bluuebunny/crossref_metadata_2025 huggingface dataset:
Stardust in Stardust—The C, N, and O isotopic compositions of Wild 2 cometary matter in Al foil impacts
Authors: Stadermann Frank J. , Hoppe Peter , Floss Christine , Heck Philipp R. , Hörz Friedrich , Huth Joachim , Kearsley Anton T. , Leitner Jan , Marhas Kuljeet K. , Mckeegan Kevin D. , Stephan Thomas
Published: January 2010

Abstract— In January 2006, the Stardust mission successfully returned dust samples from the tail of comet 81P/Wild 2 in two principal collection media, low‐density silica aerogel and Al foil. While hypervelocity impacts at the Stardust encounter velocity of 6.1 km/s into Al foils are generally highly disruptive for natural, silicate‐dominated impactors, previous studies have shown that many craters retain sufficient residue to allow a determination of the elemental and isotopic compositions of the original projectile. We have used two NanoSIMS ion microprobes to perform C, N, and O isotope imaging measurements on four large (59–295 μm in diameter) and on 47 small (0.32–1.9 μm in diameter) Al‐foil impact craters as part of the Stardust preliminary examination (PE). Most analyzed residues in and around these craters are isotopically normal (solar) in their C, N, and O isotopic compositions. However, the debris in one large crater shows an average 15N enrichment of ˜450‰, which is similar to the bulk composition of some isotopically primitive interplanetary dust particles (IDPs) and to components of some primitive meteorites. A 250 nm grain in another large crater has an 17O enrichment with ˜2.65 times the solar 17O/16O ratio. Such an O isotopic composition is typical for circumstellar oxide or silicate grains from red giant or asymptotic giant branch stars. The discovery of this circumstellar grain clearly establishes that there is authentic stardust in the cometary samples returned by the Stardust mission. However, the low apparent abundance of circumstellar grains in Wild 2 samples and the preponderance of isotopically normal material indicates that the cometary matter is a diverse assemblage of presolar and solar system materials.
Discovery of non‐random spatial distribution of impacts in the Stardust cometary collector
Authors: Westphal Andrew J. , Bastien Ronald K. , Borg Janet , Bridges John , Brownlee Donald E. , Burchell Mark J. , Cheng Andrew F. , Clark Benton C. , Djouadi Zahia , Floss Christine , Franchi Ian , Gainsforth Zack , Graham Giles , Green Simon F. , Heck Philipp R. , HorÁNYI Mihaly , Hoppe Peter , Hörz Friedrich P. , Huth Joachim , Kearsley Anton , Leroux Hugues , Marhas Kuljeet , Nakamura‐Messenger Keiko , Sandford Scott A. , See Thomas H. , Stadermann Frank J. , Teslich Nick E. , Tsitrin Samuel , Warren Jack L. , Wozniakiewicz Penelope J. , Zolensky Michael E.
Published: January 2010

Abstract— We report the discovery that impacts in the Stardust cometary collector are not distributed randomly in the collecting media, but appear to be clustered on scales smaller than ˜10 cm. We also report the discovery of at least two populations of oblique tracks. We evaluate several hypotheses that could explain the observations. No hypothesis is consistent with all the observations, but the preponderance of evidence points toward at least one impact on the central Whipple shield of the spacecraft as the origin of both clustering and low‐angle oblique tracks. High‐angle oblique tracks unambiguously originate from a non‐cometary impact on the spacecraft bus just forward of the collector.
Potassium isotope abundances in Australasian tektites and microtektites
Authors: HERZOG G. F. , ALEXANDER C. M. O'D. , BERGER E. L. , DELANEY J. S. , GLASS B. P.
Published: January 2010

Abstract— We report electron microprobe determinations of the elemental compositions of 11 Australasian layered tektites and 28 Australasian microtektites; and ion microprobe determinations of the 41K/39K ratios of all 11 tektites and 13 of the microtektites. The elemental compositions agree well with literature values, although the average potassium concentrations measured here for microtektites, 1.1‐1.6 wt%, are lower than published average values, 1.9‐2.9 wt%.

The potassium isotope abundances of the Australasian layered tektites vary little. The average value of δ41K, 0.02 ± 0.12%0 (1 s̀ mean), is indistinguishable from the terrestrial value (= 0 by definition) as represented by our standard, thereby confirming four earlier tektite analyses of Humayun and Koeberl (2004). In agreement with those authors, we conclude that evaporation has significantly altered neither the isotopic nor the elemental composition of Australasian layered tektites for elements less volatile than potassium.

Although the average 41K/39K ratio of the microtektites, 1.1 ± 1.7%0 (1 s̀ mean), is also statistically indistinguishable from the value for the standard, the individual ratios vary over a very large range, from −10.6 ± 1.4%0 to +13.8 ± 1.5%0 and at least three of them are significantly different from zero. We interpret these larger variations in terms of the evaporation of isotopically light potassium; condensation of potassium in the vapor plume; partial or complete stirring and quenching of the melts; and the possible uptake of potassium from seawater. That the average 41K/39K ratio of the microtektites equals the terrestrial value suggests that the microtektite‐forming system was compositionally closed with respect to potassium and less volatile elements. The possibility remains open that 41K/39K ratios of microtektites vary systematically with location in the strewn field.
Shape, metal abundance, chemistry, and origin of chondrules in the Renazzo (CR) chondrite
Authors: EBEL Denton S. , WEISBERG Michael K. , HERTZ Jessica , CAMPBELL Andrew J.
Published: January 2010

