Figure 6
From: Diamond formation from methane hydrate under the internal conditions of giant icy planets
Summary of diamond-formation conditions. The purple solid line is the predicted isentropes of Uranus and Neptune (represented by a single curve owing to the small differences)24. Blue, orange, and green lines are the melting curves of water25,26,27, methane9, and hydrogen28, respectively. The black dashed line is the decomposition curve of methane hydrate16. The grey solid line is the equilibrium boundary between graphite and diamond29. The red rhombi and squares are the conditions at which diamond formation was observed and not observed, respectively. The diamond-formation conditions in the C–O–H system obtained in this study are milder than those in the C–H system, as reported from atomistic simulations7,8, dynamic laser compression experiment (grey rhombus)6, and LHDAC experiments (grey- and blue-shaded areas)3,4.
