NASA announced yesterday (July 18, 2012) that the Cassini spacecraft orbiting Saturn Cassini spacecraft has captured images at visible wavelenghths of lightning on the day side of Saturn. This is a first. We had images of lightning on the night side of the planet (and even a movie; see below). But daytime lightning at visible wavelengths – which would need to be “very intense,” according to these scientists – had never been seen. The lightning came in the midst of the great storm that raged on the planet Saturn for much of 2011.
The spacecraft captured images of bluish spots in the middle of swirling storm clouds on Saturn. Those bluish spots are now known to be flashes of daytime lightning.
The intensity of the flash in the image above is comparable to the strongest lightning flashes on Earth. The visible energy alone is estimated to be about 3 billion watts lasting for one second. The flash is approximately 100 miles (200 kilometers) in diameter when it exits the tops of the clouds. From this, scientists deduce that the lightning bolts originate in the clouds deeper down in Saturn’s atmosphere where water droplets freeze. This is analogous to where lightning is created in Earth’s atmosphere.
In composite images that show the band of the storm wrapping all the way around Saturn, scientists have seen multiple flashes. In one composite image, they recorded five flashes, and in another, three flashes.
Saturn’s night side has been known for some time to have lightning flashes. The movie below, which is from 2010, shows lightning on the night side of Saturn, again as captured by Cassini.
This movie – the first of its kind – shows lightning on Saturn’s night side flashing in a cloud that is illuminated by light from Saturn’s rings. There are 16 minutes of observations covered in the 10-second movie.
Bottom line: NASA’s Cassini spacecraft, which has been orbiting Saturn since 2004, has now provided images of daytime lightning on the ringed planet.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.