共查询到20条相似文献，搜索用时 828 毫秒
1.
D. M. Pechersky G. P. Markov V. A. Tsel’movich Z. V. Sharonova 《Izvestiya Physics of the Solid Earth》2012,48(7-8):653-669
Thermomagnetic and microprobe analyses are carried out and a set of magnetic characteristics are measured for 25 meteorites and 3 tektites from the collections of the Vernadsky Geological Museum of the Russian Academy of Sciences and Museum of Natural History of the North-East Interdisciplinary Science Research Institute, Far Eastern Branch of the Russian Academy of Sciences. It is found that, notwithstanding their type, all the meteorites contain the same magnetic minerals and only differ by concentrations of these minerals. Kamacite with less than 10% nickel is the main magnetic mineral in the studied samples. Pure iron, taenite, and schreibersite are less frequent; nickel, various iron spinels, Fe-Al alloys, etc., are very rare. These minerals are normally absent in the crusts of the Earth and other planets. The studied meteorites are more likely parts of the cores and lower mantles of the meteoritic parent bodies (the planets). Uniformity in the magnetic properties of the meteorites and the types of their thermomagnetic (MT) curves is violated by secondary alterations of the meteorites in the terrestrial environment. The sediments demonstrate the same monotony as the meteorites: kamacite is likely the only extraterrestrial magnetic mineral, which is abundant in sediments and associated with cosmic dust. The compositional similarity of kamacite in iron meteorites and in cosmic dust is due to their common source; the degree of fragmentation of the material of the parent body is the only difference. 相似文献
2.
D. M. Pechersky A. Yu. Kazanskii G. P. Markov V. A. Tselmovich A. A. Shchetnikov 《Izvestiya Physics of the Solid Earth》2018,54(1):106-120
The native iron particles that were previously detected by thermomagnetic and microprobe analyses in the sediments of different age in many regions of the world are of extraterrestrial origin. The similarity in the compositions, grain shapes, and sizes observed in the extraterrestrial and terrestrial particles of native iron testifies to the common production conditions of iron particles during the formation of planets. In this paper, the single finding of terrestrial iron in the lacustrine sediments of the Zhombolok volcanic region, East Sayan, is discussed. The uniqueness of the results indicates that the spatial distribution of the particles of native iron is limited to a fairly narrow area around their source—volcanic eruption or/and the fall of a large meteorite. 相似文献
3.
Edward Stolper 《Earth and Planetary Science Letters》1979,42(2):239-242
The average concentrations of 19 siderophile and volatile elements in shergottite meteorites differ from those in terrestrial basalts by less than a factor of ten. This observation undermines claims that the abundances of siderophile and volatile elements in the Earth's upper mantle are uniquely terrestrial. Claims that similarities in the Moon's siderophile element pattern imply a terrestrial origin for the Moon are also weakened. The implication that basalt source regions on the asteroidal parent body of the shergottites resembled the terrestrial upper mantle constrains models of planetary formation and evolution. Heterogeneous accretion models may explain many of the similarities between these planets. Alternatively, separation of sulfide from basaltic magmas or their source regions on the Earth and the shergottite parent body may explain some of these similarities. 相似文献
4.
D. M. Pechersky D. M. Gil’manova G. P. Markov I. O. Murdmaa D. K. Nurgaliev V. A. Tsel’movich Z. V. Sharonova 《Izvestiya Physics of the Solid Earth》2013,49(3):426-447
The thermomagnetic and microprobe analyses of sedimentary samples from DSDP 386, 387, 391A, and 391C boreholes in the northwestern Atlantic reveal the ubiquitous occurrence of particles of native iron. The concentrations of native iron are bimodal everywhere with the zero mode necessarily present. The nickel admixture in native iron forms two groups, one represented by pure iron and the comprising native iron with 5–6% Ni. The redeposition of iron particles manifests itself in the correlation between the concentrations of these particles and terrestrial minerals (magnetite), as well as in the equalization and reduction of the concentration of the iron particles. Pyrite and pyrrhotite are widespread in the studied sediments, and the distribution of native iron does not depend on the presence of pyrite (i.e., on redox conditions) in them. At the same time, the distributions of pyrite and particles of magnetite + titanomagnetite are inversely correlated, which can probably be accounted for by the partial dissolution of magnetite and titanomagnetite in the reducing conditions. The increased concentration of particles of volcanogenic homogeneous titanomagnetite is revealed in the volcanoclastic turbidites of the Oligocene and early and middle Miocene age at the base of the Bermuda Rise (borehole 386). The titanomagnetite composition is characteristic of the basalts of plume magmatism; it corresponds to the depth of the magmatic source in the interval of 50–25 km. 相似文献
5.
