scientists say the storm occurred last year with flashes of lightning brightest in the blue filter of Cassini's imaging camera on March 6, 2011.
According to Space.com
, the storm wrapped completely around Saturn at its peak and it is the longest-lived storm ever seen on the ringed planet. It began in December 2010 and ended in late June 2011
unveiled the new Saturn lightning photos Wednesday. NASA scientists say the images came as a surprise.
Ulyana Dyudina, a Cassini imaging team associate based at the California Institute of Technology in Pasadena, said: “We didn’t think we’d see lightning on Saturn’s day side – only its night side."
The image shows a bluish spot in the middle of swirling clouds. According to NASA
experts, the blue spots indicate flashes of lightning and mark the first time scientists have detected lightning in visible wavelenghts on the side of Saturn illuminated by the Sun.
NASA scientists are still investigating why the blue filter caught the lightning. They believe that it might be that the lightning was really blue or it might be that the short exposure of the camera in the blue filter makes the short-lived lightning easier to see.
But scientists say that the intensity of the flash is comparable to the strongest flashes on Earth. NASA scientists estimate the visible energy alone to be about 3 billion watts lasting for one second.
The flash is about 100 miles (200 kilometers) in diameter when it exits the tops of the clouds. Scientists have deduced from this that lightning bolts originate in the clouds deeper down in Saturn's atmosphere where water droplets freeze.
Multiple flashes in the composite images that show the storm raging around Saturn have been observed. In one composite image scientists recorded five flashes.
According to Linda Spilker, Cassini project scientist based at NASA's Jet Propulsion Laboratory, Pasadena, California, “As summer storm season descends upon Earth’s northern latitudes, Cassini provides us a great opportunity to see how weather plays out at different places in our solar system. Saturn’s atmosphere has been changing over the eight years Cassini has been at Saturn, and we can’t wait to see what happens next.”
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Cassini spacecraft launched in 1997 and has been orbiting Saturn since 2006. According to Space.com
, the spacecraft is currently in an extended mission that is expected to last through 2017.
reports that Saturn is currently visible in Earth's night sky. It can be seen in the western evening sky with Mars and the bright star Spica in July, weather permitting.