Dissociation of CH4 at high pressures and temperatures: diamond formation in giant planet interiors?

Experiments using laser-heated diamond anvil cells show that methane (CH₄) breaks down to form diamond at pressures between 10 and 50 GPa and temperatures of about 2000 to 3000K. Infrared absorption and Raman spectroscopy, along with X-ray diffraction, indicate the presence of polymeric hydrocarbons in addition to the diamond, which is in agreement with theoretical predictions. Dissociation of CH₄ at high pressures and temperatures can influence the energy budgets of planets containing substantial amounts of CH₄, water, and ammonia, such as Uranus and Neptune.