What is the Great Red Spot?
The Great Red Spot is a giant storm on Jupiter, wider than Earth. It has been raging for at least 190 years and possibly since astronomers first saw a spot there in the 1600s.
The Great Red Spot is a high-pressure storm, called an anticyclone, in Jupiter's southern hemisphere. Winds around its edges blow at about 430 to 680 km/h. Its reddish color may come from chemicals produced when sunlight breaks down molecules high in the atmosphere.
Astronomers have watched the storm continuously since 1830. It has been shrinking: in the late 1800s it was about 40,000 kilometers wide, while today it is roughly 16,000 kilometers across, still larger than Earth.
Why it lasts so long
Storms on Earth weaken when they reach land. Jupiter has no solid surface, so the storm has nothing to slow it down. It is also fed by smaller storms and powered by heat rising from inside the planet.
Did You Know?
NASA's Juno spacecraft found that the Great Red Spot extends roughly 300 to 500 kilometers down into Jupiter's atmosphere.