dactyl galileo observations of ida s satellite abstract galileo s flyby of 243 ida in august 1993 led to the discovery of a small satellite dactyl some 85 km from the asteroid s center from earth at mean opposition the satellite is a v 20 3 mag object some 6 7 magnitudes fainter than ida forty seven images of the satellite at 18 different observing times were played back including one multicolor sequence in which the satellite is resolved adequately to distinguish surface markings 105 m pxl and three higher resolution single color views 89 39 and 24 m pxl the satellite mean radius 0 7 km is an elongated but not angular body with principal diameters of 1 6 1 4 1 2 km in the highest resolution view the longest axis points approximately in the direction of ida and its shortest axis is perpendicular to the orbital plane the spin period is slow 8 hr and may be synchronous the satellite shows no conspicuous sharp edges and is much less irregular in shape than ida limb profiles are remarkably smooth over distances of 200 300 m the geometric albedos of the two objects are similar 0 20 vs 0 21 as are the 0 4 1 0 m colors like ida dactyl is an s asteroid but has a slightly deeper 1 m band than ida by 5 8 while no identical regions in color are seen on ida the color difference is consistent with color variations reported within the koronis family and may be due to a slightly higher pyroxene olivine ratio on the satellite more than a dozen craters ranging from 90 to 280 m diameter are visible in the best image 39 m pxl at 47 phase the largest contains an off centered positive relief feature some 75 m across the image includes an intriguing crater chain but no grooves ridges or sharp edges are evident in terms of limb roughness dactyl is much smoother than ida but comparable to the two satellites of mars phobos and deimos while the satellite s origin is uncertain a likely scenario would have the satellite date from the breakup of the koronis family it is interesting that crater densities on the satellite are similar to those on ida itself

geochemical effects of co2 sequestration in sandstones under simulated in situ conditions of deep saline aquifers abstract the geochemical effects of brine and supercritical co 2 scco 2 on reservoir rocks from deep 1500 2000 m saline aquifers were examined via experimental simulation at in situ conditions dry sandstone samples were mounted in a triaxial cell and autoclave system evacuated and saturated with 1 m nacl solution the brine rock system was allowed to react at 30 mpa confining pressure 15 mpa pore fluid pressure and 60 c while scco 2 was injected at a pressure gradient of 1 2 mpa the experiment was conducted for a period of 1496 h during which fluids were periodically sampled and analyzed the ph measured in partially degassed fluid samples at 25 c decreased from a starting value of 7 0 4 3 9 days and finally 5 1 after saturation with scco 2 fluid analyses indicate that most of the major e g ca mg fe mn and trace elements e g sr ba pb of the sandstone increase in concentration during the reaction with brine and scco 2 these results are supported by scanning electron microscopy which indicates dissolution of dolomite cement k feldspar and albite in addition to dissolution reactions the formation of montmorillonite was observed by adjusting surface area and reaction rates of dissolution and precipitation geochemical modeling of the experiments could reproduce long term trends in solution chemistry and indicated limited rates of dissolution as the system remained strongly undersaturated with most minerals including carbonates the geochemical models could not account for decreases in concentration of some elements changes in solution composition resulting from changes in imposed pressure gradient and the observed ca mg and si al ratios in solution

cassini imaging science initial results on phoebe and iapetus the cassini imaging science subsystem acquired high resolution imaging data on the outer saturnian moon phoebe during cassini s close flyby on 11 june 2004 and on iapetus during a flyby on 31 december 2004 phoebe has a heavily cratered and ancient surface shows evidence of ice near the surface has distinct layering of different materials and has a mean density that is indicative of an ice rock mixture iapetus s dark leading side cassini regio is ancient heavily cratered terrain bisected by an equatorial ridge system that reaches 20 kilometers relief local albedo variations within and bordering cassini regio suggest mass wasting of ballistically deposited material the origin of which remains unknown

block distributions on itokawa abstract asteroid 25143 itokawa is a small elongated asteroid with two distinct parts the evolution of this two part body has been the source of speculation the scenarios for the formation of this asteroid include two body capture catastrophic disruption and rapid reaccretion yorp spin up and mass shedding and disruption or partial disruption with two body reaccretion in this paper we use the global and regional analyses of block populations and size frequency distributions as evidence of the probable evolutionary history of itokawa the block sample used in this study is believed to be complete for blocks of size 6 m and consists of a sample more than twice as large as previous known studies although block size frequency distributions hint at different evolutionary paths for the head and the body their differences are not statistically significant the distribution of blocks across each body provides clues as to the histories of each body the head is populated in a spherically symmetric fashion while the body has a distinct equatorial peak when considering that the head and the body may have been separate entities for a period of time and estimating a rotational axis using minimum rotational energy considerations the preferential equatorial distribution becomes even more pronounced we interpret this as excellent evidence for the partial disruption of a proto itokawa subsequent planarization of a debris field and reaccretion of the head and the body into its present configuration

s type asteroids ordinary chondrites and space weathering the evidence from galileo s fly bys of gaspra and ida new observations of the s type asteroids gaspra and ida especially by the galileo spacecraft demonstrate that a space weathering process operates which modifies the reflectance spectra of fresh material to be redder straighter and have shallower absorption bands the weathering process appears similar to but less potent than that observed on the moon it operates in the sense that it would tend to convert spectra of ordinary chondrites oc to having the spectral traits of s type asteroids these results appear to resolve the major obstacles of the long standing s type conundrum about the provenance of ordinary chondrite meteorites a wide body of recent research which is reviewed here builds on previous meteoritical evidence to support a new developing consensus that the larger s type asteroids are a diverse assortment of silicaceous assemblages which includes the ordinary chrondite parent bodies recent fairly realistic laboratory simulations of space weathering processes have changed oc spectra to resemble s type spectra j f bell s highly regarded earlier paradigm that oc parent bodies would be found only among sub 10 km main belt asteroids has been tested by an extensive observational survey by r binzel and his proteges the result is that no small main belt analog for the ocs has been found not even the somewhat oc like object boznemcova this article reviews the history of the s type conundrum which set the stage for galileo s historic flybys i review the findings about gaspra and ida including results about their geology their geophysical structure and probable origins and about ida s small moonlet dactyl density constraints on ida set by dactyl s orbit rule out for ida at least the classic view of s types as metallic stripped cores of differentiated precursor asteroids new analysis of the galileo spectral images of ida is presented that provides strong evidence that space weathering occurs on ida and that ida and the koronis family asteroids in general are plausibly oc like in composition after reviewing 1990s developments on the s type conundrum i advocate a new perspective that the ordinary chondrite parent bodies are among the s type asteroids a diverse grouping that also contains other silicaceous and silicate metal assemblages presumably including various stony irons and primitive achondrites represented in meteorite collections gaspra may be such a metal rich assemblage

