1. Dome Craters on Ganymede and Callisto May Form by Topographic Relaxation of Pit Craters Aided by Remnant Impact Heat
- Author
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Caussi, M. L., Dombard, A. J., Korycansky, D. G., White, O. L., Moore, J. M., and Schenk, P. M.
- Abstract
The icy Galilean satellites display impact crater morphologies that are rare in the Solar System. They deviate from the archetypal sequence of crater morphologies as a function of size found on rocky bodies and other icy satellites: they exhibit central pits in place of peaks, followed by central dome craters, anomalous dome craters, penepalimpsests, palimpsests, and multi‐ring structures. Understanding the origin of these features will provide insight into the geophysical factors that operate within the icy Galilean satellites. Pit craters above a size threshold feature domes. This trend, and the similarity in morphology between the two classes, suggest a genetic link between pit and dome craters. We propose that dome craters evolve from pit craters through topographic relaxation, facilitated by remnant heat from the impact. Our finite element simulations show that, for the specific crater sizes where we see domes on Ganymede and Callisto, domes form from pit craters within 10 Myr. Topographic relaxation eliminates the stresses induced by crater topography and restores a flat surface: ice flows downwards from the rim and upwards from the crater depression driven by gravity. When the starting topography is a pit crater, the heat left over from the impact is concentrated below the pit. Since warm ice flows more rapidly, the upward flow is enhanced beneath the pit, leading to the emergence of a dome. Given the timescales and the dependence on heat flux, this model could be used to constrain the thermal history and evolution of these moons. Ganymede and Callisto are large icy moons orbiting Jupiter, believed to be ocean worlds. These moons' surfaces display impact craters with shapes not seen elsewhere in the Solar System. This may be due to factors such as their high gravity, temperature, presence of subsurface oceans, and/or impactor characteristics. By exploring these atypical craters, we aim to shed light on the inner workings and evolution of these moons and, by extension, contribute to a clearer picture of the evolution of the outer Solar System. This study focuses on unveiling the origins of dome craters on Ganymede and Callisto, which have rounded bright domes in the center and are virtually unique to these moons. We believe these domes are connected to a relatively more common crater, the pit crater. Our simulations show that a pit crater can evolve into a dome crater within 10 million years as the ice flows slowly under its own weight. This flow is channeled back into the center creating a dome, aided by warm temperatures left over from the impact that soften the ice below the pit. This occurs only for the specific sizes where we see dome craters on these moons. Dome craters form via topographic relaxation of pit craters for sizes larger than ∼60 kmRemnant heat from the impact enhances relaxation at the center of the pit crater, causing domes to emergeEven young dome craters can form from the relaxation of pit craters due to the relatively short timescales required (∼10 million years) Dome craters form via topographic relaxation of pit craters for sizes larger than ∼60 km Remnant heat from the impact enhances relaxation at the center of the pit crater, causing domes to emerge Even young dome craters can form from the relaxation of pit craters due to the relatively short timescales required (∼10 million years)
- Published
- 2024
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