While Jupiter is known for its turbulent weather, Saturn also boasts enduring megastorms. In the new study, titled "Long-Lasting, Deep Effect of Saturn's Giant Storms" published in Science Advances, researchers report that century-lasting megastorms in the sixth planet of the Solar System are leaving lasting atmospheric scars.
In this handout from NASA, the planet Saturn is seen backlit by the sun, sent Cassini spacecraft July 19, 2013 in space.
Mapping Ammonia in Saturn's Atmosphere
Researchers from the University of Michigan led by Cheng Lu studied Saturn's emitted radio waves, unveiling enduring imprints from colossal storms, including historical equatorial ones. This revelation provides captivating knowledge about Saturn's dynamics and potential links to periodic megastorms.
Li said in a news release that comprehending Solar System's grandest storms broadens cosmic insights and redefines terrestrial meteorology by questioning hurricane theories.
Beyond its striking ring system, Saturn appears unremarkable in visible light. Yet, in radio frequencies, vibrant bands encircle the planet, revealing its dynamic atmosphere. As radio waves are impeded by ammonia, this unique view enables astronomers to chart Saturn's atmospheric ammonia distribution.
Li and his team conducted intricate radio assessments of Saturn using the National Radio Astronomy Observatory's Very Large Array, to investigate ammonia's distribution within the atmosphere.
Saturn's composition chiefly comprises hydrogen and helium, with minimal amounts of water, methane, and ammonia. However, ammonia predominates in the upper cloud layer. Radio observations permit scientists to delve beneath this upper layer, unveiling the underlying conditions. It is at this point that the researchers made an intriguing discovery.
Anomalous Ammonia Concentrations Found in Saturn's Atmosphere
Astronomer Imke de Pater from the University of California Berkeley explains in the news release that radio wavelengths enable exploration beneath the visible cloud layers of massive planets. Understanding a planet's authentic atmospheric composition, vital for planet formation models, necessitates observations below these clouds due to chemical changes and dynamics.
Radio observations aid in comprehending the dynamic, physical, and chemical processes such as heat distribution, cloud generation, and convection within the atmospheres of giant planets, offering insights on both a global and local scale.
In their radio images, the more luminous bands indicate lower ammonia concentrations within them. While anticipated ammonia presence was observed in Saturn's upper cloud layer, the team also detected unusual ammonia concentrations situated 100 to 200 kilometers below the surface.
The intermediate zone between these layers exhibited comparably low ammonia content. Their analysis implies that the periodic megastorms occurring approximately every 28 to 30 years on Saturn lead to ammonia sinking into the deeper atmosphere, subsequently evaporating and reemerging at the cloud tops.
Consequently, the concentrated ammonia levels in these depths serve as enduring evidence of historical megastorms that persist for extensive periods, long after the storms themselves have dissipated.
The researchers successfully linked anomalies to all six megastorms documented on Saturn since 1876 and even identified an anomaly connected to an older megastorm. The team's findings emphasize the greater dissimilarity between Jupiter and Saturn. While temperature anomalies on Jupiter are linked to its alternating bands of clouds, Saturn's anomalies are tied to its storms.
This insight provides a clue for understanding the diverse evolution paths of gas giant exoplanets. As a new megastorm is anticipated within the next 10 to 20 years, the prospect of fresh insights is truly captivating.
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