[P-PS07] 太陽系物質進化

[PPS07-02] Isotopic constraint on the origin of organic matter in carbonaceous chondrites

*古川 善博¹、岩佐 義也¹、力石 嘉人² (1.東北大学大学院理学研究科、2.北海道大学低温科学研究所)

Many solvent-soluble organic matters (SOM) in carbonaceous chondrites such as sugars, amino acids, amines, and aldehydes are enriched in ¹³C. The reason for the ¹³C enrichment has not been clear but discussed as some contributions from precursor materials formed in the cold outer solar system. Several reactions/processes have been proposed for the origin of meteorite amino acids, including their formation by the photochemical reaction in a molecular cloud, Fischer–Tropsch type reaction in the solar nebula, Strecker reaction, and Formose-type reaction in the meteorite parent bodies. Formose-type reaction is also discussed as a potential synthetic reaction of solvent insoluble organic matter (IOM) that is the primary carbon host in meteorites and has carbon isotope characteristic depleted in ¹²C. We hypothesized that kinetic isotope fractionation during the Formose-type reaction might form the large carbon isotope difference between SOM and IOM and conducted experiments to investigate this fractionation. The product amino acids and sugars have significantly enriched in ¹³C compared with the product IOM analogue. The extents of enrichment are comparable to that have been found in several carbonaceous chondrites. This result proved an isotopic constraint on the formation reactions/processes of organic matter found in carbonaceous chondrites.