Dissociation of methane into hydrocarbons at extreme (planetary) pressure and temperature.

Dipartimento di Fisica "G. Galilei," Universit√° di Padova, Via Marzolo 8, I-35131 Padova, Italy.
Science (Impact Factor: 31.03). 03/1997; 275(5304):1288-90. DOI: 10.1126/science.275.5304.1288
Source: PubMed

ABSTRACT Constant-pressure, first-principles molecular dynamic simulations were used to investigate the behavior of methane at high pressure and temperature. Contrary to the current interpretation of shock-wave experiments, the simulations suggest that, below 100 gigapascals, methane dissociates into a mixture of hydrocarbons, and it separates into hydrogen and carbon only above 300 gigapascals. The simulation conditions (100 to 300 gigapascals; 4000 to 5000 kelvin) were chosen to follow the isentrope in the middle ice layers of Neptune and Uranus. Implications on the physics of these planets are discussed.