First results of Herschel-SPIRE observations of Titan

Abstract

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 ¹²C/¹³C = 87 ± 6 in CO and 96 ± 13 in HCN, ¹⁴N/¹⁵N = 76 ± 6, and ¹⁶O/¹⁸O = 380 ± 60. The last of these results is the first documented measurement of Titan's ¹⁶O/¹⁸O ratio in CO, with a value 24% lower than the terrestrial ratio.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.