Unexpected discovery of the largest storm lasting 190 years in the Solar System

According to astronomers, unexpected observations made by Hubble over 90 days from December last year to March this year show that the Great Red Spot is not as stable as it appears.

The Great Red Spot is a large anticyclone or wind in Jupiter's atmosphere that rotates around a central high-pressure area along the mid-latitude cloud belt to the south of the planet. This long-standing storm is the largest in the Solar System and could fit Earth inside it.

The changing Great Red Spot on Jupiter. (Image: NASA/ESA/Amy Simon).

Although storms are generally considered unstable, the Great Red Spot has existed for nearly two centuries. However, observed changes in the storm appear to be related to its motion and size.

Time-lapse images showed the storm vortex 'wobbling' like jelly and expanding and contracting over time. The researchers described the observations in an analysis published in the Planetary Science Journal.

"Although we knew its motion varied slightly in longitude, we didn't expect its size to fluctuate as well. As far as we know, this has never been seen before," said study leader Amy Simon, a planetary scientist at NASA.

Astronomers have been observing this crimson feature on Jupiter for at least 150 years, and sometimes the observations lead to surprises, including the latest revelation that the storm's oval can change size, sometimes looking thinner or fatter.

Recently, a team of astronomers peered into the center of the Great Red Spot using the James Webb Space Telescope to capture new details in infrared light. The Hubble observations were made in visible and ultraviolet light.

"To limited instruments, Jupiter's famous red streak clouds and storms appear static, stable and long-lasting for years, " said study co-author Leigh Fletcher, professor of planetary science at the University of Leicester in the UK. "But when we look closer, we see incredible variability, with turbulent weather patterns as complex as anything we have on Earth. Planetary scientists have been working for years to look for patterns in this variability, and anything that can help us understand the underlying physics of this complex system is welcome."

Insights gleaned from observations of the largest storms in our Solar System could help scientists understand what weather might be like on exoplanets orbiting other stars. That knowledge could expand scientists' understanding of meteorological processes beyond what we experience on Earth.