D. S. Lauretta

The University of Arizona, Tucson, Arizona, United States

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Publications (180)204.08 Total impact

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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;
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    01/2014;
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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 01/2014; 234:17–35. · 3.16 Impact Factor
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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; · 3.88 Impact Factor
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    ABSTRACT: We determine the three-dimensional shape of near-Earth Asteroid (101955) Bennu based on radar images and optical lightcurves. 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. The lightcurve data, along with an initial determination of the rotation period derived from them, simplified and improved the shape modeling.
    Icarus 09/2013; 226(1):629-640. · 3.16 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;
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    ABSTRACT: IN SEARCH FOR FINGERPRINTS OF A POSSIBLE ET IMPACT: HR-ICP-MS STUDY OF LATE PLEISTOCENE LAKE SEDIMENTS OF LITHUANIA Alexandre V. Andronikov, Eugenija Rudnickaitė, Dante S. Lauretta, Irina E. Andronikova, Donatas Kaminskas, Petras Šinkūnas, Monika Melešytė Climate oscillation in the Northern Hemisphere (the Younger Dryas; YD) which occurred between ca. 12.9K cal yr BP and ca. 11.7K cal yr BP (Peteet, 1995; Alley, 2000; Björck, 2007; Lowe et al., 2008; Murton et al., 2010) is connected predominantly to a sharp decrease of thermohaline circulation in the Atlantic Ocean triggered by a sudden fresh-water release to the North Atlantic (Murton et al., 2010; Teller et al., 2002; McManus et al., 2004). Recently, a team of scientists proposed a new hypothesis relating the YD cooling to an extraterrestrial (ET) body impact (Firestone et al., 2007). This hypothesis suggested that just before the onset of the YD cooling (ca. 12.9K cal yr BP), a large bolide exploded over the N. American Laurentide Ice Sheet, and the consequences of such a catastrophic event (“meteorite impact winter”) led to the abrupt and significant climate alteration. In Europe, studies of the YD impact hypothesis are limited. However, some findings could be in favor of the ET hypothesis. Those include the presence of an Ir anomaly in the Bodmin Moor sediments from the LYDB in SW England (Marshall et al., 2011), the discovery of non-radiogenic possibly ET-related 187Os/188Os ratios in a sedimentary layer dated 12,893±75 cal yr BP in the S. Netherlands (Beets et al., 2008), and the presence of geochemical markers related to the ET impact in the Late-Glacial lake sediments of NW Russia (Andronikov et al., 2012). Nanodiamonds found in the Usselo Horizon of Belgium and the Netherlands (Tian et al., 2010; van Hoesel et al., 2012) are controversial in terms of their ET origin, and the authors of these papers consider them to be of terrestrial origin, but they are still nanodiamonds and are identified along the LYDB. When a large ET object hits the Earth, small particles resulted from the impact (both from the impactor and from the targeted material) can travel in the atmosphere for thousands of kilometers before they finally get deposited (Bunch et al., 2008; Artemieva and Morgan, 2011). If the impact occurred over N. America, the dominating west winds (Isarin and Renssen, 1999; Brauer et al., 2008) could have delivered the impact-related microparticles as far east as Europe. Lithuania could be an important place in determining the eastern boundary of the Late Pleistocene ET material occurrence. We are applying here geochemical analyses of sediments across four Late-Glacial lake sequences from Lithuania in order to decipher the trace element distribution. This way, the presence of anomalous (in particular, ET-related) components in the sediments can be detected. Concentrations of trace elements in Late- Glacial lakes sediments from four sites in Lithuania were studied using HR-ICP-MS. Most studied sequences are lithologically inhomogeneous and are characterized by uneven distribution of trace elements across the sequences. In some cases the changes in geochemical characteristics are due to changes in lithology and conditions of sediment deposition. However, a few