Persistence and origin of the lunar core dynamo

Area of Science:

• Lunar science
• Geophysics
• Paleomagnetism

Background:

• The ancient lunar core dynamo's power source and field generation mechanism remain debated.
• Understanding the dynamo's lifetime is crucial for lunar evolution models.

Purpose of the Study:

• To determine the lifetime and intensity of the ancient lunar dynamo.
• To constrain the power source and generation mechanism of the lunar magnetic field.

Main Methods:

• Analysis of two mare basalts aged 3.56 billion years.
• Paleomagnetic analysis to determine the strength and stability of the ancient magnetic field.

Main Results:

• Mare basalts were magnetized in a stable dynamo magnetic field of at least ~13 μT.
• The lunar dynamo's lifetime is extended by ~160 million years.
• The field was likely continuously active after the last major basin-forming impact.

Conclusions:

• Impact-driven rotation changes likely did not power the dynamo at this late stage.
• A persistent power source, such as lunar mantle precession or compositional convection, is required.
• The findings necessitate revisions to models of the Moon's internal evolution and magnetic field history.