Relative Crater Scaling Between the Major Moons of Saturn: Implications for Planetocentric Cratering and the Surface Age of Titan

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AbstractThe chronology of the moons of Saturn, especially Titan, has been limited by a lack of strong constraints on the cratering rate, low number statistics for small‐N counts of large‐diameter craters, and uncertainty about whether impactors are mostly heliocentric impactors orbiting the Sun or planetocentric impactors orbiting Saturn itself. Here, I propose to address these three problems. Instead of looking for an absolute cratering rate, I focus on the relative crater densities, calculating scaling relationships between the moons. I update crater analysis methodology by numerically modeling probability density functions of the uncertainty of crater density, enabling me to accurately assess the error of even single‐crater observations. Using these updated statistics, I show how the heliocentric cratering model leads to a dramatic increase in relative crater density for Mimas, Tethys, Dione, Rhea, and Iapetus with distance from Saturn. Under this model, the surface age of Titan is probably older than the cratered plains of Mimas—implying a very low erosion rate and minimal endogenic resurfacing on Titan. I explore possible explanations, concluding that the likeliest explanation is planetocentric cratering, although saturation effects cannot be ruled out. Under the planetocentric model, the relative crater densities of the cratered plains of Mimas, Tethys, Dione, Rhea, and Iapetus are all very close, with the relative crater density at Titan between 1 and 2 orders of magnitude lower. Under planetocentric cratering, the cratering rate on Titan allows for vigorous erosion and endogenic resurfacing.