<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Hi philotasO,C and N quickly combine with H2 to form H2O, CH4, NH3 in the proto-stellar gas clouds.Heat tends to break ammonia over time, forming C-N compounds (aminated compounds). Interesting as almost no ammonia has been found in the plume, as opposed to many C-N- compounds, indicating a significant heat source for a significant time. On Titan or TNOs, CH4 exposed to radiation (in high atmosphere for Titan, no surface for TNOs) tends to form heavier carbonated chains, (starting with ethane C2H6), and in presence of NH3 or N2, C-N compounds. Even aromatic chains. On icy bodies, NH3 tends to be "buried" as a first step, as the freezing of the water-ammonia will differentiate H2O from NH3, leaving an exterrnal shell of pure water ice and increasing gradually the concentration of NH3 in the subsyrface ocean, up to 32% (eutectic). Then, water-ammonia begins to freeze homogenously.But most TNOs have N2 (gas or solid) on their surface. And Titan atmosphere is essentially N2. The formation of heavy carbonated chains results in large quantities of tholins. Best regards. <br />Posted by h2ouniverse</DIV></p><p> Thanks <strong>h2o</strong>, that cleared up things.</p> <div class="Discussion_UserSignature"> </div>