Michael E. Zolensky

Publications (54)304.09 Total impact

• Source

  Available from: Munetaka Ueno

  Article: Itokawa dust particles: a direct link between S-type asteroids and ordinary chondrites.

  Tomoki Nakamura, Takaaki Noguchi, Masahiko Tanaka, Michael E Zolensky, Makoto Kimura, Akira Tsuchiyama, Aiko Nakato, Toshihiro Ogami, Hatsumi Ishida, Masayuki Uesugi, [......], Akio Fujimura, Ryuji Okazaki, Scott A Sandford, Yukihiro Ishibashi, Masanao Abe, Tatsuaki Okada, Munetaka Ueno, Toshifumi Mukai, Makoto Yoshikawa, Junichiro Kawaguchi
  [show abstract] [hide abstract]
  ABSTRACT: The Hayabusa spacecraft successfully recovered dust particles from the surface of near-Earth asteroid 25143 Itokawa. Synchrotron-radiation x-ray diffraction and transmission and scanning electron microscope analyses indicate that the mineralogy and mineral chemistry of the Itokawa dust particles are identical to those of thermally metamorphosed LL chondrites, consistent with spectroscopic observations made from Earth and by the Hayabusa spacecraft. Our results directly demonstrate that ordinary chondrites, the most abundant meteorites found on Earth, come from S-type asteroids. Mineral chemistry indicates that the majority of regolith surface particles suffered long-term thermal annealing and subsequent impact shock, suggesting that Itokawa is an asteroid made of reassembled pieces of the interior portions of a once larger asteroid.
  Science 08/2011; 333(6046):1113-6. · 31.20 Impact Factor
• Article: Irradiation history of Itokawa regolith material deduced from noble gases in the Hayabusa samples.

  Keisuke Nagao, Ryuji Okazaki, Tomoki Nakamura, Yayoi N Miura, Takahito Osawa, Ken-ichi Bajo, Shintaro Matsuda, Mitsuru Ebihara, Trevor R Ireland, Fumio Kitajima, [......], Kei Shirai, Masanao Abe, Toru Yada, Yukihiro Ishibashi, Akio Fujimura, Toshifumi Mukai, Munetaka Ueno, Tatsuaki Okada, Makoto Yoshikawa, Junichiro Kawaguchi
  [show abstract] [hide abstract]
  ABSTRACT: Noble gas isotopes were measured in three rocky grains from asteroid Itokawa to elucidate a history of irradiation from cosmic rays and solar wind on its surface. Large amounts of solar helium (He), neon (Ne), and argon (Ar) trapped in various depths in the grains were observed, which can be explained by multiple implantations of solar wind particles into the grains, combined with preferential He loss caused by frictional wear of space-weathered rims on the grains. Short residence time of less than 8 million years was implied for the grains by an estimate on cosmic-ray-produced (21)Ne. Our results suggest that Itokawa is continuously losing its surface materials into space at a rate of tens of centimeters per million years. The lifetime of Itokawa should be much shorter than the age of our solar system.
  Science 08/2011; 333(6046):1128-31. · 31.20 Impact Factor
• Article: Oxygen isotopic compositions of asteroidal materials returned from Itokawa by the Hayabusa mission.

