Now showing items 1-20 of 199

    • From the Editors: Logos and special publications for the Society

      Sears, Derek (The Meteoritical Society, 2002-12-01)
    • From the Editors: Chondrules and nebular shocks

      Chiang, E. I. (The Meteoritical Society, 2002-01-01)
    • Geochemistry of the ungrouped carbonaceous chondrite Tagish Lake, the anomalous CM chondrite Bells, and comparison with CI and CM chondrites

      Mittlefehldt, David W.; Killgore, Marvin; Lee, Michael T. (The Meteoritical Society, 2002-01-01)
      I have determined the composition via INAA of a bulk pristine sample of the Tagish Lake carbonaceous chondrite fall, along with bulk samples of the CI chondrite Orgueil and of several CM chondrites. Tagish Lake has a mean of refractory lithophile element/Cr ratios like those of CM chondrites, and distinctly higher than the CI chondrite mean. Tagish Lake exhibits abundances of the moderately volatile lithophile elements Na and K that are slightly higher than those of mean CM chondrites. Refractory through moderately volatile siderophile element abundances in Tagish Lake are like those of CM chondrites. Tagish Lake is distinct from CM chondrites in abundances of the most volatile element. Mean CI-normalized Se/Co, Zn/Co and Cs/Co for Tagish Lake are 0.68 +/- 0.01, 0.71 +/- 0.07 and 0.76 +/- 0.02, while for all available CM chondrite determinations, these ratios lie between 0.31-0.61, 0.32-0.58 and 0.39-0.74, respectively. Considering petrography, and oxygen isotopic and elemental compositions, Tagish Lake is an ungrouped member of the carbonaceous chondrite clan. The overall abundance pattern is similar to those of CM chondrites, indicating that Tagish Lake and CMs experienced very similar nebular fractionations. Bells is a CM chondrite with unusual petrologic characteristics. Bells has a mean CI-normalized refractory lithophile element/Cr ratio of 0.96, lower than for any other CM chondrite, but shows CI-normalized moderately volatile lithophile element/Cr ratios within the ranges of other CM chondrites, except for Na which is low. Iridium, Co, Ni and Fe abundances are like those of CM chondrites, but the moderately volatile siderophile elements, Au, As and Sb, have abundances below the ranges for CM chondrites. Abundances of the moderately volatile elements Se and Zn of Bells are within the CM ranges. Bells is best classified as an anomalous CM chondrite.
    • From the Editors: Heavy noble gases in solar system matter

      Marti, K. (The Meteoritical Society, 2002-01-01)
    • A "mesosiderite" rock from northern Siberia, Russia: Not a meteorite

      Treiman, A. H.; Lindstrom, D. J.; Schwandt, C. S.; Franchi, I. A.; Morgan, M. L. (The Meteoritical Society, 2002-12-01)
      A possible mesosiderite meteorite was found in the area of the Putorana Plateau, Noril'sk district, Siberia, Russia. Although this rock resembles a mesosiderite in its hand-sample aspect and in having Ni-bearing iron metal, it is not a meteorite. This inference is based on the lack of a fusion crust, the lack of cosmogenic nuclides, oxygen with terrestrial isotope ratios, and several mineral chemical criteria. Most likely, the rock is from the iron-metal-bearing basalts of the Siberian Trap basalt sequence, which are mined for their base and platinum-group metals. Mesosiderite imposters like this may be recognized by (1) the presence of Cu metal in hand sample or as microscopic blebs in the low-Ni metal (kamacite), (2) the absence ofhigh-Ni metal (taenite), and (3) the presence of iron carbide (cohenite) enclosing the kamacite. Even if these macroscopic tests are inconclusive, isotopic and mineral chemical tests will also distinguish rocks like this from mesosiderites.
    • The Worden meteorite: A new ordinary chondrite fall from Michigan, USA

