probing venus surface iron contents with six band visible near infrared spectroscopy from orbit machine learning models enable interpretation of orbital spectral measurements of venus using laboratory calibration data collected at venus surface temperatures partial least squares models show that total iron content can be accurately predicted using data from the six bands two in the 1 02 m window prediction errors on total wt feo are 0 50 for common subalkaline volcanic rocks accuracy is 0 42 for wt feo in alkaline rocks and 2 47 for all 18 igneous samples studied to date these robust capabilities will allow discrimination of basalt versus rhyolite granite and elucidate the rock type of the enigmatic tessera terrain on venus

determination of venus winds by ground based radio tracking of the vega balloons a global array of 20 radio observatories was used to measure the three dimensional position and velocity of the two meteorological balloons that were injected into the equatorial region of the venus atmosphere near venus midnight by the vega spacecraft on 11 and 15 june 1985 initial analysis of only radial velocities indicates that each balloon was blown westward about 11 500 kilometers 8 000 kilometers on the night side by zonal winds with a mean speed of about 70 meters per second excursions of the data from a model of constant zonal velocity were generally less than 3 meters per second however a much larger variation was evident near the end of the flight of the second balloon consistent systematic trends in the residuals for both balloons indicate the possibility of a solar fixed atmospheric feature rapid variations in balloon velocity were often detected within a single transmission 330 seconds however they may represent not only atmospheric motions but also self induced aerodynamic motions of the balloon

distribution characterization and geochemical controls of elements of concern in uranium mine tailings key lake saskatchewan canada abstract the distribution of as mo ni and se in the aqueous and solid phases of u mine tailings in the deilmann tailings management facility dtmf located at the key lake mine in northern saskatchewan canada was defined using as discharged tailings samples collected monthly starting in 1996 and core samples collected from the dtmf from 3 locations on 3 occasions between 2004 and 2009 these data indicated that the dtmf can be divided into two geochemical zones tailings generated from the deilmann ore body between 1996 and 2000 and tailings from the mcarthur river ore body mined after july 2000 the deilmann tailings solids are generally characterized by greater elemental concentrations than those in the mcarthur river tailings particularly for as co and ni these elevated concentrations are attributed to the abundance of ni co as s minerals in this ore the mean aqueous concentrations of as mo ni and se are 3 7 23 2 0 14 and 0 02 mg l 1 respectively in the deilmann porewaters and 0 20 4 16 0 06 and 0 03 mg l 1 respectively in the mcarthur river porewaters similarly the mean as mo ni and se solid phase concentrations are 5 89 10 3 69 9 3 20 10 3 and 17 4 g g 1 respectively for the deilmann tailings and 440 13 6 551 and 3 03 g g 1 in the mcarthur river tailings statistically ph remained unchanged from the time of discharge while eh values have remained oxic with no significant change between the two tailings types over 15 a of residence time results from sequential extractions thermodynamic modeling and results of complimentary research indicated that ferrihydrite solubility is the dominant control on aqueous as concentrations and also plays a role in controlling dissolved mo ni and se

windblown sand on venus preliminary results of laboratory simulations abstract small particles and winds of sufficient strength to move them have been detected from venera and pioneer venus data and suggest the existence of aeolian processes on venus the venus wind tunnel vwt was fabricated in order to investigate the behavior of windblown particles in a simulated venusian environment preliminary results show that sand size material is readily entrained at the wind speeds detected on venus and that saltating grains achieve velocities closely matching those of the wind measurements of saltation threshold and particle flux for various particle sizes have been compared with theoretical models which were developed by extrapolation of findings from martian and terrestial simulations results are in general agreement with theory although certain discrepancies are apparent which may be attributed to experimental and or theoretical modeling procedures present findings enable a better understanding of venusian surface processes and suggest that aeolian processes are important in the geological evolution of venus

