D. S. Lauretta

The University of Arizona, Tucson, Arizona, United States

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Publications (219)266.19 Total impact

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    ABSTRACT: Bennu most likely came from a low albedo asteroid family in inner main belt.•We modeled the dynamical evolution of candidate source family members.•Semimajor axis distribution of ancient families reproduced with stochastic YORP model.•Probable Bennu source families are New Polana (70%, +8/−4%) and Eulalia (30%, +4/−8%).•Most low albedo km-sized NEOs on Earth-like orbits come from these two families.
    Icarus 02/2015; 247. · 2.84 Impact Factor
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    ABSTRACT: To better understand the formation conditions of ferromagnesian chondrules from the Renazzo-like carbonaceous (CR) chondrites, a systematic study of 210 chondrules from 15 CR chondrites was conducted. The texture and composition of silicate and opaque minerals from each observed FeO-rich (type II) chondrule, and a representative number of FeO-poor (type I) chondrules, were studied to build a substantial and self-consistent data set. The average abundances and standard deviations of Cr2O3 in FeO-rich olivine phenocrysts are consistent with previous work that the CR chondrites are among the least thermally altered samples from the early solar system. Type II chondrules from the CR chondrites formed under highly variable conditions (e.g., precursor composition, redox conditions, cooling rate), with each chondrule recording a distinct igneous history. The opaque minerals within type II chondrules are consistent with formation during chondrule melting and cooling, starting as S- and Ni-rich liquids at 988–1350 °C, then cooling to form monosulfide solid solution (mss) that crystallized around olivine/pyroxene phenocrysts. During cooling, Fe,Ni-metal crystallized from the S- and Ni-rich liquid, and upon further cooling mss decomposed into pentlandite and pyrrhotite, with pentlandite exsolving from mss at 400–600 °C. The composition, texture, and inferred formation temperature of pentlandite within chondrules studied here is inconsistent with formation via aqueous alteration. However, some opaque minerals (Fe,Ni-metal versus magnetite and panethite) present in type II chondrules are a proxy for the degree of whole-rock aqueous alteration. The texture and composition of sulfide-bearing opaque minerals in Graves Nunataks 06100 and Grosvenor Mountains 03116 suggest that they are the most thermally altered CR chondrites.
    Meteoritics & Planetary Science. 12/2014;
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    ABSTRACT: We review the results of an extensive campaign to determine the physical, geological, and dynamical properties of asteroid (101955) Bennu. This investigation provides information on the orbit, shape, mass, rotation state, radar response, photometric, spectroscopic, thermal, regolith, and environmental properties of Bennu. We combine these data with cosmochemical and dynamical models to develop a hypothetical timeline for Bennu's formation and evolution. We infer that Bennu is an ancient object that has witnessed over 4.5 Gyr of solar system history. Its chemistry and mineralogy were established within the first 10 Myr of the solar system. It likely originated as a discrete asteroid in the inner Main Belt approximately 0.7–2 Gyr ago as a fragment from the catastrophic disruption of a large (approximately 100-km), carbonaceous asteroid. It was delivered to near-Earth space via a combination of Yarkovsky-induced drift and interaction with giant-planet resonances. During its journey, YORP processes and planetary close encounters modified Bennu's spin state, potentially reshaping and resurfacing the asteroid. We also review work on Bennu's future dynamical evolution and constrain its ultimate fate. It is one of the most Potentially Hazardous Asteroids with an approximately 1-in-2700 chance of impacting the Earth in the late 22nd century. It will most likely end its dynamical life by falling into the Sun. The highest probability for a planetary impact is with Venus, followed by the Earth. There is a chance that Bennu will be ejected from the inner solar system after a close encounter with Jupiter. OSIRIS-REx will return samples from the surface of this intriguing asteroid in September 2023.
