global multispectral mosaics of the icy galilean satellites multispectral mosaics of the three icy galilean satellites have been produced from low to moderate resolution voyager images the digital image data have been calibrated using preflight and in flight calibration data and reduced to normal albedos for four color band passes centered at 0 35 0 41 0 48 and 0 59 microns the individual images have been geometrically corrected mosaiked and presented in a normal cylindrical map projection at a uniform scale of 8 km pixel preliminary analysis of the normal albedo data shows that 1 the darkest terrains on the satellites are the dark regions on callisto 2 the brightest regions are bright plains regions on europa and bright fresh craters on ganymede 3 bright craters on ganymede and its dark cratered regions are both significantly brighter than comparable terrains on callisto and 4 europa exhibits several distinct spectral units with regions on the trailing hemisphere having lower relative ultraviolet spectral reflectance than areas on the leading hemisphere this is consistent with proposals that io related plasma impact on europa s trailing side has altered its optical properties

experimental investigations on the thermal conductivity characteristics of beishan granitic rocks for china s hlw disposal abstract crystalline rocks are potential host rock types for the construction of high level radioactive waste hlw repositories a better understanding of thermal conductivity of rocks is essential to safe evaluation and engineering optimization of a hlw disposal system in the rock at depth in the present study experimental investigations on the thermal conductivity characteristics of 47 pairs of granitic rock specimens were conducted using the transient plane source tps method the specimens were collected from borehole cores in the beishan area which is being considered as the most potential candidate area for china s hlw repository to evaluate geological nature of the rocks mineralogical compositions of the rocks were identified and porosity of the specimens was measured the thermal conductivities of the specimens under dry and water saturated conditions were determined and the effect of water saturation on the thermal conductivity was investigated in addition the influence of temperature and axial compression stress on the thermal conductivity of dry specimens was studied the results revealed that the thermal conductivity of tested rocks was dependent on water saturation temperature and compression stress based on the obtained data some models considering porosity were established for describing the thermal conductivity characteristics of the tested rocks furthermore when the rocks have a similar porosity the quartz content dominates the thermal conductivity and there exists an obvious increase of the thermal conductivity with increasing quartz content the test results constitute the first systematic measurements on the beishan granitic rocks and can further be used for the development of thermal models for predicting thermal response near the underground excavations for hlw disposal

the improve 1 storm of 1 2 february 2001 part i development of a forward tilted cold front and a warm occlusion abstract analysis of observations and the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 are used to study the development of a forward tilted cold front off the coast of washington state the vertical velocity associated with the cold front produced a wide cold frontal rainband in the early stage of development the midtropospheric baroclinic zone or upper cold front moved forward with time over the warm sector to produce a structure similar to a split front the movement of the upper cold front was due to horizontal transport and frontogenetical propagation the frontogenetical propagation was produced by a combination of tilting and diabatic frontogenesis which resulted in a negative positive couplet of frontogenesis straddling the baroclinic zone the lower tropospheric cold front eventually caught up with the warm front to form a classical warm occlusion in the initial occluding process the converging frontal zones tilted i

the thermal conductivity for granite with various water contents the thermal conductivities of granite were measured under different conditions of porosity and water content to investigate the effects of the porosity and water content on the thermal conductivity for the dry samples the thermal conductivities range from 2 12 w mk for the rocks with a high porosity to 3 12 w mk for the ones with a low porosity water sorbed samples have greater thermal conductivities than dry samples of the same granite the thermal conductivities range from 2 99 w mk for granites with a high porosity to 3 62 w mk for ones with a low porosity under saturated condition

dark halo craters and the thickness of grooved terrain on ganymede dark halo craters in grooved terrain on ganymede represent potential probes of the subsurface geology these craters are surrounded by a broad diffuse low albedo annulus or halo halo radius is linearly proportional to crater radius indicating that the halo is related to the continuous ejecta deposit of the crater and is not removed by natural aging processes such as regolith development and exposure to the space environment the halos have orange violet albedo ratios that are intermediate between ratios associated with grooved terrain and cratered terrain we propose that halos result from the incorporation of cratered terrain material into crater ejecta in uruk sulcus only craters greater than 12 km in diameter have halos indicating that the cratered terrain material there forms a stratigraphic horizon buried at depth in the grooved terrain into which only larger craters can excavate this depth can be calculated from the transition diameter by reconstructing the transient crater we calculate a depth of excavation corresponding to the depth of burial of cratered terrain of 1 0 to 1 6 km this shallow burial is inconsistent with deep subsidence and burial stoping into the interior or lateral spreading apart of ancient cratered terrain units but is consistent with a filled graben model for grooved terrain where relatively clean ice has been emplaced over downdropped blocks of cratered terrain

a geometric analysis of surface deformation implications for the tectonic evolution of ganymede abstract a visual nonalignment of the furrows and the circularity of impact craters are used to study surface deformation on ganymede the furrow system is examined to test the hypothesis that lateral motion has taken place between areas of dark terrain results show that while lateral motion cannot be ruled out it may not be required to explain the geometry of the system initial nonconcentricity of the furrows or an early period of penetrative deformation shortly after furrow formation could also account for the present configuration centers of curvature of the furrows in galileo and marius regiones are numerically determined and it is shown that if lateral movement did occur it is not possible to determine the amount of displacement the axial ratios of impact craters in the uruk sulcus region which separates galileo and marius regiones are determined and show that large scale shear deformation has not occured in that area since bright terrain was emplaced deformation of impact craters within galileo regio suggests that ganymede s lithosphere has behaved rigidly throughout most of the satellite s evolution the shapes and orientations of impact craters in dark terrain around wedges of bright terrain are used to place an upper limit on the amount of extension associated with bright terrain formation

