WHEN the Voyager 2 spacecraft flew by Uranus, its observations of the planet’s magnetic field looked so strange scientists thought the instrument might have gone haywire. Now the bizarre pattern has been explained. The field originates from a thin shell of convecting ice.
Planetary magnetic fields are generated when electrically conductive fluids move within them. Earth, Jupiter and Saturn all have simple fields, with north and south poles aligned along the axis of rotation. That pattern arises from a thick layer of liquid circulating around a relatively small, solid core. But Voyager 2 found that Uranus and Neptune have complicated…
