bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geochemistry of 4 Vesta based on HED meteorites: Prospective study for interpretation of gamma ray and neutron spectra for the Dawn mission
Authors: USUI Tomohiro , McSween Harry Y. 
Published: January 2010

Abstract— Asteroid 4 Vesta, believed to be the parent body of the howardite, eucrite, and diogenite (HED) meteorites, will be investigated by the Dawn orbiting spacecraft. Dawn carries a gamma ray and neutron detector (GRaND) that will measure and map some major‐ and trace‐element abundances. Drawing on HED geochemistry, we propose a mixing model that uses element ratios appropriate for the interpretation of GRaND data.Because the spatial resolution of GRaND is relatively coarse, the analyzed chemical compositions on the surface of Vesta will likely reflect mixing of three endmember components: diogenite, cumulate eucrite, and basaltic eucrite. Reliability of the mixing model is statistically investigated based on published whole‐rock data for HED meteorites. We demonstrate that the mixing model can accurately estimate the abundances of all the GRaND‐analyzed major elements, as well as of minor elements (Na, Cr, and Mn) not analyzed by this instrument. We also show how a similar mixing model can determine the modal abundance of olivine, and we compare estimated and normative olivine data for olivine‐bearing diogenites. By linking the compositions of well‐analyzed HED meteorites with elemental mapping data from GRaND, this study may help constrain the geological context for HED meteorites and provide new insight into the magmatic evolution of Vesta.
Stardust—An artificial, low‐velocity “meteor” fall and recovery: 15 January 2006
Authors: ReVelle D. O. , Edwards W. N. 
Published: January 2010

Abstract— On January 15, 2006, Stardust, a man‐made space capsule, plummeted to Earth for a soft landing after spending seven years in space. Since the expected initial speed of the body was about 12.9 km/s, a four‐element ground‐based infrasound array was deployed to Wendover, Nevada, USA, to measure the hypersonic booms from the re‐entry. At a distance of ∼33 km from the nominal trajectory, we easily recorded the weak acoustic arrivals and their continued rumbling after the main hypersonic boom arrival. In this paper, we report on subsequent analyses of these data, including an assessment of the expected entry characteristics (dynamics, energetics, ablation and panchromatic luminosity, etc.) on the basis of a bolide/meteor/fireball entry model that was specifically adapted for modeling a re‐entering man‐made object.Throughout the infrasonic data analyses, we compared our results for Stardust to those previously obtained for Genesis. From the associated entry parameters, we were also able to compute the kinetic energy density conservation properties for the propagating line source blast wave and compared the inviscid theoretical predictions against observed ground‐based infrasound amplitude and wave period data as a function of range. Finally, we made a top‐down bottom‐up assessment of the line source wave normals propagating downward into the complex temperature/sound speed and horizontal wind speed environment during January 15, 2006. This assessment proved to be generally consistent with the signal processing analysis and with the observed time delay between the known Stardust entry and the time of observations of infrasound signals, and so forth.
El'gygytgyn impact crater, Russia: Structure, tectonics, and morphology
Authors: Gurov Eugene P. , Koeberl Christian , Yamnichenko Anatoly 
Published: January 2010

Abstract— The 3.6 Myr old El'gygytgyn impact crater is located in central Chukotka, northeastern Russia. The crater is a well‐preserved impact structure with an inner basin about 15 km in diameter, surrounded by an uplifted rim about 18 km in diameter. The flat floor of the crater is in part occupied by Lake El'gygytgyn, 12 km in diameter, and surrounding terraces. The average profile of the rim is asymmetric, with a steep inner wall and a gentle outer flank. The rim height is about 180 m above the lake level and 140 m above the surrounding area. An outer ring feature, on average 14 m high, occurs at about 1.75 crater radii from the center of the structure.El'gygytgyn crater is surrounded by a complex network of faults. The density of the faults decreases from the bottom of the rim to the rim crest and outside the crater to a distance of about 2.7 crater radii. Lake El'gygytgyn is surrounded by a number of lacustrine terraces. Only minor remnants are preserved of the highest terraces, 80 and 60 m above the present‐day lake level. The widest of the terraces is 40 m above the current lake level and surrounds the lake on the west and northwest sides. The only outlet of the lake is the Enmivaam River, which cuts through the crater rim in the southeast. In terms of structure, El'gygytgyn is well preserved and displays some interesting, but not well understood, features (e.g., an outer ring), similar to those observed at a few other impact structures.
Selective release of D and 13C from insoluble organic matter of the Murchison meteorite by impact shock
Authors: Mimura Koichi , Okamoto Michioki , Sugitani Kenichiro , Hashimoto Shigemasa 
Published: January 2010

