Ever since the NASA/ESA Cassini spacecraft swung into orbit around the majestic ringed Saturn six years ago, we’ve been treated to hundreds of breathtaking close-ups.
But this week NASA released a movie that captures a living planet, rather the just another postcard glamor shot. Resembling camera flashes going off at a concert, super-bolts of lighting can be seen blasting off from deep inside the giant planet’s billowing cloud tops. Add to that a truly alien soundtrack of the crackle of radio waves emitted by each lightning burst.
The frames in the video were obtained over only 16 minutes on Nov. 30, 2009. The super-flashes lasted less than one second, yet unleashed enough electricity to fry an entire state.
Even though the snapshots are black and white, and the view is subdued, illuminated only by “ring-light,” I am nevertheless mesmerized by it. Though Saturn is one billion miles away, it suddenly seems a lot closer. I can imagine being there and witnessing a phenomenon that is familiar on Earth: the simple plasma physics of lightning, but on a gargantuan scale.
Given Saturn’s turbulent atmosphere, lightning is no surprise. But actually seeing it exploding inside continent-sized cloud tops gives a new sense of intimacy with a world that will likely be forever beyond the reach of humans. The super-flashes are half the width of Arizona and unleash at least 10,000 times more energy than their wimpy cousins on Earth.
It’s fascinating to think that the scene is being illuminated by Saturn’s rings reflecting light from the distant sun, which glows at 1/100 the brightness as seen from Earth. I immediately imagined skimming over the Saturnian cloud tops in an orbit so low that the brilliant rings arc overhead in the sky, while the cloud-fantasy landscape below me flashes as if it’s being carpet-bombed by alien invaders.
Cassini has heard the radio crackle of lighting on Saturn before, but it hadn’t seen the flashes because the fill lighting from the rings is too bright. These images were taken just a few months after the equinox on Saturn and so the rings were tilted edge-on to the sun and therefore dimmer than usual.
Mysteriously, lightning storms on Saturn usually occur about 35 degrees south of Saturn’s equator in a place scientists call “Storm Alley.” Unlike Earth, the internal energy of Saturn powers the storms. Their vertical convection of towering water-clouds carries heat up from the interior.
As Carl Sagan often mused, we are the very first generation in human history to see these planetary phenomena. Since antiquity, Saturn was a pinpoint of light. And, after the telescope was invented, it was simply a staid giant. But Cassini has unveiled a dynamic and perplexing world of wonder. There will simply never be another intense period of solar system revelations like this for the rest of human history. We live in extraordinary times.
