| 1. |
J. Park, R. Okazaki, A. Yamaguchi, M. Inagaki, and A. J. Irving, 40Ar/39Ar analyses on Martian meteorites, Yamato 002712, Asuka 12325 and Northwest Africa 12542
, 55th Lunar and Planetary Science Conference, 2024.03. |
| 2. |
Nishiizumi, K.; Caffee, M. W.; Nagao, K.; Masarik, J.; Okazaki, R.; Yurimoto, H.; Nakamura, T.; Noguchi, T.; Naraoka, H.; Yabuta, H.; Sakamoto, K.; Tachibana, S.; Watanabe, S.; Tsuda, Y.; Hayabusa2-Initial-Analysis Volatile Team, Exposure Conditions of Samples Collected on Ryugu's Two Touchdown Sites Determined by Cosmogenic Nuclides 10Be and 26Al, 54th Lunar and Planetary Science Conference, 2023.03. |
| 3. |
Tachibana, S.; Yurimoto, H.; Nakamura, T.; Noguchi, T.; Okazaki, R.; Yabuta, H.; Naraoka, H.; Hayabusa2-Initial-Analysis Team, Initial Analysis Activity of Hayabusa2-Returned Samples from C-Type Near-Earth Asteroid (162173) Ryugu, 85th Annual Meeting of The Meteoritical Society, 2022.08. |
| 4. |
Meshik, A.; Pravdivtseva, O.; Okazaki, R.; Yurimoto, H.; Nakamura, T.; Noguchi, T.; Naraoka, H.; Yabuta, H.; Sakamoto, K.; Tachibana, S.; Watanabe, S.; Tsuda, Y.; Hayabusa2-Initial-Analysis Volatile Team, Noble Gas Isotopic Analyzes of the Asteroid Ryugu Samples: Initial Results of Multi-Step Pyrolysis, 85th Annual Meeting of The Meteoritical Society, 2022.08. |
| 5. |
Broadley, M. W.; Byrne, D. L.; Füri, E.; Marty, B.; Okazaki, R.; Yurimoto, H.; Nakamura, T.; Noguhi, T.; Naraoka, H.; Yabuta, H.; Sakamoto, K.; Tachibana, S.; Watanabe, S.; Tsuda, Y.; Hayabusa Initial Analysis Volatile Team, Investigating the Nitrogen-Noble Gas Relationship of Asteroid Ryugu and the Link to Other Carbonaceous Chondrites, 85th Annual Meeting of The Meteoritical Society, 2022.08. |
| 6. |
Nagao, K.; Okazaki, R.; Nishiizumi, K.; Caffee, M. W.; Masarik, J.; Yurimoto, H.; Nakamura, T.; Noguchi, T.; Naraoka, H.; Yabuta, H.; Sakamoto, K.; Tachibana, S.; Watanabe, S.; Tsuda, Y.; Hayabusa2-Initial-Analysis Volatile Team, Noble Gases of Eight Hayabusa2 Samples from the Asteroid Ryugu, 85th Annual Meeting of The Meteoritical Society, 2022.08. |
| 7. |
Hendrix, Amanda R.; Vilas, Faith; JaramilloCorrea, Camilo; Pearson, Neil; Zolensky, Mike E.; Domingue, Deborah L.; Clark, Roger Nelson; Allain, Jean Paul; Nakamuna, Tomoki; Matsuoka, Moe; Amano, Kana; Morita, Tomoyo; Kikuiri, Mizuha; Naraoka, Hiroshi; Sakamoto, Kanako; Kagawa, Eiichi; Yurimoto, Hisayoshi; Noguchi, Takaaki; Okazaki, Ryuji; Yabuta, Hikaru; Tachibana, Shogo; Watanabe, Seiichiro; Tsuda, Yuichi, UV-Visible Reflectance Spectra of Grains Returned from 162173 Ryugu Unexposed to Earth's Atmosphere, AGU Fall Meeting 2022, 2022.11. |
| 8. |
Sato, Masahiko; Kimura, Yuki; Tanaka, Satoshi; Hatakeyama, Tadahiro; Sugita, Seiji; Nakamuna, Tomoki; Tachibana, Shogo; Okuzumi, Satoshi; Watanabe, Seiichiro; Yurimoto, Hisayoshi; Noguchi, Takaaki; Okazaki, Ryuji; Yabuta, Hikaru; Naraoka, Hiroshi; Sakamoto, Kanako; Yada, Toru; Nishimura, Masahiro; Nakato, Aiko; Miyazaki, Akiko; Yogata, Kasumi; Abe, Masanao; Okada, Tatsuaki; Usui, Tomohiro; Yoshikawa, Makoto; Saiki, Takanao; Terui, Fuyuto; Nakazawa, Satoru; Tsuda, Yuichi, Rock-magnetic and paleointensity studies of returned samples from asteroid (162173) Ryugu, AGU Fall Meeting 2022, 2022.12. |
