The early differentiation history of Mars from 182W-142Nd isotope systematics in the SNC meteorites

Foley, C. N.; Wadhwa, M.; Borg, L. E.; Janney, P. E.; Hines, R.; Grove, T. L.

doi:10.1016/j.gca.2005.05.009

Cited by 173 publications

(192 citation statements)

References 48 publications

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“…Tungsten was separated from matrix and isobar elements using ion exchange chromatography, and its isotopic composition was analyzed by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS; for details see Foley et al 2005;Qin et al 2007). …”

Section: Methodsmentioning

confidence: 99%

“…Subsequent melting induced differentiation (i.e., segregation of metal and silicate), the timing of which can be determined by measuring the abundance of 182 W, a decay product of short-lived 182 Hf (t 1 = 2 ¼ 8:9 AE 0:09 Myr; Vockenhuber et al 2004). Using this extinct radioactivity, it is possible to establish the accretion timescales of Earth and Mars, date the Moonforming impact, and date magmatic differentiation events in meteorite parent bodies (e.g., Quitté et al 2000;Yin et al 2002;Kleine et al 2002;Schoenberg et al 2002;Lee et al 2002;Foley et al 2005;Markowski et al 2006a).…”

Section: Introductionmentioning

confidence: 99%

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Tungsten Nuclear Anomalies in Planetesimal Cores

Qin

Dauphas

Wadhwa

et al. 2008

ApJ

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Use of the extinct 182 Hf-182 W chronometer to constrain the timing of planetary accretion and differentiation rests on the assumption that the solar nebula had homogeneous tungsten isotopic composition. Here, we report deficiencies of $0.1 part in 10,000 in the abundance of 184 W in group IVB iron meteorites relative to the silicate Earth. These are most likely due to incomplete mixing at the planetesimal scale (2Y4 km radius bodies) of the products of slow (s-) and rapid (r-) neutron-capture nucleosynthesis in the solar nebula. The correction that must be applied to the 182 Hf-182 W model age of core formation in IVB irons due to the presence of these nuclear anomalies is $0.5 Myr.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tungsten Nuclear Anomalies in Planetesimal Cores

Qin

Dauphas

Wadhwa

et al. 2008

ApJ

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“…Chambers 2004). Using planet-wide metalsilicate segregation and core formation as a tool to monitor the rate of late-stage accretion processes, the stage II (Vesta to Mars) and stage III (Earth-Moon system) formation timescales are now well established (e.g., Lugmair & Shukolyukov 1998;Quitté et al 2000;Yin et al 2002;Foley et al 2005;Jacobsen 2005; Kleine et al 2005). Stage I is the least understood among the three stages because there are very few observational constraints and the physics of grain growth in the solar nebula from micron-sized particles to kilometer-sized bodies is not well understood (Youdin & Shu 2002).…”

Section: Introductionmentioning

confidence: 99%

Dating the First Stage of Planet Formation

Moynier

Yin

Jacobsen

2007

ApJ

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“…The segregation of the Martian core fractionated the highly lithophile Hf from the moderately siderophile W. If this metal-silicate segregation happened during the life time of the short lived isotope 182 Hf, then the Martian mantle should have an excess in 182 W and analyses of SNC meteorites confirm that this signal is preserved in Martian meteorites (Lee and Halliday 1997;Kleine et al 2004b;Foley et al 2005). Using the W isotope composition of Martian samples to estimate the timing of core formation requires knowledge of the Hf/W and 182 W/ 184 W ratios of bulk Mars and the bulk silicate portion of Mars.…”

Section: Hf-w Age Of Core Formation and The Accretion History Of Marsmentioning

confidence: 99%

Core Formation and Mantle Differentiation on Mars

Mezger¹,

Debaille²,

Kleine³

2012

Quantifying the Martian Geochemical Reservoirs

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Geochemical investigation of Martian meteorites (SNC meteorites) yields important constraints on the chemical and geodynamical evolution of Mars. These samples may not be representative of the whole of Mars; however, they provide constraints on the early differentiation processes on Mars. The bulk composition of Martian samples implies the presence of a metallic core that formed concurrently as the planet accreted. The strong depletion of highly siderophile elements in the Martian mantle is only possible if Mars had a large scale magma ocean early in its history allowing efficient separation of a metallic melt from molten silicate. The solidification of the magma ocean created chemical heterogeneities whose ancient origin is manifested in the heterogeneous 142 Nd and 182 W abundances observed in different meteorite groups derived from Mars. The isotope anomalies measured in SNC meteorites imply major chemical fractionation within the Martian mantle during the life time of the short-lived isotopes 146 Sm and 182 Hf. The Hf-W data are consistent with very rapid accretion of Mars within a few million years or, alternatively, a more protracted accretion history involving several large impacts and incomplete metal-silicate equilibration during core formation. In contrast to Earth early-formed chemical heterogeneities are still preserved on Mars, albeit slightly modified by mixing processes. The preservation of such ancient chemical differences is only possible if Mars did not undergo efficient whole mantle convection or vigorous plate tectonic style processes after the first few tens of millions of years of its history. K. Mezger ( )

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The early differentiation history of Mars from 182W-142Nd isotope systematics in the SNC meteorites

Cited by 173 publications

References 48 publications

Tungsten Nuclear Anomalies in Planetesimal Cores

Tungsten Nuclear Anomalies in Planetesimal Cores

Dating the First Stage of Planet Formation

Core Formation and Mantle Differentiation on Mars

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