30 results on '"Franchi IA"'
Search Results
2. Jiddat al Harasis 556: A howardite impact melt breccia with an H chondrite component
- Author
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Janots E, Gnos E, Hofmann BA, Greenwood RC, Franchi IA, Bermingham K, and Netwing V
- Abstract
–A petrographic and geochemical study was undertaken to characterize Jiddat al Harasis (JaH) 556 a howardite find from the Sultanate of Oman. JaH 556 is a polymict impact melt breccia containing highly shocked clasts including mosaicized olivine and recrystallized plagioclase set in a finely recrystallized vesicular matrix (grain diameter
- Published
- 2012
3. Elephant Moraine 96029, a very mildly aqueously altered and heated CM carbonaceous chondrite: implications for the drivers of parent body processing
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Lee, MR, Lindgren, P, King, AJ, Greenwood, RC, Franchi, IA, Sparkes, R, Lee, MR, Lindgren, P, King, AJ, Greenwood, RC, Franchi, IA, and Sparkes, R
- Abstract
Elephant Moraine (EET) 96029 is a CM carbonaceous chondrite regolith breccia with evidence for unusually mild aqueous alteration, a later phase of heating and terrestrial weathering. The presence of phyllosilicates and carbonates within chondrules and the fine-grained matrix indicates that this meteorite was aqueously altered in its parent body. Features showing that water-mediated processing was arrested at a very early stage include a matrix with a low magnesium/iron ratio, chondrules whose mesostasis contains glass and/or quench crystallites, and a gehlenite-bearing calcium- and aluminium-rich inclusion. EET 96029 is also rich in Fe,Ni metal relative to other CM chondrites, and more was present prior to its partial replacement by goethite during Antarctic weathering. In combination, these properties indicate that EET 96029 is one of the least aqueously altered CMs yet described (CM2.7) and so provides new insights into the original composition of its parent body. Following aqueous alteration, and whilst still in the parent body regolith, the meteorite was heated to ∼400–600 °C by impacts or solar radiation. Heating led to the amorphisation and dehydroxylation of serpentine, replacement of tochilinite by magnetite, loss of sulphur from the matrix, and modification to the structure of organic matter that includes organic nanoglobules. Significant differences between samples in oxygen isotope compositions, and water/hydroxyl contents, suggests that the meteorite contains lithologies that have undergone different intensities of heating. EET 96029 may be more representative of the true nature of parent body regoliths than many other CM meteorites, and as such can help interpret results from the forthcoming missions to study and return samples from C-complex asteroids.
- Published
- 2016
4. A parent body association for the carbonaceous chondrite groups
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Bland, PA, Sephton, MA, Young, ED, Hoffman, E, Franchi, IA, and Berry, FJ
- Abstract
Accepted version
- Published
- 2000
5. Pinpointing the source of a lunar meteorite: implications for the evolution of the moon
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Gnos, E, Hofmann, B, al Kathiri, A, Lorenzetti, S, Eugster, O, Whitehouse, M, Villa, I, Jull, A, Eikenberg, J, Spettel, B, Krähenbühl, U, Franchi, I, Greenwood, R, Gnos E, Hofmann, BA, Whitehouse, MJ, Jull, AJT, Franchi, IA, Greenwood, RC, VILLA, IGOR MARIA, Gnos, E, Hofmann, B, al Kathiri, A, Lorenzetti, S, Eugster, O, Whitehouse, M, Villa, I, Jull, A, Eikenberg, J, Spettel, B, Krähenbühl, U, Franchi, I, Greenwood, R, Gnos E, Hofmann, BA, Whitehouse, MJ, Jull, AJT, Franchi, IA, Greenwood, RC, and VILLA, IGOR MARIA
- Abstract
The lunar meteorite Sayh at Uhaymir 169 consists of an impact melt breccia extremely enriched with potassium, rare earth elements, and phosphorus [thorium, 32.7 parts per million (ppm); uranium, 8.6 ppm; potassium oxide, 0.54 weight percent], and adherent regolith. The isotope systematics of the meteorite record four lunar impact events at 3909 ± 13 million years ago (Ma), ∼2800 Ma, ∼200 Ma, and <0.34 Ma, and collision with Earth sometime after 9.7 ± 1.3 thousand years ago. With these data, we can link the impact-melt breccia to Imbrium and pinpoint the source region of the meteorite to the Lalande impact crater.
