Astronomers glimpse lightning storms on giant planet
Snap, crackle, pop!
Cameras aboard the Cassini spacecraft have taken the first images of lightning bolts on Saturn. Movies of the storms, released by NASA on April 13, feature a soundtrack of crackling radio waves that were recorded simultaneously with the bolts. One of the storms, which lasted 10 months, is the longest on record in the solar system and generated as much power as most powerful storms on Earth.
“This is the first time we have seen the lightning and pinpointed its location” on Saturn, says Cassini scientist Andy Ingersoll of Caltech.
Up until now, he notes, Cassini had only listened to storms with its radio wave and plasma-wave detectors. But as Saturn approached its equinox on August 10, 2009, when the planet’s rings are edge-on to the sun and the night side of the planet is dimmest, lightning bolts became visible for the first time.
It’s like viewing the night sky on a moonless night, explains Cassini researcher Ulyana Dyudina, also of Caltech.
The first images were taken in August 2009 but more were recorded in November and December. Curiously, Dyudina says, the storm clouds tend to pop up in a single region centered at about 35 degrees south latitude.
With sunlight that reaches Saturn is only 1 percent as strong as that hitting Earth, Cassini scientists expected lightning storms on the ringed planet to be either weaker or less frequent than their Earthly counterparts — or both.
Generally, Saturnian lightning storms are less frequent, Ingersoll says, “but it would have been hard to predict in advance, since we don't understand lightning very well even on Earth.”
This movie of lightning on Saturn’s night side, the first recording of a storm on the planet, is accompanied by radio crackles recorded simultaneously with the flashes.
Credit: JPL-Caltech/NASA, SSI