thermal history of the h chondrite parent body implications for metamorphic grade and accretionary time scales abstract multiple temperature age constraints for eight h chondrite samples have been used to provide insight into the thermal history of their parent body through combination with numerical models of thermal evolution assuming internal heating by 26al and conductive cooling the effect of spreading accretion out over time is the principal focus of this work a wide range of body size and date of accretion is systematically tested for different values of accretion rate in order to quantify and illustrate the parameter space that is consistent with the available thermo chronological data we conclude that the h chondrite samples considered have a thermal history consistent with a parent body that at some stage had a concentric onion shell internal structure that body had a radius no larger than 130 km and accretion most probably took place over a time interval on the order of 0 0 0 2 myr approximately 2 myr after cai condensation in any case the time interval of accretion is unlikely to have been more than 0 5 myr supporting evidence in favour of rapid accretion possibly through reassembly of the fragments of an earlier generation of bodies furthermore the h chondrites studied here are inferred to have come from a wide depth range within the body where they experienced metamorphism indicating that preservation of the onion shell structure is unlikely the presence of an insulating regolith does not modify this conclusion as appropriate thermal histories for the three h6 samples considered cannot be reproduced at depths near the surface asteroid 6 hebe may be the parent body of the h chondrites but the high bulk density of the latter is difficult to reconcile with a rubble pile structure of pure h chondrite material finally optimized thermal histories are used to constrain the temperatures characterizing boundaries between petrological types 800 1000 and 1140 k for the h3 4 h4 5 and h5 6 boundaries respectively in detail the type 6 samples studied here are inferred to have experienced a similar peak temperature on the order of 1180 k but spent different times at that temperature while samples of lower metamorphic grade experienced different peak temperature but spent more or less the same time within 10 k of peak temperature on the order of 1 ma these results constitute a quantitative framework within which variations in petrographic and textural properties may be interpreted

contact metamorphism and anatexis of torridonian arkose by minor intrusions of the rum igneous complex inner hebrides scotland

oxygen isotope studies of achondrites abstract oxygen isotope abundances provide a powerful tool for recognizing genetic relationships among meteorites among the differentiated achondrites three isotopic groups are recognized l snc mars 2 earth and moon and 3 hed howardites eucrites diogenites the hed group also contains the mesosiderites main group pallasites and silicates from iiiab irons the angrites may be marginally resolvable from the hed group within each of these groups internal geologic processes give rise to isotopic variations along a slope 1 2 fractionation line as is well known for terrestrial materials variations of 17o from one planet to another are inherited from the inhomogeneities in the solar nebula as illustrated by the isotopic compositions of chondrites and their constituents among the undifferentiated achondrites five isotopic groups are found 1 aubrites 2 winonaites and iab iiicd irons 3 brachinites 4 acapulcoites and lodranites and 5 ureilites the isotopic compositions of aubrites coincide with the earth and moon and also with the enstatite chondrites these bodies apparently were derived from a common reservoir the isotopic composition of which was established at the chondrule scale by nebular processes isotopic similarities between chondrites and achondrites are seen only for the following instances 1 enstatite chondrites and aubrites 2 h chondrites and he irons and 3 l or ll chondrites and iva irons the isotopic data also support the following genetic associations 1 winonaites and iab iiicd irons 2 acapulcoites and lodranites and 3 ureilites and dark inclusions of c3 chondrites an attempt to reconcile the whole planet isotopic compositions of earth mars and the eucrite parent body with mixing models of their chemical compositions failed it is not possible to satisfy both the chemical and isotopic compositions of the terrestrial planets using known primitive solar system components

a model for planetesimal meltdown by 26al and its implications for meteorite parent bodies the melting of planetesimals heated by 26 al has been modelled using a new finite difference method that incorporates convection as an example we consider a planetesimal with a radius of 64 km which accretes instantaneously at t 0 75 myr after the formation of calcium aluminum rich inclusions from cold 250 k nebular dust with 50 porosity at t 0 9 myr t 700 k the planetesimal shrinks to a radius of 50 km due to sintering at t 1 2 myr t 1425 k the fully insulated interior deeper than a few kilometers starts to melt and at t 1 5 myr t 1725 k with 50 melting convection starts by t 2 myr the planetesimal is a globe of molten convecting slurry inside a thin residual crust from about t 2 5 myr the crust thickens rapidly as the power of 26 al fades planetesimals probably melt in this manner when they accrete before t 1 3 myr and are large enough to insulate themselves r 20 km for accretion at t 0 rising to 80 km at t 1 3 myr melting behavior will also be affected by the level of 60 fe in nebular dust by the extent of devolatilization reactions and basalt segregation during heating and by gradual accretion the model suggests that a the parent bodies of differentiated meteorites had accreted before about t 1 5 to 2 myr and before most chondritic parent bodies had formed and b that molten planetesimals may be a source for chondrule melt droplets

metal veins in the kernouve h6 s1 chondrite evidence for pre or syn metamorphic shear deformation abstract kernouve is an h6 chondrite that experienced a very small degree of late stage shock loading s1 however kernouve contains fe ni metal vein like structures whose formation have been attributed to an early impact event to establish the formation conditions of metal veins in kernouve we examined the three dimensional 3d arrangement of metal vein like structures and typical metal grains in two samples of kernouve with x ray microtomography ct at resolutions of 11 m voxel we additionally investigated the 3d structure of the porosity present in kernouve using ct at two different resolutions 3 and 11 m voxel these data and optical microscopy support the hypothesis that kernouve has experienced little post metamorphic shock however the moderate 5 8 vol porosity of kernouve is in the form of intergranular voids rather than cracks which indicates any cracking that may have existed in the relatively brittle silicate grains was annealed we estimate that 70 80 of the primordial porosity in kernouve was removed by impact related compaction moreover we found no collective orientation of metal grains so high metamorphic temperatures following compaction erased any common orientation of metal grains due to compaction we propose that the metal vein structures can be explained as a pre or syn metamorphic shock induced process which we infer was primarily shear deformation with some uniaxial compaction also occurring the coarse metal veins probably formed by accumulation of ductile metal grains along shear zones a process that would have been facilitated by having an already warm h chondrite parent body when shock occurred i e syn metamorphic shock the complexity of shape including numerous tendrils expanding from the primary structure of the veins in kernouve is likely due to the coalescence of metal by metamorphic growth after the shear event the metal veins in kernouve thus appear to record evidence for early shock induced metal mobilization and the maximum shock pressure experienced by kernouve may have been 21 gpa our study suggests that collision induced segregation of metal occurred at an early stage in low gravity planetesimals consistent with the idea that this process could have been important for the differentiation of such objects

thermal evolution model for the h chondrite asteroid instantaneous formation versus protracted accretion abstract we present a model of the thermal evolution of asteroids assuming an onion shell model for the h chondrite parent body we obtain constraints for the h chondrite asteroid parameters by fitting empirical h chondrite cooling ages of estacado guarena kernouve mt browne richardton allegan nadiabondi ste marguerite and forest vale by using a genetic algorithm for parameter optimisation the model improves previous calculations on the thermal history calculated in the instantaneous accretion approximation considering sintering and porosity dependent heat conduction the model is extended to include a finite growth time of the parent body to study whether the meteoritic record constrains the duration of the growth phase of the parent body where it assembles most of its mass it is found that only short accretion times of up to 0 1 ma are compatible with the empirical data on h chondrite cooling histories best fit models yield excellent agreement with the cooling age data particularly they indicate that i 26 al was the major heat source driving metamorphism while 60 fe contributed rather marginally ii maximum temperatures remained below partial melting temperatures throughout the body indicating that no partial differentiation occurred on the h chondrite parent asteroid iii the h chondrite asteroid formed 2 ma after cais briefly after most ordinary chondrite chondrules formed if 26 al abundance defines a chronological sequence

thermal constraints on the early history of the h chondrite parent body reconsidered abstract reconstructions of the early thermal history of the h chondrite parent body have focused on two competing hypotheses the first posits an undisturbed thermal evolution in which the degree of metamorphism increases with depth yielding an onion shell structure the second posits an early fragmentation reassembly event that interrupted this orderly cooling process here we test these hypotheses by collecting a large number of previously published closure age and cooling rate data and comparing them to a suite of numerical models of thermal evolution in an idealized parent body we find that the onion shell hypothesis when applied to a parent body of radius 75 130 km with a thermally insulating regolith is able to explain 20 of the 21 closure age data and 62 of the 71 cooling rates furthermore six of the eight meteorites for which multiple data at different temperatures are available can be accounted for by onion shell thermal histories we therefore conclude that no catastrophic disruption of the h chondrite parent body occurred during its early thermal history the relatively small number of data not explained by the onion shell hypothesis may indicate the formation of impact craters on the parent body which while large enough to excavate all petrologic types were small enough to leave the parent body largely intact impact events fulfilling these requirements would likely have produced transient crater diameters at least 30 of the parent body diameter