      Vebel, M. A.; Matty, D. J.; Wacker, J. F.; Linke, Matt P. (The Meteoritical Society, 2002-12-01)
      An ordinary chondrite fall in southeast Michigan, USA (near the crossroads hamlet of Worden in northeast Washtenaw County) penetrated the garage roof of a private home on 1997 September 1. The Worden chondrite comprises silicate matrix, mineral fragments, chondrules, chondrule fragments, and opaque primary phases. Electron microprobe analyses (olivine, Fa23.9; orthopyroxene, FS20.1, En78.8, W01) indicate diagnostic L-chondrite silicate mineral compositions. Recognizable chondrules and chondrule fragments constitute up to 42 vol%. Chondrule boundaries are readily discernable (especially where chondrules have rims of opaque material) but not sharp, and discrete plagioclase crystals are visible in the devitrified mesostasis of barred olivine chondrules; together, these characteristics suggest petrologic type S. The spatially averaged ensemble of shockrelated features (optical extinction of olivine grains, minor localized shock melt) suggests assignment of a shock stage of S3. The 26 Al and 22Na activities are typical for an L chondrite. Worden fell near the most recent solar minimum in 1997, and the 22Na production rate should have been at a level approaching the maximum levels due to solar modulation of the galactic cosmic-ray flux. The low value for the Worden 22Na activity relative to those observed in chondrite falls associated with the 1969 solar maximum and 1976 solar minimum suggests a relatively small preatmospheric size. The 60Co activity confirms the indication of a small body. The 56Co activity was essentially zero, indicating that none of the recovered meteorite contained material exposed to solar cosmic rays. The Worden chondrite is the fourth documented fall in Michigan, and the fourth stony meteorite recovered in Michigan; all other Michigan meteorites are finds, not observed falls, and are iron meteorites. All Michigan falls to date are ordinary chondrites. The three falls prior to Worden were Allegan (HS) fell 1899; Rose City (HS, brecciated, black (dark matrix)) fell 1921 ; and Coleman (L6, veined (shocked); Osborn et aI., 1997) fell 1994. Worden has a much lighter matrix than Rose City, and is less extensively thermally and shock metamorphosed than either Rose City (StOffler et aI., 1991) or Coleman.
    • The Third International Conference on Magnetism, Metamorphism and Associated Mineralizations "3MA", Casablanca, Morocco 2003 May 8-10

      The Meteoritical Society, 2002-01-01
      Announcement: The Third International Conference on Magnetism, Metamorphism and Associated Mineralizations "3MA"
    • The Dar al Gani meteorite field (Libyan Sahara): Geological setting, pairing of meteorites, and recovery density

      Schlüter, J.; Schultz, L.; Thiedig, F.; Al-Mahdi, B. O.; Abu Aghreb, A. E. (The Meteoritical Society, 2002-01-01)
      As of July 2001, 1238 Libyan meteorites have been reported. Most were found in two areas called Dar al Gani and Hamadah al Hamra. Dar al Gani is located on a plateau of marine carbonate rocks with marly components. Eight-hundred and sixty-nine meteorites between 6 g and 95 kg totalling 687 kg have been found here but the calculated mean recovery density is comparatively low with one meteorite on 6.5 km2. Dar al Gani is a perfect site for the recognition and preservation of meteorites. The existence of meteorites is the result of a combination of specific geological and geomorphological conditions: there is a bright-colored, old limestone plateau (<2 Ma), under arid weather, conditions over long periods of time, with rapid elimination of surface water if present and low erosion rates. The preservation of meteorites is guaranteed through the absence of quartz sand on the plateau, strongly reducing wind erosion and a basic environment emerging from the carbonate ground retards rusting of metallic meteorite components. A supposed soil cover during pluvial times has probably protected older meteorites and led to a concentration of meteorites of different periods. An evaluation of Dar al Gani meteorites suggests the existence of at least 26 strewnfields and 26 meteorite pairs reducing the number of falls to, at most, 534. Shock and weathering grades as a tool for the recognition of pairings turned out to be problematic, as several strewnfields showed paired meteorites which had been classified to different shock and weathering grades.
    • Discovery of an asteroid and quasi-satellite in an Earth-like horseshoe orbit

      Connors, M.; Chodas, P.; Mikkola, S.; Wiegert, P.; Weillet, C.; Innanen, K. (The Meteoritical Society, 2002-01-01)
      The newly discovered asteroid 2002 AA29 moves in a very Earth-like orbit that relative to Earth has a unique horseshoe shape and allows transitions to a quasi-satellite state. This is the first body known to be in a simple heliocentric horseshoe orbit, moving along its parent planet's orbit. It is similarly also the first true co-orbital object of Earth, since other asteroids in 1:1 resonance with Earth have orbits very dissimilar from that of our planet. When a quasi-satellite, it remains within 0.2 AU of the Earth for several decades. 2002 AA29 is the first asteroid known to exhibit this behavior. 2002 AA29 introduces an important new class of objects offering potential targets for space missions and clues to asteroid orbit transfer evolution.
    • Yamato 792947,793408 and 82038: The most primitive H chondrites, with abundant refractory inclusions

