Magnetic field of Mercury, the only other known internally generated magnetic field of any terrestrial planet other than Earths. Its strength is 1% that of Earth and weaker than that of Ganymede. Generated by a partially molten core in the region where the core and the mantle meet. Its magnetic equator is significantly north of the physical equator (20% of radius), so that its strength is stronger in the northern hemisphere than the southern one. The only other planet that has this characteristic is Saturn, which is off only by less than 1%. The southern polar magnetic cap, where field lines are open to the interplanetary medium are much larger than those in the north. One theory is that it is beginning to flip.