Detection of visible lightning on Saturn

Until now, evidence for lightning on Saturn has been indirect - through radio emissions and cloud morphology. Here we report the first visible detection of lightning, on the night side on August 17, 2009 at -36.4 degrees +/- 0.1 degrees planetocentric latitude and 10.6 degrees +/- 0.9 degrees west longitude. No other locations produced lightning detectable by either imaging or radio. The lightning images are consistent with a single cloud flashing once per minute. The visible energy of a single flash is comparable to that on Earth and Jupiter, and ranges up to 1.7 x 10(9) Joules. The diameter of the lightning flashes is similar to 200 km, which suggests the lightning is 125-250 km below cloud tops. This depth is above the base of the liquid H2O-NH3 cloud and may be either in the NH4SH cloud or in the H2O ice cloud. Saturn's lower internal heat transport and likely 5-10 fold enrichment of water largely explain the lower occurrence rate of moist convection on Saturn relative to Jupiter. Citation: Dyudina, U. A., A. P. Ingersoll, S. P. Ewald, C. C. Porco, G. Fischer, W. S. Kurth, and R. A. West (2010), Detection of visible lightning on Saturn, Geophys. Res. Lett., 37, L09205, doi: 10.1029/2010GL043188.