Jupiter is a monster. Honestly, it's hard to wrap your head around the scale of the gas giant, but nothing hammers that point home quite like the Great Red Spot. If you've ever looked through a backyard telescope, you’ve probably seen that tiny, brick-colored blemish marring the planet's southern hemisphere. But don't let the size in the eyepiece fool you. When people ask how big is the storm on jupiter, they’re usually expecting an answer involving "miles" or "kilometers."
The real answer? You measure it in Earths.
This isn't just a "big" storm. It’s a high-pressure anticyclone that has been screaming across the Jovian atmosphere for at least 150 years—and likely much longer. It's a swirling vortex of crimson clouds that would swallow our entire home planet without breaking a sweat. If you dropped Earth into the center of the Great Red Spot, we wouldn’t even touch the edges.
The Numbers Behind the Beast
Let’s get into the actual dimensions because they are frankly terrifying. As of the latest data from NASA’s Juno mission, the Great Red Spot is roughly 10,159 miles (16,350 kilometers) wide. For context, Earth’s diameter is about 7,917 miles.
Think about that.
You could take our entire world—every ocean, every continent, every mountain range—and tuck it inside that storm with thousands of miles to spare. It’s like a marble sitting inside a dinner plate. But here’s the kicker: it used to be way bigger. Back in the 19th century, observers estimated the storm was about 25,000 miles across. That’s three Earths side-by-side.
Why is it shrinking? Scientists aren't totally sure. Amy Simon, a planetary scientist at NASA’s Goddard Space Flight Center, has noted that while the storm is getting narrower, it's also actually getting taller. It’s stretching upward like a piece of clay being squeezed.
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The depth is another story. We used to think it was just a surface feature, a thin layer of clouds. Juno changed everything. By measuring the gravity signals as the spacecraft flew over the spot, researchers discovered the storm’s roots go deep. We’re talking 200 to 300 miles (300 to 500 kilometers) into the planet’s interior.
That is significantly deeper than Earth’s oceans. It’s a massive, churning column of gas that taps into the internal heat of the planet.
Why the Great Red Spot Doesn't Just "Die"
On Earth, a hurricane hits land and peters out. It loses its energy source (warm water) and friction with the ground tears it apart. Jupiter has no ground. It’s just gas all the way down until things get weird and metallic at the core.
Basically, there’s nothing to stop it.
The Great Red Spot is trapped between two massive jet streams. To the north, a jet stream moves east; to the south, one moves west. These act like gears in a machine, constantly spinning the storm and feeding it momentum. It’s a self-sustaining engine of chaos.
The Speed of the Winds
If you were standing—well, floating—on the edge of the Great Red Spot, you’d be facing winds that make a Category 5 hurricane look like a light breeze. Wind speeds at the edge of the storm have been clocked at over 400 miles per hour (640 kilometers per hour).
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Interestingly, the center is relatively calm. It’s the periphery where the violence happens. Recently, data suggested the "outer ring" of the storm is actually speeding up. We don't know why. Jupiter is a dynamic, evolving mess of fluid dynamics that defies most of our terrestrial models.
The Color Mystery: Why Is It Red?
You’d think we’d know why it's red by now. We don't.
The most popular theory involves "photochemicals." Basically, chemicals like ammonia and acetylene are being dredged up from deep within the planet and blasted by solar ultraviolet radiation. This causes a chemical reaction that turns them a reddish-brown color—sort of like a cosmic sunburn.
If the storm were just made of the clouds we see elsewhere on Jupiter, it would be white or pale yellow. The red is a signal of its power, reaching down deep to pull up "stuff" that usually stays hidden.
Is the Storm Disappearing?
There was a lot of buzz a few years ago about the Great Red Spot "unraveling." People saw big flakes of red clouds peeling off the main vortex. Some headlines claimed the storm would be gone in twenty years.
Calm down. It's probably not going anywhere.
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Philip Marcus, a professor at the University of California, Berkeley, argued that those "flakes" were just natural interactions with smaller storms nearby. The underlying vortex is still incredibly strong. While it is definitely smaller than it was in the 1800s, it has reached a sort of "stunted" stability. It’s transitioning from an oval to a circle.
How to See the Storm Yourself
You don't need a multi-billion dollar probe to answer how big is the storm on jupiter for yourself. You just need a decent telescope.
- A 4-inch to 6-inch aperture telescope is usually enough to spot the Red Spot on a clear night.
- Timing is everything. Jupiter rotates fast—a "day" there is only about 10 hours. If the spot is on the far side of the planet, you won't see it. Use an app like SkySafari or check a Great Red Spot transit calculator online.
- Look for the "hollow." Sometimes the spot isn't bright red; it can look like a pale salmon or even a "dent" in the dark southern equatorial belt.
What This Means for Us
Understanding Jupiter’s weather isn't just about trivia. It’s about fluid dynamics on a grand scale. The same physics that govern the Great Red Spot govern the currents in our oceans and the supercells that cause tornadoes in the Midwest.
Jupiter is our laboratory for the "extreme." If we can figure out why a storm can last 300 years and stay 10,000 miles wide, we might finally understand the deeper mechanics of our own atmosphere.
Moving Forward
To get the most out of your interest in Jovian weather, start by tracking the planet's position in the night sky. Jupiter is currently one of the brightest objects in the heavens, often outshining every star. If you're looking to dive deeper, check out the JunoCam website. NASA actually lets the public vote on which features the Juno spacecraft should photograph during its "perijove" flybys. You can download the raw data and process the images of the Great Red Spot yourself, seeing details that no human had ever laid eyes on until the last few years.
Keep an eye on the official mission updates from the Southwest Research Institute (SwRI). They are the ones leading the charge on Juno’s data analysis. As the storm continues to shrink and change shape, the next decade of observation will be critical in determining if we are witnessing the final century of a solar system icon or just a temporary diet for a giant that will eventually grow again.