| 研究実績の概要 |
This study aims to determine the age of the giant planets' regular satellites and the cratering/impacting rate of the outer solar system. Our recent efforts have focused on the icy regular satellites of Saturn. To achieve this, we used high-resolution outer solar system evolution simulations and improved estimates of the number of trans-Neptunian objects from the literature. This enabled us to calculate model surface ages of the most heavily cratered terrains on icy satellites, which have implications for understanding the formation and tidal evolution of these satellites.
We found that the surface ages of the cratered plains on Mimas, Enceladus, Tethys, Dione, and Rhea range from 4.1 Ga to 4.4 Ga, with the surfaces of Mimas and Enceladus being roughly 200 million years younger than the outer three satellites. The calculated model surface ages are consistent with the idea that Saturn's regular satellites are ancient and have implications for their formation and tidal evolution. This work provides updated isochrons (please refer to the figures) for the observed crater size-frequency measurement of the icy satellites and supports the current understanding of the satellites' formation and evolution.
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