Denk, T. and the Cassini ISS Team (2007). "Targeted Iapetus Flyby of Cassini: First Imaging Results." American Astronomical Society, DPS meeting #39, #6.01.


Abstract
On September 10, 2007, the first and sole targeted Iapetus flyby of the Cassini within six years took place (~5 weeks after submission of this abstract). The inbound plan covered the crescent over the leading side down to 480 m/pxl (at 145 degrees phase within the time frame between closest approach (C/A) minus 5:25 hrs and C/A observations of the dark/bright transition zone, the ridge, and a large (~500 km) trailing side were in the plan. From C/A-55 min to +180 min, the top-priority contained 11 different targets on the surface, including high-phase observations ridge (~30 m/pxl, 140°W longitude), 10 m/pxl samples of the dark terrain, two zone mosaics over the anti-Saturn hemisphere, and high-res. imaging (~50 m/pxl bright "Voyager mountains". Outbound observations included a global, 15-panel the complete trailing hemisphere (~450 m/pxl), as well as multiple regional color global color observation at 1.6 km/pxl and 34° phase. Imaging data will hopefully help to give answers to questions like: What is the record at Iapetus? How old is the surface? Might Iapetus indeed act as a reference surface age determinations in the whole Saturn system? What about the huge the ridge form? Are there more geologic features than the craters and the ridge, smaller scales? How is the dark and bright material distributed? Are there more kinds of dark material? How thick is the dark blanket, and might we even see deep within the dark terrain? Why is Iapetus' shape not spherical? What are the of the global color dichotomy? Etc. etc... And, most important: What causes the brightness dichotomy already recognized by J.-D. Cassini 335 years ago?