Astronomers have known for some time that Saturns rings consist mostly of ice. But Cassini has exposed some additional components. The so-called F ring and a gap between the A and B rings known as the Cassini Division both contain mysterious dark particles, or "dirt." Intriguingly, this unknown impurity resembles dark material spotted on another of Saturn's moons, Phoebe, bolstering the hypothesis that the rings might themselves be the remnants of a moon. In addition, the spacecraft's ultraviolet imaging instrument found large amounts of oxygen at the edge of the rings--possibly the result of a recent collision. (In the above image, the "dirty" Cassini Division appears in light red at the left; the icy A ring appears in turquoise. The lone red band in the A ring is called the Encke gap.)
In a flyby of Titan--at a closest distance of 210,600 miles--Cassini's visible and infrared mapping spectrometer penetrated the orange moon's dense atmosphere, revealing mineral and chemical features. "At some wavelengths, we see dark regions of relatively pure water ice and brighter regions with a much higher amount of non-ice materials, such as simple hydrocarbons. This is different from what we expected. It's preliminary, but it may change the way we interpret light and dark areas on Titan," says Cassini scientist Kevin Baines of the Jet Propulsion Laboratory. "A methane cloud is visible near the South Pole. It's made of unusually large particles compared to the typical haze particles surrounding the moon, suggesting a dynamically active atmosphere there." Future flybys will pass much closer to the moon--as close as 590 miles--enabling high-resolution mapping of the surface.