Abstract— We used synchrotron X‐ray microtomography to image in 3‐dimensions (3D) eight whole chondrules in a ˜1 cm3piece of the Renazzo (CR) chondrite at ˜17 μm per volume element (voxel) edge. We report the first volumetric (3D) measurement of metal/silicate ratios in chondrules and quantify indices of chondrule sphericity. Volumetric metal abundances in whole chondrules range from 1 to 37 volume % in 8 measured chondrules and by inspection in tomography data. We show that metal abundances and metal grain locations in individual chondrules cannot be reliably obtained from single random 2D sections. Samples were physically cut to intersect representative chondrules multiple times and to verify 3D data. Detailed 2D chemical analysis combined with 3D data yield highly variable whole‐chondrule Mg/Si ratios with a supra‐chondritic mean value, yet the chemically diverse, independently formed chondrules are mutually complementary in preserving chondritic (solar) Fe/Si ratios in the aggregate CR chondrite. These results are consistent with localized chondrule formation and rapid accretion resulting in chondrule + matrix aggregates (meteorite parent bodies) that preserve the bulk chondritic composition of source regions.
Geochemistry of diogenites: Still more diversity in their parental melts
Authors: BARRAT J. A. , YAMAGUCHI A. , GREENWOOD R. C. , BENOIT M. , COTTEN J. , BOHN M. , FRANCHI I. A.
Published: January 2010

Abstract— We report on the major and trace element abundances of 18 diogenites, and O‐isotopes for 3 of them. Our analyses extend significantly the diogenite compositional range, both in respect of Mg‐rich (e.g., Meteorite Hills [MET] 00425, MgO = 31.5 wt%) and Mg‐poor varieties (e.g., Dhofar 700, MgO = 23 wt%). The wide ranges of siderophile and chalcophile element abundances are well explained by the presence of inhomogeneously distributed sulfide or metal grains within the analyzed chips. The behavior of incompatible elements in diogenites is more complex, as exemplified by the diversity of their REE patterns. Apart from a few diogenite samples that contain minute amounts of phosphate, and whose incompatible element abundances are unlike the orthopyroxene ones, the range of incompatible element abundances, and particularly the range of Dy/Yb ratios in diogenites is best explained by the diversity of their parental melts. We estimate that the FeO/MgO ratios of the diogenite parental melts range from about 1.4 to 3.5 and therefore largely overlap the values obtained for non‐cumulate eucrites. Our results rule out the often accepted view that all the diogenites formed from parental melts more primitive than eucrites during the crystallization of a magma ocean. Instead, they point to a more complex history, and suggest that diogenites were derived from liquids produced by the remelting of cumulates formed from the magma ocean.
Noble gases in presolar diamonds III: Implications of ion implantation experiments with synthetic nanodiamonds
Authors: HUSS Gary R. , OTT Ulrich , KOSCHEEV Alexey P.
Published: January 2010

Abstract— A series of experiments carried out by Koscheev et al. (1998, 2001, 2004, 2005) showed that the bimodal release of heavy noble gases from meteoritic nanodiamonds can be reproduced by a single implanted component. This paper investigates the implications of this result for interpreting the noble gas compositions of meteoritic nanodiamonds and for their origin and history. If the bimodal release exhibited by meteorite diamonds reflects release of the P3 noble gas component, then the composition inferred for the pure Xe‐HL end member changes slightly, the excesses of heavy krypton isotopes that define Kr‐H become less extreme, evidence appears for a Kr‐L component, and the nucleosynthetic contribution to argon becomes much smaller. After correction for cosmogenic neon inherited from the host meteorites, the neon in presolar diamonds shows evidence for pre‐irradiation, perhaps in interstellar space, and a nucleosynthetic component perhaps consistent with a supernova source. After a similar correction, helium also shows evidence for presolar irradiation and/or a nucleosynthetic component. For the case of presolar irradiation, due to the small size of the diamonds, a large entity must have been irradiated and recoiling product nuclei collected by the nanodiamonds. The high 3He/21Ne ratio (˜43) calls for a target with a (C + O)/heavier‐element ratio higher than in chondritic abundances. Bulk gas + dust (cosmic abundances) meet this criteria, as would solids enriched in carbonaceous material. The long recoil range of cosmogenic 3He argues against a specific phase. The excess 3He in presolar diamonds may represent trapped cosmic rays rather than cosmogenic 3He produced in the vicinity of the diamond crystals.
The loss of K, REE, Th, and U from a Martian and a terrestrial basalt by acidic leaching
Authors: DREIBUS Gerlind , HAUBOLD Reinhard , HUISL Wolfgang , SPETTEL Bernhard
Published: January 2010

Abstract— The mobilization of K, rare earth elements (REE), Th, and U from Martian surface material upon contact with acidic solutions probably occurred extensively on Mars about 4 to 3.5 Ga ago and seems to have occurred locally in more recent times. We have studied the dissolution of these elements by leaching the basaltic shergottite Zagami and the terrestrial basalt BE‐N at constant pH values ranging from 5 to 1 in the absence and presence of added salts. Potassium is nearly immobile in Zagami and mobilized readily from BE‐N. The REE reside mostly in calcium phosphates and dissolve readily, with those in whitlockite of Zagami reacting slightly better than those in apatite of BE‐N. Thorium and U also reside mostly in calcium phosphates. Both dissolve similarly for both basalts and less readily than the REE. The experiments indicate the extent of the mobilization of K, REE, Th, and U, when acidic water leached the surface of Mars. Potassium was released slowly and in a small relative amount. The REE, and particularly the LREE, became mobile readily and were possibly distributed over large areas before immobilization. Thorium and U dissolved more slowly than the REE and were distributed less widely.
Mid‐sized complex crater formation in mixed crystalline‐sedimentary targets: Insight from modeling and observation
Authors: COLLINS G. S. , KENKMANN T. , OSINSKI G. R. , WÜNNEMANN K.
Published: January 2010