- Published
- 2004
6. The formation and aqueous alteration of CM2 chondrites and their relationship to CO3 chondrites: a fresh isotopic (O, Cd, Cr, Si, Te, Ti and Zn) perspective from the Winchcombe CM2 fall
- Author
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R. C. Greenwood, R. Findlay, R. Martins, R. C. J. Steele, K. M. M. Shaw, E. Morton, P. S. Savage, M. E. Murphy, M. Rehkämper, I. A. Franchi, T. Elliott, M. D. Suttle, A. J. King, M. Anand, J. Malley, K. T. Howard, X. Zhao, D. Johnson, M.‐C. Liu, K. A. McCain, N. R. Stephen, University of St Andrews. School of Earth & Environmental Sciences, University of St Andrews. St Andrews Centre for Exoplanet Science, University of St Andrews. St Andrews Isotope Geochemistry, Greenwood, RC [0000-0002-5544-8027], Findlay, R [0000-0001-7794-1819], Martins, R [0000-0003-2453-5942], Steele, RCJ [0000-0003-1406-6855], Shaw, KMM [0000-0002-3847-9382], Morton, E [0000-0001-6208-2388], Savage, PS [0000-0001-8464-0264], Murphy, ME [0000-0003-0385-9526], Rehkämper, M [0000-0002-0075-9872], Franchi, IA [0000-0003-4151-0480], Elliott, T [0000-0002-0984-0191], Suttle, MD [0000-0001-7165-2215], King, AJ [0000-0001-6113-5417], Anand, M [0000-0003-4026-4476], Zhao, X [0000-0003-0268-8139], Johnson, D [0009-0005-7239-412X], Liu, MC [0000-0003-4030-5258], McCain, KA [0000-0002-0811-135X], Stephen, NR [0000-0003-3952-922X], and Apollo - University of Cambridge Repository
- Subjects
Geophysics ,Space and Planetary Science ,MCP ,NDAS ,5109 Space Sciences ,51 Physical Sciences - Abstract
STFC are acknowledged for supporting the “Curation and Preliminary Examination of the Winchcombe Carbonaceous Chondrite Fall” project (ST/V000799/1), and Natural History Museum staff for curatorial support. Oxygen isotope studies at the Open University are funded by a consolidated grant from the Science and Technology Facilities Council (STFC), UK GRANT NUMBER: ST/T000228/1 (IAF, RCG, JM, MA), and STFC studentship NUMBER: ST/S505614/1 (RF). As part of an integrated consortium study, we have undertaken O, Cd, Cr, Si, Te, Ti, and Zn whole rock isotopic measurements of the Winchcombe CM2 meteorite. δ66Zn values determined for two Winchcombe aliquots are +0.29 ± 0.05‰ (2SD) and +0.45 ± 0.05‰ (2SD). The difference between these analyses likely reflects sample heterogeneity. Zn isotope compositions for Winchcombe show excellent agreement with published CM2 data. δ114Cd for a single Winchcombe aliquot is +0.29 ± 0.04‰ (2SD), which is close to a previous result for Murchison. δ130Te values for three aliquots gave indistinguishable results, with a mean value of +0.62 ± 0.01‰ (2SD) and are essentially identical to published values for CM2s. ε53Cr and ε54Cr for Winchcombe are 0.319 ± 0.029 (2SE) and 0.775 ± 0.067 (2SE), respectively. Based on its Cr isotopic composition, Winchcombe plots close to other CM2 chondrites. ε50Ti and ε46Ti values for Winchcombe are 3.21 ± 0.09 (2SE) and 0.46 ± 0.08 (2SE), respectively, and are in line with recently published data for CM2s. The δ30Si composition of Winchcombe is −0.50 ± 0.06‰ (2SD, n = 11) and is essentially indistinguishable from measurements obtained on other CM2 chondrites. In conformity with petrographic observations, oxygen isotope analyses of both bulk and micromilled fractions from Winchcombe clearly demonstrate that its parent body experienced extensive aqueous alteration. The style of alteration exhibited by Winchcombe is consistent with relatively closed system processes. Analysis of different fractions within Winchcombe broadly support the view that, while different lithologies within an individual CM2 meteorite can be highly variable, each meteorite is characterized by a predominant alteration type. Mixing of different lithologies within a regolith environment to form cataclastic matrix is supported by oxygen isotope analysis of micromilled fractions from Winchcombe. Previously unpublished bulk oxygen isotope data for 12 CM2 chondrites, when combined with published data, define a well‐constrained regression line with a slope of 0.77. Winchcombe analyses define a more limited linear trend at the isotopically heavy, more aqueously altered, end of the slope 0.77 CM2 array. The CM2 slope 0.77 array intersects the oxygen isotope field of CO3 falls, indicating that the unaltered precursor material to the CMs was essentially identical in oxygen isotope composition to the CO3 falls. Our data are consistent with earlier suggestions that the main differences between the CO3s and CM2s reflect differing amounts of water ice that co‐accreted into their respective parent bodies, being high in the case of CM2s and low in the case of CO3s. The small difference in Si isotope compositions between the CM and CO meteorites can be explained by different proportions of matrix versus refractory silicates. CMs and COs may also be indistinguishable with respect to Ti and Cr isotopes; however, further analysis is required to test this possibility. The close relationship between CO3 and CM2 chondrites revealed by our data supports the emerging view that the snow line within protoplanetary disks marks an important zone of planetesimal accretion. Publisher PDF
- Published
- 2023
7. A primordial noble gas component discovered in the Ryugu asteroid and its implications.
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Verchovsky AB, Abernethy FAJ, Anand M, Franchi IA, Grady MM, Greenwood RC, Barber SJ, Suttle M, Ito M, Tomioka N, Uesugi M, Yamaguchi A, Kimura M, Imae N, Shirai N, Ohigashi T, Liu MC, Uesugi K, Nakato A, Yogata K, Yuzawa H, Karouji Y, Nakazawa S, Okada T, Saiki T, Tanaka S, Terui F, Yoshikawa M, Miyazaki A, Nishimura M, Yada T, Abe M, Usui T, Watanabe SI, and Tsuda Y
- Abstract
Ryugu is the C-type asteroid from which material was brought to Earth by the Hayabusa2 mission. A number of individual grains and fine-grained samples analysed so far for noble gases have indicated that solar wind and planetary (known as P1) noble gases are present in Ryugu samples with concentrations higher than those observed in CIs, suggesting the former to be more primitive compared to the latter. Here we present results of analyses of three fine-grained samples from Ryugu, in one of which Xe concentration is an order of magnitude higher than determined so far in other samples from Ryugu. Isotopically, this Xe resembles P1, but with a much stronger isotopic fractionation relative to solar wind and significantly lower
36 Ar/132 Xe ratio than in P1. This previously unknown primordial noble gas component (here termed P7) provides clues to constrain how the solar composition was fractionated to form the planetary components., (© 2024. Crown.)- Published
- 2024
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8. The Winchcombe meteorite, a unique and pristine witness from the outer solar system.
