Investigating the Laplace plane transition theory for lunar chronology with a thermal-orbital coupled model

The Moon may have formed from a giant impact with the initial Earth spinning fast about a highly tilted axis. In this case the subsequent orbital evolution causes the lunar orbit to go through instabilities during the Laplace plane transition (LPT). Based on this model it was suggested that the level of tidal heating in the Moon during the LPT is capable of explaining a predominance of lunar rock ages at ~4.35 Ga and the survival of older zircons; the heating in this period is enough to resurface much of the Moon, but not enough to reset the near-surface zircon chronology. However, this finding was based on estimates of heating rates using model orbital histories that did not consider the evolution of the Moon’s internal structure during tidal heating and the consequent feedback on orbital evolution. For this work we tested the previous theory using a coupled thermal-orbital model, and find that the peak heating rates are not significantly different from those previously determined (~1014–1015 W). In the case of a moderately dissipative Earth (Qe = 300), the typical duration of the heating event (up to 150–200 Myr) implies a Moon formation age of around 4.5 Ga, consistent with some lunar chronologies. We also provide an explanation for the quasiperiodic oscillation of lunar semimajor axis and eccentricity, which is characteristic of the LPT instability.