The End of the Lunar Magnetic Field

Lunar magnetic field
A new analysis of Moon rocks pins down the end of the lunar dynamo, the process by which the Moon once generated a magnetic field. Image credit: Hernán Cañellas and Benjamin Weiss

Magnetic measurements of the lunar crust and Apollo samples indicate that the Moon generated a magnetic field billions of years ago. The ancient lunar magnetic field was likely even stronger than the Earth’s magnetic field is today. However, it has been unclear when the lunar magnetic field ceased. Now, a team led by scientists from MIT have used young Apollo 15 samples to pin down the timing of the lunar dynamo’s end, showing that it ceased sometime between approximately 1.92 and 0.80 billion years ago. The new findings are consistent with the predicted lifetime of core crystallization in the Moon, a proposed mechanism for powering the lunar dynamo that could have generated a weak and long-lived magnetic field in the later part of the Moon’s history. The MIT-led research group is planning to measure the direction of the Moon’s ancient magnetic field in hopes of gleaning more information about the Moon’s evolution. READ MORE