Unique physical and chemical characteristics of Mercury have been revealed by measurements from NASA's MESSENGER spacecraft. The closest planet to our Sun is made up of a large metallic core that is partially liquid, a thin mantle thought to be formed by solidification of a silicate magma ocean, and a relatively thick secondary crust produced by partial melting of the mantle followed by volcanic eruptions. However, the origin of the large metal/silicate ratio of the bulk planet and the conditions of accretion remain elusive. Metal enrichment may originate from primordial processes in the solar nebula or from a giant impact that stripped most of the silicate portion of a larger planet leaving Mercury as we know it today.

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