10:00 〜 10:15
[PPS03-05] Understanding mm scale heterogeneity for amino acids in carbonaceous chondrite meteorites.
キーワード：Carbonaceous chondrites, Amino acids, Heterogeneity, Building blocks of life, Asteroids, Meteorites
Asteroids and comets represent the material that was left over after the formation of the planets. Such bodies would have initially formed from material within the protosolar nebular around the protosun and thus can preserve clues about the processes that operated during this period of the Solar System [1]. While many studies have investigated the amino acid abundances within bulk meteorite samples or more recently in small fragments of meteorites and asteroid return samples (several mg to 10’s of mg), the mm-scale heterogeneity of small meteorite fragments has not yet been investigated [1-3]. Such an investigation is important, because studies of the same meteorite have often recorded different abundances for amino acids and it is yet unclear whether this relates to biases introduced due the sample processing and analytical techniques, from the potential influence of terrestrial contamination, or due to inherent heterogeneity within a given carbonaceous chondrite sample at the mm scale [3].
The recent development of highly sensitive techniques, which can detect meteoritic amino acids within tiny sample sizes (several mg) has paved the way for such an investigation [2]. During analysis of two Ryugu particles returned from JAXA’s Hayabusa2 mission, significant differences between the amino acid abundances between a particle from touchdown site (TD) 1 and TD 2 indicated that the amino acid abundances in Ryugu were heterogenous over a scale of ~870 m. However, it remained unclear whether heterogeneity was present over smaller distances and if it was unique to Ryugu or common to other asteroidal fragments, such as carbonaceous chondrites. Here the results of an investigation into the mm-scale amino acid heterogeneity within carbonaceous chondrites are reported. The results indicate that individual carbonaceous chondrite meteorites demonstrate significant heterogeneities (intra-meteorite) in terms of their amino acid abundances and abundance ratios over the mm scale. Despite the intra-meteorite heterogeneities, the samples also show distinct differences between different meteorites (inter-meteorite). The b-alanine/glycine ratio indicates that the CM2 meteorites (Murchison and Aguas Zarcas) experienced less aqueous alteration than the CI1 meteorite (Orgueil), in line with the results of previous studies. Meanwhile, many of the non-protein amino acids also recorded heterogeneities in their abundances and the abundance of the protein forming amino acids phenylalanine and tyrosine (common terrestrial contaminants) were low in all samples, indicating that terrestrial contamination did not represent a significant influence on the amino acid inventory of the meteorite samples.
Overall, the results shed light on the inherent heterogeneity of carbonaceous chondrites. Such findings are of high importance to those who study the origin and evolution of organic matter within our solar system, because any processes that are proposed to explain the origin and evolution of organic matter must be able to explain this inherent heterogeneity. The findings are also important for the interpretation of samples returned from asteroids, for instance how well can a small sample represent the bulk organic inventory of a large asteroid. Furthermore, future development of sample return missions should take into account the required amount of sample and number of sample sites that are necessary to understand the bulk organic composition of a primitive asteroid.
[1] E. Nakamura et al., Proceedings of the Japan Academy, Series B. 98, 6, 227–282 (2022).
[2] C. Potiszil et al., Nature Communications, 14(1), 1482 (2023).
[3] C. Potiszil et al., Life, 13(7), 1448 (2023).
The recent development of highly sensitive techniques, which can detect meteoritic amino acids within tiny sample sizes (several mg) has paved the way for such an investigation [2]. During analysis of two Ryugu particles returned from JAXA’s Hayabusa2 mission, significant differences between the amino acid abundances between a particle from touchdown site (TD) 1 and TD 2 indicated that the amino acid abundances in Ryugu were heterogenous over a scale of ~870 m. However, it remained unclear whether heterogeneity was present over smaller distances and if it was unique to Ryugu or common to other asteroidal fragments, such as carbonaceous chondrites. Here the results of an investigation into the mm-scale amino acid heterogeneity within carbonaceous chondrites are reported. The results indicate that individual carbonaceous chondrite meteorites demonstrate significant heterogeneities (intra-meteorite) in terms of their amino acid abundances and abundance ratios over the mm scale. Despite the intra-meteorite heterogeneities, the samples also show distinct differences between different meteorites (inter-meteorite). The b-alanine/glycine ratio indicates that the CM2 meteorites (Murchison and Aguas Zarcas) experienced less aqueous alteration than the CI1 meteorite (Orgueil), in line with the results of previous studies. Meanwhile, many of the non-protein amino acids also recorded heterogeneities in their abundances and the abundance of the protein forming amino acids phenylalanine and tyrosine (common terrestrial contaminants) were low in all samples, indicating that terrestrial contamination did not represent a significant influence on the amino acid inventory of the meteorite samples.
Overall, the results shed light on the inherent heterogeneity of carbonaceous chondrites. Such findings are of high importance to those who study the origin and evolution of organic matter within our solar system, because any processes that are proposed to explain the origin and evolution of organic matter must be able to explain this inherent heterogeneity. The findings are also important for the interpretation of samples returned from asteroids, for instance how well can a small sample represent the bulk organic inventory of a large asteroid. Furthermore, future development of sample return missions should take into account the required amount of sample and number of sample sites that are necessary to understand the bulk organic composition of a primitive asteroid.
[1] E. Nakamura et al., Proceedings of the Japan Academy, Series B. 98, 6, 227–282 (2022).
[2] C. Potiszil et al., Nature Communications, 14(1), 1482 (2023).
[3] C. Potiszil et al., Life, 13(7), 1448 (2023).