Credit for Image At Left:
Featured image copyright: Julien Monteux and Denis Andrault.
The gravitational effects associated with the presence of the Moon and Sun cause cyclical deformation of the Earth's mantle and wobbles in its rotation axis. This mechanical forcing applied to the whole planet causes strong currents in the outer core, which is made up of a liquid iron alloy of very low viscosity. Such currents are enough to generate the Earth's magnetic field. © Julien Monteux and Denis Andrault.
The classical model of the formation of Earth's magnetic field raised this major paradox: For the geodynamo to work, the Earth would have had to be totally molten four billion years ago, and its core would have had to slowly cool from around 6,800 °C at that time to 3,800 °C today – i.e. a drop of 3,000 °C. Now, a team of researchers suggests that, on the contrary, its temperature has fallen by only 300 °C. The action of the Moon, overlooked until now, is thought to have compensated for this difference and kept the geodynamo active. The effect of gravitational forces on a planet's magnetic field has already been well documented for two of Jupiter's moons, Io and Europa, and for a number of exoplanets.
The Earth is a thermal engine generating the fundamental processes of geomagnetic field, and this new model shows that the Moon's effect on the Earth goes well beyond merely causing tides. There is a synergy between the Earth, the Moon and the Sun, which supports our planet and the life on it.
- "The deep Earth may not be cooling down" - Denis Andrault, Julien Monteux, Michael Le Bars and Henri Samuel - Earth and Planetary Science Letters - March 30, 2016 - doi:10.1016/j.epsl.2016.03.020