Diamonds in the products of the 2012–2013 Tolbachik eruption (Kamchatka) and mechanism of their formation

The origin of diamonds in the lava and ash of the recent Tolbachik eruption of 2012–2013 (Kamchatka) is enigmatic. The mineralogy of the host rocks provides no evidence for the existence of the high pressure that is necessary for diamond formation. The analysis of carbon isotope systematics showed a similarity between the diamonds and dispersed carbon from the Tolbachik lava, which could serve as a primary material for diamond synthesis. There are grounds to believe that the formation of Tolbachik diamonds was related to fluid dynamics. Based on the obtained results, it was suggested that Tolbachik microdiamonds were formed as a result of cavitation during the rapid movement of volcanic fluid. The possibility of cavitation-induced diamond formation was previously theoretically substantiated by us and confirmed experimentally. During cavitation, ultrahigh pressure is generated locally (in collapsing bubbles), while the external pressure is not critical for diamond synthesis. The conditions of the occurrence of cavitation are rather common in geologic processes. Therefore, microdiamonds of such an origin may be much more abundant in nature than was supposed previously.     

Planned earth-based studies of the phobos material

The article describes scientific challenges in the analysis of the Phobos material that is to be returned in the Russian Phobos-Grunt space mission. Their close connection with current problems in studies of the Earth and the origin of life has been demonstrated. The most obvious up-to-date studies that are to be carried out under laboratory conditions after the soil sample is delivered to Earth are specified, and the required equipment listed.     

Role of low solar luminosity in the history of the biosphere

It was shown that the history of the biosphere is closely related to processes caused by low solar luminosity. Solar radiation is insufficient to maintain the Earth’s surface temperature above the freezing point of water. Positive temperatures are kept owing to the presence of greenhouse gases in the atmosphere: CO₂, CH₄, and others. Certain stages in the development of the biosphere and climate are related to these effects. Methane was the main carbon-bearing gas in the primordial atmosphere. It compensated the low solar luminosity. Life originated under the reduced conditions of the early Earth. Methane-producing biota was formed. Methane remained to be the main greenhouse gas in the Archean. The release of molecular oxygen into the atmosphere 2.4 Ga ago resulted in the disruption of the established mechanism of the compensation of the low solar luminosity. Methane ceased to cause a significant greenhouse effect, and the content of carbon dioxide was insufficient to play this role. A global glaciation began and had lasted for approximately 200 million years. However, the increasing CO₂ content in the atmosphere reached eventually a level sufficient for the compensation for the low solar luminosity. The glaciation period came to an end. Simultaneously, a conflict arose between the role of CO₂ as a gas controlling the thermal regime of the planet and as an initial material for biota production. As long as the resource of biotic carbon was inferior to that of atmospheric CO₂, the uptake of atmospheric CO₂ related to sporadic increases in biologic production was insufficient for a significant change in the thermal regime. This was the reason for a long-term climate stabilization for 1.5 billion years. By 0.8 Ga, the resource of oceanic biota reached the level at which variations in the uptake of atmospheric CO₂ related to variations in the production of organic and carbonate carbon became comparable with the resource of atmospheric CO₂. Since then, an oscillatory equilibrium has been established between the intensity of biota development and climate-controlling CO₂ content in the atmosphere. Glaciation and warming periods have alternated. These changes were triggered by various geologic events: intensification or attenuation of volcanism; growth, breakup, or migration of continents; large-scale magmatism; etc. A new relation between atmospheric CO₂ and biotic carbon was established in response to the emergence of terrestrial biota and the appearance of massive buffers of organic carbon on land. The interrelation of the biosphere and climate changed.     

Study of the organic matter in the rocks of the crystalline basement and weathering mantle of Tatarstan

This paper is dedicated to study of the rocks of crystalline basement and weathering mantle taken from several parametric boreholes at the territory of Tatarstan Republic. Optical-microscopy in combination with methods of organic geochemistry, including isotope analysis, revealed a migration nature of the organic matter of the studied rocks from oil-source beds of the Devonian domanikoid-facies deposits.     

Reconstruction of composition of the earth’s primary aqueous phase. Part 1: Formation from carbonaceous chondrite matter

The equilibrium composition was modeled for the water-carbonaceous chondrite matter system open to CO₂ and CH₄. It was shown that at 25°C, total pressure of 1 bar, and definite proportions between partial pressures of CO₂ (10⁻⁵–10⁻⁸ bars) and CH₄ (10⁻⁴–10⁻⁸ bar), the aqueous phase is characterized by a K/Na ratio of 4–12, which corresponds to the ratios of these elements in the cellular liquid of organisms. Aqueous phase has pH = 8−9, Eh = −450 ± 50 mV, and ammonia nitrogen, and K, Na, and Mg concentrations close to those in the cellular liquid.     

Luna-Glob project in the context of the past and present lunar exploration in Russia

The Russian Luna-Glob project has been conceived with a view to understand the origin of the Earth-Moon system. The objectives and main features of the Luna-Glob mission, which will mainly study the internal structure of the Moon by seismic instruments, are described in the context of the past and current program of lunar exploration in Russia.