The rings, which revolve around Saturn, clearly indicate that the planet’s axis of rotation is tilted: the Angle between Saturn’s axis and the plane around the sun is 26.7°.
So why does Saturn tilt?
What does Titan do?
Scientists have proposed that Saturn’s tilted axis is the result of the planet’s gravitational control (that is, resonance with Neptune). However, data from the Cassini spacecraft, which orbited Saturn from 2004 to 2017, challenges this view. The data suggest that Saturn’s largest moon, Titan, is growing about 11 centimeters closer to Saturn each year. That’s faster than scientists thought, and Titan’s rapid migration and its gravitational pull have led scientists to speculate that Titan may have caused Saturn to tilt and Saturn to resonate with Neptune.
Some of Saturn’s large existing moons
But that view depends on one premise: Saturn’s moment of inertia, the pattern of mass distribution inside the planet. The inclination of Saturn will be different if the mass is more concentrated in the core or more distributed near the surface. Therefore, to determine the cause of the tilt of Saturn’s axis, we must first know the distribution pattern of mass within Saturn.
Investigate Saturn’s moment of inertia
In a recent study, scientists used Cassini’s final observations during its “Grand Finale,” during which it came closest to Saturn in order to accurately map the planet’s entire gravitational field, to determine Saturn’s moment of inertia. In fact, there is a direct correlation between Saturn’s gravitational field and Saturn’s moment of inertia.
By modeling what’s going on inside Saturn, scientists identified a type of moment of inertia that matches the gravitational field Cassini observed. But they were surprised to find that this moment of inertia would cause Saturn to almost resonate with Neptune, without actually resonating. It also means that the two planets might once have resonated, but no longer do.
This mysterious moon exists only in the imagination of scientists
A moon may have caused the tilt of Saturn’s spin axis (schematic)
Next, scientists explored ways to get Saturn out of resonance with Neptune. They started with simulations of orbital dynamics that trace the evolution of Saturn and its moons to investigate whether there are any natural instabilities between Saturn’s current moons that could affect the tilt of the planet. However, this line of thinking does not work. So scientists took a second look at the mathematical model that describes Saturn’s precession — how a planet’s spin axis changes over time. Scientists speculate that if one of Saturn’s moons broke away from the entire population of Saturn’s moons, it could change the planet’s precession.
A lost Chrysalis
The question is: How massive would this moon have to be, and what orbital dynamics would it have to have to knock Saturn out of resonance with Neptune? The scientists ran repeated simulations to determine the Saturnian moon’s mass, orbital radius and the orbital dynamics needed to cause it to lose its resonance with Neptune. They concluded that Saturn’s current tilt was the result of its resonance with Neptune and the loss of one of its moons. Scientists call the moon Chrysalis (Chrysalis). If Chrysalis is the same size as Iapetus, Saturn’s third largest moon, it could keep Saturn from resonating with Neptune.
Mysterious Moon May Have Turned into Saturn’s Rings
Based on new simulations, scientists suspect that after orbiting Saturn for billions of years, about 160 million years ago, Clisaris entered a chaotic orbital zone, passed Iapetus and Titan (too close), and eventually passed Saturn, only to be torn apart by the planet’s massive gravity, with some debris crashing into the planet and some orbiting it, Eventually became Saturn’s rings.
It needs to be further tested
Scientists say the disappearance of Chrysalis could explain Saturn’s precession as well as its present tilt and the formation of its rings. Scientists had previously estimated that Saturn’s rings were about 100 million years old. Now they don’t look that young, but they’re still much younger than Saturn. Also, because Chrysalis had been hibernating for so long before suddenly becoming active, eventually leading to the emergence of Saturn’s rings, the name Chrysalis was just right for it.
Scientists note that while the chrysalis hypothesis may be the best explanation yet for Saturn’s tilt and rings, it needs further testing and more evidence.
