Jupiter’s Signature Red Spot May Have Evolved More Than Once

Researchers may have resolved a mystery of the Great Red Spot, a massive storm swirling above Jupiter’s surface.

The astronomer Giovanni Domenico Cassini first observed a vortex over the same region of Jupiter in 1665 and named it the ‘Permanent Spot’—but scientists have been unsure whether it was the same storm as the one seen today. In a new study published this month in Geophysical Research Letters, researchers analyzed historical observations of the spot and have determined that the two storms are probably different.

“From the measurements of sizes and movements, we deduced that it is highly unlikely that the current Great Red Spot was the ‘Permanent Spot’ observed by Cassini,” Agustín Sánchez-Lavega, a planetary scientist at the University of the Basque Country in Spain who led the research, says in a statement. “The ‘Permanent Spot’ probably disappeared sometime between the mid-18th and 19th centuries, in which case we can now say that the longevity of the Red Spot exceeds 190 years.”

Scott Bolton, a physicist at the Southwest Research Institute who wasn’t involved in the study, tells New Scientist’s Leah Crane that it’s difficult to make conclusions from the hand-drawn pictures the researchers partly relied on for early data about the spot.

“What I think we may be seeing is not so much that the storm went away and then a new one came in almost the same place—it would be a very big coincidence to have it occur at the same exact latitude, or even a similar latitude,” Bolton says to New Scientist. “It could be that what we’re really watching is the evolution of the storm.”

After Cassini first noticed Jupiter’s spot, astronomers continued to observe it until 1713. Then, the so-called Permanent Spot seemingly disappeared. “No astronomer of the time reported any spot at that latitude for 118 years,” Sánchez-Lavega tells Mashable’s Mark Kaufman. Another spot wasn’t reported until 1831, but scientists have been watching it ever since.

The current spot has diminished from a length of 24,200 miles in 1879 to around 8,700 miles currently. But that’s still longer than the diameter of the Earth (just over 7,900 miles). The storm’s winds can reach up to 400 miles per hour, and scientists still aren’t sure how chemicals in the atmosphere might give it its red hue, according to NASA.

For the new study, researchers turned to drawings of the original spot, as well as drawings of the new spot dating from 1831 to 1879, photographs from 1879 to 1980 and digital images from 1980 to 2023.

“I love articles like this that delve into pre-photographic observations,” Michael Wong, a research scientist at the University of California, Berkeley, who did not contribute to the findings, says to CNN’s Ashley Strickland.

The centuries of data allowed the scientists to analyze how the storms’ size and movement changed over time. Early drawings indicated that the Permanent Spot was much smaller than the current spot—meaning it would have needed to grow at a rate atypical for a Jovian storm to reach the size of the Great Red Spot in the 19th century, New Scientist writes. Plus, the storm now seems to be shrinking.

The researchers also investigated possible explanations for how the Great Red Spot formed by running simulations of storm behavior in Jupiter’s atmosphere. The most likely scenario was that instability in the planet’s intense atmospheric winds produced the storm, per the statement.

Future research will look into how the spot has remained relatively stable for a long period of time and how it might evolve going forward.

“We do not know what the future of the [Great Red Spot] is,” Sánchez-Lavega tells Mashable. It could break apart if it continues to shrink, or “it may reach a stable size and last for a long time.”

Will Sullivan | | READ MORE

Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.