Geological, compositional and crystallinity analysis of the Melkart impact crater, Ganymede

Abstract

In this work, we analyze the ∼103 km-diameter Melkart impact crater on the surface of Ganymede, which is a ∼ 103 km impact crater located at the boundary between the two main geological units of the satellite, the light and dark terrains. Such crater is covered both by Galileo SSI and NIMS datasets allowing inference of any possible correlation between its geology and composition, as well as to investigate the evolution of the substrate units. We provide a geomorphological characterization of the crater by creating a high-resolution geological map, investigating the DTM and performing a strain analysis to infer its deformation. We find that the Melkart dome underwent strike-slip deformation with right-lateral kinematics. Moreover, this crater is a low strain end member with subtle deformation, which has been formed in an area of gradual transition between light and dark terrains. The results obtained through band depth and crystallinity maps of the study area do not reflect the evolutionary history of the crater, instead, they are representative of the different geological terrains affecting the subsurface of Melkart. Such result implies that the possible compositional differences between the crater's units might have been obliterated through time. Our analysis supports the interpretation that the material constituting the substrate of the crater might be heterogeneous suggesting that: (i) the transition between the two geological units might be gradual or ii) the dark material located over the study area only represents a thin layer draping the icy crust.