re examination of the split cold front in the british isles cyclone of 17 july 1980 an analysis of an mm5 model simulation of a cyclone that passed over the british isles on 17 july 1980 indicates that the cyclone had some characteristics of both the split cold front model of browning and monk 1982 and of a schematic by browning and roberts 1996 most importantly the cyclone had the characteristic upper level baroclinic zone and its associated vertical velocity in advance of the surface front this is an integral part of both the split cold front model of browning and monk and browning and roberts s schematic and confirms the analysis of browning and monk simultaneously at different locations the cyclone also had the characteristics of a warm occlusion in the lower levels with the portion of the cold front that was above the warm front tipped forward with height the lower and upper portions of the cold front were not only fronts in equivalent potential temperature as proposed by browning and monk but true baroclinic zones with significant associated vertical velocity the complex structure of this cyclone in the british isles was similar to that of some storms in the pacific northwest of the united states locatelli et al 2005 copyright 2005 royal meteorological society

lunar dark haloed impact craters origin and implications for early mare volcanism remote sensing and photogeologic data were used to determine the composition and origin of lunar dark haloed craters near infrared reflectance spectra were obtained for numerous dark haloed impact craters located on either the ejecta blankets of large impact craters or imbrian and nectarian age light plains deposits spectral thermal radar and photogeologic data conclusively demonstrate that copernicus h and other dark haloed craters on the ejecta blanket of copernicus excavated mare basalts from beneath lighter surface deposits rich in highlands material analyses of reflectance spectra of dark haloed craters on light plains indicate that in every instance these craters exposed mare basalt which had previously been covered by varying thicknesses of highlands debris in the schiller schickard region a relatively thick highlands unit was emplaced as a result of the orientale impact event on the interior of balmer basin marelike basalt has been excavated from beneath much thinner highlands deposits emplaced by nearby craters mafic orbital geochemical anomalies are commonly associated with regions with abundant light plains deposits which exhibit dark haloed impact craters apparently some mare material has been incorporated into the regolith either by local mixing during the emplacement of the highlands debris or by subsequent vertical mixing the results of recent remote sensing photogeologic and lunar sample studies strongly indicate that mare volcanism was a significant process during much of the pre imbrian and may have been initiated as early as 4 2 4 3 ga these very early volcanic episodes contributed materials to the lunar surface which were incorporated into the upper portion of the highlands crust by subsequent impact mixing models concerning the extent and duration of mare volcanism as well as those involving the composition and thermal evolution of the lunar interior will have to be revised

constraints on the expansion of ganymede and the thickness of the lithosphere grooves and furrows have been interpreted as grabens resulting from extension of ganymede s lithosphere geologically reasonable estimates of the dip 90 60 and displacement less than 1 km to a few hundred meters of faults bounding grooves on ganymede allow calculation of the extension and surface area increase 0 04 2 required for the formation of all grooved terrain the implied radius increase is thus limited between 0 02 and 1 1 planetary expansion is the maximum possible since formation of the grooved terrain began similar estimates for faults bounding furrows the oldest preserved tectonic features on ganymede indicate a maximum surface area increase of 0 5 for the best developed furrow system which is located in galileo regio if equivalent furrow systems existed on all of the cratered terrain then a maximum of 0 5 increase in surface area of ganymede is possible after the formation of the lithosphere and prior to the formation of grooved terrain faults bounding simple graben originate at a subsurface mechanical discontinuity and propagate upwards resulting in grabens with similar widths and similar spacings between members of a set the depth to this mechanical discontinuity for furrows and grooves on ganymede must give at least a minimum lithosphere thickness because it is impossible for faults to originate and propagate upwards from a point below the lithosphere therefore the minimum lithosphere thickness on ganymede is 5 km and 9 km in marius and galileo regiones respectively at the time of furrow formation and 4 km at the time of groove formation

formation of crater palimpsests on ganymede crater palimpsests on ganymede are circular features of high albedo apparently formed by impacts very early in the satellite s history some palimpsests have distinct outward facing slopes at their outer margins suggesting that they are distinct deposits of significant thickness this view is supported by observations of superimposed craters that excavate through palimpsest deposits into underlying materials of contrasting albedo we suggest that crater palimpsests may result from volcanic extrusions triggered by large impact events early in ganymede s history impact excavation that occurred to a sufficient depth would penetrate the satellite s thin primordial lithosphere allowing mobile buoyant material from a vigorously convecting mantle to rise to the surface upon reaching the surface the material would spread radially to produce a circular deposit of relatively high albedo as the lithosphere cooled and thickened palimpsest formation would have ceased consistent with the observed concentration of palimpsest formation in the earliest part of ganymede s recorded geologic history constraints on the nature of the extruded material may be derived from a simple model of emplacement we use an analytic model for axisymmetric viscous flow to constrain the flow viscosity in terms of the aspect height radius ratio of the palimpsest a measured value of 0 02 would imply a viscosity marginally consistent with glacial ice viscosities smaller values of which are likely would imply still lower viscosities more appropriate to partially liquid flow if such flows were described by a bingham rheology their yield strengths were of the order of 1 kpa this is lower than is typical for even very mobile silicate lavas but may be reasonable for a water ice slush ice extrusion could have been a slow process taking thousands of years while slush extension would have been essentially contemporaneous with the impact event for the case of either solid ice and slush extrusion our conclusions for the thermal structure of ganymede at the time of palimpsest formation are similar there was a thin 10 km conducting lithosphere underlain by a vigorously convecting mantle that was very close to the solidus temperature