      Kimura, M.; Hiyagon, H.; Palme, H.; Spettel, B.; Wolf, D.; Clayton, R. N.; Mayeda, T. K.; Sato, T.; Suzuki, A.; Kojima, H. (The Meteoritical Society, 2002-01-01)
      In this paper we report petrological and chemical data of the unusual chondritic meteorites Yamato (Y)-792947, Y-93408 and Y-82038. The three meteorites are very similar in texture and chemical composition, suggesting that they are pieces of a single fall. The whole-rock oxygen isotopes and the chemical compositions are indicative ofH chondrites. In addition, the mineralogy, and the abundances of chondrule types, opaque minerals and matrices suggest that these meteorites are H3 chondrites. They were hardly affected by thermal and shock metamorphism. The degree of weathering is very low. We conclude that these are the most primitive H chondrites, H3.2-3.4 (SI), known to date. On the other hand, these chondrites contain extraordinarily high amounts of refractory inclusions, intermediate between those of ordinary and carbonaceous chondrites. The distribution of the inclusions may have been highly heterogeneous in the primitive solar nebula. The mineralogy, chemistry and oxygen isotopic compositions of inclusions studied here are similar to those in CO and E chondrites.
    • Meteoritical Society Business

      The Meteoritical Society, 2002-12-01
    • The meteorite collection of the National Museum of Natural Sciences, Madrid, Spain: An updated catalog

      Muñoz-Espadas, M. J.; Martínez-Frías, J.; Lunar, R.; Sánchez, B.; Sánchez, J. (The Meteoritical Society, 2002-12-01)
      A catalog of the meteorite collection hosted by the National Museum of Natural Sciences of Madrid is presented. It includes 88 stony meteorites, 56 iron meteorites, and 13 stony-iron meteorites, as well as 14 tektites.
    • Oral histories in meteoritics and planetary science: VIII. Friedrich Begemann

      Marvin, Ursula B. (The Meteoritical Society, 2002-12-01)
      In this interview, taped in 2001 during The Meteoritical Society meeting in Rome, Friedrich Begemann recalls that after he earned his doctorate in physics under the direction of Professor Friedrich G. Houtermans, first in Göttingen and then in Bern, Switzerland, he began his career as what he calls a low-level gas counting man, specializing in tritium (3H). In 1954 he accepted an invitation from Professor Willard F. Libby to run his gas-counting laboratory at the University of Chicago. Begemann spent 3 years there during which he traced the distribution in the world's atmosphere and waters of tritium from two sources, natural cosmic radiation and the detonation of the first thermonuclear device. During his time at Chicago he was drawn into Harold C. Urey's group of scientists studying meteorites. Begemann found that he could measure tritium in meteorites, and by coupling his values with those of 3He, he and his collaborators initiated a new branch of meteoritics by determining the first cosmic-ray exposure age of a meteorite--Norton County, which fell in 1947. In 1957, Begemann joined the group led by Friedrich A. Paneth at the Max-Planck-Institute für Chemie at Mainz, Germany, where he continued his studies of gas isotopes for the remainder of his career. His research led to the discovery of primitive noble gases in the diamond-graphite aggregates in ureilites, where their presence in presumably deep-seated igneous rocks still remains to be explained. With the advent of the Apollo missions, Begemann extended his studies to the lunar rocks and soils in an effort to learn as much as possible about the interaction of solids with the space environment. He also became heavily involved in measuring the s-process isotope abundance patterns of medium-heavy chemical elements as they occur in interstellar grains. In 1995 at the meeting in Washington, D.C., The Meteoritical Society presented Friedrich Begemann with the Leonard Medal for his contributions to our understanding of the radiation encountered by bodies as they orbit through space.
    • The meteorite collection of the Civico Planetario and the Museo Civico di Storia Naturale in Milan, Italy

      Folco, Luigi; Peri, Fabio; Pezzotta, Federico (The Meteoritical Society, 2002-12-01)
      The historical meteorite collection of Milan's Civico Planetario and Museo di Storia Naturale is presented in this catalogue. Started in 1838, the collection contains to date (March 2002) 231 samples of 77 individual falls, representing 118.935 kg (i.e., the total weight is 118 kg and 935 g) of extraterrestrial material, including 5 carbonaceous chondrites, 38 ordinary chondrites, 3 achondrites, 7 stony-iron meteorites and 24 iron meteorites.
    • Oral histories in meteoritics and planetary science: IX. Heinrich Wänke