reservoir characterization of a co2 storage aquifer the upper triassic stuttgart formation in the northeast german basin abstract ketzin in the northeast german basin negb is the site for pilot injection of co 2 co 2 sink project into a saline aquifer the upper triassic stuttgart formation situated at a depth of about 630 700 m this paper reports the baseline characterization of the reservoir formation based on new core material and well logs obtained from one injection well and two observations wells drilled at a distance from 50 m to 100 m from each other the reservoir is lithologically heterogeneous and made up by fluvial sandstones and siltstones interbedded with mudstones showing remarkable differences in porosity the thickest sandstone units are associated with channel sandstone whose thickness varies over short lateral distances in depth petrographic mineralogical mineral chemical and whole rock geochemical analysis were performed focusing on the sandstone intervals which display the best reservoir properties for co 2 injection the dominantly fine grained and well to moderately well sorted immature sandstones classify as feldspathic litharenites and lithic arkoses quartz 22 43 wt plagioclase 19 32 wt and k feldspar 5 13 wt predominate mineralogically muscovite plus illite and mixed layer minerals are omnipresent 4 13 wt quartz feldspar as well as meta sedimentary and volcanic rock fragments comprise the most abundant detrital components which often are rimmed by thin early diagenetic coatings of ferric oxides and locally of clay minerals feldspar grains may be unaltered and optically clear partially to completely dissolved partially altered to sheet silicates mainly illite or albitized analcime and anhydrite constitute the most widespread often spatially associated pore filling cement minerals authigenic dolomite barite and coelestine is minor the percentage of cements ranges in total from about 5 vol to 32 vol except of samples intensely cemented by anhydrite and analcime total porosities of the sandstones range from 13 to 26 the fraction of intergranular porosity varies between 12 and 21 about 1 5 porosity has been generated by dissolution of detrital plagioclase k feldspar and volcanic rock fragments the comparatively large modal abundance of feldspars micas chlorite clay minerals fe ti oxides and analcime account for the richness in ti al fe mg na and k and the paucity in si of the stuttgart sandstones relative to mature sandstones altogether these sandstones are comparatively rich in minerals that may potentially react with the injected co 2

knob heights within circum caloris geologic units on mercury interpretations of the geologic history of the region abstract the circum caloris geologic units show morphology consistent with ejecta derived formation however crater counts suggest the units formed after the basin to determine if the surrounding units are directly related to basin formation or products of later volcanic resurfacing events we measured the heights and densities of knobs in 22 study regions to the east of the caloris basin in three geologic units circumferential to the basin the odin formation the van eyck formation and the smooth plains formation in these study regions the size and concentration of ejecta blocks generally decrease away from the crater rim the morphology that superposes the knobs and the distribution of knob heights within each study region suggests that the knobs were deposited as ejecta and later embayed by one or multiple volcanic events the distribution of knob height and concentration indicates that the knobs within the circum caloris units are related to the formation of the basin

monitoring and volumetric estimation of injected co2 using 4d seismic petrophysical data core measurements and well logging a case study at ketzin germany more than 50 000 tons of co2 have been injected at ketzin into the stuttgart formation a saline aquifer at approximately 620 m depth as of summer 2011 we present here results from the 1 st repeat 3d seismic survey that was performed at the site in autumn 2009 after about 22 000 tons of co2 had been injected we show here that rather complex time lapse signatures of this co2 can be clearly observed within a radius of about 300 m from the injection well the highly irregular amplitude response within this radius is attributed to the heterogeneity of the injection reservoir time delays to a reflection below the injection level are also observed petrophysical measurements on core samples and geophysical logging of co2 saturation levels allow an estimate of the total amount of co2 visible in the seismic data to be made these estimates are somewhat lower than the actual amount of co2 injected at the time of the survey and they are dependent upon the choice of a number of parameters in spite of some uncertainty the close agreement between the amount injected and the amount observed is encouraging for quantitative monitoring of a co2 storage site using seismic methods

fluid injection monitoring using electrical resistivity tomography five years of co2 injection at ketzin germany between the years 2008 and 2013 approximately 67 kilotons of co2 have been injected at the ketzin site germany as part of the geophysical monitoring programme time lapse electrical resistivity tomography has been applied using crosshole and surface downhole measurements of electrical resistivity tomography the data collection of electrical resistivity tomography is partly based on electrodes that are permanently installed in three wells at the site one injection well and two observation wells both types of ert measurements consistently show the build up of a co2 related resistivity signature near the injection point based on the imaged resistivity changes and a petrophysical model co2 saturation levels are estimated these co2 saturations are interpreted in conjunction with co2 saturations inferred from neutron gamma loggings apart from the co2 brine substitution response in the observed resistivity changes significant imprints from the dynamic behaviour of the co2 in the reservoir are observed

disseminated phosphorus in oceanic sediments a review abstract the content of disseminated phosphorus in sediments of the world oceans fluctuates between 0 01 and 4 36 terrigenous and hemipelagic sediments contain on average about 0 07 phosphorus higher concentrations are characteristic of sediments enriched in iron and manganese hydroxides or bone detritus and phosphoritic material the general features of the phosphorus distribution in surface sediments depend on the ratio of continental runoff area to basin area which diminishes from the atlantic to the indian and pacific areas the relative extent of the nearshore phosphorus rich zone contracts whereas that of the pelagic phosphorus rich zone widens in the transition from the atlantic through the indian to the pacific areas the distribution of phosphorus in vertical sections of sediments gives some evidence of the diagenetic mobilisation of phosphorus and its partial loss to bottom water the rate of phosphorus accumulation in oceanic sediments is evaluated as between 10 g cm 2 k y 1 the bulk mass of phosphorus is accumulated in marginal zones of the oceans

geochemical and geomechanical effects of scco2 and associated impurities on physical and petrophysical properties of permotriassic sandstones germany an experimental approach effects of impurities sox nox and o2 from the extraction processes of the power plants in the scco2 fluids are studied with an experimental approach combining geochemical alteration in high p medium t autoclaves compressional tests in a heated triaxial testing device as well as geochemical and mineralogical analyses before and after the influences of distinct scco2 fluids on 140 70 mm sized samples of reservoir sandstones from the north german basin with carbonate cementation silicate cementation and a combined silicate carbonate cementation on the background of variable lithological compositions the attempt was made to normalize the scattering geomechanical data by the pure co2 behavior measurement data to achieve a direct impression of any differences due to the impurities changes in the chemical composition of the saline fluids were systematically measured during the scco2 alteration experiments in the autoclave systems at distinct pt conditions the development of the silica concentrations and of the ph value in the fluid solution during alteration showed a clear dependency on the fluid composition through systematical analysis of changes on the mineral surfaces using sem microscopy images before and after scco2 impurities alteration experiments or triaxial compression tests corrosion effects were detected but no differences which could be directly related to differences in the fluid composition could be identified in all the types of sandstones visible or measurable changes on mineral surfaces and pore fluid composition respectively take place as an interaction of rock with fluids of scco2 with and without impurities changing deformability and compressive strength of the rocks are the most apparent consequences due to these compositional changes it is supposed that the chemical fluid differences are responsible for these changes also a specific distribution of the different fluids in the ambient pore space is indicated with even undetected consequences for the fluid influence on stress transmission and distribution within the grain structure all work was performed within the project co2 purity for capture and storage cooral supported by the german federal ministry for economic affairs and energy

