results from the mars global surveyor thermal emission spectrometer the thermal emission spectrometer spectra of low albedo surface materials suggests that a four to one mixture of pyroxene to plagioclase together with about a 35 percent dust component provides the best fit to the spectrum qualitative upper limits can be placed on the concentration of carbonates 10 percent olivine 10 percent clay minerals 20 percent and quartz 5 percent in the limited regions observed limb observations in the northern hemisphere reveal low lying dust hazes and detached water ice clouds at altitudes up to 55 kilometers at an aerocentric longitude of 224 degrees a major dust storm developed in the noachis terra region the south polar cap retreat was similar to that observed by viking

application of the sphalerite cosmobarometer to the enstatite chondrites sphalerite is a minor constituent of a number of enstatite chondrites the assemblage sphalerite troilite kamacite buffers the iron content of sphalerite so that it is a function of temperature and pressure only high iron contents in sphalerite in enstatite chondrites are consistent with equilibration at low pressures if nebular conditions are assumed and pressure is taken as zero it is then possible to calculate blocking temperatures for diffusion of iron t b and cooling rates for the meteorites studied the variable degree of equilibration of eh3 chondrites is correlated with calculated pressures assuming that the least equilibrated y69001 formed at zero pressure parent body radii calculated from these pressures are probably too large however inhomogeneities and minor elements in sphalerite as well as the assumptions made in the calculation may have had an adverse effect on the calculations the eh4 chondrite indarch appears to have cooled at an extremely rapid rate and has an unreasonably high t b inhomogeneities and minor element content may again have affected results the data for the el6 chondrites are consistent with relatively slow cooling ca 773 k whereupon rapid cooling occurred cooling rates at 773 k are too fast by a factor of 102 to 103 in comparison with metallographically determined rates

topographic connections with density waves in mars aerobraking regime 1 atmospheric densities derived from measured acceleration of several mars orbiters reveal large amplitude sun synchronous longitudinal density variations at altitudes of about 100 160 km these variations are associated with vertically propagating nonmigrating solar thermal tides that are excited near mars surface and propagate into the thermosphere excitation of these waves is associated with the zonally asymmetric component of the near surface heating distribution and is commonly attributed to topographic modulation of solar heating however there are other possible contributors to the excitation of nonmigrating tides including zonal variations in surface properties and wave wave nonlinear interactions whose relative contributions remain unexplored in this study we use a general circulation model in combination with the mars global surveyor accelerometer measurements to isolate the different waves responsible for the observed density structures while it is evident that topography accounts for most of the waves amplitudes the surface thermal inertia and albedo are found to have a nonnegligible contribution to the eastward propagating diurnal tide with zonal wave number s 1 and the standing s 0 diurnal tide previous studies have reported the dominance of wave numbers 2 and 3 in the resulting sun synchronous aerobraking density maps we show that wave number 1 has a comparable amplitude and is mostly the result of mapping the diurnal standing wave into a near sun synchronous orbit while most of the nonmigrating tides at thermospheric altitudes are generated by an interaction between the migrating solar radiation and the dominant topography harmonics we also find that wave wave interaction is necessary to explain some of the observed density features

numerical simulation and evaluation of groundwater resources in a fractured chalk aquifer a case study in zinder well field niger groundwater is often a unique water source for agriculture industry and domestic use for local inhabitants in semi arid african continent owing to shortage of surface water and rainfall it is of significance to quantify and assess the groundwater resources for local sustainable development in order to correctly evaluate groundwater resources of zinder well field with fractured media in zinder niger a conceptual model of hydrogeology was set up by a geological and hydrogeological survey for simulating the real conditions a large multi well pumping test with designed pumping rate was conducted in addition a two dimensional finite element transient flow model was developed to simulate groundwater flow at the site results show that generally good agreements have been found between the simulated and observed hydrogeology heads for the test the hydraulic parameters were obtained from the pumping test a 11 year prediction of groundwater resources has been made under three exploitation schemes respectively and it indicates that the well field can offer 7 000 m3 day when the aquifer remains confined an optimal scheme of exploitation is provided