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King AJ, Daly L, Rowe J, Joy KH, Greenwood RC, Devillepoix HAR, Suttle MD, Chan QHS, Russell SS, Bates HC, Bryson JFJ, Clay PL, Vida D, Lee MR, O'Brien Á, Hallis LJ, Stephen NR, Tartèse R, Sansom EK, Towner MC, Cupak M, Shober PM, Bland PA, Findlay R, Franchi IA, Verchovsky AB, Abernethy FAJ, Grady MM, Floyd CJ, Van Ginneken M, Bridges J, Hicks LJ, Jones RH, Mitchell JT, Genge MJ, Jenkins L, Martin PE, Sephton MA, Watson JS, Salge T, Shirley KA, Curtis RJ, Warren TJ, Bowles NE, Stuart FM, Di Nicola L, Györe D, Boyce AJ, Shaw KMM, Elliott T, Steele RCJ, Povinec P, Laubenstein M, Sanderson D, Cresswell A, Jull AJT, Sýkora I, Sridhar S, Harrison RJ, Willcocks FM, Harrison CS, Hallatt D, Wozniakiewicz PJ, Burchell MJ, Alesbrook LS, Dignam A, Almeida NV, Smith CL, Clark B, Humphreys-Williams ER, Schofield PF, Cornwell LT, Spathis V, Morgan GH, Perkins MJ, Kacerek R, Campbell-Burns P, Colas F, Zanda B, Vernazza P, Bouley S, Jeanne S, Hankey M, Collins GS, Young JS, Shaw C, Horak J, Jones D, James N, Bosley S, Shuttleworth A, Dickinson P, McMullan I, Robson D, Smedley ARD, Stanley B, Bassom R, McIntyre M, Suttle AA, Fleet R, Bastiaens L, Ihász MB, McMullan S, Boazman SJ, Dickeson ZI, Grindrod PM, Pickersgill AE, Weir CJ, Suttle FM, Farrelly S, Spencer I, Naqvi S, Mayne B, Skilton D, Kirk D, Mounsey A, Mounsey SE, Mounsey S, Godfrey P, Bond L, Bond V, Wilcock C, Wilcock H, and Wilcock R
- Abstract
Direct links between carbonaceous chondrites and their parent bodies in the solar system are rare. The Winchcombe meteorite is the most accurately recorded carbonaceous chondrite fall. Its pre-atmospheric orbit and cosmic-ray exposure age confirm that it arrived on Earth shortly after ejection from a primitive asteroid. Recovered only hours after falling, the composition of the Winchcombe meteorite is largely unmodified by the terrestrial environment. It contains abundant hydrated silicates formed during fluid-rock reactions, and carbon- and nitrogen-bearing organic matter including soluble protein amino acids. The near-pristine hydrogen isotopic composition of the Winchcombe meteorite is comparable to the terrestrial hydrosphere, providing further evidence that volatile-rich carbonaceous asteroids played an important role in the origin of Earth's water.
- Published
- 2022
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9. Isotopic evidence for pallasite formation by impact mixing of olivine and metal during the first 10 million years of the Solar System.
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Windmill RJ, Franchi IA, Hellmann JL, Schneider JM, Spitzer F, Kleine T, Greenwood RC, and Anand M
- Abstract
Pallasites are mixtures of core and mantle material that may have originated from the core-mantle boundary of a differentiated body. However, recent studies have introduced the possibility that they record an impact mix, in which case an isotopic difference between metal and silicates in pallasites may be expected. We report a statistically significant oxygen isotope disequilibrium between olivine and chromite in main group pallasites that implies the silicate and metal portions of these meteorites stem from distinct isotopic reservoirs. This indicates that these meteorites were formed by impact mixing, during which a planetary core was injected into the mantle of another body. The impactor likely differentiated within ∼1-2 Myr of the start of the Solar System based on Hf-W chronology of pallasite metal, and we infer the age of the impact based on Mn-Cr systematics and cooling rates at between ∼1.5 and 9.5 Myr after Ca-Al-rich inclusions (CAIs). When combined with published slow subsolidus cooling rates for these meteorites and considering that several pallasite groups exist, our results indicate that such impacts may be an important stage in the evolution of planetary bodies., (© The Author(s) 2022. Published by Oxford University Press on behalf of the National Academy of Sciences.)
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- 2022
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10. Publisher Correction: Organic matter and water from asteroid Itokawa.
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Chan QHS, Stephant A, Franchi IA, Zhao X, Brunetto R, Kebukawa Y, Noguchi T, Johnson D, Price MC, Harriss KH, Zolensky ME, and Grady MM
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- 2021
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11. Organic matter and water from asteroid Itokawa.
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Chan QHS, Stephant A, Franchi IA, Zhao X, Brunetto R, Kebukawa Y, Noguchi T, Johnson D, Price MC, Harriss KH, Zolensky ME, and Grady MM
- Abstract
Understanding the true nature of extra-terrestrial water and organic matter that were present at the birth of our solar system, and their subsequent evolution, necessitates the study of pristine astromaterials. In this study, we have studied both the water and organic contents from a dust particle recovered from the surface of near-Earth asteroid 25143 Itokawa by the Hayabusa mission, which was the first mission that brought pristine asteroidal materials to Earth's astromaterial collection. The organic matter is presented as both nanocrystalline graphite and disordered polyaromatic carbon with high D/H and
15 N/14 N ratios (δD = + 4868 ± 2288‰; δ15 N = + 344 ± 20‰) signifying an explicit extra-terrestrial origin. The contrasting organic feature (graphitic and disordered) substantiates the rubble-pile asteroid model of Itokawa, and offers support for material mixing in the asteroid belt that occurred in scales from small dust infall to catastrophic impacts of large asteroidal parent bodies. Our analysis of Itokawa water indicates that the asteroid has incorporated D-poor water ice at the abundance on par with inner solar system bodies. The asteroid was metamorphosed and dehydrated on the formerly large asteroid, and was subsequently evolved via late-stage hydration, modified by D-enriched exogenous organics and water derived from a carbonaceous parent body.- Published
- 2021
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12. Multiple early-formed water reservoirs in the interior of Mars.
