Scientists Strive to Explain the Strange Weather on Other Planets

What the swirling storms on alien worlds can tell us about the climate on Earth.

A somewhat alarming new phrase entered the American lexicon when parts of the United States were plunged into an especially bitter deep freeze in January 2014: “polar vortex.” 

News reports cast the polar vortex as a previously unknown phenomenon that had suddenly descended upon the country. “What is the polar vortex and why is it doing this to us?” asked NPR, echoing the complaints of increasingly fed-up Americans. 

Despite the heightened public awareness, however, a polar vortex is nothing new (and what most of us refer to as a polar vortex might not actually be one). Scientists first identified a vortex—a mass of whirling air or fluid—high above Earth’s North Pole in the early 1950s, and they later discovered that vortices appear every winter over both the North and South Pole. 

Space exploration missions have revealed that polar vortices aren’t uncommon beyond Earth. They’ve been observed throughout the solar system, on every planet and moon that has enough of an atmosphere—from the roasting skies of Venus to the frigid poles of remote Uranus and Neptune. 

Extraterrestrial vortices take many forms. Jupiter’s look like pans of sweet rolls. A hexagon bounds Saturn’s northern polar vortex. And Martian vortices act similar to Earth’s, spinning to life each winter, but with a difference: instead of a beanie-shaped covering atop the pole, the vortex forms a doughnut that whips around the pole like a hula-hoop. 

Scientists study these extraterrestrial vortices mainly to learn about the planets and moons themselves. But their work can also yield new insights into Earth’s atmosphere—how it works, how it has evolved, and how changing conditions might impact our planet’s climate in the coming decades. 

“I think the main thing we learn from studying the polar vortices and other atmospheric phenomena of other planets is the sheer range of possibilities available in the natural world,” says Paul Streeter, a planetary scientist at the Open University in England. 

“We have an interesting suite of planets to study,” notes Jennifer Whitten, a planetary geologist at the National Air and Space Museum’s Center for Earth and Planetary Studies. “And from those, we can learn about Earth and its atmospheric evolution. In our own solar system, we have so many examples of what didn’t go the way Earth went. That shows us how unique Earth is. There’s real beauty in that.”

One Vortex or Two?

To understand a polar vortex and how it works, it helps to have a good definition. Unfortunately, there isn’t one. “It’s all a bit fuzzy,” says Darryn Waugh, an Earth and planetary scientist at Johns Hopkins University. “It’s become an everyday term when you talk about Earth, but people are really talking about different features.” 

When most people talk about Earth’s polar vortex, they’re instead referring to a weather phenomenon that occurs in the troposphere—the layer of the atmosphere that extends from the planet’s surface to altitudes of about five or six miles.

The pole-encircling jet stream, a narrow band of strong winds flowing from west to east in the troposphere, is present year-round, and is closely tied to weather patterns over Earth’s mid-latitudes, which encompass most of the United States. When the polar jet stream is strong and stable, it keeps the coldest air locked up over the pole. That means Earth’s mid-latitudes can experience especially warm weather. On the other hand, when the polar jet stream is wavy or weak, parts of it can plunge southward, triggering the dreaded arrival of Arctic air at lower latitudes—the popular concept of the polar vortex. 

To scientists who study the atmosphere, this isn’t the polar vortex. The polar vortex is a circular flow in the stratosphere, which extends from the top of the troposphere to altitudes of about 30 miles. This circular flow forms every fall, and vanishes  in spring. As the sun disappears from the polar region (northern or southern), the temperature above the pole plummets. Warmer air near the equator then flows toward the pole, where it’s deflected by Earth’s rotation, forming a strong west-to-east flow around the pole. A polar vortex is not visible, even in satellite images, but scientists can track it by measuring the wind speed, temperature, and even the chemistry of the rotating air.

Every couple of years, the polar vortex becomes unstable, which can be triggered by conditions in the troposphere. “There are waves in the atmosphere, and they break just like the waves on a beach,” says Amy Butler, a research scientist with the National Oceanic and Atmospheric Administration in Boulder, Colorado. These waves disturb the vortex, which can then wobble, stretch out, or even break into two smaller whirlpools. As winds in the vortex get disrupted, these effects can move downward and make the polar jet stream more wavy as well, increasing the chances of cold Arctic air escaping into lower latitudes. Alternatively, the jet stream can bulge northward in places, bringing warmer air to usually frigid locales. The effects of the polar vortex disruption can last for weeks or even months.