new chemical and physical data on keilite from the zaklodzie enstatite achondrite keilite fe mn mg ca cr s from the zaklodzie enstatite achondrite is described forming xenomorphic grains up to 0 5 mm in diameter the keilite is associated with troilite or pyrrhotite fe ni metal an fe zn mn s phase enstatite with relict forsterite in cores plagioclase and accessory schreibersite oldhamite graphite sinoite and an sio2 polymorph it is brittle and possesses a good cleavage similar to that of galena parallel to 001 010 and 100 x ray diffraction structural data reveal the following cubic space group fm3m 90 a 5 1717 18 a unit cell volume v 138 32 8 a 3 d 3 958 g cm 3 z 4 the chemical formula based on 63 electron microprobe point analyses is fe0 437 mn0 356 mg0 160 ca0 017 cr0 019 zn0 001 s1 008 compared with previously described keilites from enstatite chondrites the zaklodzie keilite is richer in mn ca cr s and poorer in the fe and mg end members and consequently it is nearer to alabandite and oldhamite this is the rst detailed description of keilite from a meteorite that is not an enstatite chondrite

presolar diamond sic and graphite in primitive chondrites abundances as a function of meteorite class and petrologic type abstract acid resistant residues were prepared for eighteen meteorites from seven chondrite classes using improved procedures designed to minimize loss of presolar grains noble gases were measured by stepped pyrolysis and the abundances of five exotic noble gas components were used to determine abundances of diamond sic and graphite diamond separates were prepared to check diamond abundances determined from noble gases diamond and sic were found in unmetamorphosed members of all seven chondrite classes and evidence for graphite was found in orgued ci and ll3 0 3 1 chondrites our data and noble gas and stable isotope data in the literature show that presolar grains were incorporated into all chondrite classes the grains are sited in the fine grained matrix and their abundances within the matrix reflect mainly the degree of metamorphism suffered by the host meteorite the pattern of metamorphic destruction differs from class to class in unequilibrated ordinary chondrites uocs graphite is most easily destroyed followed by sic and then diamond no presolar grains remain in uocs of petrologic type 3 8 whose matrices have been completely recrystallized in eh chondrites diamond and sic survive much more severe metamorphism than in uocs with sic apparently more stable than diamond presolar graphite was not detected in cv3 and c03 chondrites diamond appears to be more stable than sic and graphite again is missing inferred premetamorphic diamond abundances matrix normalized vary by a factor of 2 2 between classes with eh cv and co chondrites having higher initial abundances than orgueil similar diamond sic ratios are observed in most classes and differences in the ratio can be tied to secondary processing suggesting that all chondrite classes sampled the same solar system wide reservoir of presolar grains differences in initial abundances between classes appear to correlate with chemical and physical properties of the host meteorites these bulk properties and variations in presolar grain abundances both may be the result of thermal processing of presolar dust in the accretion disk

thermal history of the enstatite chondrites from silica polymorphs here we report the results of our petrologic and mineralogical study of enstatite e chondrites in order to explore their thermal histories we studied silica phases in 20 e chondrites by laser micro raman spectroscopy to determine the silica polymorphs they contain silica phases are commonly present in e chondrites and their polymorphs reflect the physical conditions of formation the samples studied here include eh3 5 el3 6 e chondrite melt rocks and an anomalous e chondrite we identified quartz tridymite cristobalite and silica glass in the samples studied eh4 5 and eh melt rocks are divided into high and low temperature classes based on niningeritealabandite solid solutions eh3 el3 and some eh melt rocks of the high temperature class contain tridymite and cristobalite we suggest that tridymite and cristobalite crystallized in chondrules and e chondrite melts followed by rapid cooling leading to the survival of these silica polymorphs eh4 and el4 chondrites also contain tridymite and cristobalite in their chondrules indicating that these silica polymorphs survived low temperature metamorphism as estimated from opaque mineral geothermometers because of the sluggishness of the transition to a more stable polymorph tridymite and cristobalite in el6 chondrites reflect the high temperature processes experienced by these meteorites on the other hand some eh5 chondrites and eh melt rocks of the low temperature class contain quartz which may be a product of the transition from tridymite or cristobalite during a long period of low temperature metamorphism although the thermal history of e chondrites have been previously estimated from opaque minerals such compositions mainly reflect low temperature processes however we can reconstruct the primordial thermal processes and subsequent cooling histories of e chondrites from their silica polymorphs the e chondrites have complicated thermal histories which produced the observed variations among them

