The Distribution and Significance of Evaporitic Weathering Products on Antarctic Meteorites

Abstract— The distribution of white evaporitic deposits differs among different meteorite compositional groups and weathering categories of Antarctic meteorites. Evaporites occur with unusual frequency on carbonaceous chondrites, and are especially common in carbonaceous chondrites of weathering categories A and B. Among achondrites, weathering categories A and A/B show the most examples of evaporite weathering. Unlike carbonaceous chondrites and achondrites, most evaporite-bearing ordinary (H and L) chondrites are from rustier meteorites of weathering categories B and, to a lesser degree, B/C and C. LL chondrites are conspicuous by their complete lack of any evaporitic weathering product. Almost two-thirds of all evaporite-bearing meteorites belong to weathering categories A, A/B, and B. Where chemical data are available, surficial evaporite deposits are associated with elemental anomalies in meteorite interiors. Meteorites of weathering classes B, A/B, and even A may have experienced significant element redistribution and/or contamination as a result of terrestrial exposure. Evaporite formation during terrestrial weathering cannot be neglected in geochemical, cosmochemical, and mineralogical studies of Antarctic meteorites. A lower-case “e” should be added to the weathering classification of evaporite-bearing Antarctic meteorites, to inform meteorite scientists of the presence of evaporite deposits and their associated compositional effects.     

Signals of collective behaviour in atmospheric showers

We discuss collective effects like percolation, quark gluon plasma, or string fusion and their effect on the longitudinal development of high energy showers in Air. It is shown that Iron–Air showers could develop more slowly than expected and produce the observed change in the slope of X_max at the highest energies.     

Near-IR spectral evolution of dusty starburst galaxies

We propose a multicomponent analysis of starburst galaxies, based on a model that takes into account the young and evolved stellar components and the gas emission, with their respective extinction, in the frame of a coherent dust distribution pattern. Near-IR signatures are preferentially investigated, in order to penetrate as deep as possible into the dusty starburst cores. We computed the 1.4-2.5 μm spectra of synthetic stellar populations evolving through strong, short timescale bursts of star formation (continuum and lines, R ? 500). The evolution model is specifically sensitive to cool stellar populations (AGB and red supergiant stars). It takes advantage of the stellar library of Lançon & Rocca-Volmerange (1992) [A&ASS, 96, 593], observed with the same instrument (FTS/CFHT) as the analysed galaxy sample, so that the instrumental effects are minimised. The main near-IR observable constraints are the molecular signatures of CO and H₂O and the slope of the continuum, observed over a range exceptionally broad for spectroscopic data. The H - K colour determined from the spectra measures the intrinsic stellar energy distribution but also differential extinction, which is further constrained by optical emission line ratios. Other observational constraints are the near-IR emission lines (Brγ, He I 2.06 μm, [Fe II] 1.64 μm, H₂ 2.12 μm) and the far-IR luminosity. The coherence of the results relies on the interpretation in terms of stellar populations from which all observable properties are derived, so that the link between the various wavelength ranges is secured. The luminosity L_K is used for the absolute calibration.We apply this approach to the typical spectrum of the core of NGC 1614. Consistent solutions for the starburst characteristics (star-formation rate, IMF, burst age, morphology) are found and the role of each observational constraint in deriving satisfactory models is extensively discussed. The acceptable contamination of the K band light by the underlying population amounts ≥ 15% even through a 5 arcsec aperture. The model leads to a limit on the direct absorption of Lyman continuum photons by dust situated inside the ionised areas, which in turn, with standard gas-to-dust ratios, translates into small characteristic sizes for the individual coexisting H II regions of the massive starburst area (clusters containing ∼ 10² ionising stars). We show that room is left for IMFs extending to 120 M_⊙, rather than truncated at ∼ 60 M_⊙ as most conservative studies conclude. High internal velocity dispersions (≥ 20 km s⁻¹) are then needed for the H II regions. An original feature of this work is to base the analysis of near-infrared spectral galaxy observations on a large wavelength range, using models constructed with spectral stellar data observed with the same instrument. However a broader use of this spectral evolution model on other spectral or photometric data samples is possible if the spectral resolution of the model is adapted to observations or if colours are derived from the energy distributions.Catherine J. Cesarsky     

