The Influence of Benzene as a Trace Reactant in Titan Aerosol Analogs

Benzene has been detected in Titan's atmosphere by Cassini instruments, with concentrations ranging from sub-ppb in the stratosphere to ppm in the ionosphere. Sustained levels of benzene in the haze formation region could signify that it is an important reactant in the formation of Titan's organic aerosol. To date, there have not been laboratory investigations to assess the influence of benzene on aerosol properties. We report a laboratory study on the chemical composition of organic aerosol formed from C 6 H 6 /CH 4 /N 2 via far ultraviolet irradiation (120–200 nm). The compositional results are compared to those from aerosol generated by a more "traditional Titan" mixture of CH 4 /N 2 . Our results show that even a trace amount of C 6 H 6 (10 ppm) has significant impact on the chemical composition and production rates of organic aerosol. There are several pathways by which photolyzed benzene may react to form larger molecules, both with and without the presence of CH 4 , but many of these reaction mechanisms are only beginning to be explored for the conditions at Titan. Continued work investigating the influence of benzene in aerosol growth will advance understanding of this previously unstudied reaction system.