surface lithologic heterogeneity of asteroid 4 vesta abstract high precision spectrophotometry of 4 vesta the third largest asteroid was used to establish the surface composition of this body and to investigate mineralogical variations across its surface the average surface of vesta is analogous to howardite and or polymict eucrite assemblages regolith derived members of the hed meteorite suite which consist of a eucrite matrix containing differing amounts of a diogenite component color and or spectral changes which exhibit a consistent relationship to rotational phasing are evident in 16 of 18 studies of vesta dating back to 1929 including the present work after elimination of possible sources of spurious spectral or color changes it is concluded that these variations arise from hemispheric variations in surface materials and hence provide a means of spatially resolving subhemispheric compositional units on the surface of vesta the background surface of vesta is a relatively dark howardite or polymict eucrite pyroxene plagioclase assemblage with several compositionally distinct bright regions clustered in one hemisphere viewed around the maximum in vesta s lightcurve these include what appears to be an olivine bearing unit suggested name leslie formation located near vesta s equator which probably represents an impact basin and or its associated ejecta that penetrated through the basaltic crust other high albedo compositional units including an apparently low calcium eucrite region and several diogenite pyroxenite regions at least one located near the southern pole may be smaller shallower impact basins by analogy to the eucrite meteorites which represent surface flows or shallow intrusions and which constitute the major component of the regolith derived howardites and polymict eucrites we conclude that the howardite polymict eucrite units represent a regolith gardened original surface of vesta it is probable that the low albedo of the background surface on vesta is due to an age related darkening effect similar to that inferred from the galileo images of gaspra and ida this mechanism is consistent with the correlation of absorption feature intensity with the lightcurve vesta appears to have an old eucritic surface darkened with age and represented among the meteorites by the regolith derived howardites and polymict eucrites on which several impacts on one hemisphere have exposed fresher brighter diogenite and olivine bearing material based on qualitative analysis of the mineralogical variations as a function of rotation a generalized lithologic map of vesta was produced there is reasonable control on the longitude of lithologic features but little control on their latitudes except where specifically noted in producing this map discrete circular features were used on the plausible assumption that impacts have been the most important geologic process on this surface for most of the age of the solar system the shape of the features has thus been assumed rather than derived and is subject to future revision as data improve

the marine phosphorus cycle phosphorus introduced to the ocean must ultimately be removed if a steady state is to be maintained over geologic time aeolian input is insignificant and there is evidently no hydrothermal contribution rivers dominate p input to the ocean the fluvial p flux is poorly quantified due to the interactions of two factors 1 man s influence on river nutrient fluxes and 2 inherent complexities in understanding the biological and inorganic associations of p in estuarine and coastal waters our best estimate of the natural or pre man p input flux is about 10 x 10 sup 9 moles p cm sup 2 ocean surface year of the identified flux of phosphorus to the sediments about 90 percent is in the form of biogenic debris or its regeneration products the burial of phosphatic fish debris is negligible p removal by direct reaction of phosphate in seawater with sea floor basalts during mid ocean ridge hydrothermal circulation is insignificant p removal by processes such as sorption on clay surfaces or formation of authigenic fe and al phosphate phases is presently unquantified and remains a serious uncertainty in the phosphorus cycle the identified sources and sinks approximately balance yielding a residence time for p in the oceans of about 10 sup 5 yrs

xenoliths and microxenoliths in h chondrites sampling the zodiacal cloud in the asteroid main belt abstract xenoliths are inclusions of a given meteorite group embedded in host meteorites of a different group xenoliths with dimensions between a few m and about 1 mm microxenoliths are meteorite trapped analogues of micrometeorites collected on the earth however they have the unique features of sampling the zodiacal cloud 1 at more ancient times than those sampled by micrometeorites and 2 at larger distances from the sun corresponding to the asteroid main belt than that sampled by micrometeorites 1 au herein we describe a systematic search for new xenoliths and microxenoliths in h chondrites aimed at determining their abundance in these ordinary chondrites analyzing their mineralogy and searching for possible correlations with host meteorite properties sixty six sections from 40 meteorites have been analyzed twenty four new xenoliths have been discovered about 87 of them are microxenoliths i e 1 mm in their largest dimension all the newly discovered xenoliths and microxenoliths are composed of carbonaceous chondritic material hence the zodiacal cloud was dominated by carbonaceous material even in past epochs all the new xenoliths and microxenoliths have been found in regolith breccias hydrous phase rich xenoliths and microxenoliths in h4 and h5 chondrites attest that their embedding happened after the end of the thermal metamorphism all these data suggest that xenoliths and microxenoliths were embedded when their host meteorites were part of the parent body regolith this combined with the h chondrite impact age distribution attests that the embedding may have happened as early as 3 5 gyr ago

evaluation of the impact of co2 co contaminant gas aqueous fluid and reservoir rock interactions on the geologic sequestration of co2 lowering the costs of front end processes e g separation in the geologic sequestration of co2 can dramatically lower the overall costs one possible approach is to sequester less pure co2 waste streams that are less expensive or require less energy to separate from flue gas or a coal gasification process etc the objective of this research is to evaluate the impacts of co2 itself as well as an impure co2 waste stream on geologic sequestration using reaction progress models reactive transport simulators and analogous reactive transport experiments run in a plug flow reactor specifically we are investigating the potential for co injecting the sox nox and h2s present in coal fired waste streams along with the co2 we present here the results of reactive transport simulations made to investigate the long term impact of dissolved co2 h2s and so2 on carbon sequestration in the frio fm tx the results suggest that addition of relatively large amounts of h2s to a co2 injection should not adversely impact injectivity or sequestration compared to the injection of co2 alone the co injection of so2 however could produce significantly different results if conditions are such that so2 can oxidize to sulfate in the long term the simulations suggest that carbonate mineral formation can sequester a significant fraction of the injected carbon through the formation of calcite magnesite and dawsonite