Abstract— Large impact crater formation is an important geologic process that is not fully understood. The current paradigm for impact crater formation is based on models and observations of impacts in homogeneous targets. Real targets are rarely uniform; for example, the majority of Earth's surface is covered by sedimentary rocks and/or a water layer. The ubiquity of layering across solar system bodies makes it important to understand the effect target properties have on the cratering process. To advance understanding of the mechanics of crater collapse, and the effect of variations in target properties on crater formation, the first “Bridging the Gap” workshop recommended that geological observation and numerical modeling focussed on mid‐sized (15–30 km diameter) craters on Earth. These are large enough to be complex; small enough to be mapped, surveyed and modelled at high resolution; and numerous enough for the effects of target properties to be potentially disentangled from the effects of other variables. In this paper, we compare observations and numerical models of three 18–26 km diameter craters formed in different target lithology: Ries, Germany; Haughton, Canada; and El'gygytgyn, Russia. Based on the first‐order assumption that the impact energy was the same in all three impacts we performed numerical simulations of each crater to construct a simple quantitative model for mid‐sized complex crater formation in a subaerial, mixed crystalline‐sedimentary target. We compared our results with interpreted geological profiles of Ries and Haughton, based on detailed new and published geological mapping and published geophysical surveys. Our combined observational and numerical modeling work suggests that the major structural differences between each crater can be explained by the difference in thickness of the pre‐impact sedimentary cover in each case. We conclude that the presence of an inner ring at Ries, and not at Haughton, is because basement rocks that are stronger than the overlying sediments are sufficiently close to the surface that they are uplifted and overturned during excavation and remain as an uplifted ring after modification and post‐impact erosion. For constant impact energy, transient and final crater diameters increase with increasing sediment thickness.
Impact penetration of Europa's ice crust as a mechanism for formation of chaos terrain
Authors: COX Rónadh , ONG Lissa C. F. , ARAKAWA Masahiko , SCHEIDER Kate C.
Published: January 2010

Abstract— Ice thickness estimates and impactor dynamics indicate that some impacts must breach Europa's ice crust; and outcomes of impact experiments using ice‐over‐water targets range from simple craters to chaos‐like destroyed zones, depending on impact energy and ice competence. First‐order impacts‐into thick ice or at low impact energy‐produce craters. Second‐order impacts punch through the ice, making holes that resemble raft‐free chaos areas. Third‐order impacts‐into thinnest ice or at highest energy‐produce large irregular raft‐filled zones similar to platy chaos. Other evidence for an impact origin for chaos areas comes from the size‐frequency distribution of chaos+craters on Europa, which matches the impact production functions of Ganymede and Callisto; and from small craters around the large chaos area Thera Macula, which decrease in average size and density per unit area as a function of distance from Thera's center. There are no tiny chaos areas and no craters >50 km diameter. This suggests that small impactors never penetrate, whereas large ones (ÜberPenetrators: >2.5 km diameter at average impact velocity) always do. Existence of both craters and chaos areas in the size range 2–40 km diameter points to spatial/temporal variation in crust thickness. But in this size range, craters are progressively outnumbered by chaos areas at larger diameters, suggesting that probability of penetration increases with increasing scale of impact. If chaos areas do represent impact sites, then Europa's surface is older than previously thought. The recalculated resurfacing age is 480 (‐302/+960) Ma: greater than prior estimates, but still very young by solar system standards.
Applied focused ion beam techniques for sample preparation of astromaterials for integrated nanoanalysis
Authors: Graham Giles A. , Teslich Nick E. , Kearsley Anton T. , Stadermann Frank J. , Stroud Rhonda M. , Dai Zurong , Ishii Hope A. , Hutcheon Ian D. , Bajt Saša , Snead Christopher J. , Weber Peter K. , Bradley John P.
Published: January 2010

Abstract— Sample preparation is always a critical step in the study of micrometer‐sized astromaterials available for study in the laboratory, whether their subsequent analysis is by electron microscopy or secondary ion mass spectrometry. A focused beam of gallium ions has been used to prepare electron transparent sections from an interplanetary dust particle (IDP), as part of an integrated analysis protocol to maximize the mineralogical, elemental, isotopic, and spectroscopic information extracted from one individual particle. In addition, focused ion beam (FIB) techniques have been employed to extract cometary residue preserved on the rims and walls of microcraters in 1100 series aluminum foils that were wrapped around the sample tray assembly on the Stardust cometary sample collector. Non‐ideal surface geometries and inconveniently located regions of interest required creative solutions. These include support pillar construction and relocation of a significant portion of sample to access a region of interest. Serial sectioning, in a manner similar to ultramicrotomy, is a significant development and further demonstrates the unique capabilities of focused ion beam microscopy for sample preparation of astromaterials.
PDF orientations in shocked quartz grains around the Chicxulub crater
Authors: NAKANO Yoichiro , GOTO Kazuhisa , MATSUI Takafumi , TADA Ryuji , TAJIKA Eiichi
Published: January 2010

