Showing papers by "John Bridges published in 2006"
Donald E. Brownlee1, Peter Tsou2, Jérôme Aléon3, Conel M. O'd. Alexander4 +182 more•Institutions (57)
TL;DR: The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study, and preliminary examination shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin.
Abstract: The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales.
886 citations
United States Naval Research Laboratory1, Brookhaven National Laboratory2, Space Sciences Laboratory3, Kingsborough Community College4, University of Münster5, Michigan State University6, Osaka University7, Jet Propulsion Laboratory8, Lawrence Livermore National Laboratory9, Kobe University10, European Synchrotron Radiation Facility11, Washington University in St. Louis12, University of Chicago13, École normale supérieure de Lyon14, University of New Mexico15, Kyushu University16, University of Tokyo17, University of Washington18, Lawrence Berkeley National Laboratory19, University of Jena20, University of Hawaii21, American Museum of Natural History22, Case Western Reserve University23, University of Hyogo24, United States Geological Survey25, Imperial College London26, State University of New York System27, Open University28, Stanford University29
TL;DR: The bulk of the comet 81P/Wild 2 samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger ferromagnesian silicates, Fe-Ni sulfides,Fe-Ni metal, and accessory phases.
Abstract: The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.
644 citations
Lawrence Livermore National Laboratory1, Open University2, University of Washington3, University of Kent4, University of California, San Diego5, University of Chicago6, Washington University in St. Louis7, Max Planck Society8, Natural History Museum9, Lille University of Science and Technology10, University of California, Berkeley11, University of Münster12, United States Naval Research Laboratory13, Spanish National Research Council14, California Institute of Technology15
TL;DR: Particles emanating from comet 81P/Wild 2 collided with the Stardust spacecraft at 6.1 kilometers per second, producing hypervelocity impact features on the collector surfaces that were returned to Earth.
Abstract: Particles emanating from comet 81P/Wild 2 collided with the Stardust spacecraft at 6.1 kilometers per second, producing hypervelocity impact features on the collector surfaces that were returned to Earth. The morphologies of these surprisingly diverse features were created by particles varying from dense mineral grains to loosely bound, polymineralic aggregates ranging from tens of nanometers to hundreds of micrometers in size. The cumulative size distribution of Wild 2 dust is shallower than that of comet Halley, yet steeper than that of comet Grigg-Skjellerup.
308 citations
State University of New York at Plattsburgh1, European Synchrotron Radiation Facility2, Lawrence Livermore National Laboratory3, Goethe University Frankfurt4, Stanford University5, Open University6, University of Washington7, Smithsonian Institution8, Dartmouth College9, Lawrence Berkeley National Laboratory10, École normale supérieure de Lyon11, Washington University in St. Louis12, University of California, Berkeley13, Centre national de la recherche scientifique14, Max Planck Society15, Rutgers University16, University of Antwerp17, Natural History Museum18, University of Chicago19, university of lille20, Kyushu University21, National Institute of Advanced Industrial Science and Technology22, California Institute of Technology23, University of Georgia24, University of New Mexico25, University of Münster26, United States Naval Research Laboratory27, Cold Regions Research and Engineering Laboratory28, Osaka University29, Ghent University30
TL;DR: The elements Cu, Zn, and Ga appear enriched in this Wild 2 material, which suggests that the CI meteorites may not represent the solar system composition for these moderately volatile minor elements.
Abstract: We measured the elemental compositions of material from 23 particles in aerogel and from residue in seven craters in aluminum foil that was collected during passage of the Stardust spacecraft through the coma of comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size scale analyzed (similar to 180 ng). The mean elemental composition of this Wild 2 material is consistent with the CI meteorite composition, which is thought to represent the bulk composition of the solar system, for the elements Mg, Si, Mn, Fe, and Ni to 35%, and for Ca and Ti to 60%. The elements Cu, Zn, and Ga appear enriched in this Wild 2 material, which suggests that the CI meteorites may not represent the solar system composition for these moderately volatile minor elements.
224 citations
TL;DR: In this paper, the shergottite SNC meteorites were derived from Mars as a product of 4-7 ejection events, probably from Tharsis and Elysium-Amazonis, and the SNCs can be classified both petrographically and geochemically.
Abstract: A group of 32 meteorites, the SNC ( S hergotty, N akhla, C hassigny) group, was derived from Mars as a product of 4–7 ejection events, probably from Tharsis and Elysium–Amazonis. The SNCs either have basaltic mineralogy or some are ultramafic cumulates crystallized from basaltic melts. The SNCs can be classified both petrographically and geochemically. We classify the shergottite SNC meteorites on the basis of their light rare earth element (LREE) depletion into highly depleted, moderately depleted and slightly depleted. The slightly depleted samples (which are mainly but not exclusively aphyric basalts) show high log 10 f O 2 values (QFM −1.0, where QFM is quartz–fayalite–magnetite). Highly depleted samples, which are mainly olivine-phyric basalts, have low log 10 f O 2 values (QFM −3.5). On the basis of mixing calculations between La/Lu and 87 Sr/ 86 Sr we favour models linking the correlation between LREE abundances and log 10 f O 2 to mantle heterogeneity rather than contamination by oxidized, LREE-rich crustal fluids. SNC chemistry in general reflects the Fe-rich mantle of Mars (which contains twice as much FeO as the Earth9s mantle), the late accretion of chondritic material into the mantle, and possibly the presence of a plagioclase-rich magma ocean, which acted to variably deplete the mantle in Al. The high FeO contents of the SNC melts are associated with high melt densities (allowing the ponding of large magma bodies) and low viscosities, both of which are consistent with the large scale of many observed martian lava flows.
