Over the years, passing spacecraft have observed mystifying weather patterns at the poles of Jupiter and Saturn. The two planets host very different types of polar vortices, which are huge atmospheric whirlpools that rotate over a planet’s polar region. On Saturn, a single massive polar vortex appears to cap the north pole in a curiously hexagonal shape, while on Jupiter, a central polar vortex is surrounded by eight smaller vortices, like a pan of swirling cinnamon rolls.

Given that both planets are similar in many ways — they are roughly the same size and made from the same gaseous elements — the stark difference in their polar weather patterns has been a longstanding mystery.

Now, MIT scientists have identified a possible explanation for how the two different systems may have evolved. Their findings could help scientists understand not only the planets’ surface weather patterns, but also what might lie beneath the clouds, deep within their interiors.

In a study appearing this week in the Proceedings of the National Academy of Sciences, the team simulates various ways in which well-organized vortex patterns may form out of random stimulations on a gas giant. A gas giant is a large planet that is made mostly of gaseous elements, such as Jupiter and Saturn. Among a wide range of plausible planetary configurations, the team found that, in some cases, the currents coalesced into a single large vortex, similar to Saturn’s pattern, whereas other simulations produced multiple large circulations, akin to Jupiter’s vortices.

After comparing simulations, the team found that vortex patterns, and whether a planet develops one or multiple polar vortices, comes down to one main property: the “softness” of a vortex’s base, which is related to the interior composition. The scientists liken an individual vortex to a whirling cylinder spinning through a planet’s many atmospheric layers. When the base of this swirling cylinder is made of softer, lighter materials, any vortex that evolves can only grow so large. The final pattern can then allow for multiple smaller vortices, similar to those on Jupiter. In contrast, if a vortex’s base is made of harder, denser stuff, it can grow much larger and subsequently engulf other vortices to form one single, massive vortex, akin to the monster cyclone on Saturn.

“Our study shows that, depending on the interior properties and the softness of the bottom of the vortex, this will influence the kind of fluid pattern you observe at the surface,” says study author Wanying Kang, assistant professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “I don’t think anyone’s made this connection between the surface fluid pattern and the interior properties of these planets. One possible scenario could be that Saturn has a harder bottom than Jupiter.”

The study’s first author is MIT graduate student Jiaru Shi.

Spinning up

Kang and Shi’s new work was inspired by images of Jupiter and Saturn that have been taken by the Juno and Cassini missions. NASA’s Juno spacecraft has been orbiting around Jupiter since 2016, and has captured stunning images of the planet’s north pole and its multiple swirling vortices. From these images, scientists have estimated that each of Jupiter’s vortices is immense, spanning about 3,000 miles across — almost half as wide as the Earth itself.

The Cassini spacecraft, prior to intentionally burning up in Saturn’s atmosphere in 2017, orbited the ringed planet for 13 years. Its observations of Saturn’s north pole recorded a single, hexagonal-shaped polar vortex, about 18,000 miles wide.

“People have spent a lot of time deciphering the differences between Jupiter and Saturn,” Shi says. “The planets are about the same size and are both made mostly of hydrogen and helium. It’s unclear why their polar vortices are so different.”

Shi and Kang set out to identify a physical mechanism that would explain why one planet might evolve a single vortex, while the other hosts multiple vortices. To do so, they worked with a two-dimensional model of surface fluid dynamics. While a polar vortex is three-dimensional in nature, the team reasoned that they could accurately represent vortex evolution in two dimensions, as the fast rotation of Jupiter and Saturn enforces uniform motion along the rotating axis.

“In a fast-rotating system, fluid motion tends to be uniform along the rotating axis,” Kang explains. “So, we were motivated by this idea that we can reduce a 3D dynamical problem to a 2D problem because the fluid pattern does not change in 3D. This makes the problem hundreds of times faster and cheaper to simulate and study.”

Getting to the bottom

Following this reasoning, the team developed a two-dimensional model of vortex evolution on a gas giant, based on an existing equation that describes how swirling fluid evolves over time.

“This equation has been used in many contexts, including to model midlatitude cyclones on Earth,” Kang says. “We adapted the equation to the polar regions of Jupiter and Saturn.”