Yohkoh/SXT observations of a coronal mass ejection near the solar surface

We report the observations of a coronal mass ejection (CME) using the Soft X-ray Telescope on board the Yohkoh Mission. The CME had the familiar three part structure (frontal loop, prominence core and a cavity). The erupting prominence was observed by the Nobeyama radioheliograph. We were able to determine the mass of the CME (2.6 × 10¹⁴ g) from X-ray observations which seems to be at the lower end of the range of CME masses reported before from white light observations. This is the first time the mass of a CME has been determined from X-ray observations. The height of onset of the CME was 0.3R_⊙. The CME moved much faster than the erupting prominence while its acceleration was smaller than that of the erupting prominence.J. Leonard Culhane     

Geochemical biosignature formation in experimental Martian fluvio-lacustrine and simulated evaporitic settings

To assess whether life existed on Mars, it is crucial to identify geochemical biosignatures that are relevant to specific Martian environments. In this paper, thermochemical modeling was used to investigate fluid chemistries and secondary minerals that would have evolved biotically over geological time scales in Martian fluvio-lacustrine and evaporitic settings, and that could be used as potential inorganic biosignatures for life detection on Mars. Modeling was performed using fluid and rock chemistries relevant to Gale crater aqueous environments. Potential inorganic biosignatures were identified investigating alteration deposits found at the surface of a simulant exposed to short-term bio-mediated weathering and comparing experimental and modeling results. In a fluvio-lacustrine setting (water/rock of 2000–278), models suggest that less complex mineral assemblages form during biotic basalt dissolution and subsequent brine evaporation compared to what would happen in an abiotic system. Mainly nontronite, kaolinite, and quartz form under biotic conditions, whereas celadonite, talc, and goethite would also precipitate abiotically. Quartz, sepiolite, and gypsum would precipitate from the evaporation of fluids evolved biotically, whereas nontronite, talc, zeolite, and gypsum would form in an abiotic evaporitic environment. These results could be used to distinguish products of abiotic and biotic processes, aiding the interpretation of data from Mars exploration missions.     

The time-scale for core collapse in spherical star clusters

The collapse time for a cluster of equal-mass stars is usually stated to be either 330 central relaxation times (t_rc) or 12-19 half-mass relaxation times (t_rh). But the first of these times applies only to the late stage of core collapse, and the second only to low-concentration clusters. To clarify how the time depends on the density profile, the Fokker-Planck equation is solved for the evolution of a variety of isotropic cluster models, including King models, models with power-law density cusps of ρ ∼ r^−γ, and models with nuclei. The collapse times for King models vary considerably with the cluster concentration when expressed in units of t_rc or t_rh, but vary much less when expressed in units of t_rc divided by a dimensionless measure of the temperature gradient in the core. Models with cusps have larger temperature gradients and evolve faster than King models, but not all of them collapse: those with 0 < γ < 2 expand because they start with a temperature inversion. Models with nuclei collapse or expand as the nuclei would in isolation if their central relaxation times are short; otherwise their evolution is more complicated. Suggestions are made for how the results can be applied to globular clusters, galaxies, and clusters of dark objects in the centers of galaxies.Scott D. Tremaine     

Lithium in black hole binaries: the case of X-ray Nova Muscae 1991

We report the detection of the LiI λ6708 resonance line in the K4V secondary of the black-hole binary Nova Muscae 1991. The LiI feature changes with orbital phase, being stronger (EW ∼ 400 mÅ) around φ = 0.0 (observing the dark side of the secondary) and weaker (EW ≤ 190 mÅ) around φ = 0.5 (observing the side facing the compact object). This effect is interpreted as LiI ionization induced by UV/X-ray illumination of the inner hemisphere of the companion star. From the strength of the LiI feature observed around φ = 0.0 we infer a photospheric lithium abundance of logN(Li) ∼ 3. This value should be considered in fact as a lower limit to the true Li abundance because we have not fully corrected for the LiI overionization expected from UV/X-ray illumination.High lithium abundances are becoming a common feature in the secondaries of black hole binaries. After the Li detections in V404 Cyg, A0620-00 and GS2000 + 25, our observations of Nova Muscae not only add a new case to the list, but also demonstrate the impact of irradiation on the formation of the LiI line for the first time. The LiI features observed in the other black hole binaries are probably also affected by irradiation, although not as strongly as in Nova Muscae, and their Li abundances are higher than previously thought.The most attractive scenario for explaining the origin of the high Li abundances in black hole binaries appears to be nucleosynthesis during the explosive accretion events that characterize these objects. We argue that our LiI detection in the secondary of X-ray Nova Muscae 1991, and the transient γ-ray narrow emission feature at 476 keV observed during the 1991 outburst, are both signatures of Li production around the black hole. We propose that the γ-ray emission line was due to ⁷Be electron capture which yielded excited ⁷Li atoms. This reaction is able to account for the central energy, narrow width and time scale of the observed γ-ray emission feature. The presence of Li on the surface of the secondary shows that Li atoms created during the outburst can escape and enrich the interstellar medium.Shrinivas Kulkarni     

