月球目前的同步旋转轨道状态使得形成的撞击坑分布满足一定的不对称性.本文利用最新的LRO影像和地形数据,结合早期的Clementine影响数据,分析了月球辐射状撞击坑经度方向成坑率分布,结果表明所识别的辐射状撞击坑的年龄为0.9 Ga内,西—东半球方向存在明显不对称性,比值约为1.35～1.53;同时利用辐射状撞击坑模拟了0.9 Ga内的同步旋转轨道的平均状态,得到该时间内月球的向点-背点为70°W-110°E附近;最后利用撞击坑数据库资料对月球形成以来各地质世纪时间尺度内的撞击坑进行了成坑率分布分析,结论表明月球在大爆炸中后期间可能处于过近似的同步轨道旋转状态,但是与现在的轨道运行状态相反,月球在之后的地质时期内经历了翻转,其诱因可能是雨海和东方海盆地遭受的撞击.%There would be spatial cratering frequency asymmetries under current spin-orbit resonance of synchronous rotation on the moon.The frequency distribution of radial craters population,which is younger than about 0.9 Ga,was analyzed with the LRO and Clementine image data,showing an asymmetry of 1.35～1.53 in west-east hemisphere direction;With the assumption that the lunar was under a slow but gradual synchronous rotation,the average apexantapex was analyzed during 0.9 Ga using the radial craters,suggesting a shift from 70°W110°E to 90°W-90°E.The impact frequency variation of craters from the Heavy Bombardment was analyzed using the Lunar Crater Database on the scale of geological ages,showing that a totally opposite approximate synchronous rotation probably existed during the Heavy Bombardment period,but was lately destroyed by severe impact of Imbrium or Orientale possibly.The lunar likely has experienced a reversal.
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