simulated planetary wave tide interactions in the atmosphere of mars 1 this study is a first attempt to simulate the nonlinear interactions between planetary waves and tides in the atmosphere of mars and to examine the consequences of the secondary waves that result from these interactions recent analysis of aerobraking densities show clear signatures of secondary waves produced by the modulation of tides by planetary waves the vertically propagating secondary waves serve to modulate longitudinal density structures due to nonmigrating tides at planetary wave periods even in the local absence of planetary waves in this parametric study using a general circulation model of mars we determine the most important waves produced by these interactions and quantify their induced variability at aerobraking altitudes

an experimental investigation of hydraulic behaviour of fractures and joints in granitic rock a method of measuring mean mechanical aperture of fractures based on gas volume balance is introduced the effects of shear displacement and normal stress on mechanical and hydraulic behaviour of fractures are also investigated the results obtained from tests conducted on granite samples from olympic dam central australia are compared with those calculated from existing shear dilation theories it is found that hydraulic aperture is considerably narrower than the measured mean mechanical aperture this highlights the need to consider tortuosity and surface roughness of fractures in the calculation of hydraulic aperture it is also found that shear dilation angle decreases linearly with increases in confining pressure as opposed to more rapid decreases predicted by existing empirical models from the results of this study a range of data describing the relationships between confining pressure shear displacements hydraulic aperture and permeability are presented which could help to develop stimulation programs for geothermal reservoirs

effects of melt viscosity and silica activity on the rate and mechanism of quartz dissolution in melts of the cmas and cas systems the dissolution rate of quartz in melts of the cmas and cas systems at 1 600 c and 1 5 gpa is a function of both the silica activity of the melt and its viscosity in melts with low silica activity quartz dissolves more quickly than in higher asio2 melts regardless of viscosity for melts with equal asio2 dissolution is faster in the low viscosity melt quartz dissolution is controlled by interface kinetics in three of the four melts used in this study for times much greater than predicted by the model of zhang et al in contrib mineral petrol 102 492 513 1989 one melt which was previously shown to adhere to the predicted behaviour at lower temperature shows a significant activation time at higher temperature all the dissolution data indicate that there are likely to be three distinct domains of dissolution behaviour although the details of why a particular melt falls in any one domain require further study although the current database is small the relationship between quartz solubility and the dissolution constant indicate that solubility may be a useful parameter for predicting dissolution rates particularly if silica activity and melt viscosity are also known

quantitative three dimensional description of a rough surface and parameter evolution with shearing note roches reference lmr article 2002 005view record in web of science record created on 2006 11 09 modified on 2016 08 08

thermal tides during the 2001 martian global scale dust storm the 2001 mars year 25 global dust storm radically altered the dynamics of the martian atmosphere using observations from the thermal emission spectrometer onboard the mars global surveyor spacecraft and marswrf general circulation model simulations we examine the changes to thermal tides and planetary waves caused by the storm we find that the extratropical diurnal migrating tide is dramatically enhanced during the storm particularly in the southern hemisphere reaching amplitudes of more than 20 k the tropical diurnal migrating tide is weakened to almost undetectable levels the diurnal kelvin waves are also significantly weakened particularly during the period of global expansion at ls 200 210 in contrast the westward propagating diurnal wavenumber 2 tide strengthens to 4 8 k at altitudes above 30 km the wavenumber 1 stationary wave reaches amplitudes of 10 12 k at 50 70 n far larger than is typically seen during this time of year the phase of this stationary wave and the enhancement of the diurnal wavenumber 2 tide appear to be responses to the high altitude westward propagating equatorial wavenumber 1 structure in dust mixing ratio observed during the storm in previous works this work provides a global picture of dust storm wave dynamics that reveals the coupling between the tropics and high latitude wave responses we conclude that the zonal distribution of thermotidal forcing from atmospheric aerosol concentration is as important to understanding the atmospheric wave response as the total global mean aerosol optical depth

numerical modelling of borehole water inflow tests in the foundation of the alqueva arch dam borehole water inflow tests allow measurement of discharges and water pressures in isolated sections of drains and piezometric boreholes a series of water inflow tests and water electrical conductivity analyses were carried out in an area of the foundation of an arch dam detailed three dimensional 3d numerical models developed for the analyses of the test data in two foundation areas are presented results of rock mass permeability tests and areas where seepage paths cross each drain identified with both water inflow tests and water electrical conductivity analyses were taken into account models were validated against flow rates and water pressures recorded in situ by examining water inflow tests using numerical models the main flow processes are identified and quantified test results and conclusions drawn from the detailed 3d models were used to elaborate a global model of the foundation the present study shows that borehole water inflow tests add valuable information to the usual monitoring d

