{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"0de1a48e37b94a3711836a4ae64a2fb87097ce8cff806a1735da9a9e5b84fce7","created":"2026-10-03T07:18:03Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"3e7dc75786649a42098ef6c149855585246ce73b697aa605d09496bee9f9c524","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"earth.planetary-dynamos.ganymede-dynamo","kind":"phenomenon","literature_status":"open","n":"1","parents":[],"plain":"Jupiter's moon Ganymede is the only moon known to make its own magnetic field. Models of how such a small body cools suggest its core should have stopped stirring long ago.","posed_since":"1996","precise":"Galileo detected an intrinsic dipole with surface equatorial strength near 7e-3 G. Identify the power source that keeps Ganymede's Fe-FeS core convecting after 4.5 Gyr: iron snow, FeS crystallization, compositional convection, or heat from past tidal heating during resonance passage. An answer is a thermal-chemical evolution model producing a present dynamo of the observed strength.","problem_ref":null,"references":"","settled_by":"JUICE orbital measurements of field harmonics, induction response and gravity (Love numbers) constraining core size and state.","status_note":"JUICE is planned to arrive at Jupiter in 2031 and orbit Ganymede from 2034.","title":"How does Ganymede sustain a core dynamo today?","topic_ref":"d630b91b3d151b4fd563599f0c63c42ed19209d89bcb67e4ebbd2cdaddd50144"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"40886804113da406a1da2ae18b5c2a4f1ab427de5fc3a9aac1ff3178ad459275","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"6ebcf4cf7182c6975707f4666efd945f16021a69a10d75f8fb5e1754d7339f54","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"3EdWWZ85p34D0MpKNTr3wYDcyNqs2hCIin4AAC6wFr-3XYrz8KJwud30C-gOXW97LL37-nBvQ6QvQBwtYBl-Aw"},"schema":"pubphys.envelope/1"},"record_hash":"40886804113da406a1da2ae18b5c2a4f1ab427de5fc3a9aac1ff3178ad459275","leaf_index":1353}