Chemical Weathering Reactions on Venus
The experimental studies of chemical weathering reactions on Venus are currently focused on reactions responsible for removing SO2 from the atmosphere of Venus, releasing COS and H2S into the atmosphere of Venus, and for altering iron-bearing minerals such as magnetite, hematite, ilmenite, pyrite, and pyrrhotite. The rates of these reactions are being measured as a function of temperature, oxygen fugacity, and partial pressures of reactive gases by heating well characterized natural minerals and synthetic samples in controlled gas mixtures for known time periods (see figure). The solid reaction products are then examined by scanning electron microscopy, X-ray diffraction, and chemical analysis techniques to identify the new phases and to quantify their abundances. The kinetic data obtained are important for interpreting the results of the Magellan, Galileo Venus flyby, Pioneer Venus, Vega, and Venera spacecraft missions to Venus and the results of the Earth-based observations of the lower atmosphere below the clouds.
Basalt before and after experiment under Venus-like conditions.
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Gas-Grain Chemistry in the Solar Nebula
The experimental and theoretical studies of solar nebula chemistry are concerned with using chemical and mineralogical observations of primitive meteorites to constrain conditions (pressure, temperature, oxygen fugacity) in the solar nebula at the time when the meteorites and other solid matter were being formed and thermally processed. Both chemical and thermodynamic and chemical kinetic models are used to define these constraints. Recent work has focused on the rates at which gas-grain reactions, such as those responsible for forming troilite (FeS) and magnetite (Fe3O4), for making organic compounds, and for destroying interstellar grains took place in the solar nebula.
Iron sulfide crystals growing on iron metal (top view).
Cross section of a iron sulfide layer growing on top of iron metal.