EUROPA鈥橲 sibling Callisto may also boast an underground ocean, scientists
say.
Margaret Kivelson of the University of California at Los Angeles says data
gathered by the Galileo spacecraft indicate that Jupiter鈥檚 moon Callisto does
not generate its own magnetism. Instead, the field detected is an echo of
Jupiter鈥檚 stronger field sweeping through the moon鈥檚 interior.
This induced field could only exist if Callisto contains an electrically
conducting layer, Kivelson said at last week鈥檚 Boston meeting of the American
Geophysical Union. An ocean 10 kilometres deep with the same conductivity as
seawater fits the bill surprisingly well. Although Callisto鈥檚 frozen terrain
lacks any sign of water, models have suggested that internal heat and pressure
could be melting ice 200 kilometres below the surface.
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