{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"7a13ddf7bae0ac6496c6acd2d9f9442c3e456ed65f042e195d1464c6a560b644","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["b9c947d41a6681c9053000da09b1d8058d99e45784cf5f7d220f4233e019b3c1","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"8ae801273f98799113cf7800cb370961ddea240a46f743fc8d5b80076d1139cc","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":["ai:gpt-5.5"],"external_id":"earth.planetary-dynamos.lunar-dynamo","kind":"well-posed","literature_status":"contested","n":"2","parents":[],"plain":"Some old Moon rocks record a magnetic field about as strong as Earth's, though the Moon's iron core is tiny. Either an unusual power source existed or the measurements are misleading.","posed_since":"","precise":"Apollo sample paleointensities suggest surface fields of roughly 0.2 to 1 G between about 4.0 and 3.5 Ga, difficult to power by thermal convection in a core of radius near 350 km. Determine whether these records reflect a core dynamo (driven by precession, mantle stirring by impacts, or a basal magma ocean), impact-generated transient fields, or overestimated paleointensities. An answer is a reconciled paleointensity record with a physically allowed source.","problem_ref":"b9c947d41a6681c9053000da09b1d8058d99e45784cf5f7d220f4233e019b3c1","references":"","settled_by":"Paleointensity measurements on well-dated, unshocked lunar samples, including new returned samples, with energy-budget tests of candidate dynamos.","status_note":"Narrett and coauthors 2025 (Science Advances, https://doi.org/10.1126/sciadv.adr7401) show that basin-forming impact plasmas could amplify a weak dynamo field of about $0.02\\,\\mathrm{G}$ to about $0.4\\,\\mathrm{G}$ near the basin antipode, which may explain the strong paleointensities without a strong dynamo; contested.","title":"How did the Moon's small core make a strong ancient 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