論文

査読有り
2021年9月

SPH simulations for shape deformation of rubble-pile asteroids through spinup: The challenge for making top-shaped asteroids Ryugu and Bennu

ICARUS
  • Keisuke Sugiura
  • ,
  • Hiroshi Kobayashi
  • ,
  • Sei-ichiro Watanabe
  • ,
  • Hidenori Genda
  • ,
  • Ryuki Hyodo
  • ,
  • Shu-ichiro Inutsuka

365
記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.1016/j.icarus.2021.114505
出版者・発行元
ACADEMIC PRESS INC ELSEVIER SCIENCE

Asteroid 162173 Ryugu and asteroid 101955 Bennu, which were recently visited by spacecraft Hayabusa2 and OSIRIS-REx, respectively, are spinning top-shaped rubble piles. Other axisymmetric top-shaped near-Earth asteroids have been observed with ground-based radar, most of which rotate near breakup rotation periods of similar to 3 h. This suggests that rotation-induced deformation of asteroids through rotational spinup produces top shapes. Although some previous simulations using the Discrete Element Method showed that spinup of rubble piles may produce oblate top shapes, it is still unclear what kinds of conditions such as friction angles of constituent materials and spinup timescales are required for top-shape formation. Here we show, through Smoothed Particle Hydrodynamics simulations of granular bodies spinning-up at different rates, that the rotation-induced deformation of spherical rubble piles before breakup can be classified into three modes according to the friction angle phi(d) : quasi-static and internal deformation for phi(d) <= 40 degrees, dynamical and internal deformation for 50 degrees <= phi(d) <= 60 degrees , and a set of surface landslides for phi(d) >= 70 degrees. Note that these apparent large values of friction angle can be acceptable if we consider the effect of cohesion among blocks of a rubble pile under weak gravity. Bodies with phi(d) <= 60 degrees evolve into oblate spheroids through internal deformation, but never form pronounced equators defining a top shape. In contrast, bodies with phi(d) >= 70 degrees deform into axisymmetric top shapes through an axisymmetric set of surface landslides if spinup timescales are less than or similar to a few days. In addition, through slow spinups with timescales greater than or similar to 1 month, bodies with phi(d) >= 70 degrees deform into non-axisymmetric shapes via localized sets of landslides. We suggest that rapid spinup mechanisms are preferable for the formation of axisymmetric top shapes.


リンク情報
DOI
https://doi.org/10.1016/j.icarus.2021.114505
Web of Science
https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=JSTA_CEL&SrcApp=J_Gate_JST&DestLinkType=FullRecord&KeyUT=WOS:000659152300015&DestApp=WOS_CPL
ID情報
  • DOI : 10.1016/j.icarus.2021.114505
  • ISSN : 0019-1035
  • eISSN : 1090-2643
  • Web of Science ID : WOS:000659152300015

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