APOD: 2009 August 9 - Saturn’s Iapetus: Painted Moon:
What has happened to Saturn’s moon Iapetus? Vast sections of this strange world are dark as coal, while others are as bright as ice. The composition of the dark material is unknown, but infrared spectra indicate that it possibly contains some dark form of carbon. Iapetus also has an unusual equatorial ridge that makes it appear like a walnut. To help better understand this seemingly painted moon, NASA directed the robotic Cassini spacecraft orbiting Saturn to swoop within 2,000 kilometers in 2007. Pictured above, from about 75,000 kilometers out, Cassini’s trajectory allowed unprecedented imaging of the hemisphere of Iapetus that is always trailing.