probability distribution of surface wind speed induced by convective adjustment on venus abstract the influence of convective adjustment on the spatial structure of venusian surface wind and probability distribution of its wind speed is investigated using an idealized weather research and forecasting model when the initially uniform wind is much weaker than the convective wind patches of both prograde and retrograde winds with scales of a few kilometers are formed during active convective adjustment after the active convective adjustment because the small scale convective cells and their related vertical momentum fluxes dissipate quickly the large scale 4 km prograde and retrograde wind patches remain on the surface and in the longitude height cross section this suggests the coexistence of local prograde and retrograde flows which may correspond to those observed by pioneer venus below 10 km altitude the probability distributions of surface wind speed v during the convective adjustment have a similar form in different simulations with a sharp peak around 0 1 m s 1 and a bulge developing on the flank of the probability distribution this flank bulge is associated with the most active convection which has a probability distribution with a peak at the wind speed 1 5 times greater than the weibull fitting parameter c during the convective adjustment the weibull distribution p v exp v c k with best estimate coefficients of lorenz 2016 is reproduced during convective adjustments induced by a potential energy of 7 10 7 j m 2 which is calculated from the difference in total potential energy between initially unstable and neutral states the maximum vertical convective heat flux magnitude is proportional to the potential energy of the convective adjustment in the experiments with the initial unstable layer thickness altered the present work suggests that convective adjustment is a promising process for producing the wind structure with occasionally generating surface winds of 1 m s 1 and retrograde wind patches

geotechnical parameters and behaviour of uranium tailings the results of laboratory and in situ testing and test blasting the observations made on a test embankment and a description of actual construction practice associated with engineering studies fo

venus cloud level circulation during 1982 as determined from pioneer cloud photopolarimeter images ii solar longitude dependent circulation abstract a strong solar locked dependence of cloud level circulation is observed in the averaged cloud motions as well as in the ultraviolet reflectivity of the venus cloud layer as determined from pioneer venus orbiter images acquired during 1982 s s limaye c grassotti and m j kuetemeyer 1988 icarus 73 193 211 the cloud motions were determined by manually tracking cloud features while the ultraviolet reflectivity was determined by removing the scattering geometry dependence of the observed intensities in ultraviolet images of venus via a minnaert scattering model in low latitudes the average zonal component is slowest at about 10 40 am local solar time while the maximum poleward flow occurs at noon at most latitudes the cloud motions are divergent with the maximum horizontal divergence 5 10 6 sec 1 occurring in equatorial latitudes just past noon and become convergent at about 30 morning to 40 afternoon lat on both sides of the equator the lowest ultraviolet reflectivity is found near the equator at local noon peak reflectivity is found in broad tilted with respect to latitude circles bands near 45 lat in the north and south hemispheres an apparent relationship between the horizontal divergence and ultraviolet is indicated such that the highest reflectivities are found in regions of convergence in high latitudes and lower values where the motions are divergent in equatorial latitudes in solar locked coordinates the root mean square deviation of the normalized ultraviolet brightness is not uniformly distributed about the subsolar point but tends to be higher around 45 lat than in equatorial regions and over periods of about 2 weeks shows substantial small scale structure as well

images from galileo of the venus cloud deck images of venus taken at 418 violet and 986 near infrared nir nanometers show that the morphology and motions of large scale features change with depth in the cloud deck poleward meridional velocities seen in both spectral regions are much reduced in the nir in the south polar region the markings in the two wavelength bands are strongly anticorrelated the images follow the changing state of the upper cloud layer downwind of the subsolar point and the zonal flow field shows a longitudinal periodicity that may be coupled to the formation of large scale planetary waves no optical lightning was detected

mineralogy and u pb pb pb and sm nd geochronology of the key lake uranium deposit athabasca basin saskatchewan canada the key lake deposit is one of several large high grade unconformity related uranium deposits located at the eastern margin of the athabasca basin in northern saskatchewan canada the deposit consists of the gaertner orebody now mined out and the deilmann orebody which is presently being mined in the past radiometric dating efforts yielded an age of oldest ore forming event of 1250 34 ma at the gaertner orebody and 1350 4 ma at the deilmann orebody this unlikely age difference called for further investigation innovative preparation techniques were used to separate the paragenetically oldest u mineral an anisotropic uraninite ore microscopy and u pb isotopic data show that the oldest event of uranium emplacement occurred simultaneously at the two orebodies at 1421 49 ma the primary ore forming phase was followed by younger generations of u mineralization and periods of remobilization sm nd data of key lake uraninite form an isochron corresponding to an age of 1215 ma this is interpret

