Abstract
Four prominent features of Titan's haze are found within the '3.4-mu m' absorption to be uniform with recent vertically resolved Cassini/VMS spectra.(1) These are absorptions at 2998 cm(-1) (3.34 mu m), 2968 cm(-1) (3.37 mu m), 2927 cm(-1) (3.42 mu m), and 2882 cm(-1) (3.47 mu m). A detailed fitting suggests that the 2998 cm(-1) feature could originate from amorphous acetonitrile (CH3CN) carrying about 25% of integrated optical depth; the remaining features, which account for 75% of the integrated optical depth, could arise from a distinct triplet (C-H stretching) structure of radiolyzed hydrocarbons. An additional feature was possibly evidenced at altitudes higher than 300 km and attributable to 'polymer-capped' methane (CH4), significantly constraining the chemical composition of organic haze layers under Titan's active radiation field.