The largest storm seen on Saturn in more than 21 years has now been encircling the planet for a record-breaking 200 days.

First appearing as a tiny blemish on Dec. 5, 2010, the storm is still going strong today, surpassing the ringed giant's previous longest tempest, which lasted 150 days back in 1903. NASA’s Cassini spacecraft, in orbit around Saturn, has given astronomers a front-seat view of this enormous maelstrom and provided valuable data.

From its humble beginnings, the storm has grown to engulf the entire area between Saturn’s 30th and 51st north latitudes. From north to south, the tempest stretches about 9,000 miles — greater than diameter of the Earth — and covers two billion square miles, or eight times the surface area of our planet.

Above:

The storm marches through the planet's atmosphere in the top right of this false-color mosaic from Cassini. Red and orange colors in this view indicate clouds that are deep in the atmosphere. Yellow and green colors, most noticeable along the top edge of the view, indicate intermediate clouds. White and blue indicate high clouds and haze. The rings appear as a thin horizontal line of bright blue.

Image: NASA/JPL-Caltech/Space Science Institute