Lunar Tidal Deformation and the Interior Structure of the Moon

Kurzfassung

Important clues on the constitution of the lunar interior can be gained by monitoring tidally-induced surface deformations from orbiting and landed spacecraft and earthbased, highly precise lunar laser ranging observations. In addition to the Apollo lunar seismic data record, those observations could provide useful constraints on mantle elasticity and size, composition and physical state of a lunar core. A major advantage is that the tidal forcing function for a synchronously rotating satellite like the Moon is exactly known. A higher temporal resolution and precision than with groundbased and space techniques alone can be achieved by additional emplacement of a geophysical network of one or several soft-landed surface stations on the Moon. However, tidal measurements may be significantly impeded by instrumental drift, instrument coupling to the surface, and local sources of noise. We will present relations between key tidal parameters such as degree-2 body tide Love numbers that can be retrieved from monitoring tidally-induced changes of local gravity and surface tilt and the constitution of the deep interior of the Moon. A most promising approach would involve time-varying gravitational field observations from an orbiting spacecraft combined with long-term monitoring of tidally-induced gravity changes at the lunar surface.