New images from NASA’s Cassini spacecraft chronicle the birth and evolution of the colossal storm that ravaged the northern face of Saturn for nearly a year. New animations show the storm from its emergence as a tiny spot in a single image almost one year ago, on December 5, 2010, through its subsequent growth into a storm so large it completely encircled the planet by late January 2011. The monster tempest, which extended north-south approximately 9,000 miles (15,000 kilometers), is the largest seen on Saturn in the past two decades and is the largest by far ever observed on the planet from an interplanetary spacecraft. The storm’s 200-day active period also makes it the longest-lasting planet encircling storm ever seen on Saturn.
According to Kunio Sayanagi, a Cassini imaging team associate and planetary scientist at the University of California, Los Angeles this storm is a completely different kind of beast compared to anything they saw on Saturn previously with Cassini. The fact that such outbursts are episodic and keep happening on Saturn every 20 to 30 years or so is telling us something about deep inside the planet, but they have yet to figure out what it is. Current plans to continue the mission through 2017 will provide opportunities for Cassini to witness further changes in the planet’s atmosphere as the seasons progress to northern summer.