Giant Saturn Storm Revealed

Using a distant spacecraft and a giant telescope, astronomers have unmasked the full ire of a storm so big that it encircles Saturn, a planet nearly ten times bigger than Earth. Astronomers have been watching this northern-hemisphere storm since December 2010, when a bright plume of gas bubbled up to the surface of the gaseous sphere that makes up Saturn.

The disturbance has since expanded by riding easterly winds blowing at about 220 miles an hour. But until now very little has been known about the workings of the storm, its depth, and how it affects the ringed planet. Now a new study, released Thursday by the journal Science, says the Saturn storm is about 370 miles tall, according to observations made both by NASA's Cassini probe and the European Southern Observatory's Very Large Telescope array in Chile. By comparison, thunderstorms on Earth usually top out at a height of 12.5 miles—and none of them circle our entire planet, despite its comparatively small size.

Saturn's New Bright Storm

First spotted by amateurs in Japan around December 9th, Saturn's new storm spans more than 100° of longitude as of January 5th, in the North Tropical Zone (roughly 34° north). This disturbance is not the same one noted by amateurs earlier this year, which appeared at a dynamic southern latitude band nicknamed "Storm Alley."

NASA / JPL / Space Science Inst.Veteran planet-watcher Thomas Dobbins notes the last time such a large storm appeared on Saturn was 1994, but that one had much lower contrast with its surroundings than the current event. This disturbance is easily the brightest feature on the globe — it even rivals the brightness of the planet's ring system. NASA's Cassini spacecraft has a "ringside" seat for the roiling clouds, as seen in the shot at right, which was taken on December 24th and transmitted to Earth on the 27th. Check the mission's website for other high-resolution images of the planet.

Saturn's Rings: Leftovers from a Cosmic Murder?

One of the solar system's most evocative mysteries—the origin of Saturn's rings—may be a case of cosmic murder, new research suggests. The victim: an unnamed moon of Saturn that disappeared about 4.5 billion years ago. The suspect: a disk of hydrogen gas that once surrounded Saturn when its dozens of moons were forming, but has now fled the crime scene. The cause of death: A forced plunge into Saturn. And those spectacular and colorful rings are the only evidence left.

As the doomed moon made its death spiral, Saturn robbed its outer layer of ice, which then formed rings, according to a new theory published online Sunday in the journal Nature. A large disk of hydrogen gas circled Saturn and that helped both create and destroy moons. Large inner moons probably made regular plunges into the planet, pulled by the disk of gas. These death spirals took about 10,000 years and the key to understanding the rings' origins is what happened to them during that time. According to Canup's computer model, Saturn stripped the ice away from a huge moon while it was far enough from the planet that the ice would be trapped in a ring.

Saturn's Strange Propellers Are Clues to Formation

For six years, the Cassini spacecraft has been touring Saturn and its magnificent rings. Unlike previous spacecraft, which have snatched a passing glimpse of the planet on their way to the edges of the solar system, Cassini has beamed back stunningly detailed images year after year. Among the most striking are structures shaped like aircraft propellers. They are the wakes created by unseen moons as they plough through the icy rubble orbiting around Saturn. Dozens of propellers have been spotted in the A-ring, a band 14,000 kilometres wide and only 10 metres deep.

The moons themselves are too small even for Cassini to see directly because they are only a few kilometres to a few hundred metres across. In contrast, their propeller-shaped wakes can be thousands of kilometres long, and some have now been observed orbiting Saturn for several years. They form as a result of a moon's gravity tugging on the surrounding material. The debris inside its orbit, being closer to Saturn, is moving faster, and the perturbation therefore quickly overtakes the moon, creating a long, thin wake ahead of it. This is the leading blade of the propeller. Meanwhile, the material outside the moon's orbit is moving more slowly, creating the trailing blade.