Theoretical study on mantle overturn processes in the moon and small rocky planets.

利用原行星盘模型，在考虑月球和小型岩质行星的原料多样性的基础上，对这些天体的内部演化进行了理论和数值研究。月球早期由于岩浆海洋的冷却和凝固而形成的一系列堆积的岩石层，应该已经转向稳定的结构。在翻转过程中，富镁橄榄石可能再次融化，这与月球背面富镁基矿物的暴露是一致的。月球目前的转动惯量因子可以用月球完成翻转后的密度曲线来解释。最近的航天器数据显示，水星富含硫的成分和e球粒陨石明显减少，这与我们的圆盘模型一致，而且水星还有一个厚度不到400公里的薄硅酸盐地幔。考虑到这种新结构，我们进行了热历史模拟。有人认为，水星的液体核心直到现在都是热对流的，允许发电机作用产生水星的本征磁场。

Theoretical and numerical studies on the evolution of the interiors of the Moon and small rocky planets were performed on the basis of the consideration about the variety of raw materials of these bodies by using a model of proto-planetary disk. A series of cumulate rock layers, formed in the early Moon due to cooling and solidification of a magma ocean, should have overturned toward stable structure. During the overturn process, Mg-rich olivine cumulate likely becomes to melt again, which is consistent with the exposure of Mg-rich mafic minerals on the lunar far-side. The present moment of inertia factor of the Moon is explained by the density profile after the completion of overturn. Recent spacecraft data shows that Mercury has a significantly reduced composition enriched in sulfur as well as E-chondrites, which is consistent with our disk model, and also has a thin silicate mantle with thickness less than about 400 km. We performed thermal history simulations considering such a new structure. It is suggested that the liquid core of Mercury is thermally convective until present, allowing dynamo action producing the intrinsic magnetic field of Mercury.