global changes in intensity of the earth s magnetic field during the past 800kyr recent advances in palaeomagnetic and dating techniques have led to increasingly precise records of the relative intensity of the earth s past magnetic field at numerous field sites the compilation and analysis of these records can provide important constraints on changes in global magnetic field intensity and therefore on the earth s geodynamo itself a previous compilation for the past 200 kyr integrated 17 marine records into a composite curve1 with the geomagnetic origin of the signal supported by an independent analysis of 10be production made on different cores2 the persistence of long term features in the earth s magnetic intensity or the existence of long term periodic changes cannot however be resolved in this relatively short time span here we present the integration of 33 records of relative palaeointensity3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 into a composite curve spanning the past 800 kyr we find that the intensity of the earth s dipole field has experienced large amplitude variations over this time period with pronounced intensity minima coinciding with known excursions in field direction reflecting the emergence of non dipole components no stable periodicity was found in our composite record and therefore our data set does not support the hypothesis that the earth s orbital parameters have a direct and strong influence on the geodynamo

an overview of venus geology the magellan spacecraft is producing comprehensive image and altimetry data for the planet venus initial geologic mapping of the planet reveals a surface dominated by volcanic plains and characterized by extensive volcanism and tectonic deformation geologic and geomorphologic units include plains terrains tectonic terrains and surficial material units understanding the origin of these units and the relation between them is an ongoing task of the magellan team

venus cloud level circulation during 1982 as determined from pioneer cloud photopolarimeter images i time and zonally averaged circulation abstract new measurements of cloud motions on venus during 1982 reveal significant changes in the mean cloud level circulation compared to that seen during 1974 s s limaye and v e suomi 1981 j atmos sci 38 1220 1235 as well as 1979 s s rossow a d del genio s s limaye l d travis and p h stone 1980 j geophys res 85 8107 8128 s s limaye c j grund and s p burre 1982 icarus 51 416 439 in order to establish the validity of these changes two individuals measured cloud motions independently in nearly identical sets of images the results of these independent estimates for 1982 are in remarkable agreement for not only the average zonal and meridional components but also for the measured meridional transport of momentum by the eddy circulation unlike the results for 1979 the latitudinal profile of the time and longitudinally averaged zonal component of the cloud motions for 1982 shows pronounced jets near 45 north and south lat while the average zonal component near the equator is weaker than by more than 10 msec 1 the time and longitudinally averaged meridional component is found to be slightly greater than that during 1979 at all measured latitudes the estimated poleward transports of angular momentum by the mean and eddy circulation are qualitatively similar to those estimated from 1979 measurements with the eddy transport being of the same sign as that of the mean circulation an accompanying paper presents the structure seen in the observed motions seen in a solar locked longitude latitude system interpreted to be the signature of the solar thermal tides s s limaye 1988 icarus 73 212 226

classification of wind streaks on mars abstract a classification of martian wind streaks has been developed to assist in investigations of eolian transport and related meteorological phenomena on mars streaks can be grouped by their albedo contrast with their surroundings and by the presence of either topographic obstacles or sediment deposits at their points of origin the vast majority of wind streaks can be included in three categories 1 bright streaks with no source deposit interpreted to be formed by preferential deposition of dust from suspension 2 dark streaks with no source deposit interpreted to be formed by preferential erosion of bright dust and its removal in suspension 3 dark streaks associated with deposits of sediment interpreted to be formed by deposition of dark material moved by saltation the orientations of the different streak types are distinctive and reflect both global flow patterns and slope controlled winds the wind directions derived from streaks and the geographical distribution of the features show a strong north south asymmetry consistent with the fact that perihelion and hence maximum wind activity occurs near southern summer solstice

deep sea magnetic vector anomalies over the hakurei hydrothermal field and the bayonnaise knoll caldera izu ogasawara arc japan 1 we conducted deep sea magnetic measurements using autonomous underwater vehicles in the bayonnaise knoll caldera the izu ogasawara island arc which hosts the large hakurei hydrothermal field we improved the conventional correction method applied for removing the effect of vehicle magnetization thus greatly enhancing the precision of the resulting vector anomalies the magnetization distribution obtained from the vector anomaly data shows a 2 km wide belt of high magnetization trending nnw sse going through the caldera and a low magnetization zone 300 m by 500 m in area extending over the hakurei site comparison between the results obtained using the vector anomaly and the total intensity anomaly shows that the magnetic field is determined more accurately especially in areas of sparse data distribution when the vector anomaly rather than the total intensity anomaly is used we suggest a geologically motivated model that basaltic volcanism associated with the back arc rifting occurred after the formation of the caldera resulting in the formation of the high magnetization belt underneath the silicic caldera the hakurei hydrothermal field lies in the intersection of the basaltic volcanism belt and the caldera wall fault suggesting a mechanism that hot water generated by the heat of the volcanic activity has been spouting out through the caldera wall fault the deposit apparently extends beyond the low magnetization zone climbing up the caldera wall this may indicate that hot water rising from the deep through the alteration zone is transported laterally when it comes near the seafloor along fissures and fractures in the caldera wall