features are not consistent with a sheer lithology change and require other explanations. We were able, with a high level of confidence, to reveal in all four studied sedimentary sequences geochemical fingerprints of the ET event, which occurred at ca. 11.7K cal yr BP. Since there are no known meteorite craters of this age in the region, this event was pronounced, most likely, as an aerial explosion (unless the impact occurred to the continental Ice Sheet). Elevated concentrations of Ni, Cr and somewhat PGE in sediments of this age could be used as a geochemical stratigraphic marker. The presence of possible ET material was also detected for the Ula-2 sequence at the stratigraphic level corresponding to the age of ca. 13.0K cal yr BP, on the basis of sharply increasing concentrations of Ni, Cr, and elevated concentrations of the PGE. In addition to the presence of the ET material in the studied sediments, such geochemical features as elevated concentrations of the REE, Zr and Hf (i.e., the elements abundant in products of the volcanic eruptions) of the sediments from the Ula-2 site allowed us to suggest a presence of volcanic material likely related to the eruption of the Laacher See volcano (12,880 cal yr BP; Brauer et al., 1999). A proposed scheme of the distribution of the ET-related material over the Northern Hemisphere suggests that the consequences of the Late Pleistocene impact/explosion would strongly affect North America, but the rest of the world would be affected by much smaller extent. The applied geochemical methodology, if confirmed by further research on additional sequences, could potentially be used as a tool for correlation between different Late-Glacial records in order to obtain better chronologies for a period during which radiocarbon dating still contains uncertainties. In addition to the presence of the ET material in the studied sediments, such geochemical features as elevated concentrations of the REE, Zr and Hf (i.e., the elements abundant in products of the volcanic eruptions) of the sediments from the Ula-2 site allowed us to suggest a presence of volcanic material likely related to the eruption of the Laacher See volcano (12,880 cal yr BP; Brauer et al., 1999). A proposed scheme of the distribution of the ET-related material over the Northern Hemisphere suggests that the consequences of the Late Pleistocene impact/explosion would strongly affect North America, but the rest of the world would be affected by much smaller extent. The applied geochemical methodology, if confirmed by further research on additional sequences, could potentially be used as a tool for correlation between different Late-Glacial records in order to obtain better chronologies for a period during which radiocarbon dating still contains uncertainties. Acknowledgements. Authors thank C.V.Haynes, J.Ballenger, A. van Hoesel, W.Hoek, M.Drury, D.A.Subetto, T.V.Sapelko, and N.Artemieva for very fruitful discussions on the considered issues. This study was supported partly by the NAI International Collaboration Fund for AVA. Field work was financed by the Research Council of Lithuania, project № LEK-03/2010. References Alley R.B. (2000) The Younger Dryas cold interval as viewed from central Greenland. Quater Sc Rev 19:213-226. Andronikov A., et al. (2012) Tale of two lakes: HR-ICP-MS study of Late Glacial sediments from the Snellegem pond in Belgium and Lake Medvedevskoye in NW Russia. Abst Int Conf “Geomorphology and Quaternary Paleogeography of Polar Regions”, St. Petersburg, Herzen Pedagogical University Press. Artemieva N., Morgan J. (2011) Modeling the Formation of the Global K/Pg Layer. Abst 74th Ann Meteor Soc Palaeolandscapes from Saalian to Weichselian, South Eastern Lithuania Meeting, Abst 5065. Beets C., et al. (2008) Search for extraterrestrial osmium at the Allerod – Younger Dryas Boundary. Amer Geophys Union, Fall Meeting 2008, Abst V53A-2150. Björck S. (2007) Younger Dryas Oscillation, Global Evidence. In: Scott A.E. (ed.) Encyclopedia of Quaternary Sci. Oxford, Elsevier, 1983-1995. Brauer A., et al. (1999) Lateglacial calendar year chronology based on annually laminated sediments from Lake Meerfelder Maar, Germany. Quaternary Intl 61:17-25. Bunch T.E., et al. (2008) Hexagonal diamonds (lonsdaleite) discovered in the K/T impact layer in Spain and New Zealand. AGU Fall Meeting, Abstract PP13C-1476, Eos Trans 89. Fayek M., et al. (2012) Framboidal iron oxide: Chondrite-like material from the black mat, Murray Springs, Arizona. Earth Planet Sci Lett 319-320:251-258. Firestone R.B., et al. (2007) Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions at the Younger Dryas cooling. Proc Natl Acad Sci 104:16016-16021. Higgins M.D., et al. (2011) Bathymetric and petrological evidence for a young (Pleistocene?) 