Abstract— We performed shock‐recovery experiments on insoluble organic matter (IOM) purified from the Murchison meteorite, and determined the abundances and isotope ratios of hydrogen and carbon in the shocked IOM sample. We also performed shock experiments on type III kerogen and compared the results of these experiments with the experimental results regarding IOM.The shock selectively released D and 13C from the IOM, while it preferably released H and 12C from the kerogen. The release of these elements from IOM cannot be explained in terms of the isotope effect, whereas their release from kerogen can be explained by this effect. The selective release of heavier isotopes from IOM would be due to its structure, in which D and 13C‐enriched parts are present as an inhomogeneity and are weakly attached to the main network. Shock gave rise to a high release of D even at a lower degree of dehydrogenation compared with the stepwise heating of IOM. This effective release of D is probably an inherent result of shock, in which a dynamic high‐pressure and high‐temperature condition prevails. Thus, shock would effectively control the hydrogen isotope behavior of extraterrestrial organic matter during the evolution of the solar nebula.
Drill core LB‐08A, Bosumtwi impact structure, Ghana: Petrographic and shock metamorphic studies of material from the central uplift
Authors: FERRIÈRE Ludovic , KOEBERL Christian , REIMOLD Wolf Uwe 
Published: January 2010

Abstract— During a recent drilling project sponsored by the International Continental Scientific Drilling Progam (ICDP), two boreholes (LB‐07A and LB‐08A) were drilled into the crater fill of the Bosumtwi impact structure and the underlying basement, into the deep crater moat and the outer flank of the central uplift, respectively. The Bosumtwi impact structure in Ghana (West Africa), which is 10.5 km in diameter and 1.07 Myr old, is largely filled by Lake Bosumtwi.Here we present the lithostratigraphy of drill core LB‐08A (recovered between 235.6 and 451.33 m depth below lake level) as well as the first mineralogical and petrographic observations of samples from this core. This drill core consists of approximately 25 m of polymict, clast‐supported lithic breccia intercalated with suevite, which overlies fractured/brecciated metasediment that displays a large variation in lithology and grain size. The lithologies present in the central uplift are metasediments composed dominantly of fine‐grained to gritty meta‐graywacke, phyllite, and slate, as well as suevite and polymict lithic impact breccia. The suevites, principally present between 235.6 and 240.5 m and between 257.6 and 262.2 m, display a fine‐grained fragmental matrix (about 39 to 45 vol%) and a variety of lithic and mineral clasts that include meta‐graywacke, phyllite, slate, quartzite, carbon‐rich organic shale, and calcite, as well as melt particles, fractured quartz, unshocked quartz, unshocked feldspar, quartz with planar deformation features (PDFs), diaplectic quartz glass, mica, epidote, sphene, and opaque minerals). The crater‐fill suevite contains calcite clasts but no granite clasts, in contrast to suevite from outside the northern crater rim.The presence of melt particles in suevite samples from the uppermost 25 meters of the core and in suevite dikelets in the basement is an indicator of shock pressures exceeding 45 GPa. Quartz grains present in suevite and polymict lithic impact breccia abundantly display 1 to (rarely) 4 sets of PDFs per grain. The shock pressures recorded by the PDFs in quartz grains in the polymict impact breccia range from 10 to ∼30 GPa. We also observed a decrease of the abundance of shocked quartz grains in the brecciated basement with increasing depth. Meta‐graywacke samples from the basement are heterogeneously shocked, with shock pressures locally ranging up to 25–30 GPa. Suevites from this borehole show a lower proportion of melt particles and diaplectic quartz glass than suevites from outside the northern crater rim (fallback impact breccia), as well as a lack of ballen quartz, which is present in the external breccias. Similar variations of melt‐particle abundance and shock‐metamorphic grade between impact‐breccia deposits within the crater and fallout impact breccia outside the crater have been observed at the Ries impact structure, Germany.
Drill core LB‐08A, Bosumtwi impact structure, Ghana: Geochemistry of fallback breccia and basement samples from the central uplift
Authors: FERRIÈRE Ludovic , KOEBERL Christian , REIMOLD Wolf Uwe , MADER Dieter 
Published: January 2010

