Inversion Of The Basalt Thickness In Lunar Oceanus Procellarum

Oceanus Procellarum is the lunar largest maria with rich terrain structure and wide time span basalt, both of the ancient high titanium basalt and the latest moderate titanium basalt on the moon. Research on lunar basalt thickness and lunar structure characteristics is of great significance to conclude the magma evolution history and explore thermal evolution process of the moon.Considering that in the past studies on basalt thickness of Oceanus Procellarum area is greatly influenced by curvature and terrain on the lunar surface, the observation data used of low spatial resolution and cross-section structure taken into account only. Combined with the topography feature of Oceanus Procellarum region,this research is based on the high resolution and global LRS(Lunar Radar Sounder)data acquisition of Japanese SELENE satellite. According to the principle of Radar imaging and a real GPR wavelet extraction method, it simulates the lunar subsurface structure. Based on two-media model to process the LRS radar data, and get the subsurface structure cross-section image, and analysis of the parameters influence of the dielectric constant and the receiver aperture size on simulation precision. The results showed that, basalt relative dielectric constant and receiver aperture size are two important parameters in the LRS data imaging process simulation. Image resolution and the receiver aperture size were positively correlated. When the aperture size increases from 5 km to 40 km, image resolution has beeen dramatically improved, and it can obtain higher subsurface structure cross-section image.According to the simulation error estimates, basalt relative dielectric constant is set as6.25, the inversion error in between-0.2 and 0.2, and it guarantees the inversion precision of the basalt thickness.Meanwhile, according to characteristics of the subsurface echo image, research on basalt thickness inversion in the large Oceanus Procellarum area was accomplished and basalt isopach map was drawn. Combined with the basalt composition, ageinformation, we described the mare basalt distribution characteristics in the Oceanus Procellarum area, in-depth analysis of the influence of the composition, age and other factors on the basalt thickness and distribution characteristics, concluded the basalt magma evolution process in this region. It shows that,the Oceanus Procellarum area is covered with an average basalt thickness of about 65 m. The basalt thickness is up to 108m(41 ° W, 30 ° N) around the large craters area. The minimum basalt thickness value in other area is about 27m(49 ° W, 8 ° N). The result is compared with the results of Oshigami well.Contrast basalt composition distribution and age characteristics shows that the position of the subsurface boundary surface LRS detected is associated with Fe O and Ti O2 content in the lunar surface. In relatively low Fe O and Ti O2 content areas, basalt thickness is relatively large, and there are many large impact craters in this region and its volcanic activity is more frequent. In relatively high Fe O and Ti O2 content areas,the basalt thickness is relatively small, this is due to the high Fe O and Ti O2 content affected the radar detector sensitivity to the difference of dielectric constant.The research is based on basalt thickness, composition and age information to study the mare basalts distribution in the Oceanus Procellarum, analyzes the influence factors on the mare basalt thickness and distribution, providing important geological and geophysical information for the lunar magma evolution process. It improved the method to explore the lunar subsurface structural characteristics,providing a new thought to study the distribution of the lunar subsurface rocks,exploring a new way to research the thermal evolution history.