Extended, new phase diagram of methane. The orange line represents the estimated D–P–T inside the Earth; the solid blue line is for the ocean, superimposed from Figure 2. Here: (i) “a” represents the ground surface, (ii) “b,” is the average depth of the ocean, ∼3.7 km, (iii) “c,” is the meeting point of ocean geotherm and crust, (iv) “e,” is the point beyond which methane transitions to the SC solid-like state, and (v) the elliptical annotations identify approximate geological P − T ranges corresponding to methane hydrates and abiotic origin of methane.