pedestal craters on ganymede abstract the high resolution voyager images of ganymede show a class of fresh craters 6 89 km in diameter which is distinguished by an ejecta blanket similar to those seen for some types of martian craters one hundred and eighty five were identified and studied for trends with respect to latitude longitude and terrain type no correlation of the ratio of ejecta diameter to crater diameter was found as a function of latitude or longitude and there is only a suggestion of a trend in this ratio with respect to major terrain types central peak frequency is greatest for the smaller crater diameters central pit occurrence dominates central peak occurrence at crater diameters 35 km we conclude that the ejecta morphology probably results from impact into an icy target the question of whether atmospheric ejecta particle drag contributes to ejecta blanket morphologies on planets with an atmospheric cannot be resolved entirely from the voyager images the image resolution is insufficient to show diagnostic flow features on the ejecta if they exist or to detect evidence of any other ejecta deposits which would lie beyond the pedestal predicted by some researchers to exist only on bodies with an atmosphere

snow control on active layer thickness in steep alpine rock walls aiguille du midi 3842 m a s l mont blanc massif since the early 2000s a remarkable amount of rockfalls has been observed in permafrost areas of the mid latitude mountain ranges concurrently to hot summers this study explores the seasonal thaw st in permafrost rock walls of the aiguille du midi site 3842 m a s l mont blanc massif we first analyse six years of temperature records in three 10 m deep boreholes against air temperature at and a four year time series of pictures showing the snow conditions on two rock faces then we test the sensitivity of the active layer against eight snow fall scenarios using the 1 d surface energy balance and heat conduction model cryogrid 3 forced by in situ measurements from a vertical face snow falls occur all the year round at this elevation and play an important role for the active layer thickness alt but the snow cover and its control are highly heterogeneous a long lasting of a snow cover during spring early summer delays the st and reduces the alt the thicker and the more spatially continuous is the snow cover the stronger are the delay and alt reduction convective clouds could also reinforce this pattern the summer at and heat waves are the dominant controlling factors of the alt but summer snow falls can sometimes persist for several days on the rock surface and reduce the effect of the heat waves active layer can thicken during the early fall except if the snow starts to accumulate on the rock surface and favours the refreezing the timing of the snow fall is the most critical parameter to determine the snow effect on the alt this study suggests that the characteristics of the bedrock and snow accumulation steepness surface roughness and sun exposure must be taken into account to better understand the formation and changes of the active layer and its possible implications for rockfall triggering

ice temperature and high geothermal flux at siple dome west antarctica from borehole measurements a verlical temperature profile through the west antarctic ice sheet wais at the summit of siple dome reveals an elevated geothermal flux this could be the root cause for the existence of a dynamic ice stream system in the wais siple dome is still frozen on its bed but adjacent ice streams have bed temperatures at the pressure melting point of ice although present day temperature increases due to climatic change do not have an immediate effect on the basal conditions that control the velocity of the ice indirect ellbcts like a rapid disintegration of the floating ice shelves or additional melt water input at the surface could give rise to speed up of the ice streams with an ensuing rise in sea level ongoing melt at the base of the ice and changes at the margins will allow continued rapid flow of the ice streams with a possibility of disintegration within a relatively short period of time of at least part of the wais

the mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones x wavelike rainbands in an occlusion abstract the dynamical and microphysical structures of trains of wavelike rainbands in an occlusion are described the rainbands were located in a region of potential instability behind the cold front aloft they were 3 5 km wide 80 km long spaced 5 10 km apart and arranged nearly parallel to the winds at their upper levels temperatures fluctuated in a wavelike manner in and out of the rainbands the temperatures inside the rainbands being 1 2 c higher than outside the vertical air velocities also fluctuated near the top of the rainbands upward velocities of 1 m s 1 relative to the ambient air were present inside the rainbands but outside of the rainbands the relative velocities were 1 m s 1 downward at lower levels the fluctuations in vertical velocities were about one half those at the upper levels and they showed fewer systematic variations with respect to the location of the wavelike rainbands the convergence divergence and airflow patterns had wavelike structures in the vicinity of the r

geology before pluto pre encounter considerations the cameras of new horizons will provide robust data sets that should be imminently amenable to geological analysis of the pluto system s landscapes in this paper we begin with a brief discussion of the planned observations by the new horizons cameras that will bear most directly on geological interpretability then we broadly review the major geological processes that could potentially operate on the surfaces of pluto and its major moon charon we first survey exogenic processes i e those for which energy for surface modification is supplied externally to the planetary surface impact cratering sedimentary processes including volatile migration and the work of wind we conclude with an assessment of the prospects for endogenic activity in the form of tectonics and cryovolcanism

