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The end of the lunar dynamo
Saied Mighani1, Huapei Wang1,2, David L Shuster3,4
1Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology (MIT), 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Science Advances
|January 9, 2020
Summary
The Moon
Area of Science:
- Lunar geology
- Paleomagnetism
- Geophysics
Background:
- The Moon possessed a global magnetic field for billions of years.
- The exact cessation time of the Moon's dynamo is not well-constrained.
Purpose of the Study:
- To determine when the Moon's dynamo magnetic field ceased.
- To investigate the longevity and potential power source of the lunar dynamo.
Main Methods:
- Paleomagnetic analysis of lunar breccias.
- Argon-Argon (Ar-Ar) dating of lunar samples.
- Reconstruction of past magnetic field strengths.
Main Results:
- Two lunar breccias cooled in a negligible magnetic field (<0.1 μT) at 0.44 ± 0.01 and 0.91 ± 0.11 billion years ago.
- The lunar dynamo likely ceased between approximately 1.92 and 0.80 billion years ago.
- The extended duration suggests late dynamo activity.
Conclusions:
- The lunar dynamo persisted for an extended period, possibly until as recently as 0.80 billion years ago.
- The protracted lifetime of the lunar magnetic field suggests ongoing core crystallization as the power source.
- This finding refines our understanding of the Moon's thermal and magnetic evolution.
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