Hmmm, that might make a good S.F. book title. Feel free to steal it, just send me a copy when it's published.
Anyway, there's something happening on Saturn:
People who know more than me, and have probably been there say this is a storm, characterized by rapid fire lightning. Look closely and you can see the track of the thing dragged all the way around the planet. If this were a storm, I'd expect it to follow the atmospheric movement and stay more or less in one place.
To me this says "Volcano". Yes, I know Saturn's a gas giant and (probably) doesn't have molten rocks, but so what. Think "low temperature sunspot". The end result is pretty much the same and the footprint would match.