6. Mercury: a battered world
A mysterious magnetic field
Mariner 10 carried a sensitive device for detecting magnetic fields, a magnetometer. As the spacecraft moved toward Mercury, the magnetometer plotted the fluctuating magnetic field of the solar wind. However, when it reached the neighborhood of Mercury, it abruptly entered a new environment - a magnetic field that emanated from the planet. The increasing strength of this field as the spacecraft approached the planet indicated that the magnetic field of Mercury's surface would be 0.0033 x 10-4 tesla, or 0.01 times the Earth's surface magnetic field. Such a field was strong enough to carve out of the solar wind an elongated magnetic cavity with a tail; pointing away from the Sun.
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Copyright 2010, Professor Kenneth R. Lang, Tufts University