thermal and depositional history of early permian rio bonito formation of southern parana basin brazil abstract the parana basin is a large volcano sedimentary basin with a complex depositional history from ordovician to the cretaceous period during permian significant amounts of organic rich beds accumulated within the rio bonito and irati formations representing deposition in coastal deltaic and barrier lagoon and shallow marine environments respectively in this work the thermal history of these beds is examined from 16 vitrinite reflectance analyses of coal beds rio bonito formation integrated with previous data on coal rank and 21 apatite fission track aft analyses collected from 17 well profiles in the south of the parana basin coal samples showed three different maturity levels two with reflectances of 0 4 0 6 and 0 6 0 8 rr formed by the natural burial history of the basin the latter is restricted to the torres syncline area in contrast the third group reached much higher values 1 0 5 0 rr related to intrusive igneous rocks the aft data show thermal consistency with the reflectance values the sandstone samples related to the two lower reflectance patterns were partially reset preserving aft ages older than the stratigraphic age of the bed otherwise the samples severely affected by the magmatism have cretaceous and early cenozoic ages but some were much younger than the last magmatic event implying deep burial before cooling onset the mean track length distribution of the partially reset samples is short due to the inheritance of tracks preserved from basement cooling history however the population of fully reset samples gives crucial information on the maximum temperature reached and the age when cooling started at these conditions around 1 0 to 3 0 km of the parana basin sequences would have been removed from the surface of the studied areas by erosion since cretaceous regional variations in the amounts of removed sections were controlled by the structural framework mostly regional nw se and ne sw oriented structures

grooved terrain on ganymede first results from galileo high resolution imaging abstract high resolution galileo imaging has provided important insight into the origin and evolution of grooved terrain on ganymede the uruk sulcus target site was the first imaged at high resolution and considerations of resolution viewing geometry low image compression and complementary stereo imaging make this region extremely informative contrast variations in these low incidence angle images are extreme and give the visual impression of topographic shading however photometric analysis shows that the scene must owe its character to albedo variations a close correlation of albedo variations to topography is demonstrated by limited stereo coverage allowing extrapolation of the observed brightness and topographic relationships to the rest of the imaged area distinct geological units are apparent across the region and ridges and grooves are ubiquitous within these units the stratigraphically lowest and most heavily cratered units lineated grooved terrain generally show morphologies indicative of horst and graben style normal faulting the stratigraphically highest groove lanes parallel ridged terrain exhibit ridges of roughly triangular cross section suggesting that tilt block style normal faulting has shaped them these extensional tectonic models are supported by crosscutting relationships at the margins of groove lanes thus a change in tectonic style with time is suggested in the uruk sulcus region varying from horst and graben faulting for the oldest grooved terrain units to tilt block normal faulting for the latest units the morphologies and geometries of some stratigraphically high units indicate that a strike slip component of deformation has played an important role in shaping this region of grooved terrain the most recent tectonic episode is interpreted as right lateral transtension with its tectonic pattern of two contemporaneous structural orientations superimposed on older units of grooved terrain there is little direct evidence for cryovolcanic resurfacing in the uruk sulcus region instead tectonism appears to be the dominant geological process that has shaped the terrain a broad wavelength of deformation is indicated corresponding to the voyager observed topography and may be the result of ductile necking of the lithosphere while a finer scale of deformation probably reflects faulting of the brittle near surface the results here form a basis against which other galileo grooved terrain observations can be compared

evidence for europa like tectonic resurfacing styles on ganymede 1 very high resolution imaging and stereo topographic data obtained during the galileo g28 encounter with ganymede show 1 evidence for europa like crustal spreading and resurfacing to form portions of the bright terrain and 2 bright terrain that appears smooth at voyager resolution and thus a strong candidate for cryovolcanism but instead is tectonically deformed and lacks embayment relationships when viewed at high resolution in contrast to previous views these new data show that tectonism has been the dominant process in shaping some very smooth areas and that ganymede appears to have experienced europa like crustal spreading during its previous history

thermal conductivity anisotropy of metasedimentary and igneous rocks 1 thermal conductivity anisotropy was determined for three sets of metasedimentary and igneous rocks from central utah usa most conductivity measurements were made in transient mode with a half space line source instrument oriented in two orthogonal directions on a flat face cut perpendicular to bedding one orientation of the probe yields thermal conductivity parallel to bedding kpar directly the other orientation of the probe measures a product of conductivities parallel and perpendicular to bedding from which the perpendicular conductivity kperp is calculated some direct measurements of kpar and kperp were made on oriented cylindrical discs using a conventional divided bar device in steady state mode anisotropy is defined as kpar kperp precambrian argillites from big cottonwood canyon have anisotropy values from 0 8 to 2 1 with corresponding conductivity perpendicular to bedding of 2 0 to 6 2 w m 1 k 1 anisotropy values for price canyon sedimentary samples are less than 1 2 with a mean of 1 04 although thermal conductivity perpendicular to bedding for the samples varied from 1 3 to 5 0 w m 1 k 1 the granitic rocks were found to be essentially isotropic with thermal conductivity perpendicular to bedding having a range of 2 2 to 3 2 w m 1 k 1 and a mean of 2 68 w m 1 k 1 the results confirm the observation by deming 1994 that anisotropy is negligible for rocks having kperp greater than 4 0 w m 1 k 1 and generally increases for low conductivity metamorphic and clay rich rocks there is little evidence however for his suggestion that thermal conductivity anisotropy of all rocks increases systematically to about 2 5 for low thermal conductivity rocks

