Surface ages of the icy Galilean satellites of Jupiter using an updated impact cratering chronology model

Two spacecraft were launched recently to reach Jupiter and its satellites: (1) ESA’s JUICE Mission (Apr. 14, 2023) and (2) NASA’s Europa Clipper (Oct. 14, 2024). The latter spacecraft is planned to be inserted into Jupiter orbit Apr. 11, 2030 [1]. JUICE will be inserted into Jupiter orbit in 2031 [2], and in 2034 in orbit about the largest satellite Ganymede [2]. While Europa Clipper will focus on intensely studying Europa, JUICE will concentrate on the two largest satellites Ganymede and Callisto. These three satellites are characterized by a wide range of geologic units: Callisto is dominated by old, dark densely cratered plains [3], whereas the surface of Europa is comparably young and dominated by intensely tectonized regions [4]. Ganymede shows both older dark cratered plains and younger light tectonically altered terrains [5]. The true ages of these surface features are still unknown, but age estimations have been carried out, based on measuring crater distributions since the late 1970ies, in Voyager and Galileo SSI imaging data [e.g., 6]. In this study, we continue our work on cratering model age estimations by applying an updated impact chronology scenario [7][8]. The dominant impactors on the surfaces of the Jovian satellites are short-period comets from the Kuiper Belt in the Outer Solar System, termed ecliptic comets (ECs) [7]. In the updated impact chronology, two scenarios, although with high degrees of uncertainties, are discussed [7]: (a) impacts preferentially without disruption of the impactors, and (b) impacts predominantly with disruption. Applying these two scenarios, cratering model ages are obtained from crater distributions on specific geologic terrains. For Ganymede, significantly higher surface ages for specific terrain types – model ages several 100 Myr older – can be derived from the disrupted comet impact scenario compared to a previous version of the chronology [8][9], while changes in model ages are minor for the scenario without comet disruption. Similarily, crater model ages were also found to be higher for geologic units on Callisto in this study, taking into account disrupted comets. The disrupted comet scenario also infers higher model ages for terrains on Europa compared to previous estimates [9]. We will use these model chronology and future updates for geologic studies based on the images returned by the JANUS Camera aboard the JUICE spacecraft. REFERENCES: [1] Pappalardo, R. T. et al.: EGU25-7629 (abstr.), 2025. [2] Vallat, C. et al.: EGU25-21485 (abstr.), 2025. [3] Moore, J. M. et al., in: Bagenal, F. et al. (Eds.), Jupiter, Cambridge Univ. Press, p. 397-426, 2004. [4]. Dogget, T. et al., in: Pappalardo, R. T. et al. (Eds.), Europa, Univ. of Arizona Press, Tucson/Az, p. 137-159, 2009. [5] Jaumann, R. et al., in: Volwerk, M. et al. (Eds.), Ganymede, Cambridge Univ. Press, p. 59-74, 2025. [6] Kirchoff, M. R. et al., in: Volwerk, M. et al. (Eds.), Ganymede, Cambridge Univ. Press, p. 104-125, 2025. [7]. Nesvorný, D. et al., Planet. Sci. J. 4:139, 2023. [8] Wagner, R. J. et al., EPSC-DPS abstr. EPSC-DPS2025-2086, 2025. [9] Zahnle, K. et al., Icarus 163, 263-289, 2003.