    Meteoritics & Planetary Science. 11/2014;
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    ABSTRACT: Concentrations of trace elements in four Late Pleistocene lake sediment sequences across Lithuania were studied using inductively coupled plasma-mass spectrometry (ICP-MS). Such elements as Cr, Cu, Eu, La, Ni, Zn, Zr, and platinum group elements were used for constraints. The studied sediments deposited during the time interval from Bølling to Allerød and to Younger Dryas. Material for sediments of the Dengtiltis and Krokšlys sequences was delivered from the same or very similar source. Geochemical features of the sediments are consistent with the presence of extraterrestrial material in at least two horizons separated by ∼2000 years, and resulted from two separate events. The younger horizon is detected in all studied sequences and corresponds to the age of ca. 11.0–11.5 ka BP. Its geochemical features are suggested to result from a local meteorite impact/bolide explosion tentatively related to the Velnio Duobės meteorite crater. The older horizon detected only for the Ūla-2 sequence corresponds to the age of ca. 13.5 ka BP and is due to the bolide airburst. There is also suggested meteoritic material in sediments dated as ca. 12.9 ka BP. The presence of volcanic materials related to the volcanic activity in the French Massif Central (a volcano of ca. 15.3 ka BP), and Laacher See volcano in Germany (12.88 ka BP) are suggested for some sedimentary layers of the studied sequences.
    Quaternary International 11/2014; · 2.13 Impact Factor
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    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.
    Meteoritics & Planetary Science. 11/2014;
  • Eve L. Berger, Lindsay P. Keller, Dante S. Lauretta
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    ABSTRACT: The low-temperature form of CuFe2S3, cubanite, has been identified in the CI chondrite and NASA Stardust mission collections. The presence of this mineral constrains the maximum temperature to 210 °C since the time of its formation. However, until now, the conditions under which cubanite forms were less well constrained. In order to refine the history of the time-varying, low-temperature fluids which existed on the CI-chondrite parent body and Comet 81P/Wild 2 (Wild 2), we synthesized cubanite. The experimental synthesis of this mineral was achieved, for the first time, under low-temperature aqueous conditions relevant to the CI-chondrite parent body. Using a variant of in situ hydrothermal recrystallization, cubanite formed in aqueous experiments starting with temperatures of 150 and 200 °C, pH approximately 9, and oxygen fugacities corresponding to the iron-magnetite buffer. The composition and structure of the cubanite were determined using electron microprobe and transmission electron microscopy techniques, respectively. The combined compositional, crystallographic, and experimental data allow us to place limits on the conditions under which the formation of cubanite is feasible, which in turn constrains the nature of the fluid phase on the CI-chondrite parent body and Wild 2 when cubanite was forming.
    Meteoritics & Planetary Science. 11/2014;
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    ABSTRACT: The Late Pleistocene climate oscillation (Younger Dryas, or YD, cooling) is connected predominantly to a sharp decrease of thermohaline circulation in the Atlantic Ocean, affecting the salinity in the areas where north Atlantic deep water is formed [1-3]. Recently, however, a hypothesis was proposed relating the YD cooling to an extraterrestrial (ET) bolide impact [4]. This hypothesis suggested that just before the onset of the YD cooling (12.9 ka), a large bolide (~4 km in the diameter) exploded over the North American Laurentide Ice Sheet. The consequences of such an event (“impact winter”) led to an abrupt climate change. If the impact occurred over North America, transportation of the impact cloud eastward by the dominating movement of the air masses could have delivered impactrelated material as far to the east as Europe (Fig. 1) [6]. Lake sediments, where undisturbed, proved to preserve reliable paleorecords on environmental, geochemical, and biotic changes [e.g., 7]. Continuing sedimentation in lakes of North-Central Europe started in Allerød and continued during the YD [3,8], covering a period of the suggested ET impact [4]. Therefore, geochemical fingerprints of the ET event can be preserved in paleolimnological records. There is not much data existing on the geochemistry of lake sediments in Europe in terms of the possible presence of the ET fingerprints. It is likely due to the fact that the event was very short and the layers carrying such fingerprints are very thin and, secondly, that nobody really searched for such geochemical anomalies. An increase of the concentration of elements which are in much higher abundances in meteorites than in terrestrial materials (“meteoritic” elements), especially in the platinum group elements (PGE), is accepted to be a clear indicator of a contribution of a meteoritic component to the terrestrial environment [9]. For the present study, the authors applied inductively coupled plasma-mass spectrometry (ICP-MS) in order to check the presence of geochemical anomalies (including the ETrelated anomalies) in Late Glacial sediments from a few lakes in Belgium, the Netherlands, Lithuania and NW Russia. All studied sedimentary sequences are dated either by