Karen L. Aplin 《Surveys in Geophysics》2006,27(1):63-108
Atmospheric electrification is not a purely terrestrial phenomenon: all Solar System planetary atmospheres become slightly
electrified by cosmic ray ionisation. There is evidence for lightning on Jupiter, Saturn, Uranus and Neptune, and it is possible
on Mars, Venus and Titan. Controversy surrounds the role of atmospheric electricity in physical climate processes on Earth;
here, a comparative approach is employed to review the role of electrification in the atmospheres of other planets and their
moons. This paper reviews the theory, and, where available, measurements, of planetary atmospheric electricity which is taken
to include ion production and ion–aerosol interactions. The conditions necessary for a planetary atmospheric electric circuit
similar to Earth’s, and the likelihood of meeting these conditions in other planetary atmospheres, are briefly discussed.
Atmospheric electrification could be important throughout the solar system, particularly at the outer planets which receive
little solar radiation, increasing the relative significance of electrical forces. Nucleation onto atmospheric ions has been
predicted to affect the evolution and lifetime of haze layers on Titan, Neptune and Triton. Atmospheric electrical processes
on Titan, before the arrival of the Huygens probe, are summarised. For planets closer to Earth, heating from solar radiation
dominates atmospheric circulations. However, Mars may have a global circuit analogous to the terrestrial model, but based
on electrical discharges from dust storms. There is an increasing need for direct measurements of planetary atmospheric electrification,
in particular on Mars, to assess the risk for future unmanned and manned missions. Theoretical understanding could be increased
by cross-disciplinary work to modify and update models and parameterisations initially developed for a specific atmosphere,
to make them more broadly applicable to other planetary atmospheres. 相似文献
6.
New measurements of mass-dependent calcium isotope effects in meteorites, lunar and terrestrial samples show that Earth, Moon, Mars, and differentiated asteroids (e.g., 4-Vesta and the angrite and aubrite parent bodies) are indistinguishable from primitive ordinary chondritic meteorites at our current analytical resolution (± 0.07‰ SD for the 44Ca/40Ca ratio). In contrast, enstatite chondritic meteorites are slightly enriched in heavier calcium isotopes (ca. + 0.5‰) and primitive carbonaceous chondritic meteorites are depleted in heavier calcium isotopes (ca. ? 0.5‰). The calcium isotope effects cannot be easily ascribed to evaporation or intraplanetary differentiation processes. The isotopic variations probably survive from the earliest stages of nebular condensation, and indicate that condensation occurred under non-equilibrium (undercooled nebular gas) conditions. Some of this early high-temperature calcium isotope heterogeneity is recorded by refractory inclusions (Niederer and Papanastassiou, 1984) and survived in planetesimals, but virtually none of it survived through terrestrial planet accretion. The new calcium isotope data suggest that ordinary chondrites are representative of the bulk of the refractory materials that formed the terrestrial planets; enstatite and carbonaceous chondrites are not. The enrichment of light calcium isotopes in bulk carbonaceous chondrites implies that their compositions are not fully representative of the solar nebula condensable fraction. 相似文献
7.
The larger and most energetic cratering events from comet and asteroid collisions with the Earth are probably associated with ejection of solid material faster than escape speeds every 100 Myr or so. Metre-sized boulders, we estimate, may have been ejected directly into Venus-crossing and perhaps Mars-crossing orbits from comet impacts at higher speeds and of larger mass, at least on 10 occasions in the last 3.5 Ga. Subsequent close encounters with Earth can also enable slower boulders to reach Mars-crossing orbits. Orbit perturbations from Mars and Jupiter would then have sent a fraction of the boulders to the outer planets and their icy satellite systems. In the so-called late bombardment epoch at 3.9 Ga, when primitive life was developing, ejection-causing impacts were much more frequent, at 30 per 0.1 Ga, yielding an increased probability of distributing seeds of terrestrial biology to the outer regions of the solar system. 相似文献
8.