high resolution x ray computed tomography and its application to ore deposits from data acquisition to quantitative three dimensional measurements with case studies from ni cu pge deposits high resolution x ray computed tomography hrxct is a nondestructive technique that allows exploration of the three dimensional distribution of minerals and pore space in natural and synthetic rock samples recent technological developments allow the characterization of samples up to few centimeters in diameter at a resolution down to 0 7 m this combined with the development of dedicated workflows algorithms and softwares is opening new doors for the quantitative three dimensional characterization of ores at the sample scale when combined with three dimensional image analysis hrxct provides quantitative three dimensional mineralogical and textural measurements volume shape three dimensional relationship that are impossible to assess accurately by any other method this manuscript describes the principles of hrxct and presents dedicated methodologies from data acquisition throught to quantitative three dimensional measurements these methodologies are applied to ni cu pge ore samples but are suitable for a range of geologic materials the combination of hrxct with quantitative three dimensional image analysis applied to geologic materials hosting ore deposits provides a better understanding of ore mineralogy ore forming processes and parameters required for mineral or metallurgical processing with benefit for both academic studies and mineral industry applications

experimental partial melting of the st severin ll and lost city h chondrites we have performed melting experiments between 1170 1325 c and at an oxygen fugacity of iw 1 on the ordinary chondrites lost city h and st severin ll in order to investigate the origin of diogenites and their possible relationship to eucrites low ca pyroxene disappears from the lost city residuum just above 1220 c at a mg near 66 accordingly lost city does not have a sufficiently large stability field for orthopyroxene to be a likely parent composition for melts which could crystallize diogenites in contrast orthopyroxene in st severin persists up to about 1325 c at which point it has a mg similar to that of typical diogenites 75 this is only marginally compatible with diogenite origins as the most magnesian pyroxenes from diogenites mg 82 and howardites mg 85 are more mgo rich than any pyroxene formed from a st severin melt accordingly if diogenites formed from a source having the bulk composition of an ordinary chondrite than either the fo2 had to be lower than that inferred for eucrite formation or more likely the parent body had a lower fesi ratio than that of an ll chondrite also low temperature melts of st severin are depleted in elements compatible with pyroxene and so while broadly eucritic do not closely match the compositions of eucrites that are thought to be primary partial melts hence it doesn t appear possible to produce both diogenites and eucrites from the same source region composition if eucrites are primary partial melts reconnaiss mce experiments at higher oxygen fugacity iw 2 produce broadly angritic melts for lost city as was observed for murchison and allende in contrast our na2o poor st severin charge produced a broadly eucritic melt at this higher fo2 this difference in melting behavior is probably because ll chondrites have a much lower bulk fesi ratio than the h cm or cv chondrites

mid infrared mapping of jupiter s temperatures aerosol opacity and chemical distributions with irtf texes abstract global maps of jupiter s atmospheric temperatures gaseous composition and aerosol opacity are derived from a programme of 5 20 m mid infrared spectroscopic observations using the texas echelon cross echelle spectrograph texes on nasa s infrared telescope facility irtf image cubes from december 2014 in eight spectral channels with spectral resolutions of r 2000 12 000 and spatial resolutions of 2 4 latitude are inverted to generate 3d maps of tropospheric and stratospheric temperatures 2d maps of upper tropospheric aerosols phosphine and ammonia and 2d maps of stratospheric ethane and acetylene the results are compared to a re analysis of cassini composite infrared spectrometer cirs observations acquired during cassini s closest approach to jupiter in december 2000 demonstrating that this new archive of ground based mapping spectroscopy can match and surpass the quality of previous investigations and will permit future studies of jupiter s evolving atmosphere the visibility of cool zones and warm belts varies from channel to channel suggesting complex vertical variations from the radiatively controlled upper troposphere to the convective mid troposphere we identify mid infrared signatures of jupiter s 5 m hotspots via simultaneous m n and q band observations which are interpreted as temperature and ammonia variations in the northern equatorial zone and on the edge of the north equatorial belt neb equatorial plumes enriched in nh3 gas are located south east of nh3 desiccated hotspots on the edge of the neb comparison of the hotspot locations in several channels across the 5 20 m range indicate that these anomalous regions tilt westward with altitude aerosols and ph3 are both enriched at the equator but are not co located with the nh3 plumes the equatorial temperature minimum and ph3 aerosol maxima have varied in amplitude over time possibly as a result of periodic equatorial brightenings and the fresh updrafts of disequilibrium material temperate mid latitudes display a correlation between mid ir aerosol opacity and the white albedo features in visible light i e zones we find hemispheric asymmetries in the distribution of tropospheric ph3 stratospheric hydrocarbons and the 2d wind field estimated via the thermal wind equation that suggest a differing efficiency of mechanical forcing e g vertical mixing and wave propagation between the two hemispheres that we argue is driven by dynamics rather than jupiter s small seasonal cycle jupiter s stratosphere is notably warmer at northern mid latitudes than in the south in both 2000 and 2014 although the latter can be largely attributed to strong thermal wave activity near 30 n that dominates the 2014 stratospheric maps and may be responsible for elevated c2h2 in the northern hemisphere a vertically variable pattern of temperature and windshear minima and maxima associated with jupiter s quasi quadrennial oscillation qqo is observed at the equator in both datasets although the contrasts were more subdued in 2014 large scale equator to pole gradients in ethane and acetylene are superimposed on top of the mid latitude mechanically driven maxima with c2h2 decreasing from equator to pole and c2h6 showing a polar enhancement consistent with a radiatively controlled circulation from low to high latitudes cold polar vortices beyond 60 latitude can be identified in the upper tropospheric and lower stratospheric temperature maps suggesting enhanced radiative cooling from polar aerosols finally compositional mapping of the great red spot confirms the local enhancements in ph3 and aerosols the north south asymmetry in nh3 gas and the presence of a warm southern periphery that have been noted by previous authors

petrologic evidence for collisional heating of chondritic asteroids abstract the identification of the mechanism s responsible for heating asteroids is among the major problems in planetary science because of difficulties with models of electromagnetic induction and the decay of short lived radionuclides it is worthwhile to evaluate the evidence for collisional heating localized impact heating is responsible for forming shock veins melt pockets metal sulfide mixtures vugs agglutinates and a wide variety of melt rock clasts new evidence for localized impact heating comes from the high proportion of relict type 6 material among impact melt bearing ordinary chondrites oc this relict material was probably metamorphosed by residual heat within large craters olivine aggregates composed of faceted crystals with 120 triple junctions occur within the melted regions of the chico and rose city oc melt rocks the olivine aggregates formed from shocked mosaicized olivine grains that underwent contact metamorphism large scale collisional heating is supported by the correlation in oc between petrologic type and shock stage no other heating mechanism can readily account for this correlation the occurrence of impact melt rock clasts in oc that have been metamorphosed along with their whole rocks indicates that some impact events preceded or accompanied thermal metamorphism such impact events occurring during or shortly after accretion are probably responsible for substantially melting 0 5 of oc these events most have heated a larger percentage of oc to subsolidus temperatures sufficient to have caused significant metamorphism if collisional heating is viable then oc parent asteroids must have been large large oc asteroids in the main belt may include those of the s iv spectral subtype collisional heating is inconsistent with layered onion shell structures in oc asteroids wherein the degree of metamorphism increases with depth but the evidence for such structures is weak it seems likely that collisional heating played an important role in metamorphosing chondritic asteroids