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Barnes JJ, McCubbin FM, Santos AR, Day JMD, Boyce JW, Schwenzer SP, Ott U, Franchi IA, Messenger S, Anand M, and Agee CB
- Abstract
The abundance and distribution of water within Mars through time plays a fundamental role in constraining its geological evolution and habitability. The isotopic composition of martian hydrogen provides insights into the interplay between different water reservoirs on Mars. However, D/H (deuterium/hydrogen) ratios of martian rocks and of the martian atmosphere span a wide range of values. This has complicated identification of distinct water reservoirs in and on Mars within the confines of existing models that assume an isotopically homogenous mantle. Here we present D/H data collected by secondary ion mass spectrometry for two martian meteorites. These data indicate that the martian crust has been characterized by a constant D/H ratio over the last 3.9 billion years. The crust represents a reservoir with a D/H ratio that is intermediate between at least two isotopically distinct primordial water reservoirs within the martian mantle, sampled by partial melts from geochemically depleted and enriched mantle sources. From mixing calculations, we find that a subset of depleted martian basalts are consistent with isotopically light hydrogen (low D/H) in their mantle source, whereas enriched shergottites sampled a mantle source containing heavy hydrogen (high D/H). We propose that the martian mantle is chemically heterogeneous with multiple water reservoirs, indicating poor mixing within the mantle after accretion, differentiation, and its subsequent thermochemical evolution., Competing Interests: Financial/Non-financial Competing Interests We declare no financial or non-financial competing interests related to this work.
- Published
- 2020
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13. Oxygen isotopic evidence for accretion of Earth's water before a high-energy Moon-forming giant impact.
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Greenwood RC, Barrat JA, Miller MF, Anand M, Dauphas N, Franchi IA, Sillard P, and Starkey NA
- Abstract
The Earth-Moon system likely formed as a result of a collision between two large planetary objects. Debate about their relative masses, the impact energy involved, and the extent of isotopic homogenization continues. We present the results of a high-precision oxygen isotope study of an extensive suite of lunar and terrestrial samples. We demonstrate that lunar rocks and terrestrial basalts show a 3 to 4 ppm (parts per million), statistically resolvable, difference in Δ
17 O. Taking aubrite meteorites as a candidate impactor material, we show that the giant impact scenario involved nearly complete mixing between the target and impactor. Alternatively, the degree of similarity between the Δ17 O values of the impactor and the proto-Earth must have been significantly closer than that between Earth and aubrites. If the Earth-Moon system evolved from an initially highly vaporized and isotopically homogenized state, as indicated by recent dynamical models, then the terrestrial basalt-lunar oxygen isotope difference detected by our study may be a reflection of post-giant impact additions to Earth. On the basis of this assumption, our data indicate that post-giant impact additions to Earth could have contributed between 5 and 30% of Earth's water, depending on global water estimates. Consequently, our data indicate that the bulk of Earth's water was accreted before the giant impact and not later, as often proposed.- Published
- 2018
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14. OSIRIS-REx Contamination Control Strategy and Implementation.
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Dworkin JP, Adelman LA, Ajluni T, Andronikov AV, Aponte JC, Bartels AE, Beshore E, Bierhaus EB, Brucato JR, Bryan BH, Burton AS, Callahan MP, Castro-Wallace SL, Clark BC, Clemett SJ, Connolly HC Jr, Cutlip WE, Daly SM, Elliott VE, Elsila JE, Enos HL, Everett DF, Franchi IA, Glavin DP, Graham HV, Hendershot JE, Harris JW, Hill SL, Hildebrand AR, Jayne GO, Jenkens RW Jr, Johnson KS, Kirsch JS, Lauretta DS, Lewis AS, Loiacono JJ, Lorentson CC, Marshall JR, Martin MG, Matthias LL, McLain HL, Messenger SR, Mink RG, Moore JL, Nakamura-Messenger K, Nuth JA 3rd, Owens CV, Parish CL, Perkins BD, Pryzby MS, Reigle CA, Righter K, Rizk B, Russell JF, Sandford SA, Schepis JP, Songer J, Sovinski MF, Stahl SE, Thomas-Keprta K, Vellinga JM, and Walker MS
- Abstract
OSIRIS-REx will return pristine samples of carbonaceous asteroid Bennu. This article describes how pristine was defined based on expectations of Bennu and on a realistic understanding of what is achievable with a constrained schedule and budget, and how that definition flowed to requirements and implementation. To return a pristine sample, the OSIRIS-REx spacecraft sampling hardware was maintained at level 100 A/2 and <180 ng/cm
2 of amino acids and hydrazine on the sampler head through precision cleaning, control of materials, and vigilance. Contamination is further characterized via witness material exposed to the spacecraft assembly and testing environment as well as in space. This characterization provided knowledge of the expected background and will be used in conjunction with archived spacecraft components for comparison with the samples when they are delivered to Earth for analysis. Most of all, the cleanliness of the OSIRIS-REx spacecraft was achieved through communication among scientists, engineers, managers, and technicians.- Published
- 2018
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15. An asteroidal origin for water in the Moon.