Abstract— We measured 852 sets of planar deformation features (PDFs) in shocked quartz grains in impactite samples of the Yaxcopoil (YAX‐1) core and from 4 Cretaceous/Tertiary (K/T) boundary deposits: the Monaca, the Cacarajícara, and the Peñalver formations in Cuba, and DSDP site 536, within 800 km of the Chicxulub crater, in order to investigate variations of PDF orientations in the proximity of the crater. Orientations of PDFs show a broad distribution with peaks at ω {101¯3}, π {101¯2}, and ω {111¯2}, plus r, z {1011¯} orientations with minor c(0001), s{112¯1}, t{224¯1} plus x{516¯1}, and m{101¯0} plus a{112¯0} orientations. Planar deformation features with c(0001) orientation are relatively more abundant in the proximity of the Chicxulub crater than in distal sites such as North America, the Pacific Ocean, and Europe. This feature indicates that in the proximity of the crater, part of the shocked quartz grains in the K/T boundary deposits were derived from the low shock pressure zones. Moreover, the orientations of PDFs with ω {112¯2} plus r, z {101¯1} are high in our studied sites, and frequencies of these orientations decrease with increasing distance from the crater. On the other hand, absence of c(0001) and the rare occurrence of PDFs with ?ω {112¯2} plus r, z {101¯1} orientations in the sample from the YAX‐1 core that was taken at the top of the impactite layer of the Chicxulub crater suggests that the sampling horizon that reflects a certain cratering stage is also an important factor for variations in shocked quartz.
Ararki (L5) chondrite: The first meteorite find in Thar Desert of India
Authors: BHANDARI N. , MURTY S. V. S. , SHUKLA P. N. , MAHAJAN R. R. , SHUKLA A. D. , LASHKARI G. , SISODIA M. S. , TRIPATHI R. P. , PARTHASARATHY G. , VERMA H. C. , FRANCHI I. A.
Published: January 2010

Abstract— We report here a chance find of a meteorite in the sand dunes of Ararki village of Hanumangarh district in the Rajasthan desert of northwest India. Chemical and petrological evidence in conjunction with isotopic composition of oxygen indicate that it is an L5 chondrite. The fayalite content of olivines is 26.3 mol%. The meteorite has some serpentinized olivines and 0.3% carbon having a terrestrial isotopic composition, indicating that it is moderately weathered. The absence of 22Na indicate that the meteorite fell to Earth more than a decade ago. The cosmic‐ray exposure age based on cosmogenic 21Ne is 7.2 Ma. Low density of cosmic‐ray heavy nuclei tracks, low 26A1 activity, the shielding parameter [(22Ne/21Ne)C = 1.094] and absence of neutron capture effects indicate cosmic‐ray shielding in a meteoroid having radius of about 16 cm, implying a meteoroid mass of about 60 kg and ablation of about 93%. The gas retention ages, based on U/Th‐4He and K‐40Ar are 1.1 and 0.58 Ga, respectively, suggesting a heating and degassing event late in the history of this meteorite.
The 410,000 year terrestrial age of eucrite Río Cuarto 001
Authors: LEVINE Jonathan , ARAZI Andrés , FAESTERMANN Thomas , NIELLO Jorge O. FERNáNDEZ , KORSCHINEK Gunther , LA GAMMA Ana María , NEGRI Agustín , RUGEL Georg , STEIER Peter , WALLNER Anton
Published: January 2010

Abstract— We have measured a surprisingly long terrestrial age of 410,000 ±45,0020,000 yr (410 ±2045ka) for basaltic eucrite Río Cuarto 001 using accelerator mass spectrometry of 26Al, 36Cl, and 41Ca. Though many meteorites are known to have survived for tens or hundreds of ka in Antarctica or hot deserts, the mean annual precipitation of 815 mm in Río Cuarto, Cordoba Province, Argentina, makes the long survival of this meteorite remarkable. We propose two explanations for the exceptional preservation of Río Cuarto 001. First, the meteorite contains only trace amounts of metal, so the weathering and oxidation of metallic Fe, which commonly destroys chondrites, is ineffective in this case. Second, the meteorite was found in a relatively young deflation basin, and may have been exhumed only recently from beneath a protective layer of soil. Insofar as the survival on Earth of Río Cuarto 001 is due to environmental factors, there may be other meteorites with comparably long terrestrial ages still to be discovered in the vicinity.
Physical properties of meteorites—Applications in space missions to asteroids
Authors: KOHOUT T. , KLETETSCHKA G. , ELBRA T. , ADACHI T. , MIKULA V. , PESONEN L. J. , SCHNABL P. , SLECHTA S.
Published: January 2010

Abstract— Based on reflectance spectroscopy and chemical/mineralogical remote sensing methods, it is generally assumed that asteroids are parent bodies for most meteorites reaching the Earth. However, more detailed observations indicate that differences exist in composition between asteroids and meteorites resulting in difficulties when searching for meteorite‐asteroid match.

We show that among other physical parameters the magnetic susceptibility of an asteroid can be determined remotely from the magnetic induction by solar wind using an orbiting spacecraft or directly using the AC coil on the lander, or it can be measured in samples returned to the laboratory. The shape corrected value of the true magnetic susceptibility of an asteroid can be compared to those of meteorites in the existing database, allowing closer match between asteroids and meteorites. The database of physical properties contains over 700 samples and was recently enlarged with measurements of meteorites in European museums using mobile laboratory facility.
Structure and density of cometary nuclei
Authors: WEISSMAN Paul R. , LOWRY Stephen C.
Published: January 2010

Abstract— Understanding the nature of the cometary nucleus remains one of the major problems in solar system science. Whipple's (1950) icy conglomerate model has been very successful at explaining a range of cometary phenomena, including the source of cometary activity and the nongravitational orbital motion of the nuclei. However, the internal structure of the nuclei is still largely unknown. We review herein the evidence for cometary nuclei as fluffy aggregates or primordial rubble piles, as first proposed by Donn et al. (1985) and Weissman (1986). These models assume that cometary nuclei are weakly bonded aggregations of smaller, icy‐conglomerate planetesimals, possibly held together only by self‐gravity. Evidence for this model comes from studies of the accretion and subsequent evolution of material in the solar nebula, from observations of disrupted comets, and in particular comet Shoemaker‐Levy 9, from measurements of the ensemble rotational properties of observed cometary nuclei, and from recent spacecraft missions to comets. Although the evidence for rubble pile nuclei is growing, the eventual answer to this question will likely not come until we can place a spacecraft in orbit around a cometary nucleus and study it in detail over many months to years. ESA's Rosetta mission, now en route to comet 67P/Churyumov‐Gerasimenko, will provide that opportunity.
Crystallization experiments of intercumulus melts for nakhlites under QFM ± 2 at 1 bar
Authors: IMAE Naoya , IKEDA Yukio
Published: January 2010

Abstract— Crystallization of parent melts for nakhlites was experimentally studied under QFM ± 2 at one bar. Isothermal experiments suggest that melts having parent magma composition for nakhlites crystallize both augites and titanomagnetites at liquidus temperatures of 1144–1154 °C. Compositions of the augites are identical to those of phenocrystic core augites (En36–38Fs22–25Wo39–40) in nakhlites. No olivines crystallize from the isothermal runs, and solidus temperature is about 1000 °C.

