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Dryad

Code and data used for reproducing calculations of lunar crustal thermal evolution and zircon resetting during a tidal heating event

Data files

Oct 25, 2024 version files 29.21 KB

Abstract

The last giant impact on Earth is thought to have formed the Moon. The timing of this event can be determined by dating the different rocks assumed to have crystallized from the lunar magma ocean (LMO). This has led to a wide range of estimates for the age of the Moon between 4.35 and 4.51 billion years ago (Gyr), depending on whether ages for lunar whole-rock samples or individual zircon grains are used. Here we argue that the common occurrence of ~4.35 Gyr ages among lunar rocks and a spike in zircon ages at about the same time is indicative of a remelting event driven by the Moon’s orbital evolution rather than the original crystallization of the LMO. We show that during passage through the Laplace Plane Transition the Moon experienced sufficient tidal heating and melting to reset the formation ages of most lunar samples, while retaining an earlier frozen-in shape and rare, earlier-formed zircons. This new paradigm reconciles existing discrepancies in estimates for the crystallization time of the LMO, and permits formation of the Moon within a few tens of Myr of solar system formation, consistent with dynamical models of terrestrial planet formation11.  Remelting of the Moon also explains the lower number of lunar impact basins than expected, and allows metal from planetesimals accreted to the Moon after its formation to be removed to the lunar core, explaining the apparent deficit of such materials in the Moon compared to Earth.