慶應義塾研究者情報データベース

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• プレスリリース：2024年
  『小惑星リュウグウの水に満ちた化学進化の源流と水質変成の証拠』
  
  慶應義塾大学 先端生命科学研究所：
  https://www.iab.keio.ac.jp/news-events/2024/07111755.html
  
  掲載誌：
  Nature Communications
  
  タイトル：
  Primordial aqueous alteration recorded in water-soluble organic molecules from the carbonaceous asteroid (162173) Ryugu.
  
  論文サイト：
  https://doi.org/10.1038/s41467-024-49237-6
  
  プレス詳細：
  https://www.jamstec.go.jp/j/about/press_release/20240710/

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• Primordial aqueous alteration recorded in water-soluble organic molecules from the carbonaceous asteroid (162173) Ryugu

  Takano, Y., Naraoka, H., Dworkin, J.P., Koga, T., Sasaki, K., Sato, H., Oba, Y., Ogawa, N.O., Yoshimura, T., Hamase, K., Ohkouchi, N., Parker, E.T., Aponte, J.C., Glavin, D.P., Furukawa, Y., Aoki, J., Kano, K., Nomura, S.-i.M., Orthous-Daunay, F.-R., Schmitt-Kopplin, P., Yurimoto, H., Nakamura, T., Noguchi, T., Okazaki, R., Yabuta, H., Sakamoto, K., Yada, T., Nishimura, M., Nakato, A., Miyazaki, A., Yogata, K., Abe, M., Okada, T., Usui, T., Yoshikawa, M., Saiki, T., Tanaka, S., Terui, F., Nakazawa, S., Watanabe, S.-i., Tsuda, Y., Tachibana, S.

  Nature Communications （Nature Publishing Group）  15   5708 2024年07月

  研究論文（学術雑誌）, 共著, 筆頭著者, 責任著者, 査読有り

  • Access to Document (DOI)
  • Access to Document (DOI)

• Polycyclic aromatic hydrocarbons in samples of Ryugu formed in the interstellar medium

  Zeichner S.S., Aponte J.C., Bhattacharjee S., Dong G., Hofmann A.E., Dworkin J.P., Glavin D.P., Elsila J.E., Graham H.V., Naraoka H., Takano Y., Tachibana S., Karp A.T., Grice K., Holman A.I., Freeman K.H., Yurimoto H., Nakamura T., Noguchi T., Okazaki R., Yabuta H., Sakamoto K., Yada T., Nishimura M., Nakato A., Miyazaki A., Yogata K., Abe M., Okada T., Usui T., Yoshikawa M., Saiki T., Tanaka S., Terui F., Nakazawa S., Watanabe S.I., Tsuda Y., Hamase K., Fukushima K., Aoki D., Hashiguchi M., Mita H., Chikaraishi Y., Ohkouchi N., Ogawa N.O., Sakai S., Parker E.T., McLain H.L., Orthous-Daunay F.R., Vuitton V., Wolters C., Schmitt-Kopplin P., Hertkorn N., Thissen R., Ruf A., Isa J., Oba Y., Koga T., Yoshimura T., Araoka D., Sugahara H., Furusho A., Furukawa Y., Aoki J., Kano K., Nomura S.I.M., Sasaki K., Sato H., Yoshikawa T., Tanaka S., Morita M., Onose M., Kabashima F., Fujishima K., Yamazaki T., Kimura Y., Eiler J.M.

  Science （Science）  382 （ 6677 ） 1411 - 1416 2023年12月

  ISSN  00368075

  　概要を見る

  Polycyclic aromatic hydrocarbons (PAHs) contain ≲20% of the carbon in the interstellar medium. They are potentially produced in circumstellar environments (at temperatures ≳1000 kelvin), by reactions within cold (~10 kelvin) interstellar clouds, or by processing of carbon-rich dust grains. We report isotopic properties of PAHs extracted from samples of the asteroid Ryugu and the meteorite Murchison. The doubly-13C substituted compositions (D2×13C values) of the PAHs naphthalene, fluoranthene, and pyrene are 9 to 51% higher than values expected for a stochastic distribution of isotopes. The D2×13C values are higher than expected if the PAHs formed in a circumstellar environment, but consistent with formation in the interstellar medium. By contrast, the PAHs phenanthrene and anthracene in Ryugu samples have D2×13C values consistent with formation by higher-temperature reactions.

