The Cassini space probe has detected the consequences of an immense storm on Saturn almost two years after it had been spotted. Cassini discovered this rare storm in the northern hemisphere of the planet on December 5, 2010 and the observation went on for several months. In time, its visible signs disappeared but the composite infrared spectrometer (CIRS), one of the spacecraft’s instruments, showed that there are still effects from the storm.

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The “Great Springtime Storm” as it this immense storm on Saturn was called, had a really huge size, with a length of many thousands of kilometers. This type of storm happens on Saturn once every 30 Earth years, or once every Saturn year. It’s therefore the first time that a storm of that type has been studied with instruments so advanced by the space probe Cassini but also from various telescopes on Earth such as the Very Large Telescope (VLO) of the European Southern Observatory (ESO) in Chile and NASA’s Infrared Telescope Facility on Mauna Kea in Hawaii.

In 2011, the visible effects of the storm disappeared but the Cassini spacecraft has detected an increase in the temperature of the stratosphere of Saturn of 83 degrees Kelvin (150 degrees Fahrenheit) above average. Researchers at NASA’s Goddard Space Flight Center have detected a huge increase in ethylene gas, whose origin is currently a mystery because it usually isn’t present on Saturn.

Usually, that part of the atmosphere of Saturn is very stable so a temperature increase of this kind is an extraordinary phenomenon. Only infrared instruments allow us to see what happened after the visible effects of the “Great Springtime Storm” have disappeared. In late April 2011, two warm vortexes started emerging then they merged into a huge vortex that for a brief period was larger than the famous Great Red Spot on Jupiter. The two phenomena have some similarities but there seem to be too many differences.

Scientists expect that now the vortex will slowly fade away over the next months but they can’t rule out more surprises. The observation of this phenomenon continues to better understand the processes that occur in the atmosphere of Saturn and the other gas giant planets.