不规则形状小行星的旋转引起的破坏
Rotationally induced failure of irregularly shaped asteroids
摘要：
许多小行星是形状不规则的碎石堆。虽然大型小行星的不规则形状可能是碰撞事件造成的，但小型小行星的不规则形状不仅可能是撞击事件造成的，也可能是旋转引起的故障造成的，这是太阳辐射压力等造成的小扭矩的长期后果。更好地理解这种小扭矩引起的形状变形将使我们能够对小行星及其结构的演化过程进行约束。然而，没有定量研究报告提供了小行星的形状和其故障模式之间的关系，由于其快速旋转。在这里，我们使用有限元模型（FEM）技术来分析24个直径小于30 - 40公里的小行星的故障模式和条件，这些小行星是由地面雷达或小行星探测任务以高分辨率观测到的。假设物质分布是均匀的，我们研究这些小行星如何在不同的自旋速率下结构失败。我们的有限元模拟描述了每个不规则形状的小行星在快速旋转的详细变形模式。失败的区域取决于原始形状。球形物体从内部发生结构失效，而细长物体在垂直于其结构中间最小转动惯量轴的平面上发生结构失效。接触二元物体在其最敏感的截面上具有结构失效。我们进一步调查，如果我们的有限元分析是一致的，从理论上探讨了一个均匀旋转的三轴椭球体的早期作品。结果表明，全球形状的变化可能会显着改变小行星的故障条件。我们的工作表明，考虑小行星的实际形状以详细探索其故障模式至关重要。
英文摘要：
Many asteroids are rubble piles with irregular shapes. While the irregular shapes of large asteroids may be attributed to collisional events, those of small asteroids may result from not only impact events but also rotationally induced failure, a long-term consequence of small torques caused by, for example, solar radiation pressure. A better understanding of shape deformation induced by such small torques will allow us to give constraints on the evolution process of an asteroid and its structure. However, no quantitative study has been reported to provide the relationship between an asteroid's shape and its failure mode due to its fast rotation. Here, we use a finite element model (FEM) technique to analyze the failure modes and conditions of 24 asteroids with diameters less than 30 - 40 km, which were observed at high resolution by ground radar or asteroid exploration missions. Assuming that the material distribution is uniform, we investigate how these asteroids fail structurally at different spin rates. Our FEM simulations describe the detailed deformation mode of each irregularly shaped asteroid at fast spin. The failed regions depend on the original shape. Spheroidal objects structurally fail from the interior, while elongated objects experience structural failure on planes perpendicular to the minimum moment of inertia axes in the middle of their structure. Contact binary objects have structural failure across their most sensitive cross sections. We further investigate if our FEM analysis is consistent with earlier works that theoretically explored a uniformly rotating triaxial ellipsoid. The results show that global shape variations may significantly change the failure condition of an asteroid. Our work suggests that it is critical to take into account the actual shapes of asteroids to explore their failure modes in detail.
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