arXiv 1909.112702019-09-25astro-ph.EP

快速旋转小行星上的凝聚风化层

Cohesive Regolith on Fast Rotating Asteroids

Paul Sánchez, Daniel J. Scheeres

备注：: Accepted for publication in Icarus
DOI：: 10.1016/j.icarus.2019.113443

摘要：

使用理论和模拟模型研究了一个整体或坚固的小行星表面粘性风化层的迁移。理论和模拟表明，在增加的旋转速率下（例如由于YORP效应），风化层覆盖物优先在身体的某些区域丢失。对于具有很少或没有内聚强度的风化层，在足够高的旋转速率下，从该天体的中纬度发生的滑坡会导致破坏。当风化层的内聚强度增加时，在更大的纬度范围内，由于颗粒（或颗粒的连贯块）的分裂而发生破坏，最终将首先发生在赤道。随着旋转速率进一步增加，故障区域从第一故障点迁移到更高和更低的纬度。最终，失效将包括赤道区域，然而，总是存在一个高纬度区域（在两极周围），该区域不会在任意高的自旋速率下发生失效（除非受到其他现象的干扰）。有了这些结果，一个比例律的推导，可以用来确定是否观察到的小行星可以保留表面风化层颗粒的给定大小。这对解释小行星的光谱观测和大行星上的巨石迁移的影响进行了讨论。

英文摘要：

The migration of cohesive regolith on the surface of an otherwise monolithic or strong asteroid is studied using theoretical and simulation models. The theory and simulations show that under an increasing spin rate (such as due to the YORP effect), the regolith covering is preferentially lost across certain regions of the body. For regolith with little or no cohesive strength, failure occurs by landsliding from the mid latitudes of the body at high enough spin rates. As the cohesive strength of the regolith increases, failure occurs by fission of grains (or coherent chunks of grains) across a greater extent of latitudes and eventually will first occur at the equator. As the spin rate is further increased, failure regions migrate from the first failure point to higher and lower latitudes. Eventually failure will encompass the equatorial region, however there always remains a region of high latitudes (around the poles) that will not undergo failure for arbitrarily high spin rates (unless disturbed by some other phenomenon). With these results a scaling law is derived that can be used to determine whether observed asteroids could retain surface regolith grains of a given size. The implications of this for the interpretation of spectral observations of small asteroids and boulder migration on large asteroids are discussed.

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