| The moon is the closest planet to the earth and the outpost for deep space exploration.The determination of the age of the planet’s surface can not only help to distinguish the sequence of geological events and reveal the clues of the evolution of the planet,but also provide great help for the selection of the landing site of the lunar exploration mission.Therefore,in the process of lunar exploration and research,the determination of the lunar surface age is very important in dividing it into different geological units and analyzing the formation process of impact crater.Because the impact crater is the most obvious feature of the lunar surface,it is very important to study the lunar surface.At present,the commonly accepted and widely used method for lunar surface dating is the impact crater statistical dating method,commonly known as the impact crater size frequency distribution method.This method is based on the relationship between the diameter of the impact crater on the lunar surface and the total number of impact craters in a unit area,combined with the radioisotope age of lunar surface rock samples.The primary problem of using impact crater statistical dating method is the removal of the secondary impact crater.The traditional methods are based on the shape and spatial distribution characteristics of the secondary impact crater which is obviously different from the initial impact crater.There are some limitations in this method,it can’t recognize the remote secondary impact crater,because it is not very clear about the distinction between the isolated,morphological and spatial characteristics,and the initial impact crater.Therefore,the method used in this paper is to identify the secondary impact crater based on the difference in the content of the material inside and outside the impact crater.In this method,the mean value of the material content in the impact crater is first selected as the material content value in the impact crater,and then the mean value of the material content in the non-impact crater area of the lunar soil is visually selected as the material content value of the lunar soil outside the impact crater.The difference between the above two values is calculated,and a threshold value is obtained through comparative analysis to distinguish the secondary impact crater.After the secondary impact craters were eliminated,the initial impact craters were used to date the lunar surface geological unit,compared with known ages to adjust the threshold and verify the feasibility of the experiment.For the purpose of improving the reliability of the experiment in this paper,the experimental results of this paper were verified by statistical analysis of impact craters and the statistical analysis of the degradation of secondary impact craters.The results obtained verified the feasibility of the method used in this paper. |