possible breakup of dark terrain on ganymede by large scale shear faulting a system of arcuate furrows in galileo regio and marius regio two large blocks of ancient dark terrain has previously been proposed to be the remnant of an originally more concentric furrow set that was disrupted by shear estimates of the two regions poles of furrow concentricity indicate a considerable westward offset of the galileo regio pole these measurements suggest the possibility of about 500 km of left lateral offset of the two areas four additional independent structural indicators support this hypothesis there is evidence that shear deformation was concentrated along a major structural lineament which closely follows a small circle about 45 of arc of radius which encloses galileo regio and that a smaller amount of distributed shear occurred across an adjacent 500 to 1500 km wide band there is also morphologic evidence for zones of minor right lateral shear between central and southern marius regio and between barnard and nicholson regio and for a zone of minor left lateral shear in nun sulci stratigraphic relations indicate that any major shear offsets occurred before and during the earliest stages of grooved terrain formation before most grooves had formed and before virtually all light material had been emplaced however regionally dominant groove orientations are generally consistent with orientations expected for transtensional features either shear strain or the shear s driving mechanism may have had a long term effect on patterns of deformation of ganymede s lithosphere

the tectonics of ganymede the surface of ganymede the largest icy jovian satellite is composed of two distinct terrain types showing abundant evidence of global scale tectonics there is geological evidence consistent with the formation of younger bright terrain by the emplacement of relatively clean ice into rift zones developed in the more silicate rich dark terrain

geometry of a large scale low angle midcrustal thrust woodroffe thrust central australia the musgrave block in central australia exposes numerous large scale mylonitic shear zones developed during the intracontinental petermann orogeny around 560 520 ma the most prominent structure is the crustal scale over 600 km long e w trending woodroffe thrust which is broadly undulate but generally dips shallowly to moderately to the south and shows an approximately top to north sense of movement the estimated metamorphic conditions of mylonitization indicate a regional variation from predominantly midcrustal circa 520 620 c and 0 8 1 1 gpa to lower crustal 650 c and 1 0 1 3 gpa levels in the direction of thrusting which is also reflected in the distribution of preserved deformation microstructures this variation in metamorphic conditions is consistent with a south dipping thrust plane but is only small implying that a 60 km long n s segment of the woodroffe thrust was originally shallowly dipping at an average estimated angle of 6 the reconstructed geometry suggests that basement cored thick skinned midcrustal thrusts can be very shallowly dipping on a scale of many tens of kilometers in the direction of movement such a geometry would require the rocks along the thrust to be weak but field observations e g large volumes of syntectonic pseudotachylyte argue for a strong behavior at least transiently localization on a low angle near planar structure that crosscuts lithological layers requires a weak precursor such as a seismic rupture in the middle to lower crust if this was a single event the intracontinental earthquake must have been large with the rupture extending laterally over hundreds of kilometers

terrain types and local scale stratigraphy of grooved terrain on ganymede grooved terrain is subdivided on the basis of pervasive morphology into 1 groove lanes elongate parallel groove bands 2 grooved polygons polygonal domains of parallel grooves 3 reticulate terrain polygonal domains of orthogonal grooves and 4 complex grooved terrain polygons with several complexly cross cutting groove sets detailed geologic mapping of select areas employing previously established conventions for determining relative age relations reveals a general three stage sequence of grooved terrain emplacement first dissection of the lithosphere by throughgoing grooves and pervasive deformation of intervening blocks second extensive flooding and continued deformation of the intervening blocks third repeated superposition of groove lanes concentrated at sites of initial throughgoing grooves this sequence is corroborated by crater density measurements dominant orientations of groove sets are parallel to relict zones of weakness that probably were reactivated during grooved terrain formation groove lane morphology and development consistent with that predicted for passive rifts suggests a major role of global expansion in grooved terrain formation

variation of frontal and precipitation structure along a cold front a diagnostic study is presented to illustrate the sequence of events in which a warm conveyor belt wcb flow is drawn into the circulation of a developing extratropical cyclone and interacts with dry air aloft to produce distinctive precipitation structures the poleward boundary of the upstream end of the wcb was associated with a classical ana cold frontal structure the other end of the wcb flow closer to the cyclone centre was overrun by a dry intrusion of low wet bulb potential temperature air to give a split kata cold front the orientation of the surface cold front i e the wcb boundary changed significantly between these two parts but the orientation of the surface geostrophic flow within the wcb changed relatively little between the two parts the surface cold front was characterized in most places by a narrow cold frontal rainband composed of shallow line convection elements precipitation cores aligned nearly parallel to the surface geostrophic flow in the wcb the changing relationship between the frontal orientation and the direction of the surface flow accounts for the fact that the line convection elements occurred end to end to give almost two dimensional line convection along the classical ana part of the cold front but were non aligned and widely spaced along the split cold front part

