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Whether surface material can reach the ocean, carrying chemical energy sources for possible life, depends on that thickness and on how the ice moves.","posed_since":"","precise":"Determine the total thickness of Europa's ice shell and the thickness of its conductive lid versus convecting layer, and whether material is transported between surface and ocean by convection, subduction-like processes or melt-through, on timescales below the surface age of about 60 Myr. An answer is a thickness with uncertainty and a demonstrated exchange pathway and rate.","problem_ref":null,"references":"","settled_by":"Ice-penetrating radar, gravity and magnetic induction data from Europa Clipper combined with geodynamic models constrained by surface geology.","status_note":"Juno microwave radiometer data (Levin et al. 2025, Nature Astronomy) indicate a thermally conductive outer shell of 29 +/- 10 km, with near-surface cracks too shallow to carry nutrients to the ocean.","title":"How thick is Europa's ice shell and does it exchange 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