| 9. |
R. Okazaki, B. Marty, H. Busemann, K. Hashizume, J. Gilmour, A. Meshik, T. Yada, F. Kitajima, M.W. Broadley, D. Byrne, E. Füri, M.E.I. Riebe, D. Krietsch, C. Maden, A. Ishida, P. Clay, S. Crowther, L. Fawcett, T. Lawton, O. Pravdivseva, J. Park, K. Bajo, Y. Takano, K. Yamada, S. Kawagucci, Y. Matsui, M. Yamamoto, Y.N. Miura, K. Righter, S. Sakai, N. Iwata, N. Shirai, S. Sekimoto, M. Inagaki, M. Ebihara, R. Yokochi, K. Nishiizumi, K. Nagao, J.I. Lee, A. Kano, M.W. Caffee, R. Uemura, T. Nakamura, H. Naraoka, T. Noguchi, H. Yabuta, H. Yurimoto, S. Tachibana, H. Sawada, K. Sakamoto, S. Watanabe, and Y. Tsuda, Isotopic compositions of noble gases and nitrogen in the Ryugu samples returned by Hayabusa2, The 53rd Lunar and Planetary Science Conference, 2022.03, Introduction: In December 2014, the Hayabusa2 spacecraft launched to visit the C-type asteroid (162173) Ryugu to bring back surface and subsurface materials to the Earth. The spacecraft arrived at Ryugu on June 27, 2018, and subsequently carried out two touchdowns (TDs) and sample collections. [1]. The 1st TD was carried out and collected surface samples, while the 2nd TD was done to collect the impact ejecta near the artificial crater made by the Small Carry-on Impactor operation in April 2019 [1]. Samples collected during the 1st and 2nd TDs were stored in Chamber A and C of the Hayabusa2 sample catcher, respectively [2]. Our principal objective is to quantify the indigenous compositions of the Ryugu samples with as little terrestrial contamination as possible. Here we report the isotopic ratios and concentrations of noble gases and nitrogen in the Ryugu samples allocated to the Hayabusa2-initial-analysis-volatile team.
Samples and Experimental method: The samples both from Chamber A (A0105- series) and from Chamber C (C0106- series) were allocated to the volatile sub-team. These samples are typically 0.8 mm-sized individual grains, not clumps of powders. Each of the samples was pressed onto diamond disks and pelletized for the Fourier-Transform Infrared (FT-IR) spectroscopy and Field-Emission Scanning Electron Microscope (FESEM) observations prior to isotope analyses. To avoid contamination from the Earth’s atmosphere, we treated the samples under a pure nitrogen environment or in vacuum during the entire procedures from the sample preparation to the isotope analyses [3]. In addition to the pelletized samples, noble gases were analyzed in some fragments generated during the pelletization process. Noble gas analyses were performed at Kyushu U., ETH, U. Manchester, and Washington U., while noble gas and nitrogen isotopes were measured at CRPG-Nancy and Ibaraki U.
Results and Discussion: Twenty-four pelletized samples were measured for FT-IR and FESEM to characterize their petrology and mineralogy. The FESEM observation revealed that all of the Ryugu samples consist of a phyllosilicate-rich fine-grained matrix, with variable amounts of magnetite and Fe-sulfide, which are consistent with the other Ryugu samples allocated to different sub-teams [4, 5], and show similarities with CI chondrites. Reflectance spectra of our samples are also consistent with the previous reports on the Ryugu grains [e.g., 6].