wind streaks on venus clues to atmospheric circulation magellan images reveal surface features on venus attributed to wind processes sand dunes wind sculpted hills and more than 5830 wind streaks have been identified the streaks serve as local wind vanes representing wind direction at the time of streak formation and allowing the first global mapping of near surface wind patterns on venus wind streaks are oriented both toward the equator and toward the west when streaks associated with local transient events such as impact cratering are deleted the westward component is mostly lost but the equatorward component remains this pattern is consistent with a hadley circulation of the lower atmosphere

is the mean venusian tropospheric circulation unsteady 1 the troposphere of venus or that region between the surface and the sulphuric acid cloud layer is characterised by very low horizontal temperature contrasts of less than 10 k such low thermal gradients will have a large impact on the tropospheric mean circulation using a simplified atmospheric model we show that the mean circulation might change in strength and possibly even reverse in direction on timescales of decades to centuries the phenomenon is associated with the high surface pressure and hence long thermal relaxation time scale of the lower atmosphere inertial oscillations appear to play a role in any circulation reversals that occur we note that wind streak data are consistent with a variable hadley circulation our results imply that the venusian cloud layer could also exhibit significant variability on the same very long timescales consistent with some observations

earth aeolian wind streaks comparison to wind data from model and stations wind streak is a collective term for a variety of aeolian features that display distinctive albedo surface patterns wind streaks have been used to map near surface winds and to estimate atmospheric circulation patterns on mars and venus however because wind streaks have been studied mostly on mars and venus much of the knowledge regarding the mechanism and time frame of their formation and their relationship to the atmospheric circulation cannot be verified this study aims to validate previous studies results by a comparison of real and modeled wind data with wind streak orientations as measured from remote sensing images orientations of earth wind streaks were statistically correlated to resultant drift direction rdd values calculated from reanalysis and wind data from 621 weather stations the results showed good agreement between wind streak orientations and reanalysis rdd r 0 78 a moderate correlation was found between the wind streak orientations and the weather station data r 0 47 a similar trend was revealed on a regional scale when the analysis was performed by continent with r ranging from 0 641 in north america to 0 922 in antarctica at sites where wind streak orientations did not correspond to the rdds i e a difference of 45 seasonal and diurnal variations in the wind flow were found to be responsible for deviation from the global pattern the study thus confirms that earth wind streaks were formed by the present wind regime and they are indeed indicative of the long term prevailing wind direction on global and regional scales

ground based near infrared imaging observations of venus during the galileo encounter near infrared images of venus obtained from a global network of ground based observatories during january and february 1990 document the morphology and motions of the night side near infrared markings before during and after the galileo venus encounter a dark cloud extended halfway around the planet at low latitudes 40 and persisted throughout the observing program it had a rotation period of 5 5 0 15 days the remainder of this latitude band was characterized by small scale 400 to 1000 kilometers dark and bright markings with rotation periods of 7 4 1 days the different rotation periods for the large dark cloud and the smaller markings suggests that they are produced at different altitudes mid latitudes 40 to 60 were usually occupied by bright east west bands the highest observable latitudes 60 to 70 were always dark and featureless indicating greater cloud opacity maps of the water vapor distribution show no evidence for large horizontal gradients in the lower atmosphere of venus

