Seeing Jupiter and its cloud belts the other morning got me curious about what NASA’s Juno spacecraft has been up to. Juno swings around Jupiter every 53 days on a highly elongated orbit that reaches as far as 5 million miles (8.1 million km) from the planet to only 2,600 miles (4,200 km) above its cloud tops. The detailed images it captures during those close shaves will make your eyes pop.
The spacecraft completed its 24th close flyby on Feb. 17 and will perform the next on April 10. My favorite way to track down recent and archival images taken by NASA space missions is through their photojournal sites. These come from the Juno Photojournal. I’m convinced if the painter Van Gogh were alive today he’d be captivated by Jupiter, a planet with a style similar to his own. The artist’s bright swirls of color imprinted with the strokes of his paintbrush mimic the wild vortices that crowd the planet’s polar regions.
Instead of using cadmium yellow and Prussian blue Jupiter mixes ammonia, methane, hydrogen, helium and dashes of sulfur and phosphorous to make its color palette. There are hundreds of vortices but they come in just two varieties: cyclones or low pressure centers and anticyclones or high pressure centers. And they’re whopping huge! Those near the planet’s north pole span 2,500 miles to 2,900 miles (4,000 to 4,600 kilometers) across with winds up to 220 miles an hour (350 kph). The biggest — from 3,500 to 4,300 miles (5,600 – 6,900 km) wide — jostle cheek to jowl around the south pole.
The massive storms are caused by convection when warm, moist air rises up from deeper down in Jupiter’s atmosphere and condenses into clouds in the cold upper atmosphere, similar to how thunderstorms form on Earth. The planet’s rapid spin combined with powerful jet-stream-like winds coil the condensing gases into whirlpools. Jupiter’s spin also torques the mammoth cells and nudges them toward the poles where they accumulate in abundance.
We’ve observed a variety of vortices practically since the invention of telescope but had no idea of their number and longevity (lifetimes range from several days to hundreds of years) until Juno was able to look over the top and bottom of the planet at its storm-rich polar regions. Juno also discovered water within the clouds along Jupiter’s equator, a finding that will help scientists better understand its meteorology.
You can see Jupiter any morning at dawn now through a small telescope and marvel for yourself at its colorful and dynamic clouds. We share that with the solar system’s biggest planet. Althought the scale may be grander the underlying causes — heat, condensation, wind and rotation — are familiar to every earthling.