(a) Ternary phase diagram of H₂O, NH₃ and CH₄, with known methane hydrates phases (“MH-I” etc), ammonia hydrates (“ADH” etc.), and the solar abundance ratio (grey circle) indicated. (b) ELF=0.7 isosurface of ammonia quarterhydrate (AQH) at 100 GPa, outlining spherical oxygen anions O 2 − and N 2 H 7 + cations. O (N,H) atoms are red (blue, pink) spheres, respectively. Dashed lines indicate hydrogen bonds.