Titan's atmospheric haze: the case for HCN incorporation

It is suggested that the incorporation of HCN in Titan's atmospheric haze m ay be an important process affecting the HCN profile and the C/N ratio in T itan's haze. By introducing a loss to the haze term for HCN (i.e, a product ion term of "poly-HCN") in the photochemical model of Lara et al. (1996), w e have improved the model's ability to simultaneously reproduce the observe d HCN and Ca hydrocarbon profiles in Titan's lower stratosphere. The loss r ate of HCN by this process may be a few times 10(8) cm(-2) s(-1). The calcu lated C/N ratio in the haze, assuming that the haze is primarily produced f rom C6H2, C8H2 and "poly-HCN", is approximately equal to 2, in agreement wi th the composition of laboratory tholin analogues.