Astronomers have discovered that Jupiter’s Great Red Spot (GRS), the largest storm in the solar system, is undergoing a surprising oscillation in shape. Using data from the Hubble Space Telescope collected over 90 days, researchers observed fluctuations in the storm’s size, shape, and speed.
Astronomers using the Hubble Space Telescope have observed Jupiter’s Great Red Spot (GRS) undergoing an unexpected oscillation over a 90-day period between December 2023 and March 2024.
During this time, when Jupiter was 630.3 million to 824.8 million km (391 million to 512 million miles) from the Sun, the iconic storm was seen fluctuating in its elliptical shape, jiggling like gelatin. The cause of this oscillation, which spans approximately 90 days, remains unknown.
Day-to-day observations revealed changes in the storm’s ultraviolet-light brightness, with the core appearing brightest when the storm reaches its largest size during the oscillation cycle. This suggests reduced haze absorption in the upper atmosphere at those times.
Additionally, as the Great Red Spot accelerates and decelerates, it pushes against the jet streams located to its north and south, creating a bulging effect similar to an overfilled sandwich. This behavior contrasts with the storms on Neptune, where dark spots can drift freely without the confinement of strong jet streams like those on Jupiter.
This is the first time astronomers have had the proper imaging cadence to observe such oscillations. With Hubble’s high-resolution images, the GRS was observed squeezing in and out while simultaneously speeding up and slowing down, a behavior for which no hydrodynamic explanation currently exists.
The GRS, an anticyclone large enough to engulf Earth, has been observed for at least 150 years, but these new observations show it is not as stable as it appears.
Hubble’s observations were part of a specific program focused on the GRS, although the space telescope also monitors Jupiter and other outer planets annually through the Outer Planet Atmospheres Legacy (OPAL) program. Understanding the behavior of Jupiter’s largest storm system could provide broader insights into hurricane theories on Earth and even meteorological phenomena on planets beyond our solar system.
References:
1 A Detailed Study of Jupiter’s Great Red Spot over a 90-day Oscillation Cycle – Amy A. Simon et al. – The Planetary Science Journal – October 9, 2024 – DOI 10.3847/PSJ/ad71d1 – OPEN ACCESS
2 NASA’s Hubble Watches Jupiter’s Great Red Spot Behave Like a Stress Ball – NASA/Science – October 9, 2024