Jupiter’s stormy weather runs deep
A new 3-D map shows ammonia swirling up to far below planet’s clouds
Jupiter, the largest planet in our solar system, is not a calm giant. It’s covered in swirling clouds that form colorful stripes and spots. Those cloud features include the famous Great Red Spot. It’s a storm wider than Earth —one that has been raging for several hundred years. Now scientists have discovered that Jupiter’s turbulence is not just skin deep. The storms and spots that we can see start far below the clouds.
Earth’s clouds are made of water vapor. Jupiter’s, in contrast, are mostly ammonia. And Jupiter’s atmosphere is always changing. That could give scientists a window into how the planet works inside. “One of the big questions is what is driving that [atmospheric] change,” says Leigh Fletcher. He’s a planetary scientist at the University of Leicester in England. “Why does it change so rapidly?” he asks. And how do those changes affect Jupiter’s environment and climate?
To address some of those questions, scientists have been studying Jupiter with an observatory called the Very Large Array in New Mexico. Among those researchers is Imke de Pater. He is a planetary scientist at the University of California, Berkeley. The Very Large Array measures a form of energy called radio waves. Jupiter gives off radio waves because it’s still cooling off from its birth about 4.6 billion years ago. Some of those waves get trapped by ammonia gas in Jupiter’s atmosphere before leaving the planet. Other waves travel through space all the way to Earth. By mapping what absorbs those radio waves, and where, the researchers created a three-dimensional (3-D) map of the ammonia beneath Jupiter’s clouds.
The scientists saw a chain of tall gas plumes. Each plume stretched nearly 100 kilometers below the cloud layer. These plumes carry ammonia upward to form ice clouds. Dry air sinks back down between the plumes. The updrafts and downdrafts seem to be powered by a narrow wave of gas that wraps around much of the planet. And the Great Red Spot, they saw, reaches at least dozens of kilometers below the clouds. The researchers reported their findings in the June 3 Science.
The depth of Jupiter’s turbulence isn’t too surprising, says Scott Bolton. He’s a planetary scientist at the Southwest Research Institute in San Antonio, Texas. “Almost everyone I know would have guessed that,” he says.
But the new observations do hint at what NASA’s Juno mission might find. Juno is a spacecraft due to reach Jupiter on July 4. Then it will start a 20-month investigation of what’s going on beneath Jupiter’s clouds. It will be using tools similar to those used in this study.
Bolton is leading the Juno mission. The new observations confirm that Juno should work as planned, he says.
Juno will get close to the planet — just 5,000 kilometers above the cloud tops. That will let it sneak inside belts of radiation around Jupiter. That radiation makes it hard to study the planet from Earth, and limits what telescopes like the Very Large Array can see.
But the spacecraft will see only a narrow piece of giant Jupiter 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. That way, they can better understand what the spacecraft is telling them about this stormy giant.