Laboratory analogues to cosmic dust

A pulsed laser has been used to vaporize olivine, pyroxene, nickel-iron alloy, Al2O3 carbon calcium carbonate, and silicon carbide, as well as mixtures of immiscible phases (Au-Al2O3 and Au-olivine) in oxidizing, reducing, and inert atmospheres. The collected condensates usually consist of strings of grains which have a median diameter of 20-30 nm, which is comparable to the calculated sizes of some interstellar and circumstellar dust grains. The silicate minerals vaporized in O2 as well as calcium carbonate and carbon vaporized in Ar or H2, are collected as glassy grains while the other materials produced crystalline grains. The systems of immiscible phases when vaporized produced condensates consisting of intermixed 2-50 nm grains of both components. The type of size distribution, crystal structures, and qualitative elemental analyses of the condensates are given. Possible similarities between the mechanism of grain growth, structure, morphology, and chemistry of laboratory grains compared to interstellar and circumstellar grains, phases in meteorites and extraterrestrial dust collected in the stratosphere are examined. Applications of the experimental technique include the production of grain systems to serve as laboratory analogues for spectral studies of grain materials believed to exist in astronomical environments, and studies of the structure of grains condensed from complex gas mixtures. (Auth.)