{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"341cf8db639b788083dda34941cdd1d6cc367d3f09b6eaa0790863337ff50374","created":"2026-10-03T07:18:03Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"f250e1b7cc63302be68d4456bdf84a1a6c13038ae886e6702a89effc03cb1aee","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"earth.ocean-worlds.europa-shell-exchange","kind":"well-posed","literature_status":"open","n":"1","parents":[],"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.","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 material?","topic_ref":"fce9705aed3acbaf66c27413ec3badd10cbd89376e3f1b6fc466396c06130caa"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"53f6b11a9e034d6f685d5cdb39b4e16266ccffa1e747e1e9244d3f918d6d92a2","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"d10c9edf78f5afad811bf4d12396e59a48e63d69a05e8835210feadc3dd080b2","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"B2k4u0gJahwJS5vqRMwgg6RlvoMFtowyBIPWgScunO7IqRfk3kWBrngVUk1Tl7vQ0ezWmb1_ljmekkTpymYlCg"},"schema":"pubphys.envelope/1"},"record_hash":"53f6b11a9e034d6f685d5cdb39b4e16266ccffa1e747e1e9244d3f918d6d92a2","leaf_index":1343}