Development of a crater scale law on a small body regolith by microgravity experiments

• Project/Area Number: 18K03723
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17010:Space and planetary sciences-related
• Research Institution: Kobe University
• Principal Investigator: Nakamura Akiko 神戸大学, 理学研究科, 准教授 (40260012)
• Co-Investigator(Kenkyū-buntansha): 和田 浩二 千葉工業大学, 惑星探査研究センター, 主席研究員 (10396856) ; 長谷川 直 国立研究開発法人宇宙航空研究開発機構, 宇宙科学研究所, 主任研究開発員 (10399553)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Project Status: Completed (Fiscal Year 2021)
• Budget Amount: ¥4,550,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥1,050,000); Fiscal Year 2020: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000); Fiscal Year 2019: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000); Fiscal Year 2018: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000)
• Keywords: 低重力 / クレーター / レゴリス / 衝突クレーター / 小天体

Outline of Final Research Achievements

We develop a drop tower for the target container of cratering experiment and performed impact cratering experiments under simulated low-gravity conditions. The crater diameters of silica sand targets of several hundred microns in size were larger under low gravity than under 1 G, indicating that the dependence on the gravitational acceleration is consistent with the values shown in previous studies. For the strongly adherent, several tens of microns size particle targets, there was no significant difference in crater diameters under 1 G and under low gravity, i.e., the "inter-particle force dominated regime" in crater formation was confirmed. On the other hand, we measured microscopic particle shape and inter-particle cohesive forces of meteorite powder, which is considered to be equivalent to asteroid regolith, and showed that it is coarser and has smaller cohesive forces than silica sand and other materials used in cratering experiments as simulated regolith.

Academic Significance and Societal Importance of the Research Achievements

はやぶさ２が探査した小惑星リュウグウや、これからMMXによって探査される火星衛星フォボスは、岩塊や砂状のレゴリスで表面が覆われている。これらの天体表層は、地上に比べて数桁も重力加速度が小さい。しかし、微小重力の天体表面ではレゴリス粒子同士の付着性が無視できない可能性がある。本研究は、模擬低重力下でクレーター実験を行うシステムを開発し、クレーターの大きさについてレゴリスの付着性がどのように影響するかを実験的に示した。