4-km diameter impact crater in the Gulf of Saint Lawrence, Canada. 42nd Lunar Planet Sci Conf 1504-1505. van Hoesel A, et al. (2012) Nanodiamonds and wildfire evidence in the Usselo horizon postdate the Allerød- Younger Dryas boundary. Proc Natl Acad Sci 109:7648-7653. Isarin R.F.B., Renssen H. (1999) Reconstructing and modeling Late Weichselian climates: the Younger Dryas in Europe as a case study. Earth-Sci Rev 48:1-38. Israde-Alcántara I., et al. (2012) Evidence from Central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis. Proc Natl Acad Sci 109:E738-E747. Kennett D.J., et al. (2009) Shock-synthesized hexagonal diamonds in Younger Dryas boundary sediments. Proc Natl Acad Sci 106:12623-12628. Kurbatov A.V., et al. (2010) Discovery of Nanodiamond-rich Layer in Polar Ice Sheet (Greenland). J Glaciol 56:749-759. Lowe J.J., et al. (2008) Synchronisation of palaeoenvironmental events in the North Atlantic region during the Last Termination: a revised protocol recommended by the INTIMATE group. Quaternary Sci Rev 27:6-17. McManus J.F., et al. (2004) Collapse and rapid resumption of Atlantic meridianal circulation linked to deglacial climate changes. Nature 428:834-837. Mahaney W.C., et al. (2010) Evidence from the northwestern Venezuelan Andes for extraterrestrial impact: The black mat enigma. Geomorphology 116:48-57. Marshall W., et al. (2011) Exceptional iridium concentrations found at the Allerød-Younger Dryas transition in sediments from Bodmin Moor in southwest England. Abst XVIII INQUA Congress 21-27 July 2011 Bern, Switzerland (ID 2641). Murton J.B., et al. (2010) Identification of Younger Dryas outburst flood path from Lake Agassiz to the Arctic Ocean. Nature 464:740-743. Peteet D. (1995) Global Younger Dryas? Quaternary Intl 28: 93-104. Sharma M., et al. (2009) High resolution Osmium isotopes in deep-sea ferromanganese crusts reveal a large meteorite impact in the Central Pacific at 12±4 ka. Eos Trans AGU 90, Fall Meeting Suppl, Abst PP33B-06. Svendsen J., et al. (2004) Late Quaternary ice sheet history of Eurasia. Quaternary Sci Rev. Doi:10.1016/ j.quascirev.2003.12.008. Teller J.T., et al. (2002) Freshwater outbursts to the ocean from glacial Lake Agassiz and their role in climate change during the last deglaciation. Quaternary Sci Rev 21:879-887. Thomson J. (1995) Ice age terrestrial carbon change revised. Glob Geochem Cycles 9:377-389. Tian H., et al. (2010) Nanodiamonds do not provide unique evidence for a Younger Dryas impact. Proc Natl Acad Sci Hwww.pnas.org/cgi/doi/10.1073/pnas. 1007695108H.
    Palaeolandscapes from Saalian to Weichselian, South Eastern Lithuania. International Field Symposium. June 25 – 30, 2013, Vilnius-Trakai, Lithuania, Vilnius-Trakai, Lithuania; 06/2013
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    ABSTRACT: The NASA OSIRIS-REx mission will retrieve a sample of the carbonaceous near-Earth Asteroid (101955) Bennu and return it to Earth in 2023. Photometry in the Eight Color Asteroid Survey (ECAS) filter system and Johnson–Cousins V and R filters were conducted during the two most recent apparitions in 2005/2006 and 2011/2012. Lightcurve observations over the nights of September 14–17, 2005 yielded a synodic rotation period of 4.2905 ± 0.0065 h,which is consistent with the results of Nolan et al. (2013). ECAS color measurements made during the same nights confirm the B-type classification of Clark et al. (Clark, B.E., Binzel, R.P., Howell, E.S., Cloutis, E.A., Ockert-Bell, M., Christensen, P., Barucci, M.A., DeMeo, F., Lauretta, D.S., Connolly, H., Soderberg, A.,Hergenrother, C., Lim, L.,Emery, J.,Mueller,M. [2011]. Icarus 216, 462–475).A search for the 0.7 microns hydration feature using themethod of Vilas (Vilas, F. [1994]. Icarus 111, 456–467) did not reveal its presence. Photometry was obtained over a range of phase angles from 15 to 96 degrees between 2005 and 2012. The resulting phase function slope of 0.040 magnitudes per degree is consistent with the phase slopes of other low albedo near-Earth asteroids (Belskaya, I.N., Shevchenko, V.G. [2000]. Icarus 147, 94–105).
