Thermoluminescence of meteorites and their orbits

The thermoluminescence (TL) levels of 45 ordinary chondrites were measured to obtain information about the meteorite orbits. The low-temperature TL reaches equilibrium while the meteorite is in space and reflects the temperature of the meteorite at perihelion. Samples of Pribram, Lost City, and Innisfree, whose orbits are accurately known, were used as control samples. The TL levels in 40 out ot 42 meteorites are similar to the three control samples, indicating that the vast majority of ordinary chondrites that survive atmospheric entry have perihelia similar to three known orbits, i.e., in the range 0.8–1 AU. The effects of albedo and rotation are also considered. A simple model indicates that temperature gradients of 1–2°K/cm are possible in slowly rotating meteoroids and such a temperature gradient is consistent with the unusually large TL gradient measured in the Farmville meteorite. Since slow rotation rates are improbable, other possibilities are examined but no satisfactory explanation has been found. The TL level measured in the Malakal meteorite is two orders of magnitude lower than control samples and is best explained by thermal draining due to solar heating in an orbit with a small perihelion distance. The perihelion is estimated to be～0.5–0.6AU.     

The age of SNC meteorites and the antiquity of the Martian surface

We report new Sm-Nd, Lu-Hf, and Pb-Pb mineral and whole-rock isotope data for the basaltic shergottite Zagami, as well as Pb-Pb whole-rock isotope data for the basaltic shergottite Los Angeles, the lherzolitic shergottite Dar-al-Gani 476 (DaG 476), and the clinopyroxenite Nakhla. In agreement with previous findings, our new Sm-Nd and Lu-Hf mineral ages on the Martian meteorite Zagami are young (155 and 185 Ma, respectively). The ²⁰⁷Pb/²⁰⁶Pb-²⁰⁴Pb/²⁰⁶Pb compositions of the insoluble fractions of shergottites (Zagami, Los Angeles, and literature data for Shergotty and EETA79001) form an excellent alignment indicative of a 4.0 Ga crystallization age. The range of Pb isotope compositions observed in the leachates of these samples attests to negligible contamination of the shergottites by terrestrial Pb and argues against mixing relationships. The age of 4.048 ± 0.017 Ga (MSWD = 1.5) provided by the Pb isotope compositions of the Zagami whole-rock and residues is therefore taken to date the crystallization of this rock, which, so far, was believed to be only ∼ 180 Ma old. Based on this result, we argue that the lithosphere of Mars is extremely old and that most mineral ages were reset recently by acidic aqueous solutions percolating through the Martian surface. This interpretation is consistent with photographic interpretations of erosional features on Mars. It also relieves the constraint imposed by the presence of anomalies of ¹⁴²Nd and ¹⁸²W (both products of extinct radioactive nuclides) that the Martian mantle should have preserved primordial isotopic heterogeneities, thus allowing for the planet interior to be actively convecting.     

Some results from recent chemical studies at Kilauea volcano,Hawaii

The chemical surveillance of Kilauea volcano, Hawaii, has continued. No relationship has thus far been identified between the helium content of an associated fumarole and the activity at the volcano. Fume samples from Halemaumau crater in Kilauea caldera and from a fissure eruption that occurred nearby on the floor of the caldera during August 1971 were examined for their halogen (Cl and F) and sulfur contents. The ratio of Cl/F in fume showed an abnormal increase in samples taken at Halemaumau a month before the eruption. This change in ratio may be a helpful indicator of the onset of eruption in volcanic areas.     

Seismostructural studies in the Pyrenees: Evolution and recent results

Seismic studies of the last ten years in the Pyrenees (deep seismic profiles, fan profiles at critical distance, teleseismic travel-time residuals, seismicity from temporary networks) and their most significant results concerning crustal thickness in the different structural units of the range, sharpness of the transition between these units at depth, and east-west lateral evolution are reviewed in this paper. Focal mechanisms for three recent earthquakes ofM4 are given, and connections of local seismicity with major tectonic structures such as the North Pyrenean Fault and its western prolongation at depth are described.     

