The Saturnian seasons are beautifully documented by the James Webb Space Telescope, showcasing the changes that occur on the planet.
The source of this information is the Journal of Geophysical Research: Planets.
The arrival of winter is approaching, not just for the Northern Hemisphere of Earth. Saturn, which completes its orbit around the Sun every 30 years, is also nearing the end of its summer season after approximately 7.5 years. Its fall equinox is expected to occur in 2025.
According to Fletcher et al., the weather on Saturn, like Earth, varies with its changing seasons. Recent images taken by the Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST) reveal the shifts in Saturn’s atmospheric dynamics since the end of the 13-year mission of the Cassini-Huygens spacecraft in 2017.
In December 2021, the JWST was launched and in November 2022 it aimed to observe Saturn. The purpose of this was to test MIRI’s ability to capture images of the planet’s large size, fast rotation, distinct rings, and high infrared brightness, which differ from MIRI’s previous targets. By using MIRI, researchers were able to piece together infrared images of Saturn and create a map of its northern hemisphere during summertime.
It seems that MIRI has successfully completed the examination. The pictures accurately depicted the composition of Saturn’s clouds and enabled scientists to analyze the varying temperatures and chemicals present in the atmosphere, uncovering several significant seasonal variations.
For example, the pictures demonstrate that the north polar stratospheric vortex of the planet, which is a high-altitude flow of gases that was initially discovered by Cassini during Saturn’s spring, experienced an increase in temperature during the summer. As winter approaches, it is expected to cool down and disperse.
The pictures also showcase a total shift in the direction of air movement in Saturn’s stratosphere, which was noticed by Cassini during the northern winter. During this time, a significant amount of air moved upward in the southern hemisphere, passed over the equator, and descended to lower altitudes in the northern hemisphere. This process led to an increase in gases such as hydrocarbons in the air. However, recent data from the MIRI indicate that now, the air is moving upward in the north and flowing south, resulting in a decrease in hydrocarbons at northern latitudes. This circulation pattern may continue to evolve as fall approaches.
Due to MIRI’s impressive sensitivity and capability of capturing light wavelengths previously inaccessible to Cassini, the latest images provide a first-time mapping of various gases such as water in the troposphere and ethylene, benzene, methyl, and carbon dioxide in the stratosphere. Additionally, the images show a significant presence of ammonia at the equator, indicating potential similarities in processes between Saturn and the gas giant Jupiter.
These discoveries offer the initial insight into the late summer season in the northern region of Saturn and showcase the impressive capabilities of JWST and MIRI. (Journal of Geophysical Research: Planets, https://doi.org/10.1029/2023JE007924, 2023)
“I am a science writer named Sarah Stanley.”
The publication titled “James Webb Space Telescope captures Saturn’s changing seasons” was written by Stanley in 2023 and was featured in Eos, volume 104, on September 28, 2023. The DOI for this article is https://doi.org/10.1029/2023EO230371.
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