Mercury's mighty magnet

Earth's magnetic field has long been understood to be the result of a solid iron core rotating at a different speed to a surrounding liquid material. This resulting dynamo effect produces a magnetic field we can be grateful for - without it, the sun's solar wind would have rubbed away our atmosphere, leaving us cold and dry like our neighbour Mars.

Mercury was determined to have something of a magnetic field, too, yet being much smaller than Earth, it was thought to have cooled to the core long ago. Therefore its weak magnetism must be the result of random patches of residual magnetism being held in its structure.

Yet with the recent Messenger mission, this is now in doubt. It appears at least strong enough to be able to shield much of its surface from the solar wind.

Earth and Mercury are the only two inner solar system bodies with magnetic fields produced from within.

http://www.sciencedaily.com/releases/2008/01/080130140130.htm

Mike

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