Experimental Studies in Metastable Crystallization

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Dr. Cassidy will use this award, made through the Small Grants for Exploratory Research program, to experimentally test the hypothesis that certain minerals found in meteorites could have grown metastably. Laboratory equipment and facilities for these studies are available at the Westinghouse Science and Technology Center in Pittsburgh. Diamonds and SiC grains have recently been identified in most classes of primitive stony meteorites. These materials probably condensed in the crystalline state from vapor. They may not have crystallized under equilibrium conditions, however. The possibility of metastable crystal growth has been raised by the discovery that crystalline diamond can be produced artificially in a plasma at very low pressures and moderate temperatures. Other high temperature minerals occur in primitive meteorites and, by analogy, these may also have grown metastably. Dr. Cassidy's research will explore the metastable growth of these minerals. If the research is successful, certain assumptions about the condensation theory of cosmic dust grains will have to be reexamined.