Host: The Japanese Society for Planetary Sciences: Local Organizing Committee for 2006 Fall Meeting
Oxygen isotopic composition of chondritic constituents(CAIs and chondrules) implies the existence of 16O-rich/17O- and 18O-rich oxygen reservoirs and the mechanicalmixing of them with various mixing ratio in the solarnebula. Recent studies suggest that CO self-shieldingeffect in parent molecular clouds produces the 16O-rich CO gas and 17O- and 18O-rich H2O ice.In this study, the mixing process of these reservoirsand its effect on the oxygen isotopic composition ofprotoplanetary accretion disks are proposed. Due to thepreferential dust transport in an accretion disk,17O- and 18O-rich H2O vapor enriches inside thesnow line. The degree of enrichment increases with decayof T Tauri accretion, following that the oxygen isotopiccomposition of the inner disk gradually evolves from16O-rich to 17O- and 18O-rich. We numerically simulateabove processes for the main oxygen reservoirs includingH2O and silicate, and follow the oxygen isotopicevolution quantitatively. Results are compared with theisotopic and chronological analysis of CAIs and chondrulesto clarify the oxygen isotopic evolution in the solar nebula.
