Research On Geological Units In Mare Nubium Based On Chang'e Lunar Microwave Radiometer Data

Mare Nubium is one of the most ancient mare on the moon.It has experienced a long period of volcanic evolution,and is an important region of the current study of mare volcanic evolution.However,Mare Nubium is also seriously affected by the coverage of spatters,and the geological units is very complex,which greatly limits the recognition research of the geological units of Mare Nubium by visible remote sensing technology.The Chang'E-2 satellite microwave radiometer(CELMS)data is unique microwave data to China for probing the lunar regolith.The data are sensitive to the substrate temperature and compositions of the shallow layer.The 4 frequency channels data can weaken the effect of surface cover and reflect the temperature and composition information corresponding penetration.Therefore,based on the CELMS data of the Chang'E-2 satellite,this paper intends to conduct a cognitive study on the basalt units in the Mare Nubium where the sputter coverage is severe.The main results of the paper are as follows:1?According to the characteristics of the microwave radiometer data,the brightness temperature of mare Nubium is mapped.Using the brightness temperature data at noon and midnight,the brightness temperature maps and the brightness temperature difference maps in the study area were made.Then for the problem that the lunar microwave brightness temperature data is greatly affected by latitude,this paper proposes to use the ratio method to reduce the effect.The relationship between latitude and average brightness temperature is obtained by polynomial fitting method,and then the ratio of brightness temperature to fitted brightness temperature isused for mapping.The image produced by this method better reduces the influence of latitude.2?Based on the noon and midnight images constructed by the ratio method,ISODATA unsupervised classification method is used to classify the images,and the result is compared with the three-phase basalt based on visible data.Based on the classification results and the distribution of brightness temperature and brightness temperature difference in the study area,the geological units of Mare Nubium were divided.3?Combined with the information of the mineral composition,the following conclusions are drawn by analyzing the microwave brightness temperature characteristics of the geological units:(1)The basalt units in the Mare Nubium is divided into 3 categories,correspond to the three-phase basalt units.And the newer the basalt phase,the higher the content of iron and titanium.(2)The central area of Mare Nubium shows high brightness temperature in low-frequency images during both noon and midnight,but not in high-frequency images.It is speculated that this area is uniform in deeper areas and has a high substrate temperature.(3)A visible spectral abnormal region in the middle of mare Nubium is invisible in the low-frequency images.It is verified that the anomaly may only exist in a shallow area.(4)The area of impact crater materials in the western Mare Nubium identified by microwave data is smaller than the area identified by visible data.It shows that the thickness of highland materials in some areas of this unit is relatively small,and microwave remote sensing has been able to penetrate it effectively.In this paper,the geological units of Mare Nubium is studied based on the data of the Chang'E-2 lunar microwave radiometer.The used method can effectively divide and analyze the Mare Nubium geological units.Through the analysis of the microwave brightness temperature characteristics of the units,the results are well verification andsupplement to the visible results,and a new understanding of geological units of Mare Nubium is obtained.