SmNd isotopic data for mineral separates from the ferroan anorthosite 60025 define a precise isochron of 4.44 ± 0.02Ga age. This age is roughly 110 m.y. younger than the formation of the first large solid objects in the solar nebula, as recorded by the radiometric ages of the differentiated meteorites. In the magma ocean model for early lunar differentiation, ferroan anorthosites are the first crustal rocks to form on the Moon. If the Moon is as old as the oldest meteorites, the relatively young age determined for 60025 implies either that the magma ocean did not form synchronously with lunar formation, or that the magma ocean required over 100 m.y. before reaching the stage of ferroan anorthosite crystallization. Alternatively, we propose that the accumulated body of radiogenic isotope data for lunar rocks permit the Moon to be as young as 4.44–4.51 Ga. If so, isotopic evidence for chemical differentiation on the Earth at about this same time suggests that the formation of the Moon is reflected in the chemical evolution of the Earth. This, in turn, is consistent with the idea that the materials that now make up the Moon were derived from the Earth, perhaps ejected by collision between the Earth and another very large planetesimal during the final stages of accumulation of the terrestrial planets. Terrestrial origin models for the Moon lessen the requirement that the Earth and Moon each have near chondritic relative abundances of the refractory elements and could require that certain chemical and isotopic characteristics of both bodies be considered in the framework of the chemical mass-balance of the combined Earth-Moon system. 相似文献
9.
Fractionation between the metal and silicate components of objects in the inner solar system has long been recognized as a necessity in order to explain the observed density variations of the terrestrial planets and the H-group, L-group dichotomy of the ordinary chondrites. This paper discusses the densities of the terrestrial planets in light of current physical and chemical models of processes in the solar nebula. It is shown that the observed density trends in the inner solar system need not be the result of special fractionation processes, and that the densities of the planets may be direct results of simultaneous application of both physical and chemical restraints on the structure of the nebula, most notably the variation of temperature with heliocentric distance. The density of Mercury is easily attributed to accretion at temperatures so high that MgSiO3 is only partially retained but Fe metal is condensed. The densities of the other terrestrial planets are shown to be due to different degrees of retention of S, O and H as FeS, FeO and hydrous silicates produced in chemical equilibrium between condensates and solar-composition gases. It is proposed that Mercury and Venus Have cores of Fe0, Earth has a core of Fe0 containing substantial amounts of FeS, and Mars has a quite small core of FeS with more FeO in its mantle than in Earth's. Geophysical and geochemical consequences of these conclusions are discussed. 相似文献
10.
《Astronomy& Geophysics》2009,50(4):4.21-4.26
Monica M Grady reviews the astronomy revealed in samples of solar system material that come to Earth as meteorites, in the Harold Jeffreys Lecture 2008. 相似文献
11.
D. M. Pechersky D. K. Nurgaliev V. A. Fomin Z. V. Sharonova D. M. Gil’manova 《Izvestiya Physics of the Solid Earth》2011,47(5):379-401
The composition and distribution of particles of native iron in eight sections of the Cretaceous-Danian sediments in the Caucasus,
Crimea and Kopet Dagh were studied using thermomagnetic analysis up to 800°C. Iron particles are found in 330 of 571 tested
samples, their percentage varies from 10−5 to 0.05%, and their distribution is bimodal. It was established that the Santonian sediments of the Caucasus and Kara-Kala
are enriched with the iron particles; the upper boundary of these sediments is marked by a sharp drop in the iron content
at approximately 84 Ma, which coincides with the upper boundary of the Dzhalal hyperchron. The variations in the Curie point
of iron from 680°C up to 780°C reflect the fluctuations of the nickel admixture. A peak of the elevated iron content with
nearly constant nickel of 5% was found in all studied sections, i.e., this is a global effect. The global pattern of the distribution
and composition of the iron particles clearly indicates that their origin is associated with cosmic dust. At the same time,
the particles of Ni-Fe alloy and pure nickel are very rare, and their concentration does not correlate with the content of
iron particles. Apparently, there are very few Ni-Fe and pure nickel particles in cosmic dust, and, most likely, the particles
of Ni-Fe alloy are mainly due to impact events. 相似文献
12.
Christiane Helling R. Giles Harrison Farideh Honary Declan A. Diver Karen Aplin Ian Dobbs-Dixon Ute Ebert Shu-ichiro Inutsuka Francisco J. Gordillo-Vazquez Stuart Littlefair 《Surveys in Geophysics》2016,37(4):705-756
Detailed observations of the solar system planets reveal a wide variety of local atmospheric conditions. Astronomical observations have revealed a variety of extrasolar planets none of which resembles any of the solar system planets in full. Instead, the most massive amongst the extrasolar planets, the gas giants, appear very similar to the class of (young) brown dwarfs which are amongst the oldest objects in the Universe. Despite this diversity, solar system planets, extrasolar planets and brown dwarfs have broadly similar global temperatures between 300 and 2500 K. In consequence, clouds of different chemical species form in their atmospheres. While the details of these clouds differ, the fundamental physical processes are the same. Further to this, all these objects were observed to produce radio and X-ray emissions. While both kinds of radiation are well studied on Earth and to a lesser extent on the solar system planets, the occurrence of emissions that potentially originate from accelerated electrons on brown dwarfs, extrasolar planets and protoplanetary disks is not well understood yet. This paper offers an interdisciplinary view on electrification processes and their feedback on their hosting environment in meteorology, volcanology, planetology and research on extrasolar planets and planet formation. 相似文献
13.
