Ganymedean pedestal craters distribution: Implications on thermal and tectonic histories

The distribution analysis of the ganymedean pedestal craters shows a very good correlation between them and the grooved terrains. These craters seem to be the earliest post-grooved impacts. The presence of tectonized pedestal craters is also noted. This type of crater is the only one lying on the grooved terrains and being affected by the grooves. Assuming that a lowering of the terrain's viscosity is the determining factor for the presence of pedestal craters, we conclude that at the time of their formation, the grooved terrains have a lower viscosity than the other terrains. Moreover, using the density ratio between non-pedestal craters and pedestal craters, a relative low viscosity state's duration time is calculated. Based on the density ratio between pedestal craters and tectonized pedestal craters, a grooved terrains formation's time is also calculated. These two times are of the order of 10⁷ yr and 10⁶ yr respectively. This period of low viscosity may be partly due to internal heating.