The end of the lunar dynamo.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31911941.
- Also identified by DOI 10.1126/sciadv.aax0883 and PMC identifier 6938704.
- Licence recorded as CC BY-NC.
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Abstract
Magnetic measurements of the lunar crust and Apollo samples indicate that the Moon generated a dynamo magnetic field lasting from at least 4.2 until <2.5 billion years (Ga) ago. However, it has been unclear when the dynamo ceased. Here, we report paleomagnetic and <sup>40</sup>Ar/<sup>39</sup>Ar studies showing that two lunar breccias cooled in a near-zero magnetic field (<0.1 μT) at 0.44 ± 0.01 and 0.91 ± 0.11 Ga ago, respectively. Combined with previous paleointensity estimates, this indicates that the lunar dynamo likely ceased sometime between ~1.92 and ~0.80 Ga ago. The protracted lifetime of the lunar magnetic field indicates that the late dynamo was likely powered by crystallization of the lunar core.