The isotopic composition and elemental abundance of lutetium in meteorites and terrestrial samples and the 176Lu cosmochronometer

The isotopic composition of lutetium has been measured in a range of terrestrial and meteoritic materials using solid-source mass spectrometric techniques. The meteoritic and terrestrial isotopic abundances are identical within experimental errors. The absolute ¹⁷⁵Lu/¹⁷⁶Lu ratio as determined in this work is 37.36 ± 0.07 at the 95% confidence level. On the basis of this measurement the atomic weight of lutetium has been calculated to be 174.967 ± 0.002, which is in good agreement with the currently accepted figure of 174.97 ± 0.01.Using the stable isotope dilution technique the abundance of lutetium has been determined in 25 stone, 1 stony-iron and 8 iron meteorites, and in 12 standard rocks, with an accuracy of ±5% at the 95% confidence level. In general, there is good agreement between this work and other published data.The ¹⁷⁶Lu-¹⁷⁶Hf pair has been proposed as an s process nucleocosmochronometer, because of the long half-life of ¹⁷⁶Lu and the unique fact that both are s process isobars. The isotopic and elemental abundances of lutetium as measured in this work have been used with published nuclear data to estimate the mean age of s process nucleosynthesis for this isobaric pair, using the Schramm-Wasserburg formalism. The mean age cannot be accurately determined at the present time because of the lack of 30 keV neutron capture cross-section data for s only process nuclides and an accurate measurement of the branching ratio of ¹⁷⁵Lu + n. However, it is possible to place constraints on the nuclear parameters in this mass region using a reasonable s process chronology based on the decay of ¹⁷⁶Lu.     

Sigmoid CME source regions at the Sun: some recent results

Identifying coronal mass ejection (CME) precursors in the solar corona would be an important step in space weather forecasting, as well as a vital key to understanding the physics of CMEs. Twisted magnetic field structures are suspected of being the source of at least some CMEs. These features can appear sigmoid (S or inverse-S) shaped in soft X-ray (SXR) images. We review recent observations of these structures and their relation to CMEs, using SXR data from the Soft X-ray Telescope (SXT) on the Yohkoh satellite, and EUV data from the EUV Imaging Telescope (EIT) on the SOHO satellite. These observations indicate that the pre-eruption sigmoid patterns are more prominent in SXRs than in EUV, and that sigmoid precursors are present in over 50% of CMEs. These findings are important for CME research, and may potentially be a major component to space weather forecasting. So far, however, the studies have been subject to restrictions that will have to be relaxed before sigmoid morphology can be used as a reliable predictive tool. Moreover, some CMEs do not display a SXR sigmoid structure prior to eruption, and some others show no prominent SXR signature of any kind before or during eruption.     

Short review and recent results on microseisms

This paper endeavours, mostly in a bibliographical manner, to show the place of meteorological microseims among the whole of geophysics. Relations with swell are mentioned with their theoretical and practical consequences for the properties of both phenomena, and the work of members of the International Commissions on Microseisms is summarized, covering velocity and bearing of the waves, spectral analysis, relation with atmospheric circulation, and world-wide extension of these researches since the I. G. Y. In a recent project, undecennial variation of yearly means of microseismic disturbance, the maximum of which often occurs 2–3 years after sunspot maxima, is investigated using data from several stations. A similar variation is therefore inferred for atmospheric cyclones, and the brightness of other planets seems to vary in the same way. Changes in the solar constant are suggested as the physical influence responsible, and new recording devices are proposed to follow on an absolute scale the future behaviour of such an index of atmospheric disturbances.     

Solar wind—magnetosphere coupling: A review of recent results

This paper reviews some aspects of solar wind–magnetosphere–ionosphere interaction. It is shown that in addition to the interplanetary electric field, the solar wind dynamic pressure also has a significant role in determining the state, dynamics, and energetics of the system. It is demonstrated how the state of the magnetosphere and the prior driving affect the amount of energy input to the system, which highlights the capability of the magnetosphere to control the energy flow. The active role of the magnetosphere in determining the dynamics is illustrated by statistical results of the flux balance in the magnetotail and the various dynamic cycles the system can enter. The inner magnetosphere processes during storms are shown to be a result of a complex interplay of processes at the magnetopause and in the magnetotail in response to the solar wind driving. The conclusions are drawn from statistical observational results, empirical models, and global MHD simulations.     