Beta-carotene—A possible biomarker in the Martian evaporitic environment: Raman micro-spectroscopic study

Due to the discovery of the evaporitic environment on the Martian surface, there is a reasonable possibility that evaporites served (or still serve) as habitats for microbial life if ever present on Mars. At the very least, if no signatures of extant life exist within these rocks, it may sustain molecular remnants as evidence for living organisms in the past. β-Carotene, among other carotenoids, could be such a suitable biomarker. In this study, Raman micro-spectroscopy was tested as a nondestructive method of determining the presence of β-carotene in experimentally prepared evaporitic matrices. Samples prepared by mixing β-carotene with powdered gypsum (CaSO₄·2H₂O), halite (NaCl) and epsomite (MgSO₄·7H₂O) were analyzed using a 785 nm excitation source. Various concentrations of β-carotene in the matrices were investigated to determine the lowest β-carotene content detectable by Raman micro-spectroscopy. Mixtures were also measured with a laser beam permeating the crystals of gypsum and epsomite in order to evaluate the possibility of identifying β-carotene inside the mineral matrix.We were able to obtain a clear β-carotene signal at the 10 mg kg⁻¹ concentration level—the number of registered β-carotene Raman bands differed depending on the particular mineral matrix. Spectral signatures of β-carotene were detected even when analyzing samples containing 1 mg kg⁻¹ of this molecule. The 10-100 mg kg⁻¹ of β-carotene in mineral matrices (halite, epsomite) was detected when analyzed through the monocrystal of gypsum and epsomite, respectively. These results will aid both in-situ analyses on Mars and sample analyses on Earth.     

Constraining the power spectrum using clusters

We analyze an extended redshift sample of Abell/ACO clusters and compare the results with those coming from numerical simulations of the cluster distribution, based on the truncated Zel'dovich approximation (TZA), for a list of eleven dark matter (DM) models. For each model we run several realizations, so that we generate a set of 48 independent mock Abell/ACO cluster samples per model, on which we estimate cosmic variance effects. Other than the standard CDM model, we consider (a) Ω₀ = 1 CDM models based on lowering the Hubble parameter and/or on tilting the primordial spectrum; (b) Ω₀ = 1 Cold + Hot DM models with 0.1 ≤Ω_ν ≤0.5; (c) low-density flat ΛCDM models with 0.3 ≤Ω₀ ≤0.5. We compare real and simulated cluster distributions by analysing correlation statistics, the probability density function, and supercluster properties from percolation analysis. We introduce a generalized definition of the spectrum shape parameter Γ in terms of σ₂₅/σ₈, where σ_ris the rms fluctuation amplitude within a sphere of radius r. As a general result, we find that the distribution of galaxy clusters provides a constraint only on the shape of the power spectrum, but not on its amplitude: a shape parameter 0.18 Γ 0.25 and an effective spectral index at the 20 h⁻¹ Mpc scale −1.1 n_eff −0.9 are required by the Abell/ACO data. In order to obtain complementary constraints on the spectrum amplitude, we consider the cluster abundance as estimated using the Press-Schechter approach, whose reliability is explicitly tested against N-body simulations. By combining results from the analysis of the distribution and the abundance of clusters we conclude that, of the cosmological models considered here, the only viable models are either Cold + Hot DM ones with 0.2 Ω_ν 0.3, better if shared between two massive ν species, and ΛCDM ones with 0.3 Ω₀0.5.     