Abstract— The 1.07 Myr old Bosumtwi impact structure in Ghana (West Africa), which measures 10.5 km in diameter and is largely filled by Lake Bosumtwi, is associated with one of four currently known tektite strewn fields. Two boreholes were drilled to acquire hard‐rock samples of the deep crater moat and from the flank of the central uplift (LB‐07A and LB‐08A, respectively) during a recent ICDP‐sponsored drilling project.Here we present results of major and trace element analysis of 112 samples from drill core LB‐08A. This core, which was recovered between 235.6 and 451.33 m depth below lake level, contains polymict lithic breccia intercalated with suevite, which overlies fractured/brecciated metasediment. The basement is dominated by meta‐graywacke (from fine‐grained to gritty), but also includes some phyllite and slate, as well as suevite dikelets and a few units of a distinct light greenish gray, medium‐grained meta‐graywacke.Most of the variations of the major and trace element abundances in the different lithologies result from the initial compositional variations of the various target rock types, as well as from aqueous alteration processes, which have undeniably affected the different rocks.Suevite from core LB‐08A (fallback suevite) and fallout suevite samples (from outside the northern crater rim) display some differences in major (mainly in MgO, CaO, and Na2O contents) and minor (mainly Cr and Ni) element abundances that could be related to the higher degree of alteration of fallback suevites, but also result from differences in the clast populations of the two suevite populations. For example, granite clasts are present in fallout suevite but not in fallback breccia, and calcite clasts are present in fallback breccia and not in fallout suevite. Chondrite‐normalized rare earth element abundance patterns for polymict impact breccia and basement samples are very similar to each other.Siderophile element contents in the impact breccias are not significantly different from those of the metasediments, or compared to target rocks from outside the crater rim. So far, no evidence for a meteoritic component has been detected in polymict impact breccias during this study, in agreement with previous work.
The Lake Bosumtwi meteorite impact structure, Ghana—A magnetic image from a third observational level
Authors: UGALDE Hernan , MORRIS William A. , CLARK Christina , MILES Brett , MILKEREIT Bernd 
Published: January 2010

Abstract— The Bosumtwi impact structure in Ghana is the youngest and best‐preserved medium‐sized impact structure on Earth, and because of the vast amount of prior geophysical and geological data gathered in the area, it constitutes a great natural laboratory to try to develop new geophysical interpretation and modeling techniques.During the 2004 International Continental Scientific Drilling Program (ICDP) drilling campaign at Lake Bosumtwi, we made magnetic field observations at 162 stations around the lake. This study differs from all previous magnetic surveys at Bosumtwi, which only measured the scalar portion of the Earth's magnetic field, in that we measured the full magnetic vector at each station. Acquisition of the full magnetic vector was made possible by innovative use of a borehole deviation probe, which uses a magnetic sensor for absolute orientation reference. Estimates of the magnetic vector orientation and magnitude at each observation station were derived from a series of measurements collected at 50 cm spacing over a depth range of 25 m.In this study, we report a comparison between the scalar total field intensity derived from this new survey approach with the other two previously acquired marine and airborne magnetic data sets. The scalar total magnetic intensity (TMI) computed from the vector data set compares in close agreement with the other two data sets. Some discrepancies between the data sets can be explained by differences in the distances between the sensor and the magnetic sources for the various surveys. The highlight of this study is that we demonstrate that is possible to acquire at least partial vector data with readily available instrumentation.
Characterization of carbon‐ and nitrogen‐rich particle fragments captured from comet 81P/Wild 2
Authors: Gallien J.‐P. , Khodja H. , Herzog G. F. , Taylor S. , Koepsell E. , Daghlian C. P. , Flynn G. J. , Sitnitsky I. , Lanzirotti A. , Sutton S. R. , Keller L. P. 
Published: January 2010

