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The current theory of the earth is the oxygen in our atmosphere came from life....If we subtracted out the oxygen; before life, the air pressure would be lower.
Quote from: puppypowerThe current theory of the earth is the oxygen in our atmosphere came from life....If we subtracted out the oxygen; before life, the air pressure would be lower.This does not follow.Life did not just create oxygen out of nothing, and add it to the atmosphere.It is thought that the early atmosphere had a high level of carbon dioxide CO2 (like Venus). Through photosynthesis, living algae & plants converted atmospheric carbon dioxide CO2 into oxygen O2, using the carbon for building their own biomass. This process does not increase the pressure of the atmosphere - in fact, iron minerals would have reacted with the atmospheric oxygen, taking it out of atmospheric circulation, and resulting in a net reduction of atmospheric pressure (not an increase, as suggested).See: http://en.wikipedia.org/wiki/Great_Oxygenation_Event
The experiment used water (H2O), methane (CH4), ammonia (NH3), and hydrogen (H2). The chemicals were all sealed inside a sterile 5-liter glass flask connected to a 500 ml flask half-full of liquid water. The liquid water in the smaller flask was heated to induce evaporation, and the water vapour was allowed to enter the larger flask. Continuous electrical sparks were fired between the electrodes to simulate lightning in the water vapor and gaseous mixture, and then the simulated atmosphere was cooled again so that the water condensed and trickled into a U-shaped trap at the bottom of the apparatus.
Professor Jeffrey Bada, himself Miller's student, inherited the original equipment from the experiment when Miller died in 2007. Based on sealed vials from the original experiment, scientists have been able to show that although successful, Miller was never able to find out, with the equipment available to him, the full extent of the experiment's success. Later researchers have been able to isolate even more different amino acids, 25 altogether. Professor Bada has estimated that more accurate measurements could easily bring out 30 or 40 more amino acids in very low concentrations, but the researchers have since discontinued the testing. Miller's experiment was therefore a remarkable success at synthesizing complex organic molecules from simpler chemicals, considering that all life uses just 20 different amino acids.
Originally it was thought that the primitive secondary atmosphere contained mostly ammonia and methane. However, it is likely that most of the atmospheric carbon was CO2 with perhaps some CO and the nitrogen mostly N2. In practice gas mixtures containing CO, CO2, N2, etc. give much the same products as those containing CH4 and NH3 so long as there is no O2. The hydrogen atoms come mostly from water vapor. In fact, in order to generate aromatic amino acids under primitive earth conditions it is necessary to use less hydrogen-rich gaseous mixtures. Most of the natural amino acids, hydroxyacids, purines, pyrimidines, and sugars have been made in variants of the Miller experiment.