Rain from Saturn’s rings may explain dark patterns in the planet’s atmosphere

Los Angeles Times : Saturn’s rings are known to be made mostly of ice. Some of that ice is ionized by sunlight and pulled out of the rings by the planet’s magnetic field to fall on the planet as “rain.” James O’Donoghue of the University of Leicester in the UK and his colleagues used images from the Keck Observatory in Hawaii to examine the phenomenon. They found that the amount of ring rain was much higher than previously believed and that it may cause the patterns of dark areas often seen on the planet’s surface in IR wavelengths. When the ionized ice reaches the atmosphere, it reacts with and neutralizes triatomic hydrogen ions and darkens those areas. The resulting pattern of dark areas reproduces the general structure of the rings. The discovery is the first significant interaction discovered between a planet and its rings, and it poses further questions such as whether the rain will eventually lead to the destruction of the rings themselves.