fresh evidence relating the great adriatic surge of 21 june 1978 to mesoscale atmospheric forcing 1 on the morning of 21 june 1978 exceptional sea level oscillations with a trough to crest height of 6 m and a period of 10 20 min were observed in vela luka bay slightly less pronounced variability was observed in a wider middle and south adriatic east coastal area and with some delay along the west coast in this paper one of the original hypotheses put forward to interpret the event relating it to a mesoscale air pressure disturbance is reconsidered by using all the available data as well as state of the art meteorological and oceanographic models a fresh look at the meteorological data confirms that the atmospheric disturbance propagated at about 22 m s in a northeastward direction additionally the data suggest that it had the shape of the boxcar function characterized by an air pressure offset of 3 mbar and duration of 10 min the meteorological model employed weather research and forecasting wrf advanced research wrf proves unable to reproduce the mesoscale disturbance coinciding with the surge but it shows that the background atmospheric conditions were favorable for the development of such disturbances the oceanographic model advanced circulation model for shelves coasts and estuaries two dimensional depth integrated forced by the described air pressure disturbance successfully reproduces sea level variability in vela luka bay reaching a few meters and thus surpassing the inverted barometer response by two orders of magnitude the enhancement appears to be due to a four phase process the model also suggests that the scattering due to the variable bathymetry and the reflection from the east adriatic coast resulted in waves that returned towards the west coast and generated considerable sea level activity there

shock metamorphism of ordinary chondrites a revised petrographic classification of progressive stages of shock metamorphism of ordinary chondrites is proposed six stages of shock s1 to s6 are defined based on shock effects in olivine and plagioclase as recognized by thin section microscopy the characteristic shock effects of each shock stage are s1 unshocked sharp optical extinction of olivine s2 very weakly shocked undulatory extinction of olivine s3 weakly shocked planar fractures in olivine s4 moderately shocked mosaicism in olivine s5 strongly shocked isotropization of plagioclase maskelynite and planar deformation features in olivine and s6 very strongly shocked recrystallization of olivine sometimes combined with phase transformations ringwoodite and or phases produced by dissociation reactions s6 effects are always restricted to regions adjacent to melted portions of a sample which is otherwise only strongly shocked in stages s3 to s6 localized melting results from stress and temperature peaks which locally deviate from the equilibration shock pressure due to differences in shock impedance these melting effects are a opaque melt veins shock veins b melt pockets with interconnecting melt veins c melt dikes and d troilite metal deposits in fractures based on a critical evaluation of data from shock recovery experiments a shock pressure calibration for the six shock stages is proposed which defines the s1 s2 s2 s3 s3 s4 s4 s5 and s5 s6 transitions at 5 5 10 15 20 30 35 and 45 55 gpa respectively whole rock melting and formation of impact melt rocks or melt breccias occurs at about 75 90 gpa the symbol for the shock stage may be used in combination with the symbol for the petrologic type to abbreviate the complete classification of a chondrite e g h5 s3 we propose this new shock classification and pressure calibration system to replace previous systems which are out of date with respect to the pressure calibration nominally restricted to l chondrites and based on incomplete and in part illdefined sets of shock effects we have classified seventy six ordinary chondrites using the new classification system and conclude the following 1 1 shock effects and the sequence of progressively increasing degrees of shock metamorphism are very similar in h l and ll groups differences in the frequency distribution of shock stages are relatively minor e g l chondrites appear to have the largest fraction with stages s5 and s6 this suggests that the collisional histories of the h l and ll parent bodies were similar 2 2 petrologic type 3 chondrites are deficient in stages s4 to s6 and with increasing petrologic type the frequency of stages s4 to s6 increases we suggest that the more porous and volatile rich type 3 chondrites are subject to melting at a lower shock pressure than the nonporous chondrites of higher petrologic type volatiles trapped in pores cause shock induced dispersal of the shocked and melted material into small particles which are not expected to survive as meteorites 3 3 stage s3 is the most abundant in nearly all petrologic types 4 4 at shock pressures in excess of about 35 gpa s5 and s6 4he and 40ar are almost completely lost pressures below 10 gpa s1 and s2 do not cause noble gas losses

shock experiments with the h6 chondrite kernouve pressure calibration of microscopic shock effects shock recovery experiments were carried out on samples of the h6 chondrite kernouve at shock pressures of 10 15 20 25 30 35 45 and 60 gpa and preheating temperatures of 293 k low temperature experiments and 920 k high temperature experiments using a calculated equation of state of kernouve pressure pulse durations of 0 3 to 1 2 s were estimated the shocked samples were investigated by optical microscopy to calibrate the various shock effects in olivine orthopyroxene oligoclase and troilite the following pressure calibration is proposed for silicates 1 undulatory extinction of olivine gpa 2 weak mosaicism of olivine from 10 15 gpa to 20 25 gpa 3 onset of strong mosaicism of olivine at 20 25 gpa 4 transformation of oligoclase to diaplectic glass completed at 25 30 gpa low temperature experiments and at 20 25 gpa high temperature experiments 5 onset of weak mosaicism in orthopyroxene at 30 35 gpa low temperature experiments and at 25 30 gpa high temperature experiments and 6 recrystallization or melting of olivine starting at 45 60 gpa low temperature experiments and at 35 45 gpa high temperature experiments and completed above 45 60 gpa in the high temperature experiments troilite displays distinct differences between the samples shocked at low and high temperatures in the low temperature experiments the following effects can be observed in troilite 1 undulatory extinction up to 25 gpa 2 twinning up to 45 gpa 3 partial recrystallization from 30 to 60 gpa and 4 complete recrystallization 35 gpa whereas in the high temperature experiments troilite shows 1 complete recrystallization from 10 up to 45 gpa and 2 melting and crystallization above 45 gpa localized shock induced melting is observed in samples shocked to pressures 15 gpa in the high temperature experiments and 30 gpa for the low temperature experiments in the form of feni metal and troilite melt injections and intergrowths and as pockets and veins of whole rock melt obviously the onset and abundance of shock induced localized melting strongly depends on the initial temperature of the sample

investigation of the h7 ordinary chondrite watson 012 implications for recognition and classification of type 7 meteorites abstract despite the fact that the number of officially classified meteorites is now over 45 000 we lack a clearly defined sequence of samples from a single parent body that records the entire range in metamorphic temperatures from pristine primitive meteorites up to the temperatures required for extensive silicate partial melting here we conduct a detailed analysis of watson 012 an h7 ordinary chondrite to generate some clarity on the textural and chemical changes associated with equilibrium based silicate partial melting in chondritic meteorites to do this we compare the textures in the meteorite with those preserved in metamorphic contact aureoles on earth the most distinctive texture generated by the partial melting that affected watson 012 is an extensively interconnected plagioclase network which is clearly observable with a petrographic microscope enlarged metal troilite grains are encapsulated at widenings in this plagioclase network and this is clearly visible in reflected light together with these features we define a series of other characteristics that can be used to more clearly classify chondritic meteorites as being of petrologic type 7 to provide comprehensive evidence of silicate partial melting and strengthen the case for using simple petrographic observations to classify similar meteorites we use high resolution x ray computed tomography to demonstrate that the plagioclase network has a high degree of interconnectedness and crystallised as large cm scale skeletal crystals within an olivine orthopyroxene clinopyroxene framework essentially pseudomorphing a melt network back scattered electron imaging and element mapping are used to show that some of the clino and orthopyroxene in watson 012 also crystallised from silicate melt and the order of crystallisation was orthopyroxene clinopyroxene plagioclase x ray diffraction data supported by bulk geochemistry are used to show that plagioclase and ortho and clinopyroxene were added to the watson 012 sample by through flowing basaltic melt along with the absence of glass and granophyre this interconnected network of coarse grained skeletal plagioclase indicates that the sample cooled slowly at depth within the parent body the evidence of melt flux indicates that watson 012 formed in the presence of a gravitational gradient and thus at significant distance from the centre of the h chondrite parent body the gravitational gradient at the centre would be zero our interpretation is that incipient silicate partial melting in watson 012 occurred when a region of radiogenically heated h6 material located at considerable depth possibly at 15 20 km from surface was heated by an additional ca 200 300 c in association with a large shock event due to insulation at depth within an already hot parent body the post shock temperature equilibrated and remained above the solidus long enough for widespread equilibrium based silicate partial melting and for melt to migrate although the observed melting may have been facilitated by additional heating from an impact event this is not an example of instantaneous shock melting which produces thermal disequilibrium at short length scales and distinctly different textures a small number of h l and ll chondrites have been previously classified as being of petrologic type 7 with our new criteria to support that classification these represent our best opportunity to explore the transition from high temperature sub solidus metamorphism through the onset of silicate partial melting in three different parent bodies

