Heavily cratered surfaces on the Moon, Mars, and Mercury show that the terrestrial planets were battered by an intense bombardment during their first billion years or more, but the timing, sources, and dynamical implications of these impacts are controversial. The Late Heavy Bombardment refers to impact events that occurred after stabilization of the planetary lithospheres such that they could be preserved as craters and basins. Lunar melt rocks and meteorite shock ages point toward a discrete episode of elevated impact flux between ∼3.5 and ∼4.0–4.2 Ga, and a relative quiescence between ∼4.0–4.2 and ∼4.4 Ga. Evidence from Precambrian impact spherule layers suggests that a long-lived tail of terrestrial impactors lasted to ∼2.0–2.5 Ga. Dynamical models that include populations residual from primary accretion and destabilized by giant planet migration can potentially account for the available observations, although all have pros and cons. The most parsimonious solution to match constraints is a hybrid mode...

中文翻译：

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后期重炮轰击

月球、火星和水星上的严重坑坑洼洼的表面表明，这些类地行星在最初的十亿年或更长时间里受到了强烈的轰击，但这些撞击的时间、来源和动力影响是有争议的。晚期重轰击是指在行星岩石圈稳定后发生的撞击事件，以便它们可以作为陨石坑和盆地得以保存。月球熔岩和陨石冲击年龄表明，大约 3.5 到 4.0-4.2 Ga 之间的冲击通量升高，以及大约 4.0-4.2 和 4.4 Ga 之间的相对静止。来自前寒武纪撞击球层的证据表明，长期-地球撞击物的存活尾部持续到~2.0-2.5 Ga。包括原始吸积残余人口和巨行星迁移不稳定的动力学模型可能会解释可用的观测结果，尽管所有这些都有利有弊。匹配约束的最简洁的解决方案是混合模式......