Dr. Steven Charnley

December 20, 2006

“Theoretical Astrochemistry: Interstellar Clouds, Protostellar Disks, Comets & Meteorites”

NCC 2–1412

The goal of the proposed theoretical work is to understand the transit and synthesis of organic interstellar matter from molecular clouds, into protostellar disks, and thereafter into primitive bodies such as comets. We will reach this goal by following the chemistry of interstellar material as it accreted into the nebula. We will then calculate the spatial and temporal evolution of the organic chemistry in the comet-forming region (5-40 AU) of the protosolar nebula using detailed dynamical-chemical models. This will allow cometary composition to be calculated as a function of nebular physical processes and will elucidate the likely organic inventory of the comets that gave the early Earth it initial budget of volatile material. We will also seek to identify and quantify the pathways to molecular complexity attainable by both solid state and gas phase interstellar processes. This will involve fully time-dependent Monte Carlo simulations of the diffusion and reaction of atoms and radicals on grain surfaces. We will also employ gas-grain chemical models, using recent laboratory data, to study the direct interstellar production of amino acids in hot molecular cores. We will also elucidate, through coma chemical models, which of the trace molecules observed in Comets Hyakutake and Hale-Bopp could actually be formed in the coma from fragmentation of large organic dust particles. A study of gas-phase switching of nuclear ortho:para spin ratios will also be carried out. Finally, we will undertake a limited program of radio observations to search for new organics.