Mercury Had an Ancient Magnetic Field, Data Indicates

posted: 05/08/15
by: Discovery.com Staff
Surface of Mercury
NASA/Johns Hopkins University Applied Physics Laboratory

It what may be NASA's MESSENGER Probe's swan song, researchers studying the defunct probe's data have found evidence that Mercury's once-strong magnetic field has been in place for much longer than originally thought.

Low-altitude observations made by the probe indicate that ancient rocks on Mercury were heavily magnetized. As the probe was nearing the end of its life in very close orbit to Mercury, its instruments detected the magnetism from the rocks, which could not have been sensed from a higher altitude.

"Magnetized rocks record the history of the magnetic field of a planet, a key ingredient in understanding its evolution," MESSENGER Participating Scientist Catherine Johnson. "We already know that around 3.7 to 3.9 billions years ago Mercury was volcanically and tectonically active. We now know that it also had a magnetic field at around that time."

Mercury and Earth are the only celestial bodies in the inner solar system with a magnetic field generated by a fluid, metallic outer core. Both planets have an outer core comprised of molten iron.

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