{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"169c9b288db3325ec481fa07d49fb4b9c80f579d74c686becffd744759954fdc","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["4c25e29e34f66825aeac161867c3d4f6dd377cf6326377be83cef182939c8a6d","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"7c3582473cd0310dd5f217b8c41a7053f6dec1d628b88d40883017ffda19e217","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"earth.venus-divergence.no-dynamo","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"Venus has an iron core roughly as large as Earth's but no magnetic field of its own. Either its core does not churn today or something else stops a dynamo (a self-sustaining magnetic generator made by flowing liquid metal).","posed_since":"","precise":"Spacecraft limits put any intrinsic Venus dipole moment below roughly $10^{-5}$ of Earth's (approximate, from Pioneer Venus era data). Determine why the Venus core sustains no dynamo: low core-mantle heat flow under a stagnant lid with no inner-core growth, a fully liquid or fully solid core, or a compositionally stratified core formed without a late giant impact (Jacobson and coauthors, EPSL 2017, https://doi.org/10.1016/j.epsl.2017.06.023). An answer is a core state (radius, solid fraction, stratification) and core heat flow consistent with the measured tidal Love number $k_2$, the moment of inertia and a thermal history, including whether a dynamo operated in the past.","problem_ref":"4c25e29e34f66825aeac161867c3d4f6dd377cf6326377be83cef182939c8a6d","references":"","settled_by":"Orbiter tracking that measures the Venus $k_{2}$ and moment of inertia precisely, combined with a search for remanent magnetization in old crust.","status_note":"","title":"Why does Venus have no internally generated magnetic field?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"5d89b8fa31d5cf27b1bb6e9cf9fe5eb6775441c49028c8129cf0d139f3aca323","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"4c8a18566c6d63d04eb1f3d118f724f12cad32ad563c33e92ef6dec3224bf76a","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"MicMtuEUp7JDfhQeIwYliCmprtRHVeHWzirNXhDC66WZmjMQ0Q3rWRDQK_vhOb9EfGmfH53YdFjsShhJFYfXDw"},"schema":"pubphys.envelope/1"},"record_hash":"5d89b8fa31d5cf27b1bb6e9cf9fe5eb6775441c49028c8129cf0d139f3aca323","leaf_index":3238}