Transportation of gaseous elements and isotopes in a thermally evolving chondritic planetesimal

Hashizume, K.; Sugiura, N.

doi:10.1111/j.1945-5100.1998.tb01722.x

Cited by 16 publications

(12 citation statements)

References 36 publications

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“…For example, the vigor of C and N release from organics during thermal metamorphism depends on the redox conditions, particularly for C, which is incorporated into a gas under oxidizing conditions, but is stabilized in refractory compounds at more reducing conditions (23). This could account for much of the variation in C/N ratio seen in ordinary chondrites.…”

Section: Significancementioning

confidence: 99%

“…Volatile species, including some organics, would decompose in meteorite parent bodies at high temperatures and the liberated C and N could migrate to the surface as a gas and be lost to space or could be incorporated into metallic Fe,Ni (kamacite and taenite), owing to their siderophilic behavior (23). Thus, the abundances of both C and N are expected to diminish within bodies that were exposed to higher temperatures and more prolonged heating.…”

Section: Significancementioning

confidence: 99%

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Tracing the ingredients for a habitable earth from interstellar space through planet formation

Bergin

Blake

Ciesla

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

182

175

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We use the C/N ratio as a monitor of the delivery of key ingredients of life to nascent terrestrial worlds. Total elemental C and N contents, and their ratio, are examined for the interstellar medium, comets, chondritic meteorites, and terrestrial planets; we include an updated estimate for the bulk silicate Earth (C/N = 49.0 ± 9.3). Using a kinetic model of disk chemistry, and the sublimation/condensation temperatures of primitive molecules, we suggest that organic ices and macromolecular (refractory or carbonaceous dust) organic material are the likely initial C and N carriers. Chemical reactions in the disk can produce nebular C/N ratios of ∼1-12, comparable to those of comets and the low end estimated for planetesimals. An increase of the C/N ratio is traced between volatile-rich pristine bodies and larger volatile-depleted objects subjected to thermal/accretional metamorphism. The C/N ratios of the dominant materials accreted to terrestrial planets should therefore be higher than those seen in carbonaceous chondrites or comets. During planetary formation, we explore scenarios leading to further volatile loss and associated C/N variations owing to core formation and atmospheric escape. Key processes include relative enrichment of nitrogen in the atmosphere and preferential sequestration of carbon by the core. The high C/N bulk silicate Earth ratio therefore is best satisfied by accretion of thermally processed objects followed by large-scale atmospheric loss. These two effects must be more profound if volatile sequestration in the core is effective. The stochastic nature of these processes hints that the surface/atmospheric abundances of biosphereessential materials will likely be variable.terrestrial worlds | elements | interstellar medium | comets | meteorites T he development of a habitable world and a stable biosphere requires the delivery of biogenic elements of which carbon and nitrogen are crucial. Carbon is the backbone for the chemistry of life and, in the form of CO 2 , combines with water to provide the greenhouse needed for a habitable Earth. Nitrogen is a key component of DNA, RNA, and proteins, while also present as the dominant constituent of our atmosphere. The processes that supply these crucial ingredients remain poorly understood. In interstellar space, C and N are abundant, but inherently volatile and so chiefly remain in the gas. Thus, the terrestrial planets, which accrete primarily from rocks and ices, are fed from C-and N-depleted materials and are carbon and nitrogen poor compared with the nebular disk from which they descend (1, 2). The carbon and nitrogen depletion of rocky bodies is a general phenomenon, observable not just in our solar system, but also in the polluted atmospheres of white dwarf stars, which trace the composition of disrupted planetesimals (3, 4). This volatile poor state of terrestrial planets is partially imparted from the starting materials. However, further differential loss of C and N can occur due to parent body processes such as thermal metamorphism, core s...

