  Titan, with its thick, nitrogen-dominated atmosphere, has been seen from
satellite and terrestrial observations to harbour methane clouds. To
investigate whether atmospheric features such as clouds could also be visible
from the surface of Titan, data taken with the Side Looking Imager (SLI)
on-board the Huygens probe after landing have been analysed to identify any
potential atmospheric features. In total, 82 SLI images were calibrated,
processed and examined for features. The calibrated images show a smooth
vertical radiance gradient across the images, with no other discernible
features. After mean-frame subtraction, six images contained an extended,
horizontal feature that had a radiance value that lay outside the 95%
confidence limit of the predicted radiance when compared to regions higher and
lower in the images. The change in optical depth of these features were found
to be between 0.005 and 0.014. It is considered that these features most likely
originate from the presence of a fog bank close to the horizon that rises and
falls during the period of observation.