numerical simulations examining the relationship between wall roughness and fluid flow in rock fractures understanding how fracture wall roughness affects fluid flow is important when modeling many subsurface transport problems computed tomography scanning provides a unique view of rock fractures allowing the measurement of fracture wall roughness without destroying the initial rock sample for this computational fluid dynamics study we used several different methods to obtain three dimensional meshes of a computed tomography scanned fracture in berea sandstone these volumetric meshes had different wall roughnesses which we characterized using the joint roughness coefficient and the fractal dimension of the fracture profiles we then related these macroscopic roughness parameters to the effective flow through the fractures as determined from navier stokes numerical models thus we used our fracture meshes to develop relationships between the observed roughness properties of the fracture geometries and flow parameters that are of importance for modeling flow through fractures in field scale models fractures with high joint roughness coefficients and fractal dimensions were shown to exhibit tortuous flow paths be poorly characterized by the mean geometric aperture and have a fracture transmissivity 35 times smaller than the smoother modeled fracture flows

numerical study of flow anisotropy within a single natural rock joint the paper investigates the flow anisotropy within a natural joint subjected to mechanical shear the cubic law is the simplest way to describe fluid flow through rock joints but because of rock wall roughness deviations from this model have been observed the reynolds equation usually gives better results in this study micro scale roughness is taken into account to define a reduced coefficient of permeability numerical simulations have been carried out by applying darcy s law to the rock joint described as an equivalent porous medium the numerical simulations are based on experimental data obtained by hans phd grenoble 2002 from a series of hydromechanical shear tests on a rock joint replica the numerical results have been compared to the experimental ones and to the results obtained by applying the reynolds equation to assess the relevance of the simulations for the fracture studied the approach proposed herein can reproduce relatively well the experimental flow anisotropy and provides consistent values of flow rates whereas the reynolds equation tends to give higher flow rates

mars atmospheric dynamics as simulated by the nasa ames general circulation model 2 transient baroclinic eddies a large set of experiments performed with the nasa ames mars general circulation model gcm have been analyzed to determine the properties structure and dynamics of the simulated transient baroclinic eddies the mars gcm simulations span a wide range of seasonal dates and dust loadings and include a number of special sensitivity experiments e g with flat topography there is strong transient baroclinic eddy activity in the extratropics of the northern hemisphere during the northern autumn winter and spring seasons the eddy activity remains strong for very large dust loadings though it shifts northward the eastward propagating eddies are characterized by zonal wavenumbers of 1 4 and periods of 2 10 days in several simulations the eddy variance is dominated by a single zonal wavenumber and a narrow range of periods the longer wavenumbers 1 and 2 transient eddies have a very deep vertical structure exhibiting a maximum kinetic energy density at the model top 45 50 km in many of the simulations in a simulation for early northern spring the eddies are quite shallow however the transient eddies generate the bulk of their energy baroclincally via large meridional and vertical heat fluxes at both lower and upper levels this is despite the fact that their vertical structure is typically close to equivalent barotropic above the lowest 10 km the eddies also appear to generate a substantial amount of energy barotropically via large meridional momentum fluxes at both lower and upper levels in the tropics and northern subtropics at upper levels 25 50 km there are strong transient eddy motions with structures resembling those characteristic of inertially unstable modes this eddy activity appears to be a response to the forcing of a region of marginal inertial stability by the extratropical transient baroclinic eddies as the wavenumbers and periods are the same as those in the extratropics a major surprise is the presence of very weak transient eddy activity in a number of the southern winter simulations it appears that this is partly a consequence of the stabilizing effects of the zonally symmetric topography in the gcm but it also must be associated with certain aspects of the zonal mean circulation in southern winter this is indicated by the presence of relatively large amplitude eddies in simulations for early southern autumn and spring and in a southern winter solstice simulation incorporating a different topography derived from the mars digital terrain model this topography differs from that used in most of the gcm simulations in not being characterized by steep symmetric slopes which are stabilizing to baroclinic instability in southern high latitudes it is hypothesized that the very large extent of the southern seasonal polar cap and high elevations in the south both might contribute to weakening the transient eddy activity large zonally symmetric topography in the northern hemisphere of the mars gcm also appears to have a strong impact on the transient eddies acting to increase the dominant zonal wavenumbers and phase speeds the properties of the gcm baroclinic eddies in the northern extratropics are compared in detail with analogous properties inferred from viking lander meteorology observations the gcm eddies are found to be very similar to those observed in most respects a notable exception is that the eddy amplitudes in the highly dusty gcm simulations are much larger than those observed by viking during the 1977 winter solstice dust storm this is almost certainly at least partly due to the relatively small latitudinal expansion of the hadley circulation in the highly dusty gcm experiments