A polar vortex encircles the South Pole as well. The South Pole’s vortex, however, differs from its northern cousin. The southern hemisphere has less land and fewer mountain ranges near the pole, so fewer waves break into the stratosphere, resulting in a more stable southern vortex, with disruptions milder and much less frequent.

Increasing the Sample Size

Public perception to the contrary, outbreaks of the polar vortex in the northern hemisphere—the bitter cold triggered by the wandering jet stream—are becoming less common. “Winter temperatures are increasing faster than any other season, so the cold outbreaks are rapidly going away,” says Butler. Despite the warming trend, forecasters aren’t sure how global climate change will impact the northern polar vortex in the coming decades. (Most models say the southern vortex will become stronger.) “If you look at the climate models, half predict the [northern] vortex will get stronger by the end of the century, but half predict it will get weaker,” explains Butler. “It’s a huge source of uncertainty.” 

The models are limited in part by the small sample size. “Earth is far more accessible than any other planet, and we know its atmosphere quite well,” says Itziar Garate-Lopez, a planetary scientist at Spain’s Universidad del País Vasco who has specialized in studying the atmosphere on Venus. “However, to completely understand atmospheric physics, we need additional examples.” 

“Planetary exploration allows us to push our understanding [of Earth’s atmosphere and climate] to its limits, using worlds far larger than Earth—or far colder,” says Leigh Fletcher, a planetary scientist at the University of Leicester in England. “One thing is certain: studying the climates of other worlds helps to place the fragile environment of our own planet into a much broader context.” Venus and Mars, the planets that flank Earth’s orbit around the sun, are especially helpful. 

“Venus, Mars, and Earth are a bit of a Three Bears story—a little too much, not enough, and just right,” says Whitten. “With Mars and Venus, there are no people modifying the landscape in any way, so you can better understand the natural drivers of climate. They had very different starting conditions, so they look very different today.” 

Venus, which is closest to the sun, is like Mama Bear’s porridge: It’s too hot. That might not always have been the case, though. There’s evidence that Venus might have been a suitable home for life early in its history; some studies even say its surface might have been covered by a global ocean. 

Today, though, Venus is the most hellish planet in the solar system. Over eons, its atmosphere thickened, increasing temperatures. The intense heat baked carbon out of the rocks, pumping carbon dioxide into the atmosphere that intensified global warming on Venus. 

Although Earth’s future isn’t as dire, our planet is also experiencing a greenhouse effect. Human-produced carbon dioxide, methane, and other chemicals trap heat that then warms the atmosphere and oceans (see “Our Changing Planet”). Venus could tell us more about this process, says Garate-Lopez. “Understanding how Venus got into this situation, what the key players are, and whether it could somehow have been avoided, we could learn how to mitigate our climate change, or at least know our future in more detail,” she says. 

Venus has vortices at both poles but they’re quite different from Earth’s, largely because Venus rotates much more slowly than Earth does (one day lasts about 243 Earth days), and because Venus has almost no tilt on its axis, so there are no seasons on the planet. The lack of seasons enables the vortices to spin all year long. Instead of cold air, the vortices on Venus are filled with air that’s hotter than the surrounding atmosphere. These vortices wobble like a spinning top, with major changes in their appearance over periods as short as 24 hours. Since only two interplanetary missions have studied the Venusian poles, the vortices there are still poorly understood. 

Scientists have a better understanding of the vortices on Mars. As the next planet out from Earth, it’s the equivalent of Papa Bear’s porridge: too cold. Like the young Venus, early Mars was probably more temperate. It was much warmer and wetter, with a thicker atmosphere than it has today. Geological features on Mars reveal that water once flowed across the surface, carving rivers and settling in deep lakes. But the Red Planet’s magnetic field faded over time, leaving it vulnerable to solar winds that stripped away its atmosphere. Most of the planet’s water escaped into space, was frozen as permafrost, or trickled into niches well below the surface. That left Mars cold and dry, with an atmosphere that’s less than one percent as dense as Earth’s. 

Even so, Mars is more like Earth than any other planet or moon in the solar system. It rotates at almost the same rate as Earth (a Martian day is only about 40 minutes longer than an Earth day), and the planet is tilted at almost the same angle as Earth, so Mars has similar seasons. 

