The Great Red Spot is only one part of Jupiter’s wild weather. You can also explore our full Jupiter facts for kids page to learn about Jupiter’s moons, rings, clouds, and missions.
The Great Red Spot is a giant storm in Jupiter’s southern hemisphere. It is roughly Earth-sized today — recent NASA measurements place it around 14,750 km (9,165 miles) wide, though its size keeps changing. The storm has been spinning continuously for at least 190 years, it is slowly shrinking, and nobody is completely sure why.
Look up at Jupiter tonight through a small telescope. If the Great Red Spot is facing Earth, you’ll see a tiny pinkish-orange oval just below Jupiter’s middle. Jupiter spins every 10 hours, so check a sky-map app to see if the Great Red Spot is on the visible side.
📋 Great Red Spot — Quick Facts
- LocationSouthern hemisphere of Jupiter
- Storm typeAnticyclonic (spins counter-clockwise around a high-pressure centre)
- WidthRoughly Earth-sized today; about 14,750 km (9,165 mi) in recent NASA Hubble measurements, but still changing
- DepthAt least 300 km deep; Juno data suggest it may reach about 500 km below the cloud tops
- AgeAt least 190 years (continuously observed since the 1830s)
- Edge wind speedAbout 430–680 km/h (270–420 mph) around the outer parts of the storm — far faster than the strongest hurricanes on Earth
- Rotation periodAbout 6 Earth days
- ColourRed — exact cause not fully understood
- New 2024 findingOscillates in width about every 90 days, like a stress ball (NASA Hubble)
What is the Great Red Spot?
The Great Red Spot is a huge, swirling storm in Jupiter’s atmosphere. It sits in the planet’s southern hemisphere, between two of Jupiter’s wide cloud bands.
The Great Red Spot is an anticyclonic storm — it spins in the opposite direction to most storms on Earth, with winds curling counter-clockwise around a high-pressure centre. One full spin takes about six Earth days.
Jupiter has many other storms, but the Great Red Spot stands out for three reasons: its size, its colour, and its age. Most storms on Earth last for days or weeks. The Great Red Spot has lasted at least 190 years.
There’s no land or sea on Jupiter to slow it down — Jupiter is a gas giant with no solid surface. With nothing to interrupt it, the Great Red Spot just keeps spinning.
ANTICYCLONE — a storm that spins around a high-pressure centre, in the opposite direction to a normal Earth hurricane. On Jupiter, anticyclones can last for centuries.
Imagine stirring a giant bowl of soup in one direction. Now imagine the soup is bigger than Earth, the bowl has no bottom, and the soup keeps swirling for hundreds of years — without anyone stirring it. That’s a simple way to picture the Great Red Spot.
How big is the Great Red Spot?
The Great Red Spot is enormous, but its exact size keeps changing. It is roughly Earth-sized today — recent NASA Hubble measurements (December 2023 to March 2024) put it at about 14,750 km (9,165 miles) wide. Independent images by amateur astronomers have measured it slightly smaller, around 12,500 km.
But it used to be much bigger. In the late 1800s, the Great Red Spot was wide enough that three Earths could line up across it side by side. Today, only about one Earth fits.
Scientists also discovered something amazing about how deep the storm goes. NASA’s Juno spacecraft used special gravity measurements to peer below the cloud tops. The storm reaches down at least 300 km — and Juno gravity data suggest it may extend as far as 500 km (about 310 miles) below the visible cloud tops. That makes the Great Red Spot far deeper than scientists had ever expected.
Then (1879): about 41,000 km wide — wide enough for 3 Earths side by side
1979 (Voyager 2): about 23,300 km wide — about 2 Earths
Now (Hubble, 2024): about 14,750 km wide — roughly 1 Earth
Why is the Great Red Spot red?
This is one of Jupiter’s biggest mysteries. Scientists know which chemicals are in Jupiter’s clouds — mostly ammonia, plus traces of sulfur and phosphorus — but they don’t fully understand which ones make the Great Red Spot specifically red.
The leading theory is that ultraviolet sunlight breaks chemicals in Jupiter’s upper atmosphere into red and orange compounds. The Great Red Spot reaches a little higher than the surrounding clouds, so its top layer might receive more sunlight — and create more of those red chemicals.
But the colour also changes over time. Some years the Great Red Spot looks darker red. Some years it looks pale, pinkish, or almost beige. Nobody knows yet why.
❓ Space Mystery
Why is the Great Red Spot so much redder, larger, and longer-lasting than most other storms on Jupiter? Other storms — like the smaller Oval BA — sometimes turn pink or brown, but none have stayed red as deeply, or as long, as the Great Red Spot. Solving this mystery may take more spacecraft visits.
How long has the Great Red Spot been there?
Astronomers have watched the Great Red Spot continuously since the 1830s, when telescopes first became powerful enough to track it from year to year. That makes it at least 190 years old as we write this.
But the story might go back even further. In the 1660s, the Italian astronomer Giovanni Cassini drew sketches of a red oval in roughly the same part of Jupiter. He called it the “Permanent Spot.”
Was Cassini’s spot the same storm we see today? Most scientists think no — they believe the 1660s storm faded away, and the Great Red Spot we know today formed sometime in the early 1800s. But we can’t be completely sure, because there’s a gap in the records between the late 1700s and the 1830s when nobody made detailed sketches.
Giovanni Cassini also discovered Saturn’s biggest gap in the rings (still called the Cassini Division today), and the NASA–ESA Cassini–Huygens spacecraft that explored Saturn from 2004 to 2017 was named in his honour. Cassini’s name appears on planets across the solar system.
Is the Great Red Spot shrinking?
