%0 Journal Article %1 Lodders1997a %A Lodders, K. %A Fegley, B. %D 1997 %J Icarus %K ACCRETION ALTERATION; AQUEOUS CONTINENTAL-CRUST; CORE Chemical-COMPOSITION; EARLY EARTH; EVOLUTION; FORMATION; HISTORY; METEORITE PARTITION-COEFFICIENTS; PLANETS; SILICATE TERRESTRIAL %N 2 %P 373--394 %T An oxygen isotope model for the composition of Mars %V 126 %X We derive the bulk chemical composition, physical properties, and trace element abundances of Mars from two assumptions: (1) Mars is the parent body for the Shergottite-Nakhlite-Chassignite (SNC) meteorites, and (2) the oxygen isotopic composition of Mars was determined by the oxygen isotopic compositions of the different types of nebular material that accreted to form Mars. We use oxygen isotopes to constrain planetary bulk compositions because oxygen is generally the most abundant element in rock, and is either the first or second (after iron) most abundant element in any terrestrial planet, the Moon, other rocky satellites, and the asteroids. The oxygen isotopic composition of Mars, calculated from oxygen isotopic analyses of the SNC meteorites, corresponds to the accretion of about 85% H-, 11% CV-, and 4% CI-chondritic material. (Unless noted otherwise, mass percentages are used in this paper.) The bulk composition of Mars follows from mass balance calculations using mean compositions for these chondrite groups. We predict that silicates (mantle + crust) comprise about 80% of Mars. The composition of the silicate fraction represents the composition of the primordial martian mantle prior to crustal formation. The FeO content of the mantle is 17.2%. A metal-sulfide core, containing about 10.6% S, makes up the remaining 20% of the planet. Our bulk composition is similar to those from other models. We calculate the abundances of siderophile (''metal-loving'') and chalcophile (''sulfide-loving'') elements in the martian mantle from the bulk composition using (metal-sulfide)/silicate partition coefficients. Our results generally agree with predictions of the SNC meteorite model of Wanke and Dreibus for the composition of Mars. However, we predict higher abundances for the alkalis and halogens than those derived from SNC meteorite models for Mars. The apparent discrepancy indicates that the alkalis and halogens were lost from the martian mantle by hydrothermal leaching and/or vaporization during accretion. Geochemical arguments suggest that vaporization was only a minor loss process for these elements. On the other hand, aqueous transport of the alkalis and halogens to the surface is supported by the terrestrial geochemistry of these elements and the high K, Rb, Cl, and Br abundances found by the Viking XRF and Phobos gamma ray experiments on the surface of Mars. (C) 1997 Academic Press.

@article{Lodders1997a, abstract = {We derive the bulk chemical composition, physical properties, and trace element abundances of Mars from two assumptions: (1) Mars is the parent body for the Shergottite-Nakhlite-Chassignite (SNC) meteorites, and (2) the oxygen isotopic composition of Mars was determined by the oxygen isotopic compositions of the different types of nebular material that accreted to form Mars. We use oxygen isotopes to constrain planetary bulk compositions because oxygen is generally the most abundant element in rock, and is either the first or second (after iron) most abundant element in any terrestrial planet, the Moon, other rocky satellites, and the asteroids. The oxygen isotopic composition of Mars, calculated from oxygen isotopic analyses of the SNC meteorites, corresponds to the accretion of about 85% H-, 11% CV-, and 4% CI-chondritic material. (Unless noted otherwise, mass percentages are used in this paper.) The bulk composition of Mars follows from mass balance calculations using mean compositions for these chondrite groups. We predict that silicates (mantle + crust) comprise about 80% of Mars. The composition of the silicate fraction represents the composition of the primordial martian mantle prior to crustal formation. The FeO content of the mantle is 17.2%. A metal-sulfide core, containing about 10.6% S, makes up the remaining 20% of the planet. Our bulk composition is similar to those from other models. We calculate the abundances of siderophile (''metal-loving'') and chalcophile (''sulfide-loving'') elements in the martian mantle from the bulk composition using (metal-sulfide)/silicate partition coefficients. Our results generally agree with predictions of the SNC meteorite model of Wanke and Dreibus for the composition of Mars. However, we predict higher abundances for the alkalis and halogens than those derived from SNC meteorite models for Mars. The apparent discrepancy indicates that the alkalis and halogens were lost from the martian mantle by hydrothermal leaching and/or vaporization during accretion. Geochemical arguments suggest that vaporization was only a minor loss process for these elements. On the other hand, aqueous transport of the alkalis and halogens to the surface is supported by the terrestrial geochemistry of these elements and the high K, Rb, Cl, and Br abundances found by the Viking XRF and Phobos gamma ray experiments on the surface of Mars. (C) 1997 Academic Press.}, added-at = {2009-11-03T20:21:25.000+0100}, author = {Lodders, K. and Fegley, B.}, biburl = {https://www.bibsonomy.org/bibtex/272d5b2bcf051c832b3a7517c3be6a04f/svance}, interhash = {034493338b0294f3e7ceb0010001ba04}, intrahash = {72d5b2bcf051c832b3a7517c3be6a04f}, journal = {Icarus}, keywords = {ACCRETION ALTERATION; AQUEOUS CONTINENTAL-CRUST; CORE Chemical-COMPOSITION; EARLY EARTH; EVOLUTION; FORMATION; HISTORY; METEORITE PARTITION-COEFFICIENTS; PLANETS; SILICATE TERRESTRIAL}, number = 2, owner = {svance}, pages = {373--394}, timestamp = {2009-11-03T20:21:58.000+0100}, title = {An oxygen isotope model for the composition of Mars}, volume = 126, year = 1997 }