Consortium study of the unusual H chondrite regolith breccia,Noblesville

Abstract— The Noblesville meteorite is a genomict, regolith breccia (H6 clasts in H4 matrix). Mössbauer analysis confirms that Noblesville is unusually fresh, not surprising in view of its recovery immediately after its fall. It resembles “normal” H4–6 chondrites in its chemical composition and induced thermoluminescence (TL) levels. Thus, at least in its contents of volatile trace elements, Noblesville differs from other H chondrite, class A regolith breccias. Noblesville's small pre-atmospheric mass and fall near Solar maximum and/or its peculiar orbit (with perihelion <0.8 AU as shown by natural TL intensity) may partly explain its levels of cosmogenic radionuclides. Its cosmic ray exposure age of ～ 44 Ma, is long, is equalled or exceeded by <3% of all H chondrites, and also differs from the 33 ± 3 Ma mean exposure age peak of other H chondrite regolith breccias. One whole-rock aliquot has a high, but not unmatched, ¹²⁹Xe/¹³²Xe of 1.88. While Noblesville is now among the chondritic regolithic breccias richest in solar gases, elemental ratios indicate some loss, especially of He, perhaps b; impacts in the regolith that heated individual grains. While general shock-loading levels in Noblesville did not exceed 4 GPa, individual clasts record shock levels of 5–10 GPa, doubtless acquired prior to lithification of the whole-rock meteoroid.     

The H.E.S.S. central data acquisition system

The High Energy Stereoscopic System (H.E.S.S.) is a system of Imaging Atmospheric Cherenkov Telescopes (IACTs) located in the Khomas Highland in Namibia. It measures cosmic gamma rays of very high energies (VHE; >100 GeV) using the Earth’s atmosphere as a calorimeter. The H.E.S.S. Array entered Phase II in September 2012 with the inauguration of a fifth telescope that is larger and more complex than the other four. This paper will give an overview of the current H.E.S.S. central data acquisition (DAQ) system with particular emphasis on the upgrades made to integrate the fifth telescope into the array. At first, the various requirements for the central DAQ are discussed then the general design principles employed to fulfil these requirements are described. Finally, the performance, stability and reliability of the H.E.S.S. central DAQ are presented. One of the major accomplishments is that less than 0.8% of observation time has been lost due to central DAQ problems since 2009.     

On the Chandler wobble. I. Theory

This paper introduces the idea that there exists a nutation separation layer in the superficial zone of the Earth, thereby sets up a new model of nutation. The equations of motion are derived and solved. It is proved that the separation layer is “soft”, and is probably located at a depth of 300 km from the surface. Its allowable minimum thickness is less than 1 km and its viscosity is on the order of 10₁₀ poise, like pitch at 15 °C. The results show that the main peak of the Chandler wobble (CW) is double, one being the nutational frequency of the inner main body, the other , the outer component. The beat between the two frequencies produces the 40-yr period in the amplitude of the CW. The two amplitudes interact so they do not differ greatly in size, their approximate ratio being 1 to 0.7. The famous amplitude-period relation of the CW is a direct result of this paper. The sudden changes in the polar trace and the 180° phase change in 1924–1926 are essentially the same phenomenon determined by relative changes in the two frequencies. The value of Q for the CW of between 30 and 60 deduced by previous workers from observations is a false Q, the true Q is around 200, in agreement with the value from seismic waves. This paper also predicts that apart from the two main frequencies, there is a series (more than one pair) of secondary frequencies symmetrically located on either side. The time constant of the CW is about 70 yr and it can be approximately maintained by excitation by earthquakes. Its unsmooth motion is one that zigzags about the mean trace.     

