Which Planet Rains Diamonds?

Laboratory experiments and planetary models suggest that deep within the ice giants Neptune and Uranus, the immense pressure (about 200,000 atmospheres) and temperature (about 5,000 °C) split methane (CH₄) molecules, and the freed carbon atoms are squeezed into diamond crystals. These "diamond hailstones" may be centimetres in size and sink through the dense hydrogen-helium atmosphere like rain, potentially accumulating in a slurry or solid layer around the planet core. In 2017, researchers at SLAC National Accelerator Laboratory successfully recreated these conditions in the lab and observed diamond formation from a plastic (hydrocarbon) target, supporting the theory.