oxygen isotope studies of ordinary chondrites several stages in the evolution of ordinary chondritic meteorites are recorded in the oxygen isotopic composition of the meteorites and their separable components chondrules fragments clasts and matrix the whole rock isotopic compositions reflect the iron group of the meteorite h l or ll isotopic uniformity of h3 to h6 and l3 to l6 are consistent with closed system metamorphism within each parent body ll3 chondrites differ slightly from ll4 to ll6 implying a small degree of opensystem aqueous alteration and carbon reduction on the scale of individual chondrules the meteorites are isotopically heterogeneous allowing recognition of the solar nebular processes of chondrule formation chondrules for all classes of ordinary chondrites are derived from a common population which was separate from the population of chondrules in carbonaceous or enstatite chondrites chondrules define an isotopic mixing line dominated by exchange between 16o rich and 16o poor reservoirs the oxygen isotopic compositions of chondrites serve as fingerprints for identification of genetic association with other meteorite types achondrites and iron and for recognition of source materials in meteoritic breccias

on the pseudomorphing of melt filled pores during the crystallization of migmatites pseudomorphs of melt filled pores recognized by their generally cuspate shape are used as diagnostic for the former presence of partial melt they are commonly observed in migmatites from the mid to deep crust although they occur in the smaller pores in migmatites from shallower levels 1 2 kbar the pseudomorphing of meltfilled pores is controlled by the kinetics of nucleation and is a consequence of the greater supersaturation required for nucleation in a small pore compared with a larger one we examine three migmatites in detail a contact metamorphosed cherty band from an iron formation an archaean regional granulite from an accretionary prism and an amphibolite facies sample from the roots of an archaean mountain chain the greater undercooling required for nucleation in progressively smaller pores is recorded by the composition of plagioclase pseudomorphs a study of dihedral angles at the corners of pseudomorphed pores demonstrates that melt solid textural equilibrium was probably attained only in the contact aureole the regional granulite preserves an almost unmodified reaction controlled melt distribution with little evidence for either melt solid textural equilibration or solid solid re equilibration whereas the reactioncontrolled melt distribution in the regional amphibolite facies example has been modified by a partial approach to solid solid textural equilibrium it is not clear whether the differences in dihedral angle population are due to differences in uplift and exhumation rates or due to the presence of h2o on grain boundaries

cassini imaging of jupiter s atmosphere satellites and rings the cassini imaging science subsystem acquired about 26 000 images of the jupiter system as the spacecraft encountered the giant planet en route to saturn we report findings on jupiter s zonal winds convective storms low latitude upper troposphere polar stratosphere and northern aurora we also describe previously unseen emissions arising from io and europa in eclipse a giant volcanic plume over io s north pole disk resolved images of the satellite himalia circumstantial evidence for a causal relation between the satellites metis and adrastea and the main jovian ring and information on the nature of the ring particles

postshock annealing and postannealing shock in equilibrated ordinary chondrites implications for the thermal and shock histories of chondritic asteroids abstract in addition to shock effects in olivine plagioclase orthopyroxene and ca pyroxene petrographic shock indicators in equilibrated ordinary chondrites oc include chromite veinlets chromite plagioclase assemblages polycrystalline troilite metallic cu irregularly shaped troilite grains within metallic fe ni rapidly solidified metal sulfide intergrowths martensite and various types of plessite metal sulfide veins large metal and or sulfide nodules silicate melt veins silicate darkening low ca clinopyroxene silicate melt pockets and large regions of silicate melt the presence of some of these indicators in every petrologic type 4 to 6 ordinary chondrite demonstrates that collisional events caused all equilibrated oc to reach shock stages s3 s6 those type 4 to 6 oc that are classified as shock stage s1 on the basis of sharp optical extinction in olivine underwent postshock annealing due to burial beneath materials heated by the impact event those type 4 to 6 oc that are classified s2 on the basis of undulose extinction and lack of planar fractures in olivine were shocked to stage s3 s6 annealed to stage s1 and then shocked again to stage s2 some oc were probably shocked to stage s3 after annealing it seems likely that many oc experienced multiple episodes of shock and annealing because 40ar 39ar chronological data indicate that mil 99301 ll6 s1 was annealed 4 26 ga ago presumably as a consequence of a major impact it seems reasonable to suggest that other equilibrated s1 and s2 oc which contain relict shock features were also annealed by impacts because some type 6 s1 oc e g guarena kernouve portales valley all of which contain relict shock features were annealed 4 44 4 45 ga ago during a period when impacts were prevalent and most oc were thermally metamorphosed it follows that impact induced annealing could have contributed significantly to oc thermal metamorphism

analysis of ordinary chondrites using powder x ray diffraction 1 modal mineral abundances abstract powder x ray diffraction xrd is used to quantify the modal abundances in wt of 18 h 17 l and 13 ll unbrecciated ordinary chondrite falls which represents the complete petrologic range of equilibrated ordinary chondrites types 4 6 the xrd technique presents an effective alternative to traditional methods for determining modal abundances such as optical point counting and electron microprobe phase emp mapping the majority of chondrite powders in this study were previously prepared for chemical characterization from 8 to 20 g of material which is consistent with the suggested mass 10 g necessary to provide representative sampling of ordinary chondrites olivine and low ca pyroxene are the most abundant phases present comprising one half to three fourths of total abundances while plagioclase high ca pyroxene troilite and metal comprise the remaining xrd measured mineralogy pigeonite may also be present in some samples but it is fitted using a high ca pyroxene standard so exact abundances cannot be measured directly using xrd comparison of xrd measured abundances with calculated cross iddings pirsson washington cipw normative abundances indicates that systematic discrepancies exist between these two data sets particularly in olivine and high ca pyroxene this discrepancy is attributed to the absence of pigeonite as a possible phase in the cipw normative mineralogy oxides associated with pigeonite are improperly allocated resulting in overestimated normative olivine abundances and underestimated normative high ca pyroxene abundances this suggests that the cipw norm is poorly suited for determining mineralogical modal abundances of ordinary chondrites

galileo photopolarimeter radiometer observations of jupiter and the galilean satellites photopolarimeter radiometer ppr maps of daytime temperatures on ganymede at a resolution of 220 kilometers show the expected anticorrelation with albedo but morning temperatures were about 10 kelvin warmer than expected europa had a subsolar temperature of 128 kelvin and a lower effective thermal inertia than either ganymede or callisto and io9s night side was cooler than predicted by recent models perhaps requiring revision of heat flow estimates the lowest 250 millibar temperatures in the great red spot grs generally corresponded to the visually darkest regions temperatures remained cold north of the grs but they rose by as much as 6 kelvin to the south over the 2800 kilometer ppr resolution a visually bright region northwest of the grs was also relatively cold it is likely that nh3 clouds affected the determination of the 500 millibar temperature field which appears qualitatively different

impact of geomorphological changes to harbor resonance during meteotsunamis the vela luka bay test case in engineering studies harbor resonance including quality and amplification factors is typically computed for swell and waves with periods shorter than 10 min however in various locations around the world such as vela luka bay in croatia meteotsunami waves of periods greater than 10 min can excite the bay or harbor natural modes and produce substantial structural damages in this theoretical study the impact of some geomorphological changes of vela luka bay i e deepening of the bay dredging the harbor adding a pier or a marina to the amplification of the meteotsunami waves are presented for a set of 6401 idealized pressure wave field forcing used to derive robust statistics the most substantial increase in maximum elevation is found when the vela luka harbor is dredged to a 5 m depth which is in contradiction with the calculation of the quality factor showing a decrease of the harbor natural resonance it has been shown that the forcing energy content at different frequency bands should also be taken into account when estimating the quality and amplification factors as their typical definitions derived from the peak frequency of the sea level spectrum fail to represent the harbor response during meteotsunami events new definitions of these factors are proposed in this study and are shown to be in good agreement with the results of the statistical analysis of the vela luka bay maximum elevation results in addition the presented methodology can easily be applicable to any other location in the world where meteotsunamis occur

jupiter s atmospheric temperatures from voyager iris to cassini cirs abstract retrievals performed on cassini composite infrared spectrometer data obtained during the distant jupiter flyby in 2000 2001 have been used to generate global temperature maps of the planet in the troposphere and stratosphere but to higher latitudes than were shown previously by flasar et al flasar f m 39 colleagues 2004a nature 427 132 135 flasar f m 44 colleagues 2004b space sci rev 115 169 297 similar retrievals were performed on voyager 1 iris data to provide the first detailed iris map of the stratosphere and high latitudes in the troposphere thermal winds were calculated for each data set and show strong vertical shears in the zonal winds at low latitudes and meridional temperature gradients indicate the presence of circumpolar jets as well the temperatures retrieved from the two spacecraft were also compared with yearly ground based data obtained over the intervening two decades tropospheric temperatures reveal gradual changes at low latitudes with little obvious seasonal or short term variation orton et al 1994 science 265 625 631 stratospheric temperatures show much more complicated behavior over short timescales consistent with quasi quadrennial oscillations at low latitudes as suggested in prior analyses of shorter intervals of ground based data orton et al 1991 science 252 537 542 friedson a j 1999 icarus 137 34 55 a scaling analysis indicates that meridional motions mechanically forced by wave or eddy convergence play an important role in modulating the temperatures and winds in the upper troposphere and stratosphere on seasonal and shorter timescales at latitudes away from the equator the mechanical forcing can be derived simply from a temporal record of temperature and its vertical derivative ground based observations with improved vertical resolution and or long term monitoring from spacecraft are required for this purpose though the voyager and cassini data given indications that the magnitude of the forcing is very small

