Detection of 13CH3D on Titan

We report the detection of 13CH3D in Titan's stratosphere from Cassini/CIRS infrared spectra near 8.7 μm. Fitting simultaneously the ν6ν6 bands of both 13CH3D and 12CH3D and the ν4ν4 band of CH4, we derive a D/H ratio equal to 1.32−0.11+0.15×10−4 and a 12C/13C ratio in deuterated methane of 82−18+27, consistent with that measured in normal methane.