Possible Thermal History of the Moon

The possible thermal history of the Moon is investigated by means of theoretical models. The calculations include the effects of melting and time-dependent redistribution of radioactive heat sources. The known constraints can best be satisfied by a model which is characterized by relatively high initial temperatures close to the melting range; melting and, consequently, fractionation and redistribution of radionuclides would occur during the first 1.5 × 10 9 yr and would then be followed by an effective cooling process. Heat flow measurements on the lunar surface should permit a distinction between such a completely fractionated model and a non-fractionated model or a model with restricted fractionation in the outer few hundred kilometers.