It’s amazing what a little basic physics can do with a rocky world. Now, those gassy ones, they and their lack of solid surface are a bit more of a challenge.

Saturn’s rotational period has confused scientists since the Voyager missions flew by it in the 1980s. At that time, Saturn’s day was calculated at just over ten and a half hours. When Cassini entered orbit twenty years later, it calculated a slightly shorter value.

There are two possible theories to explain why this happens. One had to do with the magnetosphere, and Saturn has a very strong one. The other theory is about its winds. 

In 2017, a team from the University of Leicester with first author Nahid Chowdhury used one of the Keck telescopes to measure the speed of Saturn’s winds through the spectrum of a specific hydrogen ion. It turns out that they spin really fast – 7,000 kilometers per hour. This incredible speed changes the magnetosphere enough that it distorts the radio signals the scientists had been using to measure Saturn’s rotational period. So parts of both theories were right in how the observed change in the rotational period happened. This research was published in Geophysical Research Letters.

More Information

Saturn’s Powerful Winds Explain Changes in the Length of Its Day (Eos)

“Saturn’s Weather-Driven Aurorae Modulate Oscillations in the Magnetic Field and Radio Emissions,” M. N. Chowdhury et al., 2021 December 28, Geophysical Research Letters