Carbon, nitrogen, and hydrogen are fundamental building blocks of the solar system, playing essential roles in the origin of life. Methane (CH₄) and nitrogen (N₂) are the simplest molecules formed in the C-H-N system, and do not react under atmospheric conditions. However, evidence of their reaction has been found on the surface of Titan. To explore the chemistry of the system deep within planets, high pressures and temperatures must be considered, a topic where prior research was scarce. In a recent study, researchers from the Centre for Science at extreme Conditions (CSEC) detail their discovery of compound formation in the C-H-N system by compressing mixtures of methane and nitrogen to extreme pressures in a diamond anvil cell.

At approximately 7 GPa (~70 kbar), two novel compounds formed, which were identified as (CH₄)₇(N₂)₈ and (CH₄)₅N₂. While these still retain molecular methane and nitrogen, compression beyond 160 GPa triggers a dramatic transformation. Here, the molecules dissociate and react to form a new material composed of covalently bonded carbon, hydrogen, and nitrogen atoms. Remarkably, this compound remains stable even when the pressure is released. Furthermore, the team found that subjecting methane-nitrogen mixtures to high temperatures and pressures (above 1400°C at 40 GPa) leads to their decomposition into diamond and ammonia. This research demonstrates that pressure alone can trigger reactions in systems that appear stable, providing a crucial insight into the chemistry occurring within planetary interiors.