Cassini snaps two images of Phoebe from a distance of approximately 20,000 miles, which scientists later turn into this composite image.

Cassini flies by Saturn's moon Phoebe, uncovering evidence that it may be a frozen, 4-billion-year-old artifact. Scientists have concluded that Phoebe is likely a primordial mixture of ice, rock and carbon-containing compounds similar to material seen in Pluto and in one of Neptune's moons, Triton.

Bodies like Phoebe are thought to have been common in the outer reaches of the solar system about 4 1/2 billion years ago. These icy planetesimals (small bodies) formed the building blocks of the outer solar system, and some were incorporated into inner solar system planets Jupiter, Saturn, Uranus and Neptune. During the planet-building process, much of this material was ejected into distant orbits, joining similar bodies to form the Kuiper Belt. Phoebe was left behind, caught in Saturn's orbit.