The Great Red Spot, an anticyclone with a diameter of 10,000 miles, is the largest storm in the solar system and has been adorning Jupiter’s surface for centuries.
According to a recent study, Saturn also possesses long-lasting megastorms with impacts deep in the atmosphere that continue for millennia, despite being considerably duller and less colorful than Jupiter.
Researchers from the Universities of California, Berkeley, and Michigan, Ann Arbor, examined the planet’s radio emissions, which originate below the surface, and discovered long-term abnormalities in the ammonia gas distribution.
In the journal Science Advances, the study was released today.
Megastorms, which are akin to hurricanes on Earth but far larger, happen on Saturn about every 20 to 30 years. The reason for megastorms in Saturn’s atmosphere, which is primarily made of hydrogen and helium with traces of methane, water, and ammonia, remains unknown, in contrast to the factors that lead to hurricanes on Earth.
“Understanding the mechanisms of the largest storms in the solar system puts the theory of hurricanes into a broader cosmic context, challenging our current knowledge and pushing the boundaries of terrestrial meteorology,” said lead author Cheng Li, a former 51 Peg b Fellow at UC Berkeley who is currently an assistant professor at the University of Michigan.
Imke de Pater, emerita professor of astronomy and earth and planetary sciences at UC Berkeley, has been researching gas giants for more than 40 years in an effort to better understand their makeup and what makes them special. She uses the Karl G. Jansky Very Large Array in New Mexico to look for radio emissions coming from the planet’s core.
We explore the large planets’ invisible cloud layers at radio wavelengths. Observations below these cloud layers are necessary to restrict the planet’s true atmospheric composition, a crucial variable for planet formation models, because chemical processes and dynamics will change the composition of a planet’s atmosphere. “Radio observations help characterize dynamical, physical, and chemical processes, including heat transport, cloud formation, and convection in the atmospheres of giant planets on both global and local scales.”
De Pater, Li, and graduate student at UC Berkeley Chris Moeckel discovered anomalies in the concentration of ammonia gas in the atmosphere, which they linked to the occurrence of megastorms in the planet’s northern hemisphere in the past, as reported in the new study.
The study claims that ammonia concentrations are lower at midaltitudes, just below the top ammonia-ice cloud layer, but have increased at lower altitudes, 100 to 200 kilometers deeper in the sky. They postulate that the mechanisms of precipitation and reevaporation are how ammonia is transferred from the higher to the lower atmosphere. Additionally, that impact may endure for hundreds of years.
The study also showed that Saturn and Jupiter are very different from one another, despite the fact that both gas giants are composed of hydrogen. Although there are tropospheric anomalies on Jupiter, they have been linked to the planet’s zones and belts and are not brought on by storms like they are on Saturn. The vast differences between these nearby gas giants are upending current theories about how megastorms develop on gas giants and other worlds and could have an impact on how they are discovered and investigated on exoplanets in the future.
More information: Cheng Li, Long-lasting, deep effect of Saturn’s Giant Storms, Science Advances (2023). DOI: 10.1126/sciadv.adg9419. www.science.org/doi/10.1126/sciadv.adg9419
