The 2010-2011 planet-circling storm on Saturn.
The Cassini spacecraft (which has been orbiting Saturn since 2004) captured the first images of this storm, which formed in Saturn's northern hemisphere in late December 2010. Storms on Saturn are a cyclical phenomenon, coming every 20 to 30 years.
This storm became so powerful that it stretched around the entire planet Saturn. The storm shot plumes of gas high into Saturn's atmosphere for months.
This image was taken on February 25, 2011, about 12 weeks after the storm began.