Linear‐cooling experiments were carried out at various cooling rates (1–17 °C/h) ranging from liquidus to solidus temperatures under similar pressure conditions to the isothermal runs. Augites, titanomagnetites, and fayalites crystallized in the cooling runs, but magnesian olivines never crystallized there. Magnesian core augite in the cooling runs has the same composition as those of nakhlites. Rims of augite crystals from the cooling runs of 1–4 °C/h consist of two layers, ferroan augite inner rim and hedenbergite outer rim, which are very similar to those in the Miller Range (MIL) 03346 nakhlite. Small amounts of pyroxferroite crystallized in mesostasis and augite rims from two cooling runs. Titanomagnetites from cooling runs never accompany ilmenite lamellae as seen in nakhlites, suggesting that the subsolidus cooling rate of the cooling runs was much more rapid than those of nakhlite intercumulus melts. The cooling experiments reproduce the crystallization processes of pyroxenes and the compositional change of residual melt for a rapidly cooled magma such as MIL 03346.
The Meteoritical Bulletin, No. 94, September 2008
Authors: WEISBERG Michael K. , SMITH Caroline , BENEDIX Gretchen , FOLCO Luigi , RIGHTER Kevin , ZIPFEL Jutta , YAMAGUCHI Akira , AOUDJEHANE Hasnaa CHENNAOUI
Published: January 2010

Abstract— –The Meteoritical Bulletin 94 reports over 900 (119 non‐Antarctic and 803 Antarctic) newly approved meteorite names and their recovery histories, macroscopic descriptions, petrography, mineral compositions, and geochemistry. Meteorites reported include lunar, Martian, howardites, eucrites, diogenites, mesosiderites, aubrites, irons, angrites, ureilites, acapulcoites, lodranites and H, L, LL, R, CO, and CV chondrites. Eight of the meteorites in this bulletin are falls, including 4 from India (Jodiya, Kaprada, Kavapura, Mahadevpur), 1 from Mali (Chergach), Turkey (Didim), Libya (Werdama), and the U.S. (Berthoud).
The Isheyevo meteorite: Mineralogy, petrology, bulk chemistry, oxygen, nitrogen, carbon isotopic compositions, and 40Ar‐39Ar ages
Authors: IVANOVA Marina A. , KONONKOVA Natalia N. , KROT Alexander N. , GREENWOOD Richard C. , FRANCHI Ian A. , VERCHOVSKY Alexander B. , TRIELOFF Mario , KOROCHANTSEVA Ekaterina V. , BRANDSTÄTTER Franz
Published: January 2010

Abstract— Isheyevo is a metal‐rich carbonaceous chondrite that contains several lithologies with different abundances of Fe,Ni metal (7–90 vol%). The metal‐rich lithologies with 50–60 vol% of Fe,Ni metal are dominant. The metal‐rich and metal‐poor lithologies are most similar to the CBb and CH carbonaceous chondrites, respectively, providing a potential link between these chondrite groups. All lithologies experienced shock metamorphism of shock stage S4. All consist of similar components—Fe,Ni metal, chondrules, refractory inclusions (Ca, Al‐rich inclusions [CAIs] and amoeboid olivine aggregates [AOAs]), and heavily hydrated lithic clasts—but show differences in their modal abundances, chondrule sizes, and proportions of porphyritic versus non‐porphyritic chondrules. Bulk chemical and oxygen isotopic compositions are in the range of CH and CB chondrites. Bulk nitrogen isotopic composition is highly enriched in 15N (δ15N = 1122‰). The magnetic fraction is very similar to the bulk sample in terms of both nitrogen release pattern and isotopic profile; the non‐magnetic fraction contains significantly less heavy N. Carbon released at high temperatures shows a relatively heavy isotope signature. Similarly to CBb chondrites, ∼20% of Fe,Ni‐metal grains in Isheyevo are chemically zoned. Similarly to CH chondrites, some metal grains are Ni‐rich (>20 wt% Ni). In contrast to CBb and CH chondrites, most metal grains are thermally decomposed into Ni‐rich and Ni‐poor phases. Similar to CH chondrites, chondrules have porphyritic and non‐porphyritic textures and ferromagnesian (type I and II), silica‐rich, and aluminum‐rich bulk compositions. Some of the layered ferromagnesian chondrules are surrounded by ferrous olivine or phyllosilicate rims. Phyllosilicates in chondrule rims are compositionally distinct from those in the hydrated lithic clasts. Similarly to CH chondrites, CAIs are dominated by the hibonite‐, grossite‐, and melilite‐rich types; AOAs are very rare. We infer that Isheyevo is a complex mixture of materials formed by different processes and under different physico‐chemical conditions. Chondrules and refractory inclusions of two populations, metal grains, and heavily hydrated clasts accreted together into the Isheyevo parent asteroid in a region of the protoplanetary disk depleted in fine‐grained dust. Such a scenario is consistent with the presence of solar wind—implanted noble gases in Isheyevo and with its comparatively old K‐Ar age. We cannot exclude that the K‐Ar system was affected by a later collisional event. The cosmic‐ray exposure (CRE) age of Isheyevo determined by cosmogenic 38Ar is ∼34 Ma, similar to that of the Bencubbin (CBa) meteorite.
Molecular study of insoluble organic matter in Kainsaz CO3 carbonaceous chondrite: Comparison with CI and CM IOM
Authors: REMUSAT Laurent , Le GUILLOU Corentin , ROUZAUD Jean‐Noël , BINET Laurent , DERENNE Sylvie , ROBERT François
Published: January 2010

