The exploration of the outer solar system in the last decades revealed an exotic icy world with surfaces showing the most diverse geology, sometimes exceptional to these icy bodies due to the peculiar rheology of ice. Each of these icy bodies exhibits unique characteristics and its own fascinating geological history - formed by the competition of external and internal forces. Some satellites are still geologically active today while others appear to be mostly inactive at present time. Geologically old surfaces are heavily cratered. Some projectiles which created large craters or basins were massive enough that they could have destroyed the target body, like in the case of the impact crater Herschel on the Saturnian satellite Mimas. The observed impact crater morphologies are often exclusive to icy bodies like impact craters on the Galilean satellites Ganymede and Callisto. They mirror the target properties at the time of impact and thus help to understand the satellite's geological evolution. They also reflect the external influence of the space environment onto the surface material since the impact occurred, which is of major importance since most of these icy bodies do not exhibit an atmosphere. Tectonic resurfacing can often be observed as widely distributed simple extensional fractures. Satellites that experienced a more intricate tectonic resurfacing also show more complex tectonic features like double ridges on the Jovian satellite Europa, the Saturnian satellite Enceladus as well as Neptun's satellite Triton. Peculiar tectonic features that are restricted to a single satellite include Europa's bands and chaotic terrain as well as Miranda's coronae indicating outstanding geological evolutions of these two bodies. These complex features are far from being fully understood. They are, at least partly, expected to be associated with recent and/or past cryovolcanism. Current volcanism, however, has been detected only on the two satellites Enceladus and Triton, finding its peak in geysers on Enceladus originating from its south pole forming vapor plumes that reach up to 500 km into space.
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