thermal conductivity of water saturated rocks from the ktb pilot hole at temperatures of 25 to 300 c the conductivitites of selected gneiss two and amphibolite one core samples have been measured under conditions of elevated temperature and pressure with a needle probe water saturated thermal conductivity measurements spanning temperatures from 25 to 300 c and hydrostatic pressures of 0 1 and 34 mpa confirm the general decrease in conductivity with increasing temperature but deviate significantly from results reported from measurements on dry samples over the same temperature range the thermal conductivity of water saturated amphibolite decreases with temperature at a rate approximately 40 less than the rate for dry amphibolite and the conductivity of water saturated gneiss decreases at a rate approximately 20 less than the rate for dry gneiss the available evidence points to thermal cracking as the primary cause of the more rapid decrease in dry thermal conductivity with temperature the effects of thermal cracking were also observed in the water saturated samples but resulted in a net decrease in room temperature conductivity of less than 3 these results highlight the importance of duplicating in situ conditions when determining thermal conductivity for the deep crust

complex crater formation insights from combining observations of shock pressure distribution with numerical models at the west clearwater lake impact structure large impact structures have complex morphologies with zones of structural uplift that can be expressed topographically as central peaks and or peak rings internal to the crater rim the formation of these structures requires transient strength reduction in the target material and one of the proposed mechanisms to explain this behavior is acoustic fluidization here samples of shock metamorphosed quartz bearing lithologies at the west clearwater lake impact structure canada are used to estimate the maximum recorded shock pressures in three dimensions across the crater these measurements demonstrate that the currently observed distribution of shock metamorphism is strongly controlled by the formation of the structural uplift the distribution of peak shock pressures together with apparent crater morphology and geological observations is compared with numerical impact simulations to constrain parameters used in the block model implementation of acoustic fluidization the numerical simulations produce craters that are consistent with morphological and geological observations the results show that the regeneration of acoustic energy must be an important feature of acoustic fluidization in crater collapse and should be included in future implementations based on the comparison between observational data and impact simulations we conclude that the west clearwater lake structure had an original rim final crater diameter of 35 40 km and has since experienced up to 2 km of differential erosion

mineralogy porosity and fluid control on thermal conductivity of sedimentary rocks summary estimates of thermal conductivity of the main non clay and clay sedimentary minerals are presented especially for the case of argillaceous ones these estimates are averaged estimates based on the interpretation of laboratory conductivity porosity and mineralogy measurements performed on small volumes of the order of 100cm3 of water saturated moist and air saturated samples the sampling is representative of the main sedimentary rocks sandstones carbonates evaporites and shales and it is composed of samples considered as structurally isotropic material first we experimentally verify the first order control of mineralogy porosity and fluid content on bulk conductivity and we demonstrate that such influences may be predicted accurately using a geometric mean model as long as isotropic samples are used then we interpret the data using an inverse method in order to estimate the average mineral conductivities of the main non clay and clay minerals which give the best fit to the individual laboratory measurements through the geometric mean model the analysis is based on measurements on 82 non clay samples and 29 clay samples taken on oil well cores or cuttings on outcrops and on artificially recompacted samples estimates of average mineral conductivities returned by the inversion process for the main non clay minerals are similar to generally admitted values 7 7 w m k for quartz 3 3 w m i k for calcite 5 3 w m l k for dolomite and 6 3 w m k for anhydrite values obtained for the clay minerals are systematically lower than those obtained for non clay ones they are of the order of 1 9 w m k for illite and smectite 2 6 w m k for kaolinite and 3 3 w m l k for chlorite these estimates combined with porosity and mineralogy data are used with the geometric mean model in order to verify its first order validity for predicting thermal conductivity of small volumes of porous isotropic sedimentary rocks the bulk conductivity is predicted with an accuracy of the order of f10 per cent for moist or water saturated samples and of the order of f20 per cent for air saturated samples

effect of water saturation and temperature in the range of 193 to 373 k on the thermal conductivity of sandstone abstract the thermal conductivity of porous media is crucial for many geological and engineering projects although the thermal conductivity at low temperatures is often overlooked it is of great significance to calculate the amount of heat that the ice sheet absorbs from the earth in this study the thermal conductivity of dry and water saturated sandstone was measured in the temperature range of 193 to 373 k using a transient hot wire method all samples were collected from east china with a sample porosity distribution of 5 to 13 the effects of temperature water saturation and phase transition of fluid in the pores were investigated the results indicate that the thermal conductivity decreases with an increase in temperature and that the decrease is steeper when the temperature is below 273 k moreover it is found that the thermal conductivity of the saturated sandstone is larger than that of the dry sandstone with an increase in porosity the thermal conductivity significantly increases in saturated sandstone but remains almost the same or even decreases in dry sandstones finally it is revealed that the effect of phase transformation on the thermal conductivity is significant when the water in pores becomes ice the thermal conductivity increases significantly and increases further as the temperature decreases

implications of using broadband photometry for compositional remote sensing of icy objects water ice has such a low absorption coefficient at visual wavelengths 0 01 cm 1 that a very small amount of particulate material can significantly darken an icy surface a variety of ice plus particle mixtures were studied to show that particulate contaminations of 1 by weight even 0 1 or less in some cases in ice or frosts result in reflectance levels close to that of the contaminants in a very clear ice no bubbles it is plausible to have a reflectance 0 05 for particulate contaminations 10 7 by weight for submicron dark particles such as carbon lampblack scattering conditions compete for domination with contaminants for control of visual reflectance implying that the apparent reflectivity level and color of a surface is a poor indicator of ice content a dark surface e g albedo 0 05 does not necessarily imply that there us very little water ice present infrared jhk colors of water ice and other minerals including ice mineral mixtures show that some orthopyroxenes can have jhk colors very similar to fine grained water frosts in general it is possible that the jhk colors of an ice plus particulate mixture can fall anywhere in the classical j h versus h k diagram thus the diagram cannot be used to distinguish a predominately rock surface from one which is predominantely ice for one specific case an important exception is the case where both the j h and h k colors are 0 2 it appears that such colors indicate a relatively pure icy surface in some cases the diagram might be used as a statistical tool to distinguish between the compositions of surfaces within a class of objects but the validity of such comparisons decreases for different classes such as the main belt asteroids when compared to outer solar system satellites where water ice is more stable

