Geology
The Odysseus crater is now quite flat for its size of approximately 450 km or more precisely, its floor conforms to Tethys' spherical shape. This is most likely due to the viscous relaxation of the Tethyan icy crust over geologic time. The floor lies approximately 3 km below the mean radius, while its exterior rim is about 5 km above the mean radius—the relief of 6–9 km is not very high for such a large crater. Inside the crater the rim is composed of arcuate scarps and extends for about 100 km until the floor is reached. There are several graben radiating away from Odysseus, which are 10–20 km wide and hundreds kilometers long. They are likely to be cracks in the crust created by the impact. The most prominent among them is called Ogygia Chasma.
The crater must have originally been deep, with a high mountainous rim and towering central peak. Over time the crater floor has relaxed to the spherical shape of the Tethys's surface, and the crater's rim and central peak have collapsed (similar relaxation is apparent on Jupiter's moons Callisto and Ganymede). This indicates that at the time of the Odysseus impact, Tethys must have been sufficiently warm and malleable to allow the topography to collapse; its interior may have even been liquid. If Tethys had been colder and more brittle at the time of impact, the moon might have been shattered, and even if it survived the impact, the topography of the crater would have retained its shape, similar to the crater Herschel on Mimas.
The central complex of Odysseus (Scheria Montes) features a central pit-like depression, which is 2–4 km deep. It is surrounded by massifs elevated by 6–9 km above the crater floor, which itself is about 3 km below the average radius.
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