Study On Small-Scale Lunar Craters’Morphology And Degradation

The Moon is a calibration planet for the cratering record of Earth-Moon system, and even the solar system, of which, the impact craters are its most obvious morphology. They are important for our study of the evolution of the moon, solar system meteorite impact history and space environment. Since the90s of the last century a new round of international exploration of the moon has beening setting off for development and utilization of lunar resources, and lunar exploration work is one of the major initiatives of our country for the deep-space exploration. The Chang’E satellites, especially the "Chang’E-2", have acquired a large number image data of high-precision of lunar surface, which is sufficient for the study of the morphology of the crater.In this paper, at the background of the scientific research work of the Chang’E project, morphological characteristics, degradation characteristics of small craters, and the crater retention age and stratigraphic sequence of the unit, have been studied.First, we systematically analyzed the structural morphology and evolution characteristics of small craters. Most small impact craters are simple bowl-shaped and widely distributed, with diameters less than15to20km. Significantly affected by the degradation, they are the ideal study objects of the morphology characteristics and evolution. Crater counting method is widely used for the planets stratigraphic analysis, when lacking of sampling samples.Then, for large amounts of data, automatical method of crater identification and morphological parameters extraction is necessary. We attempts the applications of craters identification method based on contour shape constraints using DEM, and the method based on regional segmentation using image. A crater segmentation method according to the direction slope is also present, so as to extract the crater morphological parameters. The distribution characteristics and relevance of the crater morphology parameters are analysed, and we select the crater depth as the leading parameter for degradation.Next, crater degradation is the phenomenon of turning darken, filled or even disappear under the influence such as the meteorite impact in the space environment. Statistical methods of crater size frequency distribution are used for the degradation. which performed as equilibrium for the aspect of the relative ages of geologic units. Morphology of crater directly characterizes its formation age, and then geological formation age of the unit, in the name of degradation parameter.A cautious solution of crater counting for estimating the age of a planet’s surface is proposed, based on the small craters’size frequency distribution (SFD). The influences of age uncertainty, degradation and secondary impact craters, is analysed.Crater degradation state such as the morphological characteristics is the direct factors of formation age. Degradation model based on the relationship of the crater diameter-depth is obtained, through crater morphological characteristics analysis. The formation age of the small craters, then the stratigraphic sequence and evolution procedure can be delivered from the model.Based on the morphology and evolution of small craters, we select typical geological unit of mare for the study area, and study the degradation systematically to establish the a numerical model. And the retention age calculation method and the stratigraphic sequence are also analysed. The research content is of significance for the study the distribution characteristics of impact crater and evalution of the space environment.