THE ORIGIN AND EVOLUTION OF THE EARTH'S ATMOSPHERE AND HYDROSPHERE.

摘要

The origin and evolution of the earth's atmosphere has been a much studied subject ever since the early nineteen hundreds. This problem has been investigated from various perspectives, such as geological, biological and physical.; Because of the uncertainty regarding the processes which led to the formation of life, the biological studies have been forced to include certain fundamental assumptions. These assumptions are presented in the discussion section.; The physical studies, on the other hand, have made fewer assumptions and have led to a greater understanding of the origin of the atmosphere. These studies have suggested that the processes by which the earth was formed were different from that of the other planets. One consequence of this difference is that the earth may have lost its primary atmosphere fairly early in it's history. Consequently, the present atmosphere is the result of outgassing from the interior of the earth. It has also been shown that the outgassing occurred over all geological time, not just in a short period.; The composition of the outgassed fluid has been a point of serious debate. In this work, a model developed by Melton and Giardini (1983) has been used. In this model, the fluid inclusions in diamonds have been taken as original samples of the outgassed fluids. The model uses first order kinetics of the degassing processes of H(,2), CH(,4), N(,2), CO and Ar, and zero order kinetics for the degassing processes of H(,2)O and CO(,2).; In this work, samples with compositions similar to the fluid included in diamonds were exposed to electric discharge, UV radiation and gamma radiation to formulate the equilibrium composition of the earth's atmosphere. The change of the composition was slight after the samples were exposed to the various high energy sources. Therefore, I postulate that the composition in the inclusion was very close to the equilibrium condition and use these values, with slight corrections, to tabulate the earth's early atmosphere.; Small amounts of organic and inorganic compounds were formed in the samples by the radiation. These are a possible source of fundamental materials necessary for the formation of living systems.; The Melton/Giardini model was used to calculate the composition and pressure of primitive atmosphere of the earth as a function of time, beginning 4.5 b.y. ago. Since light gases such as H(,2) and He escape from the earth, and other degassed material undergoes numerous chemical and physical reactions, the earth's atmosphere was quite different from the predicted composition using the uncorrected Melton/Giardini model.