radiocarbon, or thermoluminescence, or pollen methods, providing the time frames for a search for geochemical anomalies. Our study revealed that in spite of different local lithologies, some samples of Late Glacial lake sediments collected from the horizons corresponding to the age of ca. 12.9 ka display simultaneous enrichment in at least a few “meteoritic” elements (some PGE, Ni, Co, Cr). If enrichment in any of the “meteoritic” elements alone could be due to the influence of some terrestrial processes (e.g., changes in a source of sedimentary material; influence of biotic activity), simultaneous enrichment in a few “meteoritic” elements should raise suspicion about the potential presence of the ET material. Enrichment in “meteoritic” elements was observed only for very thin sedimentary layers in lakes of different parts of Europe. That points out that the event responsible for the enrichment was very short, which is consistent with the influence of the ET impact. Therefore, we suggest that elevated concentrations of “meteoritic” elements in the Late Pleistocene lake sediments are due to the presence of microparticles related to the ET event. Interestingly enough, some sedimentary horizons (ca. 12.9 ka) enriched in “meteoritic” elements also display enrichment in “volcanic” (such as REE, Zr, Hf, Sr, and Ti, i.e., elements common in products of volcanic eruptions) elements. We connect such a “double” enrichment with the presence of material from both the eruption of the Laacher See volcano (ca. 12.9 ka) [10] and a possible pre-YD ET event. Because of only patchy and weakly-pronounced occurrences of suggestively ET geochemical fingerprints in paleolimnological records of Europe, we hypothesize that the post-impact cloud did not completely blanket the sky over Europe; instead, the majority of the impact-related material deposited in North America, Greenland and North Atlantic. Therefore the influence of the pre-YD impact-related processes on the climate, if pronounced, should be restricted mostly by the Western Hemisphere, and be very limited in the Eastern Hemisphere.
    Paleolimnology of Northern Eurasia, Petrozavodsk; 09/2014
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    ABSTRACT: The Design Reference Asteroid (DRA) is a compilation of all that is known about the OSIRIS-REx mission target, asteroid (101955) Bennu. It contains our best knowledge of the properties of Bennu based on an extensive observational campaign that began shortly after its discovery, and has been used to inform mission plan development and flight system design. The DRA will also be compared with post-encounter science results to determine the accuracy of our Earth-based characterization efforts. The extensive observations of Bennu in 1999 has made it one of the best-characterized near-Earth asteroids. Many physical parameters are well determined, and span a number of categories: Orbital, Bulk, Rotational, Radar, Photometric, Spectroscopic, Thermal, Surface Analog, and Environment Properties. Some results described in the DRA have been published in peer-reviewed journals while others have been reviewed by OSIRIS-REx Science Team members and/or external reviewers. Some data, such as Surface Analog Properties, are based on our best knowledge of asteroid surfaces, in particular those of asteroids Eros and Itokawa. This public release of the OSIRIS-REx Design Reference Asteroid is a annotated version of the internal OSIRIS-REx document OREX-DOCS-04.00-00002, Rev 9 (accepted by the OSIRIS-REx project on 2014-April-14). The supplemental data products that accompany the official OSIRIS-REx version of the DRA are not included in this release. We are making this document available as a service to future mission planners in the hope that it will inform their efforts.
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    ABSTRACT: We report in situ O isotope and chemical compositions of magnetite and olivine in chondrules of the carbonaceous chondrites Watson-002 (anomalous CK3) and Asuka (A)-881595 (ungrouped C3). Magnetite in Watson-002 occurs as inclusion-free subhedral grains and rounded inclusion-bearing porous grains replacing Fe,Ni-metal. In A-881595, magnetite is almost entirely inclusion-free and coexists with Ni-rich sulfide and less abundant Ni-poor metal. Oxygen isotope compositions of chondrule olivine in both meteorites plot along carbonaceous chondrite anhydrous mineral (CCAM) line with a slope of approximately 1 and show a range of Δ17O values (from approximately −3 to −6‰). One chondrule from each sample was found to contain O isotopically heterogeneous olivine, probably relict grains. Oxygen isotope compositions of magnetite in A-881595 plot along a mass-dependent fractionation line with a slope of 0.5 and show a range of Δ17O values from −2.4‰ to −1.1‰. Oxygen isotope compositions of magnetite in Watson-002 cluster near the CCAM line and a Δ17O value of −4.0‰ to −2.9‰. These observations indicate that magnetite and chondrule olivine are in O isotope disequilibrium, and, therefore, not cogenetic. We infer that magnetite in CK chondrites formed by the oxidation of pre-existing metal grains by an aqueous fluid during parent body alteration, in agreement with previous studies. The differences in Δ17O values of magnetite between Watson-002 and A-881595 can be attributed to their different thermal histories: the former experienced a higher degree of thermal metamorphism that led to the O isotope exchange between magnetite and adjacent silicates.
