Georgios Bampasidis

Surface albedo spectral properties of geologically interesting areas on Titan

We investigate the nature and possible formation processes of three areas on Titans surface which have been suggested as geologically interesting: Hotei Regio, Tui Regio, and Sotra Patera. We also reanalyze the spectral characteristics of the Huygens Landing Site. We apply a statistical Principal Component Analysis (PCA) and a radiative transfer (RT) method on the Visual and Infrared Mapping Spectrometer Datacubes in order to retrieve the surface albedo of distinct spectral units in the near infrared. We have been able to exploit only a subset of the currently available Hotei Regio data, which are, in general, not optimal in terms of geometry for an analysis with a plane-parallel RT code. Our inferred surface albedos present generally higher values from 1 to 2 µm and lower ones at 0.94 and in the 2.6–5 µm region. The Regions of Interest (RoIs) within Hotei Regio, Tui Regio, and Sotra Patera are always significantly brighter than the surrounding areas. The largest variations are found longward of 2 µm and mainly at 5 µm. This higher surface albedo with respect to the surrounding area and, in general, the fact that the spectral behavior is different for each of these areas, is probably indicative of diverse chemical compositions and origins. We compare the spectral albedos with some suggested surface candidates on Titan (such as H2O, CO2, and CH4 ices, as well as tholin) and discuss possible chemical composition variations as well as other interpretations.

FIRST OBSERVATION IN THE SOUTH OF TITAN'S FAR-INFRARED 220 cm(-1) CLOUD

An emission feature at 220 cm{sup -1} which has been attributed to a cloud of condensed material in Titans winter stratosphere has been seen for the first time in the south. This feature had previously been found only at high northern latitudes during northern winter and spring. The material emitting at 220 cm{sup -1}, as yet unidentified, may be volatiles associated with nitrile gases that accumulate in the absence of ultraviolet sunlight. Not detected as recently as 2012 February, the 220 cm{sup -1} feature clearly appeared at the south pole in Cassini spectra recorded on 2012 July 24, indicating a rapid onset of the emission. This is the first indication of the winter buildup of condensation in the southern stratosphere that has been expected as the south pole moves deeper into shadow. In the north the 220 cm{sup -1} feature continued to decrease in intensity with a half-life of 3 years.

Life in the Saturnian Neighborhood

The Cassini–Huygens mission has revealed a very active and diverse Saturnian system in which several satellites show promising conditions for habitability and the development and/or maintenance of life. Titan, for example, is the only other body in the solar system besides Earth to possess a dense atmosphere composed essentially of nitrogen (97 %) and in which the combination with methane (2 %) gives rise to a host of organic compounds. The presence of seasonal effects, unique geomorphological features, and a probable internal liquid water ocean make Titan one of the most astrobiologically interesting bodies. Another Cassini discovery of tremendous relevance to astrobiology is the large organic-ladden plumes ejected from Enceladus’ south pole cracks, mainly made of water vapor but suggestive of a complex organic chemistry occurring in the interior of this small satellite, in the presence of liquid water. Future extensive and in situexploration ideas which could help us improve our understanding of these issues in the Kronian system are also discussed here.