Only a month and a half into its long approach to Saturn, the Cassini-Huygens spacecraft captured two storms, each a swirling mass of clouds and gas, in the act of merging.

With diameters close to 1000 kilometres, both storms, which appear as spots in the southern hemisphere, were seen moving westward, relative to the rotation of Saturn's interior, for about a month before they merged on 19-20 March 2004.