Division Of Early History Of The Moon Based On Mascon

China’s data on the farside of the moon obtained by Chang’e-4 confirmed for the first time the existence of the lunar mantle material,and the world is in a period of lunar exploration boom.The impact basin is one of the most important geological features of the lunar surface,and the moon gradually cooled down during the evolution process.It became almost silent about 3 billion years ago,and the internal dynamic geological activities basically stopped.Therefore,the impact basin retains the information of the early history of the lunar evolution.Mascons are high-density material anomalies beneath the lunar basins,which is the main difference between the lunar basins and the earth basins,it is an important feature of the lunar impact basins.Therefore,mascons can help study the early history of the moon.Previous studies on mascons largely focused on the origin of mascons,and this study will use mascons to analyze the early evolutionary history of the moon.Firstly,in this paper the impact basins are identified by using DEM data of Chang’e-1 CCD.The slope and curvature of DEM are calculated,then the impact basins are automatically identified by Hough transform.Combined with artificial visual interpretation and discrimination,the impact basins with diameters greater than 200 km on the lunar surface are identified.Eventually,62 impact basins with diameters greater than 200 km were retained except the Basin Aitken.After the basin identification,the identification of the mascons begins.Because Bouguer gravity anomaly can reflect the density difference of the material,it is necessary to make a Bouguer gravity anomaly map of the moon.In this paper,GRAIL gravity spherical harmonic model GRGM900 C published by NASA and topographic spherical harmonic model of LOLA laser altimeter are used to produce the Lunar Bouguer gravity anomaly by the method of band-limited Bouguer gravity anomaly.Based on the Bouguer gravity anomaly map obtained,62 basins identified before are examined,and it was found that 45 of them contains mascons,and most of the non-mascon basins are concentrated in the pre-Nectarian period and Nectarian basins are basically mascon basins.In mascon basins,the younger the mascon is,the stronger the gravity signal is,and the younger the basin is,the stronger the topographic signal is.Therefore,it can be seen that the mascon basins on the moon have obvious characteristics of chronological distribution.Finally,the ABAQUS finite element software is used for simulation analysis.It was found that the high temperature in the early lunar period caused the deformation of the basin,which resulted in the decrease of the upwelling degree of the deep mantle of the basin and the decrease of the gravity anomaly of the mascon.Therefore,the impact basins formed in different historical periods have different deformations due to the different geological conditions of the moon itself.Finally,the impact basins formed in different historical periods have topographic and gravity signals with different strengths.Therefore,this paper holds that the early history of the Moon can be divided into four stages,and it is urgent to determine the first mascon on the Moon in the future.Like the first impact basin on the Moon,which is of great significance to the analysis of the evolutionary history of the Moon,the first mascon on the moon is also of great significance to divide the history of the Moon and to analyze the early evolution of the Moon,which reflects the evolution of the lunar own geological state.