10:45 〜 11:00
[PPS03-12] はやぶさ２探査機で採集された小惑星リュウグウ試料に含まれる有機化合物
キーワード：小惑星リュウグウ、はやぶさ２、有機分子
Introduction: The Hayabusa2 spacecraft came back to Earth successfully after sampling the surface materials of near-Earth asteroid Ryugu. Ryugu is a Cb-type asteroid possessing a low-albedo surface with low abundance hydrous minerals [1], which has similar characteristics observed for carbonaceous meteorites. The Ryugu material is expected to contain organic matter. The occurrence of organic compounds in Ryugu samples provides clues to the evolution of prebiotic molecules and thermal condition as well as aqueous alteration of primitive asteroids in the Solar System. The SOM (soluble organic matter) team for Hayabusa2 initial analysis revealed organic molecular distributions of Ryugu samples using high-sensitive and high-resolution analytical techniques [2].
Samples and Methods: The aggregate samples of the Ryugu grains (A0106 and C0107) and ashed serpentine (as a blank) were extracted sequentially with non-polar to polar solvents. The extracts were analyzed using: 1) high-resolution mass spectroscopy (HRMS) using Fourier transform-ion cyclotron resonance/mass spectrometry (FT-ICR/MS) [3], 2) HRMS with nano-liquid chromatography using Orbitrap HRMS, 3) high performance liquid chromatography (HPLC) coupled with time-of-flight mass spectrometry (ToF-MS) with high-sensitive fluorescence detection (FD), and 4) two-dimensional gas chromatography (GC×GC) coupled with ToF-MS. The aggregate samples were also extracted with hot water followed by acid hydrolysis for amino acid analysis. Chiral amino acid analyses were performed using three-dimensional HPLC with FD [4] as well as ultrahigh precision LC coupled with Orbitrap HRMS. A ~1 mm-sized Ryugu grain (A0080) was used for: 6) in situ organic compound analysis and molecular imaging using desorption electrospray ionization (DESI) coupled with HRMS [5] and 7) spatial imaging of inorganic and organic compounds using ToF-secondary ion mass spectrometry (ToF-SIMS) [6]. 8) Total C, N, H and S elemental and isotopic compositions of A0106 and C0107 were determined using nano-elemental analysis/isotope ratio mass spectrometry (nanoEA-IRMS) [7].
Results and Discussion: The Ryugu samples contained total ~4 wt% C with ~1.2 wt% H and ~0.17 wt% N and ~3.3 wt% S, and heavy isotope enrichments of N (~ +43‰) and H (~ +250‰) were observed. The solvent extracts yielded a variety of plausibly prebiotic organic molecules including amino acids as well as aliphatic carboxylic acids and amines. More than 10 proteinogenic and non-proteinogenic amino acids were present as racemic mixtures (D/L ~1), indicating non-biological and extraterrestrial origins. N-containing heterocyclic compounds were also identified as their alkylated homologues, including pyridine-, pyrimidine- and imidazole-containing species. These N-heterocycles could have been synthesized in the parent body from ammonia and simple aldehydes [8]. Alkylated aromatic hydrocarbons including polycyclic aromatic hydrocarbons were also present. The DESI/HRMS analysis revealed heterogenous spatial distribution of organic compounds in the Ryugu grain. The association between hydrous mineral and organic matter will be important to preserve prebiotic molecules under a high-vacuum and solar irradiation environment. The prebiotic molecules can spread throughout the Solar System, potentially as interplanetary dusts from the surface of the asteroid by impacts or other causes.
References: [1] Kitazato K. et al. (2019) Science 364, 272. [2] Naraoka H. et al. (2022) submitted. [3] Schmitt-Kopplin P. et al. (2010) PNAS USA 107, 2763. [4] Hamase K. et al. (2014) Chromatography 35, 103. [5] Hashiguchi M. & Naraoka H. (2019) MAPS, 54, 452. [6] Naraoka H. et al. (2015) EPS 67, 67. [7] Ogawa N. O. et al. (2019) 82th METSOC Meeting, Abstract #6208. [8] Naraoka H. et al. (2017) ACS Earth & Space Chem. 1, 540.
The Hayabusa2-initial-analysis SOM team: Hiroshi Naraoka, Yoshinori Takano, Jason P. Dworkin, Kenji Hamase, Aogu Furusho, Minako Hashiguchi, Kazuhiko Fukushima, Dan Aoki, José C. Aponte, Eric T. Parker, Daniel P. Glavin, Hannah L. McLain, Jamie E. Elsila, Heather V. Graham, John M. Eiler, Philippe Schmitt-Kopplin, Norbert Hertkorn, Alexander Ruf, Francois-Regis Orthous-Daunay, Cédric Wolters, Junko Isa, Véronique Vuitton, Roland Thissen, Nanako O. Ogawa, Saburo Sakai, Toshihiro Yoshimura, Toshiki Koga, Haruna Sugahara, Naohiko Ohkouchi, Hajime Mita, Yoshihiro Furukawa, Yasuhiro Oba, Yoshito Chikaraishi.
