99 research outputs found
Cosmochemical Derivation of the Composition of Chondrite Material.
第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月17日(木) 国立国語研究所 2階講
Ordinary Chondrites and the Origin of the Earth
第3回極域科学シンポジウム/第35回南極隕石シンポジウム 11月29日(木)、30日(金) 国立国語研究所 2階講
Ideas and perspectives: Development of nascent autotrophic carbon fixation systems in various redox conditions of the fluid degassing on early Earth
The origin and development of the primary autotrophic metabolism on
early Earth were influenced by the two main regimes of degassing of the
Earth – reducing (predominance CH4) and oxidative (CO2). Among
the existing theories of the autotrophic origin of life in hydrothermal
environments, CO2 is usually considered to be the carbon source for nascent
autotrophic metabolism. However, the ancestral carbon used in metabolism may
have been derived from CH4 if the outflow of magma fluid to the surface
of the Earth consisted mainly of methane. In such an environment, the
primary autotrophic metabolic systems had to be methanotrophic. Due to the
absence of molecular oxygen in the Archean conditions, this metabolism would
have been anaerobic; i.e., oxidation of methane must be realized by
inorganic high-potential electron acceptors. In light of the primacy and
prevalence of CH4-dependent metabolism in hydrothermal systems of the
ancient Earth, we propose a model of carbon fixation where the methane is
fixed or transformed in a sequence of reactions in an autocatalytic
methane–fumarate cycle. Nitrogen oxides are thermodynamically the most favorable
among possible oxidants of methane; however, even the activity of oxygen
created by mineral buffers of iron in hydrothermal conditions is sufficient
for methanotrophic acetogenesis. The hydrothermal system model is considered
in the form of a phase diagram, which demonstrates the area of redox and P
and T conditions favorable for the development of the primary methanotrophic
metabolism.</p
Basalt-kahusite lava splitting in the paleoproterozoic Pechenga Depression in Kola Peninsula
Geochemical properties of oils in different regions and potential source metals contained in oil
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