    Meteoritics & Planetary Science. 08/2014;
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    ABSTRACT: Concentration and distribution of trace elements across the sequence of the Late Pleistocene sediments from the lake Medvedevskoye suggest the addition of materials other than those from a common source for the lake sediments of the region. The sediments of the lake Medvedevskoye carry some geochemical fingerprints which could be related the ET event that occurred at ca. 12.9 ka. Because such fingerprints are extremely subtle, the NW Russia can be considered to be the most remote eastern region of the extent of the Late Pleistocene airborne ET material. The sediments of the lake Medvedevskoye can also contain volcanic material from the eruption of the Laacher See (Germany) volcano and probably from other Late Pleistocene volcanoes of Western Europe and/or Iceland.
    Doklady Earth Sciences 07/2014; 457(1):819-823. · 0.39 Impact Factor
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    ABSTRACT: 819 The Late Pleistocene climate oscillation known as Younger Dryas (YD) cooling event is connected pree dominantly to a sharp decrease of thermohaline circuu lation in the Atlantic Ocean affecting the salinity in the areas where north Atlantic deep water is formed [1–3]. Recently, a hypothesis was proposed relating the YD cooling to an extraterrestrial (ET) bolide impact [4]. This hypothesis suggested that just before the onset of the YD cooling, 12.9 ka, a large bolide (up to 4 km in the diameter) exploded over the North American Lauu rentide Ice Sheet, The consequences of such a cataa strophic event (soocalled "meteorite impact winter") might have led to an abrupt climate change. This sugg gestion resulted in a widespread discussion, which has yet to result in a decisive conclusion. Detailed descripp tions of arguments for and against the impact hypothh esis are given in [5]. If the impact occurred over North America, transs portation of the impacttrelated microparticles eastt ward by the dominating move of the air masses from west to east could have delivered such particles as far to the east as Western and East Europe [6], Some studies showed that the material that could be related to metee orite impact is present in the Late Pleistocene sedii ments of Western Europe [5]. Subaquatic sediments deposited in small basins may capture and preserve airborne particles. Authors proposed to apply modern geochemical analytical methods (inductively coupled plasmaamass spectrometry; ICPPMS) in order to check the presence of geochemical anomalies (in parr ticular, ETTrelated) in Late Glacial lake sediments of East Europe. Many lakes of NW Russia are known to exist as long as from 14–15 ka [3], i.e., continuing sedimentaa tions started there before time of the suggested metee orite impact. Therefore, geochemical fingerprints of such an event could be preserved in such lake sedii ments. In a search for fingerprints of the ET impact, we chose to study Late Pleistocene sediments of the Lake Medvedevskoye (60°14′ N, 29°54′ E, 102.2 m a.s.l.) of the Karelian Isthmus of NW Russia (Fig. 1). Because of its elevation and small watershed, this small shallow lake (0.44 km 2 surface, 0.55 km width, 1.18 km length, ~4 m the maximum depth), first of all, was never flooded by water of bigger water bodies after deglaciation of the Karelian Isthmus, and, second, is
    Doklady Earth Sciences 07/2014; 457(457):819-823. · 0.50 Impact Factor
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    Asteroids, Comets, Meteors 2014, Helsinki, Finland; 06/2014
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    ABSTRACT: Near-Earth Asteroids (NEAs) have garnered ever increasing attention over the past few years due to the insights they offer into Solar System formation and evolution, the potential hazard they pose, and their accessibility for both robotic and human spaceflight missions. Among the NEAs, carbonaceous asteroids hold particular interest because they may contain clues to how the Earth got its supplies of water and organic materials, and because none has yet been studied in detail by spacecraft. (101955) Bennu is special among NEAs in that it will not only be visited by a spacecraft, but the OSIRIS-REx mission will also return a sample of Bennu’s regolith to Earth for detailed laboratory study. This paper presents analysis of thermal infrared photometry and spectroscopy that test the hypotheses that Bennu is carbonaceous and that its surface is covered in fine-grained (sub-cm) regolith. The Spitzer Space Telescope observed Bennu in 2007, using the Infrared Spectrograph (IRS) to obtain spectra over the wavelength range 5.2–38 μm and images at 16 and 22 μm at 10 different longitudes, as well as the Infrared Array Camera (IRAC) to image Bennu at 3.6, 4.5, 5.8, and 8.0 μm, also at 10 different longitudes. Thermophysical analysis, assuming a spherical body with the known rotation period and spin-pole orientation, returns an effective diameter of 484 ± 10 m, in agreement with the effective diameter calculated from the radar shape model at the orientation of the Spitzer observations (492 ± 20 m, Nolan, M.C., Magri, C., Howell, E.S., Benner, L.A.M., Giorgini, J.D., Hergenrother, C.W., Hudson, R.S., Lauretta, D.S., Margo, J.