Comment on “Mechanics of tidally driven fractures in Europa's ice shell” by S. Lee, R.T. Pappalardo, and N.C. Makris [2005. Icarus 177, 367-379]

We show Lee, Pappalardo, and Makris' [2005. Icarus 177, 367-379] argument that surface cracks in Europa's icy shell penetrate 3-10 times deeper in the presence of subsurface ocean is not correct. We use numerical calculations to demonstrate that there is at most 50% increase in penetration depth for a crack opening in a shell of finite thickness compared to a half-space. We also propose a simple equation based on force balances to estimate the maximum thickness of an ice shell that can be opened under tensile stress. Our calculations show that a crack can only penetrate 330-m-thick ice shell under 200 kPa far-field tensile stress and half of that if the stress is 100 kPa. But the presence of water would allow crack penetrate ∼4.0 km into the ice shell with zero porosity.     

Comment on the paper ‘Two-Fluid Model of the Solar Corona’ by J. W. Knight,C. E. Newman,and P. A. Sturrock

Observational line width evidence for a possible discrepancy between ion and electron temperature in the corona is reviewed for comparison with the conclusions of Knight et al. We note that the high line-width temperatures extend much higher in the corona than the high ion temperatures computed by Knight et al., and suggest that a significant ion-electron temperature difference should be expected only near a steep temperature gradient, as in the transition region.     

H.E.S.S. observations of LS 5039

Recent observations of the binary system LS 5039 with the High Energy Stereoscopic System (H.E.S.S.) revealed that its Very High Energy (VHE) γ-ray emission is modulated at the 3.9 days orbital period of the system. The bulk of the emission is largely confined to half of the orbit, peaking around the inferior conjunction epoch of the compact object. The flux modulation provides the first indication of γ-ray absorption by pair production on the intense stellar photon field. This implies that the production region size must be not significantly greater than the gamma-gamma photosphere size (∼1 AU), thus excluding the large scale collimated outflows or jets (extending out to ∼1000 AU). A hardening of the spectrum is also observed at the same epoch between 0.2 and a few TeV which is unexpected under a pure absorption scenario and could rather arise from variation with phase in the maximum electron energy and/or the dominant VHE γ-ray production mechanism. This first-time observation of modulated γ-ray emission allows precise tests of the acceleration and emission models in binary systems. Mathieu de Naurois for the H.E.S.S. Collaboration.     

Radiative decay behind strong M.H.D. shocks

The effect of radiation up on the state of gas behind strong M.H.D. shock front has been studied. The jump conditions for flow variables across the shock boundary have been obtained and temperature decay behind the shock front is determined for a optically-thin brehmsstrahlung radiation plasma. It has been found that, for a shock within strong magnetic field, the temperature decay is much quicker.     

Comment on “Cosmogenic neon in grains separated from individual chondrules: Evidence of precompaction exposure in chondrules” by J. P. Das,J. N. Goswami,O. V. Pravdivtseva,A. P. Meshik,and C. M. Hohenberg

Das et al. (2012) claim that in several cases nominal cosmic ray exposure ages derived from concentrations of cosmogenic Ne in individual olivine grains separated from chondrules substantially exceed exposure ages of matrix samples. Some grains were also reported to show larger apparent exposure ages than other grains from the same chondrule. The authors conclude that the excesses were caused by an exposure of chondrules to high fluences of solar energetic particles and suggest that their data provide direct evidence for a highly active phase of the early Sun, similar to what is observed in X‐ray emissions of recent naked T‐Tauri stars. Here, we show that the production rates of cosmogenic Ne used by Das et al. (2012) to derive nominal cosmic ray exposure ages of their olivine grains are often much too low, as the reported major element concentrations in many cases sum up to considerably less than 100% even if converted to oxides. In contrast, adopted element concentrations for matrix samples are basically self‐consistent. A precompaction exposure of chondrules to a very high flux of solar energetic particles is thus not supported by the data presented by Das et al. (2012). Das et al. (2012) claim that in several cases nominal cosmic ray exposure ages derived from concentrations of cosmogenic Ne in individual olivine grains separated from chondrules substantially exceed exposure ages of matrix samples. Some grains were also reported to show larger apparent exposure ages than other grains from the same chondrule. The authors conclude that the excesses were caused by an exposure of chondrules to high fluences of solar energetic particles and suggest that their data provide direct evidence for a highly active phase of the early Sun, similar to what is observed in X‐ray emissions of recent naked T‐Tauri stars. Here, we show that the production rates of cosmogenic Ne used by Das et al. (2012) to derive nominal cosmic ray exposure ages of their olivine grains are often much too low, as the reported major element concentrations in many cases sum up to considerably less than 100% even if converted to oxides. In contrast, adopted element concentrations for matrix samples are basically self‐consistent. A precompaction exposure of chondrules to a very high flux of solar energetic particles is thus not supported by the data presented by Das et al. (2012).     

