Meteoritic Origin Research Articles

Laboratory experiments of crater formation on ice–silicate mixture targets

Water ices exist mostly in a variety of forms of mixtures with silicate or some other components (e.g., ammonia) in the solar system. Thus, it is of importance to understand the impact process on ice–silicate mixtures. We performed impact experiments on ice–silicate mixture target using a gas gun and a two-stage light-gas gun in a cold room at 263 K in the Institute of Low Temperature, Hokkaido University. Silicate content of the target was varied from 0 to 50 wt%. Targets were 10 or 30 cm in diameter, and 5 cm in height. Projectile velocity was varied between 299 and 657 m/s and projectile mass was 1.6 g for the gas gun shot, and 1480 and 3684 m/s and 7 mg for the two-stage light-gas gun. Crater morphology changes with silicate content and impact velocity: craters formed on targets of 50 wt% silicate content had less spallation than those with the other silicate content and crater profiles at higher impact velocity became sharper than those at lower impact velocity. Although diameter-to-depth ratio is not dependent on silicate content of the target, this ratio became large at low peak pressure for the gas gun shots. This is probably because of accretion of pure ice projectile onto the target surface. The decrease of crater volume with increasing silicate content was visible for the results from the two-stage light-gas gun. We estimated the target tensile strength based on a hydrodynamic ejection model of [Melosh, H.J. Impact ejection, spallation, and the origin of meteorites. Icarus, 59, 234–260, 1984]. The ejection model predicts a relation between target tensile strength, spall fragment thickness and ejection point. If a constant shock attenuation rate is assumed for all the ice–silicate mixture targets, the tensile strength derived for the mixture with 50 wt% rock content turns out to be higher than the pure ice by a factor of 2 or more.

The rayed crater Zunil and interpretations of small impact craters on Mars

A 10-km diameter crater named Zunil in the Cerberus Plains of Mars created ∼ 10 7 secondary craters 10 to 200 m in diameter. Many of these secondary craters are concentrated in radial streaks that extend up to 1600 km from the primary crater, identical to lunar rays. Most of the larger Zunil secondaries are distinctive in both visible and thermal infrared imaging. MOC images of the secondary craters show sharp rims and bright ejecta and rays, but the craters are shallow and often noncircular, as expected for relatively low-velocity impacts. About 80% of the impact craters superimposed over the youngest surfaces in the Cerberus Plains, such as Athabasca Valles, have the distinctive characteristics of Zunil secondaries. We have not identified any other large (⩾10 km diameter) impact crater on Mars with such distinctive rays of young secondary craters, so the age of the crater may be less than a few Ma. Zunil formed in the apparently youngest (least cratered) large-scale lava plains on Mars, and may be an excellent example of how spallation of a competent surface layer can produce high-velocity ejecta (Melosh, 1984, Impact ejection, spallation, and the origin of meteorites, Icarus 59, 234–260). It could be the source crater for some of the basaltic shergottites, consistent with their crystallization and ejection ages, composition, and the fact that Zunil produced abundant high-velocity ejecta fragments. A 3D hydrodynamic simulation of the impact event produced 10 10 rock fragments ⩾10 cm diameter, leading to up to 10 9 secondary craters ⩾10 m diameter. Nearly all of the simulated secondary craters larger than 50 m are within 800 km of the impact site but the more abundant smaller (10–50 m) craters extend out to 3500 km. If Zunil is representative of large impact events on Mars, then secondaries should be more abundant than primaries at diameters a factor of ∼1000 smaller than that of the largest primary crater that contributed secondaries. As a result, most small craters on Mars could be secondaries. Depth/diameter ratios of 1300 small craters (10–500 m diameter) in Isidis Planitia and Gusev crater have a mean value of 0.08; the freshest of these craters give a ratio of 0.11, identical to that of fresh secondary craters on the Moon (Pike and Wilhelms, 1978, Secondary-impact craters on the Moon: topographic form and geologic process, Lunar Planet. Sci. IX, 907–909) and significantly less than the value of ∼0.2 or more expected for fresh primary craters of this size range. Several observations suggest that the production functions of Hartmann and Neukum (2001, Cratering chronology and the evolution of Mars, Space Sci. Rev. 96, 165–194) predict too many primary craters smaller than a few hundred meters in diameter. Fewer small, high-velocity impacts may explain why there appears to be little impact regolith over Amazonian terrains. Martian terrains dated by small craters could be older than reported in recent publications.

