MoonShake: a Future Lunar Seismic Network delivered by Penetrators

Abstract:

We envision a Lunar Seismic Network to be deployed by penetrators. Penetrators are bullet-shaped vehicles designed to penetrate a surface and embed instruments beneath the ground. Between 1969 and 1972, the Apollo astronauts deployed seismometers on the Moon, providing insights about the Moon’s interior from moonquakes and impacts. Now, we have the technology to use penetrators to deploy microseismometers to observe seismic activity on the Moon. One such seismometer is the Silicon Seismic Package (SSP). A first-generation version of the sensor was deployed on Mars in 2018 as part of InSight’s seismic package. We estimate that the SSP’s noise floor will be below 2x10e-10 (m/s^2)/Hz^(1/2) between 0.3 and 3 Hz, a similar noise floor to the Apollo instruments at these frequencies. The seismometers would be deployed in small clusters of up to eight penetrators. Signals from the different seismometers are stacked to reduce random noise, increasing the signal-to-noise ratio and providing cleaner seismic signals. In combination with Earth-based observations of impact flashes from meteoroid impacts, a single site could provide information about the local subsurface, including the thickness of the crust and crustal layering. Further missions could establish a network of seismometers. Using the network, we could investigate the asymmetry of the thickness of the Moon’s crust, variations in the seismic velocity of the mantle, and the thickness of the lunar core.