Long-lived lunar volcanism sustained by precession-driven core-mantle friction

Area of Science:

• Planetary Science
• Geophysics
• Lunar Science

Background:

• Core-mantle friction from lunar spin axis precession is a significant early heat source.
• Its long-term impact on lunar thermal evolution and geological activity is not well understood.

Purpose of the Study:

• To investigate the influence of core-mantle friction on the Moon's long-term thermal evolution.
• To explain the Moon's early volcanic activity and its implications for core dynamics and water ice.
• To model the evolution of lunar obliquity and its effect on water distribution.

Main Methods:

• Utilized a one-dimensional thermal evolution model.
• Simulated core-mantle friction effects on mantle melting and core cooling.
• Analyzed the transition of the Cassini state and its impact on lunar obliquity.

Main Results:

• Core-mantle friction sustained global partial melting in the upper mantle until approximately 3.1 billion years ago.
• This friction suppressed secular core cooling and is unlikely to power a long-lived lunar dynamo.
• The model supports a Cassini state transition before the lunar magma ocean solidified, indicating decreasing lunar obliquity post-solidification.

Conclusions:

• Core-mantle friction is a key factor in explaining early lunar volcanism.
• The findings suggest a revised understanding of lunar core cooling and dynamo potential.
• Decreasing lunar obliquity may lead to greater accumulation of volcanically sourced water ice in polar regions.