L'œuvre minéralogique et pétrographique des pharmaciens du Muséum

Three famous pharmacists were working in the Muséum national d'histoire naturelle in Paris, in the field of earth sciences: Louis Nicolas Vauquelin (1763-1829), André Laugier (1770-1832) and Alfred Lacroix (1863-1948). Vauquelin, professor of Chemical arts, established the chemical composition of numerous minerals, which led him to the discovery of new chemical elements. He also took a hand in demonstrating the extra-terrestrial origin of meteorites. Laugier, professor of General chemistry, was an admitted expert in the analytical field of these rocks. Lacroix, who held during more than forty years the chair of Mineralogy in the Museum, carried out major scientific work. This field working naturalist who was also famous vulcanologist placed his studies of the mineral species into a petrographical context. He described numerous new minerals, took an interest in their origin and classification of the volcanic rocks, as well as in contact metamorphism. In other respects, he increased the collections in the Museum (minerals, rocks, meteorites). The works of Vauquelin, Laugier and Lacroix contributed to advance those begun by some scientists of the Jardin du Roi, as Buffon or the Rouelle brothers before the French Revolution.

Study of solar system planetary lightning with LOFAR

Radio signatures of lightning discharges have been detected by the Voyager spacecraft near Saturn and Uranus up to 40 MHz. Corresponding flux densities at the distance of the Earth are up to 1000 Jansky (Jy) for Saturn (⩾1 event per minute above 50 Jy, with 30–300 ms duration) and up to a few tens of Jansky for Uranus. Low Frequency ARray LOFAR will allow us to detect and monitor the lightning activity at these two planets. Imaging will allow us to locate lightning sources on Saturn's disk (even if with moderate accuracy), which could then be correlated to optical imaging of clouds. Such observations could provide new information on electrification processes, atmospheric dynamics, composition, and geographical and seasonal variations, compared to the Earth. In addition, lightning may play a role in the atmospheric chemistry, through the production of non-equilibrium trace organic constituents potentially important for biological processes. LOFAR observations can also help us to assess the existence of lightning at Neptune (marginally detected by Voyager), at Venus (where their existence is very controversial), and at Mars (possibly resulting from dust cloud charging). At Jupiter, low-altitude ionospheric layers of meteoritic origin and/or intrinsically long discharge duration seem to prevent the emission and escape of high-frequency radio waves associated with lightning. LOFAR thus presents good possibilities for the detection and study of solar system planetary lightning; we also discuss its relevance to bring new information on Terrestrial lightning-related upper atmosphere transient phenomena (sprites, TIPPs…). Instrumental constraints are outlined.

Evidence for asteroid space weathering from the Sloan Digital Sky Survey

By studying color variations between young and old asteroid families we find evidence for processes that modify colors of asteroids over time. We show that colors of aging surfaces of S-type asteroids become increasingly ‘redder’ and measure the rate of these spectral changes. We estimate that the mean spectral slope between 0.35 and 0.9 μm increases with time t (given in My) as ≈ 0.01 μm −1 × log 10 t . This empirical fit is valid only for 2.5 ≲ t ≲ 3000 My (the time interval where we have data) and for the mean spectral slope determined from wide-wavelength filter photometry obtained by the Sloan Digital Sky Survey. We also find that Gy-old terrains of S-type asteroids reflect about 15% more light at ∼1-μm wavelengths than an ∼5-My-old S-type asteroid surface when the flux is normalized by the reflected light at 0.55 μm. We attribute these effects to space weathering. This result has important implications for asteroid geology and the origin of meteorites that reach the Earth. Our results also suggest that surfaces of C-type asteroids exhibit color alterations opposite to those of the S-type asteroids.

