Scientists with the National Aeronautics and Space Administration's Cassini-Huygens mission said the storm is the longest continually observed electrical storm ever monitored by Cassini.

Saturn's electrical storms resemble terrestrial thunderstorms but on a much larger scale, NASA said. Storms on Saturn have diameters of several thousand miles and radio signals produced by the lightning are thousands of times more powerful than those produced by terrestrial thunderstorms.

"The electrostatic radio outbursts have waxed and waned in intensity for five months now," said Georg Fischer, an associate with the radio and plasma wave science team at the University of Iowa. "We saw similar storms in 2004 and 2006 that each lasted for nearly a month but this storm is longer-lived by far. And it appeared after nearly two years during which we did not detect any electrical storm activity from Saturn."

Scientists expect the long-lived storm to provide information on the processes powering Saturn's intense lightning activity.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.