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Barnes JJ, Kring DA, Tartèse R, Franchi IA, Anand M, and Russell SS
- Abstract
The Apollo-derived tenet of an anhydrous Moon has been contested following measurement of water in several lunar samples that require water to be present in the lunar interior. However, significant uncertainties exist regarding the flux, sources and timing of water delivery to the Moon. Here we address those fundamental issues by constraining the mass of water accreted to the Moon and modelling the relative proportions of asteroidal and cometary sources for water that are consistent with measured isotopic compositions of lunar samples. We determine that a combination of carbonaceous chondrite-type materials were responsible for the majority of water (and nitrogen) delivered to the Earth-Moon system. Crucially, we conclude that comets containing water enriched in deuterium contributed significantly <20% of the water in the Moon. Therefore, our work places important constraints on the types of objects impacting the Moon ∼4.5-4.3 billion years ago and on the origin of water in the inner Solar System.
- Published
- 2016
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16. Petrography, stable isotope compositions, microRaman spectroscopy, and presolar components of Roberts Massif 04133: A reduced CV3 carbonaceous chondrite.
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Davidson J, Schrader DL, Alexander CM, Lauretta DS, Busemann H, Franchi IA, Greenwood RC, Connolly HC Jr, Domanik KJ, and Verchovsky A
- Abstract
Here, we report the mineralogy, petrography, C-N-O-stable isotope compositions, degree of disorder of organic matter, and abundances of presolar components of the chondrite Roberts Massif (RBT) 04133 using a coordinated, multitechnique approach. The results of this study are inconsistent with its initial classification as a Renazzo-like carbonaceous chondrite, and strongly support RBT 04133 being a brecciated, reduced petrologic type >3.3 Vigarano-like carbonaceous (CV) chondrite. RBT 04133 shows no evidence for aqueous alteration. However, it is mildly thermally altered (up to approximately 440 °C); which is apparent in its whole-rock C and N isotopic compositions, the degree of disorder of C in insoluble organic matter, low presolar grain abundances, minor element compositions of Fe,Ni metal, chromite compositions and morphologies, and the presence of unequilibrated silicates. Sulfides within type I chondrules from RBT 04133 appear to be pre-accretionary (i.e., did not form via aqueous alteration), providing further evidence that some sulfide minerals formed prior to accretion of the CV chondrite parent body. The thin section studied contains two reduced CV3 lithologies, one of which appears to be more thermally metamorphosed, indicating that RBT 04133, like several other CV chondrites, is a breccia and thus experienced impact processing. Linear foliation of chondrules was not observed implying that RBT 04133 did not experience high velocity impacts that could lead to extensive thermal metamorphism. Presolar silicates are still present in RBT 04133, although presolar SiC grain abundances are very low, indicating that the progressive destruction or modification of presolar SiC grains begins before presolar silicate grains are completely unidentifiable.
- Published
- 2014
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17. Tissint martian meteorite: a fresh look at the interior, surface, and atmosphere of Mars.
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Aoudjehane HC, Avice G, Barrat JA, Boudouma O, Chen G, Duke MJ, Franchi IA, Gattacceca J, Grady MM, Greenwood RC, Herd CD, Hewins R, Jambon A, Marty B, Rochette P, Smith CL, Sautter V, Verchovsky A, Weber P, and Zanda B
- Subjects
- Carbon Isotopes analysis, Iron Compounds analysis, Magnesium Compounds analysis, Nitrogen Isotopes analysis, Oxygen Isotopes analysis, Silicates analysis, Mars, Meteoroids
- Abstract
Tissint (Morocco) is the fifth martian meteorite collected after it was witnessed falling to Earth. Our integrated mineralogical, petrological, and geochemical study shows that it is a depleted picritic shergottite similar to EETA79001A. Highly magnesian olivine and abundant glass containing martian atmosphere are present in Tissint. Refractory trace element, sulfur, and fluorine data for the matrix and glass veins in the meteorite indicate the presence of a martian surface component. Thus, the influence of in situ martian weathering can be unambiguously distinguished from terrestrial contamination in this meteorite. Martian weathering features in Tissint are compatible with the results of spacecraft observations of Mars. Tissint has a cosmic-ray exposure age of 0.7 ± 0.3 million years, consistent with those of many other shergottites, notably EETA79001, suggesting that they were ejected from Mars during the same event.
- Published
- 2012
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18. An anomalous basaltic meteorite from the innermost main belt.
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Bland PA, Spurny P, Towner MC, Bevan AW, Singleton AT, Bottke WF Jr, Greenwood RC, Chesley SR, Shrbeny L, Borovicka J, Ceplecha Z, McClafferty TP, Vaughan D, Benedix GK, Deacon G, Howard KT, Franchi IA, and Hough RM
- Abstract
Triangulated observations of fireballs allow us to determine orbits and fall positions for meteorites. The great majority of basaltic meteorites are derived from the asteroid 4 Vesta. We report on a recent fall that has orbital properties and an oxygen isotope composition that suggest a distinct parent body. Although its orbit was almost entirely contained within Earth's orbit, modeling indicates that it originated from the innermost main belt. Because the meteorite parent body would likely be classified as a V-type asteroid, V-type precursors for basaltic meteorites unrelated to Vesta may reside in the inner main belt. This starting location is in agreement with predictions of a planetesimal evolution model that postulates the formation of differentiated asteroids in the terrestrial planet region, with surviving fragments concentrated in the innermost main belt.
- Published
- 2009
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19. Infrared spectroscopy of comet 81P/Wild 2 samples returned by Stardust.
