Denis Andrault, Julien Monteux, Michael Le Bars, Henri Samuel: The deep Earth may not be cooling down, Earth and Planetary Science Letters Available online 30 March 2016 Claims without the moon, the Earth's core would have cooled and shut off its magnetic field long ago. And we and most life would probably be in deep trouble. Mercury, Venus, and Mars all lack magnetic fields (anyhow 100X below Earth's). Which is presumably not a coincidence. But some Jupiter moons still have a field exceeding any of the above 3 planets. Ditto. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)