标题： 小型撞击坑的平衡大小-频率分布揭示了远距离溅射物对月球地貌形态的影响 显示英文标题

标题： The equilibrium size-frequency distribution of small craters reveals the effects of distal ejecta on lunar landscape morphology

摘要： 月海中的小陨石坑被观察到处于一种平衡状态，其中新陨石坑的产生率平均而言等于旧陨石坑的破坏率。 几十年来对多个月球地形的陨石坑计数始终表明，半径大于r的小陨石坑每单位面积的平衡累积大小-频率分布（SFD）与r^(-2)成正比，并且总陨石坑密度为所谓的几何饱和度的百分之几，这是圆形特征的最大理论填充密度。 虽然长期以来人们已经知道这些小陨石坑的主要破坏机制是稳定的扩散性退化，但对于决定米到千米尺度月表特征退化率的过程却很少有定量约束。 在这里，我们将解析模型与一个名为“陨石坑地形演化模型”的蒙特卡洛地貌演化代码相结合，以限制哪些过程控制了小陨石坑观测到的平衡大小-频率分布。 我们发现，由小的远端溅射碎片引起的撞击，这些碎片分布在空间异质的射线中，是对控制小陨石坑平衡SFD的扩散性退化的主要贡献者。 其他退化或陨石坑清除机制，如“饼干切割”、溅射埋藏、地震摇晃和微流星体轰击，在米级及更大尺度上对月海的地貌扩散性退化可能几乎没有贡献。 显示英文摘要

摘要： Small craters of the lunar maria are observed to be in a state of equilibrium, in which the rate of production of new craters is, on average, equal to the rate of destruction of old craters. Crater counts of multiple lunar terrains over decades consistently show that the equilibrium cumulative size-frequency distribution (SFD) per unit area of small craters of radius >r is proportional r^(-2), and that the total crater density is a few percent of so-called geometric saturation, which is the maximum theoretical packing density of circular features. While it has long been known that the primary crater destruction mechanism for these small craters is steady diffusive degradation, there are few quantitative constraints on the processes that determine the degradation rate of meter to kilometer scale lunar surface features. Here we combine analytical modeling with a Monte Carlo landscape evolution code known as the Cratered Terrain Evolution Model to place constraints on which processes control the observed equilibrium size-frequency distribution for small craters. We find that the impacts by small distal ejecta fragments, distributed in spatially heterogeneous rays, is the largest contributor to the diffusive degradation which controls the equilibrium SFD of small craters. Other degradation or crater removal mechanisms, such cookie cutting, ejecta burial, seismic shaking, and micrometeoroid bombardment, likely contribute very little to the diffusive topographic degradation of the lunar maria at the meter scale and larger.