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Keller LP, Bajt S, Baratta GA, Borg J, Bradley JP, Brownlee DE, Busemann H, Brucato JR, Burchell M, Colangeli L, d'Hendecourt L, Djouadi Z, Ferrini G, Flynn G, Franchi IA, Fries M, Grady MM, Graham GA, Grossemy F, Kearsley A, Matrajt G, Nakamura-Messenger K, Mennella V, Nittler L, Palumbo ME, Stadermann FJ, Tsou P, Rotundi A, Sandford SA, Snead C, Steele A, Wooden D, and Zolensky M
- Subjects
- Cosmic Dust analysis, Spacecraft, Spectroscopy, Fourier Transform Infrared, Hydrocarbons analysis, Meteoroids, Silicates analysis
- Abstract
Infrared spectra of material captured from comet 81P/Wild 2 by the Stardust spacecraft reveal indigenous aliphatic hydrocarbons similar to those in interplanetary dust particles thought to be derived from comets, but with longer chain lengths than those observed in the diffuse interstellar medium. Similarly, the Stardust samples contain abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene. The presence of crystalline silicates in Wild 2 is consistent with mixing of solar system and interstellar matter. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust.
- Published
- 2006
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20. Impact features on Stardust: implications for comet 81P/Wild 2 dust.
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Hörz F, Bastien R, Borg J, Bradley JP, Bridges JC, Brownlee DE, Burchell MJ, Chi M, Cintala MJ, Dai ZR, Djouadi Z, Dominguez G, Economou TE, Fairey SA, Floss C, Franchi IA, Graham GA, Green SF, Heck P, Hoppe P, Huth J, Ishii H, Kearsley AT, Kissel J, Leitner J, Leroux H, Marhas K, Messenger K, Schwandt CS, See TH, Snead C, Stadermann FJ 1st, Stephan T, Stroud R, Teslich N, Trigo-Rodríguez JM, Tuzzolino AJ, Troadec D, Tsou P, Warren J, Westphal A, Wozniakiewicz P, Wright I, and Zinner E
- Abstract
Particles emanating from comet 81P/Wild 2 collided with the Stardust spacecraft at 6.1 kilometers per second, producing hypervelocity impact features on the collector surfaces that were returned to Earth. The morphologies of these surprisingly diverse features were created by particles varying from dense mineral grains to loosely bound, polymineralic aggregates ranging from tens of nanometers to hundreds of micrometers in size. The cumulative size distribution of Wild 2 dust is shallower than that of comet Halley, yet steeper than that of comet Grigg-Skjellerup.
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- 2006
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21. Elemental compositions of comet 81P/Wild 2 samples collected by Stardust.
- Author
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Flynn GJ, Bleuet P, Borg J, Bradley JP, Brenker FE, Brennan S, Bridges J, Brownlee DE, Bullock ES, Burghammer M, Clark BC, Dai ZR, Daghlian CP, Djouadi Z, Fakra S, Ferroir T, Floss C, Franchi IA, Gainsforth Z, Gallien JP, Gillet P, Grant PG, Graham GA, Green SF, Grossemy F, Heck PR, Herzog GF, Hoppe P, Hörz F, Huth J, Ignatyev K, Ishii HA, Janssens K, Joswiak D, Kearsley AT, Khodja H, Lanzirotti A, Leitner J, Lemelle L, Leroux H, Luening K, Macpherson GJ, Marhas KK, Marcus MA, Matrajt G, Nakamura T, Nakamura-Messenger K, Nakano T, Newville M, Papanastassiou DA, Pianetta P, Rao W, Riekel C, Rietmeijer FJ, Rost D, Schwandt CS, See TH, Sheffield-Parker J, Simionovici A, Sitnitsky I, Snead CJ, Stadermann FJ, Stephan T, Stroud RM, Susini J, Suzuki Y, Sutton SR, Taylor S, Teslich N, Troadec D, Tsou P, Tsuchiyama A, Uesugi K, Vekemans B, Vicenzi EP, Vincze L, Westphal AJ, Wozniakiewicz P, Zinner E, and Zolensky ME
- Abstract
We measured the elemental compositions of material from 23 particles in aerogel and from residue in seven craters in aluminum foil that was collected during passage of the Stardust spacecraft through the coma of comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size scale analyzed ( approximately 180 ng). The mean elemental composition of this Wild 2 material is consistent with the CI meteorite composition, which is thought to represent the bulk composition of the solar system, for the elements Mg, Si, Mn, Fe, and Ni to 35%, and for Ca and Ti to 60%. The elements Cu, Zn, and Ga appear enriched in this Wild 2 material, which suggests that the CI meteorites may not represent the solar system composition for these moderately volatile minor elements.
- Published
- 2006
- Full Text
- View/download PDF
22. Organics captured from comet 81P/Wild 2 by the Stardust spacecraft.
- Author
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Sandford SA, Aléon J, Alexander CM, Araki T, Bajt S, Baratta GA, Borg J, Bradley JP, Brownlee DE, Brucato JR, Burchell MJ, Busemann H, Butterworth A, Clemett SJ, Cody G, Colangeli L, Cooper G, D'Hendecourt L, Djouadi Z, Dworkin JP, Ferrini G, Fleckenstein H, Flynn GJ, Franchi IA, Fries M, Gilles MK, Glavin DP, Gounelle M, Grossemy F, Jacobsen C, Keller LP, Kilcoyne AL, Leitner J, Matrajt G, Meibom A, Mennella V, Mostefaoui S, Nittler LR, Palumbo ME, Papanastassiou DA, Robert F, Rotundi A, Snead CJ, Spencer MK, Stadermann FJ, Steele A, Stephan T, Tsou P, Tyliszczak T, Westphal AJ, Wirick S, Wopenka B, Yabuta H, Zare RN, and Zolensky ME
- Subjects
- Carbon analysis, Cosmic Dust analysis, Deuterium analysis, Nitrogen analysis, Nitrogen Isotopes analysis, Oxygen analysis, Polycyclic Aromatic Hydrocarbons analysis, Spacecraft, Meteoroids, Organic Chemicals analysis
- Abstract
Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.