near at eros imaging and spectral results eros is a very elongated 34 kilometers by 11 kilometers by 11 kilometers asteroid most of the surface of which is saturated with craters smaller than 1 kilometer in diameter the largest crater is 5 5 kilometers across but there is a 10 kilometer saddle like depression with attributes of a large degraded crater surface lineations both grooves and ridges are prominent on eros some probably exploit planes of weakness produced by collisions on eros and or its parent body ejecta blocks 30 to 100 meters across are abundant but not uniformly distributed over the surface albedo variations are restricted to the inner walls of certain craters and may be related to downslope movement of regolith on scales of 200 meters to 1 kilometer eros is more bland in terms of color variations than gaspra or ida spectra 800 to 2500 nanometers are consistent with an ordinary chondrite composition for which the measured mean density of 2 67 0 1 grams per cubic centimeter implies internal porosities ranging from about 10 to 30 percent

experimental mineral dissolution in berea sandstone reacted with co2 or so2 co2 in nacl brine under co2 sequestration conditions a comparison of the geochemical changes induced in sandstone by either pure or impure co2 at geological co2 storage conditions was investigated samples of berea sandstone were batch reacted in 1 w v nacl brine saturated with pure co2 or mixed so2 co2 gas for 360 h at 50 degrees c and 10 mpa geochemical analysis of incremental water samples showed increases in the concentrations of elements such as calcium magnesium iron manganese and silicon throughout experiments likely being the products of carbonate and reactive silicate dissolution scanning electron microscope images taken of specific points of interest before and after batch reactions confirmed dissolution of carbonates but showed no reaction for minerals such as k feldspar the magnitude of apparent mineral reaction was higher for the mixed gas so2 co2 brine experiment with geochemical modelling also indicating greater dissolution of reactive silicates such as chlorite and potential precipitation of amorphous silica c 2014 elsevier b v all rights reserved

impact fragmentation of lonar crater india implications for impact cratering processes in basalt impact fragmentation is an energetic process that has affected all planetary bodies to understand its effects in basalt we studied lonar crater which is a rare terrestrial simple impact crater in basalt and analogues to kilometer scale simple craters on mars the lonar ejecta consists of basaltic fragments with sizes ranging from silt to boulder the cumulative size and mass frequency distributions of these fragments show variation of power index for different size ranges suggesting simple and complex fragmentation the general shape of the fragments is compact platy bladed and elongated with an average edge angle of 100 the size distribution of cobble to boulder sized fragments is similar to the fracture spacing distribution in the upper crater wall indicating the provenance of those large fragments its consistency with a theoretical spallation model suggests that the large fragments were ejected from near surface of the target whereas the small fragments from deeper level the petrophysical properties of the ejecta fragments reflect the geophysical heterogeneity in the target basalt that significantly reduced the original size of spall fragments the presence of fe mg phyllosilicates smectites both in the ejecta and wall indicates the role of impact in excavating the phyllosilicates from the interior of basaltic target affected by aqueous alteration the seismic images reveal a thickness variation in the ejecta blanket segregation of boulders fractures and faults in the bedrock beneath the crater rim the fracturing fragmentation and fluvial degradation of lonar crater have important implications for mars

boulder size and shape distributions on asteroid ryugu abstract in 2018 the japanese spacecraft hayabusa2 arrived at the small asteroid ryugu the surface of this c type asteroid is covered with numerous boulders whose size and shape distributions are investigated in this study using a few hundred optical navigation camera onc images with a pixel scale of approximately 0 65 m we focus on boulders greater than 5 m in diameter smaller boulders are also considered using five arbitrarily chosen onc close up images with pixel scales ranging from 0 7 to 6 cm across the entire surface area 2 7 km2 of ryugu nearly 4400 boulders larger than 5 m were identified boulders appear to be uniformly distributed across the entire surface with some slight differences in latitude and longitude at 50 km 2 the number density of boulders larger than 20 m is twice as large as on asteroid itokawa or bennu the apparent shapes of ryugu s boulders resemble laboratory impact fragments with larger boulders being more elongated the ratio of the total volume of boulders larger than 5 m to the total excavated volume of craters larger than 20 m on ryugu can be estimated to be 94 which is comparatively high these observations strongly support the hypothesis that most boulders found on ryugu resulted from the catastrophic disruption of ryugu s larger parent body as described in previous papers watanabe et al 2019 sugita et al 2019 the cumulative size distribution of boulders larger than 5 m has a power index of 2 65 0 05 which is comparatively shallow compared with other asteroids visited by spacecraft for boulders smaller than 4 m the power index is even shallower and ranges from 1 65 0 05 to 2 01 0 06 this particularly shallow power index implies that some boulders are buried in ryugu s regolith based on our observations we suggest that boulders near the equator might have been buried by the migration of finer material and as a result the number density of boulders larger than 5 m in the equatorial region is lower than at higher latitudes

geology of 243 ida abstract the surface of 243 ida is dominated by the effects of impacts no complex crater morphologies are observed a complete range of crater degradation states is present which also reveals optical maturation of the surface darkening and reddening of materials with increasing exposure age regions of bright material associated with the freshest craters might be ballistically emplaced deposits or the result of seismic disturbance of loosely bound surface materials diameter depth ratios for fresh craters on ida are 1 6 5 similar to gaspra results but greater than the 1 5 ratios common on other rocky bodies contributing causes include rim degradation by whole body ringing relatively thin ejecta blankets around crater rims or an extended strength gradient in near surface materials due to low gravitational self packing grooves probably represent expressions in surface debris of reactivated fractures in the deeper interior isolated positive relief features as large as 150 m are probably ejecta blocks related to large impacts evidence for the presence of debris on the surface includes resolved ejecta blocks mass wasting scars contrasts in color and albedo of fresh crater materials and albedo streaks oriented down local slopes color data indicate relatively uniform calcium abundance in pyroxenes and constant pyroxene olivine ratio a large relatively blue unit across the northern polar area is probably related to regolith processes involving ejecta from azzurra rather than representing internal compositional heterogeneity a small number of bluer brighter craters are randomly distributed across the surface unlike on gaspra where these features are concentrated along ridges this implies that debris on ida is less mobile and or consistently thicker than on gaspra estimates of the average depth of mobile materials derived from chute depths 20 60 m grooves 30 m and shallowing of the largest degraded craters 20 50 m minimum 100 m maximum suggest a thickness of potentially mobile materials of 50 m and a typical thickness for the debris layer of 50 100 m