Research Products

• [Journal Article] Implications of High Polarization Degree for the Surface State of Ryugu (2021)
  • Author(s): Kuroda D., Geem J., Akitaya H., Jin S., Takahashi J., Takahashi K., Naito H., Makino K., Sekiguchi T., Bach Y. P., Seo J., Sato S., Sasago H., Kawabata K. S., Kawakami A., Tozuka M., Watanabe M., Takagi S., Kuramoto K., Yoshikawa M., Hasegawa S., Ishiguro M.
  • Journal Title: The Astrophysical Journal Letters Volume: 911 Issue: 2 Pages: L24-L24
  • DOI: 10.3847/2041-8213/abee25
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Discovery of Two TNO-like Bodies in the Asteroid Belt (2021)
  • Author(s): Hasegawa Sunao、Marsset Michael、DeMeo Francesca E.、Bus Schelte J.、Geem Jooyeon、Ishiguro Masateru、Im Myungshin、Kuroda Daisuke、Vernazza Pierre
  • Journal Title: The Astrophysical Journal Letters Volume: 916 Issue: 1 Pages: L6-L6
  • DOI: 10.3847/2041-8213/ac0f05
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Resurfacing processes on asteroid (162173) Ryugu caused by an artificial impact of Hayabusa2's Small Carry-on Impactor (2021)
  • Author(s): Honda Rie、Arakawa Masahiko、Shimaki Yuri、Shirai Kei、Yokota Yasuhiro、Kadono Toshihiko、Wada Koji、et al.
  • Journal Title: Icarus Volume: 366 Pages: 114530-114530
  • DOI: 10.1016/j.icarus.2021.114530
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Cohesion of regolith: Measurements of meteorite powders (2021)
  • Author(s): Nagaashi Yuuya、Aoki Takanobu、Nakamura Akiko M.
  • Journal Title: Icarus Volume: 360 Pages: 114357-114357
  • DOI: 10.1016/j.icarus.2021.114357
  • Peer Reviewed
• [Journal Article] An artificial impact on the asteroid 162173 Ryugu formed a crater in the gravity-dominated regime (2020)
  • Author(s): Arakawa, M., Saiki, T., Wada, K., Ogawa, K., Kadono, T., Shirai, K., Sawada, H., Ishibashi, K., Honda, R., Sakatani, N., Iijima, Y., Okamoto, C., Yano, H., Takagi, Y., Hayakawa, M., Michel, P., Jutzi, M., Shimaki, Y., Kimura, S., Mimasu, Y., Toda, T., Imamura, H., Nakazawa, S., Hayakawa, H., Sugita, S., et al.
  • Journal Title: Science Volume: 368 Issue: 6486 Pages: 67-71
  • DOI: 10.1126/science.aaz1701
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Q-type asteroids: Possibility of non-fresh weathered surfaces (2019)
  • Author(s): Hasegawa, S., Hiroi, T., Ohtsuka, K., Ishiguro, M., Kuroda, D., Ito, T., Sasaki, S.
  • Journal Title: Publications of the Astronomical Society of Japan Volume: 71 Issue: 5 Pages: 103-103
  • DOI: 10.1093/pasj/psz088
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Experimental study on gravitational and atmospheric effects on crater size formed by low‐velocity impacts into granular media (2019)
  • Author(s): Kiuchi, M., Nakamura, A. M., Wada, K.
  • Journal Title: Journal of Geophysical Research: Planets Volume: 印刷中 Issue: 5 Pages: 1379-1392
  • DOI: 10.1029/2018je005628
  • Peer Reviewed
• [Journal Article] Laboratory experiments on agglomerationof particles in a granular stream (2018)
  • Author(s): Nagaashi, Y., Omura, T., Kiuchi, M., Nakamura, A. M., Wada, K., Hasegawa, S.
  • Journal Title: Progress in Earth and Planetary Science Volume: 5 Issue: 1 Pages: 52-52
  • DOI: 10.1186/s40645-018-0205-6
  • Peer Reviewed / Open Access
• [Journal Article] Physical properties of near-Earth asteroids with a low delta-v: Survey of target candidates for the Hayabusa2 mission (2018)
  • Author(s): Hasegawa Sunao、他４２名
  • Journal Title: Publications of the Astronomical Society of Japan Volume: 70 Issue: 6 Pages: 114-114
  • DOI: 10.1093/pasj/psy119
  • Peer Reviewed / Int'l Joint Research
• [Presentation] High-velocity impact experiments in reduced gravity: The effect of cohesive strength of particle layers (2021)
  • Author(s): Masato Kiuchi, Takaya Okamoto, Yuuya Nagaashi, Sunao Hasegawa, Akiko Nakamura
  • Organizer: Japan Geoscience Union Meeting 2021, online, May 30 - June 6
  • Int'l Joint Research
• [Presentation] Cohesive force measurements of meteorite powders (2021)
  • Author(s): Nagaashi, Y., Aoki, T., Nakamura, A. M.
  • Organizer: The 52nd Lunar and Planetary Science Conference (LPSC), virtual
  • Int'l Joint Research
• [Presentation] 低重力下での高速度衝突クレーター形成実験 (2021)
  • Author(s): 木内 真人、岡本尚也、長足 友哉、長谷川 直、中村 昭子
  • Organizer: 天体の衝突物理の解明 (XVI)/第12回スペースガード研究会
• [Presentation] Laboratory penetration experiments conducted at low effective gravity II (2020)
  • Author(s): Nakamura, A. M., Nakahata, J., Nagaashi, Y.
  • Organizer: JpGU - AGU joint meeting 2020 virtual
  • Int'l Joint Research
• [Presentation] Experimental study of high-velocity impacts into granular material in reduced gravity (2020)
  • Author(s): Kiuchi, M., Okamoto, T., Hasegawa, S., Nakamura, A. M.
  • Organizer: JpGU - AGU joint meeting 2020 virtual
  • Int'l Joint Research
• [Presentation] 簡易的な落下装置を用いた高速度クレーター形成実験：クレーターサイズの重力依存性 (2020)
  • Author(s): 木内 真人、岡本 尚也、長足 友哉、長谷川 直、中村 昭子
  • Organizer: 日本惑星科学会秋季講演会
• [Presentation] レゴリス粒子の固着力：粒子の形状と塑性変形の効果 (2020)
  • Author(s): 長足 友哉、青木隆修、中村昭子
  • Organizer: 日本惑星科学会秋季講演会
• [Presentation] Experimental study on gravitational effects on crater size formed by low-velocity impacts into granular media (2019)
  • Author(s): Kiuchi, M., Nakamura, A. M., Wada, K.
  • Organizer: JpGU2019, Makuhari Messe, May. 26-30, 2019
  • Int'l Joint Research
• [Presentation] Laboratory impact penetration experiments conducted at simulated reduced gravity (2019)
  • Author(s): Nakamura, A. M., Morizono, K., Nagaashi, Y.
  • Organizer: JpGU2019, Makuhari Messe, May. 26-30, 2019
  • Int'l Joint Research
• [Presentation] 微小重力下での高速度衝突クレーター形成実験 (2019)
  • Author(s): 木内真人, 中村昭子, 岡本尚也
  • Organizer: 令和元年度宇宙科学に関する室内実験シンポジウム, JAXA宇宙科学研究所, 3月2-3日, 2019. (書面発表)
• [Presentation] はやぶさ2 SCIによる小惑星リュウグウ上での衝突実験 (2019)
  • Author(s): 荒川政彦, 佐伯孝尚, 門野敏彦, 高木靖彦, 和田浩二, 他
  • Organizer: 日本惑星科学会2019年度秋季講演会，京都産業大学神山ホール，2019年10月7日-9日
• [Presentation] SCIクレータから放出されたイジェクタ粒子のサイズ推定 (2019)
  • Author(s): 和田浩二, 石橋高, 木村宏, 荒川政彦, 澤田弘崇, 他
  • Organizer: 第15回衝突研究会：天体の衝突物理の解明 (XV) ～小惑星の表層進化～, 千葉工業大学 東京スカイツリータウンキャンパス, 11月27-29日, 2019
• [Presentation] Experimental study of low velocity impact onto granular media under reduced gravities: Effects of density ratio of the projectile to the target (2018)
  • Author(s): Kiuchi, M., Nakamura, A. M., Wada, K.
  • Organizer: JpGU2018 (EE session)
  • Int'l Joint Research
• [Presentation] 小天体レゴリスへのインパクターの貫入深さ (2018)
  • Author(s): 森園佳奈，中村昭子
  • Organizer: 第14回衝突研究会研究集会 天体の衝突物理の解明 (XIV) ～探査機はやぶさの成果と挑戦：初号機から２号機へ～
• [Presentation] 粉体層への低速度衝突で形成されるクレーターサイズの重力依存性 (2018)
  • Author(s): 木内真人，中村昭子，和田浩二
  • Organizer: 第14回衝突研究会研究集会 天体の衝突物理の解明 (XIV) ～探査機はやぶさの成果と挑戦：初号機から２号機へ～