The origin and evolution of stony meteorites

The origin of stony meteorites landing on Earth today is directly linked to the history of the main belt, which evolved both through collisional evolution and dynamical evolution/depletion. In this paper, we focus our attention on the main belt dynamical evolution scenario discussed in Petit et al. (2001). According to Petit et al., during the planet formation epoch, the primordial main belt contained several Earth masses of material, enough to allow the asteroids to accrete on relatively short timescales.After a few My, the accretion of planetary embryos in the main belt zone dynamically stirred the remaining planetesimals to high enough velocities to initiate fragmentation. After a short interval, perhaps as long as 10 My, the primordial main belt was dynamically depleted of % of its material via the combined perturbations of the planetary embryos and a newly-formed Jupiter. The small percentage of objects that survived in the main belt zone became the asteroid belt. It has been shown that the wavy-shaped size-frequency distribution of the main belt is a “fossil” left over from this violent period (Bottke et al. 2004).Using a collisional/dynamical model of this scenario, we tracked the evolution of stony meteoroids produced by catastrophic disruption events over the last several Gy. We show that most stony meteoroids are a byproduct of a collisional cascade derived from large and ancient asteroid families or smaller, more recent breakup events. The meteoroids are then delivered to Earth by drifting in semimajor axis via Yarkovsky thermal drag forces until they reach a resonance powerful enough to place them on an Earth-crossing orbit.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The age of the Kaali meteorite craters and the effect of the impact on the environment and man: evidence from inside the Kaali craters, island of Saaremaa, Estonia

The Kaali meteorite impact crater field, which consists of a 110 m diameter main crater and eight satellite craters on the island of Saaremaa, Estonia is a unique object as its meteoritic origin is well proven, it lies in a densely populated area and fell in the relatively recent past. The precise age of the impact that generated the craters is still disputed. We investigated the basal sediment section from the main crater lake, Kaali jrv, consisting of crushed and in-washed dolomite diamiction. AMS dating of terrestrial macrofossils from these sediment layers places the age of the impact at 1690�1510 B.C. The age is about 1000 years older than revealed from the impact marker-horizon in a contemporaneous peat sequence 6 km northwest of the Kaali crater. The pollen, diatom and chemical data suggest the instant formation of a shallow hard-water lake environment in the main crater depression after the impact, and a rapid post-impact sedimentation of crushed dolomite dust. Archaeological evidence on the crater slopes points to human activity around 700- 200 B.C., indicating that the crater ring wall was inhabited by Bronze Age people soon after the impact event, and the structure of the main crater is mimicked in nearby ar- chaeological sites.

Experimental constraints on the origin of Martian meteorites and the composition of the Martian mantle

The major element compositions of partial melts of a chondritic (Homestead L5) model Mars mantle have been determined at 4.7–5.0 GPa in a multi-anvil device over a temperature interval that ranged from near solidus to near liquidus conditions. The purpose of these experiments is to determine if the major element abundances of Martian basalts (shergottite meteorites) or their parent magmas can be derived from a model Martian mantle composition at high pressure. Partial melting of our model composition at 4.7–5.0 GPa produces liquids with super-chondritic CaO/Al 2O 3 similar to those of proposed Martian basalt parent magmas. The concentrations of CaO and Al 2O 3 in the high-pressure experimental liquids are, however, lower than in Martian basalt parent magmas. We conclude that matches for both ratios and concentrations involving CaO and Al 2O 3 between current model Mars compositions and proposed Martian basalt parent magmas would require at least two stages of magmatic differentiation. For example, partial melting at 5 GPa (425 km depth in Mars) produces a magma having super-chondritic CaO/Al 2O 3, but subsequent, lower pressure differentiation of olivine (±low-Ca pyroxene) is needed to increase the CaO and Al 2O 3 concentrations to those of calculated Martian basalt parent magmas. This two-stage polybaric differentiation would be consistent with either a magma ocean or mantle plume-melting scenario. On the other hand, these multi-stage differentiation scenarios cannot reconcile the significant mismatch between the FeO content of our experimental liquids and Martian basalt parent magmas. A remedy for this apparent inconsistency might require a bulk Martian mantle or shergottite parent source region with a composition and Mg# closer to that of H-chondrites, but still much less magnesian than are terrestrial upper-mantle basalt source regions.