wave activity in jupiter s north equatorial belt from near infrared reflectivity observations high spatial resolution images of jupiter at 1 58 2 28 m are used to track and characterize a wave pattern observed in 2017 at a planetocentric latitude of 14 n the wave pattern has a wave number of 18 and spans 5 in latitude one bright crest remains stationary in system iii longitude while the remaining crests move slowly westward the bright and dark regions of the near infrared wave pattern are caused by variations in the vertical location of the upper tropospheric haze layer a comparison with thermal infrared observations shows a correlation with temperature anomalies in the upper troposphere the results are consistent with a rossby wave generated by flow around a stationary vortex

hydraulic and acoustic properties as a function of porosity in fontainebleau sandstone laboratory measurements have been made of the permeability k free porosity l compressional velocities vp or ve and compressional attenuations qp or qe in fontainebleau sandstone over a continuous range of porosities from 3 to 28 this large variation was achieved without any composition change fontainebleau sandstone is made of fine quartz grains with regular grain size 250 m permeability was measured with a falling head permeameter velocities and attenuations were obtained either through an ultrasonic experiment for frequencies around 500 khz or through a resonant bar technique experiment for frequencies around 5 khz and in both cases with varying water saturation the results show an excellent correlation between permeability k and total porosity for all our samples for low porosities 3 to 9 permeability in millidarcies is 2 75 10 5 7 33 while for high porosities 9 to 28 permeability k in millidarcies is given by 0 303 3 05 the correlation is also excellent between free porosity and total porosity on the other hand the correlation between acoustic properties and total porosity is not as clear as for hydraulic properties whatever the frequency 500 khz or 5 khz or the water saturation on the average velocity decreases and attenuation roughly increases with increasing total porosity velocity and attenuation values are related to the variation of grain contact structure and two samples with the same porosity and permeability may exhibit different velocities and attenuations the clear correlation between hydraulic properties and porosity is related to constant grain size while the lack of correlation for acoustic properties emphasizes the importance of the microstructure

portales valley petrology of a metallic melt meteorite breccia portales valley pv is an unusual metal veined meteorite that has been classified as an h6 chondrite it has been regarded either as an annealed impact melt breccia as a primitive achondrite or as a meteorite with affinities to silicated iron meteorites we studied the petrology of pv using a variety of geochemical mineralogical techniques our results suggest that pv is the first well documented metallic melt meteorite breccia mineral chemical and other data suggest that the protolith to pv was an h chondrite the composition of feni metal in pv is somewhat fractionated compared to h chondrites and varies between coarse vein and silicate rich portions it is best modeled as having formed by partial melting at temperatures of 940 1150 c with incomplete separation of solid from liquid metal solid metal concentrated in the coarse vein areas and s bearing liquid metal concentrated in the silicate rich areas possibly as a result of a surface energy effect both carbon and phosphorus must have been scavenged from large volumes and concentrated in metallic liquid graphite nodules formed by crystallization from this liquid whereas phosphate formed by reaction between p bearing metal and clinopyroxene components depleting clinopyroxene throughout much of the meteorite and growing coarse phosphate at metal silicate interfaces some phosphate probably crystallized from p bearing liquids but most probably formed by solid state reaction at 975 725 c phosphate forming and feo reduction reactions were widespread in pv and entailed a change in the mineralogy of the stony portion on a large scale portales valley experienced protracted annealing from supersolidus to subsolidus temperatures probably by cooling at depth within its parent body but the main differences between pv and h chondrites arose because maximum temperatures were higher in pv a combination of a relatively weak shock event and elevated pre shock temperatures probably produced the vein and breccia texture with endogenic heating being the main heat source for melting and with stress waves from an impact event being an essential trigger for mobilizing metal portales valley is best classified as an h7 metallic melt breccia of shock stage s1 the meteorite is transitional between more primitive chondritic and evolved achondrite iron meteorite types and offers clues as to how differentiation could have occurred in some asteroidal bodies

partial melting and melt migration in the acapulcoite lodranite parent body we review petrologic evidence that the acapulcoites and lodranites formed by 1 vol to probably 20 vol whole rock partial melting of a chondritic precursor material at low degrees of partial melting only fe ni fes cotectic melting occurred migration distances for partial melts were short resulting in the formation of acapulcoites with essentially chondritic troilite and plagioclase contents but achondritic textures at high degrees of partial melting both fe ni fes and basaltic plagioclase pyroxene partial melts formed and the melts may have migrated out of the source rock the partial melt residues which are more or less depleted in fe ni fes and plagioclase are the lodranites melt migration was complex most acapulcoites which experienced relatively low degrees of partial melting lost little if any of the partial melt one acapulcoite lew 86220 represents a unique case in which fe ni fes and basaltic partial melts appear to have migrated from a lodranite source region into a cooler acapulcoite region where they were trapped in cases of the relatively high degrees of partial melting experienced by lodranites melts may have been partly selectively or totally removed from the rocks and fe ni fes and or basaltic partial melts may have been removed to different degrees and may in fact have been trapped on occasion in greater than chondritic proportions we model vein and dike formation and melt migration by calculating the excess pressures and vein and dike sizes for varying degrees of partial melting our calculations are broadly consistent with observations indicating that melt migration is inefficient at low degrees of partial melting and extremely efficient at high degrees of partial melting although the size of the acapulcoite lodranite parent body and the volatile contents of the chondritic precursor rocks are poorly constrained the lack of basaltic rocks in the world s meteorite collections complementary to the lodranites suggests that basaltic partial melts may have been accelerated off the body by explosive volcanism of the type envisioned by wilson and keil 1991 and ejected into space the diversity of rocks from the acapulcoite lodranite parent body may provide a basis for better understanding the diverse range of spectral subtypes recognized among the s type asteroids

a disturbance in jupiter s high speed north temperate jet during 1990 abstract during february 1990 a remarkable disturbance developed in the strongest jovian atmospheric jet located at 24 n planetographic latitude our telescopic images at visible wavelenghts revealed the outbreak of two bright features with an initial length scale 6000km the first discovered on february 10 and the second a week later both resided on the peak of the eastward jet drifting rapidly with zonal velocities of 165 and 170 m sec 1 respectively to the west of these bright features a pattern of alternating dark and light spots developed over the next few days these features moved with a lower mean velocity of 108 m sec 1 and had a mean east west length of 10 000 km their separation in longitude showed a bimodal distribution with peaks at 12 600 and 19 700 km the disturbance expanded zonally encircling the whole latitudinal band at 24 n 3 months after its outburst generating a new temperate belt we suggest that the two bright spots were the result of a localized convective instability while the dark spots may reflect a wave disturbance that was generated by the onset of convection

magma crystallization and viscosity a study of molten basalts from the piton de la fournaise volcano la reunion island abstract the viscosity of three molten basalts produced by fusion of lavas issued from different eruptions of the piton de la fournaise la reunion island has been investigated above the liquidus and at high degrees of supercooling for all basalts crystallization took place rapidly above the glass transition range which made static measurements problematic because of time dependent non newtonian rheology by contrast reproducible results were obtained in dynamic measurements made at a constant heating rate of 5 k mn partial crystallization resulted in strong viscosity increases which were primarily due to the presence of solid inclusions comparisons with phase equilibria experiments performed for the same samples at higher temperatures show that crystallization takes place differently below the liquidus and at strong degrees of supercooling as recently described for simpler systems these differences in nucleation and growth are controlled by the relative mobilities of the cations diffusing within the melt to attach themselves to crystal melt interfaces a consequence is that the composition evolution of the residual melt differs in equilibrium and irreversible crystallization in turn this contrast induces opposite viscosity variations for the residual melt