  Hisayoshi Yurimoto, Ken-ichi Abe, Masanao Abe, Mitsuru Ebihara, Akio Fujimura, Minako Hashiguchi, Ko Hashizume, Trevor R Ireland, Shoichi Itoh, Juri Katayama, [......], Naoya Sakamoto, Yusuke Seto, Masashi Takei, Akira Tsuchiyama, Masayuki Uesugi, Shigeyuki Wakaki, Toru Yada, Kosuke Yamamoto, Makoto Yoshikawa, Michael E Zolensky
  [show abstract] [hide abstract]
  ABSTRACT: Meteorite studies suggest that each solar system object has a unique oxygen isotopic composition. Chondrites, the most primitive of meteorites, have been believed to be derived from asteroids, but oxygen isotopic compositions of asteroids themselves have not been established. We measured, using secondary ion mass spectrometry, oxygen isotopic compositions of rock particles from asteroid 25143 Itokawa returned by the Hayabusa spacecraft. Compositions of the particles are depleted in (16)O relative to terrestrial materials and indicate that Itokawa, an S-type asteroid, is one of the sources of the LL or L group of equilibrated ordinary chondrites. This is a direct oxygen-isotope link between chondrites and their parent asteroid.
  Science 08/2011; 333(6046):1116-9. · 31.20 Impact Factor
• Article: Three-dimensional structure of Hayabusa samples: origin and evolution of Itokawa regolith.

  Akira Tsuchiyama, Masayuki Uesugi, Takashi Matsushima, Tatsuhiro Michikami, Toshihiko Kadono, Tomoki Nakamura, Kentaro Uesugi, Tsukasa Nakano, Scott A Sandford, Ryo Noguchi, [......], Takaaki Noguchi, Ryuji Okazaki, Hisayoshi Yurimoto, Michael E Zolensky, Toshifumi Mukai, Masanao Abe, Toru Yada, Akio Fujimura, Makoto Yoshikawa, Junichiro Kawaguchi
  [show abstract] [hide abstract]
  ABSTRACT: Regolith particles on the asteroid Itokawa were recovered by the Hayabusa mission. Their three-dimensional (3D) structure and other properties, revealed by x-ray microtomography, provide information on regolith formation. Modal abundances of minerals, bulk density (3.4 grams per cubic centimeter), and the 3D textures indicate that the particles represent a mixture of equilibrated and less-equilibrated LL chondrite materials. Evidence for melting was not seen on any of the particles. Some particles have rounded edges. Overall, the particles' size and shape are different from those seen in particles from the lunar regolith. These features suggest that meteoroid impacts on the asteroid surface primarily form much of the regolith particle, and that seismic-induced grain motion in the smooth terrain abrades them over time.
  Science 08/2011; 333(6046):1125-8. · 31.20 Impact Factor
• Article: Electron microscopy of pyroxene in the Almahata Sitta ureilite

  Takashi MIKOUCHI, Michael E. ZOLENSKY, Ichiro OHNISHI, Toshiaki SUZUKI, Hiroshi TAKEDA, Peter JENNISKENS, Muawia H. SHADDAD
  [show abstract] [hide abstract]
  ABSTRACT: Abstract– We performed scanning electron microscope–electron backscatter diffraction (SEM-EBSD) and focused ion beam–transmission electron microscopy (FIB-TEM) investigations of pyroxene in the Almahata Sitta ureilite (sample #7). The pyroxenes (mg# = ∼0.92) are present as minute individual grains (10–20 μm in size) showing a polycrystalline texture, and they are both low-Ca and high-Ca pyroxenes. Although their Ca contents are as low as Wo2–3, the EBSD analysis shows that low-Ca pyroxenes are clinopyroxene (P21/c). The obtained pyroxene equilibration temperature (1240–1280 °C) is consistent with the previous studies on many ureilites. In low-Ca pigeonite, (001) augite exsolution lamellae (10–15 nm wide) develop in the pigeonite host (20–45 nm wide), and a similar exsolution texture was observed in augite. The exsolution wavelength of pyroxene (typically 30–60 nm) gives the cooling rate of 0.2–5 °C h−1. Such a rapid cooling probably records quenching from high temperature (1240–1280 °C) down to 1000 °C (estimated from the exsolution pair) due to the breakup of the ureilite parent body (UPB) while it was still hot. The pyroxene microstructure of Almahata Sitta is within the range of known ureilites and is most similar to that of Allan Hills (ALH) A81101 with the affinity of polycrystalline texture. The coarser exsolution texture of ALHA81101 pyroxene suggests slower cooling history than Almahata Sitta. However, direct comparison is difficult because of different pyroxene compositions. Because ALHA77257 has a similar pyroxene composition to Almahata Sitta and does not show visible pyroxene exsolution, it should have cooled faster than Almahata Sitta. Rapid, albeit variable cooling rates observed in different ureilite samples may suggest that they originated from UPB fragments of different size.
  Meteoritics & Planetary Science. 12/2010; 45(10‐11):1812 - 1820.
• Article: Three‐dimensional shapes and Fe contents of Stardust impact tracks: A track formation model and estimation of comet Wild 2 coma dust particle densities

