Saturn's Rings, in Color

Newly fleshed-out data from NASA's Cassini spacecraft include this faux-color, ultraviolet image of portions of Saturn's C and B rings, which shows their clear compositional variation. The red regions to the left represent some as yet unknown dirty substance, while the turquoise regions to the right are composed of relatively pure ice chunks. The dirt bears striking resemblance to material that Cassini detected on Saturn's moon Phoebe, suggesting that the rings may, like Phoebe, have origins in the outer solar system.

Cassini also sent back visible and infrared images of the surface of Saturn's giant moon Titan, which is normally obscured by a heavy nitrogen-and-methane atmosphere. To their surprise, scientists discovered that previously observed dark patches are not hydrocarbon lakes, as was thought. Rather, they are areas of relatively pure water ice, while hydrocarbons likely exist in the brighter regions.

The spacecraft will spend the next four years orbiting Saturn, studying its rings, atmosphere, and moons. On Dec. 25, Cassini will dispatch a probe to the surface of Titan, where scientists hope to find chemical clues to the conditions faced by early life on Earth. With a price tag of $3 billion, Cassini is the most elaborate and expensive robotic interplanetary mission NASA has ever undertaken.