. H. J. Poole, Sci. Proc. R. Dublin Soc, 22, 345, 1941. 



7. 8. H. C. Urey, Chapter in Physics and Chemistry of the Earth, Vol. 2. Pergamon 



Press, London, 1956. 

 9. H. C. Urey, The Planets. Yale Univ. Press, 1952. 



10. H. C. Urey, Handbuch der Physik. In the press. 



11. H. G. Thode, J. MacNamara & W. H. Fleming, Geochim. et cosmoch. Acta, 3, 



2355 1953- 



12. A. MacGregor, S. Afr.J. Sci., 24, 155, 1927. 



13. G. Herzberg, Atmospheres of the Earth and Planets (Ed. by G. P. Kuiper). Univ. 



of Chicago Press, 1949. 



14. N. A. Kozyrev, Publ. Crimean astrophys. Obs., 12, 169, 1954. 



15. E. Pettit & S. B. Nicholson, Publ. astr. Soc. Pacif, 67, 293, 1955. 



16. A. Adel, Astrophys. J., 93> 397^ I94i- 



17. J. W. Chamberlain & G. P. Kuiper, Astrophys. J., 124, 399, 1956. 



18. C. H. Mayer, R. M. Stoanaker & T. P. McCollough. As reported in Sky & 



Telesc, 15, 435, 1956. 



19. A. Danjon, Astronomic, 57, 161, 1943. 



20. A. DOLLFUS, Mem. Soc. Sci. Liege, 4^ serie, 18, 141, 1956. 



21. F. H. Whipple & D. H. Menzel, Publ. astr. Soc. Pacif, 67, 161, 1955. 



22. B. Lyot, Ann. Obs. Paris (Meudon), 8, 1929. 



23. G. P. Kuiper, Atmospheres of the Earth and Planets (Ed. by G. P. Kuiper). Univ. 



of Chicago Press, 2nd ed., 1952. 



24. J. Grandjean & R. M. Goody, Astrophys. J., 121, 548, 1955. 



25. A. DoLLFUS, C. R. Acad. Sci., Paris, 233, 467, 1066, 1951. 



26. T. Dunham, Atmospheres of the Earth and Planets (Ed. by G. P. Kuiper). Univ. of 



Chicago Press, 1949. 



