Astronomers Galileo Galilei and Giovanni Cassini laid eyes on Jupiter's swirling surface in the 1600s. These early astronomers marveled at the giant planet’s bands and even the Great Red Spot—a storm that has swirled for centuries. Since then, despite countless observations and several successful flybys, our knowledge of the King of Planets still runs skin deep.
But now, researchers are getting their closest look yet. Four separate articles published in the journal Nature parse data from NASA’s Juno probe, giving scientists a peek into the planet’s mysterious interior, reports Jonathan Amos at the BBC. And it's nothing like we imagined.
The Juno probe was launched in 2011 and arrived at Jupiter in 2016, orbiting the solar system’s largest planet ever since. It has snapped our best photos yet of the planet and uses its array of instruments to scrutinize Jupiter's many curious features—magnetosphere, dense atmosphere, roaring winds and all.
In the first two of the new studies, researchers explore the tiny variations in the tug of Jupiter's gravity. The analysis suggests that the atmospheric storm bands swirling around the planet are not just surface features. Instead, they likely extend around 1,860 miles down.
“This solves a long-time mystery,” Juno co-investigator Tristan Guillot from the Côte d'Azur Observatory in France tells Amos. “For over 40 years we didn't know whether the bands would go all the way to the center, or whether they were just skin deep. [1,860 miles] is actually quite deep. It’s 1 percent of the mass of the planet. Jupiter’s very big so it’s about three Earth masses that are involved in this motion.”
While an atmosphere that makes up 1 percent of the planet’s mass may not sound too impressive, George Dvorsky at Gizmodo points out that Earth’s atmosphere makes up less than one millionth the mass of our planet. The new measurements will give researchers a much more detailed view of the planet, helping scientists better understand what might be powering Jupiter’s jet streams and learn more about the planet’s core, structure and origins. "It’s like going from a 2-D picture to a 3-D version in high definition, ” says lead author Yohai Kaspi of the Weizmann Institute of Science, Rehovot, Israel in a press release.
As for Jupiter’s core, this has been an enduring mystery. The third new study, however, is starting to sort this out. The analysis suggests that the interior mass of Jupiter rotates as one single body, unlike its swirling surface. The findings also suggest that the core is likely in a liquid state and is not a solid.
“It is an almost 50-year old puzzle in planetary science that is solved,” Guillot tells Dvorsky. “We didn’t know whether a gaseous planet like Jupiter—but also Saturn, Uranus, Neptune, and giant exoplanets—rotates with zones and belts all the way to the center or whether, on the contrary, the atmospheric patterns are skin-deep. Many lab experiments, numerical simulations had been performed but with no clear picture emerging. Now, thanks to Juno’s amazing accuracy—it measured Jupiter’s gravity field 100 times better than before—we have the ground truth.”
The next revelation from Juno is a series of new photos from its Jovian Infrared Auroral Mapper, an instrument that was able to probe the weather at Jupiter’s poles as deep as 45 miles. The effort revealed an area of closely packed cyclones, some roaring at 220 miles per hour. At the north pole, eight cyclones circle around one central swirl while Juno found five of these whirls around the central cyclone of the south pole.
“Each one of the northern cyclones is almost as wide as the distance between Naples, Italy, and New York City—and the southern ones are even larger than that. They have very violent winds, reaching, in some cases, speeds as great as 220mph,” lead author Alberto Adriani of the Institute for Space Astrophysics and Planetology in Italy tells Amos. “Finally, and perhaps most remarkably, they are very close together and enduring. There is nothing else like it that we know of in the Solar System.”
Juno will likely reveal many more surprising finds about Jupiter as it continues to scan the planet until its mission ends in 2021. “The real question that we’re after is, how did it form?” Scott Bolton, Juno’s principal investigator tells Marina Koren at The Atlantic. “And what does that tell us about how the rest of the solar system formed and how other solar systems form? How are planets really made?”
Since Jupiter is likely the first planet to form in our solar system, figuring out how it came to be will help researchers understand how the rest of the planets—including Earth—lined up around the sun.