Since 1969, seismology has been extended beyond the Earth, and seismic sensors have been placed on the surface of other bodies of the solar system. A Lunar seismic network thus operated for the 8 years after 1969, with up to 4 stations, and detected some 1000 Moonquakes per year. A single seismic station was also operated on the Martian surface for 19 months since 1977. Unfortunately, it did not detect any Marsquakes, but produced useful information for future experiments. Remotesensing seismic experiments using Doppler shift observation have also been applied to Jupiter in the last two years and are beginning to return information on the normal modes. Planetary seismology is thus now well developed, and will provide increasing information on the structure and dynamics of the planets and bodies of the solar system. In this paper we review the state of the art in planetary seismology. For the terrestrial planets, we compare the seismic sources, structure and experiments on Earth, Moon and Mars. Such a comparison is useful in evaluating the design of past or future experiments. Results in the seismology of giant planets are also reviewed, stressing the connection between methods and theory. 相似文献
14.
Terrestrial xenology 总被引：13，自引：0，他引：13
The xenon isotopic composition measured in samples from various origins shows that variations relative to the atmospheric standard are common. Excesses in129Xe and fissiogenic xenon, derived from the extinct radioactivities129I and244Pu respectively, are characteristic of mid-ocean ridge basalts, whereas238U-fission xenon excesses are only found in granitoid samples or in samples which are contaminated by the continental crust. Hence, the xenon isotopes can be used as tracers in geodynamics. A model for the degassing of the terrestrial mantle is developed and reflections on the time interval between the formation of meteorites and the formation of the Earth are made. 相似文献
15.
Acceleration of charged particles in magnetic field-aligned electric potential differences at Earth and at the outer planets in the solar system is summarized and its general importance in the Universe is briefly discussed.The role of field-aligned currents, driven by parallel electric fields, in causing filamentary structure in stellar atmospheres is briefly reviewed.The differences between auroral optical emissions at various planets are summarized.The important role of field-aligned potential differences in the generation of AKR and corresponding emissions from other objects is discussed.Finally, aurora-associated processes for ejection of planetary plasma into space are briefly reviewed. 相似文献
16.
Taylor SR 《AGSO journal of Australian geology & geophysics》1997,17(1):27-31
It is not possible to consider the formation of the Earth in isolation without reference to the formation of the rest of the solar system. A brief account is given of the current scientific consensus on that topic, explaining the origin of an inner solar system rocky planet depleted in most of the gaseous and icy components of the original solar nebula. Volatile element depletion occurred at a very early stage in the nebula, and was probably responsible for the formation of Jupiter before that of the inner planets. The Earth formed subsequently from accumulation of a hierarchy of planetesimals. Evidence of these remains in the ancient cratered surfaces and the obliquities (tilts) of most planets. Earth melting occurred during this process, as well as from the giant Moon-forming impact. The strange density and chemistry of the Moon are consistent with an origin from the mantle of the impactor. Core-mantle separation on the Earth was coeval with accretion. Some speculations are given on the origin of the hydrosphere. 相似文献
17.
The paper summarizes the results of thermomagnetic analysis concerning the distribution of metallic iron in the sediments
ranging in age from Miocene to Early Cretaceous sampled from the following sections: Gams (Austria); Verkhorech’e and Sel’bukhra
(the Crimea); Kvirinaki and Tetritskaro (Georgia); Aimaki, Dzhengutai, Madzhalis, and Gergebil (Ciscaucasia, Russia); Klyuchi
and Teplovka (Volga region, Russia); Koshak (Kazakhstan); and Khalats and Kara-Kala (Turkmenia). Small amounts of native iron
(from 10−5% to 0.05%) are identified in 521 samples of 921 studied; i.e., iron particles are almost pervasive. This fact traces the
origin of these particles to cosmic dust. Some established features point to the heterogeneous character of the cosmic dust:
(a) the samples clearly fall into two groups. One group comprises the rocks that contain iron particles; the rocks of the
other group are iron-free. In the first group, four intervals are distinguished where the sediments are globally enriched with iron with constant nickel content (5–6%); (b) in terms of composition, the iron particles are divided into
three groups. The first group contains pure iron; the particles pertaining to the second group contain iron with a minor amount
of nickel typical for kamacite; and the third group comprises the particles of Fe-Ni alloy with more than 20% nickel. The
first and the second groups are ubiquitous; the particles of the third group are spread locally. They bear no relation to
cosmic dust and are probably associated with the meteoritic impacts. 相似文献
18.
