{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"92887766abd4eddf733669cfd633e2ae0e9030f3fbbdafe8363d82feb752b714","created":"2026-10-03T07:18:03Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["51545aca12e72e5514ed3f46e2e3ef4b1719bf94439437e1aadafac010f0d214","5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"7e1ecfa5f2b70d8267413e990acc87d8422df7ddfaf474bb0eb97927c5b05d1d","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"earth.mantle-structure.llsvp-density","kind":"well-posed","literature_status":"contested","n":"1","parents":[{"note":"","parent_revision":"51545aca12e72e5514ed3f46e2e3ef4b1719bf94439437e1aadafac010f0d214","relation":"special_case"}],"plain":"If the two big regions are denser than normal mantle they are chemically different and long-lived; if lighter they are probably just hot. Different methods give opposite answers.","posed_since":"","precise":"Determine the sign and magnitude of the density anomaly $\\delta \\rho/\\rho$ in the lowermost 300 to 500 km of the LLSVPs. Normal-mode and Stoneley-mode inversions have favored lighter material while body-tide tomography (Lau and coauthors, Nature 2017) favored denser material. An answer is $\\delta \\rho/\\rho$ with uncertainty below about 0.3 percent from mutually consistent methods.","problem_ref":null,"references":"","settled_by":"Combined normal-mode, body-tide and satellite-gravity inversions with shared parametrization and resolution tests.","status_note":"A 2026 satellite-gravity analysis (arXiv:2606.09296) adds new constraints; methods still disagree.","title":"Are the deep mantle slow regions denser or lighter than their surroundings?","topic_ref":"704a212d9f3a93ea0fe758e2d498cdc938219156d755cccd033c2d677e4d8b4a"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"1d3f886d2b2d4a25428175d92ba982db6a1fe43abe89b307b3c2c6f5e6f64aae","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"579f546f37b04e33424cb1747a41625fbbded8f39edde53d22a4ffcb2aa0e179","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"0A0ILdvk4uoO7SVxqVVE2LRkKvWtOTKuCDJvRiZgxgNLY8zpbtFajKHN1tVqVn4EyIa_v3mODT6aUYcLdfn2DA"},"schema":"pubphys.envelope/1"},"record_hash":"1d3f886d2b2d4a25428175d92ba982db6a1fe43abe89b307b3c2c6f5e6f64aae","leaf_index":1336}