HYDROGEOCHEMICAL CONDITION OF THE PIKROLIMNI LAKE (KILKIS GREECE)

In order to understand the hydrogeochemical conditions of the basin of Pikrolimni we collected water samples from the borehole in the thermal spa of Pikrolimni and samples of brine and sediments from the lake. We also sampled fresh water of the region. The depth of the borehole in the thermal spa is approximately 250 meters. This water is naturally sparkling, with a metallic aftertaste and a slight organic smell. The samples were taken twice during the year: in summer (8/2002) and in winter (2003). The analytical scheme includes field measurements of temperature, conductivity and pH. Major ions (Na+, K+, Ca2+, Mg2\ CI", Br, S04 2", C03 2", HC03", N03"), F and Br were determined, in laboratory, according to standard analytical methods. Samples were also subjected to isotopie analysis of δ Ο and δ2Η. The results from the chemical analyses of the samples, show that the waters taken from the borehole, are of the type Mg- (Na-Ca)-HCC>3 and the salts of the lake are of the type Na-CI- (CO3-S04). The salts of the lake result from mixing and condensation of the waters which are accumulated in the basin of the lake, and come not only from sources that feed the lake, e.g. waters from borehole, but also from rain water. The waters of these sources are mainly of meteoritic origin and circulate deeply, mixing probably with salt water of deeper and probably of warmer horizons. The latter comes in agreement with the hydrothermal field, which exists in the area. From hydrochemical data, the brines of summer clearly correspond to waters, which have been submitted under high degree of evaporation: they are residual mother solutions before the step of the precipitation of halite. During winter, dilution of brines and dissolution of depositing minerals by fresh water are observed. On the other hand, evaporating conditions are created in the lake during summer.

A petrogenetic model for the origin and compositional variation of the martian basaltic meteorites

Abstract— The major element, trace element, and isotopic compositional ranges of the martian basaltic meteorite source regions have been modeled assuming that planetary differentiation resulted from crystallization of a magma ocean. The models are based on low to high pressure phase relationships estimated from experimental runs and estimates of the composition of silicate Mars from the literature. These models attempt to constrain the mechanisms by which the martian meteorites obtained their superchondritic CaO/Al2O3 ratios and their source regions obtained their parent/daughter (87Rb/86Sr, 147Sm/144Nd, and 176Lu/177Hf) ratios calculated from the initial Sr, Nd, and Hf isotopic compositions of the meteorites. High pressure experiments suggest that majoritic garnet is the liquidus phase for Mars relevant compositions at or above 12 GPa. Early crystallization of this phase from a martian magma ocean yields a liquid characterized by an elevated CaO/Al2O3 ratio and a high Mg#. Olivine‐pyroxene‐garnet‐dominated cumulates that crystallize subsequently will also be characterized by superchondritic CaO/Al2O3 ratios. Melting of these cumulates yields liquids with major element compositions that are similar to calculated parental melts of the martian meteorites. Furthermore, crystallization models demonstrate that some of these cumulates have parent/daughter ratios that are similar to those calculated for the most incompatible‐element‐depleted source region (i.e., that of the meteorite Queen Alexandra [QUE] 94201).The incompatible‐element abundances of the most depleted (QUE 94201‐like) source region have also been calculated and provide an estimate of the composition of depleted martian mantle. The incompatible‐element pattern of depleted martian mantle calculated here is very similar to the pattern estimated for depleted Earth's mantle. Melting the depleted martian mantle composition reproduces the abundances of many incompatible elements in the parental melt of QUE 94201 (e.g., Ba, Th, K, P, Hf, Zr, and heavy rare earth elements) fairly well but does not reproduce the abundances of Rb, U, Ta and light rare earth elements. The source regions for meteorites such as Shergotty are successfully modeled as mixtures of depleted martian mantle and a late stage liquid trapped in the magma ocean cumulate pile. Melting of this hybrid source yields liquids with major element abundances and incompatible‐element patterns that are very similar to the Shergotty bulk rock.

On search and identification of relatively short-lived superheavy nuclei (Z ≥ 110) by fossil track studies of meteoritic and lunar olivine crystals