Abstract—We studied three Stardust fragments with infrared spectroscopy to characterize organic matter; with synchrotron‐induced X‐ray fluorescence to determine Fe contents and certain elemental ratios to iron; with scanning electron microscopy (SEM) to image sample morphology and to detect semiquantitatively Mg, Al, Si, Ca, and Fe; and with nuclear reaction analysis (NRA) to measure C, N, O, and Si. A fourth fragment was analyzed by SEM only.Fragment C2054,0,35,21 from track 35 (hereafter C21) is extremely rich in C and contains appreciable concentrations of Mg, Al, and Ca, but little Fe. Fragments C2054,0,35,23 (C23), C2044,0,41 (C41), and C2054,0,35,51,0 (C51), from tracks 35, 41, and 35, respectively, consist largely but not exclusively of aerogel. C23 contains Mg and finely dispersed S, but little Al, Ca or Fe. Pooled CI‐normalized elemental ratios for C21, C23, and C41 are as follows: Ti/Fe, 5.0; Cr/Fe, 0.84; Mn/Fe, 0.97; Ni/Fe, 2.4; and Zn/Fe, 31. The enrichments in Ti and Zn may be related to the presence of aerogel.Minimum weight percentages of C and N estimated without correcting for the presence of aerogel are 30 and 0.7 for C21; 2.8 and 0.2 for C23; 1.2 and 0.14 for C41. After corrections for the presence of aerogel containing 1.4 wt% C and 0.02 wt% N, the corresponding results are 37 and 0.85 for C21; and 10 and 1 for C23; and ˜1 and ˜1, for C41 (The results for C41 have large uncertainties). These weight percentages are larger than or comparable to values for carbonaceous meteorites. C/N atomic ratios without/without aerogel corrections are 51/51 for C21, 17/11 for C23, and 10/˜1 for C41. Within the uncertainties these values are within the range for carbonaceous meteorites.
Frontier Mountain meteorite specimens of the acapulcoite‐lodranite clan: Petrography, pairing, and parent‐rock lithology of an unusual intrusive rock
Authors: BURRONI Alessandro , FOLCO Luigi 
Published: January 2010

Abstract— In this paper we reconstruct the heterogeneous lithology of an unusual intrusive rock from the acapulcoite‐lodranite (AL) parent asteroid on the basis of the petrographic analysis of 5 small (<8.3 g) meteorite specimens from the Frontier Mountain ice field (Antarctica). Although these individual specimens may not be representative of the parent‐rock lithology due to their relatively large grain size, by putting together evidence from various thin sections and literature data we conclude that Frontier Mountain (FRO) 90011, FRO 93001, FRO 99030, and FRO 03001 are paired fragments of a medium‐ to coarse‐grained igneous rock which intrudes a lodranite and entrains xenoliths. The igneous matrix is composed of enstatite (Fs13.3 ± 0.4 Wo3.1 ± 0.2), Cr‐rich augite (Fs6.1 ± 0.7 Wo42.3 ± 0.9), and oligoclase (Ab80.5 ± 3.3 Or3.2 ± 0.6). The lodranitic xenoliths show a fine‐grained (average grain size 488 ± 201 μm) granoblastic texture and consist of olivine Fa9.5 ± 0.4 and Fe,Ni metal and minor amounts of enstatite Fs12.7 ± 0.4 Wo1.8 ± 0.1, troilite, chromite, schreibersite, and Ca‐phosphates. Crystals of the igneous matrix and lodranitic xenoliths are devoid of shock features down to the scanning electron microscope scale. From a petrogenetic point of view, the lack of shock evidence in the lodranitic xenoliths of all the studied samples favors the magmatic rather than the impact melting origin of this rock.FRO 95029 is an acapulcoite and represents a separate fall from the AL parent asteroid, i.e., it is not a different clast entrained by the FRO 90011, FRO 93001, FRO 99030, and FRO 03001 melt, as in genomict breccias common in the meteoritic record. The specimen‐to‐meteorite ratio for the AL meteorites so far found at Frontier Mountain is thus 2.5.
Ulasitai: A new iron meteorite likely paired with Armanty (IIIE)
Authors: XU Lin , MIAO Bingkui , LIN Yangting , OUYANG Ziyuan 
Published: January 2010

