Chemical and isotopic analyses of asteroid samples returned by Hayabusa2 mission

• Project Area: Aqua planetology
• Project/Area Number: 20H04609
• Research Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
• Allocation Type: Single-year Grants
• Review Section: Science and Engineering
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: 横山 哲也 東京工業大学, 理学院, 教授 (00467028)
• Project Period (FY): 2020-04-01 – 2022-03-31
• Project Status: Completed (Fiscal Year 2021)
• Budget Amount: ¥13,000,000 (Direct Cost: ¥10,000,000、Indirect Cost: ¥3,000,000); Fiscal Year 2021: ¥6,500,000 (Direct Cost: ¥5,000,000、Indirect Cost: ¥1,500,000); Fiscal Year 2020: ¥6,500,000 (Direct Cost: ¥5,000,000、Indirect Cost: ¥1,500,000)
• Keywords: リュウグウ / はやぶさ2 / 同位体比 / 微量元素存在度 / 隕石 / CIコンドライト / 初期分析 / 同位体 / 微量元素

Outline of Research at the Start

探査機はやぶさ2は、水と有機物を含むC型小惑星リュウグウからのサンプルリターンを行う。これまで2度のタッチダウンを行い、異なる地点からの試料採取に成功した。目標天体から汚染なく採取した試料の化学分析は、地球や生命の起源に関する新しい発見をもたらすだろう。本研究の最終目標は、湿式分析による少量地球外試料の微量元素濃度・同位体測定技術を開発し、実際にリュウグウ試料の測定を行うことである。

Outline of Annual Research Achievements

2021年6月より、リュウグウの初期分析が始まった。研究代表者は初期分析化学班の副リーダーとして、リュウグウ試料および炭素質コンドライトの化学分析および同位体分析を実施した。初期分析化学チームにはリュウグウの集合体試料、約30mgが2点が配分された。これら試料について、XRF分析を行って主成分組成を決定した後、酸で分解し、四重極型ICP-MS（X-series2）を用いて54種類の元素存在度を測定した。その結果、リュウグウはCIコンドライトと似た化学組成を持つことが分かった。
更に、東工大に設置した専用のクリーンベンチで、溶解したリュウグウ試料から約20種類の元素を分離抽出した。その際、研究代表者が開発したマルチ元素分離技術を適用した。分離した元素のうち、Crについては東工大の表面電離型質量分析計を用いて精密同位体測定をおこなった。また、Ti同位体の分析を東大のマルチコレクター型ICP質量分析計を用いて行った。その結果、リュウグウのCr-Ti同位体組成はCIコンドライトに近い値となり、XRFやICP-MSを用いて得られた化学組成と矛盾しない結果となった。
2022年2月に導入されたトリプル四重極型ICP-MS（iCAP-TQ）を用いて、隕石試料ならびにリュウグウの元素存在度分析の開発を開始した。特に、消滅核種53Mnを用いた53Mn-53Cr年代測定法において必要となる55Mn/52Cr比を精密に測定する手法の開発を行った。様々な測定モードを試した結果、ガス反応セルを用いないSQ-non gas modeでは分子イオンの干渉により、正しい結果が得られないことが判明した。一方、Heガスを用いたKEDモードで干渉分子イオンを軽減させると、最も高精度・高確度なMn/Cr比を与えることが分かった。

