What causes earth's magnetosphere? How many planets have a magnetosphere?

Liquid metal forms a fluid dynamo, iron in the Earth's core, and metallic hydrogen in the outer planets. Venus and Mars have no magnetosphere, which has allowed the solar wind to strip atmosphere and especially hydrogen from the two planets. Jupiter's magnetosphere is huge, extending up to 7M km towards the Sun with a tail trailing almost to the orbit of Saturn. If Jupiter's magnetosphere were visible, from Earth it would appear larger than the sun and moon. Jupiter's moon Ganymede has its own small magnetosphere dominating and shielding only Ganymede's equatorial region. Saturn's magnetosphere is much weaker than Jupiter's and only extends about as far as Titan. Uranus and Neptune have magnetospheres that are displaced and tilted and include a large quadropole moment; theories include magnetic fields generated by water+ammonia oceans, or liquid diamond oceans which partially block fields. Jupiter's field strength at Jupiter's "surface" is about 20x Earth's (compass needles would snap, not lazily wander) while the three other outer planets have surface field strengths comparable to Earth's. However, the outer planets' magnetic dipole moments are much larger than Earth's. Mercury has a weak magnetic field, about 1% of Earth's. When discovered in 1974 scientists were surprised there was any magnetic field. This diagram shows the order(s) of magnitude difference in sizes of Mercury's, Earth's, Jupiter's, and the Sun's magnetospheres.