Origin of Saturn’s small moons

Are Saturn’s small moons the children of Saturns rings  ?

S. Charnoz, J. Salmon, A. Crida

The main moons that orbit the giant planets are thought to have finished forming when their planets did, about 4.5 billion years ago. Yet some of Saturn’s small moons are too young (less than 10 million years old) for this to have been the case.

One possibility is that the moons formed at the edge of Saturn’s rings — aggregates of ice particles as well as some rocky debris and dust. But until recently, insufficient computing power made it impossible to model how this process might have occurred.

In this week’s Nature, Sébastien Charnoz and colleagues use a hydrodynamical model to follow the evolution of the rings, and an orbital model to track the birth of the moonlets and assess how their formation is affected by the other rings and Saturn itself.

Through their hybrid simulation, the group show how the spreading of Saturn’s rings beyond the Roche limit (the distance from the planet beyond which the rings become gravitationally unstable) could have given rise to the small moons.

Contact : Sébastien Charnoz (charnoz@cea.fr)

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Small satellites of Saturns (Cassini/NASA/JPL/SSI)

The edge of Saturn’s rings , Prometheus and the F ring (images Cassini/NASA/JPL/SSI)