Timing of dissipation of the solar nebula gas and accretion ages of cometary dustof comets based on the 26Al-26Mg chronometry

• Project/Area Number: 18H01263
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 17010:Space and planetary sciences-related
• Research Institution: Tohoku University
• Principal Investigator: Nakashima Daisuke 東北大学, 理学研究科, 講師 (90734757)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Project Status: Completed (Fiscal Year 2021)
• Budget Amount: ¥8,320,000 (Direct Cost: ¥6,400,000、Indirect Cost: ¥1,920,000); Fiscal Year 2020: ¥2,600,000 (Direct Cost: ¥2,000,000、Indirect Cost: ¥600,000); Fiscal Year 2019: ¥3,120,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥720,000); Fiscal Year 2018: ¥2,600,000 (Direct Cost: ¥2,000,000、Indirect Cost: ¥600,000)
• Keywords: 彗星塵 / 斜長石 / 酸素同位体比 / 26Al-26Mg同位体年代 / 酸素同位体比分析 / 同位体年代 / 彗星 / 原始太陽系ガス円盤 / 斜長石を含む彗星塵 / コンドリュール様彗星塵

Outline of Final Research Achievements

Cometary dust particles were analyzed for oxygen and 26Al-26Mg isotopes to give constraints on accretion ages of comets and timing of dissipation of the solar nebula gas. Oxygen isotope analysis showed that the particles are all cometary in origin. Plagioclase in a cometary dust particle showed no resolvable excess of 26Mg, suggesting crystallization of the cometary plagioclase after decay of 26Al. The cometary plagioclase formed 3.9 Myr after starting of the formation of solar system based on the uncertainty of the initial 26Al/27Al ratio, which is later than that estimated in previous studies (2.6 Myr). It is considered that accretion of comets and dissipation of the solar nebula gas are later than previously though.

Academic Significance and Societal Importance of the Research Achievements

原始太陽系ガス円盤の進化過程の研究は、恒星と周囲のガス円盤の観測や数値計算によって行われている。我々の太陽系の進化過程の理解は、これらの結果からの類推に依るところが大きい。一方で本研究は、彗星塵の物質科学に基づき、原始太陽系ガス円盤の進化過程について直接的な制約を与えたという点で学術的意義がある。

Research Products

• [Int'l Joint Research] NASA-JSC/University of Wisconsin-Madison(米国)
• [Int'l Joint Research] Korean Polar Research Institute(韓国)
• [Int'l Joint Research] ウィスコンシン大学/ローレンス・リバモア国立研究所/アメリカ自然史博物館(米国)
• [Int'l Joint Research] ウィスコンシン大学/ローレンス・リバモア国立研究所/アメリカ自然史博物館(米国)
• [Presentation] Oxygen isotopes in AMMs and IDPs: universality of oxygen isotope systematics of crystalline silicates in comets (2022)
  • Author(s): D. Nakashima, S. Shimizu, R. Oike, K. Fukuda, M. Zhang, N.T. Kita, M.E. Zolensky, J.I. Lee, S. Park, T. Nakamura
  • Organizer: The 53rd Lunar and Planetary Science Conference
  • Int'l Joint Research
• [Presentation] GEMSを産する微隕石と惑星間塵に含まれるコンドルールと難揮発性包有物について (2019)
  • Author(s): 野口高明
  • Organizer: 日本地球惑星連合2019年大会
• [Presentation] Chondrule-like objects and a refractory inclusion in GEMS-bearing Antarctic micrometeorites and interplanetary dust particles (2019)
  • Author(s): Takaaki Noguchi
  • Organizer: 50th Lunar and Planetary Science Conference
  • Int'l Joint Research