Astronomy
Properties of Jupiter's Great Red Spot Storm
Quick fact
The Great Red Spot is an anticyclonic storm that has been continuously observed since the 1600s, and it could swallow our entire planet with room to spare.
Why this is interesting
Imagine a storm larger than Earth that has been raging for at least 350 years — that's Jupiter's Great Red Spot. But what makes it so stubborn and why is it red?
Read the full explanation
Understanding Properties of Jupiter's Great Red Spot Storm
The Great Red Spot is a massive, oval-shaped storm in Jupiter's southern hemisphere. It is an anticyclone, meaning it rotates counterclockwise (in the southern hemisphere) with high-pressure at its center. The storm's width is about 1.3 times Earth's diameter, though it has been shrinking. Winds at its outer edge can exceed 400 kilometers per hour (250 mph), faster than any hurricane on Earth. Unlike terrestrial storms that dissipate over land or cooler water, the Great Red Spot persists because Jupiter has no solid surface to break up the storm and because the planet's internal heat drives strong atmospheric circulation. The storm's color—ranging from brick-red to pale orange—is still not fully understood, but it likely involves complex chemical reactions of compounds such as ammonia, phosphorus, or sulfur compounds dredged up from deeper layers.
A deeper explanation
The Great Red Spot's longevity and behavior are governed by the physics of rotating fluids and lack of frictional dissipation. Jupiter's rapid rotation (once every 10 hours) generates strong Coriolis forces that anchor the anticyclone, while the planet's internal heat creates turbulent bands (zones and belts) that interact with it. The storm is actually a stable vortex that has absorbed smaller storms and merged with them, maintaining its energy. The red color is thought to result from photochemical reactions: sunlight breaks down ammonia and acetylene in the upper atmosphere, producing compounds like hydrazine or other organic molecules that absorb blue light, giving the spot its reddish hue. Changes in color and size (it is slowly shrinking) provide clues about Jupiter's atmospheric dynamics and the ocean of liquid metallic hydrogen below. Understanding this storm helps scientists model weather on gas giant exoplanets and informs theories of long-term atmospheric stability.