Uranus and Neptune have long puzzled scientists: their magnetic fields are heavily tilted and tangled, nothing like Earth's. The answer lay in an exotic form of water — superionic ice, which fills their interiors.
The temperature difference from the scorching core to the frigid surface drives protons to move from hot to cold, carrying entropy with them. Their organized flow creates an electric current, which in turn generates a magnetic field. So the ice acts like a natural thermocouple, converting a heat gradient into magnetism. The field's strength depends on how steep the gradient is: it differs on Uranus and Neptune, which is why their fields are not alike. Calculations based on proton flow match observations precisely.
Amazingly, the same effect powers a kitchen probe thermometer: there, a hot tip generates voltage in the wires. Only here, the charge carriers aren't electrons in metal but protons in ice — solid and fluid at once.
Pressure inside Uranus and Neptune is millions of times higher than on Earth, turning water into superionic ice — a substance that is both solid and liquid at once.