    Icarus 05/2013; 226:663-670. · 3.16 Impact Factor
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    ABSTRACT: The so-called Nysa-Polana complex of asteroids is a diverse and widespread group. It appears to be two overlapping families of different asteroid taxonomies: (44) Nysa is an E-type asteroid with the lowest number in the midst of a predominantly S-type cluster and (142) Polana is a B-type asteroid near the low-albedo B- and C-type cluster. Using the data from the Wide-field Infrared Survey Explorer (WISE) mission we have re-analyzed the region around the Nysa-Polana complex in the inner Main Belt, focusing on the low-albedo population. (142) Polana does not appear to be a member of the family of low-albedo asteroids in the Nysa-Polana complex. Rather, the largest is asteroid (495) Eulalia. This asteroid has never before been linked to this complex for an important dynamical reason: it currently has a proper eccentricity slightly below the range of most of the family members. However, its orbit is very close to the 3:1 mean motion resonance with Jupiter and is in a weak secular resonance. We show that its osculating eccentricity varies widely on short timescales and the averaged value diffuses over long timescales. The diffusive orbit, low-albedo, taxonomic similarity and semimajor axis strongly suggests that despite its current proper eccentricity, (495) Eulalia could have recently been at an orbit very central to the family. Hierarchical Clustering Method tests confirm that at an eccentricity of e=0.15, (495) Eulalia could be the parent of the family. The ``Eulalia family'' was formed between 900--1500 Myr ago, and likely resulted from the breakup of a 100--160 km parent body. There is also compelling evidence for an older and more widespread primitive family in the same region of the asteroid belt parented by asteroid (142) Polana.
    Icarus 05/2013; 225(1). · 3.16 Impact Factor
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    ABSTRACT: We discuss the microstructures and textures of sulfide grains from Alais and Orgueil and the implications that these data have on grain formation conditions.
    03/2013;
  • J. Davidson, K. Nagashima, A. N. Krot, D. S. Lauretta
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    ABSTRACT: We present in situ O-isotope measurements of magnetite and associated chondrule olivine in the CK3s Asuka 881595 and Watson 002 to investigate CV3/CK links.
    03/2013;
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    ABSTRACT: Partial melting experiments on R chondrites suggest that GRA 06128/9 might have formed from very-low-degree partial melting in the Ab-SiO_2-Fo system.
    03/2013;
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    ABSTRACT: We present results of LA-ICP-MS analyses of pellets prepared from EOC for the OSIRIS-REx program. Various reference materials were used for comparison.
    03/2013;
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    ABSTRACT: OSIRIS-REx's "Target Asteroids!" is a citizen science program for amateur astronomers that contributes to basic scientific understanding of near-Earth objects.
