15:45 〜 16:00
[PCG20-08] 炭素質隕石・非炭素質隕石の同位体組成バリエーション
★招待講演
キーワード：同位体不均質、惑星形成、同位体二分性
The formation process of planetesimals is key to understand the history of the early solar system. The heterogeneous isotopic compositions were preserved in the early solar nebula due to the incomplete mixing of presolar materials. Isotopic variations recorded in bulk-scale meteorites will provide the important constraint for the temporal and spatial heterogeneities in the early solar system.
New finding within bulk-scale meteorites is the materials in the early solar system can be classified into two groups, carbonaceous chondrites (CC) and non-carbonaceous meteorites (NC) [1]. Bulk-scale CC possibly record the primordial information associated with the formation process of their parent bodies. We tried to estimate the relative formation region of parent bodies of CC by utilizing the nucleosynthetic Cr isotopic variation (54Cr/52Cr) [2]. We speculate that the heterogeneities in the other types of supernova-derived nuclides (e.g., 50Ti and 64Ni) can be explained by the similar mechanism. Also, CC show the isotopic variation in trans-iron elements such as Sr, Mo, and Nd [3–5]. This may be explained by the two-component mixing of s-process-rich and s-process-poor materials in the early solar nebula.
The isotopic compositions of NC would reflect the accretional histories of the terrestrial planets. Generally, the plots of the Earth are the endmembers in the two-component mixing line for trans-iron elements [3–5]. Therefore, this is difficult to reproduce the terrestrial isotopic compositions by the mixings of existing meteorite data. We should try the multiple, high-precision isotopic measurements for the planetary materials which would possess terrestrial-like isotopic compositions (e.g., enstatite chondrite, aubrite, and IAB irons). Furthermore, E-type asteroids are possible targets for a next sample-return mission to understand the formation of the Earth.
[1] Kruijer et al. (2017) PNAS, 114, 6712. [2] Fukai and Arakawa (2021) ApJ, 908, 64. [3] Fukai and Yokoyama (2019) ApJ, 879, 79. [4] Yokoyama et al. (2019) ApJ, 883, 62. [5] Fukai and Yokoyama (2017) EPSL, 474, 206.
New finding within bulk-scale meteorites is the materials in the early solar system can be classified into two groups, carbonaceous chondrites (CC) and non-carbonaceous meteorites (NC) [1]. Bulk-scale CC possibly record the primordial information associated with the formation process of their parent bodies. We tried to estimate the relative formation region of parent bodies of CC by utilizing the nucleosynthetic Cr isotopic variation (54Cr/52Cr) [2]. We speculate that the heterogeneities in the other types of supernova-derived nuclides (e.g., 50Ti and 64Ni) can be explained by the similar mechanism. Also, CC show the isotopic variation in trans-iron elements such as Sr, Mo, and Nd [3–5]. This may be explained by the two-component mixing of s-process-rich and s-process-poor materials in the early solar nebula.
The isotopic compositions of NC would reflect the accretional histories of the terrestrial planets. Generally, the plots of the Earth are the endmembers in the two-component mixing line for trans-iron elements [3–5]. Therefore, this is difficult to reproduce the terrestrial isotopic compositions by the mixings of existing meteorite data. We should try the multiple, high-precision isotopic measurements for the planetary materials which would possess terrestrial-like isotopic compositions (e.g., enstatite chondrite, aubrite, and IAB irons). Furthermore, E-type asteroids are possible targets for a next sample-return mission to understand the formation of the Earth.
[1] Kruijer et al. (2017) PNAS, 114, 6712. [2] Fukai and Arakawa (2021) ApJ, 908, 64. [3] Fukai and Yokoyama (2019) ApJ, 879, 79. [4] Yokoyama et al. (2019) ApJ, 883, 62. [5] Fukai and Yokoyama (2017) EPSL, 474, 206.