Condensation and the composition of iron meteorites

The pressure-temperature conditions in the primordial nebula which could produce the observed Ni, Ga and Ge abundances in the major iron meteorite groups have been calculated assuming equilibrium condensation. Included in these calculations are the effect on the metal composition of Fe oxidation and sulphide formation during accretion, GeS and GaCl in the nebula gases and pressure variations in the nebula. It was found that the IIAB irons had their abundances of these elements fixed at the low-pressure extreme of the range which gives the IAB irons, but at 50 ± 10K higher temperatures. IIIAB and IVA formed over the same temperature range as IAB (600–670_?40⁺⁶⁰ K) in regions where the pressure was lower by a factor of 20 and 10⁴ respectively. Group IVB accreted soon after condensation of the metal and at pressures of less than 10^?3 atmosphere. The distribution of sulphur and carbon are consistent with this. The abundance of carbon in group IAB suggests that this and group IIAB accreted at about 10^?4 atmosphere, so that IIIAB and IVA accreted where the pressure was 5 × 10^?6 and 10^?8 atmosphere, respectively.     

Thermoluminescence studies of the Allende meteorite

The Allende meteorite has been examined with a view to applying thermoluminescence (TL) to the study of a meteorite's passage through the atmosphere. At least three kinds of TL-bearing minerals are present. A strong peak at 140°C is due to forsterite, and one at 200°C is probably caused by cordierite. By far the most intense TL comes from an alteration product associated with gehlenite.In the 4-cm diameter meteorite examined the 200°C TL varied in intensity across the stone, showing it to be produced by fragmentation. Temperature gradients induced by atmospheric heating can also be derived, and indicate the orientation of the meteorite. Together with fusion crust measurements these results enable the final phase of the meteorite's passage through the atmosphere to be delineated.     

High field intensity results from recent and historic lavas

A total of 45 recent and historic lava flows of Mount Etna, Sicily, were sampled to investigate changes in the strength and orientation of the geomagnetic field in the region. Of the flows sampled, 11 yielded one or more samples which provided anomalously high field intensity results. A rock magnetic study has shown that a high resistance to alternating field demagnetization and group 2 low-temperature susceptibility behaviour are the two factors common to these samples.     

Some results of aerosol measurements

Summary In brief a newly developed freezing nuclei meter is described. Results of measurements made with this instrument in New Jersey, California and in the Thule area, Greenland, are shown. These data are compared with measurements of condensation nuclei, simultaneously made with the General Electric and the Aitkennuclei counters. Also the results obtained from some measurements of the lightscattering function of the aerosol in industrial areas near New York City are presented.     

Some recent investigations on the nature and properties of natural and artificial freezing nuclei

