A Micro-to-Macro Structural Approach Using Terrestrial Analogs to Constrain Crustal Mechanics in Europa’s Strike-Slip Zones Article Swipe

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Costanza Rossi , Hatsuki Yamauchi , Christine McCarthy , David J. Prior , Alice Lucchetti , M. Pajola , Luca Penasa , Filippo Tusberti · YOU? · · 2025 · Open Access · · DOI: https://doi.org/10.5194/epsc-dps2025-1530

Introduction:Multiscale analysis is a powerful tool for investigating the surfaces and interiors of Solar System bodies. It is particularly valuable for studying the icy satellites of the outer planets, which are remote targets whose exploration relies heavily on remote sensing and therefore greatly benefit from complementary analog studies. These satellites are key objectives of current planetary missions: ESA’s JUICE and NASA’s Europa Clipper are both en route to the Jovian system, aiming to investigate their geological activity and potential habitability.Most icy satellites are thought to possess an outer ice shell overlying a subsurface liquid water ocean, sustained primarily by tidal heating, e.g. [1]. The ocean activity caused by tides drives deformation of the overlying brittle ice crust, leading to the formation of extensive networks of kilometer-scale fractures and strike-slip faults, particularly on Europa, Ganymede, and Enceladus [2][3]. Compressional structures are relatively rare [4]. These tectonic features are critically important, as they may serve as conduits between the surface and the internal ocean. Therefore, understanding both brittle and ductile deformation structures is essential for revealing the processes at work within the icy crust and the insights they offer.In this study, we explore how terrestrial glacial environments can serve as analogs for icy satellite tectonics, with a focus on strike-slip fault zones. We present structural data from the Priestley Glacier, Antarctica, where the eastern margin exhibits brittle structures caused by left-lateral strike-slip kinematics. [5] collected an ice core sample from this area, showing a well-developed Crystallographic Preferred Orientation (CPO) of the ice crystals throughout the 58-meter-deep core. This fabric correlates with larger-scale deformation patterns of the sinistral shear. These findings were used as a reference to interpret strike-slip zones on Europa that show macrostructural similarities to the Priestley margin.The aim of this study is to constrain the mechanical behavior and internal structure of strike-slip fault zones on icy satellites, particularly Europa, through multiscale structural analysis of terrestrial glacial analogs. This approach contributes to advancing our understanding of crustal deformation in icy satellites.Data and Methods:We conducted a multiscale analysis by mapping macro-scale features (e.g., fractures and faults) in satellite images of the Priestley Glacier, and micro-scale structures (e.g., subgrain boundaries and slip bands) in microscope images of a sample obtained from the Priestley Glacier ice core at a depth of ~52 m [5]. A strong correlation was found between surface structures and microstructural fabric, indicating the scalability of the deformation system. Both the microstructures and the CPO are consistent with synthetic strike-slip and compressional structures recognized at larger scale, suggesting that a transpressional component is active at the glacier margin depth, which is something not clearly observed at the macro scale.The strong CPO and the existence of subgrain boundaries suggest that deformation at approximately 50 m depth is governed by a ductile regime. These microstructures indicate that internal zones of weakness may exist even in the absence of brittle fracturing. Therefore, this may suggest that the oriented fabric and its associated defects could act as pathways for fluid migration within the ductile ice layer.Europa Application:We applied these insights to Europa, where long bands and ridges, interpreted as strike-slip zones, exhibit comparable structures and morphologies to those observed at Priestley Glacier. Four strike-slip zones were identified as analogs, where regional-scale structural mapping was performed. This comparison allowed us to estimate the depth of the brittle–ductile transition beneath these shear zones on Europa and to infer internal viscosity. Using available values for naturally deformed ice, we scaled viscosity estimates to Europa’s subsurface, providing new constraints on the mechanical behavior of its icy crust.Discussion and Conclusions:Our results help define the location of rheological variations within Europa’s icy crust, particularly across strike-slip zones. On the Priestley Glacier, the occurrence of an ice fabric consistent with transpression suggests that compressional deformation may primarily occur in the deeper, ductile layers rather than in the upper brittle portion. This leads us to make analog inferences for Europa's crust on shear zones. A three-dimensional tectonic model was developed, integrating both micro- and macro-scale data, to illustrate the structural and rheological architecture of Europa’s icy crust.This approach improves our understanding of icy satellite evolution, from surface features observed via remote sensing to deep crustal deformation. The findings support future scientific planning for targeted high-resolution imaging by the cameras of JUICE (JANUS [6]) and Europa Clipper ( EIS [7]) missions. Acknowledgements: This work is part of the DISCOVERIES project funded by INAF Mini Grants RSN3. The activity has been realized under the ASI-INAF contract 2023-6-HH.0.References: [1] Ojakangas and Stevenson, 1989, Icarus, 81(2), 220-241; [2] Pappalardo et al., 1998, Icarus, 135(1), 276-302; [3] Nimmo et al., 2002, JGR: Planets, 107(E4), 5-1; [4] Kattenhorn and Prockter, 2014, Nat. Geoscience, 7(10), 762-767; [5] Thomas et al., 2021, Front. Earth Sci. 9:702213; [6] Palumbo et al., 2025, Space Science Reviews, 221(3), 32; [7] Turtle et al., 2024, Space Science Reviews, 220(8), 1-68.

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https://doi.org/10.5194/epsc-dps2025-1530

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https://doi.org/10.5194/epsc-dps2025-1530

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A Micro-to-Macro Structural Approach Using Terrestrial Analogs to Constrain Crustal Mechanics in Europa’s Strike-Slip Zones

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2025

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2025-07-09

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Costanza Rossi, Hatsuki Yamauchi, Christine McCarthy, David J. Prior, Alice Lucchetti, M. Pajola, Luca Penasa, Filippo Tusberti

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https://doi.org/10.5194/epsc-dps2025-1530

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