Chemical composition of the primary aqueous phase of the earth and origin of life |
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| Authors: | E M Galimov Yu V Natochin B N Ryzhenko E V Cherkasova |
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| Institution: | 1. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, ul. Kosygina 19, Moscow, 119991, Russia
2. Sechenov Institute of Evolutionary Physiology and Biochemistry, pr. Toreza, 44, St. Petersburg, 194223, Russia
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| Abstract: | Prokaryotes and cytoplasm of eukaryotes are dominated by K+, whereas the extracellular fluid of most species of multicellular organisms is dominated by Na+. It was substantiated that the K+/Na+ ratio in the salt constituent of the cells of modern organisms qualitatively reflects the proportions between these elements in the aqueous phase, in which the first forms of life and the protocell originated. The same conclusion is done by Armen Y. Mulkidjanian et al. (PNAS 13, 2012, E821-830). The chemical composition of primary aqueous phase of the Earth was reconstructed using thermodynamic numerical simulation of the equilibrium composition of the ??carbonaceous chondrite material-water??, ??primitive mantle material-water??, ??ultramafic rock-water??, ??mafic rocks-water?? systems that are open with respect to CO2 and CH4. It was shown that at 25°C, total pressure of 1 bar, and partial pressures of CO2 and CH4 10?5?C10?8 and 10?2?C10?8 bar, respectively, the aqueous phase of the systems with carbonaceous chondrite and primitive mantle has K+/Na+ > 1, which corresponds to the proportions of these elements in the intracellular solution. The aqueous phase is characterized by pH = 8?C9, Eh = ?450 ± 50 mV, the presence of ammonium nitrogen, and concentrations of K, Na, and Mg close to those in the inferred intracellular fluid. The interaction of water with ultramafic and mafic rocks provides K+/Na+ < 1 in aqueous solution, which corresponds to the chemical composition of the modern natural waters of the Earth??s crust. Simulation results show that the protocell could arise in the primary aqueous phase of the Earth during differentiation of chondritic material into the Earth??s core and mantle, after the formation of the nitrogen atmosphere containing CH4, CO2, NH3, H2, H2S, CO and other gases, but prior to the formation of the modern rocks of the Earth??s crust (first billion years of the planet??s lifetime). |
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