A Striking Nitrogen Isotope Anomaly in the Bencubbin and Weatherford Meteorites

Prombo, C. A.; Clayton, Robert N.

doi:10.1126/science.230.4728.935

Cited by 84 publications

(47 citation statements)

References 26 publications

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“…Recent work describing the nitrogen isotopic composition of the atmosphere of Titan has also been modeled to interpret its anomalous molecular nitrogen isotopic composition, which is a factor of two higher than the associated HCN (27). These careful calculations incorporated isotopic photoabsorption and photodissociation cross-sections for molecular nitrogen as well as consideration of coupling between Rydberg and valence states.Meteoritic nitrogen observations have revealed extraordinarily high bulk heavy nitrogen isotopic enrichments (28,29). High enrichments are also observed in spatially restricted hot spots within meteoritic material (30).…”

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confidence: 99%

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On the strong and selective isotope effect in the UV excitation of N ₂ with implications toward the nebula and Martian atmosphere

Muskatel

Remacle

Thiemens

et al. 2011

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

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Isotopic effects associated with molecular absorption are discussed with reference to natural phenomena including early solar system processes, Titan and terrestrial atmospheric chemistry, and Martian atmospheric evolution. Quantification of the physicochemical aspects of the excitation and dissociation processes may lead to enhanced understanding of these environments. Here we examine a physical basis for an additional isotope effect during photolysis of molecular nitrogen due to the coupling of valence and Rydberg excited states. The origin of this isotope effect is shown to be the coupling of diabatic electronic states of different bonding nature that occurs after the excitation of these states. This coupling is characteristic of energy regimes where two or more excited states are nearly crossing or osculating. A signature of the resultant isotope effect is a window of rapid variation in the otherwise smooth distribution of oscillator strengths vs. frequency. The reference for the discussion is the numerical solution of the time dependent Schrödinger equation for both the electronic and nuclear modes with the light field included as part of the Hamiltonian. Pumping is to all extreme UV dipole-allowed, valence and Rydberg, excited states of N 2 . The computed absorption spectra are convoluted with the solar spectrum to demonstrate the importance of including this isotope effect in planetary, interstellar molecular cloud, and nebular photochemical models. It is suggested that accidental resonance with strong discrete lines in the solar spectrum such as the CIII line at 97.703 nm can also have a marked effect.photodissociation | isotopic fractionation | UV photodissociation P hotochemical processes are particularly pervasive in nature. Measurements of isotopic compositions provide insights into a range of such processes, both terrestrial and extraterrestrial. To adequately interpret such measurements, characterization of relevant isotopically selective physicochemical processes associated with gas phase processes is desirable. In this paper we quantify an isotopic selectivity due to electronic reorganization following ligfht absorption. The results are compared to the solar spectrum for applications in nature.There are a number of photodissociation processes that have been suggested where a more basic understanding of isotope effects could aid in the development of models. A striking example of observed, but presently not fully understood oxygen isotopic distribution occurs in the high temperature calcium aluminum rich inclusions of the Allende meteorite (1) and most oxygen bearing meteorites (see, for example, review in ref.2). Although originally thought to be nucleosynthetic in origin based upon laboratory experiments, it was later suggested that the observed isotopic composition might arise from photochemical self-shielding (3-6). It has also been proposed that given the special properties of oxygen, symmetry related properties might produce the same fraction in the actual mineral formation process (7-11). A...

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“…Meteoritic nitrogen observations have revealed extraordinarily high bulk heavy nitrogen isotopic enrichments (28,29). High enrichments are also observed in spatially restricted hot spots within meteoritic material (30).…”

mentioning

confidence: 99%

On the strong and selective isotope effect in the UV excitation of N ₂ with implications toward the nebula and Martian atmosphere

Muskatel

Remacle

Thiemens

et al. 2011

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

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“…There is no evidence of Ni mobilization or recrystallization of chondritic fragments [Newsom and Drake, 1979]. The 15 N/ 14 N ratios in the silicate phases ofBencubbin are enriched by as much as a factor of2 [Prombo and Clayton, 1985], and the excess 15 N was interpreted to be due to a nucleosynthetic origin or to extreme isotopic fractionation [Prombo and Clayton, 1985]. Based on this extensive information, we thought it would be an interesting candidate for Pd-Ag investigation.…”

