Zhang Yun, Michel Patrick, Barnouin Olivier S, Roberts James H, Daly Michael G, Ballouz Ronald-L, Walsh Kevin J, Richardson Derek C, Hartzell Christine M, Lauretta Dante S
Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France.
Department of Aerospace Engineering, University of Maryland, College Park, MD, USA.
Nat Commun. 2022 Aug 6;13(1):4589. doi: 10.1038/s41467-022-32288-y.
Asteroid interiors play a key role in our understanding of asteroid formation and evolution. As no direct interior probing has been done yet, characterisation of asteroids' interiors relies on interpretations of external properties. Here we show, by numerical simulations, that the top-shaped rubble-pile asteroid (101955) Bennu's geophysical response to spinup is highly sensitive to its material strength. This allows us to infer Bennu's interior properties and provide general implications for top-shaped rubble piles' structural evolution. We find that low-cohesion (≲0.78 Pa at surface and ≲1.3 Pa inside) and low-friction (friction angle ≲ 35) structures with several high-cohesion internal zones can consistently account for all the known geophysical characteristics of Bennu and explain the absence of moons. Furthermore, we reveal the underlying mechanisms that lead to different failure behaviours and identify the reconfiguration pathways of top-shaped asteroids as functions of their structural properties that either facilitate or prevent the formation of moons.
小行星内部结构在我们理解小行星的形成与演化过程中起着关键作用。由于尚未进行直接的内部探测，小行星内部结构的特征描述依赖于对其外部特性的解读。在此，我们通过数值模拟表明，顶部呈穹顶状的碎石堆小行星（101955）贝努对加速自转的地球物理响应高度依赖于其物质强度。这使我们能够推断贝努的内部特性，并为顶部呈穹顶状的碎石堆的结构演化提供一般性启示。我们发现，具有多个高内聚力区域的低内聚力（表面约≲0.78帕，内部约≲1.3帕）和低摩擦力（摩擦角≲35°）结构能够始终如一地解释贝努所有已知的地球物理特征，并解释其卫星缺失的原因。此外，我们揭示了导致不同破坏行为的潜在机制，并确定了顶部呈穹顶状小行星的重新配置路径，这些路径是其结构特性的函数，而这些结构特性要么促进要么阻碍卫星的形成。
