Vertical angular momentum constraint on lunar formation and orbital history
Vertical angular momentum constraint on lunar formation and orbital history
复制标题
月球形成和轨道历史的垂直角动量约束
DOI：
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发表时间：
2020
影响因子：
11.1
通讯作者：
J. Wisdom
中科院分区：
文献类型：
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作者：
Z. Tian;J. Wisdom
月球的形成和随后的地月系统的动力学演化有各种各样的情景，所有这些都受到以前没有充分利用的约束。使用这个约束，我们证明，最近提出的高分辨率的情况下是不符合目前的地月系统。在今后对月球形成和演化的所有研究中，都必须考虑到这一限制。月球可能是在一次巨大的撞击中形成的，留下了一个快速旋转的地球，但细节仍然不确定。在这里，我们研究了一个尚未充分利用的约束的含义：地月系统垂直于地球轨道平面的角动量分量在地月历史中几乎是保守的，除了月球轨道时可能的间隔。与地球绕太阳的运动共振。这一条件极大地限制了撞击后地球的方向和随后的月球轨道历史。特别是，涉及初始高密度地球的假设不能产生目前的地月系统。一个低密度的postimpact地球之后，在轨道演化的逃逸极限环仍然是一个可能的途径，产生目前的角动量和观察到的月球成分。
Significance There are various scenarios for the formation of the Moon and subsequent dynamical evolution of the Earth–Moon system, all of which are subject to a constraint that has not previously been fully exploited. Using this constraint, we demonstrate that the recently proposed high-obliquity scenario is not consistent with the present Earth–Moon system. This constraint will have to be taken into account in all future investigations of the formation and evolution of the Moon. The Moon likely formed in a giant impact that left behind a fast-rotating Earth, but the details are still uncertain. Here, we examine the implications of a constraint that has not been fully exploited: The component of the Earth–Moon system’s angular momentum that is perpendicular to the Earth’s orbital plane is nearly conserved in Earth–Moon history, except for possible intervals when the lunar orbit is in resonance with the Earth’s motion about the Sun. This condition sharply constrains the postimpact Earth orientation and the subsequent lunar orbital history. In particular, the scenario involving an initial high-obliquity Earth cannot produce the present Earth–Moon system. A low-obliquity postimpact Earth followed by the evection limit cycle in orbital evolution remains a possible pathway for producing the present angular momentum and observed lunar composition.