Abstract— Kainsaz CO3 insoluble organic matter (IOM) was studied using Curie point pyrolysis, electronic paramagnetic resonance (EPR), and high‐resolution transmission electron microscopy (HRTEM) to determine the effect of thermal metamorphism on molecular chondritic fingerprints. Pyrolysis released a very low amount of products that consist of one‐ and two‐ring aromatic units with methyl, dimethyl, and ethyl substituents. Moreover, Kainsaz IOM contains two orders of magnitude fewer radicals than Orgueil, Murchison, and Tagish Lake IOM. In addition, no diradicaloids were found in Kainsaz, although they are thought to constitute a specific signature for weakly organized extraterrestrial organic compounds in contrast to terrestrial ones. HRTEM reveals a very heterogeneous structure, with microporous disordered carbon, mesoporous graphitic carbons and graphite. Graphitization likely occurs and explains the differences between Kainsaz and CI or CM IOM. Heating stress experienced by Kainsaz IOM, on the parent body and/or prior its accretion, is likely responsible for the differences in molecular and structural organizations compared with those of CI and CM IOM.
In situ micro‐Raman and X‐ray diffraction study of diamonds and petrology of the new ureilite UAE 001 from the United Arab Emirates
Authors: HEZEL Dominik C. , DUBROVINSKY Leonid , NASDALA Lutz , CAUZID Jean , SIMIONOVICI Alexandre , GELLISSEN Marko , SCHÖNBECK Thorbjörn
Published: January 2010

Abstract— A new olivine‐pigeonite ureilite containing abundant diamonds and graphite was found in the United Arab Emirates. This is the first report of a meteorite in this country. The sample is heavily altered, of medium shock level, and has a total weight of 155 g. Bulk rock, olivine (Fo79.8–81.8) and pyroxene (En73.9–75.2, Fs15.5–16.9, Wo8.8–9.5) compositions are typical of ureilites. Olivine rims are reduced with Fo increasing up to Fo96.1–96.8. Metal in these rims is completely altered to Fehydroxide during terrestrial weathering. We studied diamond and graphite using micro‐Raman and in situ synchrotron X‐ray diffraction. The main diamond Raman band (LO = TO mode at ˜1332 cm−1) is broadened when compared to well‐ordered diamond single crystals. Full widths at half maximum (FWHM) values scatter around 7 cm−1. These values resemble FWHM values obtained from chemical vapor deposition (CVD) diamond. In situ XRD measurements show that diamonds have large grain sizes, up to >5 μm. Some of the graphite measured is compressed graphite. We explore the possibilities of CVD versus impact shock origin of diamonds and conclude that a shock origin is much more plausible. The broadening of the Raman bands might be explained by prolonged shock pressure resulting in a transitional Raman signal between experimentally shock‐produced and natural diamonds.
Impact melt rocks from the Paasselkä impact structure (SE Finland): Petrography and geochemistry
Authors: SCHMIEDER Martin , MOILANEN Jarmo , BUCHNER Elmar
Published: January 2010

Abstract— Recently, samples of allochthonous melt rocks from the ˜10 km and ≤1.9 Ga Paasselkä impact structure, SE Finland, were obtained. In this study, we present a first detailed petrographic and geochemical description of clast‐rich Paasselkä impact melt rocks. Shock metamorphic features comprise shocked feldspar grains, intensely shocked and toasted quartz, marginally molten and recrystallized clasts thought to have been diaplectic quartz glass, largely fresh and recrystallized feldspar glasses, decomposed biotite flakes, recrystallized fluidal silica glass (originally probably lechatelierite) in partially molten sandstone clasts, all set into a glassy to cryptocrystalline melt matrix. The degree of shock metamorphism of clasts suggests initial whole‐rock melting at peak shock pressures of ≥35 GPa and post‐shock temperatures of up to ˜1500 °C. Glass components vary in geochemical composition corresponding to the mixed character of the crystalline target rock (i.e., representing different monomineralic and mixed‐mineral melts). Feldspar glasses and the fresh glassy to cryptocrystalline melt matrix indicate that the Paasselkä melt rocks are not intensely altered. The geochemical composition of the Paasselkä impact melt rocks is roughly consistent with the compositions of melt rocks from a number of impact structures located within the crystalline basement of the Baltic Shield.
Petrogenetic linkages among Martian basalts: Implications based on trace element chemistry of olivine
Authors: SHEARER C. K. , BURGER P. V. , PAPDCE J. J. , BORG L. E. , IRVING A. J. , HERD C.
Published: January 2010