a reduced crustal magnetization zone near the first observed active hydrothermal vent field on the southwest indian ridge 1 inversion of near bottom magnetic data reveals a well defined low crustal magnetization zone lmz near a local topographic high 37 47 s 49 39 e on the ultraslow spreading southwest indian ridge swir the magnetic data were collected by the autonomous underwater vehicle abe on board r v dayangyihao in february march 2007 the first active hydrothermal vent field observed on the swir is located in area a within and adjacent to the lmz at the local topographic high implying that this lmz may be the result of hydrothermal alteration of magnetic minerals the maximum reduction in crustal magnetization is 3 a m the spatial extent of the lmz is estimated to be at least 6 7 104 m2 which is larger than that of the lmzs at the tag vent field on the mid atlantic ridge mar as well as the relict field bastille dante grotto and new field vent sites on the juan de fuca ridge jdf the calculated magnetic moment i e the product of the spatial extent and amplitude of crustal magnetization reduction is at least 3 107 am2 for the lmz on the swir while that for the tag field on the mar is 8 107 am2 and that for the four individual vent fields on the jdf range from 5 107 to 3 107 am2 together these results indicate that crustal demagnetization is a common feature of basalt hosted hydrothermal vent fields at mid ocean ridges of all spreading rates furthermore the crustal demagnetization of the area a on the ultraslow spreading swir is comparable in strength to that of the tag area on the slow spreading mar

the permeability of clay suspensions the chemical engineering literature abounds with empirical and theoretical equations relating the sedimentation and fluidization velocities of a given solid liquid system and its porosity a geotechnical approach shows that for active clay particles the problem lies in the definition and associated determination of a coefficient of permeability of the system a fluidization test is proposed to provide a direct permeability measurement of clay suspensions the experimental results obtained on two clay mixtures indicate that the coefficient of permeability varies continuously over a wide range of porosities encompassing soil conditions and suspended conditions and that a two constant power equation can be usefully employed to represent such variation les textes de genie chimique abondent en equations empiriques et theoriques qui experiment les vitesses de sedimentation et de fluidisation d un systeme solide liquide donne et sa porosite une approche geotechnique montre que pour des particules actives

shuttle radar images of wind streaks in the altiplano bolivia shuttle imaging radar sir a coverage across bolivia shows the major physiographic provinces including the andean altiplano the altiplano contains a variety of eolian features many of which are visible as radar dark radar mottled and radar bright streaks aligned parallel to the prevailing winds the streaks form downwind from hills and are as much as 15 km long and 800 m wide dark streaks originate between closely spaced hills whereas bright streaks form in the immediate lee of hills the radar brightness of the streaks is modulated by the proportion of sand cover vegetation and exposed substrate all of which relate to the local wind regime in the radar dark streaks vegetation is sparse and the sand is organized into dune forms some of which can be recognized as barchan dunes on the radar image by outlining of the dark dune by bright substrate radar mottled zones are covered by numerous 0 5 2 m high coppice dunes and in radarbright streaks the sand forms flat sheets but also includes sand mounds and abundant vegetation measurements indicate that winds are strongest and most turbulent in the region of active sand sheets and dunes inhibiting the growth of vegetation and the formation of mounds and resulting in a radar dark zone these results are consistent with previous studies that have demonstrated the existence of turbulent eddies in the wake of topographic obstacles that produce zones of increased surface wind shear and enhanced sand mobility the relation between the radar signature and the wind regime allows inferences to be drawn for the wind regime from image interpretation

depositional characteristics of uranium tailings from saskatchewan canada the management of uranium tailings generated as a by product of ore processing is particularly important to minimize the environmental footprint of the industry a clear understanding of tailings slurry behavior is required at the time of deposition to help evaluate the storage capacity and life span of the containment facilities the main purpose of this study was to investigate the segregation and self weight settling properties of uranium tailings detailed laboratory investigations were conducted on tailings from 4 5 and 6 nominal mill feeds high grade mcarthur river ores blended with special wastes on site from the cameco key lake operation the results indicate that the three uranium tailings can be characterized as a sandy silt material with a negligible amount of clay their depositional behavior is governed by the initial solids content of the slurry the investigated tailings showed insignificant segregation between 25 and 40 initial solids content the initial hydraulic conductivity during settling was about 10 4 m s at a void ratio of 4 and was increased by half an order of magnitude for the 4 mill feed and by almost two orders of magnitude for the 5 and 6 mill feeds at a void ratio of 8 over the same range of initial void ratio the settling potential increased threefold from 8 to 24 for the 4 mill feed and from 12 to 36 for the 5 and 6 mill feeds the better rate and amount of dewatering of future high mill feed tailings as compared to the current low mill feed tailings means that the onsite containment facility can store more tailings thereby supporting a longer life span of the mill

