How Do Hurricanes on Earth Compare to Space Storms on Jupiter?

We may fear hurricanes, cyclones and other powerful storms on Earth — and rightly so — but the term "storm" takes on a whole new meaning on the giant, gaseous planet of Jupiter. There, a storm can be bigger than the Earth itself, and storm winds top out at around 375 mph (604 kph). For comparison, a Category 5 hurricane, the most powerful on Earth, starts at 155 mph (249 kph) on the Saffir-Simpson Hurricane Winds Scale.

Jupiter's tremendously violent, planet-sized storms can grow by hundreds of miles in a day, and they can throw ice and other matter up to 20 miles (32 kilometers) above the clouds. They're the product of about 12 bands of weather, or jet streams, that move east and west around the planet.

Violent Vortices
A storm on Jupiter is officially called a vortex. In the planet's northern hemisphere, a clockwise-rotating storm is called an anticyclone; a counterclockwise-rotating storm is a cyclone. The terms are reversed for storms in the southern hemisphere. Vortices may last for short periods of time, disappearing in the jet stream, or high-speed winds may push them into the path of other vortices, causing them to combine and form major storms.

A Never Ending Storm
Located in the southern hemisphere, the Great Red Spot is the most recognizable and most massive of Jupiter's storms. At up to 25,000 miles (40,000 kilometers) wide, this anticyclone is larger than two Earths put together. The storm sits at a higher altitude than most of the surrounding weather patterns, and its vast size often allows it to consume smaller storms. Since Jupiter is a gaseous planet, the Great Red Spot has never made landfall: That fact and its position near the equator get the credit for the spot's ancient age of at least 400 years old. Just imagine our entire planet perpetually covered in violent storms since Europe started colonizing the Americas in the 17th century. Maybe Mother Nature is taking it easy on us earthlings after all compared to this centuries-old space storm!

With an average temperature of 163 degrees below zero Celsius (216 degrees below Fahrenheit), Jupiter's red spot is far colder than any place on Earth. The temperature is also partly responsible for the spot's distinctive colors: The warmest areas appear to be more vivid shades of red, while colder areas are lighter colors. The spot has a distinctive swirl because its center rotates clockwise and while its outer region rotates counterclockwise. One counterclockwise rotation takes about 6 Earth days to complete.

Big Red's Baby Brother
Although it's officially called Oval BA, a smaller — though still quite large — storm on Jupiter is often known as Red Spot Jr. Compared to its big brother, this storm is practically a newborn. It began to form in 1998, when a group of vortices called the White Ovals, some of which were at least 90 years old, drifted toward each other and eventually combined into one storm stretching about 7,500 miles (120,000 kilometers) north to south.

By 2000, Oval BA had formed, but at the time the storm was mostly white. Over a few months in 2006, the storm darkened, turning a muddy red. Scientists suspect that the storm sucked up material from lower in the atmosphere, which then reacted with UV light from the sun. Like the Great Red Spot, it may owe its color to its position high in the atmosphere.

Because of its position closer to Jupiter's south pole, some scientists believe that Oval BA won't grow to be as big as the Great Red Spot. Even so, this smaller storm is still a major event, particularly when you compare it to our comparatively paltry weather patterns on Earth. After a decade, it's showing no signs that it'll soon disappear.