The team applied their two-dimensional model to simulate how fluid would evolve over time on a gas giant under different scenarios. In each scenario, the team varied the planet’s size, its rate of rotation, its internal heating, and the softness or hardness of the rotating fluid, among other parameters. They then set a random “noise” condition, in which fluid initially flowed in random patterns across the planet’s surface. Finally, they observed how the fluid evolved over time given the scenario’s specific conditions.

Over multiple different simulations, they observed that some scenarios evolved to form a single large polar vortex, like Saturn, whereas others formed multiple smaller vortices, like Jupiter. After analyzing the combinations of parameters and variables in each scenario and how they related to the final outcome, they landed on a single mechanism to explain whether a single or multiple vortices evolve: As random fluid motions start to coalesce into individual vortices, the size to which a vortex can grow is limited by how soft the bottom of the vortex is. The softer, or lighter the gas is that is rotating at the bottom of a vortex, the smaller the vortex is in the end, allowing for multiple smaller-scale vortices to coexist at a planet’s pole, similar to those on Jupiter.

Conversely, the harder or denser a vortex bottom is, the larger the system can grow, to a size where eventually it can follow the planet’s curvature as a single, planetary-scale vortex, like the one on Saturn.

If this mechanism is indeed what is at play on both gas giants, it would suggest that Jupiter could be made of softer, lighter material, while Saturn may harbor heavier stuff in its interior.

“What we see from the surface, the fluid pattern on Jupiter and Saturn, may tell us something about the interior, like how soft the bottom is,” Shi says. “And that is important because maybe beneath Saturn’s surface, the interior is more metal-enriched and has more condensable material which allows it to provide stronger stratification than Jupiter. ”

"Because Jupiter and Saturn are otherwise so similar, their different polar weather has been a puzzle,” says Yohai Kaspi, a professor of geophysical fluid dynamics at the Weizmann Institute of Science, and a member of the Juno mission’s science team, who was not involved in the new study. “The work by Shi and Kang reveals a surprising link between these differences and the planets’ deep interior ‘softness’, offering a new way to map the key internal properties that shape their atmospheres."

This research was supported, in part, by a Mathworks Fellowship and endowed funding from MIT’s Department of Earth, Atmospheric and Planetary Sciences.

“I went into the military right after high school, mostly because I didn’t really see the value of academics,” says Air Force veteran and MIT sophomore Justin Cole.

His perspective on education shifted, however, after he experienced several natural disasters during his nine years of service. As a satellite systems operator in Colorado, Cole volunteered in the aftermath of the 2013 Black Forest fire, the state’s most destructive fire at the time. And in 2018, while he was leading a team in Okinawa conducting signal-monitoring work on communications satellites, two Category 5 typhoons barreled through the area within 26 days.

“I realized, this climate stuff is really a prerequisite to national security objectives in almost every sense, so I knew that school was going to be the thing that would help prepare me to make a difference,” he says. In 2023, after leaving the Air Force to work for climate-focused nonprofits and take engineering courses, Cole participated in an intense, weeklong STEM boot camp at MIT. “It definitely reaffirmed that I wanted to continue down the path of at least getting a bachelor’s, and it also inspired me to apply to MIT,” he says. He transferred in 2024 and is majoring in climate system science and engineering.

“It’s a lot like the MIT experience”

MIT runs the boot camp every summer as part of the nonprofit Warrior-Scholar Project (WSP), which started at Yale University in 2012. WSP offers a range of programming designed to help enlisted veterans and service members transition from the military to higher education. The academic boot camp program, which aims to simulate a week of undergraduate life, is offered at 19 schools nationwide in three areas: business, college readiness, and STEM.

MIT joined WSP in 2017 as one of the first three campuses to offer the STEM boot camp. “It was definitely rigorous,” Cole recalls, “not getting tons of sleep, grinding psets at night with friends … it’s a lot like the MIT experience.” In addition to problem sets, every day at MIT-WSP is packed with faculty lectures on math and physics, recitations, working on research projects, and tours of MIT campus labs. Scholars also attend daily college success workshops on topics such as note taking, time management, and applying to college. The schedule is meticulously mapped out — including travel times — from 0845 to 2200, Sunday through Friday.

Michael McDonald, an associate professor of physics at the Kavli Institute for Astrophysics and Space Research, and Navy veteran Nelson Olivier MBA ’17 have run the MIT-WSP program since its inception. At the time, WSP wanted to expand its STEM boot camps to other universities, so a Yale astrophysicist colleague recruited McDonald. Meanwhile, Olivier’s former Navy SEAL Team THREE teammate — who happened to be the WSP CEO — convinced Olivier to help launch the program while he was at the MIT Sloan School of Management, along with classmate Bill Kindred MBA ’17.

