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<p>Small celestial bodies provide key insights into the formation and evolution of the Solar System, as their internal structures retain records of the early planetary environment. However, direct measurements of their gravity fields are rare, limiting our understanding of their internal composition. Here we report the gravity field of asteroid (162173) Ryugu from Hayabusa2 laser altimetry and image landmark tracking data. By comparing the estimated gravity field with a constant-density gravity model, we reveal a distinct west–east dichotomy, characterized by significant surface gravity anomalies concentrated in the western hemisphere. We interpret these signals as evidence for shallow subsurface density variations plausibly arising from heterogeneous reaccumulation of parent-body fragments and/or asymmetric alteration by spin-driven surface processes. Comparison with asteroid (101955) Bennu suggests that these two rubble-pile bodies may have experienced divergent evolutionary pathways, leading to their heterogeneous density patterns. Our findings revealed that seemingly similar rubble-pile asteroids can have distinct internal structures shaped by their specific dynamical histories, providing new insights for understanding their diversity and informing future exploration missions.</p>

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The shallow subsurface heterogeneities of asteroid Ryugu revealed by its gravity field

  • 期刊论文

  • 发表日期：

    2026年6月30日

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  • Wutong Gao,
  • Jianguo Yan,
  • Jian-Yang Li,
  • Denggao Qiu,
  • Mohamed Ramy El-Maarry,
  • Sho Sasaki,
  • Jean-Pierre Barriot

摘要

Small celestial bodies provide key insights into the formation and evolution of the Solar System, as their internal structures retain records of the early planetary environment. However, direct measurements of their gravity fields are rare, limiting our understanding of their internal composition. Here we report the gravity field of asteroid (162173) Ryugu from Hayabusa2 laser altimetry and image landmark tracking data. By comparing the estimated gravity field with a constant-density gravity model, we reveal a distinct west–east dichotomy, characterized by significant surface gravity anomalies concentrated in the western hemisphere. We interpret these signals as evidence for shallow subsurface density variations plausibly arising from heterogeneous reaccumulation of parent-body fragments and/or asymmetric alteration by spin-driven surface processes. Comparison with asteroid (101955) Bennu suggests that these two rubble-pile bodies may have experienced divergent evolutionary pathways, leading to their heterogeneous density patterns. Our findings revealed that seemingly similar rubble-pile asteroids can have distinct internal structures shaped by their specific dynamical histories, providing new insights for understanding their diversity and informing future exploration missions.