Impact-driven Resurfacing at Antum Crater (Ganymede)

Kurzfassung

The icy crust of Ganymede, Jupiter’s largest moon, preserves evidence of complex interactions among impact, tectonic, and chemical processes. Antum Crater, a 25-km dark-rayed feature located in Marius Regio, offers a valuable case study to investigate these dynamics. By integrating Galileo and Voyager geological mapping, spectral analysis from the Near Infrared Mapping Spectrometer (NIMS), and iSALE2D impact simulations, this study reconstructs Antum’s formation and explores its implications for Ganymede’s subsurface volatile inventory. Geological mapping based on a 359 m/pixel global mosaic identifies three distinct albedo-defined facies within the Antum crater region. The oldest terrain is densely fractured, while the crater’s ejecta display progressively darker albedo with distance, indicating stratigraphic differences or compositional gradients. A revised crater rim diameter of 25 km—significantly larger than previous estimates of 15 km based on the inner dark rim—and an asymmetric ejecta pattern suggest a south-southeast to north-northwest impact trajectory. This directional asymmetry is consistent with the redistribution of dark-rayed material enriched in non-ice components.