shock and thermal history of northwest africa 4859 an annealed impact melt breccia of ll chondrite parentage containing unusual igneous features and pentlandite abstract northwest africa 4859 nwa 4859 is a meteorite of ll chondrite parentage that shows unusual igneous features and contains widely distributed pentlandite the most obvious unusual feature is a high proportion of large 3 cm diameter igneous textured enclaves lites interpreted as shock melts that were intruded into an ll chondrite host one such lite appears to have been produced by whole rock melting of ll chondrite initial rapid partial crystallization and subsequent slow cooling of the residual melt in the host to produce a differentiated object other unusual features include mm sized overgrowth objects fine grained plagioclase rich bands and coarse troilite 7 mm across grains all these features are interpreted as having crystallized from melts produced by a single transient shock event followed by slow cooling a subsequent shock event of moderate s3 intensity produced veining and transformed some of the pyroxene into the clinoenstatite polytype pentlandite together with associated troilite in nwa 4859 probably formed by the breakdown of a monosulfide precursor phase at low temperature 230 c following the second shock event nwa 4859 is interpreted to be an unusual impact melt breccia that contains shock melt which crystallized in different forms at depth within the parent body

spatial organization and time dependence of jupiter s tropospheric temperatures 1980 1993 the spatial organization and time dependence of jupiter s temperatures near 250 millibar pressure were measured through a jovian year by imaging thermal emission at 18 micrometers the temperature field is influenced by seasonal radiative forcing and its banded organization is closely correlated with the visible cloud field evidence was found for a quasi periodic oscillation of temperatures in the equatorial zone a correlation between tropospheric and stratospheric waves in the north equatorial belt and slowly moving thermal features in the north and south equatorial belts there appears to be no common relation between temporal changes of temperature and changes in the visual albedo of the various axisymmetric bands

transport and mixing in jupiter s stratosphere inferred from comet s l9 dust migration abstract we use a series of 230 nm wavelength images acquired with the hubble space telescope wide field and planetary camera 2 to trace the spreading of debris introduced into jupiter s stratosphere by the impact of comet shoemaker levy 9 impact debris was transported rapidly equatorward by stratospheric winds from the impact latitude at 45 to at least 20 during the 3 2 year period covered by the observations we use the observations to test the formulation of mixing and transport in two dimensional latitude height models for the jovian stratosphere two different models for the transport are considered in the first model advection by the residual circulation of west et al 1992 icarus 100 245 259 is taken to be the sole transport mechanism we find that this circulation advects the debris slowly poleward in disagreement with the observations in the second model horizontal diffusive transport by large scale quasi geostrophic eddies is also included the horizontal eddy diffusion coefficients k yy are derived from a map of annual average eliassen palm flux divergence produced by west et al 1992 introduction of the derived k yy into the dynamical model causes a rapid spreading of the debris in both the equatorward and the poleward directions we find that the predicted rate of equatorward spreading of the impact debris optical depth is in good agreement with that derived from the observations we conclude that our derived eddy k yy provides a useful first order description of zonal mean eddy transport at mid latitudes in the southern hemisphere of jupiter s stratosphere

chemical alteration and ree mobilization in meteorites from hot and cold deserts the effects of terrestrial weathering on ree mobilization are evaluated for a variety of uncommon meteorites found in antarctica and in hot deserts the meteorites analyzed include 7 non cumulate eucrites 10 shergottites 3 nakhlites 2 lunar meteorites 4 angrites 10 acapulcoites 1 winonaite and 1 brachinite in situ concentration measurements of lanthanides and selected other minor and trace elements were made on individual grains by secondary ion mass spectrometry sims in antarctic meteorites oxidation converts ce 3 to ce 4 which is less soluble than the trivalent ree resulting in ce anomalies the mineral most affected is low ca pyroxene however not all grains of a given mineral are and distinct analyses of a single grain can even yield ree patterns with and without ce anomalies the effect is most pronounced for antarctic eucrites in which ce anomalies are observed not only in individual minerals but also in whole rock samples although ce anomalies are observed in meteorites from hot deserts as well the most characteristic signs of chemical alteration in this environment are a lree enrichment with a typical crustal signature as well as sr ba and u contaminations these can modify the whole rock ree patterns and disturb the isotope systematics used to date these objects the lree contamination is highly heterogeneous affecting some grains and not others of a given mineral mainly olivine and low ca pyroxene the two minerals with the lowest ree concentrations the major conduit for ree movement is through shock induced cracks and defects and the highest levels of contamination are found in altered material filling such veins and cracks meteorites that experienced low shock levels and those that are highly recrystallized are the least altered copyright 2003 elsevier ltd

multi meteotsunami event in the adriatic sea generated by atmospheric disturbances of 25 26 june 2014 a series of meteotsunamis hit a few locations in the mediterranean and black seas during 22 27 june 2014 meteotsunamis were particularly numerous on 25 and 26 june in the adriatic sea where at least six harbours and bays were stricken by powerful waves strongest events occurred in vela luka korcula island a known meteotsunami hot spot where waves reached height of 3 m and in rijeka dubrovacka bay where strong 5 m s currents accompanied 2 5 m high waves intensification of high frequency sea level activity was observed at both the eastern and western adriatic tide gauge stations with maximum recorded wave heights reaching 68 cm ortona italy a series of individual air pressure disturbances characterized by pronounced rates of air pressure change up to 2 4 hpa 5 min limited spatial extent 50 km and high temporal variability propagated over the adriatic on 2 days in question numerical hydrodynamic model schism forced by measured and idealised air pressure disturbances was utilised to reproduce the observed adriatic sea level response several important conclusions were reached 1 meteotsunamis occurring at various parts of the coast were generated by different atmospheric air pressure disturbances 2 topographic influence can be removed from sea level spectra by computing spectral signal to background ratios the result being related to the external forcing resembles atmospheric pressure spectra 3 sea response is strongly dependant on details of atmospheric forcing and 4 over complex bathymetries like the middle and south adriatic ones numerous effects including proudman resonance edge waves strong topographical enhancement and refractions on the islands placed on the pathway of atmospheric disturbances should be taken into account to fully understand meteotsunami generation and dynamics an in depth numerical study is planned to supplement the latter conclusion and to quantify contribution of each process

wetting behavior of partial melts during crustal anatexis the distribution of hydrous silicic melts in polycrystalline aggregates of quartz the equilibrium distribution of hydrous silicic melts in polycrystalline aggregates of quartz was characterized in a series of partial melting and melt distribution experiments in the systems quartz albite orthoclase h2o and quartz anorthite h2o at 650 to 1000 mpa and 800 to 900 c near equilibrium textures in these experiments are characterized by very low quartz quartz melt wetting angles and by a substantial number of thin melt films along grain boundaries wetting angles in the h2o saturated experiments are as follows 18 at 800 c 1000 mpa and 12 at 900 c 1000 mpa in the granitic system 18 at 850 c 650 mpa 15 at 900 c 650 mpa and 15 at 900 c 1000 mpa in the quartzanorthite system in the granitic system at 900 c 1000 mpa a decrease of h2o content in melt from 17 wt at saturation to 6 wt results in a slight increase of wetting angle from 12 to 16 these low wetting angles and the observation that many grain boundaries are wetted by melt films indicate that the ratio of quartz quartz to quartz melt interfacial energies ss s1 is high 2 secondary electron imaging of fracture surfaces of melt poor samples provided a three dimensional insight into the geometry of melt at low melt fraction melt forms an interconnected network of channels along grain edges as predicted for isotropic systems with wetting angles below 60 this high permeability geometry suggests that the segregation of granitic melts is not as sluggish as previously anticipated simple compaction calculations for a permeability range of 10 12 to 10 9 m2 indicate that segregation may operate at low to moderate melt fractions below 30 vol within relatively short time scales i e 105 to 106 years quartzmelt textures show significant deviations from the equilibrium geometries predicted for isotropic partially molten systems the most consistent deviation is the pervasive development of crystallographically controlled planar faces of quartz these faces provide definitive evidence for non isotropic quartz melt surface energy for most silicates other than quartz the grain scale distribution of partial melts deviates even more significantly from equilibrium distributions in isotropic systems accordingly in order to describe adequately melt distributions in most natural source regions the equilibrium model should be modified to account for anisotropy of solid liquid interfacial energy

