Michael F. A'Hearn
University of Maryland
Deep Impact: Excavating Comet Tempel 1
Deep Impact delivered 19 Gigajoules of kinetic energy to the nucleus of comet Tempel 1. The excavation process was observed both in situ and remotely in order to understand the physical and chemical properties of the nucleus. Key physical conclusions include very low strength (65 Pa) at all scales down to the microscopic, very low bulk density for the nucleus implying very high porosity, and surface geology that is very different from that of other cometary nuclei with several features that are not yet understood. Chemical results include the fact that late stage ejecta were not thermally processed (water came out as ice, not vapor), a very large increase in the release of organics relative to water with a smaller increase in CO2, and emission bands of several species that are not yet identified.