Review

Elemental Composition of the Martian Crust

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Science  08 May 2009:
Vol. 324, Issue 5928, pp. 736-739
DOI: 10.1126/science.1165871

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Mars Matters

Several decades of exploration by orbiting and in situ spacecraft, together with analysis of martian meteorites, have resulted in a wealth of data on the chemical composition of Mars' crust. McSween et al. (p. 736) review these data, which help infer the planet's geological history, discrediting previous ideas suggesting Mars had a wet mantle—similar to that of Earth—and cautioning that martian meteorites are not representative of the planet's crust.

Abstract

The composition of Mars’ crust records the planet’s integrated geologic history and provides clues to its differentiation. Spacecraft and meteorite data now provide a global view of the chemistry of the igneous crust that can be used to assess this history. Surface rocks on Mars are dominantly tholeiitic basalts formed by extensive partial melting and are not highly weathered. Siliceous or calc-alkaline rocks produced by melting and/or fractional crystallization of hydrated, recycled mantle sources, and silica-poor rocks produced by limited melting of alkali-rich mantle sources, are uncommon or absent. Spacecraft data suggest that martian meteorites are not representative of older, more voluminous crust and prompt questions about their use in defining diagnostic geochemical characteristics and in constraining mantle compositional models for Mars.

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