Abstract
Several seismic experiments were deployed on the Moon by the astronauts during the Apollo missions. The experiments began in 1969 with Apollo 11, and continued with Apollo 12, 14, 15, 16 and 17. Instruments at Apollo 12, 14, 15, 16 and 17 remained operational until the final transmission in 1977. These remarkable experiments provide a valuable resource. Now is a good time to review this resource, since the InSight mission is returning seismic data from Mars, and seismic missions to the Moon and Europa are in development from different space agencies. We present an overview of the seismic data available from four sets of experiments on the Moon: the Passive Seismic Experiments, the Active Seismic Experiments, the Lunar Seismic Profiling Experiment and the Lunar Surface Gravimeter. For each of these, we outline the instrumentation and the data availability.We show examples of the different types of moonquakes, which are: artificial impacts, meteoroid strikes, shallow quakes (less than 200 km depth) and deep quakes (around 900 km depth). Deep quakes often occur in tight spatial clusters, and their seismic signals can therefore be stacked to improve the signal-to-noise ratio. We provide stacked deep moonquake signals from three independent sources in miniSEED format. We provide an arrival-time catalog compiled from six independent sources, as well as estimates of event time and location where available. We show statistics on the consistency between arrival-time picks from different operators. Moonquakes have a characteristic shape, where the energy rises slowly to a maximum, followed by an even longer decay time. We include a table of the times of arrival of the maximum energy t_{max} and the coda quality factor Q_{c}.Finally, we outline minimum requirements for future lunar missions to the Moon. These requirements are particularly relevant to future missions which intend to share data with other agencies, and set out a path for an International Lunar Network, which can provide simultaneous multi-station observations on the Moon.
Highlights
Many seismic experiments were deployed on the Moon by the astronauts during the Apollo missions
The Lunar Surface Gravimeter (LSG) used a Lacoste-Romberg type of spring-mass suspension to measure the vertical changes in local gravity and vertical ground motion
Dimech et al (2017) found and categorized 50,000 events recorded by the Lunar Seismic Profiling Experiment at Apollo 17
Summary
Many seismic experiments were deployed on the Moon by the astronauts during the Apollo missions. These experiments were part of the Apollo Lunar Seismic Experiments Package (ALSEP). The seismic instruments included passive seismometers, a gravimeter, and geophones which were deployed in active source experiments, and later in passive listening mode. The passive seismic stations from Apollo 12, 14, 15 and 16 remained operational until the final transmission in 1977. These remarkable experiments provide a valuable resource. 12 Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Université Côte d’Azur, Nica, France. 16 Institut de Physique du Globe de Paris, CNRS, Université de Paris, Paris, 75005, France
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