the zaklodzie enstatite meteorite mineralogy petrology origin and classification the zaklodzie meteorite was found in september 1998 about 40 km west of zamo c in southeast poland macroscopic and microscopic observations in transmitted and reflected light microprobe analyses cathodoluminescence images and x ray diffraction data show that the meteorite is composed of clino and orthoenstatite two generations of feldspars relict olivine forsterite a polymorph of sio2 apparently cristobalite and opaque minerals fe ni alloy kamacite and taenite troilite schreibersite graphite and sulfide mg mn fe s which is probably keilite the texture is fine to inequigranular of cumulate type locally intergranular the mgs fes thermometer indicates that the sulfides crystallized at 580 600 oc thus the zaklodzie meteorite formed by the nearly complete melting of an enstatite chondrite protolith probably at 4 4 ga the process was likely caused by the decay of the 26al nuclide in the planetesimal interior the second stage of its evolution which could have happened at 2 1 ga involved partial re melting of most fusible components probably due to collision with another body the structure composition and origin of the meteorite and its relation to the parent rock indicate that zaklodzie may represent a primitive enstatite achondrite

metallic minerals thermal histories and parent bodies of some xenolithic ordinary chondrite meteorites we have studied metal grains in the hosts and lithic fragments of widely differing petrologic types in four xenolithic chondrftes using reflected light microscopy and electron probe analysis in weston and fayetteville which both contain solar flare tracks and solar wind gases kamacite taenite and tetrataenite ordered feni and troilite show a variety of textures on a wood plot of central ni content vs dimension taenite analyses scatter as if metal grains cooled at rates of 10 1000 and 1 100 k myr respectively through 700 k although metal in an h6 clast in fayetteville plots coherently with a cooling rate of 50 k myr we propose that metal grains cooled at these rates in chondritic clasts at different locations before host and clasts were compacted and were not subsequently heated above 650 k we predict a similar history for all gas rich ordinary chondrites by contrast metallic minerals throughout bhola and mezo madaras show more uniform textures and plot coherently giving cooling rates in the range 750 to 600 k of 0 1 and 1 k myr respectively we conclude that host and xenoliths in both chondrites were slowly cooled after compaction thus clasts in these chondrites experienced peak metamorphic temperatures and slow cooling through 700 k in different environments according to the conventional onion shell model for h l or ll chondrite parent bodies material of petrologic types 3 5 was arranged in successive shells around a type 6 core prior to catastrophic collisions which mixed all types intimately but if peak metamorphic temperatures were reached during not after accretion as seems plausible maximum metamorphism may have occurred in planetesimals 10 km in radius cooling through 700 k may then have occurred in larger bodies that accreted from these planetesimals iron meteorites mesosiderites and some achondrites may also have experienced melting in planetesimals and slow cooling in larger bodies

evidence for nonmigrating thermal tides in the mars upper atmosphere from the mars global surveyor accelerometer experiment 1 mars global surveyor accelerometer experiment density measurements indicate the presence of planetary scale wave structure in the mars upper atmosphere 130 km in particular phase 2 aerobraking observations reveal large amplitude zonal wave 2 and 3 variations in dayside density between 60 latitude these spatial variations in a fixed local solar time reference can be qualitatively reproduced by a mars general circulation model and are identified as a manifestation of eastward propagating nonmigrating thermal tides with long vertical wavelengths the simulated wave 2 variation is dominated by a diurnal period wave 1 kelvin mode while the principal components of the simulated zonal wave 3 structure are a diurnal period wave 2 kelvin mode and a wave 1 semidiurnal tide the characterization of these waves is important for understanding the structure and variability of the martian atmosphere at aerobraking altitudes

