Research progress and prospect of moonquakes

The Lunar interior structure is important for understanding the formation and evolution of the Moon, because it is closely related to the processes of magma ocean condensation, density differentiation and material convection. The Apollo missions established the first moonquakes observation network in the middle and low latitudes on the near side of the Moon, which provides us with a lot of valuable observations to study the moonquakes and interior structure of the Moon. However, the lunar seismography in the Apollo era was greatly limited on the sensitivity and some other aspects, which seriously affected the detection ability of the lunar interior structure. Up to now, no reliable internal reflection phase has been observed, which has led to a great academic debate on the thickness of the lunar crust, the size of the lunar core and the state of deep physical properties. In this paper, we review the Apollo instruments, data and applications, with special attention to the research progress in the interior structure, the scattering and the attenuation of lunar seismic waves. Finally, we prospect the future research direction of the lunar seismicity and present the basic conception of the first lunar seismometer from China.