WU Yuan ling and CHEN Jian-ping reported in 2019 that the lunar Mare is an important topographical unit while the impact crater is an important annular structure on the surface of the Moon. The purpose of this paper is to study the temporal and spatial distribution characteristics of impact craters in the mare area and lay a good foundation for further determination of impact events in the lunar mare area. The LU106016 database is selected to classify the mare chronologically, which is divided into five periods, namely Aitkenian, Nectarian, Late Imbrian, Early Eratothenian and Late Eratothenian.
The relationship between the periods of the impact craters and the number of geological units, the number of impact craters and the impact areas are analyzed statistically. According to the results of statistical analysis, Late Imbrian is an era in which impact events occurred frequently in the lunar mare area, and the number of geological units, the number of impact craters and the impact areas are much larger than those in the other four periods, from Aitkenian to Late Eratothenian, the impact strength shows a trend of first increasing and then decreasing. At last, combining the Kernel Density Estimation and latitude-longitude distribution, the spatial distribution characteristics of impact craters in each period are analyzed in details.
The Aitkenian impact craters are mainly distributed in the Mare Orientale, Mare Humorum, Mare Serenitatis and Mare Marginis areas, with a relatively balanced distribution in latitude and longitude. The Nectarian craters are mainly distributed in the Mare Spumans and Mare Australe area, and is extremely uneven in latitude and longitude distribution, the number of craters in the western hemisphere is significantly larger than that in the eastern hemisphere, and in latitude, the number of craters in the southern hemisphere is significantly larger than that in the northern hemisphere. The number and concentration of late Imbrian craters in the northern hemisphere are higher than those in the southern hemisphere, while the number and concentration in the eastern hemisphere are higher than those in the western hemisphere. The impact craters of the early Eratothenian are evenly distributed in the Mare Imbrium area, with relatively scattered distribution and uneven latitude and longitude distribution, mainly in the western and northern hemispheres. The number of impact craters in Late Eratothenian is very small, but the distribution is very regular, they are mainly distributed in the Mare Imbrium and Mare Anguis area, with 20o longitude and 35o latitude as axisymmetric distribution respectively.
Based on the LU106016 impact crater database, this paper analyzes the spatial distribution characteristics of impact craters in different periods, and draws the following conclusions:
1. The geological units of lunar mare area can be divided into five periods, namely Aitkenian, Nectarian, Late Imbrian, Early Eratothenian and Late Eratothenian, in which Late Imbrian contains the largest number of impact craters, the largest impact area and the widest distribution.
2. Aiken impact craters are mainly distributed in the Mare Orientale, Mare Humorum, Mare Serenitatis and Mare Marginis, among which there are a large number of
concentrated distributions in the Mare Humorum and Mare Marginis areas, and the latitude and longitude distribution is relatively balanced.
3. The impact craters in Nectarian Period are clustered at the height of the Mare Spumans and Mare Australe, while some impact craters are clustered in the region of Mare Nectaris and Mare Nubium, but the degree of aggregation is more dispersed than that in the Mare Spumans and Mare Australe area. In terms of latitude and longitude distribution, the distribution of impact craters is extremely uneven, the number of impact craters in the western hemisphere is significantly larger than that in the eastern hemisphere, and in latitude, the number of impact craters in the southern hemisphere is significantly larger than that in the northern hemisphere.
4. The Late Imbrium impact crates are distributed in the whole lunar mare area, especially in Mare Serenitatis, Mare Imbrium, Mare Crisium and the Mare Australe. Overall, the spatial distribution is uneven. The number and concentration of Late Imbrium impact crates in the northern hemisphere is higher than that in the southern hemisphere, and the number and concentration in the eastern hemisphere is higher than that in the western hemisphere.
5. The impact craters of the early Eratothenian are evenly distributed in Mare Imbrium area, and they are relatively scattered mainly in the western and northern
hemispheres.
6. The number of impact craters in Eratothenian is very small, but the distribution is very regular, they are mainly distributed in the Mare Imbrium and Mare Anguis area, with 20o longitude and 35o latitude as axisymmetric distribution respectively.
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