An interconnected system
In the years following the end of the Cassini mission, scientists have come to appreciate that it’s impossible to consider any part of the Saturn system on its own.
“It’s a real interconnected system where everything interacts with everything else,” said Matthew Hedman, an associate professor of physics at the University of Idaho who was a Cassini participating scientist.
Hedman published data that helped solve a longstanding mystery about Saturn: How long is a day on the ringed planet?
On a terrestrial planet like Earth, this question can be answered by watching landforms make a lap around the planet. Since gas giants like Jupiter and Saturn have no landforms, an alternative way to determine the length of a day is by tracking how long it takes one of the planet’s magnetic field poles to travel around the planet.
Unfortunately, that doesn’t work on Saturn because the magnetic field pole is aligned almost perfectly with the planet’s rotation axis, meaning the magnetic pole hardly moves at all.
So scientists tried something different: They learned that Saturn’s interior vibrates like a bell, creating variations in its gravitational field. These variations show up as waves in the planet’s rings. By tracking these waves, scientists were able to determine that a Saturn day lasts 10 hours, 33 minutes, and 38 seconds.
Studying the frequency of the ring waves may also yield clues about Saturn’s interior, including what its core is like.
“If the planet’s more centrally condensed, it rings at one frequency. If its center is puffier, it rings at other frequencies,” Hedman said.