Some surprises from the rings and the atmosphere of Saturn

Some details of Saturn rings (Image NASA/JPL-Caltech/Space Science Institute)
Some details of Saturn rings (Image NASA/JPL-Caltech/Space Science Institute)

During the American Astronomical Society Division for Planetary Science meeting some of the latest discoveries were presented about the planet Saturn and its rings obtained from data collected by the Cassini space probe before disintegrating in the planet’s atmosphere on September 15. Some of the results were published in “The Astrophysical Journal”.

During the final months of its mission, the Cassini space probe performed maneuvers riskier than in previous years boldly going where no one had gone before. That Grand Finale allowed, for example, to gather even more detailed information about the gap between Saturn and its rings and the planet’s atmosphere. These data were added to the considerable wealth accumulated over the years and several researchers gained new insights with their research.

Saturn’s rings are the most recognizable feature of the planet and one of the most spectacular features of the entire solar system but not all is clear about their formation and duration. The data collected during the dives into the gap between Saturn and its rings, including photos from new angles, allowed researchers to obtain new details on the structures called “propellers”, wakes generated by some small moons of the planet that have similarities with the processes of planet formation within disks of gas and dust around young stars.

The Cassini space probe captured images of six propellers whose orbits were traced over the last years of the mission. They were given names of famous aviators: Blériot, Earhart, Santos-Dumont, Sikorsky, Post and Quimby. However, during the months that preceded the Grand Finale, Cassini also captured the images of smaller propeller swarms and this surprised the researchers.

Another study concerning Saturn’s rings was conducted through computer simulations to better understand the forces that prevent them from spreading out. According to the results, their stability is aided by various moons of the planet: according to the old models it was Janus that exerted the forces that stabilized in particular the ring A but the simulations indicate that Pan, Atlas, Prometheus, Epimetheus, Pandora, and Mimas are also involved.

The space between Saturn and its rings might seem like an empty and dull place but it’s actually interesting as well and during its dives inside it, the Cassini space probe used its Ion and Neutral Mass Spectrometer (INMS) to directly detect the components in the planet’s atmosphere’s upper layers for the first time. That’s because they stretch almost to the rings.

The researchers had a confirmation of the presence in the atmosphere of materials from the rings but the findings show that there are also compounds more complex than the water that represent the main component. A surprise came from an abundance of methane, unexpected in the rings or in the upper layers of the planet’s atmosphere. The final detections at lower altitudes show an even greater complexity and variability and researchers are very busy analyzing those final data.

Another study concerns Saturn’s magnetic field and aims to understand if it has a tilt and determine the exact length of the planet’s day, which is still not well measured. Again, Cassini’s final detections can be crucial because of the space probe’s greater proximity to Saturn. The results of these data’s analysis will influence future studies not only on this planet but also on the generation of planetary magnetic fields.

Saturn’s magnetic field studies also include those of his auroras. On September 14, 2017, the day before its fall into planet’s atmosphere, the Cassini space probe’s Ultraviolet Imaging Spectrograph (UVIS) captured ultraviolet emissions from the northern polar region’s aurora.

It’s normal that the data accumulated during a space probe’s mission keep on being studied for a long time after its end. In the case of the Cassini mission, research can continue for several years.

Aurora at Saturn's north pole (Image NASA/JPL-Caltech/University of Colorado/ University of Liege-LPAP)
Aurora at Saturn’s north pole (Image NASA/JPL-Caltech/University of Colorado/ University of Liege-LPAP)

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