月球撞击坑溅射堆积与辐射纹蒙特卡洛模拟

Formation of lunar impact crater ejecta and rays and their Monte-Carlo simulation

撞击坑是月球上最常见的地质构造之一,通常只有较大规模的撞击坑才能形成超长辐射纹.然而最近我们的研究发现,在一些大规模撞击坑的边缘,溅射堆积发育有良好的孔隙结构;在这些多孔的撞击坑边缘区域,即使是小规模撞击事件,也易于形成具有辐射纹的撞击坑.本文建立了包含孔隙结构的撞击抛射模型,并利用蒙特卡洛方法模拟了垂直撞击溅射堆积构造和超长辐射纹,不仅揭示了在多孔结构岩石区域易于形成超长辐射纹的原因,同时为撞击辐射纹的形成提供了一种可行的解释方案.

Lunar impact crater is one of popular geology structures and only some of large scale craters were surrounded by ultra-long rays.The nature and origin of lunar rays have long been the subjects of major controversies.Recently,our study shows that ejecta on the edge of many large scale impact craters are porous.Even a small scale impact event can produce super-long rays on the edge.We have found this kind of small scale rayed craters in the craters of Gibbs,Byrgius and Ryder.Especially,in the cross-regime of the edges of the Szilard and Harkhebi,the rayed crater was rather outstanding. To interpret these unusual small scale rayed craters,we introduced an impact ejection model to deal with ejecta in the rich-porous regime.Results show that it tends to produce super-long rays in the rich-porous regime than other regime without porous rocks.That is the reason why we can observe some small scale rayed craters on the edge of large scale craters,while we can＇t observe rayed craters in the bottom of large scale craters.By using Monte-Carlo method to simulate the ejection in the richporous regime,we obtain the topography of crater ejecta and super-long rays.The numerical results show a good agreement with crater scaling law.Our model provides a reasonable interpretation of rayed crater.