Seismic studies provide definitive knowledge of internal planetary structure

Reexamination of seismic data from the moon has provided an important glimpse of its mantle and core structure which has bearing on its thermal petrological and rotational history. Data suggest the presence of a fluid-like transition layer between the lunar core and mantle. The moon may therefore still be undergoing chemical segregation and thermal layering. The seismologist s challenge is substantiating this view. Further investigation of internal structure hinges on innovative development of a lunar geophysical network (LGN) that includes advanced seismic sensors and deployment methods. This network will need to overcome the limitations of an initially sparse grid and improve upon the quality of apollo-ERA seismograms. The best design for such instruments considering they will likely be delivered by a new class of small commercial landers is currently underdeveloped. We propose to raise the TRL of a silicon audio commercial-off-the-shelf geophone from 4 to 6. This instrument is a novel combination of a classic seismic geophone and a laser interferometer. Micron-scale movements of an internal mass are recorded as induced current while submicron-scale motions are recorded by the laser system. This allows for a small (