Section: Other Stony Iron Meteoritesmentioning

confidence: 99%

Live¹⁰⁷Pd in the Early Solar System and Implications for Planetary Evolution

Chen

Wasserburg

2013

Earth Processes: Reading the Isotopic Code

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We present a report on the status of 107 Pd (>r = 9.4 x 10 6 y) in the early solar system and the implications of its presence for protoplanet evolution. Over the last two decades we have carried out an extensive search for the evidence of presently extinct 107 Pd in meteorites. From these results we conclude that: 1) 107 Ag* (excess 107 Ag) is present in a wide variety of iron and stony-iron meteorites; 2) 107 Ag* is due to the in situ decay of 107 Pd in these meteorites; 3) Pd-Ag metal-PeS and metal whole-rock isochrons have been established for a few meteorites; 4) the correlation observed for the total metal isochrons reflects a large variation in normal silver contents ( -1 0 3 ) with much small variations in Pd contents (factors of 10); 5) there is a wide range in apparent Major fractionation between PdfAg can only be achieved during condensation, early accretion, and metal segregation in the solar nebula. The reaction ofFeNi with H 2 S gas to form PeS and subsequent melting and segregation ofFeNi and PeS provides a mechanism for minor (x2) fractionation. For some volatile-depleted meteorites, the processes of condensation ofFeNi with isolation from later condensates effectively fractionated PdfAg and produced metal with a 108 Pdf 109 Ag -10 4 -10 5 . For other meteorites not so extensively depleted in volatiles, a smaller degree of effective Pdf Ag fractionation is produced due to the presence of later condensates which, upon planetary melting, produced metal with a 108 Pdf 109 Ag-50-100. Some fractionation ofPd and Ag occurred by metal-liquid, metal-crystal fractionation during crystallization in planets similar to the models of Scott [1972], Larimer and Anders [1967], and Wai and Wasson [1977]. If the variation in initial 107 Pdf 108Pd among meteorites indicates a time difference (AT) in the condensation and melting-segregation of planetesimals, the data indicate a total range of -12 my for many meteorites. This tight cluster includes samples ofthe IIAB, IIIAB, IVA, IVB, and "anomalous" groups, as well as mesosiderites and pallasites. However, some meteorites exhibit no evidence of

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“…Most isotopic heterogeneities have been attributed to incomplete mixing of the primordial materials and or insertion of some materials of diverse nucleosynthetic origins during the condensation events of the solar system (see reviews by Anders, 1981;Begemann, 1980;1986;Rolfs et al, 1987). Existence of such other kinds of presolar grains in some of the regions of the mat ter that agglomerated to form stone meteorites, is now well recognised as manifested by the presence of variable ratios in: D/H ; 15N/ 14N (Lewis et al, 1983;Prombo and Clayton, 1985;Franchi et al, 1986); 13C / 12C (Zinner and Epstein, 1987;Grady et al, 1988); 110/160 (Clayton and Mayeda , 1984) and rare gases (Begemann, 1986).…”

Section: Introductionmentioning

confidence: 99%

Variations in the 190Os/184Os ratio in some stone meteorites and acid residues of Sikhote Alin iron meteorite.

Kumar¹,

Goel²

1991

Geochem. J.

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A Striking Nitrogen Isotope Anomaly in the Bencubbin and Weatherford Meteorites

Cited by 84 publications

References 26 publications

On the strong and selective isotope effect in the UV excitation of N ₂ with implications toward the nebula and Martian atmosphere

On the strong and selective isotope effect in the UV excitation of N ₂ with implications toward the nebula and Martian atmosphere

Live¹⁰⁷Pd in the Early Solar System and Implications for Planetary Evolution

Variations in the 190Os/184Os ratio in some stone meteorites and acid residues of Sikhote Alin iron meteorite.

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A Striking Nitrogen Isotope Anomaly in the Bencubbin and Weatherford Meteorites

Cited by 84 publications

References 26 publications

On the strong and selective isotope effect in the UV excitation of N 2 with implications toward the nebula and Martian atmosphere

On the strong and selective isotope effect in the UV excitation of N 2 with implications toward the nebula and Martian atmosphere

Live107Pd in the Early Solar System and Implications for Planetary Evolution

Variations in the 190Os/184Os ratio in some stone meteorites and acid residues of Sikhote Alin iron meteorite.

Contact Info

Product

Resources

About

On the strong and selective isotope effect in the UV excitation of N ₂ with implications toward the nebula and Martian atmosphere

On the strong and selective isotope effect in the UV excitation of N ₂ with implications toward the nebula and Martian atmosphere

Live¹⁰⁷Pd in the Early Solar System and Implications for Planetary Evolution