{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"aa1dd021a2e9d3bed9e2e03fce354a3a0ec1e20d9f7e37b87b3243e4c94c815c","created":"2026-10-03T07:18:03Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"d8ca1a78885b8e000de47829ab73efb66ad951a25d95bb25ba45c98c7036db26","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"earth.inner-core.light-elements","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Earth's liquid core is about 10 percent less dense than pure iron-nickel would be at core pressure, so lighter elements must be dissolved in it. Which ones (silicon, oxygen, sulfur, carbon or hydrogen) and how much of each is unknown.","posed_since":"1952","precise":"The outer core is roughly 10 percent less dense than Fe-Ni at the same P and T, the inner core a few percent, and the density jump at the inner-core boundary is about $0.5\\ \\text{to}\\ 0.9\\ \\mathrm{g}/\\mathrm{cm}^{3}$ depending on the normal-mode analysis. Determine the concentrations of Si, O, S, C and H in outer and inner core that reproduce density, compressional velocity and the boundary density jump, with solid-liquid partitioning from experiment or ab initio calculation and consistency with core-formation conditions. An answer is a composition with uncertainty of about 1 weight percent per element.","problem_ref":null,"references":"","settled_by":"Static and shock measurements of density and sound speed of Fe alloys at core conditions combined with ab initio solid-liquid partitioning and normal-mode constraints on the inner-core boundary.","status_note":"","title":"Which light elements make Earth's core less dense than 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