Lunar and planetary seismology

The last 4 years have been very significant for new results in lunar seismology and the emergence of a definite program in planetary seismology. Since 1970, four stations with seismic sensors have been placed on the moon at Apollo 14, 15, 16, and 17 sites. When combined with the seismic station operating at the Apollo 12. site since November 1969, these have formed an excellent network. The network has detected a large number of moonquakes and meteoroid impacts. In addition to these there have been nine artificial impacts (ascent stage of the lunar module (LM) and Saturn third‐stage booster (S4B)) of known energies, impact times, and locations. Data from all sources have been analyzed to determine the lunar velocity structure, the seismicity, and the properties of the lunar interior. This has been a pioneering program in extending the direct seismological exploration to another planetary body with both surprising and very significant results.