115 citations
TL;DR: In this paper, a preliminary investigation of the luminescence characteristics (sensitivity, dose response, fading) of some Martian analogue mineral and rock samples are presented and implications discussed for Martian luminecence dating.
38 citations
TL;DR: In this paper, the authors demonstrate that slight variations in average grain size can be exploited, using differential centrifugation (followed by analysis using electron microscopy and isotope-ratio mass spectrometry), to produce separates that reflect contributions from specific sources.
Abstract: Although the most abundant type of presolar grain found in meteorites is nanometer-sized diamond ("nanodiamond"), the dimensions make study of individual crystallites rather uninformative; instead, laboratory astrophysicists usually work with an ensemble of grains (generally in concentrated form, produced by chemical treatments). This, of course, produces results that are just a measure of average properties, which makes assessing the origin of diamonds quite difficult. An apparently uniform distribution of chemical and physical properties of the grains has been interpreted as their having a single origin. In this paper, however, we demonstrate that slight variations in average grain size can be exploited, using differential centrifugation (followed by analysis using electron microscopy and isotope-ratio mass spectrometry), to produce separates that reflect contributions from specific sources. In this way we identify a contribution from carbon stars, at the asymptotic giant branch stage of evolution, in addition to components already ascribed to supernovae and solar nebular processing. The astrophysical significance of the new discovery is discussed.
21 citations
01 Aug 2006
TL;DR: Zolensky et al. as mentioned in this paper presented the final results of the PRELIMINARY EXAMINATION of the Stardust Mineralogy/Petrology Subteam.
Abstract: NUCLEUS SAMPLES — FINAL RESULTS OF THE PRELIMINARY EXAMINATION TEAM. Stardust Mineralogy/Petrology Subteam: Michael Zolensky, Phil Bland, John Bradley, Adrian Brearley, Sean Brennan, John Bridges, Donald Brownlee, Anna Butterworth, Zurong Dai, Denton Ebel, Matt Genge, Matthieu Gounelle, Giles Graham, Jeff Grossman, Lawrence Grossman, Ralph Harvey, Hope Ishii, Anton Kearsley, Lindsay Keller, Alexander Krot, Falko Langenhorst, Antonio Lanzirotti, Hugues Leroux, Graciela Matrajt, Keiko Messenger, Takashi Mikouchi, Tomoki Nakamura, Kazumasa Ohsumi, Kyoko Okudaira, Murielle Perronnet, Frans Rietmeijer, Steven Simon, Thomas Stephan, Rhonda Stroud, Mitra Taheri, Kazu Tomeoka, Alice Toppani, Peter Tsou, Akira Tsuchiyama, Michael Velbel, Iris Weber, Mike Weisberg, Andrew Westphal, Hajime Yano, Thomas Zega. NASA JSC (email: michael.e.zolensky@nasa.gov), Imperial College, Lawrence Livermore National Lab., Univ. New Mexico, SLAC, Open Univ., Univ. Washington, Univ. California, Berkeley, American Museum of Natural History, Muséum National D’Histoire Naturelle, Univ. Chicago, Case Western Reserve Univ., Natural History Museum, Univ. Hawaii, Brookhaven National Lab, Univ. Sciences et Technologies de Lille, Univ. Tokyo, Kyushu Univ., Inst. Materials Structure Science-KEK, JAXA-ISAS, Univ. Münster, Naval Research Lab., Kobe University, JPL, Osaka Univ., Kingsborough Community College, Inst. für Geowissenschaften, US Geol. Survey, Michigan State Univ.
7 citations
01 Jan 2006
TL;DR: The sample return capsule of the Stardust spacecraft will be recovered in northern Utah on January 15, 2006, and under nominal conditions it will be delivered to the new Stardust Curation Laboratory at the Johnson Space Center two days later as discussed by the authors.
Abstract: The sample return capsule of the Stardust spacecraft will be recovered in northern Utah on January 15, 2006, and under nominal conditions it will be delivered to the new Stardust Curation Laboratory at the Johnson Space Center two days later. Within the first week we plan to begin the harvesting of aerogel cells, and the comet nucleus samples they contain for detailed analysis. By the time of the LPSC meeting we will have been analyzing selected removed grains for more than one month. This presentation will present the first results from the mineralogical and petrological analyses that will have been performed.
6 citations
01 Mar 2006
TL;DR: In this paper, a new technique using dual beam FIB/SEM with which impact residues can be extracted from microcraters and analyzed by EDS is described, which will allow the determination of residue compositions from Stardust craters.
Abstract: We describe results from a new technique using dual beam FIB/SEM with which impact residues can be extracted from microcraters and analysed by EDS This will allow the determination of residue compositions from Stardust craters
TL;DR: In this article, the spectrum of the Stardust grains between 200 nm and 800 nm was measured to provide an additional technique for characterizing the grains, one that is complementary to other spectroscopic techniques and one that produces results that can be matched directly with spectra acquired remotely (with telescope or spacecraft instrumentation).
Abstract: NASA's Stardust mission flew through the coma of comet Wild 2 in January 2004, capturing dust grains as it did so. The grains were returned safely to Earth in January 2006, and are in the process of being distributed to investigators. As members of the Spectroscopy Preliminary Examination Team, we are preparing to analyse Stardust grains. Our contribution is to measure the spectrum of the grains between 200 nm (in the near ultraviolet) and 800 nm (near infrared). The purpose of the measurement is to provide an additional technique for characterizing the grains, one that is complementary to other spectroscopic techniques and one that produces results that can be matched directly with spectra acquired remotely (with telescope or spacecraft instrumentation). As part of the preparation for analysis of Stardust materials, we are producing a database of spectra from appropriate minerals, and are honing the technique through analysis of primitive meteorites.
Journal Article•
TL;DR: The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe -Ni metal, and accessory phases.
Abstract: The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.