Does Callisto have a sub-surface ocean?
Inside CallistoThe internal structure of Callisto shows the same paradoxical dichotomy between age and youth that the surface exhibits. Unlike the other Galilean satellites, Callisto seems more like a uniformly dense sphere, indicating that most of its rock and ice are mixed together. A core is ruled out. Therefore, the interior has never been heated strongly, either by radioactive decay or by tides. The moon does not participate in the tidal heating that kneads the other Galilean satellites. On the other hand, the moon is far from dead. As the Galileo magnetometer found, Callisto seems to perturb the surrounding Jovian magnetic field in a peculiar pattern. This disturbance, unlike Ganymede’s, resembles what is seen in classic physics experiments in which a hollow copper sphere is subjected to a changing magnetic field.
The internal structure of Callisto shows the same paradoxical dichotomy between age and youth that the surface exhibits. Unlike the other Galilean satellites, Callisto seems more like a uniformly dense sphere, indicating that most of its rock and ice are mixed together. A core is ruled out. Therefore, the interior has never been heated strongly, either by radioactive decay or by tides. The moon does not participate in the tidal heating that kneads the other Galilean satellites. On the other hand, the moon is far from dead. As the Galileo magnetometer found, Callisto seems to perturb the surrounding Jovian magnetic field in a peculiar pattern. This disturbance, unlike Ganymede’s, resembles what is seen in classic physics experiments in which a hollow copper sphere is subjected to a changing magnetic field. In such an experiment, electric currents are set up in the conducting shell of the sphere, which in turn produces a magnetic field that exactly counters the imposed field. Callisto’s