The environment of early Mars and the missing carbonates

Abstract– A model is presented in which the aqueous conditions needed to generate phyllosilicate minerals in the absence of carbonates found in the ancient Noachian crust are maintained by an early CO₂‐rich atmosphere, that, together with iron (II) oxidation, would prevent carbonate formation at the surface. After cessation of the internal magnetic dynamo, a CO₂‐rich primordial atmosphere was stripped by interactions with the solar wind and surface conditions evolved from humid to arid, with ground waters partially dissolving subsurface carbonate and sulfide minerals to produce acid‐sulfate evaporitic deposits in areas with upwelling ground water. In a subsequent geochemical state (Late Noachian to Hesperian), surface and subsurface acidic solutions were neutralized in the subsurface through interaction with basaltic crust, allowing the precipitation of secondary carbonates. This model suggests that, in the early Noachian, the surface waters of Mars maintained acidity because of a drop in temperature. This would have favored increased dissolution of CO₂ and a reduction in atmospheric pressure. In this scenario, physicochemical conditions precluded the formation of surface carbonates, but induced the precipitation of carbonates in the subsurface.     

Wisp motions in the Crab nebula

We present the results of a CCD monitoring campaign of the continuum emission from the central region of the Crab nebula, amounting to 17 epochs spread over 3.5 years. The data provide clear evidence that the brightest wisps move outward from the pulsar at mildly relativistic velocities. This motion, combined with the shape of the wisps, supports the idea that they arise at a standing shock in an equatorial wind. The deprojected velocity of the wisps in the equatorial plane is c/3. We see only small changes in the so-called ‘thin wisps’ which leads us to suggest that these wisps may be the result of a back-flow from the shock in a toroidal cavity around the pulsar.     

Dynamical supersymmetric inflation

We propose a new class of inflationary models in which the scalar field potential governing inflation is generated by the same nonperturbative gauge dynamics that may lead to supersymmetry breaking. Such models satisfy constraints from cosmic microwave background measurements for natural values of the fundamental parameters in the theory. In addition, they have two particularly interesting characteristics: a “blue” spectrum of scalar perturbations, and an upper bound on the total amount of inflation possible.     

Molecular hydrogen in the central regions of southern infrared galaxies

An extensive set of molecular hydrogen observations of centers of southern infrared galaxies is presented. Our data are combined with published infrared and radio observations to investigate the relationship between nuclear and circumnuclear activity. We convert the observational data to absolute luminosities, by applying the known distances. The resulting dataset covers several decades in luminosity for the various parameters, which observe fairly tight correlations. The parameters of our (power law) fits are, at the level of accuracy achieved, not dependent on the type of nuclear activity: while the dataset comprises a mixture of alleged Seyfert, Liner & starburst galaxies, single fits match the complete sample well enough. In particular, non-thermal nuclei (AGN) present in some of the galaxies in the current sample, do not stand out in the parameters we investigated. The absence of a significant dependence on the nuclear type is consistent with the idea that the ever present starbursts energetically dominate a possible ‘AGN in a dusty environment’-component in most galaxy nuclei with infrared excesses.The size of the H₂ emitting region is found to be proportional to the square root of the 21 cm radio continuum luminosity. The excitation of the circumnuclear H₂ is dominated by shocks. If the H₂ extent marks the size of an inner cavity in the dense molecular material surrounding a galaxy nucleus and the radio luminosity is proportional to the mechanical luminosity of (circum)nuclear winds. This result then indicates that the cavity size occurs at constant pressure in the sample galaxies, in accordance with the superwind model by Heckman et al. (1990) [ApJS, 74, 833]. Our results, together with those obtained by others, thus suggest that luminosities and size scales of excited gas associated with active nuclei are dominated by the mechanical energy input. Given the difficulties of uniquely establishing the presence of an AGN, we cannot exclude that (a large fraction of the) infrared luminous galaxies procure part of their radiated energy through accretion onto a massive dark object.F. Duccio Macchetto     

A Research on the Algorithm of Local Atomic Time

The goal of all time laboratories’ pursue is to produce and keep a stable, precise and reliable time scale. The long-term stability of the time scale is mainly taken into account in the traditional ALGOS algorithm, while the local atomic time scale should give consideration to both the long-term and shortterm stabilities. From the analysis and research on the atomic clock noise model and under the condition that the long-term stability of the local atomic time scale does not drop, a complete algorithm is proposed which is suitable for the calculation of the local time scale TA (NTSC) carried out at the time laboratory with the time-keeping clocks of a unitary type and being close in performance at the National Time Service Center, called the NTSC for short, of Chinese Academy of Sciences. The data of all the clocks in the NTSC which participated in the calculation of the International Atomic Time (TAI) all the year round in 2008 are applied to the test and verification of the new algorithm, with the result showing that both the short- and long-term stability indexes of the obtained TA (NTSC) are improved. The research result is suitable for the calculation of the atomic time scale of the time laboratory whose time keeping system is similar to that of the NTSC.     

