Did a Complex Carbon Cycle Operate in the Inner Solar System?

Solids in the interstellar medium consist of an intimate mixture of silicate and carbonaceous grains. Because 99% of silicates in meteorites were reprocessed at high temperatures in the inner regions of the Solar Nebula, we propose that similar levels of heating of carbonaceous materials in the oxygen-rich Solar Nebula would have converted nearly all carbon in dust and grain coatings to CO. We discuss catalytic experiments on a variety of grain surfaces that not only produce gas phase species such as CH, CH, CH, CHOH, or CHCN, but also produce carbonaceous solids and fibers that would be much more readily incorporated into growing planetesimals.

Gas/solid carbon branching ratios in surface-mediated reactions and the incorporation of carbonaceous material into planetesimals.

We report the ratio of the initial carbon available as CO that forms gas-phase compounds compared to the fraction that deposits as a carbonaceous solid (the gas/solid branching ratio) as a function of time and temperature for iron, magnetite, and amorphous iron silicate smoke catalysts during surface-mediated reactions in an excess of hydrogen and in the presence of N. This fraction varies from more than 99% for an amorphous iron silicate smoke at 673 K to less than 40% for a magnetite catalyst at 873 K. The CO not converted into solids primarily forms methane, ethane, water, and CO, as well as a very wide range of organic molecules at very low concentration.

On the Use of Fourier Transform Infrared (FT-IR) Spectroscopy and Synthetic Calibration Spectra to Quantify Gas Concentrations in a Fischer-Tropsch Catalyst System.

One possible origin of prebiotic organic material is that these compounds were formed via Fischer-Tropsch-type (FTT) reactions of carbon monoxide and hydrogen on silicate and oxide grains in the warm, inner-solar nebula. To investigate this possibility, an experimental system has been built in which the catalytic efficiency of different grain-analog materials can be tested. During such runs, the gas phase above these grain analogs is sampled using Fourier transform infrared (FT-IR) spectroscopy.

The influence of buoyant convection on the nucleation of n-propanol in thermal diffusion cloud chambers.

A two-dimensional numerical model has been applied to three thermal diffusion cloud chamber (TDCC) investigations of n-propanol in helium taken by two different research groups to provide a quantitative example of how the results in these chambers can be affected by buoyant convection. In the first set of TDCC data, corrections for buoyancy resolve an apparent discontinuity in critical supersaturation data and also yield nucleation rate data that tend to agree better with higher rate, expansion-based studies at the same temperature. In the second TDCC study, the nucleation of propanol was studied over an extended pressure range.

Experimental studies of the vapor phase nucleation of refractory compounds. VI. The condensation of sodium.

In this paper we discuss the condensation of sodium vapor and the formation of a sodium aerosol as it occurs in a gas evaporation condensation chamber. A one-dimensional model describing the vapor transport to the vapor/aerosol interface was employed to determine the onset supersaturation, in which we assume the observed location of the interface is coincident with a nucleation rate maximum. We then present and discuss the resulting nucleation onset supersaturation data within the context of nucleation theory based on the liquid droplet model.