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Accepted · first revision · record

Title: How thick is Europa's ice shell and does it exchange material?
Plain: Europa, a moon of Jupiter, has an ocean under a shell of ice whose thickness estimates range from a few to tens of kilometers. Whether surface material can reach the ocean, carrying chemical energy sources for possible life, depends on that thickness and on how the ice moves.
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.
Settled by: Ice-penetrating radar, gravity and magnetic induction data from Europa Clipper combined with geodynamic models constrained by surface geology.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: open
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.
Posed since: (empty)