Primitive Earths Atmosphere

The wavelengths at which most of the components of a primitive Earth atmosphere absorb lie, with few exceptions, under 200 nm. The exceptions include ammonia (< 230 nm), hydrogen sulphide (<260 nm) and ozone (180-300 nm). However, ozone was probably present in the primeval atmosphere only in trace amounts, since free oxygen was only available in extremely low concentrations. The young Earth thus had no protective ozone layer, so short-wavelength UV irradiation could readily penetrate the atmosphere. 

Cloud PE (1968) Atmospheric and hydrospheric evolution on the primitive Earth. Science 160 729-736... 

The energy from the decay of radioactive elements was probably not an important energy source for the synthesis of organic compounds on the primitive earth since most of the ionization would have taken place in silicate rocks rather than in the reducing atmosphere. The shock wave energy from the impact of meteorites on the earth s atmosphere and sur-... 

This synthesis of amino acids, called the Strecker synthesis, requires the presence of NH4+ (and NH3) in the primitive ocean. On the basis of the experimental equilibrium and rate constants it can be shown16 that equal amounts of amino and hydroxy acids are obtained when the NH4+ concentration is about 0.01 M at pH 8 and 25°C with this NH4+ concentration being insensitive to temperature and pH. This translates into a pNH3 in the atmosphere of 2 x 1(U7 atm at 0° and 4 x 10-6 atm at 25°C. This is a low partial pressure, but it would seem to be necessary for amino acid synthesis. Ammonia is decomposed by ultraviolet light, but mechanisms for resynthesis are available. The details of the ammonia balance on the primitive earth remain to be worked out. 

A mixture of CH4, N2, and traces of NH3 and H20 is a more realistic atmosphere for the primitive earth because large amounts of NH3 would... 

For these reasons, it is generally felt that the interstellar molecules played at most a minor role in the origin of life. However, the presence of so many molecules of prebiotic importance in interstellar space, combined with the fact that their synthesis must differ from that on the primitive earth where the conditions were very different, indicates that some molecules are particularly easily synthesized when radicals and ions recombine. Another way of saying this is that there appears to be a universal organic chemistry, which shows up in interstellar space, in the atmospheres of the major planets, and in the reducing atmosphere of the primitive earth. 

Miller SL. The atmosphere of the primitive earth and the prebiotic synthesis of amino acids. Orig Life 1974 3 139. 

Very little is certain on organic matter formation in the atmosphere or in the ocean of the primitive Earth as a result of lightning, volcanism, or other energy sources. Since no preserved geological records exist from the concerned era, there is no certainty about the reactor conditions (physical parameters kind, concentration and/or fluxes of reagents). The endogenous synthesis of... 

But what was there, in addition to water, on the primitive Earth The four outer planets of the solar system (Jupiter, Saturn, Uranus and Neptune) are still made up mainly of hydrogen, helium, methane, ammonia and water, and it is likely that those same chemicals were abundant everywhere else in the solar system, and therefore even in its four inner planets (Mercury, Venus, Earth and Mars). These were too small to trap light chemicals, such as hydrogen and helium, but the Earth had a large enough mass to keep all the others. It is likely therefore that the Earth s first atmosphere had great amounts of methane (CH4), ammonia (NHJ and water, and was, as a result, heavy and reducing, like Jupiter s. 

Even if the atmosphere of the primitive Earth could change within ample limits, therefore, we are bound to conclude that the first oceans became filled with organic molecules. In addition to molecular syntheses there also were, of course, degradation processes going on,... 

The primitive earth atmosphere was composed of CO2, CO, nitrogen, and water, and somehow radiation, heat, and sparks contributed to the generation of amino acid from these basic materials (Kobayashi et al, 2002 Miyakawa et al., 2002). If this is true, it should be possible to experimentally prove this we are not aware whether this has been done. However, if it is true, nothing could be physiologically more important than CO, nitrogen, and H2O. 

Eons ago. The atmosphere of the primitive Earth before the emergence of life contained N2, NH3, H2, HCN, CO, and H2O. Which of these compounds is the most likely precursor of most of the atoms in adenine Why ... 

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