Four-neutrino mixing and Big-Bang Nucleosynthesis

We investigate the Big-Bang Nucleosynthesis constraints on the elements of the neutrino mixing matrix which connect sterile with massive neutrino fields, in the framework of the two four-neutrino schemes that are favored by the results of neutrino oscillation experiments. We discuss the implications of these constraints for terrestrial short and long-baseline neutrino oscillation experiments and we present several possibilities of testing them in these experiments. In particular, we show that from the Big-Bang Nucleosynthesis constraints it follows that the transition is severely suppressed in short-baseline experiments, whereas its oscillation amplitude in long-baseline experiments is of order 1. We also propose a new parameterization of the four-neutrino mixing matrix U which is appropriate for the schemes under consideration.     

Remote sensing and geological studies of the Hadley‐Apennine region of the Moon

Abstract— We have used data from the Clementine and Lunar Prospector spacecraft in conjunction with reflectance spectra collected with Earth‐based telescopes to study the geology of the Hadley‐Apennine portion of the lunar Imbrium basin. The Apennine Mountains and the Imbrium backslope are composed of Imbrium basin ejecta with a noritic or anorthositic norite composition. We find that the two major facies of Imbrium ejecta, the Apenninus material and the Alpes Formation, differ in iron and titanium content. “Pure” anorthosite has tentatively been identified in the ejecta of the crater Conon, based on low‐iron content. A difference in Th and rare earth element (REE) abundance between the northeast Apennine Mountains (lower) and the southwest Apennines (higher) is noted. Pyroclastic deposits are common in the region and are dominated by mare basalt material, probably plug rock ejected in vulcanian eruptions. The Apennine Bench Formation, which is likely to be a deposit of non‐mare volcanic material, has an Fe, Ti and Th composition consistent with that of Apollo 15 KREEP basalt samples thought to be fragments of the Bench. Aristillus crater is a Th and REE hot spot, and the stratigraphy of the impact target site has been reconstructed from knowledge of the composition of the crater interior and exterior deposits. We infer that the target consisted of highland basement, KREEP plutonics and volcanics, and both high‐ and low‐Ti mare basalt.     

The mass ratio of Nova Muscae 1991

We report intermediate resolution H spectroscopy of the black hole candidate Nova Muscae 1991 during quiescence. We classify the companion star as a K3-K4V which contributes 85±6 percent to the total flux from the binary. The photospheric absorption lines are broadened by 106±13 kms⁻¹ with respect to template field stars, leading to a system mass ratio of q =M₁/M₂ = 7.8_−2.0^+3.4. Doppler imaging of the H line shows strong emission coming from the secondary star (EW=3.1±0.6Å) which we associate with chromospheric activity. However, the hot-spot is not detected and this may indicate a lower mass transfer rate than in other X-ray transients of comparable orbital periods. The surface brightness distribution of the accretion disk in H follows a relation I∝R^−1.1, less steep than typically observed in cataclysmic variables. Updated system parameters are also presented.     

Near-infrared surface photometry of bulges and disks of spiral galaxies. The data

We present optical and near-infrared (NIR) surface brightness and colour profiles, in bands ranging from U to K, for the disk and bulge components of a complete sample of 30 nearby S0 to Sbc galaxies with inclinations larger than 50 °. We describe in detail the observations and the determination of colour parameters. Calibrated monochromatic and real-colour images are presented, as well as colour index maps. This data set, tailored for the study of the population characteristics of galaxy bulges, provides useful information on the colours of inner disks as well. In related papers, we have used them to quantify colour gradients in bulges, and age differentials between bulge and inner disk.     

Evolution of cold shock-bounded slabs

The stability and evolution of cold, shock-bounded slabs is studied using numerical hydrodynamic simulations. We confirm the analysis of Vishniac (1994) [ApJ, 428, 186], who showed that such slabs are unstable if they are perturbed by a displacement larger than their width. The growth rate of this nonlinear thin shell instability (NTSI) is found to increase with decreasing wavelength, in qualitative agreement with Vishniac's analysis. The NTSI saturates when the bending angle becomes large and the growth in the width of the slab pinches off the perturbation. After saturation, the slab remains greatly extended with an average density much less than the original slab density, supported primarily by supersonic turbulence within the slab. Linear perturbations are also found to be unstable in that they can lead to turbulent flow within the slab, although this response to linear perturbations is distinct from, and much less violent than the NTSI.Richard McCray