- Published
- 2006
- Full Text
- View/download PDF
23. Comet 81P/Wild 2 under a microscope.
- Author
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Brownlee D, Tsou P, Aléon J, Alexander CM, Araki T, Bajt S, Baratta GA, Bastien R, Bland P, Bleuet P, Borg J, Bradley JP, Brearley A, Brenker F, Brennan S, Bridges JC, Browning ND, Brucato JR, Bullock E, Burchell MJ, Busemann H, Butterworth A, Chaussidon M, Cheuvront A, Chi M, Cintala MJ, Clark BC, Clemett SJ, Cody G, Colangeli L, Cooper G, Cordier P, Daghlian C, Dai Z, D'Hendecourt L, Djouadi Z, Dominguez G, Duxbury T, Dworkin JP, Ebel DS, Economou TE, Fakra S, Fairey SA, Fallon S, Ferrini G, Ferroir T, Fleckenstein H, Floss C, Flynn G, Franchi IA, Fries M, Gainsforth Z, Gallien JP, Genge M, Gilles MK, Gillet P, Gilmour J, Glavin DP, Gounelle M, Grady MM, Graham GA, Grant PG, Green SF, Grossemy F, Grossman L, Grossman JN, Guan Y, Hagiya K, Harvey R, Heck P, Herzog GF, Hoppe P, Hörz F, Huth J, Hutcheon ID, Ignatyev K, Ishii H, Ito M, Jacob D, Jacobsen C, Jacobsen S, Jones S, Joswiak D, Jurewicz A, Kearsley AT, Keller LP, Khodja H, Kilcoyne AL, Kissel J, Krot A, Langenhorst F, Lanzirotti A, Le L, Leshin LA, Leitner J, Lemelle L, Leroux H, Liu MC, Luening K, Lyon I, Macpherson G, Marcus MA, Marhas K, Marty B, Matrajt G, McKeegan K, Meibom A, Mennella V, Messenger K, Messenger S, Mikouchi T, Mostefaoui S, Nakamura T, Nakano T, Newville M, Nittler LR, Ohnishi I, Ohsumi K, Okudaira K, Papanastassiou DA, Palma R, Palumbo ME, Pepin RO, Perkins D, Perronnet M, Pianetta P, Rao W, Rietmeijer FJ, Robert F, Rost D, Rotundi A, Ryan R, Sandford SA, Schwandt CS, See TH, Schlutter D, Sheffield-Parker J, Simionovici A, Simon S, Sitnitsky I, Snead CJ, Spencer MK, Stadermann FJ, Steele A, Stephan T, Stroud R, Susini J, Sutton SR, Suzuki Y, Taheri M, Taylor S, Teslich N, Tomeoka K, Tomioka N, Toppani A, Trigo-Rodríguez JM, Troadec D, Tsuchiyama A, Tuzzolino AJ, Tyliszczak T, Uesugi K, Velbel M, Vellenga J, Vicenzi E, Vincze L, Warren J, Weber I, Weisberg M, Westphal AJ, Wirick S, Wooden D, Wopenka B, Wozniakiewicz P, Wright I, Yabuta H, Yano H, Young ED, Zare RN, Zega T, Ziegler K, Zimmerman L, Zinner E, and Zolensky M
- Abstract
The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales.
- Published
- 2006
- Full Text
- View/download PDF
24. Oxygen isotope variation in stony-iron meteorites.
- Author
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Greenwood RC, Franchi IA, Jambon A, Barrat JA, and Burbine TH
- Subjects
- Evolution, Planetary, Meteoroids, Minor Planets, Oxygen Isotopes
- Abstract
Asteroidal material, delivered to Earth as meteorites, preserves a record of the earliest stages of planetary formation. High-precision oxygen isotope analyses for the two major groups of stony-iron meteorites (main-group pallasites and mesosiderites) demonstrate that each group is from a distinct asteroidal source. Mesosiderites are isotopically identical to the howardite-eucrite-diogenite clan and, like them, are probably derived from the asteroid 4 Vesta. Main-group pallasites represent intermixed core-mantle material from a single disrupted asteroid and have no known equivalents among the basaltic meteorites. The stony-iron meteorites demonstrate that intense asteroidal deformation accompanied planetary accretion in the early Solar System.
- Published
- 2006
- Full Text
- View/download PDF
25. Widespread magma oceans on asteroidal bodies in the early Solar System.
- Author
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Greenwood RC, Franchi IA, Jambon A, and Buchanan PC
- Abstract
Immediately following the formation of the Solar System, small planetary bodies accreted, some of which melted to produce igneous rocks. Over a longer timescale (15-33 Myr), the inner planets grew by incorporation of these smaller objects through collisions. Processes operating on such asteroids strongly influenced the final composition of these planets, including Earth. Currently there is little agreement about the nature of asteroidal igneous activity: proposals range from small-scale melting, to near total fusion and the formation of deep magma oceans. Here we report a study of oxygen isotopes in two basaltic meteorite suites, the HEDs (howardites, eucrites and diogenites, which are thought to sample the asteroid 4 Vesta) and the angrites (from an unidentified asteroidal source). Our results demonstrate that these meteorite suites formed during early, global-scale melting (> or = 50 per cent) events. We show that magma oceans were present on all the differentiated Solar System bodies so far sampled. Magma oceans produced compositionally layered planetesimals; the modification of such bodies before incorporation into larger objects can explain some anomalous planetary features, such as Earth's high Mg/Si ratio.
