[Previous] | [Session 46] | [Next]
T. W. Momary, K. H. Baines, B. J. Buratti (JPL/California Institute of Technology), Cassini VIMS Team
The Visual Infrared Mapping Spectrometer (VIMS) aboard Cassini boasts 352 channels with which to obtain views of Titan. By utilizing different wavelengths, it is possible to differentiate between relative altitudes on Titan, both in the atmosphere and also of topographic features. Over the past year, as Cassini has swung around the Saturnian system, a wealth of images have been obtained in visual and near-infrared wavelengths. Certain windows, such as at 2.02 microns, allow VIMS to pierce Titan's haze and see right to the surface. Other wavelengths, such as 2.83 microns, probe higher in Titan's atmosphere, and are sensitive to the various presumably methane clouds and hazes that typify Titan's skies. Recent passes by Titan indicate that there is currently a scarcity of cloud cover (on the order of 1.5-2% of Titan's visible surface obscured by clouds). The prominent South Polar Cloud has diminished in recent months and Titan's atmosphere has been relatively clear during these passes. The sparse nature of Titan's cloud cover, the periodic flare ups and quiescent periods, and the possibility that clouds remain anchored near topographic features are all intriguing and puzzling. In addition to probing cloud cover, we are using the same technique to probe the surface of Titan. Certain features that are relatively bright in all wavelengths, including methane bands that generally probe only at altitude, indicate high topography. Furthermore, the Huygens GCMS experiment has reported an enhancement of methane in the lower 2 km of Titan's atmosphere, more than twice what had been expected. This implies that VIMS is more sensitive to topography than was previously thought. We are currently investigating this. A bright elongated feature present on Xanadu, at -23 degrees latitude and 125 degrees longitude, seems to exhibit behavior in these wavelengths that suggest that it is at a higher altitude than surrounding topographic features. We are continuing to probe the surface and atmosphere of Titan, particularly looking into data from the coming targeted flybys, and will present our latest findings.
[Previous] | [Session 46] | [Next]
Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.