-L., Ostro, S.J., Scheeres, D.J. [2013]. Icarus 226, 629–640) and a visible geometric albedo of 0.046 ± 0.005 (using Hv = 20.51, Hergenrother, C.W. et al. [2013]. Icarus 226, 663–670). Including the radar shape model in the thermal analysis, and taking surface roughness into account, yields a disk-averaged thermal inertia of 310 ± 70 J m−2 K−1 s−1/2, which is significantly lower than several other NEAs of comparable size. There may be a small variation of thermal inertia with rotational phase (±60 J m−2 K−1 s−1/2). The spectral analysis is inconclusive in terms of surface mineralogy; the emissivity spectra have a relatively low signal-to-noise ratio and no spectral features are detected. The thermal inertia indicates average regolith grain size on the scale of several millimeters to about a centimeter. This moderate grain size is also consistent with low spectral contrast in the 7.5–20 μm spectral range. If real, the rotational variation in thermal inertia would be consistent with a change in average grain size of only about a millimeter. The thermophysical properties of Bennu’s surface appear to be fairly homogeneous longitudinally. A search for a dust coma failed to detect any extended emission, putting an upper limit of about 106 g of dust within 4750 km of Bennu. Three common methodologies for thermal modeling are compared, and some issues to be aware of when interpreting the results of such models are discussed. We predict that the OSIRIS-REx spacecraft will find a low albedo surface with abundant sub-cm sized grains, fairly evenly distributed in longitude.
    Icarus 05/2014; 234:17–35. · 2.84 Impact Factor
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    ABSTRACT: An environmental simulation chamber was used to measure the emissivities of a selection of ground meteorites under isothermal and asteroid-like conditions.
    02/2014;
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    ABSTRACT: NASA's OSIRIS-REx mission will return samples of asteroid Bennu in 2023. We review our approach to unraveling the history of Bennu by returned sample analyses.
    02/2014;
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    ABSTRACT: Although rare in meteorites, chalcopyrite (CuFeS2) is seen in R chondrites. Thermodynamics predict it formed in aqueous conditions or by melt crystallization.
    02/2014;
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    ABSTRACT: The target asteroid of the OSIRIS-REx asteroid sample return mission, (101955) Bennu (formerly 1999 RQ$_{36}$), is a half-kilometer near-Earth asteroid with an extraordinarily well constrained orbit. An extensive data set of optical astrometry from 1999--2013 and high-quality radar delay measurements to Bennu in 1999, 2005, and 2011 reveal the action of the Yarkovsky effect, with a mean semimajor axis drift rate $da/dt = (-19.0 \pm 0.1)\times 10^{-4}$ au/Myr or $284\pm 1.5\;\rm{m/yr}$. The accuracy of this result depends critically on the fidelity of the observational and dynamical model. As an example, neglecting the relativistic perturbations of the Earth during close approaches affects the orbit with $3\sigma$ significance in $da/dt$. The orbital deviations from purely gravitational dynamics allow us to deduce the acceleration of the Yarkovsky effect, while the known physical characterization of Bennu allows us to independently model the force due to thermal emissions. The combination of these two analyses yields a bulk density of $\rho = 1260\pm70\,\rm{kg/m^3}$, which indicates a macroporosity in the range $40\pm10$% for the bulk densities of likely analog meteorites, suggesting a rubble-pile internal structure. The associated mass estimate is $(7.8\pm0.9)\times 10^{10}\, \rm{kg}$ and $GM = 5.2\pm0.6\,\rm{m^3/s^2}$. Bennu's Earth close approaches are deterministic over the interval 1654--2135, beyond which the predictions are statistical in nature. In particular, the 2135 close approach is likely within the lunar distance and leads to strong scattering and therefore numerous potential impacts in subsequent years, from 2175--2196. The highest individual impact probability is $9.5\times 10^{-5}$ in 2196, and the cumulative impact probability is $3.7\times 10^{-4}$, leading to a cumulative Palermo Scale of -1.70.