The modal abundances of magnetite and Fe-sulfide are similar to those of typical CI lithology, which indicates that our samples are not magnetite or sulfide-rich CI clasts [7], CM, or CY chondrite materials [8].
Isotopic ratios of Ne in the Ryugu samples (Fig. 1) are similar to those in Orgueil and Ivuna [9], and can be explained by a mixing between solar wind (SW) [10], planetary-type Ne (P1 or Q gas: [11, 12]), and presolar HL Ne [12]. Based on the Ne isotopic ratios, we calculated cosmogenic 21Ne concentrations by weighted mean to be 5.0 and 4.6 ×10-9 cm3STP/g for the Ryugu-A (except for SW-rich A0105-15) and for the Ryugu-C samples, respectively. The measured 10Be concentrations [13] suggest shielding depths of 2–20 g/cm2 (relatively shallow) and one of 150 g/cm2 (deeper) for the Ryugu-A and C samples, respectively. Based on these measurements in conjunction with the production rates [14] for the CI chemistry [15], we obtained the cosmic ray exposure ages of 5.6 and 5.7 Myr for the Ryugu-A and C samples, respectively. For the SW-rich A0105-15, we assumed the shallowest shielding of 0–1 g/cm2 and obtained several hundreds of kyr using its cosmogenic 21Ne of 1.1×10-9 cm3STP/g. We concluded that most of the Ryugu materials resided at a subsurface layer of Ryugu beneath an uppermost layer of material that have been exposed to solar wind irradiation.
Isotopic ratios of nitrogen in our samples are depleted in 15N compared to those in the other sub-teams’ Ryugu samples [16, 17] and CI chondrites [e.g., 18] (Fig. 2). The nitrogen concentrations are also lower than those in CI chondrites and the other Ryugu samples. The two samples of A0105-07 and C0106-07 plot close to the Yamato-980115 dehydrated CI chondrite [19]. The variations observed in the δ15N and the nitrogen contents can be attributed to sample heterogeneity at a small scale of samples, and suggest that there are at least two different carrier phases of nitrogen in the Ryugu samples; one is nitrogen-depleted and has a lower δ15N value, while the other is nitrogen-enriched and has a higher δ15N value. A linear trend is observed among the Ryugu samples and CI chondrites, from which we can estimate the δ15N value to be ~70 ‰ for the 15N-rich end member. The similarity with the dehydrated CI chondrite Y-980115 suggests that some dehydration or devolatilization effect may be responsible for the depletion of the 15N-rich phase from our samples, although the mineralogy of the Ryugu samples does not show heavily metamorphosed features as Y-980115 does.
Acknowledgments: RO was supported by JSPS KAKENHI Grant Numbers JP19H01959 and JP20H05846. BM, EF, MWB and DB were supported by the European Research Council (PHOTONIS Advanced Grant # 695618 and VOLATILIS Starting Grant 715028) and by the Centre National d’Etudes Spatiales (CNES). Work by D.K., M.R. and H.B. has been carried out within the framework of the NCCR Planets and the Ambizione program supported by the Swiss NSF. JG, SC, TL and LF were funded by STFC grants numbers ST/R000751/1 and ST/V000675/1. PLC was supported by UKRI FLF grant number MR/S03465X/1. KH and AI were supported by JSPS KAKENHI Grant Number JP20H00190.