  Yosuke IIDA, Akira TSUCHIYAMA, Toshihiko KADONO, Kanako SAKAMOTO, Tomoki NAKAMURA, Kentaro UESUGI, Tsukasa NAKANO, Michael E. ZOLENSKY
  [show abstract] [hide abstract]
  ABSTRACT: Abstract– We investigated three-dimensional structures of comet Wild 2 coma particle impact tracks using synchrotron radiation (SR) X-ray microtomography at SPring-8 to elucidate the nature of comet Wild 2 coma dust particles captured in aerogel by understanding the capture process. All tracks have a similar entrance morphology, indicating a common track formation process near the entrance by impact shock propagation irrespective of impactor materials. Distributions of elements along the tracks were simultaneously measured using SR-XRF. Iron is distributed throughout the tracks, but it tends to concentrate in the terminal grains and at the bottoms of bulbs. Based on these results, we propose an impact track formation process. We estimate the densities of cometary dust particles based on the hypothesis that the kinetic energy of impacting dust particles is proportional to the track volume. The density of 148 cometary dust particles we investigated ranges from 0.80 to 5.96 g cm−3 with an average of 1.01 (±0.25) g cm−3. Moreover, we suggest that less fragile crystalline particles account for approximately 5 vol% (20 wt%) of impacting particles. This value of crystalline particles corresponds to that of chondrules and CAIs, which were transported from the inner region of the solar system to the outer comet-forming region. Our results also suggest the presence of volatile components, such as organic material and perhaps ice, in some bulbous tracks (type-C).
  Meteoritics & Planetary Science. 07/2010; 45(8):1302 - 1319.
• Source

  Available from: Sue Wirick

  Article: Assessment and control of organic and other contaminants associated with the Stardust sample return from comet 81P/Wild 2

  Scott A. SANDFORD, Saša BAJT, Simon J. CLEMETT, George D. CODY, George COOPER, Bradley T. DEGREGORIO, Vanessa De VERA, Jason P. DWORKIN, Jamie E. ELSILA, George J. FLYNN, [......], Antonio LANZIROTTI, Thomas LIMERO, Mildred P. MARTIN, Christopher J. SNEAD, Maegan K. SPENCER, Thomas STEPHAN, Andrew WESTPHAL, Sue WIRICK, Richard N. ZARE, Michael E. ZOLENSKY
  [show abstract] [hide abstract]
  ABSTRACT: Abstract– Numerous potential sources of organic contaminants could have greatly complicated the interpretation of the organic portions of the samples returned from comet 81P/Wild 2 by the Stardust spacecraft. Measures were taken to control and assess potential organic (and other) contaminants during the design, construction, and flight of the spacecraft, and during and after recovery of the sample return capsule. Studies of controls and the returned samples suggest that many of these potential sources did not contribute any significant material to the collectors. In particular, contamination from soils at the recovery site and materials associated with the ablation of the heatshield do not appear to be significant problems. The largest source of concern is associated with the C present in the original aerogel. The relative abundance of this carbon can vary between aerogel tiles and even within individual tiles. This C was fortunately not distributed among a complex mixture of organics, but was instead largely present in a few simple forms (mostly as Si-CH3 groups). In most cases, the signature of returned cometary organics can be readily distinguished from contaminants through their different compositions, nonterrestrial isotopic ratios, and/or association with other cometary materials. However, some conversion of the carbon indigenous to the flight aerogel appears to have happened during particle impact, and some open issues remain regarding how this C may be processed into new forms during the hypervelocity impact collection of the comet dust.
  Meteoritics & Planetary Science. 02/2010; 45(3):406 - 433.
• Article: Fayalitic olivine in matrix of the Krymka LL3.1 chondrite: Vapor‐solid growth in the solar nebula