radiometric performance of the voyager cameras the voyager imaging experiment provided high quality data of jupiter and the galilean satellites with the two flyby trajectories in march and july of 1979 moderately accurate radio metric measurements have been made using these data this paper evaluates the radiometric results and describes the inflight and ground geometric and radiometric correction factors the radiometric quantities of intensity i and geometric albedo i f are derived and scaling factors for each of the filters are tabulated for correcting the calibrated data from the image processing laboratory at jpl in addition the key characteristics of both voyager 1 and voyager 2 cameras are tabulated

initial thermal conditions around an underground research tunnel at shallow depth the initial thermal conditions around a shallow research tunnel in korea were investigated based on the data analysis of rock properties in situ observation and a computer simulation the measured thermal conductivity data were used for evaluating different theoretical estimations based on mineral composition porosity and saturation with a consideration of total porosity which was assumed to be twice of effective porosity the prediction with geometric mean could be improved in the case of three phase system consisted of minerals water and air however geometric mean overestimated especially in low saturation condition by using the chaudhary and bhandari equation for three phase system we could predict the measured thermal conductivity with about 10 error in low saturation condition with the data of porosity variation and saturation expected at kurt it was possible to predict the thermal conductivity increases with depth and stabilized at 3 2 w mk below 50 m considering the surface topography around kurt sequential tunnel excavation depth dependent rock properties and seasonal temperature variation of the air the time and depth dependent thermal conditions around kurt were predicted by a three dimensional computer simulation using flac3d

volcanic constructs on ganymede and enceladus topographic evidence from stereo images and photoclinometry paul m schenklunar and planetary institute houston texasjeffrey m moorespace sciences division and the seti institute nasa ames research center moffett field californiaabstract the morphology of volcanic features on ganymede differs significantly from that onthe terrestrial planets few if any major volcanic landforms such as thick flows or shieldvolcanoes have been identified to date using new stereo voyager images we have searchedganymede for relief generating volcanic constructs we observed seven major types of volcanicstructures including several not previously recognized the oldest are broad flat topped domespartially filling many older craters in dark terrain similar domes occur on enceladus togetherwith smooth dark deposits these domes indicate that the volcanic history of the dark terrain iscomplex bright terrain covers vast areas although the style of emplacement remains unclear smooth bright materials embay and flood older terrains and may have been emplaced as low viscosity fluids associated with smooth bright material are a number of scalloped shaped semi enclosed scarps that cut into preexisting terrain in planform these structures resemble terrestrialcalderas the youngest volcanic materials identified are a series of small flows that may haveflooded the floor of the multiring impact structure gilgamesh forming a broad dome theidentification of volcanic constructs up to 1 km thick is the first evidence for extrusion ofmoderate to high viscosity material on ganymede viscosity and yield strength estimates for thesematerials span several orders of magnitude indicating that volcanic materials on ganymede have arange of compositions and or were extruded under a wide range of conditions and or eruptive styles introductionthe voyager survey of the outer solar system has revealedan astonishing variety of endogenic landforms on the surfacesof icy satellites despite extensive endogenic resurfacing ofsomc satellites for example ganymede enceladus andtriton volcanism on these surfaces has little topographicexpression we do not see massive volcanic edifices similarto olympus mons or mauna kea even the best putativeexamples of volcanic landforms seen on ariel miranda triton and enceladus exhibit rarely more than 1 2 km ofrelief jankowski and squyres 1988 pozio and kargel 1989 schenk 1991a croft et al 1995 this may berelated to the soft theology of ice see poirier 1982 durham et al 1983 and kirby et al 1987 or torheology and volcanic styles peculiar to icy petrologicsystems e g kargel 1991 kargel et al 1991 well over half of the surface of ganymede radius 2634 kin has been covered by endogenic effusions it is now consideredlikely that ganymede experienced one or more episodes ofchaotic orbital behavior malhotra 1991 possiblyresulting in tidal heating volcanic resurfacing constitutes arecord of ganymede s compositional and thermal evolution andmay record some of these putative tidal heating events yetthis satellite has been the subject of morphological study for15 years without the unambiguous detection of relief copyright 1995 by the american geophysical union paper number 95je01854 0148 0227 95 95je 01854505 00generating volcanic constructions on its landscape the styleof emplacement and composition of those volcanic depositsthat have been identified remains unclear on any planetary surface volcanic and other nonimpactconstructs can be difficult to recognize in spacecraft images particularly those obtained under high sun conditions e g malin 1978 topography is especially low on the galileansatellites and imaging resolution is at best 500 m pixel major local albedo variations on ganymede further complicategeologic and topographic mapping with these problems inmind we have undertaken the production of stereo pairs ofvoyager images where coverage permits to aid in the searchfor and characterization of volcanic landforms on ganymede ssurface in addition to an examination of previously identifiedvolcanic materials we report the discovery of severalpreviously unrecognized volcanic landforms and at least twotypes with substantial relief and describe their morphologyand geologic setting morphology of volcanic depositsindicates that ganymede extrusions probably had a range oftheologies and may be compositionally variable we concludewith speculations and predictions regarding their mode ofemplacement and the implications of volcanic landforms forthe geologic evolution of ganymede stereo imaging with voyagerthis study was motivated by the recognition that asignificant fraction of the surfaces of most of the outer planetsatellites were imaged by voyager in stereo e g croft andsoderblom 1991 schenk and moore 1993 we can usestereo imaging to detect subtle topographic features that were19 009

