碰撞编年史：早期不稳定性背景下彗星和碳质小行星对地球挥发性元素预算的相对贡献
Crash Chronicles: relative contribution from comets and carbonaceous asteroids to Earth's volatile budget in the context of an Early Instability
AI总结：
本研究通过20次高分辨率动力学模拟，发现早期巨行星不稳定性下彗星对地球的晚期撞击贡献增加，可解释地幔与大气Xe同位素差异。
摘要：
近期太阳系形成模型表明，巨行星之间的动力学不稳定性发生在气体盘消散后的前1亿年内，或许早于月球形成撞击。作为直接后果，在地球内部储库与大气储库解耦之前，富含挥发性元素的撞击体可能已对地球进行了轰击。然而，这一时间节点被解释为可能与地球地幔与大气中Xe同位素分布差异相矛盾。本研究旨在评估早期不稳定性对碳质小行星和彗星向地球输送的动力学影响，并探讨其对地球挥发性元素预算的意义。我们进行了20次高分辨率太阳系形成动力学模拟，从气体盘消散时开始，每次模拟初始包含1600颗碳质小行星和10000颗彗星，并考虑了早期巨行星不稳定性带来的动力学扰动。在月球形成撞击之前，彗星与地球的累积碰撞率比碳质小行星低约4个数量级。月球形成撞击之后，这一比率根据各次模拟的动力学不同而降低或升高，且常变化达数个数量级。在我们30%的模拟中，彗星相对贡献有所增加。在这些情况下，鉴于彗星中132Xe的丰度比碳质球粒陨石高3个数量级，来自各源的惰性气体输送量相当。因此，晚期彗星通量相对于碳质小行星的增加，可能为地球地幔与大气之间Xe同位素特征的二分性提供解释。
英文摘要：
Recent models of solar system formation suggest that a dynamical instability among the giant planets happened within the first 100 Myr after disk dispersal, perhaps before the Moon-forming impact. As a direct consequence, a bombardment of volatile-rich impactors may have taken place on Earth before internal and atmospheric reservoirs were decoupled. However, such a timing has been interpreted to potentially be at odds with the disparate inventories of Xe isotopes in Earth's mantle compared to its atmosphere. This study aims to assess the dynamical effects of an Early Instability on the delivery of carbonaceous asteroids and comets to Earth, and address the implications for the Earth's volatile budget. We perform 20 high-resolution dynamical simulations of solar system formation from the time of gas disk dispersal, each starting with 1600 carbonaceous asteroids and 10000 comets, taking into account the dynamical perturbations from an early giant planet instability. Before the Moon-forming impact, the cumulative collision rate of comets with Earth is about 4 orders of magnitude lower than that of carbonaceous asteroids. After the Moon-forming impact, this ratio either decreases or increases, often by orders of magnitude, depending on the dynamics of individual simulations. An increase in the relative contribution of comets happens in 30\% of our simulations. In these cases, the delivery of noble gases from each source is comparable, given that the abundance of 132Xe is 3 orders of magnitude greater in comets than in carbonaceous chondrites. The increase in cometary flux relative to carbonaceous asteroids at late times may thus offer an explanation for the Xe signature dichotomy between the Earth's mantle and atmosphere.
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