Apollo Lunar Seismic Experiment—Final summary

Abstract

Processing and initial analysis of the entire set of Apollo lunar seismic data collected continuously from 1969 through 1977 have now been completed. Recent results include: 1) better defined deep moonquake locations, which appear to be bounded rather sharply between about 800 km and 1000 km depths with concentrations near both boundaries; and 2) middle mantle (∼500 to 1000 km depth) seismic velocities of Vp, = 8.3 ± 0.4 km/sec and Vs = 4.6 ± 0.2 km/sec, which are significantly higher than previous estimates and represent an increase of velocities from the upper mantle as opposed to a decrease in previous estimates.

Interior Structure, Composition, and Mineralogy of the Terrestrial Planets

“…Early seismic studies favored crustal thickness of about 60 km beneath the Apollo network (Goins et al, 1981;Nakamura et al, 1982;Toks€ oz et al, 1974). An early analysis of body wave phases from artificial impacts of known impact time and location provided evidence for a dual-layered crust about 60 km thick beneath the Apollo 12 and 14 stations near Mare Cognitum (Toks€ oz et al, 1974), whereas a putative thickness of 75 AE 5 km was derived from seismic data near the Apollo 16 highland site (Goins et al, 1981).…”

Farside explorer: unique science from a mission to the farside of the moon

“…Current knowledge Much of our knowledge of the Moon's internal structure comes from analyses of the Apollo seismic data that were collected from 4 stations in network mode between 1971 and 1977 [46]. The Apollo instruments were extremely sensitive, but the limitations of late 1960s digital technology, the narrow frequency range, and the small footprint of the network near the sub-Earth point placed severe limitations on seismic data interpretation.…”

“…6 Example P and S seismic ray paths associated with meteoroid impacts and deep moonquakes (using the velocity model of [46]). Meteoroid impact locations and times will be provided by the observation of impact flashes, allowing interior modeling with even a single seismic station.…”

Frequency band enlargement of the penetrator seismometer and its application to moonquake observation

“…In the Apollo mission, a seismic network consisting of four seismic stations (at Apollo 12,14,15,and 16 sites) was deployed on the lunar near-side, and seismic observations using this network continued from April 1972 to September 1977. The collected data set has provided abundant information about lunar internal structure and seismic activity (e.g., Gagnepain-Beyneix et al, 2006;Garcia et al, 2011;Lognonné et al, 2003;Lognonné and Johnson, 2007;Nakamura et al, 1982). However, owing to the limitations on the frequency responses and sensitivities of the Apollo seismometers, obtaining information about the whole lunar structure and the source mechanisms of lunar seismic events has been proven to be difficult.…”