Research Progress Status

令和3年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和3年度が最終年度であるため、記入しない。

Research Products

• [Int'l Joint Research] シカゴ大学/カーネギー研究所/メリーランド大学(米国)
• [Int'l Joint Research] パリシテ大学(フランス)
• [Int'l Joint Research] スイス連邦工科大学チューリッ ヒ校(スイス)
• [Int'l Joint Research] コペンハーゲン大学(デンマーク)
• [Int'l Joint Research] ミュンスター大学(ドイツ)
• [Journal Article] Chemical and Isotopic Evaluation of a Microsampling Method using Laser Ablation and Membrane Filter (2022)
  • Author(s): Masuda Yuki、Yokoyama Tetsuya、Okabayashi Satoki、Ishikawa Akira、Iwamori Hikaru
  • Journal Title: Geostandards and Geoanalytical Research Volume: in press Issue: 2 Pages: 205-222
  • DOI: 10.1111/ggr.12426
  • Peer Reviewed
• [Journal Article] Geochemical constraints on the formation of chondrules: Implication from Os and Fe isotopes and HSE abundances in metals from CR chondrites (2022)
  • Author(s): Nakanishi Nao、Yokoyama Tetsuya、Okabayashi Satoki、Iwamori Hikaru、Hirata Takafumi
  • Journal Title: Geochimica et Cosmochimica Acta Volume: 319 Pages: 254-270
  • DOI: 10.1016/j.gca.2021.11.009
  • Peer Reviewed / Open Access
• [Journal Article] EXAFS Determination of Clay Minerals in Martian Meteorite Allan Hills 84001 and Its Implication for the Noachian Aqueous Environment (2021)
  • Author(s): Nakada Ryoichi、Tanabe Gaku、Kajitani Iori、Usui Tomohiro、Shidare Masashi、Yokoyama Tetsuya
  • Journal Title: Minerals Volume: 11 Issue: 2 Pages: 176-176
  • DOI: 10.3390/min11020176
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Nucleosynthesis: The Where and How (2021)
  • Author(s): Yokoyama Tetsuya、Tsujimoto Takuji
  • Journal Title: Encyclopedia of Geology 2nd Edition Volume: 5 Pages: 1-19
  • DOI: 10.1016/b978-0-08-102908-4.00121-1
  • ISBN: 9780081029091
  • Peer Reviewed
• [Journal Article] Problem of Iron Isotope Composition of the Earth and Moon. Data on δ57Fe of Luna 16, Luna 20, and Luna 24 Lunar Soil Samples (Report on the XXII Symposium on the Geochemistry of Stable Isotopes, Moscow, October 29?31, 2019) (2020)
  • Author(s): Galimov E. M.、Okabayashi S.、Yokoyama T.、Hirata T.、Terakado K.
  • Journal Title: Geochemistry International Volume: 58 Issue: 11 Pages: 1193-1198
  • DOI: 10.1134/s0016702920110063
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Compositional heterogeneity of Archean mantle estimated from Sr and Nd isotopic systematics of basaltic rocks from North Pole, Australia, and the Isua supracrustal belt, Greenland (2020)
  • Author(s): Nakamura Hitomi、Sano Ayane、Kagami Saya、Yokoyama Tetsuya、Ishikawa Akira、Komiya Tsuyoshi、Iwamori Hikaru
  • Journal Title: Precambrian Research Volume: 347 Pages: 105803-105803
  • DOI: 10.1016/j.precamres.2020.105803
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] A new concept for the genesis of felsic magma: the separation of slab-derived supercritical liquid (2020)
  • Author(s): Taniuchi Hajime、Kuritani Takeshi、Yokoyama Tetsuya、Nakamura Eizo、Nakagawa Mitsuhiro
  • Journal Title: Scientific Reports Volume: 10 Issue: 1 Pages: 1-9
  • DOI: 10.1038/s41598-020-65641-6
  • Peer Reviewed / Open Access
• [Journal Article] Magma plumbing system for the Millennium Eruption at Changbaishan volcano, China: Constraints from whole-rock U?Th disequilibrium (2020)
  • Author(s): Kuritani Takeshi、Nakagawa Mitsuhiro、Nishimoto Jumpei、Yokoyama Tetsuya、Miyamoto Tsuyoshi
  • Journal Title: Lithos Volume: 366-367 Pages: 105564-105564
  • DOI: 10.1016/j.lithos.2020.105564
  • Peer Reviewed
• [Presentation] Multi-isotopic analyses of bulk Ryugu samples returned by the Hayabusa2 mission (2022)
  • Author(s): Yokoyama, T., et al.
  • Organizer: Lunar and Planetary Science Conference, The Woodlands, USA (hybrid)
  • Int'l Joint Research
• [Presentation] Chemical and isotopic characterization of asteroid Ryugu. (2022)
  • Author(s): Yurimoto, H., Yokoyama, T., et al.
  • Organizer: Lunar and Planetary Science Conference, The Woodlands, USA (hybrid)
  • Int'l Joint Research
• [Presentation] The oxygen isotopic composition of samples returned from asteroid Ryugu: Evidence for similarity to CI chondrites. (2022)
  • Author(s): Young, E.D., Tang, H., Tafla, L., Pack, A., Rocco, T.Di, Yurimoto, H., Yokoyama, T., et al.
  • Organizer: Lunar and Planetary Science Conference, The Woodlands, USA (hybrid)
  • Int'l Joint Research
• [Presentation] In-situ oxygen and manganese-chromium isotope studies of Ryugu: Implications to temperature and timing of aqueous activity. (2022)
  • Author(s): Nagashima, K., Yokoyama, T., et al.
  • Organizer: Lunar and Planetary Science Conference, The Woodlands, USA (hybrid)
