Photo: NASA/JPL-Caltech/MSSS/SwRI/Kevin M. Gill · Public domain
Wider than Earth
Jupiter's Great Red Spot is a storm wider than Earth that has raged for at least 150 years.
5 min readLast updated
The short answer
Yes. The Great Red Spot is a giant storm on Jupiter, currently about 16,000 kilometers across, wider than Earth's roughly 12,700 kilometers. It has been observed continuously since at least the 1830s.
Why it's true
Jupiter is a gas giant with no solid surface. Its atmosphere is banded by powerful jet streams, and the Great Red Spot sits between two of them in the southern hemisphere. It is an anticyclone, a high pressure storm, spinning counterclockwise with winds that can exceed 400 kilometers per hour at its edges.
Measurements by the Hubble Space Telescope and NASA's Juno spacecraft show the spot has been shrinking. In the late 1800s it was estimated at around 40,000 kilometers wide. By 2017 it measured about 16,000 kilometers. Even so, Earth could still fit inside it, and it remains the largest known storm in the solar system.
No storm on Earth lasts more than weeks. This one has lasted well over a century.
By the numbers
~16,000 km
Width measured in 2017
~12,700 km
Earth's diameter for comparison
1831
Continuous tracking begins
400+ km/h
Wind speeds at the edges
How we know
Astronomers have tracked the Great Red Spot continuously since 1831. The Italian astronomer Giovanni Cassini reported a permanent spot on Jupiter in 1665, but historians and scientists debate whether that was the same storm, because records have a long gap. A 2024 study concluded Cassini's spot was probably a different feature that disappeared.
Spacecraft have revealed much more. Voyager 1 and 2 photographed swirling detail in 1979. Juno, in orbit since 2016, used microwave instruments to look beneath the cloud tops and found the storm extends a few hundred kilometers down into the atmosphere, far deeper than Earth's oceans but shallow compared with Jupiter's size.
Storms that swallow storms
Smaller storms on Jupiter sometimes drift into the Great Red Spot and merge with it, possibly feeding it energy.
In 2000, three white storms merged to form Oval BA, nicknamed Red Spot Junior, which later turned reddish itself.
Worth remembering
- The Great Red Spot is a storm wider than Earth.
- It has been observed continuously since 1831.
- It has been shrinking over the past century.
In context
Jupiter's weather is extreme because the planet is so large and spins so fast, completing a day in under ten hours. That rapid spin stretches its clouds into bands and powers jet streams that can trap storms for long periods.
Other planets have long lived storms too. Neptune's Great Dark Spot, seen by Voyager 2 in 1989, vanished within a few years, and Saturn has huge seasonal storms. None has matched the Great Red Spot's staying power.
Jupiter itself is enormous, about 11 times wider than Earth and more than twice as massive as all the other planets combined. Against that backdrop, a storm larger than our planet looks like just one swirl among many. Jupiter's bands are full of white ovals, brown barges and churning eddies, but the Great Red Spot has outlasted all of them, which is why it has become the planet's most famous feature.
A closer look
Shrinking and changing shape
Over the past century the spot has become rounder as well as smaller. Its colour has also deepened at times.
Researchers are still working out why. Changes in the jet streams around it and interactions with smaller storms may be part of the answer.
Juno's view from above
Juno passes low over Jupiter's clouds on a looping orbit, giving close views of storms and the poles.
Its gravity measurements helped estimate how deep the Great Red Spot reaches, a key clue to how it stays alive.
Seeing it yourself
Through a backyard telescope, the Great Red Spot can appear as a pale salmon oval in Jupiter's southern cloud belts.
Because Jupiter spins quickly, the spot rotates into and out of view within a few hours.
Related facts
Jupiter's moons are giants too Jupiter's moon Ganymede is wider than Mercury.
Another of Jupiter's wild worlds Io is the most volcanic world.
Jupiter's moons may hold water Europa likely hides an ocean.
For Earth's own extreme weather lightning is hotter than the Sun's surface.
Key terms
- Anticyclone
- A high pressure weather system whose winds circle around a central area.
- Gas giant
- A large planet made mostly of hydrogen and helium, with no solid surface.
- Jet stream
- A fast, narrow current of wind in a planet's atmosphere.
Myth vs reality
Myth
The Great Red Spot is a giant volcano or a hole in Jupiter.
Reality
It is a long lived high pressure storm in Jupiter's atmosphere.
People also ask
How big is the Great Red Spot?
About 16,000 kilometers wide as of 2017, a little wider than Earth. It was much larger in the 1800s and has been shrinking.
How old is the Great Red Spot?
It has been observed continuously since 1831. Whether it is the same spot Cassini saw in 1665 is debated, and recent research suggests it is not.
Why is the Great Red Spot red?
Scientists are not completely sure. A leading idea is that sunlight breaks apart chemicals such as ammonia and acetylene in the upper atmosphere, producing reddish compounds.
Why does the storm last so long?
Jupiter has no land to slow storms down, and surrounding jet streams help keep the spot spinning. It also absorbs smaller storms.
Will the Great Red Spot disappear?
It may continue shrinking, but no one can say if or when it will vanish. Scientists keep monitoring it with telescopes and spacecraft.