meteoritic and other constraints on the internal structure and impact history of small asteroids studies of the internal structure of asteroids which are crucial for understanding their impact history and for hazard mitigation appear to be in conflict for the s type asteroids eros gaspra and ida spacecraft images and geophysical data show that they are fractured coherent bodies whereas models of catastrophic asteroidal impacts family and satellite formation and studies of asteroid spin rates and other diverse properties of asteroids and planetary craters suggest that such asteroids are gravitationally bound aggregates of rubble these conflicting views may be reconciled if 10 50 km s type asteroids formed as rubble piles but were later consolidated into coherent bodies many meteorites are breccias that testify to a long history of impact fragmentation and consolidation by alteration metamorphism igneous and impact processes ordinary chondrites which are the best analogs for s asteroids are commonly breccias some may have formed in cratering events but many appear to have formed during disruption and reaccretion of their parent asteroids some breccias were lithified during metamorphism and a few were lithified by injected impact melt but most are regolith and fragmental breccias that were lithified by mild or moderate shock like their lunar analogs shock experiments show that porous chondritic powders can be consolidated during mild shock by small amounts of silicate melt that glues grains together and by friction and pressure welding of silicate and metallic fe ni grains we suggest that the same processes that converted impact debris into meteorite breccias also consolidated asteroidal rubble internal voids would be partly filled with regolith by impact induced seismic shaking consolidation of this material beneath large craters would lithify asteroidal rubble to form a more coherent body fractures on ida that were created by antipodal impacts and are concentrated in and near large craters and small positive gravity anomalies associated with the psyche and himeros craters on eros are consistent with this concept spin data suggest that smaller asteroids 0 6 6 km in size are unconsolidated rubble piles c type asteroids which are more porous than s types and their analogs the volatile rich carbonaceous chondrites were probably not lithified by shock

experimental evaluation of the impact of the interactions of co2 so2 brine and reservoir rock on petrophysical properties a case study from the ketzin test site germany the objective of this study is to evaluate the impact of impure co2 on a possible co2 repository here we present experimental data on the simulation of the injection of pure co2 and co2 and cocontaminant so2 into a saline aquifer long term exposure experiments with pure co2 reveal no significant changes in the petrophysical properties electrical resistivity elastic wave velocity and permeability in contrast for the injection of co2 and cocontaminant so2 1 vol we have observed significant and irreversible changes of all monitored physical parameters on the one hand the decrease of p wave velocity and the increase of electrical resistivity indicate a dissolution of some framework material on the other hand the decrease of permeability points to the mobilization and redistribution of fines these data might be relevant for subsequent modeling and estimations about tolerable concentration limits regarding the contaminants of co2 to be stored

combination of seismic reflection and constrained resistivity inversion with an application to 4d imaging of the co2 storage site ketzin germany abstracta combination of seismic and geoelectric processing was studied by means of a structurally constrained inversion approach structural constraints were interpreted from the seismic data and integrated into the geoelectric inversion through a local regularization which allowed inverted resistivities to behave discontinuously across defined boundaries this arranged seismic processing and constrained resistivity inversion in a sequential workflow making the generic assumption that the petrophysical parameters of both methods change across common lithostructural boundaries we evaluated the approach using a numerical example and a real data example from the ketzin co2 pilot storage site germany the latter demonstrated the efficiency of this approach for combining 4d seismic and surface downhole geoelectric data in consistence with the synthetic example the constrained resistivity inversions produced clearer delineated images along the boundary between caprock and reservoir formation near the co

detecting crater ejecta blanket boundaries and constraining source crater regions for boulder tracks and elongated secondary craters on eros abstract we present results of a numerical model of the dynamics of ejecta emplacement on asteroid 433 eros ejecta blocks represent the coarsest fraction of eros regolith and are important readily visible tracer particles for crater ejecta blanket units that may be linked back to specific source craters model results show that the combination of irregular shape and rapid rotation of an asteroid can result in markedly asymmetric ejecta blankets and it follows ejecta block spatial distribution with locally very sharp distinct boundaries we mapped boulder number densities in near shoemaker msi images across a portion of a predicted sharp ejecta blanket boundary associated with the crater valentine and confirm a distinct and real ejecta blanket boundary significant at least at the 3 sigma level using our dynamical model we back track the landing trajectories of three ejecta blocks with associated landing tracks in an effort to constrain potential source regions where those blocks were ejected from eros surface in impact events the observed skip distances of the blocks upon landing on eros surface and the landing speeds and elevation angles derived from our model allow us to estimate the coefficient of restitution e of eros surface for impacts of 10 m scale blocks at approximately 5 m s 1 impact speeds we find mean values of e of approximately 0 09 0 18

fundamentally distinct outcomes of asteroid collisional evolution itokawa and eros 1 the outcomes of asteroid collisional evolution are presently unclear are most asteroids larger than 1 km size gravitational aggregates reaccreted from fragments of a parent body that was collisionally disrupted while much smaller asteroids are collisional shards that were never completely disrupted the 16 km mean diameter s type asteroid 433 eros visited by the near mission has surface geology consistent with being a fractured shard the hayabusa spacecraft visited an s asteroid smaller than 1 km namely 25143 itokawa here we report the first comparative analyses of itokawa and eros geology itokawa lacks a global lineament fabric and its blocks craters and regolith are inconsistent with formation and evolution as a fractured shard unlike eros itokawa is not a scaled down eros but formed by a distinct process of catastrophic disruption and reaccumulation

dynamics of oceanic iron prior to the great oxygenation event abstract we report fe isotope compositions in banded iron formations bif from three cores from the pre goe transvaal supergroup south africa and one core from the pre goe joffre member of the hamersley group australia the low abundances of detrital elements such as al ti sc and v suggest that these bif were deposited in distal positions with respect to precambrian continents while the very low p abundances are incompatible with strong biological productivity at these localities a combination of u pb chronology and cobalt accumulation rates is used to establish a high resolution time scale and deduce chemical fluxes the e folding time of 56 fe variations up stratigraphy is used to determine fe oceanic residence times and fe concentrations as well as the dissolved carbonate content of early proterozoic seas iron oceanic residence times increased from 0 2 to 2 3 ma during the time interval between 2521 and 2394 ma covered by the present cores translating into ocean fe concentrations increasing from 6 4 to 37 mmol kg 1 massive bif precipitation was triggered by release of co2 into the atmosphere and subsequent surges of alkalinity into the ocean due to the weathering of large subaerial volcanic systems we argue that a suitable electron acceptor for fe2 oxidation to magnetite is the inorganic conversion of co2 or dissolved inorganic carbon to ch4 in the process h is produced which is reinjected into oceanic hydrothermal systems liberating fe2 the couple fe2 magnetite may in the archean have played the same buffering role as the couple ca2 calcite plays today massive injection of methane into the atmosphere would accompany bif deposition and make the early earth similar to modern titan therefore although biological processes may have assisted iron oxidation and precipitation they are not a prerequisite for bif deposition