  • Int'l Joint Research
• [Presentation] Sampling mass and chemical heterogeneities among Ryugu samples returned by the Hayabusa2 mission. (2022)
  • Author(s): Dauphas, N., Yokoyama, T., et al.
  • Organizer: Lunar and Planetary Science Conference, The Woodlands, USA (hybrid)
  • Int'l Joint Research
• [Presentation] Speciation of sulfur in carbonates in a 4.1-billion-year-old Martian meteorite. (2022)
  • Author(s): Kajitani, I, Nakada, R., Koike, M., Tanabe, G., Usui, T., Marsuura, R., Fukushi, K., Kurokawa, H., Yokoyama, T.
  • Organizer: Lunar and Planetary Science Conference, The Woodlands, USA (hybrid)
  • Int'l Joint Research
• [Presentation] Origin of nucleosynthetic Sr isotope anomalies in fine grained calcium and aluminum-rich inclusions from Allende. (2022)
  • Author(s): Masuda, Y., Yokoyama, T.
  • Organizer: Lunar and Planetary Science Conference, The Woodlands, USA (hybrid)
  • Int'l Joint Research
• [Presentation] Progress of chemical characterization of asteroid Ryugu samples. (2021)
  • Author(s): Yurimoto, H., Yokoyama, T., et al.
  • Organizer: Hayabusa Symposium 2021, Virtual
  • Int'l Joint Research
• [Presentation] Sulfur species in carbonates of a 4.1-billion-year old Martian meteorite constraining conditions of water on ancient Mars (2020)
  • Author(s): Kajitani, I., Nakada, R., Koike, M., Tanabe, G., Usui, T., Matsu'ura, F., Fukushi, K., Yokoyama, T.
  • Organizer: JpGU-AGU Joint meeting 2020, On-line
• [Presentation] Small-scale isotopic analysis of geological materials using the Laser Ablation with Filter (LAF) sampling method (2020)
  • Author(s): Masuda, Y., Yokoyama, T., Okabayashi, S., Ishikawa, A.
  • Organizer: JpGU-AGU Joint meeting 2020, On-line
• [Presentation] Highly siderophile element mobility during serpentinization of forearc mantle peridotite (2020)
  • Author(s): Nakamura, N., Ishikawa, A., Yokoyama, T.
  • Organizer: JpGU-AGU Joint meeting 2020, On-line
• [Presentation] Highly siderophile geochemistry of komatiites from Pilbara Craton, Western Australia (2020)
  • Author(s): Nakano. S., Ishikawa, A., Ueno, Y., Yokoyama, T.
  • Organizer: JpGU-AGU Joint meeting 2020, On-line
• [Presentation] 神津島流紋岩及び玄武岩質捕獲岩の地球化学的研究 (2020)
  • Author(s): 田村達也、横山哲也、石川晃
  • Organizer: JpGU-AGU Joint meeting 2020, On-line
• [Presentation] Origin and evolution of distinct isotopic variabilities for Sr, Mo, and Nd within inner and outer solar system (2020)
  • Author(s): Yokoyama, T., Fukai, R., Nagai, Y., Hirata, T.
  • Organizer: JpGU-AGU Joint meeting 2020, On-line
• [Presentation] Origin and evolution of distinct isotopic variabilities for Sr, Mo, and Nd within CC and NC reservoirs (Keynote Talk) (2020)
  • Author(s): Yokoyama, T., Fukai, R., Nagai, Y., Hirata, T.
  • Organizer: Goldschmidt Conference, On-line
  • Int'l Joint Research / Invited
• [Presentation] Origin of Hawaiian mantle xenoliths: fragments of mantle plume? (2020)
  • Author(s): Fujita, R., Ishikawa, A., Yokoyama, T., Garcia, M.O.
  • Organizer: Goldschmidt Conference, On-line
  • Int'l Joint Research
• [Presentation] Assessment of the effect of mass-dependent fractionation on 142Nd compositions in Archean rocks (2020)
  • Author(s): Fukai, R., Asanuma, H., Komiya, T., Yokoyama, T., Hirata, T.
  • Organizer: Goldschmidt Conference, On-line
  • Int'l Joint Research
• [Presentation] Lead Isotope Analysis for Picogram Size Samples by TE-DS-TIMS using Amplifier equipped with 10^13 Ohm Resistor (2020)
  • Author(s): Fukami, Y., Tobita, M., Yokoyama, T., Suzuki, K.
  • Organizer: Goldschmidt Conference, On-line
  • Int'l Joint Research
• [Presentation] No impact signatures in Earth’s oldest rocks from Acasta Gneiss Complex, Canada (2020)
  • Author(s): Ishikawa, A., Koshida, K., Suzuki, K., Yokoyama, T., Komiya, T.
  • Organizer: Goldschmidt Conference, On-line
  • Int'l Joint Research
• [Presentation] Development of Laser Ablation with Filter (LAF) sampling method for micro-scale isotopic analysis of geologic materials (2020)
  • Author(s): Masuda, Y., Yokoyama, T., Okabayashi, S., Ishikawa, A.
  • Organizer: Goldschmidt Conference, On-line
  • Int'l Joint Research
• [Presentation] 10＾13Ω抵抗付増幅器を使用したTE-DS-TIMSによる極微量鉛同位体分析における時定数補正について (2020)
  • Author(s): 深海雄介、飛田南斗、横山哲也、鈴木勝彦
  • Organizer: 日本地球化学会年会、オンライン
• [Presentation] 隕石の重元素同位体異常にまつわる最近の話題 (2020)
  • Author(s): 横山哲也
  • Organizer: 研究会「星の錬金術から銀河考古学へ」 、オンライン
  • Invited
• [Presentation] Recent progress in the application of nucleosynthetic isotope anomalies in meteorites (2020)
  • Author(s): Yokoyama, T.
  • Organizer: ISAS Colloquium, on-line
  • Invited