Cassini scientists waited years for the right conditions to produce the first movie that shows lightning on another planet -- Saturn.


We don't really know on Earth why you get thunderstorms at the rate we get them.
Andy Ingersoll, Cassini Imaging Team Member:
We look at Saturn. They're very infrequent.

Ulyana Dyudina
Cassini Imaging Team Associate:
We were pretty sure that lightning existed but we actually couldn't see it. It's a giant planet with a huge atmosphere and there should be a lot of weather there. We had heard the lightning on the radio instrument on Cassini but you hear static on the radio signal but you can't pinpoint where it's coming from.

We had to use a synthetic noise because the actual noise that the radio instrument is picking up is beyond the human ear. So we picked a noise that sounded like an electrical discharge, in other words, a big spark. That's
what lightning is.

Approximated sound
Based on Cassini radio wave data

It's taken us a long time to see the lightning and that's because normally the night side of Saturn is very bright because the rings are shining down all the time. The night side of Saturn is brighter than Earth under a full moon. The strategy we chose was to look at the equinox and the equinox is when the sun is in the ring plane. So it doesn't illuminate the rings that much and rings become dark and night becomes dark.

When it finally got dark, dark enough at night, we pointed the cameras there and wonders of wonders there were
lightning flashes. And we took a series of pictures. And in one picture there'd be no lightning flash and in the next picture there'd be a lightning flash. And at the same time you hear the noise over the radio instrument.

Text: Movie of lightning flashes with approximated sound

And we actually saw it.
I didn't believe it

The lightning storms on Saturn are very much like lightning on Earth. You get the same strength lightning storms
or thunderstorms. They have the same strength but they're just much less frequent. I'm enjoying the show.

NASA's Jet Propulsion Laboratory, California Institute of Technology

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