decoupling of p and corg burial following early cretaceous valanginian hauterivian platform drowning along the nw tethyan margin during the hauterivian three important phases of platform drowning phosphogenesis and mesotrophic carbonate deposition along the northern margin of the tethys are not mirrored by positive n 13 ccarb excursions such as during the valanginian and aptian but rather by decreasing to stable trends the aim of this study is to understand the decoupling of organic carbon and phosphorus burial during the hauterivian for this purpose po4 concentrations were determined from biogenic limestones from eight sections along a platform to basin transect integration with a previously obtained dataset for the valanginian leads to a biostratigraphically calibrated high resolution phosphorus accumulation rate mg cm 2 kyr curve based on 575 data points from the late valanginian to early hauterivian phosphorus accumulation rates increased nearly threefold from 0 75 mg cm 2 kyr to 2 1 mg cm 2 kyr the phosphorus accumulation rate increase obtained in this study correlates well with a compilation based on odp and dsdp records indicating that phosphorus accumulation rates along the northern margin of the tethys reflect global changes in p in and output a global rise in continental p input is thought to have resulted from intensified greenhouse climate conditions leading to increased riverine runoff coeval sea level rise led to re arrangement of circulation and oxygenation of bottom waters which meant that p was increasingly well retained by means of fe and mnoxyhydroxides furthermore the nw margin of the tethys may have been especially susceptible to phosphogenesis as it was influenced by cold water exchange with the boreal realm and prone to coastal upwelling the late hauterivian witnessed sea level fall more sluggish circulation along the nw tethyan margin and also globally lower weathering and erosion rates leading to generally lower phosphorus accumulation rates increased regeneration of phosphorus might have occurred as circulation stagnated and bottom water oxygen levels decreased increased phosphorus input into early hauterivian oceans did not lead to the production of organic carbon rich rocks but rather to increased carbonate carbon burial also seen in a decoupling between the n 13 ccarb record decreasing and phosphorus accumulation rates increasing decoupling of these records reflects the ecological recovery of the carbonate system after a prolonged phase of reef destruction during the late early and late valanginian carbonate production in the

the phosphorus cycle phosphogenesis and marine phosphate rich deposits abstract phosphorus in the form of phosphate is an essential nutrient and energy carrier on many different levels of life and a key element in mediating between living and lifeless parts of the biosphere one of the most important aspects of the phosphorus cycle is its vital role in governing productivity thereby interacting with the exogenic part of the carbon cycle which in turn is important in regulating earth s climate phosphorus is a prime element to be traced in earth s history because it allows for the reconstruction of long term feedback mechanisms between climate environment and ecology and of global change as such marine sedimentary phosphate deposits are particularly suited to study aspects of the phosphorus cycle because in the case of ubiquity their origin may result from a general acceleration of the global phosphorus cycle sources of sedimentary phosphate are microbial breakdown of buried organic matter and redox driven phosphate desorption from iron and manganese oxyhydroxides dissolved sea water phosphate represents an additional source which may become important in the formation of phosphatic hardgrounds the main locus of phosphogenesis is near the sediment water interface but phosphogenesis also occurs at greater sediment depths current induced winnowing and transport processes along the sea floor concentrate phosphate precipitates into deposits which exhibit internal stratification patterns typical for the prevailing hydraulic energy regime in a sequence stratigraphic context phosphate deposits preferentially occur along marine or maximum flooding surfaces consequent sedimentary reworking may result in the transfer of phosphates to highstand or lowstand deposits bio chemical weathering on continents represents the most significant source of bioavailable phosphorus this implies that long term changes in marine phosphorus levels and with these changes in marine ecology productivity rates and ratios of exported carbonate carbon and organic carbon are a response to changes in continental weathering rates a compilation of marine sedimentary phosphorus burial rates for the last 160 myr suggests that natural variations have occurred that span one order of magnitude for the late jurassic cretaceous and most of the paleogene the phosphorus cycle appears to have been accelerated in times of climate warming which was most likely due to the spreading of zones of humid climate and more intense continental weathering in the neogene the phosphorus cycle appears to have responded to changes in glacially induced weathering this suggests that uniform interpretations with respect to the emplacement of major phosphorite deposits should be treated with caution integrated analyses of the sedimentary and biogeochemical context of phosphorite occurrences may help to identify paleoenvironmental conditions as well as to improve our understanding of periods of enhanced phosphate accumulation periods which were usually characterized by steep gradients in the development of climate and environment with regard to the complexity of feedback mechanisms between the phosphorus cycle and the biosphere the present day input rates of phosphate into the world s oceans should be of great concern they are more than doubled by anthropogenic means and affect ecological systems on a rapidly increasing scale

effect of dissolved h2so4 on the interaction between co2 rich brine solutions and limestone sandstone and marl abstract the effect of pure and impure carbon dioxide co 2 on geological storage is uncertain oxidation of impurities such as sulfur dioxide so 2 and hydrogen sulfide h 2 s which may be catalyzed by co injected oxygen or nitrogen oxides leads to the formation of sulfuric acid h 2 so 4 and a decrease in ph of the formation water we investigated the effect of 0 005 mol l 1 h 2 so 4 corresponding to a worst case of 0 4 so 2 in the flue gas anticipating total conversion of so 2 into h 2 so 4 on the reactivity of the reservoir limestone and sandstone and cap marl rocks of hontomin spain at p pco 2 10 bar and 60 c during 24 days using flow through column experiments aqueous element concentrations were measured from fluid extracts obtained periodically throughout the experiments to infer fluid rock reactions over time results were modeled with the crunchflow reactive transport code the added h 2 so 4 lowered the ph of the injected brine by 1 5 ph units with respect to the ph of 3 6 of the h 2 so 4 free brine in both h 2 so 4 free and h 2 so 4 rich brine calcite dissolution fostered gypsum precipitation a comparison between the reactivity of the rocks reacted in h 2 so 4 free and h 2 so 4 rich brine showed that calcite dissolution and gypsum precipitation rates were increased by 27 48 and 25 75 respectively in h 2 so 4 rich brine overall rock porosity increments in h 2 so 4 rich brine were 2 9 3 6 3 7 4 8 and 2 1 2 7 for sandstone limestone and marl respectively porosities in h 2 so 4 rich brine were 6 23 and 250 higher respectively than under pure co 2 modeled porosity increments in the acid inlet zone in h 2 so 4 rich brine for sandstone limestone and marl were 28 29 44 45 and 24 28 respectively corresponding to an increase of 1 250 and 25 respectively relative to h 2 so 4 free brine gypsum precipitation was consistently higher in marl than in limestone and sandstone indicating kinetically favorable conditions for gypsum precipitation within the cap rock our results provide relevant data for long term storage simulations of impure co 2 injection