  MICHAEL K. WEISBERG, MICHAEL E. ZOLENSKY, MARTIN PRINZ
  [show abstract] [hide abstract]
  ABSTRACT: Abstract— Fayalitic olivine (Fa54–94) is a ubiquitous component in the matrix of Krymka (LL3.1) as well as in other highly unequilibrated chondrites (ordinary and carbonaceous). In Krymka, the fayalitic olivine has an unusual anisotropic platy morphology that occurs in at least five types of textural settings that can be characterized as: (1) isolated platelets, (2) clusters of platelets, (3) euhedral to subhedral crystals, (4) overgrowths of platelets on forsteritic olivine, and (5) fluffy (porous) aggregates. From transmission electron microscope (TEM) investigation, the direction of elongation of the platy olivine overgrowths on forsteritic olivine substrates is along the c axis and in most cases it corresponds with the c axis of the substrate olivine, which suggests that the fayalitic olivine grew in this unusual morphology and is not a replacement product of preexisting material. The fayalitic olivine in the matrix of Krymka is compositionally similar to olivine with platy morphology in the matrix of some CV3 chondrites and both have similar Fe/Mn ratios, but important morphological differences indicate that their relationship needs to be explored further. Textural and compositional data indicate that the fayalitic olivine in the matrix of Krymka, as well as in some other unequilibrated ordinary chondrites, formed prior to final lithification of the meteorite and probably prior to parent body accretion. We find that formation of the fayalitic olivine by vapor-solid growth provides the best explanation for our observations and data and is the only feasible mechanism for the formation of fayalitic olivine in the matrix of Krymka. We propose that the fayalitic olivine formed by vaporization and recondensation of olivine rich-dust, during a period of enhanced dust/gas ratio in the nebula.
  Meteoritics & Planetary Science. 02/2010; 32(6):791 - 801.
• Source

  Available from: Zack Gainsforth

  Article: Discovery of non‐random spatial distribution of impacts in the Stardust cometary collector

  Andrew J. Westphal, Ronald K. Bastien, Janet Borg, John Bridges, Donald E. Brownlee, Mark J. Burchell, Andrew F. Cheng, Benton C. Clark, Zahia Djouadi, Christine Floss, [......], Kuljeet Marhas, Keiko Nakamura-Messenger, Scott A. Sandford, Thomas H. See, Frank J. Stadermann, Nick E. Teslich, Samuel Tsitrin, Jack L. Warren, Penelope J. Wozniakiewicz, Michael E. Zolensky
  [show abstract] [hide abstract]
  ABSTRACT: Abstract— We report the discovery that impacts in the Stardust cometary collector are not distributed randomly in the collecting media, but appear to be clustered on scales smaller than ˜10 cm. We also report the discovery of at least two populations of oblique tracks. We evaluate several hypotheses that could explain the observations. No hypothesis is consistent with all the observations, but the preponderance of evidence points toward at least one impact on the central Whipple shield of the spacecraft as the origin of both clustering and low-angle oblique tracks. High-angle oblique tracks unambiguously originate from a non-cometary impact on the spacecraft bus just forward of the collector.
  Meteoritics & Planetary Science. 01/2010; 43(1‐2):415 - 429.
• Source