Now in its 10th year, MIT-WSP has hosted over 120 scholars, 93 percent of whom have gone on to attend schools like Stanford University, Georgetown University, University of Notre Dame, Harvard University, and the University of California at Berkeley. MIT-WSP alumni who have graduated now work at employers such as Meta, Price Waterhouse Coopers, Boeing, and BAE Systems.

Translating helicopter repairs to Newton’s laws

McDonald has a lot of fun teaching WSP scholars every summer. “When I pose a question to my first-year physics class in September, no one wants to meet my eyes or raise their hand for fear of embarrassing themselves,” he says. “But I ask a question to this group of, say, 12 vets, and 12 hands shoot up, they are all answering over each other, and then asking questions to follow up on the question. They are just curious and hungry, and they couldn’t care less about how they come off. … As a professor, it’s like your dream class.”

Every year, McDonald witnesses a predictable transformation among the scholars. They start off eager enough, however “by Tuesday, they are miserable, they’re pretty beaten down. But by the end of the week, they’re like, ‘I could do another week,’” he says.

Their confidence grows as they recognize that, while they may not have taken college courses, their military experience is invaluable. “It’s just a matter of convincing these guys that what they are already doing is what we are looking for. We have guys that say, ‘I don’t know if I can succeed in an engineering program,’ but then in the field, they are repairing helicopters. And I’m like, ‘Oh no, you can do this stuff!’ They just need to understand the background of why that helicopter that they are building works.”

Olivier agrees. “The enlisted veteran has a leg up because they’ve already done this before. They are just translating it from either fixing a radio or messing around with the components of a bomb to understanding Newton’s laws. That’s a thing of beauty, when you see that.”

Fostering a virtuous cycle

While just seeing themselves succeed at MIT-WSP helps instill confidence among scholars, meeting veterans who have made the leap into academia has a multiplier effect. To that end, the WSP organization provides each academic boot camp with alumni, called fellows, to teach college success workshops, provide support, and share their experiences in higher education.

“When I was at boot camp, we had two WSP fellows who were at Columbia, one at Princeton, and one who just got accepted to Harvard,” Cole recalls. “Just seeing people existing at these institutions made me realize, this is a thing that is doable.” The following summer, he became a fellow as well.

Former Marine Corps communications operator Aaron Kahler, who attended MIT-WSP in 2024, particularly recalls meeting a veteran PhD student while the group toured the neuroscience facility. “It was really cool seeing instances of successful vets doing their thing at MIT,” he says. “There were a lot more than we thought.”

Over the years, McDonald has made an effort to recruit more MIT veterans to staff the program. One of them is Andrea Henshall, a retired major in the Air Force and a PhD student in the Department of Aeronautics and Astronautics. After joining the Ask Me Anything panel a few years ago, she’s become increasingly involved, presenting lectures, mentoring participants, offering tours of the motion capture lab where she conducts experiments, and informally mentoring scholars.

“It’s so inspiring to hear so many students at the end of the week say, ‘I never considered a place like MIT until the boot camp, or until somebody told me, hey, you can be here, too.’ Or they see examples of enlisted veterans, like Justin, who’ve transitioned to a place like MIT and shown that it’s possible,” says Henshall.

At the conclusion of MIT-WSP, scholars receive a tangible reminder of what’s possible: a challenge coin designed by Olivier and McDonald. “In the military, the challenge coin usually has the emblem of the unit and symbolizes the ethos of the unit,” Olivier explains. On one side of the MIT-WSP coin are Newton’s laws of motion, superimposed over the WSP logo. MIT's “mens et manus” (“mind and hand”) motto appears on the other side, beneath an image of the Great Dome inscribed with the scholar’s name.

“As you go into Killian Court you see all the names of Pasteur, Newton, et cetera, but Building 10 doesn’t have a name on it,” he says. “So we say, ‘earn your space there on these buildings. Do something significant that will impact the human experience.’ And that’s what we think each one of these guys and gals can do.”

Kahler keeps the coin displayed on his desk at MIT, where he’s now a first-year student, for inspiration. “I don’t think I would be here if it weren’t for the Warrior-Scholar Project,” he says.