ejecta blocks on 243 ida and on other asteroids abstract seventeen positive relief features 45 150 m across are identified as probable blocks in galileo high resolution images of ida their presence provides direct evidence for regolith retention on asteroids the spatial distribution maximum size and integrated volume of the blocks are consistent with those of blocks associated with craters on the earth the moon phobos and deimos the concordance suggests that the features are impact ejecta fragments and that cratering mechanics on ida an object of average diameter 32 km are similar to those applying on previously studied rocky bodies the blocks that lie within or near the rims of craters lascaux and mammoth were likely mobilized in the low velocity tail portion of the excavation flow that formed those craters a few blocks located near smaller craters may have migrated some distance away from their source possibly by impact induced spallation hopping rolling and or sliding some blocks on ida could be surviving fragments from the koronis parent body accreted after its breakup the lifetime of 102 m sized boulders against collisional disruption is estimated to be in the 108 109year range consistent with ages considered for the largest and oldest craters on ida extrapolation of successful ejecta scaling laws to other asteroids suggests that blocks 15 and 70 m across could be present on dactyl and gaspra respectively in both cases too small to be identified in available galileo images blocks 100 m in size could be present on 433 eros and km sized megablocks on 4 vesta

imaging of small scale features on 433 eros from near evidence for a complex regolith on 25 october 2000 the near earth asteroid rendevous near shoemaker spacecraft executed a low altitude flyover of asteroid 433 eros making it possible to image the surface at a resolution of about 1 meter per pixel the images reveal an evolved surface distinguished by an abundance of ejecta blocks a dearth of small craters and smooth material infilling some topographic lows the subdued appearance of craters of different diameters and the variety of blocks and different degrees of their burial suggest that ejecta from several impact events blanketed the region imaged at closest approach and led to the building up of a substantial and complex regolith consisting of fine materials and abundant meter sized blocks

phobos regolith and ejecta blocks investigated with mars orbiter camera images four flybys of phobos by the mars global surveyor spacecraft in 1998 allowed imaging at resolutions 2 7 m better than obtained for any other satellite or asteroid except earth s moon the images show the interior and vicinity of the large crater stickney there are 2000 identifiable ejecta blocks the largest about 85 m across the great majority of these blocks come from stickney as part of low velocity ejecta spread eastward by the influence of phobos s rapid rotation they appear to have experienced only a few meters at most of burial or modification since emplacement the images also show materials of different albedos within stickney that mark downslope motion of regolith the number of craters on the steep slopes of stickney that are subject to the downslope motion suggests that 4 km have been degraded to the point that they are no longer recognizable

pacific pelagic phosphorus accumulation during the last 10 m y as a limiting nutrient to marine life phosphorus p is an effective tracer of today s marine productivity the distribution of p in marine sediments likewise tracks the history of marine productivity because of its relative insolubility in seawater caco3 biogenic opal terrigenous sediment and total p have been measured in cores from nine pacific sites deep sea drilling project dsdp 65 66 310 77 62 572 463 586 and gpc 3 and one subantarctic dsdp 266 site these sites were specifically chosen to provide information on biota burial flux changes with time for sedimentary sinks that represent key oceanographic variables i e rate of upwelling water depth and carbonate dissolution gradient the accumulation rates of these components for the last 10 ma were then calculated from determined core age versus depth plots core bulk density and porosity data the accumulation of p weakly correlates with that of caco3 moderately with that of total sediment and very strongly with carbonate free accumulation two prominent peaks for all components occur at 2 3 ma and 5 6 ma and record the chemical loading of dissolved caco3 sio2 and p from glacially emergent continental shelves these results indicate that continental shelf phosphorites form during interglacially high sea levels and correspond to low deep sea p accumulation rates whereas glacially lowered sea levels allow for shelf bypassing and greater deep sea p accumulation rates

isotopic analysis of sulfur cycling and gypsum vein formation in a natural co2 reservoir abstract in order to assess the long term security of geologic carbon storage it is crucial to study the geochemical behavior of sulfur in reservoirs that store co2 fossil fuel combustion may produce mixtures of carbon dioxide and sulfur gases and the geochemical effects of sulfur co2 cosequestration are poorly understood this study examines sulfur mineralization from a core drilled in a stacked sequence of natural co2 reservoirs near the town of green river utah these reservoirs include the entrada and navajo sandstone which are separated by the carmel formation caprock and transected by a system of co2 degassing normal faults through which saline co2 charged brines discharge our objective in this study is to evaluate the mechanisms and timing of secondary mineral formation particularly gypsum formation in the co2 reservoirs and intervening caprock the carmel formation contains beds of gypsum within a fault zone secondary veins of gypsum exist throughout the entrada sandstone and carmel formation we report sulfur and oxygen isotope data 34sso4 and 18oso4 respectively measured in gypsum and 34s measured in pyrite and the oxygen and hydrogen isotope composition 18o and d respectively of gypsum hydration water the multiple isotope approach allows us to trace the sources of sulfur in the reservoirs and when combined with structural and petrological evidence the progress of fluid rock reactions and relative timing of vein mineralization the secondary gypsum veins in the carmel formation derive from mixing of fluids with two isotopically distinct sulfate sources sulfate from the gypsum beds within the carmel formation and sulfate rich brines that originate from evaporites in the underlying carboniferous paradox formation the gypsum veins in the entrada sandstone have a relatively wide range of 18oso4 both isotopically more enriched in 18o and more depleted in 18o than the primary gypsum sources we suggest that some aqueous sulfate in the entrada sandstone may cycle through multiple valence states as it undergoes reduction and reoxidation resulting in the replacement of its oxygen atoms and allowing the occasional formation of gypsum with anomalous low 18oso4 our data from gypsum hydration water indicates that groups of gypsum veins formed at two different times gypsum veins in the entrada sandstone and some veins in the carmel formation likely formed during quaternary co2 charged brine discharge events while other veins located close to the gypsum beds in the carmel formation formed earlier likely during cycles of dehydration and rehydration associated with the laramide age 40 mya faulting we conclude that calcium sulfate mineral formation in brine filled fractures may play an important role in inhibiting fluid migration in geologic reservoirs that contain co2

ejection of rock fragments from planetary bodies the recent discovery of alha81005 a small meteorite that undoubtedly came from the moon has raised questions about how an intact rock fragment could survive acceleration to planetary escape velocities this acceleration could only have been produced by a large impact on the lunar surface a small amount of material 0 005 to 0 02 projectile volume may be ejected from an impact crater at speeds exceeding lunar escape velocity without suffering petrographically detectable shock damage the ejected material is protected by stress wave interference close to the free surface the existence and size of this zone depend upon parameters such as the rise time of the stress pulse produced by an impact the fragment size is a function of ejection velocity the lunar meteorite was ejected during an impact event that produced a crater at least 3 6 km in diameter other meteorites may have originated in a similar way