  Available from: astrochem.org

  Article: TOF‐SIMS analysis of cometary particles extracted from Stardust aerogel

  Thomas Stephan, George J. Flynn, Scott A. Sandford, Michael E. Zolensky
  [show abstract] [hide abstract]
  ABSTRACT: Abstract— Sections of seven cometary fragments extracted from the aerogel collector flown on the Stardust mission to comet 81P/Wild 2 were investigated with TOF-SIMS. These grains showed a rather heterogeneous chemical and mineralogical composition on a submicrometer scale. However, their average chemical composition is close to bulk CI chondritic values, which is consistent with analyses of numerous Stardust samples using various techniques. As a result, the TOF-SIMS analyses support the conclusion that Wild 2 has a CI-like bulk composition. The cometary particles resemble anhydrous chondritic porous interplanetary dust particles, which have previously been suggested to originate from comets. For one of the fragments, polycyclic aromatic hydrocarbons that could possibly be attributed to the comet were observed.
  Meteoritics & Planetary Science. 01/2010; 43(1‐2):285 - 298.
• Article: Heavily‐hydrated lithic clasts in CH chondrites and the related, metal‐rich chondrites Queen Alexandra Range 94411 and Hammadah al Hamra 237

  Ansgar GRESHAKE, Alexander N. KROT, Anders MEIBOM, Michael K. WEISBERG, Michael E. ZOLENSKY, Klaus KEIL
  [show abstract] [hide abstract]
  ABSTRACT: Abstract— Fine-grained, heavily-hydrated lithic clasts in the metal-rich (CB) chondrites Queen Alexandra Range (QUE) 94411 and Hammadah al Hamra 237 and CH chondrites, such as Patuxent Range (PAT) 91546 and Allan Hills (ALH) 85085, are mineralogically similar suggesting genetic relationship between these meteorites. These clasts contain no anhydrous silicates and consist of framboidal and platelet magnetite, prismatic sulfides (pentlandite and pyrrhotite), and Fe-Mn-Mg-bearing Ca-carbonates set in a phyllosilicate-rich matrix. Two types of phyllosilicates were identified: serpentine, with basal spacing of ˜0.73 nm, and saponite, with basal spacings of about 1.1–1.2 nm. Chondrules and FeNi-metal grains in CB and CH chondrites are believed to have formed at high temperature (>1300 K) by condensation in a solar nebula region that experienced complete vaporization. The absence of aqueous alteration of chondrules and metal grains in CB and CH chondrites indicates that the clasts experienced hydration in an asteroidal setting prior to incorporation into the CH and CB parent bodies. The hydrated clasts were either incorporated during regolith gardening or accreted together with chondrules and FeNi-metal grains after these high-temperature components had been transported from their hot formation region to a much colder region of the solar nebula.
  Meteoritics & Planetary Science. 01/2010; 37(2):281 - 293.
• Source

  Available from: Kevin Mckeegan

  Article: A unique basaltic micrometeorite expands the inventory of solar system planetary crusts.

  Matthieu Gounelle, Marc Chaussidon, Alessandro Morbidelli, Jean-Alix Barrat, Cécile Engrand, Michael E Zolensky, Kevin D McKeegan
  [show abstract] [hide abstract]
  ABSTRACT: Micrometeorites with diameter approximately 100-200 microm dominate the flux of extraterrestrial matter on Earth. The vast majority of micrometeorites are chemically, mineralogically, and isotopically related to carbonaceous chondrites, which amount to only 2.5% of meteorite falls. Here, we report the discovery of the first basaltic micrometeorite (MM40). This micrometeorite is unlike any other basalt known in the solar system as revealed by isotopic data, mineral chemistry, and trace element abundances. The discovery of a new basaltic asteroidal surface expands the solar system inventory of planetary crusts and underlines the importance of micrometeorites for sampling the asteroids' surfaces in a way complementary to meteorites, mainly because they do not suffer dynamical biases as meteorites do. The parent asteroid of MM40 has undergone extensive metamorphism, which ended no earlier than 7.9 Myr after solar system formation. Numerical simulations of dust transport dynamics suggest that MM40 might originate from one of the recently discovered basaltic asteroids that are not members of the Vesta family. The ability to retrieve such a wealth of information from this tiny (a few micrograms) sample is auspicious some years before the launch of a Mars sample return mission.
  Proceedings of the National Academy of Sciences 05/2009; 106(17):6904-9. · 9.68 Impact Factor
• Source

  Available from: Kanako Sakamoto

  Article: Chondrulelike objects in short-period comet 81P/Wild 2.