Although vigorous mantle convection early in the thermal history of the Earth is shown to be capable of removing several times the latent heat content of the core, we are able to construct a thermal evolution model of the Earth in which the core does not solidify. The large amount of energy removed from the model Earth's core by mantle convection is supplied by the internal energy of the core which is assumed to cool from an initial high temperature given by the silicate melting temperature at the core-mantle boundary. For the smaller terrestrial planets, the iron and silicate melting temperatures at the core-mantle boundaries are more comparable than for the Earth, and the cores of these planets may not possess enough internal energy to prevent core solidification by mantle convection. Our models incorporate temperature-dependent mantle viscosity and radiogenic heat sources in the mantle. The Earth models are constrained by the present surface heat flux and mantle viscosity. Internal heat sources produce only about 55% of the Earth model's present surface heat flow. 相似文献
19.
The data on the distribution of native iron particles in sediments yielded by thermomagnetic analysis are explored. It is shown that the accumulation of iron particles in sediments is statistically inversely linked with the rate of sedimentation and the frequency of geomagnetic reversals and statistically directly linked to the intensity of the geomagnetic field. These dependences highlight the predominance of cosmic iron particles in the studied sediments. 相似文献
20.
Iron isotope fractionation during planetary differentiation 总被引：4，自引：0，他引：4
Stefan Weyer Ariel D. Anbar Carsten Münker Alan B. Woodland 《Earth and Planetary Science Letters》2005,240(2):251-264
The Fe isotope composition of samples from the Moon, Mars (SNC meteorites), HED parent body (eucrites), pallasites (metal and silicate) and the Earth's mantle were measured using high mass resolution MC-ICP-MS. These high precision measurements (δ56Fe ≈ ± 0.04‰, 2 S.D.) place tight constraints on Fe isotope fractionation during planetary differentiation.Fractionation during planetary core formation is confined to < 0.1‰ for δ56Fe by the indistinguishable Fe isotope composition of pallasite bulk metal (including sulfides and phosphides) and olivine separates. However, large isotopic variations (≈ 0.5‰) were observed among pallasite metal separates, varying systematically with the amounts of troilite, schreibersite, kamacite and taenite. Troilite generally has the lightest (δ56Fe ≈ − 0.25‰) and schreibersite the heaviest (δ56Fe ≈ + 0.2‰) Fe isotope composition. Taenite is heavier then kamacite. Therefore, these variations probably reflect Fe isotope fractionation during the late stage evolution and differentiation of the S- and P-rich metal melts, and during low-temperature kamacite exsolution, rather than fractionation during silicate-metal separation.Differentiation of the silicate portion of planets also seems to fractionate Fe isotopes. Notably, magmatic rocks (partial melts) are systematically isotopically heavier than their mantle protoliths. This is indicated by the mean of 11 terrestrial peridotite samples from different tectonic settings (δ56Fe = + 0.015 ± 0.018‰), which is significantly lighter than the mean of terrestrial basalts (δ56Fe = + 0.076 ± 0.029‰). We consider the peridotite mean to be the best estimate for the Fe isotope composition of the bulk silicate Earth, and probably also of bulk Earth. The terrestrial basaltic mean is in good agreement with the mean of the lunar samples (δ56Fe = + 0.073 ± 0.019‰), excluding the high-Ti basalts. The high-Ti basalts display the heaviest Fe isotope composition of all rocks measured here (δ56Fe ≈ + 0.2‰). This is interpreted as a fingerprint of the lunar magma ocean, which produced a very heterogeneous mantle, including the ilmenite-rich source regions of these basalts.Within uncertainties, samples from Mars (SNC meteorites), HED (eucrites) and the pallasites (average olivine + metal) have the same Fe isotope compositions as the Earth's mantle. This indicates that the solar system is very homogeneous in Fe isotopes. Its average δ56Fe is very close to that of the IRMM-014 standard. 相似文献