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Section: Significancementioning

confidence: 99%

Section: Significancementioning

confidence: 99%

Tracing the ingredients for a habitable earth from interstellar space through planet formation

Bergin

Blake

Ciesla

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

182

175

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“…However, Schaefer and Fegley (2007) did not present results for the nominal pressure and temperature conditions proposed for Earth's putative steam atmosphere or consider several of the questions addressed in this paper. Hashizume and Sugiura (1998) did chemical equilibrium calculations of carbon speciation during metamorphism of ordinary chondritic material. They reported that CO was the major C-bearing gas, but as noted by Schaefer and Fegley (2007), after reading a preprint of their paper Professor Sugiura discovered that Hashizume and Sugiura (1998) used incorrect Gibbs energy data for CH 4 .…”

Section: Planet He Used H Chondritic and Various Mixtures Of H And Cmentioning

confidence: 99%

Chemistry of atmospheres formed during accretion of the Earth and other terrestrial planets

Schaefer

Fegley

2010

Icarus

180

134

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atmosphere with H 2 O being the second most abundant gas. Our results predict that the atmospheres formed during accretion of the Earth and Mars were probably H 2 -rich unless the accreted material was dominantly CI and CM carbonaceous chondritic material. We also predict significant amounts of S, P, Cl, F, Na, and K in accretionary atmospheres at high temperatures (1500 -2500 K). Finally, our results may be useful for interpreting spectroscopic observations of accreting extrasolar terrestrial planets.

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“…Antarctic CKs appear to have suffered less terrestrial contamination. Gibson and Yanai (1979) Despite the limited data available for CKs it is clear that total carbon contents tend to decrease with increasing metamorphic grade, a feature also seen in both the ordinary (Hashizume and Sugiura, 1998) and CO chondrites . As a defining characteristic of the CK group total carbon content is of limited value.…”

Section: Carbon Contentmentioning

confidence: 99%

The relationship between CK and CV chondrites

Greenwood¹,

Franchi²,

Kearsley³

et al. 2010

Geochimica et Cosmochimica Acta

103

195

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CK chondrites are highly oxidized meteorites containing abundant magnetite and trace amounts of Fe,Ni-metal. Although the group is predominately composed of equilibrated meteorites (types 4 to 6), in recent years a significant number of new samples have been classified as being either CK3 or CK3-anomalous. These unequilibrated CKs often display a close affinity with members of the CV oxidized subgroup. CKs and CVs (oxidized subgroup) may therefore form a continuum and by implication could be derived from a single common parent body. To investigate the relationship between these two groups a detailed study of the oxygen isotope composition, opaque mineralogy and major and trace element geochemistry of a suite of CV and CK chondrites has been undertaken. The results of oxygen isotope analysis confirm the close affinity between CV and CK chondrites, while excluding the possibility of a linkage between the CO and CK groups. Magnetites in both CV and CK chondrites show significant compositional similarities, but high Ti contents are a diagnostic feature of the latter group. The results of major and trace element analysis demonstrate that both CV and CK chondrites show overlapping variation. Supporting evidence for a single common source for both groups comes from their similar cosmic-ray exposure age distributions. Recent reflectance spectral analysis is consistent with both the CVs and CKs being derived from Eos family asteroids, which are believed to have formed by the catastrophic disruption of a single large asteroid. Thus, a range of evidence appears to be consistent with CV and CK chondrites representing samples from a single thermally stratified parent body. In view of the close similarity between CV and CK chondrites some modification of the present classification scheme may be warranted, possibly involving integration of the two groups. One means of achieving this would be to reassigned CK chondrites to a subgroup of the oxidized CVs. It is recognized that a full evaluation of this proposal may require further study of the still poorly understood CK3 chondrites. ACCEPTED MANUSCRIPT3

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Transportation of gaseous elements and isotopes in a thermally evolving chondritic planetesimal

Cited by 16 publications

References 36 publications

Tracing the ingredients for a habitable earth from interstellar space through planet formation

Tracing the ingredients for a habitable earth from interstellar space through planet formation

Chemistry of atmospheres formed during accretion of the Earth and other terrestrial planets

The relationship between CK and CV chondrites

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