High-Resolution 3 Micron Spectroscopy of Molecules in the Mesosphere and Troposphere of Titan

A high-resolution 2.9-3.5 μm spectrum of Titan has revealed a surprisingly strong emission band of hydrogen cyanide (HCN) and strong absorption bands of acetylene (C₂H₂) and monodeuterated methane (CH₃D), in addition to methane (CH₄) emission and absorption known from previous observations. Whereas the C₂H₂ and CH₃D absorptions are largely in the troposphere, the HCN emission must occur at higher altitudes. However, the intensity of the HCN band is inconsistent with our current understanding of the upper atmosphere of Titan.