Abstract

We compare the number of lunar craters larger than 15 km across and younger than 1.1 Ga to the estimates of the number of craters that could have been formed for 1.1 Ga if the number of near-Earth objects and their orbital elements during that time were close to the corresponding current values. The comparison was performed for craters over the entire lunar surface and in the region of the Oceanus Procellarum and maria on the near side of the Moon. In these estimates, we used the values of collision probabilities of near-Earth objects with the Moon and the dependences of the crater diameters on the impactor sizes. According to the estimates made by different authors, the number density of known Copernican craters with diameters D ≥ 15 km in mare regions is at least double the corresponding number for the remaining lunar surface. Our estimates do not contradict the growth in the number of near-Earth objects after probable catastrophic fragmentations of large main-belt asteroids, which may have occurred over the recent 300 Ma; however, they do not prove this increase. Particularly, they do not conflict with the inference made by Mazrouei et al. (2019) that 290 Ma ago the frequency of collisions of near-Earth asteroids with the Moon increased by 2.6 times. The number of Copernican lunar craters with diameters not smaller than 15 km is probably higher than that reported by Mazrouei et al. (2019). For a probability of a collision of an Earth-crossing object (ECO) with the Earth in a year equaled to 10^–8 , our estimates of the number of craters agree with the model, according to which the number densities of the 15-km Copernican craters for the whole lunar surface would have been the same as that for mare regions if the data by Losiak et al. (2015) for D < 30 km were as complete as those for D > 30 km. With this collision probability of ECOs with the Earth and for this model, the cratering rate may have been constant over the recent 1.1 Ga.

中文翻译：

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过去十亿年中近地天体的数量和月球坑的形成

摘要

我们将跨度大于15 km且小于1.1 Ga的月球陨石坑的数量与如果在此期间近地天体及其轨道元素的数量接近的情况下可能形成的1.1 Ga陨石坑的数量进行了比较到相应的当前值。对整个月球表面以及月球近侧的海星Procellarum和玛丽亚地区的陨石坑进行了比较。在这些估算中，我们使用了近地物体与月球的碰撞概率值以及陨石坑直径对撞击器尺寸的依赖性。根据不同作者的估计，已知直径为D的哥白尼陨石坑的数量密度在母马地区≥15 km，至少是剩余月球表面对应数量的两倍。我们的估计与在大型主带小行星可能发生灾难性破碎之后发生的近地天体数量的增长没有矛盾，这可能发生在最近的300 Ma。但是，他们没有证明这一增加。特别是，它们与Mazrouei等人的推论没有冲突。（2019）290 Ma之前，近地小行星与月球的碰撞频率增加了2.6倍。直径不小于15 km的哥白尼月球坑的数量可能比Mazrouei等人报道的数量更大。（2019）。一年中跨地球物体（ECO）与地球发生碰撞的可能性等于10 ^–8，我们对陨石坑数量的估计与该模型一致，根据该模型，如果Losiak等人的数据表明，整个月球表面15公里哥白尼陨石坑的密度将与整个母马地区的密度相同。（2015）D <30 km与D  > 30 km一样完整。有了这种ECO与地球的碰撞概率，对于该模型，火山口速率在最近的1.1 Ga上可能是恒定的。