Cassini might be dead but its legacy lives on. Several groups of researchers are working hard on the data from the mission’s grand finale and the first results are now coming out. New details about the ringed planet are presented today at the American Astronomical Society Division for Planetary Sciences meeting.
The Grand Finale brought the probe closer to Saturn's atmosphere and rings than ever before and the latest analysis helps us solve some their mystery. Of particular importance is a study on how the rings keep their shape.
Making sure the rings don’t disperse into space is apparently a group effort. Several moons, including Pan, Atlas, Prometheus, Pandora, Janus, Epimetheus, and Mimas, are the keepers of Ring A, for example, making sure it doesn’t spread out. The dynamics of the rings are also related to how they formed and how old they are.
Analyses suggest that without any confining force, Saturn’s rings should spread out and disappear over a few hundred million years. If this were the case, they would have to be much much younger than the planet itself.
The new research instead highlights how the moons create intricate waves in the rings. Their full effect actually dampens the rings' tendency to spread out. The study was led by Radwan Tajeddine of Cornell University and will be published in The Astrophysical Journal this week.
More research is about the propellers – peculiar features in the rings caused by the motion of tiny moons. Researchers were able to track the motions of six of these propellers and they argue that they appear to behave as we'd expect baby-planets to.
The extremely close flybys have also shed new light on the chemical makeup of Saturn’s upper atmosphere. Cassini used the Ion and Neutral Mass Spectrometer, its electronic nose, to discover that molecules from Saturn's rings – even complex ones – rain down on the planet.
Finally, Professor Michele Dougherty from Imperial College London gives an update on the mystery surrounding Saturn’s day length. We don’t know precisely how long it takes Saturn to rotate on its axis and a usual approach is to study its magnetic tilt. Saturn appears to have a tiny tilt but we don’t have an explanation for how it works, suggesting there are some complex mechanisms at play.
"There are whole careers to be forged in the analysis of data from Cassini," Linda Spilker, the mission's project scientist at NASA's Jet Propulsion Laboratory, said in a statement. "In a sense, the work has only just begun."
Cassini finished its 13-year mission around Saturn on September 15 of this year. It was a joint project between NASA, the European Space Agency, and the Italian Space Agency.