Dissociation of CH 4 at High Pressures and Temperatures: Diamond Formation in Giant Planet Interiors?

Abstract

Experiments using laser-heated diamond anvil cells show that methane (CH 4 ) breaks down to form diamond at pressures between 10 and 50 gigapascals and temperatures of about 2000 to 3000 kelvin. 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 CH 4 at high pressures and temperatures can influence the energy budgets of planets containing substantial amounts of CH 4 , water, and ammonia, such as Uranus and Neptune.