Summary Working on the hypothesis that atmospheric ice-forming nuclei are largely of terrestrial origin, the nucleating ability of various types of soil particles and mineral dusts has been investigated. Of the thirty substances tested, twenty-one, mainly silicate minerals of the clay and mica groups, were found to produce ice crystals in supercooled clouds and also on supercooled soap films at temperatures of – 18° C, or above, and of these, ten were active above – 12° C. The most abundant of these is kaolinite with a threshold temperature of – 9° C. Ten natural substances, again mainly silicates, were found to become more efficient ice nuclei having once been involved in ice-crystal formation, i.e. they could be pre-activated or «trained». Thus, ice crystals grown on kaolinite nuclei, which are initially active at –9° C, when evaporated and warmed to near 0° C in a dry atmosphere, leave behind nuclei which are thereafter effective at – 4° C. Particles of montmorillonite, another important constituent of some clays, and which are initially inactive even at –25° C, may be pre-activated to serve as ice nuclei at temperatures as high as –10° C. It is suggested that although such particles can initially form ice crystals only at cirrus levels, when the ice crystals evaporate they will leave behind some «trained» nuclei which may later seed lower clouds at temperatures only a few degrees below 0° C. On this hypothesis, the fact that efficient nuclei are occasionally more abundant at higher levels would not necessarily imply that they originate from outer space. Indeed, in view of our tests on products of stony meteorites, produced both by grinding and vaporization, which show them to be ineffective at temperatures above – 17° C, it seems likely that atmospheric ice nuclei are produced mainly at the earth's surface, the clay minerals, particularly kaolinite, being a major source.Although a good deal of work has been carried out in different laboratories on the ice-nucleating ability of a wide variety of inorganic compounds, there has been little agreement in the results. Careful tests carried out in our laboratory have revealed a number of reasons for this. Spurious results may be obtained because of the presence, in the air or the chemicals, of small traces of silver or free iodine, leading to the formation of silver iodide: if all such trace impurities are removed, many of the substances that have been claimed to provide efficient ice nuclei are found to be quite ineffective. It is dangerous to infer that all twinkling particles in a water cloud are ice crystals since particles of some seeding agents glitter even at positive temperatures. The threshold temperature of a nucleant will depend upon the criterion adopted for the onset of nucleation, i.e. upon the fraction of the total number of particles of seeding agent which are activated; this, in turn, will depend upon the fraction of particles which happen to possess suitable crystallographic faces for nucleation. Much may also depend upon the manner in which the test is performed. Since some nucleating materials produce ice crystals only after a delay of 30 seconds or more, they may appear to be ineffective if tested in the transient cloud of an expansion chamber but highly effective if allowed to remain in an ice-supersaturated atmosphere for a minute or more. Again, we have found that the efficiency of some nuclei is governed by the supersaturation as well as the temperature of the environment, and the supersaturation regimes in expansion, diffusion, and mixing-cloud chamber may be widely different. Highly soluble particles, although able to act as «sublimation» nuclei in atmospheres super-saturated relative to ice but sub-saturated relative to water, on entering a water cloud go quickly into solution and lose their nucleating ability.Inorganic substances which definitely nucleate a supercooled water cloud in a mixing-cloud chamber at temperatures of –15° C and above are: AgI (–4° C), PbI₂ (–6° C), CuS (–6° C), Ag₂S (–8° C), Ag₂O (–9° C), HgI₂ (–8° C), V₂O₅ (–14° C), Cu₂I₂ (–15° C), the figures in brackets indicating the threshold temperatures at which about one particle in 10⁴ becomes active as an ice nucleus. Cadmium iodide (–12° C), ammonium fluoride (–9° C) and iodine (–14° C) are examples of salts which will act as sublimation nuclei in an ice-supersaturated atmosphere and will nucleate a supercooled soap film, but which are ineffective in a water cloud because of their solubility.Although the most efficient nucleating agents tend to be hexagonal in structure, there are some striking exceptions e.g. Ag₂S, Ag₂O, HgI₂, but in most cases, we have been able to find a low-index crystal surface on which the ice lattice could grow with a misfit of only a few per cent.In an attempt to investigate the nucleation mechanism in more detail, we have studied the growth of ice on single crystals of various nucleating agents. Perfect orientation of ice crystals has so far been observed on the basal faces of silver iodide, lead iodide, cupric sulphide, cadmium iodide, and freshly-cleaved mica, on the (001) plane of iodine, and on the (010) plane of mercuric iodide.     

The topical problems of identifying the results of the observations in recent geodynamics

The paper addresses the problems of identifying the results of deformational observations on the Earth, which arise from the new measurement technologies and lead to the ambiguity relationships such as the “spatial size of the anomaly—density of the observation sites” and the “duration of the anomalies—degree of temporal detail of the measurements.” It is found that many “paradoxical” conclusions concerning the rates and scales of the recent geodynamical processes are removed if the parameters of the measurement system match the properties of the studied object and if the relative character of the observational means is taken into account. It is shown that the time variation in the uniaxial deviatoric stress leads to the variation in the volumetric strain and, consequently, to the variation in gravity. The ambiguity in determining the ground displacement vectors by SAR interferometry is demonstrated. It is concluded that the autonomous use of the interferometry data leads to the significant distortions of the results, and these data should be necessarily used in combination with the ground-based geodetic observations.     

Some structural and geomorphological aspects of recent crustal movements in estonia

Comparison of some structure contour of northeastern and southeastern Estonia with the bedrock relief patterns leads to the conclusion that direct morphostructures are infrequent in those areas. The formation of bedrock and contemporary relief has been little effected by differential postglacial and recent crustal movements. Morphotectonic analysis enables us to determine the character of those movements only in a few cases.     

Some methods of adjusting a terrestrial spatial network (Part 1)

Summary In the Part 1 and in a subsequent Part 2 to be published two methods of adjusting a spatial terrestrial network in tri-dimensional space are described. Care has been taken that the nature of the equations used, as well as of the adjustment, correspond to the same in adjustment satellite networks. The adjustment was carried out by the least-squares method according to conditioned observations. Various types of condition equations have been constructed according to the various types of adjusted quantities, and the various alternatives of the introduced errors (changes of input values) and weights. An effort was made to eliminate the ellipsoid of reference to the largest extent. The theory was applied numerically to a model of a smaller network which corresponds in position and height to usual triangulation networks with side lengths of about 30 km.Dedicated to 90th Birthday of Professor Frantiek Fiala