科学美国人60秒:Water Ice Found across Saturn System

Saturn’s rings and moons are a diverse group, but some of their differences are only skin deep. A new analysis of the Saturnian system shows that the planet’s rings and satellites have at least one compositional characteristic in common. They appear uniformly stocked with water ice, dating from their formation in the early solar system.

Researchers examined six years of Saturn observations from NASA’s Cassini orbiter, which can detect ice as well as the colorful contaminants that obscure it, such as iron or hydrocarbons. The inner moons are largely devoid of such coloration, thanks to a fresh coat of icy material that spews out from the moon Enceladus. And the outer moons are dusted with dark stuff, which looks to be debris from Phoebe, a dark-colored lump of a moon.

But underneath those surface differences is a uniform distribution of water ice, which seems to reflect the common origins of the moons and rings billions of years ago. The research appears in the Astrophysical Journal. [Gianrico Filacchione et al., The Radial Distribution of Water Ice and Chromophores across Saturn's System]

The rings and moons, polluted and tinted though they may be now, therefore appear to preserve a record of their beginnings, frozen in time and space.

—John Matson