This collection of images from the Cassini spacecraft orbiting Saturn shows the evolution of a massive thunder storm that circled all the way around the planet and fizzled out when it ran into its own tail. The storm was first detected on 5 December, 2010. It developed a head of bright clouds which began rapidly moving west and also spawned a much slower moving clockwise-spinning vortex.

The bright clouds at the head of the storm are indicated with red triangles. Yellow triangles mark the vortex.

The top image was taken not long after the start of the storm on 22 January, 2011. It shows the bright head of the storm just ahead of the vortex by about 40,000 km. The next image from 5 May shows that the head of the storm had traveled around the planet and started approaching the vortex from the east. The storm’s body had stretched over 220,000 km, and the head was within about 80,000 km of the vortex. That image also shows that the  vortex was losing steam compared to the head of the storm. The third image was taken on 14 June. The head of the storm had made its way roughly 290,000 km—almost entirely around the planet, and it was about to catch up with the vortex. The head of the storm was just 14,000 km east of the vortex. The bottom image, from 12 July, 2011, shows that the storm fizzled once the head and vortex met. Only the vortex remains; the bright cloud has disappeared. By late August, the storm stopped generating lightning for good.

These are false color images with the colors denoting the altitudes of the clouds. Red data is from a wavelength of radiation that penetrates the atmosphere deep down to the top of the tropospheric cloud deck (750 nm). Green represents an intermediate wavelength above the troposphere (728 nm). Blue is for a wavelength that penetrates only to the top of tropospheric haze (890 nm). White is for thick clouds at high altitudes.

Image Credit: NASA