The Cosmological Scalar in the Jordan-Brans-Dicke Theory. II.

Cosmological solutions are examined in the proper representation of the JBD theory with a dominant nonminimally coupled scalar field. It is shown that only the introduction of a cosmological scalar that transforms to the ordinary cosmological constant in the Einstein representation enables a phase of evolution with a uniform and then an accelerated expansion of the universe over cosmological time scales. __________ Translated from Astrofizika, Vol. 48, No. 4, pp. 633–640 (November 2005).     

Young stars in gas-dust disks. I. Fomalhaut

This is a single-factor analysis of the variance of the average quasimonochromatic magnitudes of Fomalhaut, α PsA, in the 325-1080 nm spectral range for different observation seasons collected in the Pulkovo Spectrophotometric Data Base (PSDB). The overall variance of the data combined over several seasons is decomposed into components characterizing the randomness and variability factors separately. The influence of the variability factor on the variance of the average magnitudes is found to be significant with a confidence coefficient exceeding 95%. The estimated amplitude of the variability is 0^m.02-0^m.03. It is proposed that the main causes of the variability are photospheric pulsations (changes in the temperature by ~40 K and in the radius by ~0.5%) and variations in the scattering of radiation by dust in the circumstellar disk owing to the large scale inhomogeneity of the disk. Data from the Hipparcos catalog indicate a variability of the star in the Vt band with an amplitude of ~0^m.017 and a period of 20.6 days. It is suggested that the disk surrounding the star contains a region with an elevated concentration of particles which periodically eclipses the star as it undergoes Kepler rotation. Another explanation is also proposed: transit of an unknown planet across the star’s disk. The existence of a planet at a distance of ~0.2 a.u. will require further confirmation.     

C.T.R. Wilson and the cloud chamber

A brief history of C.T.R. Wilson’s invention of the cloud chamber is presented. Initially, the research programme concerned the origin of the atmospheric phenomena he had experienced as a temporary meteorological observer on Ben Nevis. As his understanding of the physical conditions under which the condensation of water droplets took place from supersaturated water vapour developed, he realised that the technique provided the first way of imaging the tracks of the charged particles released by X-rays, in radioactive decays and in nuclear interactions.     

High energy cosmic ray spectroscopy. III. Further analyses

In recent papers (A.D. Erlykin and A.W. Wolfendale, Astropart. Phys. 7 (1997) 1, 203) we presented evidence favouring the identification of “structure” in the size spectrum of cosmic ray electrons and muons with heavy nuclei originating in a single local, recent, supernova. Inevitably, such a claim, in a field that is notoriously difficult, has not met with universal agreement. In the present work we add more recent evidence and address the criticisms. Almot all of the evidence considered appears to support our claim; the remainder is neutral.     

Comments on the paper entitled: Turbulence,billows and gravity waves in a high shear region of the upper atmosphere by K.H. Lloyd,C.H. Low and R.A. Vincent

Some of the observational evidence which leads to the conclusion by Layzer and Bedinger (1969) that the small scale structure of high altitude vapor trails is not produced by preexisting atmospheric turbulence is recalled briefly in response to the recent report by Lloyd, Low and Vincent (1973). Specifically noted are: the difference in the structure of the ‘up’ and ‘down’ trails, the delay in appearance of the globular structure, and the equal frequency of occurrence of globules in regions of low and high wind shear. It is concluded that the observation presented by Lloyd, Low and Vincent does not alter our conclusion which is based on a large number of trails.     