  Tomoki Nakamura, Takaaki Noguchi, Akira Tsuchiyama, Takayuki Ushikubo, Noriko T Kita, John W Valley, Michael E Zolensky, Yuki Kakazu, Kanako Sakamoto, Etsuko Mashio, Kentaro Uesugi, Tsukasa Nakano
  [show abstract] [hide abstract]
  ABSTRACT: The Stardust spacecraft returned cometary samples that contain crystalline material, but the origin of the material is not yet well understood. We found four crystalline particles from comet 81P/Wild 2 that were apparently formed by flash-melting at a high temperature and are texturally, mineralogically, and compositionally similar to chondrules. Chondrules are submillimeter particles that dominate chondrites and are believed to have formed in the inner solar nebula. The comet particles show oxygen isotope compositions similar to chondrules in carbonaceous chondrites that compose the middle-to-outer asteroid belt. The presence of the chondrulelike objects in the comet suggests that chondrules have been transported out to the cold outer solar nebula and spread widely over the early solar system.
  Science 10/2008; 321(5896):1664-7. · 31.20 Impact Factor
• Article: TOF‐SIMS analysis of cometary matter in Stardust aerogel tracks

  Thomas Stephan, Detlef Rost, Edward P. Vicenzi, Emma S. Bullock, Glenn J. MacPherson, Andrew J. Westphal, Christopher J. Snead, George J. Flynn, Scott A. Sandford, Michael E. Zolensky
  [show abstract] [hide abstract]
  ABSTRACT: Abstract— Cometary matter in aerogel samples from the Stardust mission was investigated with TOF-SIMS for its elemental and organic composition. While single grains >1 μm are highly variable in their chemical composition, nanometer-scale material found in the wall of one track has within a factor of 1.22 bulk CI chondritic element ratios relative to Fe for Na, Mg, A1, Ti, Cr, Mn, and Co. Compared to CI, a depletion in Ca by a factor of four and an enrichment in Ni by a factor of two was observed. These results seem to confirm recent reports of a CI-like bulk composition of Wild 2. The analysis of organic compounds in aerogel samples is complicated by the presence of contaminants in the capture medium. However, polycyclic aromatic hydrocarbons that could possibly be attributed to the comet were observed.
  Meteoritics & Planetary Science. 01/2008; 43(1‐2):233 - 246.
• Source

  Available from: Emma S Bullock

  Article: TOF‐SIMS analysis of cometary matter in Stardust aerogel tracks

  Thomas Stephan, Detlef Rost, Edward P Vicenzi, Emma S Bullock, Glenn J Macpherson, Andrew J Westphal, Christopher J Snead, George J Flynn, Scott A Sandford, Michael E Zolensky
  [show abstract] [hide abstract]
  ABSTRACT: Cometary matter in aerogel samples from the Stardust mission was investigated with TOF-SIMS for its elemental and organic composition. While single grains >1 μm are highly variable in their chemical composition, nanometer-scale material found in the wall of one track has within a factor of 1.22 bulk CI chondritic element ratios relative to Fe for Na, Mg, Al, Ti, Cr, Mn, and Co. Compared to CI, a depletion in Ca by a factor of four and an enrichment in Ni by a factor of two was observed. These results seem to confirm recent reports of a CI-like bulk composition of Wild 2. The analysis of organic compounds in aerogel samples is complicated by the presence of contaminants in the capture medium. However, polycyclic aromatic hydrocarbons that could possibly be attributed to the comet were observed.
  Meteoritics & planetary science 01/2008; 43:233-246. · 2.72 Impact Factor
• Article: Organic globules in the Tagish Lake meteorite: remnants of the protosolar disk.