single fractures under normal stress the relation between fracture specific stiffness and fluid flow abstract fracture specific stiffness and fluid flow through a single fracture under normal stress are implicitly related through the geometry of the void space and contact area that comprise the fracture data from thirteen different rock samples each containing a single fracture show that relationships between fracture specific stiffness and fluid flow through a fracture fall into two general classes of behavior fractures either fall on a loosely defined universal curve relating fluid flow to fracture specific stiffness or else the flow is weakly dependent on fracture specific stiffness the second relationship shows that flow decreases slowly with increasing fracture specific stiffness the first relationship shows that flow decreases rapidly for increases in fracture specific stiffness to understand this behavior computer simulations on simulated single fractures were performed to calculate fluid flow fracture displacement and fracture specific stiffness as a function of normal stress simulated fractures with spatially correlated and uncorrelated aperture distributions were studied fractures with spatially uncorrelated aperture distributions tend to exhibit a weak dependence of fluid flow on fracture specific stiffness because these fractures tend to have multiple connected paths across the sample which can support flow with uniformly distributed contact area thus an increment in stress will increase the stiffness of the fracture without greatly reducing the amount of fluid flow on the other hand fractures with spatially correlated aperture distributions tend to belong to the universal relationship because correlated fractures tend to have only one or two dominant flow paths and the contact area is limited to a few regions resulting in a compliant fracture thus an increment in stress on a spatially correlated fracture will result in an increase in stiffness and rapid decrease in fluid flow these spatial correlations in fracture void geometry can be differentiated in the laboratory based on the observed fracture specific stiffness fluid flow relationship for a single fracture under normal loading

a new interpretation of mars aerobraking variability planetary wave tide interactions 1 this study presents a new interpretation of mars aerobraking density observations in terms of planetary wave tide interactions mars global surveyor and mars reconnaissance orbiter provide invaluable information about tidal activity in the lower thermosphere of mars through the longitude structure that they reveal in near sun synchronous frame of reference however this same perspective does not permit one to uncover the origins of day to day variability of these structures herein by employing a new arrangement of the data and understanding the relationship between spectral features in longitude space versus ut space we are able to attribute a significant amount of density variability in the aerobraking region to the effect of tidal modulation by planetary waves in the 5 20 day period range

traveling waves in the northern hemisphere of mars 1 analysis of temperature retrievals from mars global surveyor thermal emission spectrometer data has revealed the presence of regular eastward propagating waves in the northern hemisphere a large amplitude zonal wave 1 with a long 20 sol period is particularly prominent during early winter ls 220 270 after ls 270 a weaker and more rapidly propagating 6 5 sol period zonal wave 1 is dominant these waves have a deep vertical structure 40 km correlated with the axis of the winter hemisphere westerly jet simulations with a mars general circulation model suggest that the fast wave is associated with baroclinic instability due to the strong meridional temperature gradient at the surface and is consistent with surface pressure oscillations seen in viking lander data by contrast the slow wave has the appearance of a large amplitude rossby wave that is coupled with an inertially unstable region in the subtropics

direct measurement of contact area and stress dependence of anisotropic flow through rock fracture with heterogeneous aperture distribution abstract direct measurement of a contact area using pressure sensitive film was performed for artificially generated granite tensile fractures with different shear displacements of 2 3 and 5 mm and at various normal stresses of up to approximately 100 mpa to clarify the relationship between anisotropic flow and normal stress in a rock fracture with shear displacement aperture distributions with contact areas were then numerically generated using fracture surface geometry data and anisotropic flow was evaluated through a bi directional flow simulation the directional distributions of contacting asperities in the fracture plane were clearly observed for every given condition and the contacting asperities tended to align in the direction perpendicular to shear displacement generally the contact area increased and the anisotropic distribution was enhanced with increasing normal stress however the contact areas for 3 mm shear displacement were less stress dependent anisotropic flow with higher permeability in the perpendicular direction was always observed for aperture distributions with an anisotropic distribution of the contacting asperities flow paths created in the aperture distributions seemed less tortuous in the perpendicular direction due to the distribution of the contacting asperities the anisotropic flow was enhanced with increasing normal stress to the fracture and was more evident for the smaller shear displacements of 2 mm due to the high sensitivity of the contact area to the normal stress the results suggested that the anisotropic flow was likely for a wide range of normal stresses and correspondingly at varying depths in the earth s crust at which anisotropic flow was enhanced with increasing normal stress based on the stress dependence of the contact area in addition the stress dependent anisotropic flow is expected for much higher normal stresses because complete fracture closure with 100 contact area may be unexpected under the crustal stress conditions at depths of several to ten thousand meters