That, says Streeter, makes Mars the best natural laboratory for studying what Earth’s atmosphere might be like under different conditions. “Mars is similar enough to Earth that a lot of what we know translates fairly smoothly, but still strange and different enough to learn from and broaden our horizons regarding how atmospheres can behave and evolve,” he says. 

The Red Planet’s polar vortices, like Mars itself, are both familiar and peculiar. As on Earth, they’re seasonal, twirling to life every autumn and fizzling in spring. Unlike the stratospheric vortices on Earth, though, vortices on Mars extend all the way down to the surface. And instead of a single blob of cold air sitting atop the pole, each vortex forms a wide, elongated ring around the pole. That’s because the air above the poles is much colder than on Earth. It’s so cold that carbon dioxide in the atmosphere freezes—and as it does so, it releases heat that makes the air above it less stable. “So, it seems that Martian dry-ice snow may be responsible for its ring-shaped polar vortices,” says Streeter. 

The northern vortex on Mars is more dynamic than the southern one because of more dust activity. Much of the northern hemisphere is smoother and flatter than the southern hemisphere, except for some especially high ground near the equator. This difference in elevation creates strong wind currents that make the northern vortex much more elongated than the southern one. Giant dust storms in the northern hemisphere—some of which eventually cover the entire planet—warm the atmosphere, which can cause the vortex to weaken, wobble, and even vanish (see “Attack of the Martian Dust Storms,”).

Artistic Swirls on Giant Planets

If Mars, Earth, and Venus are characters from “Goldilocks and the Three Bears,” the planets of the outer solar system represent fairy tale giants. Jupiter, Saturn, Uranus, and Neptune are many times larger and more massive than Earth. They consist mainly of gases or hot ices (an exotic form of water that remains solid due to intense gravity) topped by relatively thin atmospheres. All four spin so rapidly that clouds in their atmospheres are stretched into parallel bands that encircle the globe. Yet, like their smaller, rocky siblings, their atmospheres spin into patterns that each tell a different story. 

Jupiter’s Great Red Spot, the biggest and longest-lived known vortex in our solar system, has been scrutinized with telescopes since at least the 19th century, and perhaps as early as the 17th.  A more recent discovery was made by the Juno spacecraft, which has been orbiting Jupiter since 2016. Images sent back to Earth revealed that Jupiter’s north pole has a central vortex that’s about 3,000 miles across, ringed by eight other vortices of about the same size. Jupiter’s south pole is similar, although its central vortex is slightly more stretched out and is surrounded by only five others. Seen together, these smaller vortices evoke Vincent van Gogh’s 1889 masterpiece, “The Starry Night,” with intertwining white whirls against a blue background. 

Planetary scientists still don’t fully understand Jupiter’s vortex clusters, including how they formed and how deep they penetrate into the atmosphere. “Jupiter really tested our theories on polar vortex dynamics, and to this day we’re still working on the underlying physics as to how they evolve,” says Dann Mitchell, a climate scientist at the University of Bristol. 

Vortices on Saturn—the second-largest planet and the next one out from Jupiter—also remain a mystery. The Cassini spacecraft photographed the vortices at both poles many times during its decade in orbit around the ringed planet—until the spacecraft ended its mission in 2017 by intentionally plunging into Saturn’s atmosphere. 

Telescopes have continued to supplement Cassini’s observations. One sight, in particular, continues to mesmerize scientists: Saturn’s north polar vortex is surrounded by a vast hexagon. Each side is several thousand miles long, and the entire structure spans 18,000 miles, which is wide enough to swallow two Earths side by side. 

The sides of the hexagon are jet streams that zip through the upper atmosphere at speeds of 200 miles per hour. We don’t see jet streams settle into symmetric shapes on Earth because the surface of our planet—with its varying topography amid alternating patches of ice, water, and land—disrupts atmospheric flow. But conditions are very different on Saturn, which has no solid surface. 

Scientists have managed to recreate the hexagon-shaped hurricane in an Earth-based lab, using a spinning cylinder of water. But researchers still have questions: What powers the hexagon? Why is it found in only one hemisphere? And how has it maintained its shape for decades? 