    03/2013;
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    ABSTRACT: To better understand the formation conditions of type-I and type-II chondrules in the Renazzo-like carbonaceous (CR) chondrites, an in situ major- and minor-element and O-isotope study was conducted. Twenty-one ferromagnesian chondrules from three CR chondrites (GRA 95229, GRA 06100, and QUE 99177) were analyzed to establish an internally-consistent data set. From this study we infer that type-II chondrule precursors contained enhanced S-bearing dust and ice abundances relative to type-I chondrules. There is a relationship between the O-isotope composition and oxidation state of olivine, which may be related to the amount of 16O-poor ice and reduced carbon accreted by chondrule precursors before melting. Type-II chondrules formed under H2O/H2 ratios of ∼230–740 times solar. In contrast, type-I chondrules formed under more reducing conditions with lower H2O/H2 ratios of ∼10–100 times solar. We find a relationship between type-II chondrule petrology (relict free vs. relict grain-bearing) and O-isotope composition, which is due to degree of melting and exchange with a 16O-poor gas reservoir. The 16O-poor gas that interacted with both type-I and type-II chondrules is estimated to have an isotopic composition between ∼δ18Og = 13–27‰ and δ17Og = 10–22‰, different from the O-isotope composition of the water accreted by the CR chondrite parent body. Due to partial melting, type-I chondrules and relict grain-bearing type-II chondrules exchanged with the 16O-poor gas to a lower degree than relict-free type-II chondrules.
    Geochimica et Cosmochimica Acta 01/2013; 101:302–327. · 3.88 Impact Factor
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    ABSTRACT: The late Early Pleistocene deposit, dating from ca. 0.8-0.9 Ma, at Cueva Negra del Estrecho del Río Quípar in Murcia, Spain, contains an abundant assemblage of small flaked artifacts of chert, quartzite and limestone, and one bifacially-flaked limestone hand-axe. We have investigated several possible sources of the chert in an attempt to throw light on Palaeolithic interaction with the environment. Possible sources on the landscape were sampled at distances of up to 30 km from the site. Trace-element fingerprints were analyzed by laser-ablation inductively-coupled plasma mass-spectrometry (ICP-MS). Factor analysis was used to differentiate between sources and as a pointer to where chert analyzed from the cave may have been obtained. Our initial assumption was that most had come from less than 1 km away, namely, from a conglomerate outcrop where chert nodules could be quarried readily. Whilst trace-element evidence supports that hypothesis, it also points to a fair likelihood that some recovered chert lithics had been brought from sources up to 30 km away from the cave. Although evidence is scarce for transport of stone from a similar distance at other late Early Pleistocene sites in Europe, it nevertheless is present in the archaeological record, particularly in Spain where it may be possible to begin to consider differences in stone-procurement strategies between late Early Pleistocene technological assemblages.
    Quartär. 01/2013; 60:7-28.
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    ABSTRACT: TALE OF TWO LAKES: HR-ICP-MS STUDY OF LATE-GLACIAL LAKE SEDIMENTS FROM THE SNELLEGEM POND IN BELGIUM AND THE LAKE MEDVEDEVSKOYE IN NW RUSSIA. IN SEARCH FOR FINGERPRINTS OF THE LATE PLEISTOCENE EXTRATERRESTRIAL EVENT A. Andronikov, D. S. Lauretta, D. Subetto, C. Verbruggen, N. van der Putten, I. Andronikova, T. Sapelko, D. Drosenko Introduction Concentrations of trace elements in Late-Glacial lake sediments from the Snellegem pond (SP) in Western Belgium and the Lake Medvedevskoye (LM) in NW Russia were studied using HR-ICPMS. Trace elements may indicated sources for sediments deposited in lake’s environment. We used concentrations and distributions of trace elements in lacustrine sediments of Europe in order to check a hypothesis about the Late Pleistocene extraterrestrial (ET) impact (Firestone et al., 2007). This hypothesis suggests that ca. 12,900 cal a BP, just before the onset of the YD cooling, a large bolide exploded over the North American Laurentida Ice Shield. The consequences of such a catastrophic event led to abrupt climate change. If the impact occurred over North America, transportation of the impact-related microparticles eastward by the dominating west winds could have delivered such particles as far east as Europe. Snellegem Pond Distribution of trace elements across the sequence of the Late Pleistocene sediments (mostly carbonaceous lake marl) in the SP suggests that they experienced