Abstract— The shergottites exhibit a range of major and trace element compositions, crystallization ages, and initial Sr, Nd, Hf, and Pb isotopic compositions. To constrain the physical mechanisms by which shergottites obtain their compositional characteristics, we examined the major and trace element record preserved in olivine in the more primitive shergottites. Based on such characteristics as the Mg#, V zoning, calculated DNi,Co, the olivine in Y‐980459 are most likely phenocrysts. Many of these same characteristics indicate that the olivines in other shergottites are not in equilibrium with the adjacent melt. However, in most cases they are not xenocrystic, but additions of olivine from the same basaltic system. Elephant Moraine (EET) A79001 may be an exception with the olivine data suggesting that it is xenocrystic. In this case, the olivine crystallized from a reduced and LREE‐depleted melt and was incorporated into an oxidized and enriched basalt. Vanadium and CaO in olivine appear to record the appearance of spinel and pyroxene on the liquidus of most of the shergottites. Most of the olivine shergottites represent basalts produced by melting of reduced (IW to IW + 1), depleted mantle sources. Olivine data indicate that many of the primary melts derived from this source had similar Ni, Co, and Mn. Shergottites such as Northwest Africa (NWA) 1110/1068 and perhaps Roberts Massif (RBT) 04261 that appear to be derived from more enriched sources have distinctly different olivine. In the case of NWA 1110/1068, the olivine data suggests that the enriched component was added to system prior to olivine crystallization.
K‐Ar dating of rocks on Mars: Requirements from Martian meteorite analyses and isochron modeling
Authors: BOGARD Donald D.
Published: January 2010

Abstract— Radiometric age dating of Martian rocks and surfaces at known locations for which crater densities can be determined is highly desirable in order to fully understand Martian history. Performing K‐Ar age dating of igneous rocks on Mars by robots, however, presents technical challenges. Some of these challenges can be defined by examining Ar‐Ar data acquired on Martian meteorites, and others can be evaluated through numerical modeling of simulated K‐Ar isochrons like those that would be acquired robotically on Martian rocks. Excess 40Ar is present in all shergottites. Thus for Martian rocks, the slopes of K‐Ar isochrons must be determined to reasonable precision in order to calculate reliable ages. Model simulations of possible isochrons give an indication of some requirements in order to define a precise rock age: Issues addressed here are: how many K‐Ar analyses should be made of rocks thought to have the same age; what range of K concentrations should these analyzed samples have; and what analytical uncertainty in K‐Ar measurements is desirable. Meteorite data also are used to determine the D/a2 diffusion parameters for Ar in plagioclase and pyroxene separates of several shergottites and nakhlites. These data indicate the required temperatures and times for heating similar Martian rocks in order to extract Ar. Quantitatively extracting radiogenic 40Ar could be difficult, and degassing cosmogenic Ar from mafic phases even more so. Considering all these factors, robotic K‐Ar dating of Martian rocks may be achievable, but will be challenging.
Layered ejecta craters and the early water/ice aquifer on Mars
Authors: OBERBECK Verne R.
Published: January 2010

Abstract— A model for emplacement of deposits of impact craters is presented that explains the size range of Martian layered ejecta craters between 5 km and 60 km in diameter in the low and middle latitudes. The impact model provides estimates of the water content of crater deposits relative to volatile content in the aquifer of Mars. These estimates together with the amount of water required to initiate fluid flow in terrestrial debris flows provide an estimate of 21% by volume (7.6 × 107km3) of water/ice that was stored between 0.27 and 2.5 km depth in the crust of Mars during Hesperian and Amazonian time. This would have been sufficient to supply the water for an ocean in the northern lowlands of Mars. The existence of fluidized craters smaller than 5 km diameter in some places on Mars suggests that volatiles were present locally at depths less than 0.27 km. Deposits of Martian craters may be ideal sites for searches for fossils of early organisms that may have existed in the water table if life originated on Mars.
Cosmogenic nuclides in the solar gas‐rich H3–6 chondrite breccia Frontier Mountain 90174
Authors: LEYA I. , WELTEN K. C. , NISHIIZUMI K. , CAFFEE M. W.
Published: January 2010

Abstract— We re‐evaluated the cosmic‐ray exposure history of the H3‐6 chondrite shower Frontier Mountain (FRO) 90174, which previously was reported to have a simple exposure history, an irradiation time of about 7 Ma, and a pre‐atmospheric radius of 80–100 cm (Welten et al. 2001). Here we measured the concentrations and isotopic compositions of He, Ne, and Ar in 8 aliquots of 6 additional fragments of this shower, and 10Be and 26Al in the stone fractions of seven fragments. The radionuclide concentrations in the stone fractions, combined with those in the metal fractions, confirm that all samples are fragments of the FRO 90174 shower. Four of the fragments contain solarwind‐implanted noble gases with a solar 20Ne/22Ne ratio of ˜12.0, indicating that FRO 90174 is a regolith breccia. The concentrations of solar gases and cosmogenic 21Ne in the samples analyzed by us and by Welten et al. (2001) overlap with those of the FRO H‐chondrites from the 1984 season, suggesting that many of these samples are also part of the large FRO 90174 chondrite shower. The cosmogenic 21Ne concentrations in FRO 90174 show no simple correlation with 10Be and 26Al activities. We found 21Ne excesses between 0.3‐1.1 × 10−8cm3STP/g in 6 of the 17 samples. Since excess 21Ne and trapped solar gases are not homogeneously distributed, i.e., we found in one fragment aliquots with and without excess 21Ne and solar 20Ne, we conclude that excess 21Ne is due to GCR irradiation of the regolith before compaction of the FRO 90174 object. Therefore, the chondrite shower FRO 90174 did not simply experience an exposure history, but some material was already irradiated at the surface of an asteroid leading to excess 21Ne. This excess 21Ne is correlated to implanted solar gases, clearly indicating that both processes occurred on the regolith.
Lunar meteorite LaPaz Icefield 04841: Petrology, texture, and impact‐shock effects of a low‐Ti mare basalt
Authors: HILL Eddy , TAYLOR Lawrence A. , FLOSS Christine , LIU Yang
Published: January 2010