Much less is known about the storm systems on Uranus and Neptune, the two ice giants that orbit in the outer reaches of the solar system. No spacecraft have visited these frigid blue worlds since the Voyager flybys in the 1980s. 

When Voyager 2 visited Uranus in 1986, it didn’t get a view of the north pole, but it was able to measure changes in wind speeds at the ice giant’s south pole that indicated the existence of a polar vortex. Observations of the planet’s north pole have been difficult for Earth-based telescopes because Uranus, with an axial tilt of 97.8 degrees, rolls on its side like a giant barrel during its 84-year trip around the sun. As a result, Uranus experiences some of the most extreme seasons in the solar system. Each of the planet’s poles is engulfed in continuous sunlight or continuous darkness for more than four decades at a time. 

And, because of the planet’s tilt, summers are quite different than they are on other worlds. “On average, the poles get more sunlight than the equator, so it’s a world turned inside out and back to front,” says Fletcher. “That’s just one of the many reasons why we’d love to see a mission there.”

Voyager arrived when Uranus was near the southern solstice, with only the south polar region illuminated by the sun. But the planet reached an equinox in 2007, revealing areas around the north pole that had previously been shrouded.

With the northern hemisphere entering spring and edging closer toward northern summer, which begins in 2030, the Hubble Space Telescope captured images of Uranus in 2014 and 2022 that revealed a bright cap of icy smog forming at its north pole. Meanwhile, astronomers conducted observations over several years with the National Radio Astronomy Observatory’s Very Large Array in New Mexico and the Very Large Telescope in Chile. The observations revealed a dark collar around the pole, with warmer and drier air inside. And the arrangement remained anchored above the pole—adding to the distinctive signs of a strong polar vortex. 

“It’s a much more dynamic world than you might think,” NASA radio astronomer Alex Akins said in a statement announcing the discovery. “It isn’t just a plain blue ball of gas. There’s a lot happening under the hood.”

For about two decades, astronomers have observed a warm vortex at Neptune’s south pole. They got an even better look at it in 2022, when the James Webb Space Telescope captured a detailed view of the continuous band of high-latitude clouds surrounding the spiral storm. 

But Neptune, like Uranus, also has a lot going on under its hood. When Voyager 2 visited the ice giant in 1989, it captured an image of a dark spot in the southern hemisphere, roughly the size of Earth and spinning at speeds up to 1,300 mph. The Great Dark Spot disappeared a few years later, but the Hubble Space Telescope later discovered more of these short-lived “dark vortices” (as they are now called) in Neptune’s northern hemisphere. 

Since the dark vortices tend to disappear after a few months, sustained studies of them have proven difficult. Fortunately, the European Southern Observatory’s Very Large Telescope has an instrument—the Multi Unit Spectroscopic Explorer (MUSE)—that enabled astronomers to split Neptune’s reflected sunlight into constituent wavelengths, which are associated with different layers in the ice giant’s atmosphere. With the MUSE analysis, they could determine the altitude of the dark vortices, as well as the composition of the surrounding atmosphere. While astronomers had previously thought the dark vortices might be holes in Neptune’s cloud tops, the new observations indicate their distinctive coloring is likely the result of a chemical process triggered by heat from the vortex, causing air particles to darken just below the visible haze layer. 

Uncovering the secrets of Saturn’s hexagon, Jupiter’s sweet rolls, and Neptune’s smudges could help us learn more about planets in other star systems, many of which are also giants. The James Webb telescope is already providing details of the atmospheric composition of some of these exoplanets, and future telescopes could even provide crude images. Comparing the atmospheres of all the solar system’s planets to those found on distant worlds might help future scientists refine their ideas of how planetary systems form and evolve. 

In the end, say scientists, having plentiful examples to study can only help refine our understanding of Earth and its fragile climate. “It can help us as a society see what happens with crazy, different climates,” says Kirsten Siebach, a self-described Mars geologist at Rice University in Houston. “We can see what might happen if we don’t take care of Earth. So, sending missions into space can ultimately help us understand our place in the solar system, our place in the universe, where this planet came from and why it’s unique.” 

Damond Benningfield is a radio producer and science writer in Austin, Texas.

This article, originally titled “Into the Vortex,” is from the Winter 2025 issue of Air & Space Quarterly, the National Air and Space Museum's signature magazine that explores topics in aviation and space, from the earliest moments of flight to today. Explore the full issue.

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