First results of Herschel-SPIRE observations of Titan

We investigate the composition of Titan’s stratosphere from high-resolution submillimetric observations performed with the SPIRE instrument on the Herschel satellite. From the flux density spectrum measured in the 20−52 cm −1 interval at an apodized resolution of 0.08 cm −1 , we determine the stratospheric abundances of CH4, CO, HCN, as well as the isotopic ratios 12 C/ 13 C = 87 ± 6i n CO and 96 ± 13 in HCN, 14 N/ 15 N = 76 ± 6, and 16 O/ 18 O = 380 ± 60. The last of these results is the first documented measurement of Titan’s 16 O/ 18 O ratio in CO, with a value 24% lower than the terrestrial ratio.

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