traveling waves in the martian atmosphere from mgs tes nadir data abstract we have characterized the annual behavior of martian atmospheric traveling waves in the mgs tes data set from the first two martian years of mapping there is a high degree of repeatability between the two years they are dominated by strong low zonal wavenumber waves with high amplitudes near the polar jets strongest in late northern fall and early northern winter the m 1 waves have amplitudes up to about 20 k are vertically extended and occasionally extend even into the tropics periods for m 1 range from 2 5 to 30 sols much weaker waves were identified in the south with amplitudes less than about 3 5 k traveling waves with m 2 and m 3 are also seen but their amplitudes are typically limited to less than 4 k and are generally more confined near the surface in the north they are more evident in fall and spring rather than winter solstice which is clearly dominated by m 1 waves some evidence of storm tracks has been identified in the data with accentuated weather related temperature perturbations near longitudes 200 to 320 e for both the southern and northern hemispheres near latitude 65 at the surface some evidence was also found for a sharpening of longitudinal gradients into what may be frontal systems ep flux divergences show the waves extracting energy from the zonal mean winds when the m 1 waves were strongest decelerations of the zonal jet of order 30 m s sol were measured above 1 scale height the waves extract energy from the jet predominately through barotropic processes but their character is overall mixed barotropic baroclinic inertial instabilities may exist at altitude on the equatorward flanks of the polar jets and marginal stability extends through to the tropics this may explain the coordination of the tropical behavior of the waves with that centered along the polar jet consistent with the ideas expressed in wilson et al 2002 geophys res lett 29 1684 and similar to those in barnes et al 1993 j geophys res 98 3125 3148 throughout the year there exist large regions with the meridional gradient of pv less than zero but they are strongest near winter solstice poleward of the winter jet the regions of instability reach the surface equatorward they do not these regions satisfying a necessary criterion for instability likely explain the genesis of the waves and perhaps also their bimodal character between surface faster waves and altitude slow m 1 waves

new findings for the equilibrated enstatite chondrite grein 002 we report new petrographic and chemical data for the equilibrated el chondrite grein 002 including the occurrence of osbornite metallic copper abundant taenite and abundant diopside as inferred from low si concentrations in kamacite the presence of ferroan alabandite textural deformation chemical equilibration of mafic silicates and a subsolar noble gas component we concur with grein 002s previous classification as an el4 5 chondrite furthermore the existence of pockets consisting of relatively coarse euhedral enstatite crystals protruding large patches of fe ni alloys suggests to us that this el4 5 chondrite has been locally melted we suspect impact induced shock to have triggered the formation of the melt pockets mineralogical evidence indicates that the localized melting of metal and adjacent enstatite must have happened relatively late in the meteorites history the deformation of chondrules equilibration of mafic silicates and generation of normal zoning in fe zn sulfides took place during thermal alteration before the melting event following parent body metamorphism daubreelite was exsolved from troilite in response to a period of slow cooling at subsolidus temperatures exsolution of schreibersite from the coarse metal patches probably occurred during a similar period of slow cooling subsequent to the event that induced the formation of the melt pockets overall shock features other than localized melting correspond to stage s2 and were likely established by the final impact that excavated the grein 002 meteoroid

buseckite fe zn mn s a new mineral from the zaklodzie meteorite buseckite ima 2011 070 fe zn mn s is the fe dominant analog of wurtzite a new member of the wurtzite group discovered in zaklodzie and an ungrouped enstatite rich achondrite the type material occurs as single crystal grains 4 20 m in size in contact with two or more of enstatite plagioclase troilite tridymite quartz and sinoite low ni iron martensitic iron schreibersite keilite cristobalite and graphite which are also present in the type sample are not observed to be in contact with buseckite buseckite is black under diffuse illumination and nearly opaque grayish brown in transmitted light the mean chemical composition of buseckite as determined by electron microprobe analysis of the type material is wt s 35 84 fe 28 68 zn 23 54 mn 10 04 mg 1 18 sum 99 28 leading to an empirical formula calculated on the basis of 2 atoms of fe 0 46 zn 0 32 mn 0 16 mg 0 04 0 99 s 1 01 electron backscatter diffraction patterns of buseckite are a good match to that of synthetic zn 0 558 fe 0 442 s with the p6 3mc structure showing a 3 8357 c 6 3002 a v 80 27 a3 and z 2 buseckite is likely derived from the breakdown of high temperature pyrrhotite to form troilite and buseckite following the solidification of sulfide rich liquids produced during impact melting of an enstatite rich rock