title: Temporal and Spatial Variation of the Organic Particles in the Proto-Solar Disk

authors: M. Numata, H. Nagahara

abstract: More than 80 distinct amino acids are discovered in meteorites, which are suggested to be extraterrestrial origin. Even the detection of glycine has been claimed in samples from comet 81P/Wild 2. These discoveries suggest that interstellar chemistry can produce such complex molecules. Motivated by these studies, some observational search reported to detect acetic complex molecules in molecular cloud. More recently, ALMA observation is expected to find more complexity of such organic materials. 
Organic materials in the asteroids and comets may be derived from molecular clouds and processed in proto-solar disk. Interstellar dusts were incorporated into the proto-solar molecular cloud and were heated to evaporate in the proto solar nebula. Since the degree of evaporation depends on temperature of the solar nebula, chemical compositions of the dusts in the solar nebula would vary from place to place and with time.
We calculated viscous disk evolution and particle motion simultaneously in order to investigate temperature change of individual particles. Particles are released at each 10AU at t = 0. The starting material is assumed to be a particle that consists of silicate core and organics and the chemical composition is taken from that for 297K of Nakano et al. (2003). When heated, the C and N composition of particles varies according to Nakano et al. (2003), but do not vary if temperature decreases. By summing up all the grains with different thermal history located at every 1AU at a certain time, the local bulk chemical composition of organics in the disk is obtained.
The temporal change of gas temperature and distribution of particles shows that particles initially located in the low-temperature outer region drift inward, and that thermally unprocessed organic particles were present in the inner region after 10^6 years. The temporal-spatial variation of C and N contents and C/N ratio of organic particles indicates chemical variation of the inner region (<10AU). Silicate-organics complex grains from a molecular cloud were partially evaporated to be poor in organic materials inside 5AU at the early stage of the proto-solar disk. As temperature decreases with disk evolution, chemical composition of organic materials in the inner regions of the disk change from fractionated to unfractionated composition. This result shows that composition of organic materials accrete to a planetesimal depend on when the planetesimal is formed.