Analytical results for the material of the Chelyabinsk meteorite

This paper presents the results of the mineralogical, petrographic, elemental, and isotopic analysis of the Chelyabinsk meteorite and their geochemical interpretation. It was shown that the meteorite can be assigned to LL5-group ordinary chondrites and underwent moderate shock metamorphism (stage S4). The Chelyabinsk meteorite contains a significant fraction (approximately one-third by volume) of shock-melted material similar in composition to the main volume of the meteorite. The results of isotopic analysis suggest that the history of meteorite formation included an impact event approximately 290 Ma ago.     

Study of the planet-satellite system growth process as a result of the accumulation of dust cloud material

In our paper, we suggest a model allowing study of the growth process of the double system (planet-satellite) as a result of the accumulation of scattered material from the common dust condensation. The model consists of two components—a computer component and an analytic component. In the course of the numerical experiment, the computer model allows determination of the dependence of the ratio of particle number captured by each body on their mass ratio. From there, the obtained dependence is used to close the analytical model of the protoplanet growth that is reduced to the solving of a differential equation. It is shown that at any form of the dependence, the equation is integrated in quadratures, and its solution in a number of concrete cases is studied. As a result, possible scenarios of double-system growth are obtained.     

Advances in geochemistry during the last four decades: A personal perspective

This is the author’s speech at the meeting in Cologne (2007) to celebrate the 40th anniversary of the International Association of Geochemistry and Cosmochemistry, which the author served as the President in 2000 to 2004. The paper narrates the author’s personal involvement in important scientific programs during the last 4 decades, including implementation of isotope techniques, oil-and-gas research, diamond research, deep-sea drilling, space research, molecular biology and the origin of life.     

Traveling self-sustained structures in interstellar clouds with the isentropic instability

The isentropic thermal instability of media with a generalized heat-loss function and negative bulk viscosity condition are discussed. We obtain the nonlinear equation taking into account the nonlinear saturation of the isentropic instability. This equation describes the nonstationary evolution of acoustical waves in media with the isentropic instability. Its stationary solutions are investigated analytically. The most interesting solution is the self-sustained pulse. Using the numerical simulation of the nonlinear acoustical equation and the full system of one-dimensional non-stationary hydrodynamical equations, we showed the disintegration of the initial weak perturbation of compression into sequence of these self-sustained pulses in low-density PDRs.     

Phenomenon of life: Between equilibrium and non-linearity. Origin and principles of evolution

Geochemistry International -     

Experimental modeling of the origin of the Moon’s metallic core at partial melting

Geochemical criteria of the Moon’s composition as deficient in Fe and depleted in volatile components and the distribution of siderophile elements in the planet offer the possibility of correlating, under certain conditions, the origin of the Moon and its core from an initial material of composition close to CI carbonaceous chondrites. In order to verify the model of the percolation of liquid metallic Fe through a silicate matrix of chondritic composition at low degrees of melting, we have experimentally modeled Fe movement and deposition in the course of high-temperature centrifugation. The starting experimental mixture had the composition 85% Ol, 10% ferropicrite, and 5% Fe-S (95% Fe and 5% S); the experimental conditions were 4000 g “gravity”, T = 1440°C, Δ log fO₂(IW) ～ ?5.5. In our experiments, Fe was segregated in systems with Fe sulfide and silicate melts at partial melting under reduced conditions and the deformation of the silicate framework. Our results indicate that the Moon could be produced from a material of composition close to CI carbonaceous chondrite.     

Chemical composition of the primary aqueous phase of the earth and origin of life

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).     

Estimation of the composition of the Earth’s primary aqueous phase. 2. Synthesis from the mantle and igneous rock material. Comparison with synthesis from the carbonaceous chondrite material

Simulation results of the equilibrium state of systems water-carbonaceous chondrite material, water-primary mantle material, water-ultramafic rock material, and water-mafic rock material open with respect to carbon dioxide and methane at 25°C, 1 bar indicate that highly alkaline reduced aqueous solutions with K/Na > 1 can be formed only if water is in equilibrium with compositions close to those of continental crust and primitive mantle. Yu.V. Natochin’s hypothesis that the living cell can be formed only in an aqueous environment with K/Na > 1 leads to the conclusion that terrestrial life could arise and further evolve on the Earth during the differentiation of primary chondritic material into the Earth’s core and mantle (during the first few million years of the planet’s lifetime) in an alkaline (pH 9–10) reduced (Eh = −400–500 mV) aqueous solution at a temperature of 50–60°C, in equilibrium with an N₂-bearing atmosphere, which also contained CH₄ (partial pressure from 10⁻² to 10⁻⁸ bar), CO₂ (partial pressure from 10⁻⁵ to 10⁻⁸ bar), NH₃, H₂, H₂S, CO, and other gases.