On the possibility of lunar core phase detection using new seismometers for soft-landers in future lunar missions

Abstract

Information on the lunar central core; size, current state and composition; are key parameters to understand the origin and evolution of the Moon. Recent studies have indicated that possible seismic energies of core-reflected phases can be identified from past Apollo seismic data, and core sizes are determined, but we have still uncertainties to establish the lunar core parameters. We, therefore, plan to detect seismic phases that pass through the interior of the core and/or those reflected from the core–mantle boundary to ensure the parameters using new seismometers for future lunar soft-landing missions such as SELENE-2 and Farside Explorer projects.As the new seismometers, we can apply two types of sensors already developed; they are the Very Broad Band (VBB) seismometer and Short Period (SP) seismometer. We first demonstrate through waveform simulations that the new seismometers are able to record the lunar seismic events with S/N much better than Apollo seismometers. Then, expected detection numbers of core-phases on the entire lunar surface for the two types of seismometers are evaluated for two models of seismic moment distributions of deep moonquakes using the recent interior model (VPREMOON).The evaluation indicates that the VBB has performance to detect reflected S phases (ScS) from the core–mantle boundary mainly on the lunar near-side, and the P phases (PKP) passing through the interior of the core on some areas of the lunar far-side. Then, the SP can also detect PKP phases as first arrival seismic phase on limited regions on the lunar far-side. If appropriate positions of the seismic stations are selected, core-phases can be detected, allowing us to constrain the origin and evolution of the Moon with future lunar soft-landing missions.