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Title: Why does Mercury have such an outsized iron core?
Plain: About 70 percent of Mercury's mass is in its metal core, far more than for Earth or Mars. It may have lost its rocky outer layers in a giant impact, or formed from material enriched in iron near the Sun.
Precise: Explain Mercury's metal mass fraction (about 0.7) by mantle stripping in one or more hit-and-run or giant impacts, by chemical or magnetic sorting of iron-bearing solids in the inner disk, or by evaporation, consistent with MESSENGER's detection of a surface high in volatile elements (high K/Th, S, Na). An answer is a scenario matching bulk composition and volatile inventory.
Settled by: BepiColombo measurements of Mercury's interior and surface composition combined with formation models that predict both the metal fraction and the volatile abundances.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: open
Status note: BepiColombo is scheduled to enter Mercury orbit in late November 2026, with interior and surface-composition measurements to follow.
Posed since: (empty)