The role of photochemical processes in evolution of the isotopic composition of the atmosphere of Titan

Molecular nitrogen, the main component of the modern atmosphere of Titan, may have formed without significant changes in the nitrogen and hydrogen isotopic composition from the clathrate hydrate of ammonia NH₃ · H₂O_SLD, which is the main accreted form of nitrogen. The most preferable transformation mechanism of NH₃ · H₂O_SLD into atmospheric N₂ is its thermal decomposition in the interior of Titan rather than the photochemical decomposition of ammonia in the upper atmosphere of early Titan. The photolysis of ammonia does not lead to a change in the isotopic composition of nitrogen, as all the nitrogen remains in Titan’s atmosphere. The photolysis of NH does not lead to a change in the isotopic composition of nitrogen in Titan’s atmosphere. Fractionation of hydrogen and nitrogen isotopes during the impacts of comets with Titan does not seem to be significant either. It will be possible to determine the dissociative fractionation factor, the original ratio ¹⁴N/¹⁵N, and the mass of Titan’s original atmosphere when fractionation of nitrogen isotopes in Titan’s atmosphere is examined in additional theoretical and experimental studies that take into account processes occurring during the formation of a system of Saturn’s satellites.