a dispersive wave pattern on jupiter s fastest retrograde jet at 20 s abstract a compact wave pattern has been identified on jupiter s fastest retrograding jet at 20 s the sebs on the southern edge of the south equatorial belt the wave has been identified in both reflected sunlight from amateur observations between 2010 and 2015 thermal infrared imaging from the very large telescope and near infrared imaging from the infrared telescope facility the wave pattern is present when the seb is relatively quiescent and lacking large scale disturbances and is particularly notable when the belt has undergone a fade whitening it is generally not present when the seb exhibits its usual large scale convective activity rifts tracking of the wave pattern and associated white ovals on its southern edge over several epochs have permitted a measure of the dispersion relationship showing a strong correlation between the phase speed 43 2 to 21 2 m s and the longitudinal wavelength which varied from 4 4 to 10 0 longitude over the course of the observations infrared imaging sensing low pressures in the upper troposphere suggest that the wave is confined to near the cloud tops the wave is moving westward at a phase speed slower i e less negative than the peak retrograde wind speed 62 m s and is therefore moving east with respect to the sebs jet peak unlike the retrograde nebn jet near n which is a location of strong vertical wind shear that sometimes hosts rossby wave activity the sebs jet remains retrograde throughout the upper troposphere suggesting the sebs pattern cannot be interpreted as a classical rossby wave 2d windspeeds and thermal gradients measured by cassini in 2000 are used to estimate the quasi geostrophic potential vorticity gradient as a means of understanding the origin of the a wave we find that the vorticity gradient is dominated by the baroclinic term and becomes negative changes sign in a region near the cloud top level 400 700 mbar associated with the sebs such a sign reversal is a necessary but not sufficient condition for the growth of baroclinic instabilities which is a potential source of the meandering wave pattern

ground based imaging of jovian cloud morphologies and motions ii the northern hemisphere from 1975 to 1985 abstract telescopic photographs of jupiter obtained during one jovian year 1975 1985 have been analyzed in order to study the morphology and motions of the great scale cloud systems present in the northern hemisphere during the epoch pre and post voyager flyby spacecraft mission see sanchez lavega and rodrigo 1985 astron astrophys 148 67 78 for a similar work in the southern hemisphere the texture of the north equatorial belt neb was characterized by a variable number of plumes between 11 and 15 a mean of 25 have high albedo heads rifts tilted high albedo clouds crossing the belt in the shear flow sense and turbulent wavy patterns in the northern edge we present interactions between these features as observed in 1985 elongated dark barges and rows of small dark spots were observed near the northern edge of the neb during specific epochs the high albedo north tropical zone ntrz was generally homogeneous from 1977 to 1984 but in 1976 little red spots were observed in its interior and a contrasting visible and red wavelengths narrow belt located in its center was present in 1985 however the most interesting feature in this region was the development of a prominent double disturbance ntrzd during 1975 in the high speed eastward jet at 24 n of which we present a study of its morphology and kinematics pronounced albedo changes were observed in the ntb during the whole period analyzed color contrasts in the ntrz ntb ntz regions were measured in 1985 from broadband relative photometry north of 34 n there were alternating albedo bands characterized by their longitudinal variability by the presence of small light spots in the equatorial side of the eastward jets and by elongated dark sections of the belts on the polar side the zonal wind profile u measured during this jovian year is in good agreement with that obtained from voyager s images and from previous ground based analysis

record breaking storm activity on uranus in 2014 abstract in spite of an expected decline in convective activity following the 2007 equinox of uranus eight sizable storms were detected on the planet with the near infrared camera nirc2 coupled to the adaptive optics system on the 10 m w m keck telescope on ut 5 and 6 august 2014 all storms were on uranus northern hemisphere including the brightest storm ever seen in this planet at 2 2 m reflecting 30 as much light as the rest of the planet at this wavelength the storm was at a planetocentric latitude of 15 n and reached altitudes of 330 mbar well above the regular uppermost cloud layer methane ice in the atmosphere a cloud feature at a latitude of 32 n that was deeper in the atmosphere near 2 bar was later seen by amateur astronomers we also present images returned from our hst too program that shows both of these cloud features we further report the first detection of a long awaited haze over the north polar region

thermal maps of jupiter spatial organization and time dependence of stratospheric temperatures 1980 to 1990 the spatial organization and time dependence of jupiter9s stratospheric temperatures have been measured by observing thermal emission from the 7 8 micrometer ch4 band these temperatures observed through the greater part of a jovian year exhibit the influence of seasonal radiative forcing distinct bands of high temperature are located at the poles and mid latitudes while the equator alternates between warm and cold with a period of approximately 4 years substantial longitudinal variability is often observed within the warm mid latitude bands and occasionally elsewhere on the planet this variability includes small localized structures as well as large scale waves with wavelengths longer than 30 000 kilometers the amplitudes of the waves vary on a time scale of 1 month structures on a smaller scale may have lifetimes of only days waves observed in 1985 1987 and 1988 propagated with group velocities less than 30 meters per second

tsunami taxonomy and detection from recent mediterranean tide gauge data abstract sea level records collected in digital form with high sampling rate by recently upgraded tide gauges located along the mediterranean coasts are subjected to a posteriori investigation to examine and characterize occurrence of sea level oscillations in the tsunami period range induced by both underwater or coastal earthquakes and by meteorological events after performing a rigorous quality control procedure on the raw sea level time series a wavelet based analysis is applied to 2 h high pass filtered data to identify oscillations generated by earthquakes and a few events are modeled aiming to verify travel time and expected spectral shape seismic tsunami oscillations that are not reported in published catalogues are identified in the sea level records of the period 2010 2014 just after three different earthquake events a method is proposed to detect occurrence of tsunami like oscillations of meteorological origin from the available tidal records based on the distribution of the detided level process over spectral bandwidth parameter and mean period the developed methodology is also the first presented which allows to distinguish sea wave induced harbor seiches from fluctuations of meteorological origin associated with passage of atmospheric disturbances meteotsunamis in sea level time series the results of the analyses show that during the considered period in the mediterranean sea tsunamis of seismic origin are rare and weak meteotsunamis on the contrary are relatively frequent and in critical areas may reach intensities exceeding astronomical tide the availability of the recently acquired high frequency records and the presented approach allow to extend the list of recorded tsunami events of both seismic and meteorological origin the identified event sets may be used for improved hazard analyses and risk assessments along the mediterranean coasts

a study of the time variability of jupiter s atmospheric structure abstract jupiter s south equatorial belt seb underwent a dramatic increase in reflectivity in june july 1989 the equatorial zone ez decreased in reflectivity slightly throughout 1988 1989 four nights of photometrically calibrated ccd images of jupiter obtained throughout the period of seb and ez activity have been used to construct vertically inhomogeneous atmospheric structure models these models were constructed to match the center to limb behavior of constant latitude scans obtained from images taken in broadband blue and red near ir continuum and methane bands the vertical structure models allow direct quantitative comparison between different latitudinal regions and more importantly between different epochs it was found that the dramatic increase in the seb reflectivity can be explained with an increase in both the optical thickness from 3 1 to 5 1 and the single scattering albedo of the upper tropospheric cloud from 0 0 980 0 001 to 0 997 0 001 in the blue for the ez the rate of decrease in reflectivity has been very subtle a small decrease in the single scattering albedo is detected from 0 0 994 0 001 to 0 992 0 001 in the blue and a slight change in the optical depth of the upper tropospheric cloud may be detected from 5 1 to 4 1 no significant change in the pressure levels of the clouds for either of the latitude regions is required to adequately fit the data

constraints on the role of impact heating and melting in asteroids received 1996 august 30 accepted in revised form 1997 january 30 abstract imaging of asteroids gaspra and ida and laboratory studies of asteroidal meteorites show that im pacts undoubtedly played an important role in the histories of asteroids and resulted in shock metamorphism and the formation of breccias and melt rocks however in recent years impact has also been called upon by numerous authors as the heat source for some of the major geological processes that took place on asteroids such as global thermal metamorphism of chondrite parent bodies and a variety of melting and igneous events the latter were proposed to explain the origin of ureilites aubrites mesosiderites the eagle station pallasites acapulcoites lodranites and the iab iiicd and iie irons we considered fundamental observations from terrestrial impact craters combined with results from laboratory shock experiments and theoretical consider ations to evaluate the efficiency of impact heating and melting of asteroids studies of terrestrial impact craters and relevant shock experiments suggest that impact heating of aster oids will produce two types of impact melts 1 large scale whole rock melts total melts not partial melts at high shock pressure and 2 localized melts formed at the scale of the mineral constituents mineral specific or grain boundary melting at intermediate shock pressures the localized melts form minuscule amounts of melt that quench and solidify in sifu thus preventing them from pooling into larger melt bodies partial melting as defined in petrology has not been observed in natural and experimental shock metamor phism and is thermodynamically impossible in a shock wave induced transient compression of rocks the total impact melts produced represent a minuscule portion of the displaced rock volume of the parent crater internal differentiation by fractional crystallization is absent in impact melt sheets of craters of sizes that can be tolerated by asteroids and impact melt rocks are usually clast laden thermal metamorphism of country rocks by impact is extremely minor experimental and theoretical considerations suggest that 1 single dis ruptive impacts cannot raise the average global temperature of strength or gravity dominated asteroids by more than a few degrees 2 cumulative global heating of asteroids by multiple impacts is ineffective for asteroids less than a few hundred kilometers in diameter 3 small crater size low gravity and low impact velocity suggest that impact melt volume in single asteroidal impacts is a very small 0 014 1 fraction of the total displaced crater volume 4 total impact melt volume formed during the typical lifetime of an asteroid is a small fraction 0 001 of the volume of impact generated debris and 5 much of the impact melt generated on asteroidal targets is ejected from craters with velocities greater than escape velocity and thus not retained on the asteroid the inescapable conclusion from these observations and calculations is that impacts cannot have been the heat source for the origin of the meteorite types listed above and we must turn to processes other than impact such as decay of short lived radionuclides or electromagnetic induction during an early t tauri phase of the sun to explain heating and melting of the parent bodies of these meteorites

