1. The Cassini Orbiter and the Huygens Probe Reveal Titan's Earth-Like Surface and Organic Atmosphere: The Huygens probe showed that Titan's surface is remarkably Earth-like, complete with evidence for methane rain, erosion, stream-like drainage channels and dry lake beds. The Cassini orbiter provided the first detailed global view of Titan's surface, including possible volcanoes, rain clouds, flow features, lakes, craters and vast dune fields, as well as other puzzling terrain. A soup of complex hydrocarbons, including benzene, has been detected in Titan's atmosphere.
Image right: Colored view of Titan's surface. Image credit: ESA/JPL/University of Arizona + Full image and caption
2. Closest-Ever Observations of Saturn's Rings Reveal Clumps, Kinks, and Waves: The Cassini cameras took the highest resolution images ever of Saturn's rings, and Cassini fields and particles instruments measured the in situ ring environment as the spacecraft skimmed above Saturn's rings just after Saturn orbit insertion. Discoveries included straw-like clumps several kilometers long in the A ring, an oxygen atmosphere just above the rings, signatures of marble-sized meteoroids impacting the rings, and evidence for slowly rotating ring particles.
Image left: Cassini images have revealed the presence of previously unseen faint rings in some of the gaps in Saturn's rings -- possible indicators of small yet-unseen moons. Image credit: NASA/JPL/Space Science Institute + Full image and caption
3. Phoebe: A Captured World From the Outer Solar System: Phoebe is a crater-scarred moon, with large landslides revealing bright water ice on crater walls and patchy clustering of silicate and organic material. The volatile ices tell scientists that Phoebe must have formed in the outer solar system and then was captured by Saturn's gravity - a survivor of objects much older than Saturn itself.
Image right: A high-resolution mosaic of Phoebe. Image credit: NASA/JPL/Space Science Institute + Full image and caption
4. Saturn's Dynamic Atmosphere: The entire northern hemisphere of Saturn has a completely new look since the Voyager encounters. It now appears deep blue, much like the deep, clear atmospheres of Uranus and Neptune. The shadow of the rings on the northern hemisphere probably cools it down, so the tan clouds sink to depths where they are no longer visible. Nothing like this had ever been suspected from previous observations. Powerful lightning storms - ten thousand times stronger than on Earth - occur in huge, deep thunderstorm columns nearly as large as the entire Earth. The storms occasionally boil up to the visible surface.
Image left: A large convective storm that appeared in Saturn's southern hemisphere in mid-September 2004. Image credit: NASA/JPL/Space Science Institute + Full image and caption
5. Enceladus: A Moon With a Tenuous Atmosphere: Tiny Enceladus seems to have a tenuous atmosphere, discovered in magnetic field data, that may imply internal activity. It may help explain the source and variability of Saturn's E ring.
Image right: This artist concept shows the detection of an atmosphere on Saturn's icy moon Enceladus. Image credit: NASA/JPL