Neptune and Uranus contain a high proportion of methane, which campus researchers have now shown can turn into diamond and complex organic matter compounds at the high temperatures and pressures found inside these planets.Shock compression studies performed by Hirai et el recorded the transition of methane into diamond at 19 GPa and between 2200 and 3000 degrees Kelvin. The conversion of methane into diamond is primarily dependent on temperature, but the ambient pressure of the atmosphere is also important to consider.
In addition to being awesome, diamond rain could also account for the excess heat radiated from Neptune (in addition to heat from the sun). Energy released by diamonds falling and settling towards the planet’s core is thought to boost the magnetic field of Neptune, thus increasing the heat radiated from the planet (Sanders 1999 and Kerr 1999). Although diamond rain has not been a proven phenomenon, it is pretty amazing to imagine. Given the experimental evidence, it is also not an unlikely occurrence.