McEwen, A., West, R., Turtle, E., Perry, J., Johnson, T., Delgenio, A., Dawson, D., Campbell, S., Barbara, J., and Porco, C. (2004). "Cassini Imaging Observations of Titan." Eos Trans. AGU 85(47), Fall Meet. Suppl., Abstract P41B-01.


The Cassini ISS team will present preliminary results from new high-resolution images of Titan. ISS can best detect the surface and lower-troposphere clouds though a narrow filter centered in the 940-nm methane window. Near-global coverage acquired during approach to Saturn revealed 100-km-scale dark markings in the equatorial region, some with straight trends or boundaries suggestive of tectonic influences. Cassini passed within 339,000 km of the south-polar region on July 2 and acquired images with scales of 2-3 km/pixel, revealing clouds that change on timescales of a hour or less. The photochemical haze limited resolution of the surface to ~10 km, as predicted (Porco et al., Space Sci. Rev., in press). No evidence for topographic shading was seen, probably because icy satellites tend to have low relief, not detectable at 10-km scales, but the haze scattering must also lower the contrast of any topographic shading. The albedo markings include straight and meandering dark linear features and crudely rectangular or irregular dark and bright patches. There is nothing suggestive of a large impact structure over this ~10% of Titan's surface. Over 4 Ga, comets are expected to produce from 0.6 to 6 impact features >=100 km diameter on 10% of Titan's leading hemisphere (Korycansky and Zahnle, in press, Planet. Space Sci.). If large impact structures are in fact rare on Titan, this would indicate significant endogenic resurfacing since an early period of heavy bombardment. The first close targeted flyby of Titan on October 26 will return much more detailed images (down to ~150 m/pixel) of an equatorial region on the anti-Saturn hemisphere, including the landing site for the Huygens probe, we will present preliminary image products and interpretations.