addition of compositionally anomalous material during a short single event. This event resulted in enrichment (up to 200% of the elements’ background values) of a thin layer located 4-5 cm below the lower YD boundary (LYDB) in Cr, Co, Ni, Zn, Ir and Pt (Fig. 1). All these elements are much more abundant in meteorites than in terrestrial sediments, and addition of the ET material seems to be the most likely cause for the observed geochemical feature. We used an age-depth chronological model based on three chronological pinpoints to obtain timing of various events. The first pinpoint is a radiocarbon date located at a depth of 100 cm (Fig. 1) and corresponds to the age of 12,846 cal a BP coinciding with the onset of Greenland Stadial-1 in Lowe et al. (2008). The second one is related to the sudden rise of Pinus pollen at a depth of 130 cm (not in the sampled part of the sequence), and corresponds to the age of 13,200 cal a BP (Hoek, 2001). The third one is the onset of the Older Dryas biozone at a depth of 170 cm (not in the sampled part of the sequence) corresponding to Greenland Interstadial-1d (14,025 cal a BP; Lowe et al., 2008). A stratigraphic position of the “enriched” layer suggests, according to the age-depth model, that it was deposited 12,880 cal a BP, just before the onset of the YD cooling in the region. The pre-YD ET event, resulting in enrichment of sediments in “meteoritic” elements, may have occurred between two volcanic eruptions: (i) an older volcano probably in the Massif Central of France, and erupting more basic ash (Kuznetsov and Subetto, 2004); and (ii) a younger Laacher See volcano of East Eifel in Germany erupting more felsic ash (Wörner et al., 1983; van den Bogaard, 1995). These eruptions, separated by 115-130 years, might have resulted in the addition of volcanic material to the SP sediments (Fig. 1). Distribution of trace elements across the Late Pleistocene sediments of the LM also displays features which may be consistent with addition of materials other than those delivered from usual sources for lake sediments. Such addition is pronounced in enrichment of some stratigraphic horizons in elements that are not entirely typical for lake sediments. The enrichment coincides within the limits of determination errors with both time of the Laacher See volcano eruption (van den Bogaard, 1995) and the time of the ET impact in question (Firestone et al., 2007). However, the enrichment up to 25% above the elements’ background occurs mostly in elements, which are abundant in meteorites such as Ni, Cr, and Zn, and not in elements, which are abundant in volcanic material such as Ti, Zr, Hf, and Nb (Fig. 2), As a consequence, we suggest a possibility that sediments of the LM, like their counterparts from the SP, may carry fingerprints of the Late Pleistocene ET event. An age-depth model based on three radiocarbon dates in the LM Late Pleistocene sedimentary sequence was used in our calculations. The first dated point is located at a depth of 513 cm (not in the sampled part of the sequence) and corresponds to the age of 10,900 cal a BP proposed for a change of a nival climate to a humid climate Subetto (2009). The second one is located at a depth of 548 cm (not in the sampled part of the sequence), characterized by appearance of hydrotroilite, and corresponds to the age of 11,350 cal a BP (Subetto, 2009). The third radiocarbon date of 12,650 cal a BP at a depth of 579 cm (Fig. 2) marks the transition from the Allerød to the YD in the region (Subetto, 2009). According to this age-depth model, a sedimentation rate of ~0.35 mm a-1 could be calculated. Platinum group elements, the most indicative elements to determine between terrestrial and ET components, display some disturbances in distribution around the time of the impact in question. In particularly, Ir and Pt show no coherency before the time of the ET event, and, on the other hand, behave coherently with each other and Ni for some time after the event (Fig. 2). An increase in concentrations of “meteoritic” elements occurs, according to our depth-age model at ca. 13,000 cal a BP, which is within the error limits of the suggested time of the Late Pleistocene impact. Eruption of the Laacher See volcano might have added volcanic material to the LM sediments as well as in the case of the sediments from the SP. Some disturbances in distribution of such “volcanic” elements as Zr, Hf, and Nb can be observed just above the horizon enriched in “meteoritic” elements (Fig. 2). However, a low sedimentation rate and small spatial interval between the layers do not allow for reliable discrimination between the events separated by just 50-60 years. Moreover, in contrast to the lake