Geomorphology of Impact Features on Tethys Using High Resolution Mosaics
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Abstract
The cratering record on Tethys provides much-needed constraints on the formation timescale and mechanism of the mid-sized icy moons of Saturn. However, most geologic mapping studies have focused on the large impact basin, Odysseus, and the canyon system, Ithaca Chasma. Recently, work by the authors showed that ejecta fragments from primary impacts onto either of Tethys' coorbital moons are very likely to impact Tethys. The distribution, impact velocities, and impact angles of the debris are spatially-variable. In particular, high-velocity debris (>5 km/s) with low impact angles are highly clustered along the equator in Tethys' leading hemisphere. Slower impacts would be more evenly distributed across the surface of Tethys. Here, we use high resolution Cassini ISS images to look for impact features that may have resulted from coorbital debris, including elongated craters, grooves, and pit chains. In addition, we map features in two areas - one in which Schenk et al. would predict clustered, higher-velocity, oblique impacts and one on the opposite side of Tethys, where we would expect a sparser and more variable population of impactors.