Inside the ice giant planets Uranus and Neptune, the conditions are so extreme that something amazing happens to carbon atoms: they get squeezed into diamond.
The atmospheres of these planets are loaded with methane gas - molecules made of carbon and hydrogen. As you go deeper, the pressure rises rapidly until it’s about 6 million times stronger than Earth’s surface atmosphere. At those pressures, the carbon and hydrogen atoms in methane molecules get torn apart. The hydrogen escapes upward, and the carbon condenses into tiny diamond crystals.
The diamonds, being heavy, then sink slowly downward through the planet’s mantle - like a slow, sparkling rain. Eventually they pile up near the core, where scientists believe there may even be an ocean of liquid diamond with diamond icebergs floating on top. Scientists have actually recreated the effect in laboratories on Earth, using lasers to compress methane fast enough to make tiny diamonds rain out.