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• Uracil in the carbonaceous asteroid (162173) Ryugu

  Oba Y., Koga T., Takano Y., Ogawa N.O., Ohkouchi N., Sasaki K., Sato H., Glavin D.P., Dworkin J.P., Naraoka H., Tachibana S., Yurimoto H., Nakamura T., Noguchi T., Okazaki R., Yabuta H., Sakamoto K., Yada T., Nishimura M., Nakato A., Miyazaki A., Yogata K., Abe M., Okada T., Usui T., Yoshikawa M., Saiki T., Tanaka S., Terui F., Nakazawa S., Watanabe S.i., Tsuda Y.

  Nature Communications （Nature Communications）  14 （ 1 ）  2023年12月

  　概要を見る

  The pristine sample from the near-Earth carbonaceous asteroid (162173) Ryugu collected by the Hayabusa2 spacecraft enabled us to analyze the pristine extraterrestrial material without uncontrolled exposure to the Earth’s atmosphere and biosphere. The initial analysis team for the soluble organic matter reported the detection of wide variety of organic molecules including racemic amino acids in the Ryugu samples. Here we report the detection of uracil, one of the four nucleobases in ribonucleic acid, in aqueous extracts from Ryugu samples. In addition, nicotinic acid (niacin, a B3 vitamer), its derivatives, and imidazoles were detected in search for nitrogen heterocyclic molecules. The observed difference in the concentration of uracil between A0106 and C0107 may be related to the possible differences in the degree of alteration induced by energetic particles such as ultraviolet photons and cosmic rays. The present study strongly suggests that such molecules of prebiotic interest commonly formed in carbonaceous asteroids including Ryugu and were delivered to the early Earth.

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• Biomarkers in the Atacama Desert along the moisture gradient and the depth in the hyperarid zone: Phosphatase activity as trace of microbial activity

  Kobayashi K., Nauny P., Takano Y., Honma C., Kurizuka T., Ishikawa Y., Yogosawa S., Obayashi Y., Kaneko T., Kebukawa Y., Mita H., Ogawa M., Enya K., Yoshimura Y., McKay C.P.

  International Journal of Astrobiology （International Journal of Astrobiology）  21 （ 5 ） 329 - 351 2022年10月

  ISSN  14735504

  　概要を見る

  Microbiological activities can be detected in various extreme environments on Earth, which suggest that extraterrestrial environments, such as on Mars, could host life. There have been proposed a number of biomarkers to detect extant life mostly based on specific molecules. Because terrestrial organisms have catalytic proteins (enzymes), enzymatic activity may also be a good indicator to evaluate biological activities in extreme environments. Phosphatases are essential for all terrestrial organisms because phosphate esters are ubiquitously used in genetic molecules (DNA/RNA) and membranes. In this study, we evaluated microbial activity in soils of the Atacama Desert, Chile, by analysing several biomarkers, including phosphatase activity. Phosphatases extracted with Tris buffer were assayed fluorometrically using 4-methylumbelliferyl phosphate as a substrate. The horizontal distribution of phosphatase activity and other parameters in soils from the Atacama Desert showed that phosphatase activity was positively correlated with amino acid concentration and colony-forming units and negatively correlated with precipitation amount. We found consistent that biochemical indicators including phosphatase significantly decreased in the extreme hyper-arid zone where rainfall of <25 mm year-1. The results were compared with phosphatase activities detected in extreme environments, such as submarine hydrothermal systems and Antarctic soils, as well as soils from ordinary environments. Overall, our results suggested that phosphatase activity could be a good indicator for evaluating biological activities in extreme environments.

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• Precometary organic matter: A hidden reservoir of water inside the snow line

  Nakano H., Hirakawa N., Matsubara Y., Yamashita S., Okuchi T., Asahina K., Tanaka R., Suzuki N., Naraoka H., Takano Y., Tachibana S., Hama T., Oba Y., Kimura Y., Watanabe N., Kouchi A.

  Scientific Reports （Scientific Reports）  10 （ 1 ）  2020年12月

  　概要を見る

  The origin and evolution of solar system bodies, including water on the Earth, have been discussed based on the assumption that the relevant ingredients were simply silicates and ices. However, large amounts of organic matter have been found in cometary and interplanetary dust, which are recognized as remnants of interstellar/precometary grains. Precometary organic matter may therefore be a potential source of water; however, to date, there have been no experimental investigations into this possibility. Here, we experimentally demonstrate that abundant water and oil are formed via the heating of a precometary-organic-matter analog under conditions appropriate for the parent bodies of meteorites inside the snow line. This implies that H2O ice is not required as the sole source of water on planetary bodies inside the snow line. Further, we can explain the change in the oxidation state of the Earth from an initially reduced state to a final oxidized state. Our study also suggests that petroleum was present in the asteroids and is present in icy satellites and dwarf planets.

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