space shuttle observations of terrestrial impact structures using sir c and x sar radars ten terrestrial impact structures were imaged during two flights of the 1994 space radar laboratory srl experiment these craters include wolf creek australia roter kamm namibia zhamanshin kazakhstan b p and oasis libya aorounga chad amguid algeria and spider connolly basin and henbury australia srl contained two co registered instruments the united states sir c polarimetric radar system operating in l band 24 cm and c band 5 6 cm and the joint german italian x sar vertically polarized radar operating in x band 3 cm comparisons show srl images to be complementary to or in some cases superior to corresponding optical images for evaluating size location and relative age of impact features regardless of wavelength or polarization craters with significant relief appear prominently on radar as a result of slope and roughness effects in desert regions longer wavelengths penetrate dry sand mantles to reveal hidden crater dimensions or associated buried landforms radar polarities and wavelengths are particularly sensitive to vegetation surface roughness and soil moisture or electrical properties in the more temperate environments of kazakhstan and australia srl images show detailed stream patterns that reveal the location and structure of otherwise obscured impact features

large scale patterns of eolian sediment transport on venus predictions for magellan the atmosphere of venus is likely to exert a major influence on the surface arecibo and venera 15 16 observations of the population of impact craters with bright halos give direct evidence of surface modification on the scale of centimeters to smooth the surface on time scales of 50 250 my both chemical and mechanical modifications probably occur diurnal winds in the planetary boundary layer can transport particles using boundary layer theory including the effects of topography surface stresses and resulting transport and deposition of sand size particles are calculated regional slopes are sites of largest surface stresses sand will be generally transported downhill although there is a preferential net transport from east to west in the same direction as the atmospheric superrotation it is predicted here that streaks may be seen in the magellan radar images which will indicate directions of net eolian transport on the surface of venus

planetary boundary layer and slope winds on venus few constraints are available to characterize the deep atmosphere of venus though this region is crucial to understand the interactions between surface and atmosphere on venus based on simulations performed with the ipsl venus global climate model the possible structure and characteristics of venus planetary boundary layer pbl are investigated the vertical profile of the potential temperature in the deepest 10 km above the surface and its diurnal variations are controlled by radiative and dynamical processes the model predicts a diurnal cycle for the pbl activity with a stable nocturnal pbl while convective activity develops during daytime the diurnal convective pbl is strongly correlated with surface solar flux and is maximum around noon and in low latitude regions it typically reaches less than 2 km above the surface but its vertical extension is much higher over high elevations and more precisely over the western flanks of elevated terrains this correlation is explained by the impact of surface winds which undergo a diurnal cycle with downward katabatic winds at night and upward anabatic winds during the day along the slopes of high elevation terrains the convergence of these daytime anabatic winds induces upward vertical winds that are responsible for the correlation between height of the convective boundary layer and topography

implications of the vega balloon results for venus atmospheric dynamics both vega balloons encountered vertical winds with typical velocities of 1 to 2 meters per second these values are consistent with those estimated from mixing length theory of thermal convection however small scale temperature fluctuations for each balloon were sometimes larger than predicted the approximate 6 5 kelvin difference in temperature consistently seen between vega 1 and vega 2 is probably due to synoptic or planetary scale nonaxisymmetric disturbances that propagate westward with respect to the planet there is also evidence from doppler data for the existence of solar fixed nonaxisymmetric motions that may be thermal tides surface topography may influence atmospheric motions experienced by the vega 2 balloon

