9
January 2003
Planetary science: By the heat of the Moon
The Moon has no 'global' magnetic field today but palaeomagnetic data and radiometric ages determined from samples brought back to Earth by the Apollo missions suggest there was an internally generated lunar magnetic field for a brief period, between 3.9 and 3.6 billion years ago. The idea that an internal dynamo could have existed so long (600–900 million years) after the formation of the Moon—only to then suddenly be switched off—has been difficult to explain using conventional models. But new numerical simulations of the early thermal history of the Moon show how a dynamo could have been formed in the Moon's interior by the removal of a marginally stable 'thermal blanket' layer enriched in radioactive elements at the base of the mantle surrounding a liquid iron core.
An early lunar core dynamo driven by thermochemical
mantle convection
DAVE R. STEGMAN, A. MARK JELLINEK,
STEPHEN A. ZATMAN, JOHN R. BAUMGARDNER & MARK A. RICHARDS
Nature
421, 143–146 (2003); doi:10.1038/nature01267
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Planetary science: Model for magnetic mystery
MARIA T. ZUBER
Today, the Moon has no magnetic field,
but analyses of lunar rocks suggest that it did in the past. Did changes in the
lunar interior create a magnetic dynamo billions of years ago?
Nature
421, 119–120 (2003); doi:10.1038/421119a
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