- Published
- 2005
- Full Text
- View/download PDF
26. Pinpointing the source of a lunar meteorite: implications for the evolution of the Moon.
- Author
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Gnos E, Hofmann BA, Al-Kathiri A, Lorenzetti S, Eugster O, Whitehouse MJ, Villa IM, Jull AJ, Eikenberg J, Spettel B, Krähenbühl U, Franchi IA, and Greenwood RC
- Subjects
- Crystallization, Elements, Isotopes, Lead, Metals, Rare Earth analysis, Phosphorus analysis, Potassium analysis, Thorium analysis, Uranium analysis, Evolution, Planetary, Meteoroids, Moon
- Abstract
The lunar meteorite Sayh al Uhaymir 169 consists of an impact melt breccia extremely enriched with potassium, rare earth elements, and phosphorus [thorium, 32.7 parts per million (ppm); uranium, 8.6 ppm; potassium oxide, 0.54 weight percent], and adherent regolith. The isotope systematics of the meteorite record four lunar impact events at 3909 +/- 13 million years ago (Ma), approximately 2800 Ma, approximately 200 Ma, and <0.34 Ma, and collision with Earth sometime after 9.7 +/- 1.3 thousand years ago. With these data, we can link the impact-melt breccia to Imbrium and pinpoint the source region of the meteorite to the Lalande impact crater.
- Published
- 2004
- Full Text
- View/download PDF
27. Mass-independent fractionation of oxygen isotopes during thermal decomposition of carbonates.
- Author
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Miller MF, Franchi IA, Thiemens MH, Jackson TL, Brack A, Kurat G, and Pillinger CT
- Subjects
- Calcium Carbonate chemistry, Magnesium chemistry, Thermodynamics, Carbonates chemistry, Oxygen Isotopes isolation & purification
- Abstract
Nearly all chemical processes fractionate 17O and 18O in a mass-dependent way relative to 16O, a major exception being the formation of ozone from diatomic oxygen in the presence of UV radiation or electrical discharge. Investigation of oxygen three-isotope behavior during thermal decomposition of naturally occurring carbonates of calcium and magnesium in vacuo has revealed that, surprisingly, anomalous isotopic compositions are also generated during this process. High-precision measurements of the attendant three-isotope fractionation line, and consequently the magnitude of the isotopic anomaly (delta17O), demonstrate that the slope of the line is independent of the nature of the carbonate but is controlled by empirical factors relating to the decomposition procedure. For a slope identical to that describing terrestrial silicates and waters (0.5247 +/- 0.0007 at the 95% confidence level), solid oxides formed during carbonate pyrolysis fit a parallel line offset by -0.241 +/- 0.042 per thousand. The corresponding CO2 is characterized by a positive offset of half this magnitude, confirming the mass-independent nature of the fractionation. Slow, protracted thermolysis produces a fractionation line of shallower slope (0.5198 +/- 0.0007). These findings of a 17O anomaly being generated from a solid, and solely by thermal means, provide a further challenge to current understanding of the nature of mass-independent isotopic fractionation.
- Published
- 2002
- Full Text
- View/download PDF
28. A technique for the determination of 18O/16O and 17O/16O isotopic ratios in water from small liquid and solid samples.
- Author
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Baker L, Franchi IA, Maynard J, Wright IP, and Pillinger CT
- Subjects
- Oxygen Isotopes analysis, Water chemistry, Meteoroids, Oxygen analysis
- Abstract
We have developed a new technique in which a solid reagent, cobalt(III) fluoride, is used to prepare oxygen gas for isotope ratio measurement from water derived either from direct injection or from the pyrolysis of solid samples. The technique uses continuous flow, isotope ratio monitoring, gas chromatography/mass spectrometry (irmGC/MS) to measure the delta18O and delta17O of the oxygen gas. Water from appropriate samples is evolved by a procedure of stepped pyrolysis (0-1000 degrees C, typically in 50 degrees C increments) under a flowing stream of helium carrier gas. The method has considerable advantages over others used for water analysis in that it is quick; requires only small samples, typically 1-50 mg of whole rock samples (corresponding to approximately 0.2 micromol of H2O); and the reagent is easy and safe to handle. Reproducibility in isotope ratio measurement obtained from pyrolysis of samples of a terrestrial solid standard are delta18O +/- 0.54, delta17O +/- 0.33, and delta17O +/- 0.10/1000, 1sigma in all cases. The technique was developed primarily for the analysis of meteorites, and the efficiency of the method is illustrated herein by results from water standards, solid reference materials, and a sample of the Murchison CM2 meteorite.
- Published
- 2002
- Full Text
- View/download PDF
29. High precision delta(17)O isotope measurements of oxygen from silicates and other oxides: method and applications.
- Author
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Miller MF, Franchi IA, Sexton AS, and Pillinger CT
- Abstract
The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 µm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ( approximately 250) to provide (17)O and (18)O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1) of typically 0.08 and 0.04 per thousand are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by Delta(17)O; our precision (1) of such measurements on individual samples is shown to be +/-0.024 per thousand. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the (17)O versus (18)O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244+/- 0.00038 (standard error). Copyright 1999 John Wiley & Sons, Ltd.
- Published
- 1999
- Full Text
- View/download PDF
30. Terrestrial carbon and nitrogen isotopic ratios from cretaceous-tertiary boundary nanodiamonds.
- Author
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Gilmour I, Russell SS, Arden JW, Lee MR, Franchi IA, and Pillinger CT
- Abstract
One hypothesis for the origin of the nanometer-size diamonds found at the Cretaceous-Tertiary (K-T) boundary is that they are relict interstellar diamond grains carried by a postulated asteroid. The (13)C/(12)C and (15)N/(14)N ratios of the diamonds from two sites in North America, however, show that the diamonds are two component mixtures differing in carbon and nitrogen isotopic composition and nitrogen abundance. Samples from a site from Italy show no evidence for either diamond component. All the isotopic signatures obtained from the K-T boundary are material well distinguished from known meteoritic diamonds, particularly the fine-grain interstellar diamonds that are abundant in primitive chondrites. The K-T diamonds were most likely produced during the impact of the asteroid with Earth or in a plasma resulting from the associated fireball.
- Published
- 1992
- Full Text
- View/download PDF
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