Near/Far Side Asymmetry in the Tidally Heated Moon

TL;DR

This study uses viscoelastic simulations to show that tidal heating in a Moon close to Earth is asymmetrically higher on the near side, influencing crustal growth and thermal evolution.

Contribution

It introduces a viscoelastic mass spring model to quantify near/far side tidal heating asymmetry in the Moon, highlighting its impact on lunar crust development.

Findings

Tidal heating is 10-20% higher on the near side.

Asymmetric heating influences crustal growth and magma ocean crystallization.

Near/far side asymmetry may trigger uneven lunar crust formation.

Abstract

Using viscoelastic mass spring model simulations to track heat distribution inside a tidally perturbed body, we measure the asymmetry of heating in the crust of a spin synchronous Moon in eccentric orbit about the Earth. With the Moon within a few Earth radii of the Earth, we find that tidal heating per unit area in a lunar crustal shell is asymmetric due to the octupole order moment in the Earth's tidal field and is 10 to 20\% higher on its near side than on its far side. Tidal heating reduces the crustal basal heat flux and the rate of magma ocean crystallization. Assuming that the local crustal growth rate depends on the local basal heat flux and the distribution of tidal heating in latitude and longitude, a heat conductivity model illustrates that a moderately asymmetric and growing lunar crust could maintain its asymmetry. Near/far side asymmetric tidal heating could serve as a trigger for uneven lunar crustal growth.