The role of carbon and oxygen in cosmic gases: some applications to the chemistry and mineralogy of enstatite chondrites

Larimer, J. W.; Bartholomay, Mary

doi:10.1016/0016-7037(79)90140-6

Cited by 185 publications

(106 citation statements)

References 31 publications

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“…Two principal models to explain reduction of nebular gas have been proposed: 1) addition of C-rich dust (Larimer and Bartholomay 1979); and 2) removal of oxygen (Baedecker and Wasson 1975). Local fluctuation of these components could explain variation of oxygen fugacity in the reservoir.…”

Section: Reservoir Of Feo-rich Pyroxene Formationmentioning

confidence: 99%

FeO‐rich silicates in the Sahara 97159 (EH3) enstatite chondrite: Mineralogy, oxygen isotopic compositions, and origin

Kimura

Hiyagon

Lin

et al. 2003

Meteorit & Planetary Scien

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Section: Reservoir Of Feo-rich Pyroxene Formationmentioning

confidence: 99%

FeO‐rich silicates in the Sahara 97159 (EH3) enstatite chondrite: Mineralogy, oxygen isotopic compositions, and origin

Kimura

Hiyagon

Lin

et al. 2003

Meteorit & Planetary Scien

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“…An increase in the C/O ratio has been proposed as the most likely way to create minerals such as CaS and MgS in the solar nebula (e.g., Larimer and Bartholomay, 1979;Lodders and Fegley, 1993). That water-vapor depletion in a nebular gas may have been important for enstatite chondrites is suggested by the work of Baedecker and Wasson (1975), who calculated that the Si content observed in E4 metal could be obtained at a pressure of 10-4 atm if the H20/H2 ratio of the gas was 5x lower than solar.…”

Section: Water Depletionmentioning

confidence: 99%

“…Several models to account for the origin of the enstatite chondrites have been proposed, including: ( I ) condensation with slow nucleation kinetics (Blander, 1971); (2) condensation at high pressures (>I bar) (Herndon and Suess, 1976;Sears, 1980); (3) formation in a region of the nebula with low H20/H2 ratio (Baedecker and Wasson, 1975) or high C/O ratio (Larimer and Bartholomay, 1979;Lodders andFegley, 1993, 1997); (4) increasing the amount of a "tar" component in the nebula (Wood and Hashimoto, 1993); and (5) condensation with partial isolation of solids (Petaev and Wood, 1998). None of these models have successfully replicated the observed modal mineralogy and bulk compositions of type 3 enstatite chondrites.…”

Section: Introductionmentioning

confidence: 99%

A multi‐step model for the origin of E3 (enstatite) chondrites

Hutson¹,

Ruzicka²

2000

Meteorit & Planetary Scien

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Abstract-It appears that the mineralogy and chemical properties of type 3 enstatite chondrites could have been established by fractionation processes (removal of a refractory component, and depletion of water) in the solar nebula, and by equilibration with nebular gas at low-to-intermediate temperatures (approximately 700-950 K). We describe a model for the origin of type 3 enstatite chondrites that for the first time can simultaneously account for the mineral abundances, bulk-chemistry, and phase compositions of these chondrites by the operation of plausible processes in the solar nebula. This model, which assumes a representative nebular gas pressure of 10-5 bar, entails three steps: (1) initial removal of 56% of the equilibrium condensed phases in a system of solar composition at 1270 K; (2) an average loss of 80-85% water vapor in the remaining gas; and (3) two different closure temperatures for the condensed phases. The first step involves a "refractory element fractionation'' and is needed to account for the overall major element composition of enstatite chondrites, assuming an initial system with a solar composition. The second step, water-vapor depletion, is needed to stabilize Si-bearing metal, oldhamite, and niningerite, which are characteristic minerals of the enstatite chondrites. Variations in closure temperatures are suggested by the way in which the bulk chemistry and mineral assemblages of predicted condensates change with temperature, and how these parameters correlate with the observations of enstatite chondrites. In general, most phases in type 3 enstatite chondrites appear to have ceased equilibrating with nebular gas at approximately 900-950 K, except for Fe-metal, which continued to partially react with nebular gas to temperatures as low as -700 K.

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“…Condensation calculations as a function of variable C/O ratio also show that the only "rocky" bodies that can possibly have C/O ratios approaching unity would be formed at C/O ~ 1 in otherwise solar composition material (e.g., see Larimer 1975, Larimer & Bartholomay 1979, Lodders & Fegley 1997. Thus the situation for rocky planets is completely different than that for gas giant planets where C/O ratios higher than the solar composition value can be produced by formation from solar composition material, e.g., as discussed by Lodders (2004) for Jupiter.…”

Section: Variable Abundances: H C Omentioning

confidence: 99%

Vaporization of the Earth: Application to Exoplanet Atmospheres

Schaefer

Lodders

Fegley

2012

ApJ

152

186

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Currently, there are about 3 dozen known super-Earth (M < 10 M ⊕ ), of which 8 are transiting planets suitable for atmospheric follow-up observations. Some of the planets are exposed to extreme temperatures as they orbit close to their host stars, e.g., CoRot-7b, and all of these planets have equilibrium temperatures significantly hotter than the Earth.Such planets can develop atmospheres through (partial) vaporization of their crustal and/or mantle silicates. We investigated the chemical equilibrium composition of such heated systems from 500 -4000 K and total pressures from 10 -6 to 10 +2 bars. The major gases are H 2 O and CO 2 over broad temperature and pressure ranges, and Na, K, O 2 , SiO, and O at high temperatures and low pressures. We discuss the differences in atmospheric composition arising from vaporization of SiO 2 -rich (i.e., felsic) silicates (like Earth's continental crust) and MgO-, FeO-rich (i.e., mafic) silicates like the bulk silicate Earth.The computational results will be useful in planning spectroscopic studies of the atmospheres of Earth-like exoplanets.

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The role of carbon and oxygen in cosmic gases: some applications to the chemistry and mineralogy of enstatite chondrites

Cited by 185 publications

References 31 publications

FeO‐rich silicates in the Sahara 97159 (EH3) enstatite chondrite: Mineralogy, oxygen isotopic compositions, and origin

FeO‐rich silicates in the Sahara 97159 (EH3) enstatite chondrite: Mineralogy, oxygen isotopic compositions, and origin

A multi‐step model for the origin of E3 (enstatite) chondrites

Vaporization of the Earth: Application to Exoplanet Atmospheres

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