Labels:book | bulletin board | reckoner OCR: Collecting these rocks by dredging the seafloor and then crushing them under vacuum in a sensitive mass spectrometer allow geochemists to determine the ratios of the isotopes in the mantle The results are quite surprising Calculations of the ratios indicate that between 80 and 85 percent of the atmosphere was out gassed in the first one million years; the rest was released slowly but constantly during the next 4.4 billion years The composition of this primitive atmosphere was most certainly dominated by carbon dioxide, with nitrogen as the second most abundant gas Trace amounts of methane ammonia sulfur dioxide and hydrochloric acid were also present but there was no oxygen Except for the presence of abundant water, the atmosphere was similar to that of Venus or Mars The details of the evo ...
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