The tilt of the rotation axis of the gas giant Saturn may in fact be caused by its moons, scientists from CNRS, Sorbonne University and the University of Pisa have reported (Nature Astronomy). The current tilt of Saturn’s rotation axis is caused by the migration of its satellites, and especially by that of its largest moon, Titan.

Recent observations have shown that Titan and the other moons are gradually moving away from Saturn much faster than astronomers had previously estimated. By incorporating this increased migration rate into their calculations, the researchers concluded that this process affects the inclination of Saturn’s rotation axis: as its satellites move further away, the planet tilts more and more.

In fact, Saturn’s axis is still tilting, and what we see today is merely a transitional stage in this shift. Over the next few billion years, the inclination of Saturn’s axis could more than double.

The decisive event that tilted Saturn is thought to have occurred relatively recently. For over three billion years after its formation, Saturn’s rotation axis remained only slightly tilted. It was only roughly a billion years ago that the gradual motion of its satellites triggered a resonance phenomenon that continues today: Saturn’s axis interacted with the path of the planet Neptune and gradually tilted until it reached the inclination of 27 degrees observed today, says a release from CNRS.

Scientists already are in agreement about the existence of this resonance but it was so far believed that it had occurred very early on, over four billion years ago, due to a change in Neptune’s orbit. Since that time, Saturn’s axis was thought to have been stable.