Testing Models for the Formation of the Equatorial Ridge on Saturn’s Moon Iapetus via Crater Counting

The equatorial ridge on Saturn’s moon Iapetus is likely attributed to a key event in the evolution of Iapetus. Various models of ridge formation have been proposed. In this study, I test these ridge formation models by exploring the population of impact craters on the surface of Iapetus. The objectives of this study are to compile a database of crater populations on and around the ridge, assess the age of the ridge, and test the various ridge formation models. The completed database contains 7,748 craters. Comparison of the crater size-frequency distributions show that the ridge is depleted in larger craters with an enhanced small crater population up to saturation. One possible interpretation is that the ridge is relatively younger in age with an enhanced small impactor population. The exogenic impact generated ridge formation model appears most likely as it is the only model that produces a younger ridge with an enhanced small crater population.