Tholinomics—Chemical Analysis of Nitrogen-Rich Polymers

摘要

The polymeric composition of Titan’s tholinsslaboratorynanalogues of Titan’s aerosolssis elucidated using highresolutionnmass spectrometry. This complex organic matternis produced by plasma discharge in a gaseousnnitrogen-methane mixture and analyzed with a hybridnlinear trap/orbitrap mass-spectrometer. The highly structurednmass spectra are treated with tools developed fornpetroleomics (Kendrick and van Krevelen diagrams), withnoriginal adaptations for nitrogen-rich compounds. Ourngoal is to find the best chemical basis set to describe thencompositional space that these polymers occupy, to shednlight onto the chemical structure of tholins. We succeedednin assigning the molecules identified in the mass spectranof tholins to a small number of regularly distributednX-(CH2)m(HCN)n families, where the balanced copolymern(m )n) is determined to play a central role. Withinneach family, the polymer lengths n and m presentnPoisson-type distributions. We also identify the smallestnspecies of a subset of families as linear and cyclicnamino nitrile compounds of great astrobiological interest:nbiguanide, guanidin, acetamidine, aminoacetonitrile,nand methylimidazole.