Once every saturnian year, a giant storm included of white cloud activity seen in the center that eventually wrap around the planet. The storm was a recurring event that occurred at 28.5-year periods when Saturn’s northern hemisphere was tilted most toward the sun. Eruptions from the cloud decks left an everlasting imprint on the planet’s complexion.
The Cassini mission captured the greatest and most powerful storm ever seen on Saturn, known as the white spot or the giant northern storm. It was a perfect coincidence that Cassini happened to be orbiting Saturn during the storm, offering an unprecedented opportunity to study the gas giant’s turbulent weather and climate patterns. This storm have been so immense and powerful that it was able to disturb the atmosphere at the planet’s equator some tens of thousands of kilometres away. This gigantic storm which captured by the spacecraft began in late 2010 and lasted for more than 6 months; it was the cause of unusual temperatures, clouds, and atmospheric composition on Saturn.
The newest study by University of Michigan researcher Cheng Li, discovered that the peculiar aspect of the last giant storm on Saturn is its “dehydration” effect, referring to the observation that the storm depletes the condensable vapors in the atmosphere, in particular, the ammonia vapor. The vapor can linger for centuries like a footprint to mark the storms. Li et al examined the long-term evolution of the atmosphere of Saturn after the 2010 storm using the upgraded Karl G. Jansky Very Large Array (VLA) and focused the analysis on the northern hemisphere where the line of sight was free of ring materials. The uppermost cloud decks which are mostly ammonia, floating in the atmosphere of hydrogen.
Li et al say it carried ammonia from high-altitude clouds into the lower layers of the atmosphere — where it’s now stuck.
This disruption of the long-term, cyclical, continuing atmospheric patterns at mid-latitudes (dubbed informally by some as the planet’s ‘heartbeat’), is thought to be due ‘teleconnection’, which we also observe on Earth — when distant events within a climate system are somehow connected and can influence one another significantly.
Saturn's 'Great Springtime Storm' in visible light.
Credit: NASA/JPL-Caltech/Space Science Institute
Such storms have been observed on Saturn over the past 140 years, alternating between the equator and midlatitudes.
1876 — Observed by Asaph Hall. He used the white spots to determine the planet’s period of rotation.
1903 — Observed by Edward Bannard
1933 — Observed by Will Hay, comic actor and amateur astronomer.
1960 — Observed by JH Botham
1990 — Observed by Stuart Wilber
1994 — Studied by ground-based observers and the HST
2006 — Observed by Erick Bondoux and Jean-Luc Dauvergne.
2010 — Observed by Anthony Wesley, photographed by Cassini Probe 2010–11.
Additional research and observations will definitely offer glimpses into how these storms form on Saturn. The next enormous storm could happen in a few years, and radio astronomy these days should allow us to learn how Saturn’s deep layers give rise to storms on the planet’s surface.
References
Cheng Li et al. Long-lasting, deep effect of Saturn’s giant storms. Sci. Adv.9,eadg9419(2023).DOI:10.1126/sciadv.adg9419
Fletcher, L.N. Saturn’s big storm. Nat Astron 1, 583 (2017). https://doi.org/10.1038/s41550-017-0246-6
“ESA Science & Technology - Saturn’s giant storm reveals the planet’s churning atmosphere,” 2012. https://sci.esa.int/web/cassini-huygens/-/50994-saturn-s-giant-storm-reveals-the-planet-s-churning-atmospherel
“ESA Science & Technology — Saturn’s greatest storm,” Esa.int, 2018. https://sci.esa.int/web/cassini-huygens/-/60033-saturn-s-greatest-storm (accessed Aug. 23, 2023).
“Explaining Saturn’s Great White Spots,” California Institute of Technology, 2015. https://www.caltech.edu/about/news/explaining-saturn-s-great-white-spots-46500.
Cheng Li, Andrew P. Ingersoll. Moist convection in hydrogen atmospheres and the frequency of Saturn’s giant storms. Nature Geosci 8, 398–403 (2015). https://doi.org/10.1038/ngeo2405
K. Smith, “The Aftermath of Saturn’s Giant Storms Lasts for Centuries,” Inverse, Aug. 15, 2023. https://www.inverse.com/science/saturns-giant-storms-lasts-for-centuries (accessed Aug. 23, 2023).