The Hayabusa2-initial-analysis core: Shogo Tachibana, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Sei-ichiro Watanabe, Yuichi Tsuda.
Samples and Methods: The aggregate samples of the Ryugu grains (A0106 and C0107) and ashed serpentine (as a blank) were extracted sequentially with non-polar to polar solvents. The extracts were analyzed using: 1) high-resolution mass spectroscopy (HRMS) using Fourier transform-ion cyclotron resonance/mass spectrometry (FT-ICR/MS) [3], 2) HRMS with nano-liquid chromatography using Orbitrap HRMS, 3) high performance liquid chromatography (HPLC) coupled with time-of-flight mass spectrometry (ToF-MS) with high-sensitive fluorescence detection (FD), and 4) two-dimensional gas chromatography (GC×GC) coupled with ToF-MS. The aggregate samples were also extracted with hot water followed by acid hydrolysis for amino acid analysis. Chiral amino acid analyses were performed using three-dimensional HPLC with FD [4] as well as ultrahigh precision LC coupled with Orbitrap HRMS. A ~1 mm-sized Ryugu grain (A0080) was used for: 6) in situ organic compound analysis and molecular imaging using desorption electrospray ionization (DESI) coupled with HRMS [5] and 7) spatial imaging of inorganic and organic compounds using ToF-secondary ion mass spectrometry (ToF-SIMS) [6]. 8) Total C, N, H and S elemental and isotopic compositions of A0106 and C0107 were determined using nano-elemental analysis/isotope ratio mass spectrometry (nanoEA-IRMS) [7].
Results and Discussion: The Ryugu samples contained total ~4 wt% C with ~1.2 wt% H and ~0.17 wt% N and ~3.3 wt% S, and heavy isotope enrichments of N (~ +43‰) and H (~ +250‰) were observed. The solvent extracts yielded a variety of plausibly prebiotic organic molecules including amino acids as well as aliphatic carboxylic acids and amines. More than 10 proteinogenic and non-proteinogenic amino acids were present as racemic mixtures (D/L ~1), indicating non-biological and extraterrestrial origins. N-containing heterocyclic compounds were also identified as their alkylated homologues, including pyridine-, pyrimidine- and imidazole-containing species. These N-heterocycles could have been synthesized in the parent body from ammonia and simple aldehydes [8]. Alkylated aromatic hydrocarbons including polycyclic aromatic hydrocarbons were also present. The DESI/HRMS analysis revealed heterogenous spatial distribution of organic compounds in the Ryugu grain. The association between hydrous mineral and organic matter will be important to preserve prebiotic molecules under a high-vacuum and solar irradiation environment. The prebiotic molecules can spread throughout the Solar System, potentially as interplanetary dusts from the surface of the asteroid by impacts or other causes.
References: [1] Kitazato K. et al. (2019) Science 364, 272. [2] Naraoka H. et al. (2022) submitted. [3] Schmitt-Kopplin P. et al. (2010) PNAS USA 107, 2763. [4] Hamase K. et al. (2014) Chromatography 35, 103. [5] Hashiguchi M. & Naraoka H. (2019) MAPS, 54, 452. [6] Naraoka H. et al. (2015) EPS 67, 67. [7] Ogawa N. O. et al. (2019) 82th METSOC Meeting, Abstract #6208. [8] Naraoka H. et al. (2017) ACS Earth & Space Chem. 1, 540.
The Hayabusa2-initial-analysis SOM team: Hiroshi Naraoka, Yoshinori Takano, Jason P. Dworkin, Kenji Hamase, Aogu Furusho, Minako Hashiguchi, Kazuhiko Fukushima, Dan Aoki, José C. Aponte, Eric T. Parker, Daniel P. Glavin, Hannah L. McLain, Jamie E. Elsila, Heather V. Graham, John M. Eiler, Philippe Schmitt-Kopplin, Norbert Hertkorn, Alexander Ruf, Francois-Regis Orthous-Daunay, Cédric Wolters, Junko Isa, Véronique Vuitton, Roland Thissen, Nanako O. Ogawa, Saburo Sakai, Toshihiro Yoshimura, Toshiki Koga, Haruna Sugahara, Naohiko Ohkouchi, Hajime Mita, Yoshihiro Furukawa, Yasuhiro Oba, Yoshito Chikaraishi.
The Hayabusa2-initial-analysis core: Shogo Tachibana, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Sei-ichiro Watanabe, Yuichi Tsuda.