Observations with the VIMS instrument on Cassini have identified the presence of liquid ethane in one of the large lake-like features observed on Saturn's moon, Titan. These results are reported by R. Brown and colleagues in the 31 July issue of Nature.
Ontario Lacus is a lake-like feature in the south-polar region of Titan first detected with the Cassini Imaging Science Subsystem in mid-2005. Brown and colleagues report on observations of this region that were made during the 38th close fly-by of Titan on 4 December 2007 with the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini Spacecraft.
Titan's thick atmosphere makes study of its surface difficult except for specific atmospheric windows at 2.0, 2.7 and 5.0 um. The VIMS instrument can penetrate the atmosphere through these windows to obtain, for example, measurements which are used to determine the chemical composition of the surface.
Infrared observations of Ontario Lacus yielded spectra with features which are indicative of the composition and nature of the contents of the lake. A characteristic ethane signature was observed in the VIMS spectra at 2.0