Jupiter has no tilt as it moves, so its poles have never been visible from our planet. But in the past two years, with NASA’s Juno spacecraft, researchers have gotten a good look at the top and bottom of the planet for the first time. What they found astounded them: bizarre geometric arrangements of storms, each arrayed around one cyclone over the north and south poles.
This composite image, derived from data collected by the JIRAM instrument aboard NASA’s Juno orbiter, shows the central cyclone at Jupiter’s north pole and the eight cyclones that encircle it. JIRAM collects data in infrared, and the colors in this composite represent radiant heat: the yellow (thinner) clouds are about 9 degrees Fahrenheit (minus 13 degrees Celsius) in brightness temperature and the dark red (thickest) are around minus 181 degrees Fahrenheit (83 degrees Celsius). Image credit: NASA / JPL-Caltech / SwRI / ASI / INAF / JIRAM.
Juno launched in 2011 with the ambitious mission of finally seeing beneath the dense clouds covering Jupiter.
On July 4, 2016, it finally reached the planet’s orbit. Since then it’s been orbiting the giant planet, taking pictures and measuring Jupiter’s profile in infrared, microwave, ultraviolet, gravity and magnetism — and answering questions scientists have had about the planet for decades. One of these was the question of what lay at its elusive poles.
When Juno co-investigator Alberto Adriani and colleagues got beautiful images from Juno’s Jovian Infrared Auroral Mapper (JIRAM) instrument, they were stunned: Jupiter’s poles were a stark contrast to the more familiar orange and white belts and zones encircling the gas giant at lower latitudes.
“Jupiter’s north pole is dominated by a central cyclone surrounded by eight circumpolar cyclones with diameters ranging from 2,500 to 2,900 miles (4,000 to 4,600 km) across,” the researchers said.
“Its south pole also contains a central cyclone, but it is surrounded by five cyclones with diameters ranging from 3,500 to 4,300 miles (5,600 to 7,000 km) in diameter.”
Almost all the polar cyclones, at both poles, are so densely packed that their spiral arms come in contact with adjacent cyclones.
“Prior to Juno we did not know what the weather was like near Jupiter’s poles. Now, we have been able to observe the polar weather up-close every two months,” Dr. Adriani said.
“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 220 mph (350 kph). 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.”
This computer-generated image shows the structure of the cyclonic pattern observed over Jupiter’s south pole. Like in the North, Jupiter’s south pole also contains a central cyclone, but it is surrounded by five cyclones with diameters ranging from 3,500 to 4,300 miles (5,600 to 7,000 km) in diameter. Almost all the polar cyclones (at both poles), are so densely packed that their spiral arms come in contact with adjacent cyclones. The data used in generating this image was collected by the JIRAM instrument aboard Juno during the fourth Juno pass over Jupiter on February 2, 2017. Image credit: NASA / JPL-Caltech / SwRI / ASI / INAF / JIRAM.
The manner in which the cyclones persist without merging and the process by which they evolve to their current configuration are currently unknown to the scientists.
“They are extraordinarily stable arrangements of such chaotic elements. We’d never seen anything like it,” said Dr. Morgan O’Neill, a postdoctoral researcher at the University of Chicago.
“In the 1990s, scientists observed a similar behavior as they used electrons to simulate a frictionless, turbulent 2D fluid as it cools. Instead of merging, which tends to happen in such 2D flows, small vortices would clump together and form equally spaced arrays, or ‘vortex crystals,’ around a center.”
“It’s not yet clear whether the same physics underlies both these behaviors, but it is tantalizing,” she said.
“The next step is: can you create a model that builds a virtual planet and predicts these flows? With further studies, we can understand the forces at play in the swirling storms.”
The study is published in the March 8, 2018 issue of the journal Nature as part of a set of four papers dedicated to new observations from the Juno orbiter.
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A. Adriani et al. 2018. Clusters of cyclones encircling Jupiter’s poles. Nature 555 (7695): 216-219; doi: 10.1038/nature25491