thermal evolution and interaction between impact melt sheet and footwall a genetic model for the contact sublayer of the sudbury igneous complex canada 1 the sudbury igneous complex sic and associated ni cu pge mineralization has been interpreted in terms of a large meteorite impact event in this study the thermal relationship between the large cooling melt sheet and the surrounding country rock is examined in terms of its role in an evolving thermal gradient rather than as a passive receptacle for the melt sheet above thermal modeling of this environment is undertaken using physical and thermal constraints appropriate to the sic and assuming heat dissipation from the 2 5 km thick superheated melt sheet 1800 c by either diffusion with zero convection or by rapid convection within the melt sheet with zero convection basal cooling produces a solid base which lowers conductivity such that the immediate footwall rocks reach 1000 c producing partial melting that extends 200 m into the footwall in a rapidly convecting melt sheet the initial footwall chill is remelted and high temperatures maintained within the sheet close to the contact this results in higher temperatures being attained in the immediate footwall 1100 1200 c inducing complete melting of proximal footwall and partial melting to depths of 500 m below the melt sheet proximal footwall consists of paleoproterozoic huronian basalts granitoids and sediments exposed in the south range overlying archaean gneisses and granitoids total and partial melting of this material early in the cooling history of the melt sheet and the subsequent gravitational accommodation of these melts according to density would produce a basalt dominated basal liquid corresponding to the so called contact sublayer the thermal aureole predicted by our models is consistent with that preserved around the north range of the sic assuming 800 m of thermally induced erosion at the contact

interfacial tension between magmatic sulfide and silicate liquids constraints on kinetics of sulfide liquation and sulfide migration through silicate rocks we have measured the interfacial tension sf between sulfide and silicate melts over the temperature range from 1250 to 1325 c by in situ measurement of the shapes of sessile drops of sulfide immersed in silicate melt sitting upon level alumina substrates the silicate melt was an alkali free synthetic basaltic liquid the sulfide melts were synthetic mixtures of fe cu ni s or fe s o the interfacial tension ranges from about 500 mj m 2 for sulfide of fes composition to approximately 600 mj m 2 for sulfide containing 16 wt cu or 6 5 wt ni and up to 650 mj m 2 for fe s o liquid containing 4 wt o contact angles vary from 150 to 180 showing that sulfide liquid does not wet oxide minerals in silicate magmas the density of sulfide melt does not depend strongly on cu or ni content remaining between 4 0 and 4 5 g cm 3 over the range of cu and ni contents expected in sulfide magmas but increases substantially to about 5 5 g cm 3 in fe s o melts containing 4 wt o our results can be combined with conventional concepts of nucleation theory to indicate that when silicate magmas exist at small degrees of supersaturation sulfide drops may nucleate rarely and at widely spaced intervals leading to kinetic control of the compositions of the resulting droplets in light of our results we use simple scaling arguments to argue that sulfide magmas are not capable of migrating through partially molten silicate rocks by capillary forces alone but may be forced through narrow grain boundaries or grain edges only by the flow of the enclosing silicate melt during melt extraction by compaction of partially molten mantle peridotite it is highly unlikely that silicate flow rates could be sufficiently rapid to permit the entrainment of droplets of sulfide liquid at temperatures below the solidus of enclosing silicate rocks sulfide melt will be free to travel along fractures or grain boundaries the mobility of sulfide melts through completely solidified silicate rocks may account for the widespread observation that late stage highly fractionated sulfide liquids have escaped from cooling bodies of massive sulfide to form veins and disseminations of cu rich sulfide minerals in their silicate host rocks

shock post shock annealing and post annealing shock in ureilites the thermal and shock histories of ureilites can be divided into four periods 1 formation 2 initial shock 3 post shock annealing and 4 post annealing shock period 1 occurred 4 55 ga ago when ureilites formed by melting chondritic material impact events during period 2 caused silicate darkening undulose to mosaic extinction in olivines and the formation of diamond lonsdaleite and chaoite from indigenous carbonaceous material alkali rich fine grained silicates may have been introduced by impact injection into ureilites during this period about 57 of the ureilites were unchanged after period 2 during period 3 events impact induced annealing caused previously mosaicized olivine grains to become aggregates of small unstrained crystals some ureilites experienced reduction as feo at the edges of olivine grains reacted with c from the matrix annealing may also be responsible for coarsening of graphite in a few ureilites forming euhedral appearing idioblastic crystals orthopyroxene in meteorite hills met 78008 may have formed from pigeonite by annealing during this period the rb sr internal isochron age of 4 0 ga for met 78008 probably dates the annealing event at this late date impacts are the only viable heat source about 36 of ureilites experienced period 3 events but remained unchanged afterwards during period 4 7 of the ureilites were shocked again as is evident in the polymict breccia elephant moraine eet 83309 this rock contains annealed mosaicized olivine aggregates composed of small individual olivine crystals that exhibit undulose extinction ureilites may have formed by impact melting chondritic material on a primitive body with heterogeneous o isotopes plagioclase was preferentially lost from the system due to its low impedance to shock compression brief melting and rapid burial minimized the escape of planetary type noble gases from the ureilitic melts incomplete separation of metal from silicates during impact melting left ureilites with relatively high concentrations of trace siderophile elements

petrology and geochemistry of patuxent range 91501 a clast poor impact melt from the l chondrite parent body and lewis cliff 88663 an l7 chondrite we have performed petrologic and geochemical studies of patuxent range pat 91501 and lewis cliff lew 88663 pat 91501 originally classified as an l7 chondrite is rather a unique near total impact melt from the l chondrite parent body lewis cliff 88663 was originally classified as an achondrite but we find that it is a very weakly shocked l7 chondrite pat 91501 is an unshocked homogeneous igneous textured ultramafic rock composed of euhedral to subhedral olivine low ca pyroxene augite and chrome rich spinels with interstitial albitic plagioclase and minor silica alumina alkali rich glass only 10 relic chondritic material is present olivine grains are homogeneous fa25 2 26 8 low ca pyroxene wo1 9 7 2en71 9 78 2fs19 9 20 9 and augite wo29 8 39 0en49 2 55 3fs11 8 14 9 display a strong linear tio2 al2o3 correlation resulting from igneous fractionation plagioclase is variable in composition or3 0 7 7ab79 8 84 1an8 2 17 2 chrome rich spinels are variable in composition and zoned from cr rich cores to ti al rich rims some have evolved compositions with up to 7 9 wt tio2 pat 91501 bulk silicate has an l chondrite lithophile element composition except for depletions in zn and br siderophile and chalcophile elements are highly depleted due to sequestration in centimeter size metal troilite nodules the minerals in lew 88663 are more uniform in composition than those in pat 91501 olivine grains have low cao and cr2o3 contents similar to those in l5 6 chondrites pyroxenes have high tio2 contents with only a diffuse tio2 al2o3 correlation low ca pyroxenes are less calcic wo1 6 3 1en76 5 77 0fs20 4 21 4 while augites wo39 5 45 6en46 8 51 1fs7 6 9 4 and plagioclases or2 6 5 7ab74 1 83 1an11 2 23 3 are more calcic spinels are homogeneous and compositionally similar to those in l6 chondrites lew 88663 has an l chondrite bulk composition for lithophile elements and only slight depletions in siderophile and chalcophile elements that are plausibly due to weathering and or sample heterogeneity