Solidification of liquid core from thermal expansivity measurements on the Fe-Ni-S liquids

• Project/Area Number: 18K03805
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: Okayama University
• Principal Investigator: urakawa Satoru 岡山大学, 自然科学研究科, 教授 (30201958)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Project Status: Completed (Fiscal Year 2020)
• Budget Amount: ¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000); Fiscal Year 2020: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2019: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2018: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
• Keywords: 惑星磁場 / 流体核 / 組成対流 / 断熱温度勾配 / 熱膨張率 / Fe-Ni-S系 / Fe-S系

Outline of Final Research Achievements

Some bodies in the solar system have a magnetic field like the earth, and another bodies once had. The magnetic field of an Earth-like rock body originates from a dynamo driven by thermo-compositional convection of the liquid core. The lifetime of the magnetic field depends on how the compositional convection of the liquid Fe-alloy caused by the cooling of the core works. We have clarified how the compositional convection pattern of the Fe-FeS core changes depending on the chemical composition and pressure. It was found that relatively small bodies such as the Earth’s moon solidify mainly from the top of the liquid core, resulting in compositional convection.

Academic Significance and Societal Importance of the Research Achievements

太陽系の天体の熱的・化学的進化の詳細を理解することは，45億年前の太陽系の誕生から今日までの歴史の解明という地球惑星科学の壮大な目標の重要な部分を占める。天体の磁場はその熱的・化学的現象の結果であり，衛星によって観測される磁場は天体の熱的・化学的進化の記録を残している。天体の磁場の起源である流体コアの組成対流を理解することは，観測された天体の磁場からその熱的・化学的進化を読み解く鍵を与える。

Research Products

• [Journal Article] Pressure and composition effects on sound velocity and density of core-forming liquids: Implication to core compositions of terrestrial planets (2019)
  • Author(s): H. Terasaki, A. Rivoldini, Y. Shimoyama, K. Nishida, S. Urakawa, M. Maki, F. Kurokawa, Y. Takubo, Y. Shibazaki, T. Sakamaki, A. Machida, Y. Higo, K. Uesugi, A. Takeuchi, T. Watanuki, T. Kondo
  • Journal Title: Journal of Geophysical Research Volume: 124 Issue: 8 Pages: 2272-2293
  • DOI: 10.1029/2019je005936
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Sound velocity and density of liquid Ni68S32 under pressure using ultrasonic and X-ray absorption with tomography methods (2019)
  • Author(s): Terasaki, H., Nishida, K., Urakawa, S., Takubo, Y., Ku51bara, S., Shimoyama, Y., Uesugi, K., Kono, Y., Takeuchi, A., Suzuki, Y., Higo, Y. and Kondo, T.
  • Journal Title: Comptes Rendus Geoscience Volume: 351 Issue: 2-3 Pages: 163-170
  • DOI: 10.1016/j.crte.2018.04.005
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Phase relationships of the system Fe-Ni-S and structure of the high-pressure phase of (Fe 1-x Ni x ) 3 S 2 (2018)
  • Author(s): Urakawa Satoru、Kamuro Ryota、Suzuki Akio、Kikegawa Takumi
  • Journal Title: Physics of the Earth and Planetary Interior Volume: 277 Pages: 30-37
  • DOI: 10.1016/j.pepi.2018.01.007
  • Peer Reviewed
• [Presentation] Bottom-up solidification versus top-down solidification of the liquid core of the relatively small planetary bodies (2019)
  • Author(s): 浦川 啓，寺崎 英紀
  • Organizer: 日本地球惑星科学連合2019年大会
• [Presentation] Fe-Sコアの固化モードと組成対流 (2019)
  • Author(s): 浦川 啓，寺崎 英紀
  • Organizer: 鉱物科学会2019年年会
• [Presentation] 高圧下におけるFe-Ni-S液体のモル体積の熱力学解析 (2019)
  • Author(s): 浦川 啓
  • Organizer: 第60回高圧討論会
• [Presentation] Mercury's and Mars' core composition estimated from elastic properties of liquid iron alloys (2018)
  • Author(s): H. Terasaki, M. Maki, Y. Shimoyama, K. Nishida, S. Urakawa, Y. Takubo, Y. Shibazaki, T. Sakamaki, Y. Higo, A. Machida, T. Kondo
  • Organizer: European Geosciences Union General Assembly 2018
  • Int'l Joint Research
• [Presentation] Core composition of Mercury estimated from elastic properties of liquid Fe-Ni-alloy (2018)
  • Author(s): 寺崎英紀，Rivoldini Attilio，下山裕太，西田圭佑，浦川 啓，黒川冬華，田窪勇作，柴崎裕樹，坂巻竜也，町田晃彦，肥後祐司，近藤 忠
  • Organizer: 日本地球惑星科学連合2018年大会
• [Presentation] Density of the Fe70S30 liquid at high pressure: constraints from the Clapeyron-Clausius relation (2018)
  • Author(s): 浦川 啓，鈴木昭夫
  • Organizer: 日本地球惑星科学連合2018年大会
• [Presentation] 高圧下におけるFe-FeS系のイオウに富む領域の融解関係 (2018)
  • Author(s): 田中翔太，浦川 啓
  • Organizer: 第59回高圧討論会
• [Presentation] Ni-Sメルトの密度と熱膨張率 (2018)
  • Author(s): 浦川 啓，寺崎英紀，田窪勇作，長谷川巧，町田晃彦
  • Organizer: 第59回高圧討論会