Abstract— The Ulasitai iron was recently found about 130 km southeast to the find site of the Armanty (Xinjiang, IIIE) meteorite. It is a coarse octahedrite with a kamacite bandwidth of 1.2 ± 0.2 (0.9–1.8) mm. Plessite is abundant, as is taenite, kamacite, cohenite, and schreibersite with various microstructures. Schreibersite is Ni‐rich (30.5–55.5 wt%) in plessite or coexisting with troilite and daubreelite, in comparison with the coarse laths (20.6–21.2 wt%) between the Widmanstätten pattern plates. The correlation between the center Ni content and the half bandwidth of taenite suggest a cooling rate of ˜20 °C/Myr based on simulations. The petrography and mineral chemistry of Ulasitai are similar to Armanty.The bulk samples of Ulasitai were measured, together with Armanty, Nandan (IIICD), and Mundrabilla (IIICD), by inductively coupled plasma atomic emission spectrometry (ICP‐AES) and mass spectrometry (ICP‐MS). The results agree with literature data of the same meteorites, and our analyses of four samples of Armanty (L1, L12, L16, L17) confirm a homogeneous composition (Wasson et al. 1988). The bulk composition of Ulasitai is identical to that of Armanty, both plotting within the IIIE field. We classify Ulasitai as a new IIIE iron and suggest that it pairs with Armanty.
Noble gas content and isotope abundances in phases of the Saint‐Aubin (UNGR) iron meteorite
Authors: NISHIMURA Chikako , MATSUDA Jun‐ichi , KURAT Gero 
Published: January 2010

Abstract— We analyzed the noble gas isotopes in the Fe‐Ni metal and inclusions of the Saint‐Aubin iron meteorite, utilizing the stepwise heating technique to separate the various components of noble gases.The light noble gases in all samples are mostly cosmogenic, with some admixture from the terrestrial atmosphere. Total abundances of noble gases in metal are one of the lowest found so far in iron meteorites and the 4He/21Ne ratio is as high as 503, suggesting that the Saint‐Aubin iron meteorite was derived from a very large meteoroid in space. The exposure ages obtained from cosmogenic 3He were 9–16 Ma.Saint‐Aubin is very peculiar because it contains very large chromite crystals, which—like the metal—contain only cosmogenic and atmospheric noble gases. The noble gases in all the samples do not reveal any primordial components. The only exception is the 1000 °C fraction of schreibersite which contained about 5% of the Xe‐HL component. The Xe‐Q and the El Taco Xe components were not found and only the Xe‐HL is present in this fraction. Some presolar diamond, the only carrier for the HL component known today, must have been available during growth of the schreibersite. However, it is also possible that this excess is due to the addition of cosmogenic and fission components. In this case, all the primordial components are masked (or lost) by the later events such as cosmic‐ray irradiation, heating, and radioactive decay.
Ca,Al‐rich inclusions in Rumuruti (R) chondrites
Authors: ROUT Surya Snata , BISCHOFF Addi 
Published: January 2010

Abstract— Rumuruti chondrites (R chondrites) constitute a well‐characterized chondrite group different from carbonaceous, ordinary, and enstatite chondrites. Many of these meteorites are breccias containing primitive type 3 fragments as well as fragments of higher petrologic type. Ca,Al‐rich inclusions (CAIs) occur within all lithologies. Here, we present the results of our search for and analysis of Al‐rich objects in Rumuruti chondrites.We studied 20 R chondrites and found 126 Ca,Al‐rich objects (101 CAIs, 19 Al‐rich chondrules, and 6 spinel‐rich fragments). Based on mineralogical characterization and analysis by SEM and electron microprobe, the inclusions can be grouped into six different types: (1) simple concentric spinel‐rich inclusions (42), (2) fassaite‐rich spherules, (3) complex spinel‐rich CAIs (53), (4) complex diopside‐rich inclusions, (5) Al‐rich chondrules, and (6) Al‐rich (spinel‐rich) fragments. The simple concentric and complex spinel‐rich CAIs have abundant spinel and, based on the presence or absence of different major phases (fassaite, hibonite, Na,Al‐(Cl)‐rich alteration products), can be subdivided into several subgroups.Although there are some similarities between CAIs from R chondrites and inclusions from other chondrite groups with respect to their mineral assemblages, abundance, and size, the overall assemblage of CAIs is distinct to the R‐chondrite group. Some Ca,Al‐rich inclusions appear to be primitive (e.g., low FeO‐contents in spinel, low abundances of Na,Al‐(Cl)‐rich alteration products; abundant perovskite), whereas others were highly altered by nebular and/or parent body processes (e.g., high concentrations of FeO and ZnO in spinel, ilmenite instead of perovskite, abundant Na,Al‐(Cl)‐rich alteration products). There is complete absence of grossite and melilite, which are common in CAIs from most other groups. CAIs from equilibrated R‐chondrite lithologies have abundant secondary Ab‐rich plagioclase (oligoclase) and differ from those in unequilibrated type 3 lithologies which have nepheline and sodalite instead.