    Icarus 02/2014; · 2.84 Impact Factor
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    ABSTRACT: A fragment of the Chelyabinsk meteorite (LL5, S4, WG0) represented by an impact melt breccia is studied for chemical composition of metals and sulfides.
    01/2014;
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    ABSTRACT: The primitive achondrites provide a window into the initial melting of asteroids in the early solar system. The brachinites are olivine-dominated meteorites with a recrystallized texture that we and others interpret as evidence of partial melting and melt removal on the brachinite parent body. We present a petrologic, thermodynamic and experimental study of the brachinites to evaluate the conditions under which they formed and test our hypothesis that the precursor material to the brachinites was FeO-rich compared to the precursors of other primitive achondrites. Petrologic analysis of six brachinites (Brachina, Allan Hills (ALH) 84025, Hughes 026, Elephant Moraine (EET) 99402, Northwest Africa (NWA) 3151, and NWA 4969) and one brachinite-like achondrite (NWA 5400) shows that they are meteorites with recrystallized texture that are enriched in olivine (⩾80 vol.%) and depleted in other minerals with respect to a chondritic mineralogy. Silicates in the brachinites are FeO-rich (Fa32–36). Brachinite-like achondrite Northwest Africa 5400 is similar in mineralogy and texture to the brachinites but with a slightly lower FeO-content (Fa30). Thermodynamic calculations yield equilibration temperatures above the Fe,Ni–FeS cotectic temperature (˜950 °C) for all meteorites studied here and temperatures above the silicate eutectic (˜1050 °C) for all but two. Brachina formed at an fO2 of ˜IW, and the other brachinites and NWA 5400 formed at ˜IW ‑ 1. All the meteorites show great evidence of formation by partial melting having approximately chondritic to depleted chondritic mineralogies, equilibrated mineral compositions, and recrystallized textures, and having reached temperatures above that required for melt generation. In an attempt to simulate the formation of the brachinite meteorites, we performed one-atmosphere, gas-mixing partial melting experiments of R4 chondrite LaPaz Ice Field 03639. Experiments at 1250 °C and an oxygen fugacity of IW ‑ 1 produce residual phases that are within the mineralogy and mineral compositions of the brachinites. These experiments provide further evidence for the formation of brachinites as a result of partial melting of a chondritic precursor similar in mineralogy and mineral compositions to the R chondrites.
    Geochimica et Cosmochimica Acta 12/2013; · 4.25 Impact Factor
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    ABSTRACT: We present the three-dimensional shape of near-Earth asteroid (101955) Bennu (provisional designation 1999 RQ36) based on radar images and optical lightcurves (Nolan et al., 2013). Bennu was observed both in 1999 at its discovery apparition, and in 2005 using the 12.6-cm radar at the Arecibo Observatory and the 3.5-cm radar at the Goldstone tracking station. Data obtained in both apparitions were used to construct a shape model of this object. Observations were also obtained at many other wavelengths to characterize this object, some of which were used to further constrain the shape modeling (Clark et al., 2011; Hergenrother et al., 2013; Krugly et al., 1999).
    NASA Planetary Data System. 09/2013;

Publication Stats

1k Citations
266.19 Total Impact Points

Institutions

  • 2002–2015
    • The University of Arizona
      • • Department of Planetary Sciences
      • • Southwest Center
      Tucson, Arizona, United States
  • 1999–2012
    • Arizona State University
      • Department of Chemistry and Biochemistry
      Mesa, AZ, United States
  • 1997–2010
    • Washington University in St. Louis
      • Department of Earth and Planetary Sciences
      Saint Louis, MO, United States
  • 2006
    • Sierra Tucson
      Tucson, Arizona, United States
  • 2005
    • NASA
      Washington, West Virginia, United States