      Marvin, Ursula B. (The Meteoritical Society, 2002-12-01)
      In this interview, Heinrich Wänke, a nuclear physicist, describes how he first encountered meteorite studies in 1953 when, after finishing his Ph.D. thesis in Vienna, he joined the research group of Professor Friedrich Paneth at the University of Durham, England. There, he worked on problems relating to uranium-helium ages of iron meteorites. A year later, Wänke moved with Paneth to the Max-Planck-Institut für Chemie at Mainz in Germany. He continued meteorite research but also conducted experiments to measure noble gases in the stratosphere, a project that brought him to America in 1956 where he first met Professor Harold C. Urey, with whom he formed a lasting friendship. After Paneth's early death in 1958, Wänke remained at the Institute in Mainz and pursued research on topics such as the isotopic compositions of cosmogenic noble gases in iron meteorites and the abundances of primordial rare gases implanted by solar wind particles in brecciated stony meteorites. In 1969, Wänke was appointed to fill Paneth's position as a director as the Max-Planck-Institut für Chemie just in time for him to lead a wide spectrum of research projects on the lunar rocks and soils. Froom the geochemical evidence these studies provided, he theorized on the formation of the Moon by the giant impact hypothesis, and proposed a two-component model for the cosmic composition of the Earth's mantle. His group also investigated the isotopic chemistry of martian meteorites and its hearing on the origin and evolution of Mars, which he viewed as a cored planet that underwent early differentiation without subsequent convective homogenization. In 1980, the Meteoritical Society awarded the Leonard Medal to Heinrich Wänke for his numerous contribution of fundamental importance to meteoritics and planetary science.
    • The law of ownership and control of meteorites

      Schmitt, Douglas G. (The Meteoritical Society, 2002-12-01)
      Increased commerce in meteorites raises questions about their ownership and control. This article reviews the law in several countries, international law, and considers the legal and ethical issues facing curators wanting to bring finds to the research community and not divert them to a black market. A survey was made of scientists involved in meteorite acquisition in over 20 countries to determine how well various systems work. Meteorite ownership law is non-uniform. English Common Law, from which the law in former British colonies including the United States evolved, provides that meteorites are the landowner's property; buried meteorites might be part of the mineral rights. Find reporting that is not mandatory. Most Western European countries, and former colonies, have civil codes providing that meteorites are owned by the landowner. In many countries legislation about archaeological treasures modifies earlier meteorite law. The UNESCO Convention on the Means of Prohibiting and Preventing the Illicit Import, Export and Transfer of Ownership of Cultural Property provides for tracking and retrieving from reciprocating states, cultural property including meteorites. The Antarctic Treaty does not deal with samples exported. In July 2001 the Antarctic Treaty Consultative parties adopted a resolution to discourage non-scientific collection. Curators should exercise caution if acquiring specimens of questionable legal ownership. Governments should be urged to enact laws to (1) discourage non-scientific collection in pristine areas; (2) encourage collection in populated areas by reasonable incentives to finders, with mandatory find reporting; (3) create efficient export permitting systems allowing exchange of research samples; and (4) retrieve illegally exported meteorites under the UNESCO Cultural Property Convention.
    • Oral histories in meteoritics and planetary science: VII. Alastair G. W. Cameron

      Marvin, Ursula B. (The Meteoritical Society, 2002-12-01)
      In this interview, Alastair Cameron reecounts how he started his career as a nuclear physicist but taught himself astrophysics after he read a paper that required an astrophysical explanation for the presence of technetium in red giant stars. Subsequently, as new analytical data became available, he periodically updated the Suess-Urey tables of elemental abundances to enhance the value of the systematic approach they provided to understanding the individual processes of nucleosysthesis. Since many of these new data were based on analyses of carbonaceous chondrites, he taught himself meteoritics. In recent decades, Cameron has focused his research interests on problems such as the provenance of certain components of meteorites (calcium-aluminum-rich inclusions, FUN (fractionated and unknown nuclear) anomalous inclusions, amoeboid olivine aggregates, and presolar grains) that he believes to have formed in the supernova envelope prior to formation of the solar nebula, the origin of chondrules in the primitive solar nebula, and the origins of the solar system and of the Earth-Moon system. To investigate these subjects he has pioneered the use of advanced computer technology to make lengthy calculations of nucleosysthesis in complicated networks. After teaching courses and advising graduate students at several research institutes and colleges, Cameron served as a Professor of Astronomy at Harvard University from 1973 to 1997 when he was appoinetd to the Donald H. Menzel Research Professorship of Astrophysics. In 1994, The Meteoritical Society honored him with the Leonard Medal at its meeting in Prague, the Czech Republic.
    • One meteorite less from Vietnam

      Rochette, P. (The Meteoritical Society, 2002-12-01)
      Among the four declared meteorites from Vietnam, the two most recent ones--Phuoc-Binh (1941) and Fuc Bin (1971)--appear to be the same, following a visit to the Hanoi museum and an analysis of the literature. Phuoc-Binh (L5) with a fall date of 1941 July 18 should be the correct entry.