Diamond Rain

Deep inside both Uranus and Neptune, pressures reach millions of atmospheres. Under these conditions, methane molecules are torn apart and the carbon atoms are compressed into diamond crystals that sink toward the core. Scientists have reproduced this process in laboratories, confirming that it likely rains diamonds inside these ice giants.

The interiors of both planets also contain superionic water — a bizarre state of matter where oxygen atoms lock into a crystal lattice while hydrogen ions flow through it like a liquid. This substance conducts electricity like a metal but is technically a form of ice.