If you look at a picture of the biggest planet in our solar system, you can’t miss it. That angry, swirling eye staring back at us from the southern hemisphere is the Great Red Spot, which is the official answer to what is the storm on Jupiter called. It’s not just a storm, though. Honestly, calling it a "storm" feels like calling the Pacific Ocean a "puddle." It is a high-pressure anticyclone that has been screaming across the Jovian clouds for centuries, and it’s large enough to swallow Earth whole without even breaking a sweat.
But here’s the thing. It’s changing.
Jupiter is a gas giant, a massive ball of hydrogen and helium with no solid surface to grind a storm down. On Earth, a hurricane hits Florida, hits the land, and dies out because it loses its heat source and faces friction. Jupiter doesn't have that problem. The Great Red Spot just keeps spinning. Astronomers like Giovanni Cassini or Robert Hooke might have seen it as far back as the 1600s, though there’s a bit of a historical debate about whether the spot they saw is the exact same one we see today.
Why is the Great Red Spot Red?
We actually don't know for sure. That sounds wild, right? We’ve sent the Juno spacecraft, the Voyagers, and Pioneer, yet the exact chemical recipe for that brick-red hue remains a bit of a mystery. The leading theory involves "photochemical" reactions. Basically, solar radiation hits chemicals like ammonia and acetylene in the upper atmosphere. This creates complex organic molecules called chromophores.
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Think of it like a sunburn. When these chemicals get "cooked" by the sun’s UV rays, they turn that deep, iconic red. Interestingly, the storm is deeper than we thought. Data from NASA’s Juno mission suggests the storm roots itself about 200 to 300 miles deep into the planet. For context, the deepest part of Earth's ocean is only about 7 miles. This is a massive, vertical beast of a weather system.
The Incredible Shrinking Act
For a long time, the Great Red Spot was huge. Like, "fit three Earths inside it" huge. In the late 1800s, observers estimated it was about 25,000 miles wide. When Voyager 1 and 2 flew by in 1979, it had already shrunk significantly. Today? It’s down to about 10,000 miles. You could still fit Earth inside it, but it’s getting tight.
It’s also changing shape. It used to look like a long, thin oval—kinda like a cigar. Now, it’s becoming more circular. Some scientists, like Philip Marcus from UC Berkeley, have argued that the storm isn't necessarily dying, but rather shedding "flakes" of energy. Others are worried it might vanish within our lifetime. Imagine Jupiter without its most famous feature. It would be like seeing Saturn without its rings.
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What is the Storm on Jupiter Called and How Does it Move?
While the Great Red Spot is the king, it’s not the only storm. Jupiter is a chaotic mess of weather. The planet rotates incredibly fast—a day only lasts about 10 hours. This rapid spinning creates powerful jet streams that wrap around the planet like belts.
The Great Red Spot is trapped between two of these jet streams. One moves east, the other moves west. Because it’s an anticyclone (spinning counter-clockwise in the southern hemisphere), it’s constantly being fed by the sheer of these winds. It’s a self-sustaining monster. The winds at the edge of the spot can reach 270 to 425 miles per hour. That’s more than double the strength of a Category 5 hurricane.
Other Storms You Should Know About
It’s easy to focus on the big one, but Jupiter has a "Little Red Spot" too. Formally known as Oval BA, this storm formed in 2000 when three smaller white storms collided and merged. It stayed white for a few years, then suddenly turned red in 2006.
Then you have the "String of Pearls." These are a series of massive, white, counter-rotating storms in the southern hemisphere. From a telescope, they look like a necklace draped across the planet. Each "pearl" is roughly the size of a continent on Earth.
The Physics of the Abyss
Why does it stay in one place? Mostly because Jupiter lacks a solid crust. On Earth, weather is dictated by mountains, oceans, and plains. On Jupiter, it’s all fluid dynamics. The Great Red Spot stays at a relatively constant latitude of 22 degrees south. It drifts in longitude, circling the planet at its own pace, but it stays in its "lane."
The heat source is also key. Jupiter radiates more heat than it receives from the Sun. This internal heat, left over from the planet’s formation and generated by gravitational contraction, bubbles up from the interior. This "convection" is the engine for the Great Red Spot. It’s like a giant pot of thick soup boiling on a stove that never gets turned off.
Is the End Near for the Great Red Spot?
Amy Simon, a planetary scientist at NASA’s Goddard Space Flight Center, has noted that the storm's color is also deepening as it shrinks. As the storm gets smaller, it’s actually getting taller. Imagine a piece of clay being squeezed; it gets narrower but sticks out further. This might be why the red is getting more intense—the storm is reaching higher into the atmosphere where the sun can "bake" those chemicals more effectively.
Will it disappear? Maybe. But these systems are remarkably resilient. Even if the Great Red Spot fades, the atmospheric conditions that created it still exist. Another one could eventually take its place.
Seeing It For Yourself
You don't need a multi-billion dollar satellite to see what is the storm on Jupiter called. Even a decent backyard telescope (with at least 4 to 6 inches of aperture) can reveal the spot on a clear night when Jupiter is in opposition.
- Check the Transit Times: Jupiter spins fast. If the spot is on the "back" side of the planet, you won't see it. Use an app like SkySafari or check websites like Sky & Telescope to find out when the Great Red Spot is crossing the center of the planet’s disk.
- Use a Filter: A light blue or green filter can help pop the contrast of the red/orange tones against the white clouds.
- Wait for "Steady Air": Atmospheric turbulence on Earth (twinkling) ruins the view. Look for nights where the stars don't twinkle much—that means the air is steady and you can crank up the magnification.
Actionable Next Steps
To truly appreciate the scale of Jupiter's weather, you should track the planet's movement over the next few months. Jupiter is currently one of the brightest objects in the night sky.
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- Download a star map app (like Stellarium) to locate Jupiter tonight.
- Look for the "Galilean Moons" even with basic binoculars. You'll see four tiny dots (Io, Europa, Ganymede, and Callisto) orbiting the giant.
- Follow the Juno Mission updates on NASA’s official site. They frequently release "raw" images that the public can process, showing the Great Red Spot in detail that surpasses anything we've seen in human history.
The Great Red Spot is a reminder that Earth is a very small, very calm place in a very violent universe. Whether it lasts another twenty years or another two hundred, it remains the most spectacular weather event in our reach.
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