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| 11. |
Ryuji Okazaki, Moeka Harada, Kasumi Yogata, In-situ K-Ar dating of rock samples by a combination of laser-induced breakdown spectroscopy (LIBS) and noble-gas mass spectrometry, 82nd Annual Meetings of the Meteoritical Society, 2019.07. |
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Yuichiro Cho, Shingo Kameda, Yayoi N. Miura, Yoshifumi Saito, Shoichiro Yokota, Satoshi Kasahara, Ryuji Okazaki, others, An In-situ Dating Instrument Package for a Future Mars Rover Mission, 30th International Symposium on Space Technology and Science, 2016.07. |
| 13. |
Yuichiro Cho, M. Horiuchi, K. Shibasaki, S. Kameda, K. Wada, T. Nakamura, T. Mikouchi, Y. Miura, Ryuji Okazaki, others, A laser-induced breakdown spectroscopy instrument for elemental analyses on Phobos, Phobos, Deimos, and Mars Workshop, 2016.02. |
| 14. |
Ryuji Okazaki, A fine-grained polycrustalline micrometeorite: An asteroidal dust particle with a unique mineralogy, The 76th Annual Meeting of the Meteoritical Society.. |
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Nagao, K., Okazaki Ryuji, Miura, Y., Osawa, T., Gilmour, J. D., Nishimura, Y., Noble Gas Analysis of Two Hayabusa Samples as the First International A/O Investigation: A Progress Report , The 44th Lunar and Planetary Science Conference, 2013.03. |
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Yada, T., Abe, M., Okada, T., Uesugi, M., Karouji, Y., Ishibashi, Y., Yakame, S., Shirai, K., Nakamura, T., Noguchi, T., Okazaki Ryuji, Fujimoto, M., Yoshikawa, M., Mineral Ratios of Itokawa Samples — Difference Between Two Rooms of a Hayabusa Sample Catcher, The 44th Lunar and Planetary Science Conference, 2013.03. |
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Tachibana, S., Sawada, H., Okazaki Ryuji, Takano, Y., Okamoto, C., Yano, H., Hayabusa-2 Sampler Team., Hayabusa-2 Sampler Team. The Sampling System of Hayabusa-2: Improvements from the Hayabusa Sampler, The 44th Lunar and Planetary Science Conference, 2013.03. |
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Yabuta, H., Itoh, S., Noguchi, T., Sakamoto, N., Hashiguchi, M., Abe, K., Tsujimoto, S., Kilcoyne, A. L. D., Okubo, A., Okazaki Ryuji, Tachibana, S., Terada, K., Nakamura, T., Nagahara, H., Coexisting Nitrogen-Rich and Poor Organic Materials in Ultracarbonaceous Antarctic Micrometeorite, The 75th Annual Meeting of the Meteoritical Society., 2012.08. |
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Yada, T., Abe, M., Okada, T., Uesugi, M., Karouji, Y., Ishibashi, Y., Yakame, S., Shirai, K.,, Nakamura, T., Noguchi, T., Okazaki Ryuji, Fujimura, A., A Mineral Ratio of Itokawa Particles Recovered from the Hayabusa Sample Catcher , The 75th Annual Meeting of the Meteoritical Society., 2012.08. |
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Yabuta, H, Noguchi, T., Itoh, S., Sakamoto, N., Hashiguchi, M., Abe, K., Tsujimoto, S., Kilcoyne, A. L. D., Okubo, A., Okazaki Ryuji, Tachibana, S.,, Nakamura, T.,, Terada, K, Ebihara, M.,, Nagahara, H, Evidence of Minimum Aqueous Alteration in Rock-Ice Body: Update of Organic Chemistry and Mineralogy of Ultracarbonaceous Antarctic Micrometeorite, The 44th Lunar and Planetary Science Conference, 2012.03. |
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Ebihara, M.,, Sekimoto, S., Shirai, N., Tsujimoto, S., Noguchi, T., Nakamura, T.,, Okazaki Ryuji, Itoh, S., Tachibana, S.,, Yabuta, H, Terada, K, Nagahara, H, Chemical Composition of Dust Samples (Micrometeorites) Recovered from Antarctic Snow, The 44th Lunar and Planetary Science Conference, 2012.03. |
| 22. |
Mineralogy and isotope compositions of coarse-grained Antarctic micrometeorites. . |
| 23. |
Mineralogical and stable isotope signatures of El-Quss Abu Said CM2 carbonaceous chondrite: pristine material from outer asteroid belt. . |
| 24. |
Noble-gas and oxygen isotopes and REE abundances in Antarctic micrometeorites. . |
| 25. |
Si and O diffusivity in ringwoodite. . |
| 26. |
Chemical composition and formation process of silica-rich chondrule rims in the Sahara 00182 CR/CV chondrite.. |
| 27. |
Geochemical study on Temagami iron-formations, Canada. . |
