Primitive atmosphere composition

The atmospheric composition of Jupiter is much different from tlx --< of Mars and Venus. It is similar to the primitive stellar atmospheres. I In... 

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

The Earth and planetary system were formed 4.6 billion years ago. Certain meteorites as fragments from small planets have preserved a primitive cosmic composition and contain records of the early history of the solar system. Because of the lack of an atmosphere, the lunar surface has not been reworked and still exhibits the craters from the impact of large planetesimals which were abundant in space at the stage of planet formation. The oldest rocks on earth have an age of 3.5 to 4 billion years. 

It has been pointed out that the total amounts of carbon and nitrogen now present on the surface of the Earth, if dissolved in the present oceans, would produce a rather dilute solution (see for example Miller and Orgel, 1974). If all of the carbon were to be converted to formaldehyde, or all of the nitrogen to HCN, the maximum concentrations attainable would be about IM and 0.2M, respectively. Of course, it is extremely improbable that concentrations approaching these could ever have existed. It is clear that when the likely composition of the primitive atmosphere is taken into con-... 

We call the present atmosphere of the earth secondary , but the discussion is still open whether there was a primordial atmosphere and what the composition of the primary one was. The so-called primitive (or primordial) atmosphere could have been formed by the remaining gas phase (solar wind) from solar nebula (H2, He). However, it is unlikely that the earth had such a primitive atmosphere. There are several assumptions (e. g. the collision of earth with another celestial body, by which... 

If the primeval Earth s atmosphere was indeed formed only from volatile components emitted by the primitive, newly formed Earth s crust, its composition must have depended on the time at which it was formed, i.e., whether this was before or after the formation of the iron-rich Earth s core (Joyce, 1989) ... 

Now they see things very differently. The chemical composition of the air is not a precondition for life but the result of it. Around two billion years ago, primitive living organisms transformed the atmosphere from one largely devoid of oxygen to one with plenty... 

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. 

In addition to the transition phenomena mentioned so far in the present section, a variety of even larger scale processes might have operated during chemical evolution, namely, instabilities and bifurcations in the very atmospheric environment within which life emerged. As shown in the paper by Marcel Nicolet, the earth s atmosphere is the theater of a variety of complex chemical and transport phenomena. Moreover, as explained by Stanley L. Miller, the composition of the primordial atmosphere has certainly affected deeply the chemistry in the primitive oceans. Conversely, once life emerged the properties of the atmosphere changed radically, and this must have affected the further course of evolution. We refer to Prather et al.41 and North et al.42 for an account of present views on large scale transitions in the earth-atmosphere system. 

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