This report summarizes observations of returned Apollo rocks and soils, lunar surface images, orbital observations, and experimental impacts related to the erosion and comminution of rocks exposed at the lunar surface. The objective is to develop rigorous criteria for the recognition of impact processes that assist in distinguishing “impact” from other potential erosional processes, particularly thermal fatigue, which has recently been advocated specifically for asteroids. Impact in rock is a process that is centrally to bilaterally symmetric, resulting in highly crushed, high-albedo, quasicircular depressions surrounded by volumetrically prominent spall zones. Containing central glass-lined pits in many cases, such features provide distinctive evidence of impact that is not duplicated by any other process. Additional evidence of impact can include radial fracture systems in the target that emanate from the impact point and clusters of fragments that attest to the lateral acceleration and displacement of each one. It is also important to note that impact produces a wide variety of fragment shapes that might totally overlap with those produced by thermal fatigue; we consider fragment shape to be an unreliable criterion for either process. The stochastic nature of the impact process will result in exponential survival times of surface rocks; that is, rock destruction initially is relatively efficient, but it is followed by ever increasing surface times for the last rock remnants. Thermal fatigue, however, is essentially a thermal-equilibrium process. The corresponding distribution of survival times should be much more peaked in comparison, presumably Gaussian, and diagnostically different from that due to impact. Given the abundance of evidence that has been gleaned from returned Apollo rocks and soils, it is surprising how little has been learned about the impact process from the photography of rocks and boulders taken by the astronauts on the lunar surface. This suggests that it will require rocks and soils returned from asteroids to evaluate the relative roles of thermal versus impact-triggered rock erosion, particularly when both processes are likely to be operating.

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冲击过程对月球表面岩石的侵蚀：综合

这份报告总结了对阿波罗返回的岩石和土壤的观察、月球表面图像、轨道观察以及与暴露在月球表面的岩石的侵蚀和粉碎有关的实验影响。目标是制定严格的标准来识别撞击过程，以帮助将“撞击”与其他潜在的侵蚀过程区分开来，特别是最近专门针对小行星提出的热疲劳。岩石撞击是一个从中心到两侧对称的过程，导致高度破碎、高反照率、准圆形凹陷，周围环绕着体积突出的剥落带。在许多情况下，这些特征包含中央搪玻璃坑，提供了任何其他工艺无法复制的独特影响证据。撞击的其他证据包括目标中从撞击点发出的径向断裂系统，以及证明每个碎片的横向加速度和位移的碎片群。同样重要的是要注意，撞击会产生各种各样的碎片形状，这些碎片形状可能与热疲劳产生的碎片形状完全重叠；我们认为片段形状对于任何一个过程都是不可靠的标准。冲击过程的随机性将导致地表岩石的存活时间呈指数增长；也就是说，岩石破坏最初是相对有效的，但随后最后的岩石残余物的表面时间不断增加。然而，热疲劳本质上是一个热平衡过程。相对应的生存时间分布应该是尖峰多了，大概是高斯分布，并且由于影响而在诊断上与它不同。鉴于从返回的阿波罗岩石和土壤中收集到的大量证据，令人惊讶的是，从宇航员在月球表面拍摄的岩石和巨石的照片中，我们对撞击过程的了解却如此之少。这表明它将需要从小行星返回的岩石和土壤来评估热和撞击引发的岩石侵蚀的相对作用，特别是当这两个过程都可能发生时。