origin of magnetic highs at ultramafic hosted hydrothermal systems insights from the yokoniwa site of central indian ridge high resolution vector magnetic measurements were performed on an inactive ultramafic hosted hydrothermal vent field called yokoniwa hydrothermal field yhf using a deep sea manned submersible shinkai6500 and an autonomous underwater vehicle r2d4 the yhf has developed at a non transform offset massif of the central indian ridge dead chimneys were widely observed around the yhf along with a very weak venting of low temperature fluids so that hydrothermal activity of the yhf was almost finished the distribution of crustal magnetization from the magnetic anomaly revealed that the yhf is associated with enhanced magnetization as seen at the ultramafic hosted rainbow and ashadze 1 hydrothermal sites of the mid atlantic ridge the results of rock magnetic analysis on seafloor rock samples including basalt dolerite gabbro serpentinized peridotite and hydrothermal sulfide showed that only highly serpentinized peridotite carries high magnetic susceptibility and that the natural remanent magnetization intensity can explain the high magnetization of yokoniwa these observations reflect abundant and strongly magnetized magnetite grains within the highly serpentinized peridotite comparisons with the rainbow and ashadze 1 suggest that in ultramafic hosted hydrothermal systems strongly magnetized magnetite and pyrrhotite form during the progression of hydrothermal alteration of peridotite after the completion of serpentinization and production of hydrogen pyrrhotites convert into pyrite or nonmagnetic iron sulfides which considerably reduces their levels of magnetization our results revealed origins of the magnetic high and the development of subsurface chemical processes in ultramafic hosted hydrothermal systems furthermore the results highlight the use of near seafloor magnetic field measurements as a powerful tool for detecting and characterizing seafloor hydrothermal systems

expansive characteristics of gypsiferous anhydritic soil formations abstract geology and climatic and environmental conditions have led to the formation of expansive soils in the eastern province of saudi arabia calcium sulphate which commonly occurs in such soils is well known for phase transformation and dissolution phase changes from gypsum to anhydrite and vice versa and dissolution of these phases add to the potential hazards of local expansive soils this paper discusses the behaviour of the expansive soil formations of eastern saudi arabia containing gypsum and anhydrite

magnetic structure of an oceanic core complex at the southernmost central indian ridge analysis of shipboard and deep sea three component magnetometer data 1 we investigated the magnetic structure of an oceanic core complex occ at the southernmost central indian ridge cir near 25 s on the basis of newly collected magnetic and bathymetric data and submersible dives the occ is located off axis on the western flank of the cir and is characterized by typical megamullion morphology with flow line parallel corrugations the occ is similar in size to those found along the mid atlantic ridge mar but the cir occ formed in an estimated 0 8 ma which is slightly shorter than the average time for the formation of occs along the mar the magnetization intensity over the cir occ is quite weak compared to that over adjacent seafloor of the same age mostly gabbroic rocks were recovered from outcrops during submersible dives fault rocks were also recovered from the corrugated surface suggesting that the occ surface represents the plane of a detachment fault although the magnetization intensity is rather low we were able to identify the brunhes matuyama boundary and the jaramillo and olduvai subchrons on and around the occ using vector magnetic analysis over the occ the jaramillo subchron which cannot be recognized from magnetic data acquired at the sea surface was identified using data from a magnetometer attached to a submersible the locus of this subchron is consistent with that observed over the seafloor adjacent to the occ combining the results of magnetic survey and rock sampling we would like to point out the possibility that the gabbroic rocks constituted the occ and preserved seafloor spreading history although there are several interpretations of the low magnetization

galileo infrared imaging spectroscopy measurements at venus during the 1990 galileo venus flyby the near infaied mapping spectrometer investigated the night side atmosphere of venus in the spectral range 0 7 to 5 2 micrometers multispectral images at high spatial resolution indicate substanmial cloud opacity variations in the lower cloud levels centered at 50 kilometers altitude zonal and meridional winds were derived for this level and are consistent with motion of the upper branch of a hadley cell northern and southern hemisphere clouds appear to be markedly different spectral profiles were used to derive lower atmosphere abundances of water vapor and other species

comparison of remote sensing observations of planetary wind streaks abstract wind streaks are common aeolian features observed on terrestrial planets they were first identified on mars thus the associated terminology is based on mars related observations usually describing surface patterns with distinct albedos however terms related to reflected tones are only relevant to past knowledge for mars and not necessarily suitable for description of radar visible streaks located on venus titan or earth furthermore the sensor type used to observe wind streaks can influence the subsequent data analysis the purpose of this study was to examine the effects of sensor type on wind streak identification and interpretation six case studies featuring wind streaks on earth were performed using imaging by both radar and optical sensors the results indicate that wind streak identification is constrained to a specific combination of sensor settings appropriate for the local surface properties only half the optically visible wind streaks considered in this study were also radar visible but all the wind streaks observable in the radar images also appeared in the optical images furthermore bright and dark reflectance and backscatter are relative terms and should be used with caution these results suggest that the venusian wind streak database is most likely far from complete and that many more streaks exist