Saturn's northern hemisphere has developed a bizarre sequence of cloud clearings that resembles a string of pearls. The Cassini spacecraft's visual and infrared spectrometer acquired the image, a snapshot of the planet's thermal glow. Stretching across 60,000 kilometers are more than 24 regularly spaced circular gaps in the clouds, which appear darker in the image because they trap more infrared light. This is the first such formation observed on the gaseous planet. Researchers plan to study it in hopes of better understanding Saturn's deep circulation system. If it extends all the way around the planet, it may represent a large planetary wave. A group reported the find last week at a meeting of the American Astronomical Society.