Jupiter’s stormy weather no tempest in teapot

Jupiter’s turbulence is not just skin deep. The giant planet’s visible storms and blemishes have roots far below the clouds, researchers report in the June 3 Science. The new observations offer a preview of what NASA’s Juno spacecraft will see when it sidles up to Jupiter later this year.

A chain of rising plumes, each reaching nearly 100 kilometers into Jupiter, dredges up ammonia to form ice clouds. Between the plumes, dry air sinks back into the Jovian depths. And the famous Great Red Spot, a storm more than twice as wide as Earth that has churned for several hundred years, extends at least dozens of kilometers below the clouds as well.

Jupiter’s dynamic atmosphere provides a possible window into how the planet works inside. “One of the big questions is what is driving that change,” says Leigh Fletcher, a planetary scientist at the University of Leicester in England. “Why does it change so rapidly, and what are the environmental and climate-related factors that result from those changes?”

To address some of those questions, Imke de Pater, a planetary scientist at the University of California, Berkeley, and colleagues observed Jupiter with the Very Large Array radio observatory in New Mexico. Jupiter emits radio waves generated by heat left over from its formation about 4.6 billion years ago. Ammonia gas within Jupiter’s atmosphere intercepts certain radio frequencies. By mapping how and where those frequencies are absorbed, the researchers created a three-dimensional map of the ammonia that lurks beneath Jupiter’s clouds. Those plumes and downdrafts appear to be powered by a narrow wave of gas that wraps around much of the planet.

The depths of Jupiter’s atmospheric choppiness isn’t too surprising, says Scott Bolton, a planetary scientist at the Southwest Research Institute in San Antonio. “Almost everyone I know would have guessed that,” he says. But the observations do provide a teaser for what to expect from the Juno mission, led by Bolton. The spacecraft arrives at Jupiter on July 4 to begin a 20-month investigation of what’s going on beneath Jupiter’s clouds using tools similar to those used in this study.

The new observations confirm that Juno should work as planned, Bolton says.

By getting close to the planet — just 5,000 kilometers from the cloud tops — Juno will break through the fog of radio waves from Jupiter’s radiation belts that obscures observations made from Earth and limits what telescopes like the Very Large Array can see. But the spacecraft will see only a narrow swath of Jupiter’s bulk at a time. “That’s where ground-based work like the research de Pater has been doing is really essential,” Fletcher says. Observations such as these will let Juno scientists know what’s going on throughout the atmosphere so they can better understand what Jupiter is telling them.