Jupiter’s Great Red Spot might be relatively young, possibly less than 200 years old, based on current estimates.

Jupiter’s iconic Great Red Spot might not be the same dark spot observed on the planet over three centuries ago.

From 1665 to 1713, astronomer Giovanni Domenico Cassini and others documented a dark oval feature on Jupiter, known as the Permanent Spot, located at the same latitude as the current Great Red Spot. Researchers have been investigating whether these historical observations represent the same feature as the Great Red Spot today.

An analysis of sketches and photographs of Jupiter spanning nearly 360 years, reported in the June 28 issue of Geophysical Research Letters, suggests that these spots are distinct. The study also includes computer simulations that propose the Great Red Spot may have originated from a disruption in wind patterns between opposing jet streams.

The Great Red Spot is the largest vortex in our solar system, located in Jupiter’s Southern Hemisphere, with wind speeds exceeding 600 kilometers per hour. However, its exact age and the factors that initiated its formation remain uncertain.

Historical observations provide some insight. Early astronomers meticulously recorded their observations, offering valuable clues. Agustín Sánchez‐Lavega, an astronomer and planetary scientist at the University of the Basque Country in Bilbao, Spain, highlights the importance of these historical records. His research indicates that by 1713, reports of Jupiter no longer mentioned the Permanent Spot, and by the 1830s, new drawings began depicting a prominent red-tinted oval similar to the Great Red Spot seen today.

But an area of rotation could have formed at this latitude between a jet stream moving westward and one moving east (SN: 11/3/23). A pressure disturbance could have caused the wind to do a U-turn at its ends, creating a flow that curved from north to south at one end and south to north at the other. This spinning region could have acted as precursor to the Great Red Spot, Sánchez‐Lavega says.

But the simulations used to study the giant windstorm’s formation don’t include thunderstorm activity, which is important to how the Great Red Spot maintains itself, Dowling says. A ring of thunderstorms forms around the planet at this latitude and eventually the storms get sucked into — and essentially feed — the Great Red Spot, he says. The Great Red Spot may help seed these storms — it’s so big that it obstructs the flow of gas around the planet at this latitude, creating a low-pressure region ripe for thunderstorm formation. “It’s in a global system.”

The Great Red Spot has been shrinking since it was spotted in the 1800s. It’s currently 1.1 times as wide as Earth —about the size of the long-lost Permanent Spot. And it may share that spot’s fate, Dowling says. A shriveling spot may not be able to fuel enough thunderstorm activity to sustain itself. “There are some people who are alive right now — some younger kids — that may see the end of this one.”