  Keiko Nakamura-Messenger, Scott Messenger, Lindsay P Keller, Simon J Clemett, Michael E Zolensky
  [show abstract] [hide abstract]
  ABSTRACT: Coordinated transmission electron microscopy and isotopic measurements of organic globules in the Tagish Lake meteorite shows that they have elevated ratios of nitrogen-15 to nitrogen-14 (1.2 to 2 times terrestrial) and of deuterium to hydrogen (2.5 to 9 times terrestrial). These isotopic anomalies are indicative of mass fractionation during chemical reactions at extremely low temperatures (10 to 20 kelvin), characteristic of cold molecular clouds and the outer protosolar disk. The globules probably originated as organic ice coatings on preexisting grains that were photochemically processed into refractory organic matter. The globules resemble cometary carbon, hydrogen, oxygen, and nitrogen (CHON) particles, suggesting that such grains were important constituents of the solar system starting materials.
  Science 01/2007; 314(5804):1439-42. · 31.20 Impact Factor
• Source

  Available from: Marc Fries

  Article: Organics captured from comet 81P/Wild 2 by the Stardust spacecraft.

  Scott A Sandford, Jérôme Aléon, Conel M O'd Alexander, Tohru Araki, Sasa Bajt, Giuseppe A Baratta, Janet Borg, John P Bradley, Donald E Brownlee, John R Brucato, [......], Andrew Steele, Thomas Stephan, Peter Tsou, Tolek Tyliszczak, Andrew J Westphal, Sue Wirick, Brigitte Wopenka, Hikaru Yabuta, Richard N Zare, Michael E Zolensky
  [show abstract] [hide abstract]
  ABSTRACT: Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.
  Science 01/2007; 314(5806):1720-4. · 31.20 Impact Factor
• Source

  Available from: Koen Janssens

  Article: Elemental compositions of comet 81P/Wild 2 samples collected by Stardust.

  George J Flynn, Pierre Bleuet, Janet Borg, John P Bradley, Frank E Brenker, Sean Brennan, John Bridges, Don E Brownlee, Emma S Bullock, Manfred Burghammer, [......], Peter Tsou, Akira Tsuchiyama, Kentaro Uesugi, Bart Vekemans, Edward P Vicenzi, Laszlo Vincze, Andrew J Westphal, Penelope Wozniakiewicz, Ernst Zinner, Michael E Zolensky
  [show abstract] [hide abstract]
  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 ( approximately 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.
  Science 01/2007; 314(5806):1731-5. · 31.20 Impact Factor
• Article: Mineralogy and petrology of comet 81P/Wild 2 nucleus samples.

  Michael E Zolensky, Thomas J Zega, Hajime Yano, Sue Wirick, Andrew J Westphal, Mike K Weisberg, Iris Weber, Jack L Warren, Michael A Velbel, Akira Tsuchiyama, [......], Miaofang Chi, Anna L Butterworth, Donald E Brownlee, John C Bridges, Sean Brennan, Adrian Brearley, John P Bradley, Pierre Bleuet, Phil A Bland, Ron Bastien
  [show abstract] [hide abstract]
  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.
  Science 01/2007; 314(5806):1735-9. · 31.20 Impact Factor
• Article: Preliminary examination of the comet Wild 2 samples returned by the Stardust spacecraft

  Michael E. Zolensky, Donald E. Brownlee, Peter Tsou, Friedrich P. Hörz, Scott A. Sandford, George J. Flynn, Kevin D. McKeegan, Lindsay P. Keller
  [show abstract] [hide abstract]
  ABSTRACT: Results of the Stardust mission to sample dust from comet Wild 2 are summarized.
  Proceedings of the International Astronomical Union 07/2006; 2:327 - 328.