Numerical simulations of asteroid deformation due to rapid rotation and implication for internal properties of asteroids

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K14536
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17010:Space and planetary sciences-related
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Sugiura Keisuke 東京工業大学, 地球生命研究所, JSPS特別研究員 (70846344)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 小惑星リュウグウ / そろばん珠型 / 高速自転変形 / 数値シミュレーション

Outline of Final Research Achievements

The asteroid Ryugu visited by JAXA's spacecraft Hayabusa 2 has a diamond-like top shape. Many top-shaped asteroids have rapid rotation, so that top shapes are considered to be formed through deformation due to rapid rotation. We performed numerical simulations to investigate conditions required for top shape formation. As a result, we found that top shape formation needs high effective friction angles > 70 degrees and fast spinup timescales < several days. We also found that fragments ejected at top shape formation eventually accumulate into satellites, which suggests that top-shaped asteroids are likely to have satellites.

Free Research Field

太陽系形成論

Academic Significance and Societal Importance of the Research Achievements

本研究では小惑星リュウグウのようなそろばん珠形状の形成には70度程度以上の高い実効的摩擦角が必要なことを明らかにした。1 kmサイズの小惑星がこのような高い実効的摩擦角を獲得するためには、数100Pa程度の付着力が必要である。そろばん珠形状をした小惑星は多く見つかっていることから、数100Pa程度の付着力は小惑星の内部物性として普遍的に存在していることが示唆される。特に1 km程度以下の小天体の衝突進化にはこの付着力が大きな影響を及ぼすため、本研究は惑星形成論の文脈において付着力の重要性を示したと言える。