C allisto ("ka LIS toh") is the eighth of Jupiter 's known satellites and the second largest. ... C allisto is only slightly smaller than Mercury but only a third of its mass. U nlike Ganymede , Callisto seems to have little internal structure; However there are signs from recent Galileo data that the interior materials have settled partially, with the percentage of rock increasing toward the center. ... C allisto's surface is covered entirely with craters. ... Callisto Fact Sheet from JPL . ...
... A dynamo is created in a magnetic field by an electric circuit, part of which is moving relative to the rest (additional conditions must also be met). ... Furthermore, the plasma between them conducts electricity very well along its magnetic field lines, which act as if they were wires connecting Io and the planet (drawing). ... The drawing is not to scale. ... The Hubble Space Telescope , using its Wide Field and Planetary Camera 2, has been photographing auroras of the planet Jupiter. ...
Jupiter is the largest of the nine planets, more than 10 times the diameter of Earth and more than 300 times its mass. ... The mean density of Earth is 5.245 times that of water. The pull of gravity on Jupiter at the top of the clouds at the equator is 2.4 times as great as gravity's pull at the surface of Earth at the equator. ... It is tipped about 11њ to Jupiter's axis of rotation, similar to Earth's, but it is also offset from the center of Jupiter by about 10,000 kilometers (6,200 miles). ...