论月球不对称的演化

EVOLUTION OF ASYMMETRY OF LUNAR CRUST

月球形成初期有一个固体内核，表层是岩浆“海洋”，重力分异、冷却固结形成月壳。由于同步自转，其一侧总是向着地球。在地球引力场作用下，使固体内核向地球一侧移动，月壳表层轻的物质向背地球一侧漂浮，所以月壳背地球一侧１５０公里，向地球一侧仅有６０公里，这种演化机制使大部分月海分布在向地球一侧。

The thickness of the lunar crust facing the earth is 40-60km,where most maria exist.Whereas that of the other side is up to 150km.This makes the asymmetry of the moon.The present paper put forward an explanation for the formation of this asymmetry.In the early stage,there was a solid lunar core surrounded by magma “ocean”,and the lunar crust was formed by gravitational differentiation and cooling consolidation.Owing to the synchronous rotation with the earth,one side of the moon always faces the earth.The solid lunar core moved towards the earth by earth's gravitational field,and as a result,the light substances on the lunar surface floated to the back side of the moon.This evolution machanism made the lunar surface thinner in the near earth side while thicker in the back side.Through theoretical inducement,the paper gives a formula to calculate the distance of lunar core moving toward the earth as: r=2Md·R 3My(D 2-R 2) Where Md is the mass of the earth,My is the mass of the moon,R is the radius of the moon,and D is the distance from moon to earth.According to this theory,it is concluded that the distance betwen the moon and the earth was 162,700km when their synchronous rotation happened.