[P-PS24_1PO1] Origin and evolution of materials in space

[PPS24-P05] A New Experiment for Organic Molecule Formation by Catalytic Reactions on the Surface at Low Temperature and Pressure

*Yuki KIMURA¹, Akira TSUCHIYAMA², Hiroko NAGAHARA³ (1.Tohoku University, 2.Division of Earth and Planetary Sciences, Graduate School of Sciece, Kyoto University, 3.Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo)

Keywords:Organic molecules, Catalytic reactions, Protoplanetary system

Abundant H₂, CO and N₂ gases react to be more complex molecules mainly on the cooled surface of cosmic dust particles in the molecular cloud and/or primitive solar nebula [1]. The production of organic molecules and subsequent evolution to organic materials in the solar nebula may contribute to the primordial organic system of the Earth. Catalytic chemical reactions are possible production pathway of organic materials in the solar nebula after the formation of simple molecules on nanometer sized cosmic dust particles in the molecular clouds. Experimentally, organic molecules ranging from methane (CH₄), ethane (C₂H₆), benzene (C₆H₆) and toluene (C₇H₈), to more complex species such as acetone (C₃H₆O), methyl amine (CH₃NH₂), acetonitrile (CH₃CN) and N-methyl methylene imine (H₃CNCH₂) have been produced using such as the Fischer-Tropsch type (FTT) and Haber-Bosch type (HBT) reactions on analogs of naturally occurring grain surfaces [2]. Previous studies were performed at higher-temperature (>573 K) and pressure (〜1 atm) than the expected conditions in the solar nebula [3-6]. However, since the actual environment is at lower temperature and pressure, it is not clear whether the previous experimental results can be extrapolated to the solar nebula. Our group seeks to elucidate the reaction rates of chemical reactions including isotopic fractionation at lower temperature (100-500 K) and pressure (10^-3-10⁰) and their contribution to the primordial organic system of the Earth. We are constructing a vacuum chamber based on a new concept to conduct the experiments mentioned above. The chamber with a differential pumping system has a temperature-controlled substrate, a Fourier transform infrared spectrometer (FT-IR), and two quadrupole mass spectrometers (Q-MSs). The substrate has an iron or silicate thin film for FTT and HBT reactions and the FT-IR measures the vibration modes of adsorbed and produced molecules on the surface and the Q-MSs detect volatile and nonvolatile molecules, respectively. As a result, reaction rates of molecules such as H₂, CO, N₂ and NH₃ on iron or silicate substrate will be obtained as a function of temperature and pressure.[1] J. Llorca and I. Casanova, Meteorit. Planet. Sci. 35, 841 (2000).[2] H. G. G. M. Hill, and J. A. Nuth, Astrobiology 3, 291 (2003).[3] J. A. Nuth, N. M. Johnson, and S. Manning, The Astrophysical Journal 673, L225 (2008).[4] J. A. Nuth, N. M. Johnson, and S. Manning, Organic matter in space, Proc. IAU Symp. 251, edited by S. Kwok and S. Sandford, Cambridge Univ. Press, NY (2008), pp. 403-408.[5] J. A. Nuth, Y. Kimura, C. Lucas, F. Ferguson, and N. M. Johnson, The Astrophysical Journal Letters 710, 98 (2010).[6] Y. Kimura, J. A. Nuth, N. M. Johnson, K. D. Farmer, K. P. Roberts, and S. R. Hussaini, Nanoscience and Nanotechnology Letters 3, 4 (2011).