crater densities and crater ages of different terrain types on ganymede abstract crater densities and size frequency distributions on ganymede were measured for separate areas of dark furrowed and dark smooth terrains reticulate terrain complex grooved terrain and groups of groved polygons and groove lanes having a variety of relative ages these measurements were used first together with results of previous studies to test alternate models of heliocentric and planetocentric crater forming bombardments of ganymede and callisto the spatial distribution of crater production functions on ganymede is consistent with a single impactor population having dominated cratering of that satellite s observed surface in addition relative crater ages of different ganymedean material deposits are better reconciled with the deposits stratigraphic relations if a heliocentric impactor population is assumed these results are consistent with results of previous studies interpreted here to indicate that the spatial distributions of most classes of craters on ganymede and younger craters on callisto are more consistent with heliocentric than with planetocentric bombardment the measurements were then used to infer the sequence and style of surface modification of ganymede bounds on absolute ages depend on the assumption of heliocentric bombardment dark terrain was emplaced during a prolonged period of volcanic resurfacing of older heavily cratered terrain probably at least 10 8 yrs in duration and at least 3 8 4 0 gyr ago furrows generally formed on blanket like deposits of dark material typically hundreds of meters or more in thickness soon after their emplacement furrow formation continued globally throughout the period of dark material deposition next dark terrain was deformed locally by reticulate terrain formation light terrain emplacement subsequently began at least regionally within complex grooved terrain it continued for an extended period perhaps several times 10 8 yrs in grooved lanes grooved polygons andsmooth terrain where a light material layer averaging several hundred meters or more in thickness was emplaced

estimation of the thermal conductivity anisotropy of rock with application to the determination of terrestrial heat flow a moderately large data set of mostly sedimentary and metamorphic rocks compiled from the literature shows an inverse correlation between thermal conductivity anisotropy and thermal conductivity perpendicular to bedding the empirical relationship can be represented by a simple two component end member mixing model one end member is anisotropic x z 2 5 and has a relatively low thermal conductivity perpendicular to bedding z 1 w m k the other end member is isotropic and has a relatively high thermal conductivity perpendicular to bedding 4 w m k the proposed model may be used to derive a correction for anisotropic effects observed during thermal conductivity measurements on mixtures of randomly oriented aggregates although the accuracy and reliability of a universal correction procedure remain to be determined the proposed correction scheme should enhance our ability to estimate accurately heat flow in sedimentary basins where generally only borehole cuttings are available for thermal conductivity measurements

thermal conductivity characterisation of shallow ground via correlations with geophysical parameters abstract thermal conductivity is an important physical property of geological formations for example a comprehensive assessment of the thermal conductivity variations in the shallow ground surrounding a heat exchanger borehole can be used to determine the installation parameters of a ground source heat pump however in some locations it is not possible to measure thermal conductivity directly one of the most common methods to indirectly infer thermal conductivity is to establish correlations between thermal conductivity and various geophysical parameters by utilising test data acquired from drilling sites and ascertaining the corresponding geophysical parameters via non invasive geophysical methods such correlations can be obtained at 11 test sites the thermal conductivities were measured in situ via thermal response testing and the corresponding values for the s wave velocity and density were calculated using the microtremor survey method msm the correlations between the thermal conductivity s wave velocity and density in the tested shallow ground were built by exponential fitting by utilising the established correlations two dimensional 2d cross sections along the microtremor survey line were created to illustrate the thermal conductivity variations in the shallow ground these results demonstrate that this approach can be used to infer the thermal conductivities of areas that cannot be tested directly

spherule layers crater scaling laws and the population of ancient terrestrial impactors abstract ancient layers of impact spherules provide a record of earth s early bombardment history here we compare different bombardment histories to the spherule layer record and show that 3 2 3 5 ga the flux of large impactors 10 100 km in diameter was likely 20 40 times higher than today the e belt model of early solar system dynamics suggests that an increased impactor flux during the archean is the result of the destabilization of an inward extension of the main asteroid belt bottke et al 2012 here we find that the nominal flux predicted by the e belt model is 7 19 times too low to explain the spherule layer record moreover rather than making most lunar basins younger than 4 1 gyr old the nominal e belt model coupled with a corrected crater diameter scaling law only produces two lunar basins larger than 300 km in diameter we also show that the spherule layer record when coupled with the lunar cratering record and careful consideration of crater scaling laws can constrain the size distribution of ancient terrestrial impactors the preferred population is main belt like up to 50 km in diameter transitioning to a steep distribution going to larger sizes