[P-PS24] 宇宙における物質の形成と進化

[PPS24-15] 初期太陽系星雲中でのFT型触媒反応による分子形成の再現実験

*木村 勇気¹、山﨑 智也¹、土山 明²、永原 裕子³、羽馬 哲也¹、日高 宏¹、渡部 直樹¹、香内 晃¹ (1.北海道大学低温科学研究所、2.京都大学、3.東京大学)

キーワード：有機物, 触媒反応, 分子生成, 低温科学, 太陽系星雲

Catalytic reactions such as the Fischer-Tropsch type and Haber-Bosch type reactions are able to produce organic molecules efficiently on the surface of cosmic dust analogues, such as iron, magnetite, amorphous iron silicate and graphite at temperature above 573 K and pressure at 10⁵ Pa in the laboratory [1-4]. In these experiments, 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 so far. However, it is not obvious the reaction similarly works in the solar nebula and is able to extrapolate to the actual early nebula environment at lower temperature below 500 K and lower pressure under 10² Pa. Therefore, we developed a new experimental system to test the catalytic chemical reactions in the early nebula environment [lower temperature (100-500 K) and pressure (10^-3-10⁰ Pa)] using a substrate of magnesium silicate or iron. Our experimental system has a temperature-controlled substrate, a Fourier transform infrared spectrometer (FT-IR), and two quadrupole mass spectrometers (Q-MSs). FT-IR measures the vibration modes of adsorbed and produced molecules on the surface and the Q-MSs detect volatile molecules, respectively. As a preliminary experiment, the substrate of a magnesium silicate thin film was used in a continuous gas flow of a mixture gas of H₂ and CO for Fischer-Tropsch type reactions. Unfortunately, however, we do not find any signal of the Fischer-Tropsch type reaction and resulting organic molecules on the amorphous magnesium substrate, whereas the signal of CHO molecule and ethane (C₂H₆) have been detected on the Q-MS spectra in some experimental condition on a different substrate. In the workshop, the detail results using iron substrate will be presented as a function of temperature and pressure.

References
[1] H. G. M. Hill, J. A. Nuth, Astrobiology, 3 (2003) 291.
[2] J. A. Nuth, N. M. Johnson, S. Manning, The Astrophysical Journal, 673 (2008) L225.
[3] N. M. Johnson, M. McCarthy, J. A. Nuth III, 45th Lunar and Planetary Science Conference, (2014) 2702.
[4] J. A. Nuth, Y. Kimura, C. Lucas, F. Ferguson, N. M. Johnson, The Astrophysical Journal Letters, 710 (2010) 98.
[5] Y. Kimura, J. A. Nuth, N. M. Johnson, K. D. Farmer, K. P. Roberts, S. R. Hussaini, Nanoscience and Nanotechnology Letters, 3 (2011) 4.