Dr. Patrick Cassen

December 20, 2006

“Thermal and Dynamical Evolution of the Primitive Solar Nebula”

NCC2-1250

The main objective of the proposed research is to understand the relationship between the properties of planetary materials and the evolution of the primitive solar nebula. This goal is pursued by means of theoretical models of the nebula designed specifically to illuminate the physical and chemical processes experienced by preplanetary material, particularly as inferred from the primitive meteorites. The models involve a synthesis of theoretical and observational results, and are tested against an array of solar system data. To the degree that they are consistent with inferences from both astronomical observations of young stellar objects and the known properties of planetary materials, they provide a comprehensive physical context for the discussion of nebular processes. Related, but secondary tasks would explore the consequences of variations in primary nebula parameters (such as total angular momentum) for the properties of other planetary systems; determine the conditions under which giant planets might be formed by direct (gravitational) condensation from a circumstellar disk; and constrain the timing of nebula removal by testing hypotheses for the existence of solar gases in the deep Earth. Thus the proposal contains four tasks, henceforth referred to as: 1) Models of the thermal evolution of the nebula and preplanetary material; 2) Initial conditions for planet formation in other systems; 3) Gravitational instabilities in circumstellar disks; and 4) Cooling of an early Earth embedded in nebula.