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The geomorphological and composition analysis of Melkart crater on the surface of Ganymede

Presentation #504.06 in the session Galilean Satellites: Scratching the Surface (Oral Presentation)

Published onOct 23, 2023
The geomorphological and composition analysis of Melkart crater on the surface of Ganymede

In this work, we performed a multidisciplinary analysis of the ~103 km-diameter Melkart impact crater on the surface of Ganymede, which is located at the boundary between the light and dark terrain [1]. We made use of both Galileo SSI and NIMS datasets to investigate any possible correlation between its geology and composition. A high-resolution geological map allows us to identify the main geological units characterizing both light and dark terrains on which Melkart stands. An asymmetry of the ejecta blanket and the pit-dome off-centered location has been revealed, which support an impact direction from SSW to NNE. Fractures dome suggests that the crater dome underwent strike-slip deformation with right-lateral kinematics. The crater strain analysis performed through the use of the DTM supports that Melkart is a low strain end member with subtle deformation, which has been formed in an area of gradual transition between light and dark terrains. This is in agreement with an impact that occurred during the late stage of the light terrain formation (between 4 and 2 Gyr), suggesting that Melkart age is closer to 2 Gyr. By making use of the NIMS dataset, we performed a compositional analysis deriving the water ice band depths and the crystallinity map. The results obtained 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. Starting from the presented work, higher resolution data will be pivotal to provide an even deeper analysis of Melkart crater and icy surface features in general. This will be possible thanks to the ESA JUICE mission [2], whose first objective will be the study of Ganymede by high resolution imagery and spectroscopy [3, 4].

References:

[1] Lucchetti, A., et al., (2023). Icarus, 401, 115613; [2] Grasset, O., et al., (2013). PSS, 78, 1-21; [3] Langevin, Y., (2017), EPSC, v. 11; [4] Palumbo, P., et al., (2014), LPSC Vol. 45, p. 2094.

Acknowledgements

This work has been developed under the ASI-INAF agreement n. 2023-6-HH.0. We gratefully acknowledge funding from National Institute of Astrophysics through the INAF - Mini Grant RSN3 RIFTS project (d.d. 5/2022).

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