Current estimates place the ages of the inner Saturnian satellites (Mimas, Enceladus, Tethys, Dione, and Rhea) between 4.5 Gyr and 100 Myr. These estimates are based on impact crater measurements and dynamical simulations, both of which have uncertainties. Models of satellite evolution are inherently simplified and rely on uncertain or unknown parameters, which are often difficult to verify, whereas the interpretations of crater densities depend on the source populations of impactors, which are not well‐constrained in the outer solar system. We investigate the cratering history of Tethys, mapping the population of small impact craters, to determine the roles that planetocentric, heliocentric, or other impact debris play in its cratering record. To map the surface of Tethys, we chose five regions that were located in geographically distinct areas and had high‐resolution (~150 m/pix) image coverage by the Cassini ISS camera. We studied all craters that had at least 7 pixels across but mapped down to 5 pixels for completeness in the crater counts. We observe an abundance of small craters (D < 3 km) in the oldest region; this does not appear to be due to secondary cratering effects from the Odysseus impact basin. Fitting the production functions from Zahnle et al. (2003, https://doi.org/10.1016/S0019‐1035(03)00048‐4), we find that neither their Case A nor Case B scenarios align with the observed cratering record at Tethys. We conclude that in addition to the standard outer solar system impactor populations, there is a Saturn‐centric impactor source that is cratering Tethys.

中文翻译：

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土星的月亮特提斯上的小型撞击坑人口及其对系统中撞击源的影响

目前的估计将土星内部卫星（Mimas，Enceladus，Tethys，Dione和Rhea）的年龄定在4.5 Gyr至100 Myr之间。这些估计是基于撞击坑测量和动力学模拟，两者均具有不确定性。卫星演化模型本质上是简化的，并且依赖于不确定或未知的参数，这些参数通常难以验证，而陨石坑密度的解释取决于撞击源的来源，撞击源的来源在外部太阳系中并不十分严格。我们调查了特提斯的陨石坑历史，绘制了小型撞击坑的地图，确定了平心，日心或其他撞击碎片在陨石坑记录中的作用。要绘制特提斯的表面，我们选择了五个地区，这些地区位于地理上不同的区域，并且通过卡西尼ISS相机具有高分辨率（〜150 m / pix）的图像覆盖率。我们研究了所有陨石坑，这些陨石坑的宽度至少为7个像素，但映射到5个像素以确保陨石坑计数的完整性。我们观察到大量的小火山口（D  <3 km）。这似乎不是由于奥德修斯撞击盆地的二次火山口效应所致。拟合Zahnle等人的生产函数。（2003，https://doi.org/10.1016/S0019-1035(03)00048-4），我们发现他们的案例A和案例B场景都不符合在特提斯观测到的火山口记录。我们得出的结论是，除了标准的外部太阳系撞击物种群外，还有一个土星中心撞击物源正在使特提斯陷坑。