The main goal of the present work is the search for and identification of relatively stable nuclei of superheavy elements (SHE) (Z>110) in galactic matter by fossil track study of nonconducting crystals from the surface of meteorites and rocks from the lunar regolith. Nuclei of SHE are thought to be the products of nucleosynthesis in explosive processes in our Galaxy (supernova r-process nucleosynthesis and, especially, neutron-star formation, etc.). When accelerated to relativistic energies in the Galaxy, they can produce extended trails of damage in nonconducting extraterrestrial crystals. The lifetime of such SHE in galactic cosmic rays will range from 103 to 107 yr to be registered in extraterrestrial crystals. To search for and to identify the superheavy nuclei in the galactic cosmic rays, it was proposed to use the ability of nonconducting extraterrestrial crystals such as olivines, pyroxenes, and feldspars to detect and to store for many millions of years the trails of damage produced by fast Z≥23 nuclei coming to rest in the crystalline lattice. The track lengths of fast Z≥23 nuclei are directly proportional to Z2 of these nuclei. The nuclei of SHE produce, when coming to rest in a crystal volume, tracks that are a factor of 1.6–1.8 longer than the tracks due to cosmic-ray Th and U nuclei. To identify the tracks due to superheavy nuclei, calibrations of the same crystals were performed with accelerated Au, Pb, and U nuclei. For visualization of these tracks inside the crystal volume, proper controlled annealing and chemical etching procedures were developed. Since 1980, fossil tracks due to Th and U nuclei have observed and unambiguously identified (1988) by subsequent calibrations of the olivine crystals with accelerated U, Au, and Pb ions. The number of tracks of Th and U nuclei measured in olivine crystals totaled more than 1600, as compared with the prior 30 events. The other approach to identifying SHE in nature is to search for tracks in phosphate crystals from spontaneous fission of Z ≥ 110 nuclei; these produce two-prong and three-prong fission fragment tracks and differ significantly from the tracks from spontaneous fission of 238U and 244Pu nuclei. Extraterrestrial phosphate crystals of lunar and meteoritic origin will be investigated. Such SHE nuclei can survive in crystals of extraterrestrial rocks and produce spontaneous fission tracks, if the lifetime is more than 5×107 yr.

The Origin and Significance of Antarctic Meteorites

Abstract More than 25,000 meteorite specimens have been recovered from Antarctica since systematic collection programs began in the mid 1970's. When properly recovered and curated, these specimens serve as a uniquely representative sample of the extraterrestrial material accreting to our planet, providing our best glimpse of the full lithological and geochemical breadth of the inner solar system. Antarctic meteorite concentrations are intimately linked to variations in climate and ice sheet behavior over the past several million years, with each individual icefield exhibiting distinct and often unique characteristics.

Mineralogical and geochemical aspects of impact craters

AbstractThe importance of impact cratering on terrestrial planets is obvious from the abundance of craters on their surfaces. On Earth, active geological processes rapidly obliterate the cratering record. To date only about 170 impact structures have been recognized on the Earth's surface. Mineralogical, petrographic, and geochemical criteria are used to identify the impact origin of such structures or related ejecta layers. The two most important criteria are the presence of shock metamorphic effects in mineral and rock inclusions in breccias and melt rocks, as well as the demonstration, by geochemical techniques, that these rocks contain a minor extraterrestrial component. There is a variety of macroscopic and microscopic shock metamorphic effects. The most important ones include the presence of planar deformation features in rock-forming minerals, high-pressure polymorphs (e.g. of coesite and stishovite from quartz, or diamond from graphite), diaplectic glass, and rock and mineral melts. These features have been studied by traditional methods involving the petrographic microscope, and more recently with a variety of instrumental techniques, including transmission electron microscopy, Raman spectroscopy, cathodoluminescence imaging and spectroscopy, and high-resolution X-ray computed tomography. Geochemical methods to detect an extraterrestrial component include measurements of the concentrations of siderophile elements, mainly of the platinum-group elements (PGEs), and, more recently, chromium and osmium isotopic studies. The latter two methods can provide confirmation that these elements are actually of meteoritic origin. The Cr isotopic method is also capable of providing information on the meteorite type. In impact studies there is now a trend towards the use of interdisciplinary and multi-technique approaches to solve open questions.

Oral histories in meteoritics and planetary science: I. Edward Anders

Abstract— In this interview, taped in 2000 August, during the meeting of the Meteoritical Society in Chicago, Edward Anders ascribes his interest in meteorites to a single moment of inspiration while he was in graduate school. He then reviews those advances that he has found most exciting. Some were contributed by his own research group, but many by others. Among the topics are the following: origin of meteorites (lunar or asteroidal parent bodies, diamonds, Widmanstätten pattern, nebular condensation, meteorite orbits, asteroid spectra); primitive meteoritic matter (Cl chondrites, calcium‐aluminum‐rich inclusions (CAIs), solar‐system abundances, organic matter); meteorite ages (radiogenic ages, cosmic‐ray ages, charged particle tracks); classification of meteorites (chondrites, iron meteorites, unequilibrated chondrites); isotopic anomalies (oxygen, heavy elements, noble gases, interstellar grains); and meteorite impacts (impact craters, K/T mass extinction). Anders spent most of his career (1955–1991) at the University of Chicago where he was the Horace B. Horton Professor of Chemistry from 1973–1991. The Meteoritical Society honored Anders with its Leonard Medal in 1974, and he served as its president in 1991–1992. He then dropped out of science. After residing in Switzerland for several years, Anders returned to the USA where he maintains residences in Burlingame, California, and Chicago, Illinois. Today, Anders can be reached at: eanders1@concentric.net.