marl sediments of the SP sequence, the aleuritic sand and aleurite of the LM sequence are relatively abundant in trace elements. That makes it difficult to catch low degrees of trace element enrichments. Conclusions Geochemical features of the Late-Glacial lake sediment sequences of the Snellegem pond of Belgium and to the lesser extent of the Lake Medvedevskoye of NW Russia are consistent with addition of meteoritic material ca. 12,900 cal a BP. There are still no decisive data about the connection between the ET event and the beginning of the Younger Dryas cooling. Because of very low degrees of indicative trace element enrichments, we suggest that the NW Russia can represent the eastern limit of the extension of the Late Pleistocene ET material. Both sedimentary sequences can contain volcanic material from the eruption of the Laacher See volcano and probably from other Late Pleistocene volcanoes of Western Europe as well. References [1] van den Bogaard P., 1995. 40Ar/39Ar ages of sanidine phenocrysts from Laacher See Tephra (12,900 yr BP): Chronostratigraphic and petrological significance. Earth Planet. Sci. Lett., 133, 163-174. [2] Firestone R.B., West A., Kennett J.P., Bunch T.E., Revay Z.S., Schultz P.H., Belgya T., Kennett D.J., Erlandson J.M., Dickenson O.J., Goodyear A.C., Harris R.S., Howard G.A., Kloosterman J.B., Lechler P., Mayewski P.A., Montgomery J., Poreda R., Darrah T., Que Hee S.S., Smith A.R., Stich A., Topping W., Wittke J.H., Wolbach W.S., 2007. Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions at the Younger Dryas cooling. Proc. Nat. Acad. Sci., 104, 16016-16021. [3] Hoek W.Z., 2001. Vegetation response to the ~ 14.7 and ~ 11.5 ka cal. BP climate transitions: is vegetation lagging climate? Global and Planetary Change, 30, 103-115. [4] Kuznetsov D.D, Subetto D.A., 2004. Tephrochronology and its application to palaeolimnology. Reports of the Russian Geographic Society, 134, 79-82 (in Russian). [5] Lowe J.J., Rasmussen S.O., Björck S., Hoek W.Z., Steffensen J.P., Walker M.J.C., Yu Z.C., INTIMATE group., 2008. Synchronisation of palaeoenvironmental events in the North Atlantic region during the Last Termination: a revised protocol recommended by the INTIMATE group. Quaternary Sci. Rev., 27, 6-17. [6] Subetto D.A., 2009. Lake sediments: paleolimnological reconstructions. Saint Petersburg, Publishing House “A. Herzen Russian State Pedagogical University”, 333 p. (in Russian). [7] Wörner G., Beusen J.-M., Duchateau N., Gijbels R., Schmincke H.-U., 1983. Trace element abundances and minera/melt distribution coefficients in phonolites from the Laacher See Volcano (Germany). Contrib. Mineral. Petrol., 84, 152-173.
    “GEOMORPHOLOGY AND PALАEOGEOGRAPHY OF POLAR REGIONS”, Leopoldina Symposium and INQUA Peribaltic Working Group Workshop, Saint-Petersburg, Russia, 9-17 September, 2012, Saint-Petersburg, Russia; 10/2012
  • [show abstract] [hide abstract]
    ABSTRACT: We used planetary radar images and visible lightcurves of asteroid (101955) 1999 RQ36 obtained in 1999 and 2005 to create a three-dimensional shape model of the asteroid and to constrain its surface properties. Radar images at 19-, 15- and 7.5-m resolution taken with the Arecibo and Goldstone planetary radar systems in September/October 1999 and September/October 2005, combined with lightcurves taken in 2005 by CWH and in 1999 by Krugly et al. (2002) were used to model the shape of 1999 RQ36 at 25-m resolution. The asteroid has a fairly smooth “spinning top” shape similar to the primaries of binary asteroids such as 1999 KW4, but with a less well-defined equatorial ridge. The shape appears fairly smooth at small scales, with some large-scale features. There is one 10-20 m boulder that appears in both the 1999 and 2005 radar images, but no other small-scale surface features are evident down to the radar resolution of 7.5-m. The asteroid has a disk-integrated circular polarization ratio of 0.18 ± 0.02 that varies by about 10% over the surface, which is somewhat lower than the polarization ratios obtained for (25143) Itokawa and (433) Eros, suggesting that the surface of 1999 RQ36 is smoother at cm-to-m scales than those objects. The model unambiguously shows the rotation to be retrograde and perpendicular to the orbit plane to within 5° uncertainty, consistent with expectations for YORP spin-up. These results strongly support OSIRIS-REx mission planning. Detailed shape and spin-state information are essential for analysis of orbital stability and sample-targeting accuracy. The smooth surface, polarization ratio, and slope analysis (using the density from Chesley et al., 2012) all provide confidence in the presence of regolith on the surface of 1999 RQ36.
