Insight into three-dimensional structure of the lunar crust and upper mantle in the Mare Crisium from gravity imaging

Abstract

Mare Crisium is a typical Mascon on the Moon, and a detailed 3-D structure of the lunar crust and upper mantle is essential to explore the causes of the lunar Mascon. However, research in the Mare Crisium region has focused more on surface rather than internal structure in the past few decades. With the development of space exploration technology, lunar gravity data have been applied several times to determine the internal structure of the Moon. Nevertheless, the gravity method has limitations in terms of vertical resolution. To address this issue, this paper adopts the wavelet multi-scale analysis method to decompose the gravity anomaly data in the Mare Crisium region. The power spectrum method is then used to estimate the mean source depth of the decomposed gravity anomaly signal. On the one hand, the gravity anomaly signal and its corresponding mean source depth at different scales can be used to stratify the structure of the lunar crust and upper mantle in the Mare Crisium region, and then obtain the density structure of each layer. On the other hand, the gravity anomaly signals from the crust-mantle undulations are extracted and combined with prior information to invert the depth of the crust-mantle interface in the Mare Crisium region. As a result, the 3-D structure of the lunar crust and upper mantle in the Mare Crisium region was obtained. The study indicates that there are two high-density bodies with a large range in the interior of Mare Crisium. The first high-density body is located in the western part of the Mare Crisium, and the centre of its bottom is about 54°E longitude and 17°N latitude. The second high-density body is located in the northeast of the Mare Crisium, and the centre of its base is about 63°E longitude and 25°N latitude. Additionally, the study found that the crust-mantle interface of the Mare Crisium is obviously uplifted, and the uplifting rebound phenomenon exists in the centre of the basin. Considering the depth and size of the high-density body, Mare Crisium probably experienced two high-angle, high-speed impacts at least.