Proton microprobe characterization of a unique siderophile element mineral assemblage in the melt sheet of the giant 145 Ma Morokweng impact structure, Southern Kalahari, South Africa

The present study deals with mapping of major and trace elements in the Morokweng impact melt sheet which leads to preliminary understanding of its mineralogy. The elements of interest are the siderophile metals, namely, Ni, Co and platinum group metals (PGMs) which are thought to be of meteoritic origin and are highly enriched in the quartz norite and largely concentrated in sulphide–metal oxide intergrowths, which has never been observed before in impact melt sheets. The striking feature of this study is the identification of a new platinum-bearing mineral at the intergrowth of the two major phases, namely nickel sulphide and the iron oxide. The highest concentration of platinum is found to be about 14.3% by weight and is localized in a smaller domain of 20 μm×20 μm . This study not only has metallogenic applications, but also addresses fundamental questions on the behavior or the PGMs at high temperature and very reducing conditions.

Spinel inclusions in olivine of peridotite xenoliths from TUBAF seamount (Bismarck Archipelago/Papua New Guinea): evidence for the thermal and tectonic evolution of the oceanic lithosphere

Olivine in spinel peridotite xenoliths from the Bismarck Archipelago northeast of Papua New Guinea, which were transported to the surface by Quaternary basalts, shows spinel inclusions up to 25 μm long and 200 nm wide. These inclusions mainly occur as inhomogeneously distributed needles and subordinately as octahedral grains in olivine of veined metasomatic peridotites as well as peridotites without obvious metasomatism. The needles very often occur in swarms with irregular spacing in between them. Similar spinel inclusions in olivine have only previously been reported from ultramafites of meteoritic origin. Composition and orientation of the spinel inclusions were determined by transmission electron microscopy (TEM) and analytical electron microscopy (AEM). Both the needles and the grains display a uniform crystallographic orientation in the host olivine with [001]O1//[1¯10]Spl and (100)Ol// (111)Spl. The needles eare elongated parallel [010] in olivine, which is the same in all olivine grains. As these needles have no relation to the metasomatic sections in the peridotite, it is concluded that they are primary features of the rock. Although the composition of the spinel needles is often very similar to the large chromian spinel octahedra in the matrix, the small octahedral spinel inclusions in olivine are in part Mg-rich aluminous spinel and sometimes almost pure magnetite. The spinel needles are suggested to have formed by exsolution processes during cooling of Al- and Cr-rich, high-temperature olivine during the initial formation of the lithospheric mantle at the mid-ocean ridge. The Al-rich spinel octahedra probably formed by the breakdown of an Al-rich phase such as phlogopite or by metasomatism, whereas the magnetite was generated by oxidizing fluids. These oxidizing fluids may either have been set free by dehydration of the underlying, subducted plate or by the Quaternary magmatism responsible for the transport of the xenoliths to the seafloor.

A petrologic study of the IAB iron meteorites: Constraints on the formation of the IAB‐Winonaite parent body

