Neptune may crush methane into diamonds.
Kerr
R A
RA
D018130:Diamond / Q000737:chemistry*; D006358:Hot Temperature; D006838:Hydrocarbons / Q000737:chemistry; D008697:Methane / Q000737:chemistry*; D018541:Neptune; D011312:Pressure; D018540:Uranus
D006838:Hydrocarbons; D018130:Diamond; D008697:Methane