Yes — the Great Red Spot is shrinking, and it has been for over 150 years.
The Hubble Space Telescope has been measuring the storm every year as part of a programme called OPAL (Outer Planet Atmospheres Legacy). The team is led by NASA scientist Amy Simon. Their measurements tell a clear story:
- 1879: about 41,000 km wide (3 Earths across)
- 1979: about 23,300 km wide (almost 2 Earths)
- 2024: about 14,750 km wide (roughly 1 Earth)
The Great Red Spot is also becoming more round. Long ago it was a stretched oval. Today it’s much closer to a circle.
And in October 2024, Amy Simon’s team announced a brand-new discovery: the Great Red Spot doesn’t just shrink slowly — it also oscillates in width about every 90 days, like a stress ball being gently squeezed in and out. Nobody knows yet why this happens.
Nobody knows whether the Great Red Spot will keep shrinking, stabilise, or eventually disappear. Smaller storms on Jupiter have been swallowed by it from time to time — possibly slowing the shrinkage. We’ll find out as Hubble and future missions keep watching.
Humans are causing the Great Red Spot to shrink.
Nothing humans do on Earth can reach Jupiter. The shrinkage is a natural process happening on Jupiter itself. Scientists are still working out what’s behind it.
Has any spacecraft visited the Great Red Spot?
Several spacecraft have photographed the Great Red Spot from far away. But only one has flown directly over it.
In July 2017, NASA’s Juno spacecraft made a close pass over the Great Red Spot — flying just 9,000 kilometres above it, closer than any spacecraft before. Juno’s cameras and instruments captured stunning detail, and revealed for the first time how deep the storm went.
Juno’s instruments showed that the Great Red Spot is far deeper than scientists expected. The microwave radiometer measured the storm reaching at least 350 km below the cloud tops. Then in 2021, a separate set of gravity measurements pushed that estimate even further: the Great Red Spot may extend about 500 km (310 miles) below the visible cloud tops. The storm is much bigger in 3D than it looks in photographs.
In 2017, Juno fired its instruments straight down through the Great Red Spot for less than a minute as it raced past. That brief flyover gave scientists more data on this storm than the previous 50 years of telescope observations combined.
Read more about NASA’s Juno mission →
What’s near the Great Red Spot? Meet Oval BA
The Great Red Spot isn’t Jupiter’s only red storm. Just below it sits a smaller storm called Oval BA, sometimes called “Red Spot Jr.”
Oval BA formed in 2000, when three smaller white storms collided and merged. It was originally white. Then in 2006, it turned a pale red — surprising everyone.
Oval BA is much smaller than the Great Red Spot — only about as wide as Earth. But scientists watch it closely, because it gives them a chance to study how Jupiter’s storms form, change colour, and (sometimes) die.
Read more about Jupiter’s storms →
Frequently asked questions about the Great Red Spot
Is the Great Red Spot bigger than Earth?
It used to be. The Great Red Spot is currently about the same width as Earth — recent NASA measurements put it around 14,750 km wide, only slightly larger than Earth’s 12,756 km diameter. In the late 1800s it was three times wider than Earth.
How long has the Great Red Spot lasted?
Astronomers have watched it continuously since the 1830s, making it at least 190 years old. A different storm in the same area was sketched in the 1660s, but most scientists think that earlier storm faded away before the current one started.
Why is the Great Red Spot red?
Nobody is completely sure. The most popular idea is that ultraviolet sunlight breaks chemicals (like sulfur and phosphorus) in Jupiter’s upper atmosphere into red and orange compounds. The exact recipe is still being worked out.
Is the Great Red Spot shrinking?
Yes. The Hubble Space Telescope has been measuring it for decades and it’s now about half the width it was 100 years ago. It’s also becoming more round, and in 2024 NASA discovered that it oscillates in width about every 90 days.
Could the Great Red Spot disappear one day?
Maybe. It’s been shrinking for over 150 years, but smaller storms feed into it from time to time. Nobody knows whether it will keep shrinking, stabilise, or eventually fade away completely.
How fast are the winds in the Great Red Spot?
Winds around the outer parts of the storm reach about 430–680 km/h (270–420 mph), depending on where and how they are measured. That’s much faster than the strongest hurricanes on Earth.
Can you see the Great Red Spot with a telescope?
Yes! With a small backyard telescope you can spot the Great Red Spot as a tiny pinkish-orange oval — when it’s facing Earth. Use a sky-map app to check timing, because Jupiter spins every 10 hours.
Has any spacecraft visited the Great Red Spot?
Several have photographed it. NASA’s Juno made the closest pass in July 2017, flying just 9,000 km above the storm, and used gravity measurements to constrain its depth at about 500 km below the cloud tops.
Is there anything like the Great Red Spot on other planets?
Saturn, Uranus and Neptune all have long-lasting storms, but none as long-lived as the Great Red Spot. Neptune had a “Great Dark Spot” that disappeared within six years of its discovery.
Quick recap
- The Great Red Spot is a giant anticyclonic storm in Jupiter’s southern hemisphere
- It’s roughly Earth-sized today — about 14,750 km wide and shrinking
- It’s been spinning continuously for at least 190 years
- The storm is shrinking — half its size from 100 years ago
- Nobody is completely sure why it’s red
- NASA’s Juno spacecraft flew over it in 2017 and found it reaches up to 500 km below the cloud tops
- Smaller storms like Oval BA form on Jupiter too — but none lasts like the Great Red Spot
Want to learn more about Jupiter’s amazing weather? Head over to Jupiter’s storms, the Jupiter atmosphere page, or back to the main Jupiter pillar.