The biggest and strongest storms to hit Earth are around 1,000 miles across, with winds upwards of 200 mph. Hurricane Patricia, for example, is among the strongest ever recorded on Earth with sustained winds upwards of 215 mph, although it was reduced to a Category 4 before smashing into the coast of Mexico. But even these mega-storms are nothing compared to Jupiter’s Great Red Spot (GRS).
Around the width of Earth, with winds of 400 mph, this giant system has been churning over Jupiter for hundreds of years. And even more fascinating, researchers have shown using images of GRS that it’s changing all the time and that it oscillates like a stress ball. In a study published last month in the Planetary Science Journal, a time-lapsed video showed how the storm shifts over a 90-day period.
The Great Red Spot
GRS is a high-pressure system located on Jupiter that produces an anticyclonic storm, meaning that the high pressure is in the middle, with winds circulating around its center. While it resembles a hurricane, it operates in the opposite manner, says Michael H. Wong, study author and a planetary scientist at the University of California Berkeley.
“A hurricane is a low-pressure system or cyclone, and the Great Red Spot is a high-pressure system or anticyclone,” says Wong. GRS is rotating in the opposite direction of a hurricane.
What’s more, it’s a mega-storm that doesn’t drift north and south because it’s stuck in place, says Wong, “sandwiched in between a pair of jet streams.”
The closest comparison on Earth to an anticyclone is an ocean eddy, a swirl of water cut off from the normal ocean current with currents that move fast around a center while the center moves slowly through the ocean. These are stable storms that last for many months or years, unlike a hurricane, which runs out of steam within a couple of weeks. GRS is also referred to as a “pancake vortex” because it’s much thinner than it is wide, at around 10,000 km (about 6200 miles) across by 200 km (about 124 miles) deep.
Discovered in the 1800s, astronomers didn’t have photography so they would look through a telescope and then sketch what they’d seen. Researchers had previously thought that GRS dated all the way back to the 1600s, but now they’re confident that the storm that G. D. Cassini discovered in 1665, called the Permanent Spot, was likely a different, much smaller storm that has since disappeared. GRS came later and was first discovered around 1831.
Read More: 5 Planets with Extreme (and Weird) Weather Patterns in Our Solar System
Why Is the Storm Oscillating?
We don’t know for sure why the storm is moving this way but we know that it is, thanks in part to a huge community of amateur astronomers as well as Hubble Space Telescope taking images of GRS on the regular. We can also see that its shape changes, something that researchers have known for a while.
We also know that the storm is moving slowly westward around Jupiter, and it takes around three years to move around the planet, says lead study author Amy A. Simon, a planetary scientist at NASA. As part of the study, researchers used observations from Hubble to gather data from eight dates spanning from December 2023 to March 2024. They found that longitudinal positions oscillated over a 90-day period, but there was no corresponding latitude drift.
Read More: Jupiter's Great Red Spot Reveals Its Stormy Secrets
The Great Red Spot Changes Over Time
“We know that the storm has been changing, and we also know that the internal wind speeds have been changing,” says Simon. The biggest difference is that it’s much smaller now than it was in the late 1800s. Years later, when NASA first measured it, the storm could fit about two Earths within its borders, and now that number is more like one. GRS also changes color occasionally, getting darker and lighter all the time. Its shape has also changed. Once oval-shaped, over the years, it’s been shrinking and has begun to be more circular.
What we don’t know, and what researchers want to know next, is what’s happening beneath the clouds of Jupiter. What’s going on in the middle of a storm that’s been around since before light bulbs, cars, and airplanes? A lot has changed, but GRS is still going strong.
Read More: Jupiter’s 8,700-Mile-Wide Great Red Spot Keeps Shrinking
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Planetary Science Journal. A Detailed Study of Jupiter's Great Red Spot over a 90-day Oscillation Cycle
Study author and a planetary scientist at the University of California Berkeley. Michael H. Wong
Advancing Earth and Space Sciences. The Origin of Jupiter's Great Red Spot
Planetary scientist at NASA. Amy A. Simon
