We investigate the possibility that the Moon’s formation impact was triggered by an early dynamical instability of the giant planets. We consider the well-studied ‘jumping Jupiter’ hypothesis for the Solar system’s instability, where Jupiter and Saturn’s semimajor axes evolve in step-wise manner from their primordially compact architecture to their present locations. Moreover, we test multiple different configurations for the primordial system of terrestrial planets and the Moon-forming projectile, with particular focus on the almost equal masses impact. We find that the instability/migration of the giant planets excites the orbits of the terrestrial planets through dynamical perturbations, thus allowing collisions between them. About 10 per cent of the simulations lead to a collision with the proto-Earth which resulted in a final configuration of the terrestrial system that reproduces, to some extent, its present architecture. Most of these collisions occur in the hit-and-run domain, but about 15 per cent occur in the partial accretion regime, with the right conditions for a Moon-forming impact. In most of the simulations, there is a delay of more than ∼20 My between the time of the instability and the Moon-forming impact. This supports the occurrence of an early instability (<10 My after dissipation of the gas in the protoplanetary disc), compatible with the time of the Moon-forming impact (30–60 My) inferred from cosmochemical constraints. In general, the final states of the inner Solar system in our simulations show an excess of Angular Momentum Deficit, mostly attributed to the overexcitation of Mercury’s eccentricity and inclination.

中文翻译：

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跳跃的木星能触发月球的形成撞击吗？

我们调查了月球形成撞击是由巨行星的早期动态不稳定性触发的可能性。我们考虑了关于太阳系不稳定性的充分研究的“跳跃木星”假说，其中木星和土星的半长轴从它们最初紧凑的结构逐步演化到它们现在的位置。此外，我们测试了类地行星原始系统和月球形成弹丸的多种不同配置，特别关注质量几乎相等的撞击。我们发现巨行星的不稳定性/迁移通过动力扰动激发了类地行星的轨道，从而允许它们之间发生碰撞。大约 10% 的模拟导致与原始地球的碰撞，从而导致陆地系统的最终配置在某种程度上再现了其当前架构。这些碰撞中的大多数发生在肇事逃逸领域，但大约 15% 发生在部分吸积机制中，具有形成月球的撞击的适当条件。在大多数模拟中，在不稳定时间和月球形成撞击之间存在超过 20 My 的延迟。这支持了早期不稳定性的发生（原行星盘中气体消散后<10 My），与从宇宙化学约束推断的月球形成撞击时间（30-60 My）相一致。一般来说，在我们的模拟中，太阳系内部的最终状态显示出过量的角动量赤字，