Geochemical evolution of Mars

Mars is more volatile-rich than Earth, reflecting a higher proportion of accreted volatilebearing planetesimals. It is also more highly oxidized than Earth, so that twice as much of its iron has remained as Fe2+ in the mantle rather than in the metallic core. Wanke and Dreibus (1988) suggested that oxidation occurred during accretion, as water in accreted planetesimals reacted with iron metal. 

Both short-lived (182Hf-182W, 146Sm-142Nd) and long-lived (87Rb-87Sr, 

The crust of Mars is basaltic, with only small amounts of other rock compositions. Most volcanism was ancient but some eruptions, especially in Tharsis and Elysium, may extend to the present day. 

Early on, water existed at least periodically on the Martian surface. The formation of clay minerals in the Noachian and precipitation of sulfates and chlorides in the Hesperian were consequences of this water. Some fraction of the water evaporated and was lost to space, as indicated by the high D/H ratios in SNCs. Other water was apparently sequestered at the poles or underground as permafrost. The surface of Mars is effectively dry now, and chemical weathering of crustal rocks is minimal. 

The Moon and Mars have very different compositions and have had very different geologic histories. However, the geochemical techniques applied to both bodies are similar, and the results illustrate the power of chemical data in planetary exploration. Combinations of 

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The following publications provide excellent summaries of the geologic and geochemical evolution of Mars ... 

In a recent paper (Marion et al. 2003a), we quantified a conceptual model for the surficial aqueous geochemical evolution of Mars. This model rests... 

Table 5.3. Martian and comparative solution compositions in the geochemical evolution of Mars. Reprinted from Marion et al. (2003a)... 

Schaefer MW (1990) Geochemical evolution of the Northern Plains of Mars Early hydrosphere, carbonate development, and present morphology. J Geophys Res 95 14,291-14,300... 

Wright I, Grady MM, PUlinger CT (1990) The evolution of atmospheric C02 on Mars the perspective from carbon isotope measurements. 1 Geophys Res 95 14789-14794 Wunder B Meixner A, Romer R, Wirth R, Heinrich W (2005) The geochemical cycle of boron constraints from boron isotope partitioning experiments between mica and fluid. Lithos 84 ... 

Nier AO, Hayden JL (1971) A miniature Mattauch-Herzog mass spectrometer for the investigation of planetary atmospheres. Inti J Mass Spectrom Ion Phys 6 339-346 Nier AO, McElroy MB (1977) Composition and stmctuie of Mars upper atmosphere results from the neutral mass spectrometers on Viking 1 and 2. J Geophys Res 82 4341-4349 Ott U (2002) Noble gases in meteorites- trapped components. Rev Mineral Geochem 47 71-100 Ozima M, Kudo K (1972) Excess argon in submarine basalts and an earth-atmosphere evolution model. Nature Phys Sci 239 23-24... 

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