Abstract—We studied 26 IAB iron meteorites containing silicate‐bearing inclusions to better constrain the many diverse hypotheses for the formation of this complex group. These meteorites contain inclusions that fall broadly into five types: (1) sulfide‐rich, composed primarily of troilite and containing abundant embedded silicates; (2) nonchondritic, silicate‐rich, comprised of basaltic, troctolitic, and peridotitic mineralogies; (3) angular, chondritic silicate‐rich, the most common type, with approximately chondritic mineralogy and most closely resembling the winonaites in composition and texture; (4) rounded, often graphite‐rich assemblages that sometimes contain silicates; and (5) phosphate‐bearing inclusions with phosphates generally found in contact with the metallic host. Similarities in mineralogy and mineral and O‐isotopic compositions suggest that IAB iron and winonaite meteorites are from the same parent body.We propose a hypothesis for the origin of IAB iron meteorites that combines some aspects of previous formation models for these meteorites. We suggest that the precursor parent body was chondritic, although unlike any known chondrite group. Metamorphism, partial melting, and incomplete differentiation (i.e., incomplete separation of melt from residue) produced metallic, sulfide‐rich and silicate partial melts (portions of which may have crystallized prior to the mixing event), as well as metamorphosed chondritic materials and residues. Catastrophic impact breakup and reassembly of the debris while near the peak temperature mixed materials from various depths into the re‐accreted parent body. Thus, molten metal from depth was mixed with near‐surface silicate rock, resulting in the formation of silicate‐rich IAB iron and winonaite meteorites. Results of smoothed particle hydrodynamic model calculations support the feasibility of such a mixing mechanism. Not all of the metal melt bodies were mixed with silicate materials during this impact and reaccretion event, and these are now represented by silicate‐free IAB iron meteorites. Ages of silicate inclusions and winonaites of 4.40‐4.54 Ga indicate this entire process occurred early in solar system history.

Internal friction of the glassy tektites

Tektites are naturally occurring glasses, perhaps of meteoritic origin. They occur all over the world. They range in size from μm to decimeter. They are based on the compounds silica and alumina, with smaller concentrations of alkali metal and transition metal oxides. Their origin is in vigorous dispute; some scientists think they are of terrestrial earth origin, others believe they come from interplanetary space, as is true of meteorites. We have secured seven specimens from various regions of the earth and have measured the internal friction spectrum of several in the kilocycle frequency range above room temperature, where internal friction peaks of synthetic glasses have been observed. A well defined loss peak is observed around 500 K in a number of specimens. We have also measured the loss spectrum of obsidian and of blast furnace slag. From comparison of these measurements, we conclude that tektites are probably of volcanic origin, the loss peaks being associated with the reorientation of Fe–oxygen complexes.

Life and intelligence in the universe from nanobiological principles: A survey and budget of concepts and perspectives

The new-born bioscience called Nanobiology has tackled the problems of the possibility of existence of extraterrestrial life and intelligence and of biosystem distribution in the Universe, as such questions actually belong to the realm of Theoretical Biology. The central, and yet unanswered points of such science have been reinvestigated by attempting knowledge and control of the hard-to-determine nanoscale-level classical and quantum interactions, which would supposedly give mechanistic, definite answers, both informationally and energetically, to the vexing questions put by biosystems to science: is the “ living state” a physically definible concept, and how to define it? Are nanoscale kinetics or even detailed mechanics involved in the origin of life? What about intelligence, consciousness and their nanophysical roots? Are “ life” and “ intelligence” engineerable properties, or is any Artificial Intelligence program bound to mere metaphors? Self-organization, studied at the thermodynamic and the hydrodynamic level, showed the possibility of chemical evolution from amino acids, probably of cometary and/or meteoritic origin, up to spatiotemporal organization, autopoiesis and biological evolution, but didn't explain the origins of life. Questioning the uniqueness of the earthly evolutionary chemistry is cardinal for the ETI dilemma, as from a budgetary appraisal of perspectives in bionanoscale chaotic undecidable dynamics, quantum gravity and quantum vacuum, both “ living state” and “ intelligence” look like nonlocal, spacetime-linked cosmic phenomena.

Minor Bodies: Spectral Gradients and Relationships with Meteorites

The observational evidence of a gradient in composition of the solid matter in the Solar System as a function of heliocentric distance, with more volatile elements increasingly abundant at larger heliocentric distances, is in general agreement with commonly accepted ideas about condensation of solid material in the early protoplanetary disk. In this respect, the gradual transition from regions mostly populated by S-type objects in the inner asteroid belt to the C-type dominated outer belt, and to the D-type dominated Trojan clouds has generally been interpreted as diagnostic of a zoning of the asteroid population in terms of mineralogic composition and thermal history. The situation, however, is not completely clear, and several contradictory facts still need an explanation. Another major problem concerns the origin of meteorites. Understanding the history of these bodies is critically important, since most of our ideas about the composition of the original protosolar nebula and protoplanetary matter come from meteoritic data. In this respect, very recent advances have been achieved in the knowledge of dynamical transport mechanisms. This can have important consequences for the characterization of plausible meteorite parent bodies.