Flexi Says: Diamonds can form deep in the dense atmospheres of the gas giant planets: Jupiter, Saturn, Uranus, and Neptune. This happens when elemental carbon in the form of graphite or soot comes under crushing pressures within the thick atmospheres. As the diamonds grow, they may fall deeper into the atmosphere. In the lower depths of Saturn and Jupiter, the temperature and pressure conditions are so extreme that the diamonds can melt into liquid, forming diamond "rain" drops. Diamonds don't melt under the 1 atm pressure at Earth's surface, even at extremely high temperatures. Instead, they sublime directly to vapor. However, the pressure deep inside Saturn and Jupiter is over a million times greater than on Earth's surface, and temperatures can reach over 11,000 °C ( 21,000 °F).