The “diamond rain” on Jupiter and Saturn is a theoretical phenomenon where, under the extreme pressure and temperature conditions deep within their atmospheres, elemental carbon, is compressed into diamonds, which then fall towards the planet’s core.

Jupiter and Saturn have atmospheres rich in methane (CH4).

Lightning storms in these atmospheres can break down methane into its constituent elements, carbon and hydrogen.

As these carbon atoms fall deeper into the planet’s atmosphere, they encounter increasing pressure and temperature.

Under these extreme conditions, the carbon atoms are forced into a diamond structure.
“Diamond Rain”:
These diamond “hailstones” then fall towards the planet’s core, where they eventually melt into a liquid sea of diamonds.

The pressure deep inside Jupiter and Saturn is estimated to be over a million times greater than on Earth’s surface, and temperatures can reach over 11,000 °C (21,000 °F)