Relative motions of fragments of the split comets.: I. A new approach

A new approach is formulated for the study of motions of the split comets. It is based on the assumption that two fragments of a comet separate at a rate that is determined primarily by a slight difference between their effective solar attractions rather than by the impulse imparted on them at the time of splitting. The net dynamical effect is interpreted as due to differential nongravitational forces, which depend on the size, density, structure, composition, and spin rate of the fragments. Since at least at smaller distances from the Sun these forces vary inversely as roughly the square of heliocentric distance, their dynamical effect resembles that of radiation pressure, so that the formalism developed for the motion of a dust particle in a cometary tail is applicable in principle. The calculations show that this approach provides reasonably good to excellent fits of the observed separations for a great majority of the split comets, and that it fails only in the case of Comet 1957 VI. The correlation between the differential nongravitational forces and the endurance of the fragment is investigated in terms of the physical behavior of the fragments, with the emphasis on the short-lived objects. Some of the unusual phenomena accompanying the split comets are discussed, and comments are also offered on the sequence of splitting for comets with multiple nuclei and on the distribution of the points of splitting in space.     

Variable features on Mars. VI. An unusual crater streak in Mesogaea

An unusual, prominent dark streak located in Mesogaea (near 8°N, 191°W) is described. Its appearance is unlike that of most dark streaks on Mars, many of which have ragged outlines, are variable on short time-scales, and are presumed to be erosional. The Mesogaea streak has a tapered, smooth outline, and no changes within it were observed. We suggest that this streak is depositional and that the low-albedo material originated within the associated crater itself. The source area is identified with a compact, low-albedo region on the crater floor. Two possible origins for the dark material are suggested: (1) deflation from a recently exposed, relatively unconsolidated subsurface deposit, and (2) production of ash by a volcanic vent.     

The Lissajous transformation II. Normalization

Normalization of a perturbed elliptic oscillator, when executed in Lissajous variables, amounts to averaging over the elliptic anomaly. The reduced Lissajous variables constitute a system of cylindrical coordinates over the orbital spheres of constant energy, but the pole-like singularities are removed by reverting to the subjacent Hopf coordinates. The two-parameter coupling that is a polynomial of degree four admitting the symmetries of the square is studied in detail. It is shown that the normalized elliptic oscillator in that case behaves everywhere in the parameter plane like a rigid body in free rotation about a fixed point, and that it passes through butterfly bifurcations wherever its phase flow admits non isolated equilibria.     

Comment on: Constraints on the depth and variability of the lunar regolith,by B. B. Wilcox,M. S. Robinson,P. C. Thomas,and B. R. Hawke

Abstract— Any permanent presence on the Moon will require use of materials from the lunar regolith, the surface soil layer on the Moon. Thus, knowledge of the thickness of the lunar regolith is essential. It has been proposed that crater counts obtained from high Sun angle photography give larger estimates of impact crater equilibrium diameters than for low Sun angle photography, and thus deeper estimates of lunar surface regolith than were previously made using crater morphology, size of blocky rimmed craters, and equilibrium diameters determined on low Sun angle images. The purpose of this comment is to evaluate this result as a means of resolving this important question before planning for future lunar missions is undertaken     

Total ozone measurements derived from T.O.V.S. radiances

A new method of total ozone retrieval from i.r. satellite data(NOAA6) is presented. It uses ozone transmittance as a predictor of total ozone. Ozone transmittance at 9.6 μm(TR) is deduced from radiance at 9.6 μm(R9), surface temperature (TS) measured at 11 μm, and ozone mean temperature (TE) estimated from several channels (among them 9.6 μm) by the radiative transfer equation : R9 = B(TS) × TR + (1?TR) × B(TE) where B is the Planck function.A statistical analysis of the retrieved ozone field and a comparison with ground based measurements show that the S.E. is less than 5% for the considered data set.