Abstract— Found during the 2004 U.S. Antarctic Search for Meteorites season, LaPaz Icefield (LAP) 04841 represents an addition to the LaPaz lunar basalts suite and brings the total mass collected to 1.93 kg. The presence of FeNi grains, troilite, and the anorthositic composition of plagioclase are evidence for the lunar origin of this meteorite. Pyroxene and olivine Mn/Fe values plot along the trend set for lunar basalts. Analyses of chromite grains provide a V/(Al + Cr) ratio of 1.33 ± 13, translating to an fO2 one log unit below the IW buffer, in accordance with previous fO2 estimates for lunar basalts. Application of the Zr‐cooling speedometer, for ilmenite and ulvöspinel pairs, gives a cooling rate of 5.2 °C/day, matching previous estimates of cooling rates for the LaPaz lunar meteorites and Apollo mare basalts. Mineral modes and chemistries, as well as trace‐element patterns, provide compelling evidence for pairing of this meteorite to others in the LaPaz lunar basalt suite.
Application of a textural geospeedometer to the late‐stage magmatic history of MIL 03346
Authors: HAMMER Julia E.
Published: January 2010

Abstract— Dynamic crystallization experiments performed on Fe‐rich, Al‐poor basalt are employed as a textural calibration set to quantify the late‐stage igneous history of nakhlite Miller Range (MIL) 03346. The ratio of crystal‐melt surface area to volume typifying morphologically distinct populations of Ca‐pyroxene has been shown to vary as a strong function of cooling rate (Hammer 2006). Furthermore, a texture of phenocrysts surrounded by finer‐grained groundmass crystals arises by sequential nucleation events during constant‐rate cooling, but multiple populations nucleate only if the cooling rate is 72 °C h−1. Textural analysis of meteorite MIL 03346 reveals at least two distinct populations. The Ca‐pyroxene phenocryst and microphenocryst three dimensional (3D) aspect ratios are 112 ± 8.3 and 1530 ± 160 mm−1, respectively. By comparison with the calibration set, the range of cooling rates consistent with 3D aspect ratios of both populations in MIL 03346 is ˜20 °C h−1An additional experiment was performed approximating a conductive heat transfer profile in order to interpret and apply results of constant‐rate cooling experiments to the natural cooling of magma. Results suggest that the textures of constant‐rate experiments parallel the initial period of rapid cooling in natural magma. Initial cooling rates of ˜20 °C h−1in the lava hosting MIL 03346 occur in conductively solidifying lava at depths of˜0.4 m, constraining the minimum total thickness to 0.8 m. Crystal accumulation beginning in a subsurface reservoir and continuing after lava emplacement as an inflated pahoehoe sheet satisfies all textural constraints on the late‐stage igneous history of MIL 03346.
Puerto Lápice eucrite fall: Strewn field, physical description, probable fireball trajectory, and orbit
Authors: TRIGO‐RODRÍGUEZ Josep M. , BOROVIčKA Jiří , LLORCA Jordi , MADIEDO José M. , ZAMORANO Jaime , IZQUIERDO Jaime
Published: January 2010

Abstract— The fall of the Puerto Lápice eucrite occurred on May 10, 2007, at 17 h 57 m 30 ± 30 s UTC. Its daylight fireball was witnessed by hundreds of people from Spain, and produced a meteorite fall associated with a large strewn field of fragments. There were no direct pictures of the fireball, but several pictures of the fireball's train were taken from different locations in Spain. Additional theodolite calibrations of visual records were made in order to find the most probable fireball trajectory based on the available data. The shape of the meteorite strewn field was considered as well. Although the orbit of the Puerto Lápice meteoroid could not be computed due to the absence of velocity data, we assumed a likely range of geocentric velocities and computed a range of possible orbits. All solutions show that the body was in an Apollo‐type orbit, with low inclination and perihelion distance just below 1 astronomical unit (AU). This is the first case that an orbit can be discussed for an HED meteorite fall.
Sahara 03505 sulfide‐rich iron meteorite: Evidence for efficient segregation of sulfide‐rich metallic melt during high‐degree impact melting of an ordinary chondrite
Authors: D'ORAZIO Massimo , FOLCO Luigi , CHAUSSIDON Marc , ROCHETTE Pierre
Published: January 2010

Abstract— The Sahara 03505 meteorite is a 65 g sulfide‐rich iron found in an undisclosed locality of the Sahara. It consists of roughly equal volumetric proportion of polycrystalline troilite (crystal size 1.5–7.5 mm) enclosing cellular/dendritic metallic Fe‐Ni (width of the dendrite arms, ˜100 μm). The mineral assemblage is completed by sparse skeletal crystals of chromite, abundant droplets, 5–100 μm in size, of anhydrous Fe‐, Fe‐Na‐, and Fe‐Mn‐Mg‐Ca‐Na‐K‐phosphates, tiny crystals of schreibersite, and particles of metallic Cu.

The medium‐ to fine‐grained quench texture, and cooling modeling suggest that Sahara 03505 formed through crystallization of a sulfur‐rich metallic melt under rapid cooling conditions (1–4 °C s−1). The low troilite/metallic Fe‐Ni ratio (˜0.6 by weight) shows that this liquid was generated at much higher temperatures (<1300 °C) with respect to the FeS‐Fe,Ni cotectic liquids. Based on bulk chemistry and oxygen isotope composition of chromite, we propose that Sahara 03505 formed by extensive impact melting of an ordinary chondrite lithology, followed by the efficient segregation of the immiscible silicate and metallic liquids. The sulfur‐rich metallic liquid rapidly cooled either by radiation into space as a small lump, or by conduction to a chondrite country rock as a vein intruded into the walls of an impact crater.

Sahara 03505 belongs to a small group of sulfide‐rich iron meteorites which are characterized by medium‐ to fine‐grained quench textures and by bulk chemistry that is different from the other iron meteorite groups. We propose here to use the descriptive term “sulfide‐irons” for this meteorite group, by analogy with the stony‐irons.