Primitive atmosphere oxygen

Table 17.1 shows that Earths present-day atmosphere is a mixture of gases— primarily nitrogen and oxygen, with small amounts of argon, carbon dioxide, and water vapor and traces of other elements and compounds. This has not always been the composition of the atmosphere. Oxygen, for example, was nor a component until the evolution of photosynthesis in primitive life-forms 3 billion years ago. Carbon dioxide levels have also varied significantly over time. 

There was no free oxygen or nitrogen in the primitive atmosphere. How and why did the composition of air change ... 

Walker, J. C. G., 1978 Oxygen and hydrogen in the primitive atmosphere. Pure and Appl. Geophvs. 116,222-231. 

The prebiotic, primitive atmosphere was practically devoid of oxygen, since it is not a constituent of volcanic gases. How oxygen came to arise and attain its present level is a fascinating problem that will be discussed below. 

Note that this reaction is the reverse of Eq. (6). Unlike oxygen, CO2 is a relatively unreactive gas that is found in the atmospheres of planets other than the earth. It may have been part of the earth s primitive atmosphere and... 

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