标题： 水星自转的长期演化 I. 倾角和地核-地幔摩擦的影响 显示英文标题

标题： Long-term evolution of the spin of Mercury I. Effect of the obliquity and core-mantle friction

摘要： 水星目前的倾角非常低（小于0.1度），这使得先前的研究总是假设行星过去演化过程中的倾角接近于零。 然而，水星自转轴的初始方向未知，且可能与今天大不相同。 因此，我们认为，当行星的旋转速率首次遇到自旋-轨道共振时，倾角可能是显著的。 为了计算任何演化场景下共振中的捕获概率，我们详细介绍了控制自旋长期演化的动力学方程，包括倾角的贡献。 水星的长期自旋演化是由与太阳的潮汐相互作用引起的，但也受到地核-地幔边界粘性摩擦的影响。 在这里，这种效应也得到了特别关注。 先前的研究表明，液态核心极大地提高了被捕获到自旋-轨道共振的概率。 我们确认了零倾角下的这些结果，但我们发现，随着倾角的增加，捕获概率通常会降低。 最后，我们展示了，当地核-地幔摩擦与倾角演化相结合时，自旋可以演化出一些意想不到的配置，如同步或1/2自旋-轨道共振。 显示英文摘要

摘要： The present obliquity of Mercury is very low (less than 0.1 degree), which led previous studies to always adopt a nearly zero obliquity during the planet's past evolution. However, the initial orientation of Mercury's rotation axis is unknown and probably much different than today. As a consequence, we believe that the obliquity could have been significant when the rotation rate of the planet first encountered spin-orbit resonances. In order to compute the capture probabilities in resonance for any evolutionary scenario, we present in full detail the dynamical equations governing the long term evolution of the spin, including the obliquity contribution. The secular spin evolution of Mercury results from tidal interactions with the Sun, but also from viscous friction at the core-mantle boundary. Here, this effect is also regarded with particular attention. Previous studies show that a liquid core enhances drastically the chances of capture in spin-orbit resonances. We confirm these results for null obliquity, but we find that the capture probability generally decreases as the obliquity increases. We finally show that, when core-mantle friction is combined with obliquity evolution, the spin can evolve into some unexpected configurations as the synchronous or the 1/2 spin-orbit resonance.