The top left image shows the vortex's most turbulent activity captured by Cassini's imaging cameras on Jan. 11, 2011. It was centered around 54 degrees west longitude and 35 degrees north latitude. At the time, it was the largest vortex ever observed in Saturn's troposphere, which is the layer of the atmosphere where weather occurs. It measured up to 7,500 miles (12,000 kilometers) across. This is comparable in size to the giant storm on Jupiter known as Oval BA, though Oval BA and Jupiter's more famous storm – the Great Red Spot – are not thunder-and-lightning storms. Jupiter’s vortices are known for their stability and longevity. Precursors to Oval BA formed in the 1930s, and evolved into what finally became Oval BA in the late 1990s. The Great Red Spot has been in existence at least since 1879, and possibly since 1664. Jupiter and Saturn are similar in many respects. However, why Jupiter’s vortices are long-lived and why Saturnian ones are so short remain a mystery.