AGU: Geophysical Research Letters

 

Editors' Highlight

The equatorial ridge on Saturn's moon Iapetus: Formation through ring collapse?

The most recent observations made by the Imaging Science Subsystem (ISS) device aboard the Cassini spacecraft showed that the third-largest Saturnian satellite, Iapetus, has a curious ridge system exactly aligned with the equator. Some scientists believe that this ridge system is the result of tectonic stress caused by despinning of the proto-Iapetus from a rotational period of a few hours to the present configuration, where it spins in synchronous rotation with Saturn over a period of 79 days. Ip (2006) proposed a different hypothesis, suggesting that because Iapetus has large gravitational influence despite perturbations from Saturn, a ring system might have been present during its formation. The author further hypothesized that as the rotational period of Iapetus lengthened, this ring collapsed and ring particles collided onto Iapetus, forming the equatorial ridge system. Ip noted that if correct, this hypothesis could potentially shed new light on the origin of Iapetus as well as on satellite formation in general.

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