    LPI Contributions. 10/2012;
  • [show abstract] [hide abstract]
    ABSTRACT: The OSIRIS-REx mission, the third in NASA’s New Frontier line, will launch in 2016, visit the near-Earth asteroid (101955) 1999 RQ36, and return samples of its regolith to Earth in 2023. Ground-based observations have already revealed a great deal about 1999 RQ36, including the spectral type (B-type), size, and rotation period. To further characterize the composition, surface grain size, and thermophysical properties, we observed 1999 RQ36 with the Spitzer Space Telescope during the time period 3-9 May 2007. Thermal spectra from 5.2 to 38 μm were measured with the Infrared Spectrograph (IRS) of opposite hemispheres of the body. Photometry at 3.6, 4.5, 5.8, and 8.0 μm was obtained with the Infrared Array Camera and at 16 and 22 μm with the IRS peak-up imaging mode. With the imaging modes, we targeted 10 equally distributed longitudes in order to search for rotational heterogeneities. The thermal inertia derived from the model fit is 600 +/- 150 J m-2s-1/2K-1. This moderately high thermal inertia suggests a regolith with grains less than 2 cm in diameter. Thermal inertia an important parameter for estimating the strength of the Yarkovsky effect, and has been used with measurements of the semi-major axis drift rate to estimate the bulk density of 1999 RQ36 (Chesley et al. 2012). The inferred size of RQ36 is in excellent agreement with radar observations, and the geometric albedo is very low (pv 0.03). There is no evidence for spectral features larger than the noise (S/N 40) in the final spectrum. The imaging data show no evidence for dust around the asteroid. Additional observations with Spitzer are planned for September 2012. We will present the current results and new observations along with an analysis of the thermal lightcurve in the context of the shape model derived from radar data.
    10/2012;
  • [show abstract] [hide abstract]
    ABSTRACT: OSIRIS-REx is an asteroid sample-return mission that was selected by NASA in May 2011 as the third New Frontiers Mission. The name is an acronym that captures the scientific objectives of the mission: Origins, Spectral Interpretation, Resource Identification, and Security Regolith Explorer. OSIRIS-REx will Rendezvous with near-Earth asteroid 101955 (1999 RQ36), which is both the most accessible carbonaceous asteroid and one of the most potentially hazardous asteroids known. The primary objective of the mission is to return a pristine sample from this body to advance our understanding of the generation, evolution, and maturation of regolith on small bodies. 1999 RQ36 was discovered in September 1999 by the LINEAR survey and is an Apollo NEO with a semi-major axis of 1.126 AU. Observations of 1999 RQ36 were performed by team members using ground-based telescopes [1] the Spitzer Space Telescope [2] the Arecibo Planetary Radar System [3], and other assets. These data strongly support the presence of abundant regolith, comprised of fine gravel (4-8 mm), ideal for sampling. 1999 RQ36 comes within 0.003 AU of the Earth and has the highest impact probability of any known asteroid [4]. Although by far the most important objective of this mission is to collect and return a pristine sample, it will also significantly improve our understanding of details of this body from data collected from remote observations. This work will provide a brief overview of the mission followed by a more detailed discussion of the planned remote sensing observations to be taken in proximity to the asteroid.
    09/2012;

Publication Stats

384 Citations
204.08 Total Impact Points

Institutions

  • 2005–2014
    • The University of Arizona
      • Department of Planetary Sciences
      Tucson, Arizona, United States
    • NASA
      Washington, West Virginia, United States
  • 1999–2012
    • Arizona State University
      • Department of Chemistry and Biochemistry
      Mesa, AZ, United States
  • 2006
    • Sierra Tucson
      Tucson, Arizona, United States