A low velocity zone for P waves is detected at 400 km depth near the point where the melting temperature of the dry silicate mantle is reached at 1700 o C. 3. S waves are not detected below 1600 km, perhaps signifying another partial melt zone in the lunar core. Seismic activity is mostly impact events, with some moonquakes in the deep interior, which seem to be correlated with peaks in the solid lunar tide. D. Temperature structure and heat flow 1. Determined primarily from electrical conductivity measurements.
Specific luminosity is higher than the Earth's , suggesting greater radiogenic heat production.
E. Gravity and density 1. Far side density is slighly lower, reflecting possibly thicker crust. For images and more information see the Nine Planets moon page .