ejecta megaregolith accumulation on planetesimals and large asteroids megaregolith accumulation can have important thermal consequences for bodies that lose heat by conduction as vacuous porosity of the kind observed in the lunar megaregolith lowers thermal conductivity by a factor of 10 i have modeled global average ejecta accumulation as a function of the largest impact size with no explicit modeling of time in conjunction with an assumed cratering size distribution exponent b the largest crater constrains the sizes of all other craters that significantly contribute to a megaregolith the largest impactor mass ratio is a major fraction of the catastrophic disruption mass ratio and in general the largest crater s diameter is close to the target s diameter total accumulation is roughly 1 5 of and proportional to the target s radius global accumulations estimated by this approach are higher than in the classic housen et al 1979 study by a factor of roughly 10 this revision is caused mainly by higher typical largest crater size for b 2 the single largest crater typically contributes close to 50 of the total of new nonrecycled ejecta megaregolith can be destroyed by sintering a process whose pressure sensitivity makes it effective at lower temperature on larger bodies planetesimals 100 km in diameter may be surprisingly well suited about as well suited as bodies two to three times larger in diameter for attaining temperatures conducive to widespread melting a water rich composition may be a significant disadvantage in terms of planetesimal heating as the shallow interior may be densified by aqueous metamorphism and will have a low sintering temperature

bulk density of asteroid 243 ida from the orbit of its satellite dactyl during its reconnaissance of the asteroid 243 ida the galileo spacecraft returned images of a second object 1993 243 1 dactyl1 the first confirmed satellite of an asteroid sufficient data were obtained on the motion of dactyl to determine its orbit as a function of ida s mass here we apply statistical and dynamical arguments to constrain the range of possible orbits and hence the mass of ida combined with the volume of ida2 this yields a bulk density of 2 6 0 5 g cm 3 allowing for the uncertainty in the porosity of ida this density range is consistent with a bulk chon dritic composition and argues against some but not all classes of meteoritic igneous rock types that have been suggested as compositionally representative of s type asteroids like ida

tectonic cycles and the history of the earth s biogeochemical and paleoceanographic record an integrated approach to earth history for the last 2 5 b y reveals the strong interdependence of all geologic variables three earth history components are identified and interrelated secular trends as the earth ages recurring events of a previously proposed supercontinent megacycle worsley et al 1984 1985 and nonrecurring environmental shifts declining secular trends are endogenic heat production atmospheric carbon dioxide levels and surface temperatures continental differentiation enzyme efficiency atmospheric oxygen levels and solar luminosity are increasing secular trends four phases of a supercontinent cycle supercontinent fragmentation maximum continent dispersal continental assembly and supercontinental stasis recur with a 0 5 b y period and are correlated with tectonism cratonic sediment preservation atmospheric and hydrospheric evolution and the distribution of marine platform stable isotopes these correlations reflect coupling among the various oceanic and continental constituents during consecutive supercontinent assemblies and fragmentations nonrecurring shifts are unique and irreversible events in earth history e g development of photosynthesis occurrence of banded iron formations and deposition of detrital uraninite that represent periods of rapid geochemical adjustment to biospheric evolution earth s tectonobiogeochemical history is then synthesized by integrating secular trends and nonrecurring events with the supercontinent cycle emphasizing the preferentially preserved periods of fragmentation and continental dispersal paleoceanographic consequences of the megacycle are considered to reflect the stepwise coupling of secular trends and nonrecurring events to a biotically controlled phosphorus organic carbon climate linkage required to maintain earth s post archean surface temperature

surface downhole electrical resistivity tomography applied to monitoring of co2 storage at ketzin germany abstractsurface downhole electrical resistivity tomography sd ert surveys were repeatedly carried out to image co2 injected at the pilot storage ketzin germany the experimental setup combines surface with downhole measurements by using a permanent electrode array that has been deployed in three wells two baseline experiments were performed during the site startup and three repeat experiments were performed during the first year of co2 injection by the time of the third repeat approximately 13 500 tons of co2 had been injected into the reservoir sandstones at about 650 m depth field data and inverted resistivity models showed a resistivity increase over time at the co2 injector the lateral extent of the related resistivity signature indicated a preferential co2 migration toward the northwest using an experimental resistivity saturation relationship we mapped co2 saturations by means of the resistivity index method for the latest repeat co2 saturations show values of up to 70 near the injectio

eros shape topography and slope processes stereogrammetric measurement of the shape of eros using images obtained by near s multispectral imager provides a survey of the major topographic features and slope processes on this asteroid this curved asteroid has radii ranging from 3 1 to 17 7 km and a volume of 2535 20 km3 the center of figure is within 52 m of the center of mass provided by the navigation team this minimal difference suggests that there are only modest variations in density or porosity within the asteroid three large depressions 10 8 and 5 3 km across represent different stages of degradation of large impact craters slopes on horizontal scales of 300 m are nearly all less than 35 although locally scarps are much steeper the area distribution of slopes is similar to those on ida phobos and deimos regions that have slopes greater than 25 have distinct brighter markings and have fewer large ejecta blocks than do flatter areas the albedo patterns that suggest downslope transport of regolith have sharper boundaries than those on phobos deimos and gaspra the morphology of the albedo patterns their lack of discrete sources and their concentration on steeper slopes suggest transport mechanisms different from those on the previously well observed small bodies perhaps due to a reduced relative effectiveness of impact gardening on eros regolith is also transported in talus cones and in connected sinuous paths extending as much as 2 km with some evident as relatively darker material talus material in at least one area is a discrete superposed unit a feature not resolved on other small bodies flat floored craters that apparently contain ponded material also suggest discrete units that are not well mixed by impacts

the chemical dissolution and physical migration of minerals induced during co2 laboratory experiments their relevance for reservoir quality the characterization of the quality and storage capacity of geological underground reservoirs is one of the most important and challenging tasks for the realization of carbon capture and storage ccs projects one approach for such an evaluation is the upscaling of data sets achieved by laboratory co2 batch experiments to field scale sub microscopic petrophysical tomographic and chemical analytical methods were applied to reservoir sandstone samples from the altmark gas field before and after static autoclave batch experiments at reservoir specific conditions to study the relevance of injected co2 on reservoir quality these investigations confirmed that the chemical dissolution of pore filling mineral phases carbonate anhydrite associated with an increased exposure of clay mineral surfaces and the physical detachment and mobilization of such clay fines illite chlorite are most appropriate to modify the quality of storage sites thereby the complex interplay of both processes will affect the porosity and permeability in opposite ways mineral dissolution will enhance the rock porosity and permeability but fine migration can deteriorate the permeability these reactions are realized down to m scale and will affect the fluid rock reactivity of the reservoirs their injectivity and recovery rates during co2 storage operations

space weathering on eros constraints from albedo and spectral measurements of psyche crater we present combined multi spectral imager msi 0 95 m and near infrared spectrometer nis 0 8 2 4 m observations of psyche crater on s type asteroid 433 eros obtained by the near earth asteroid rendezvous near shoemaker spacecraft at 5 3 km in diameter psyche is one of the largest craters on eros which exhibit distinctive brightness patterns consistent with downslope motion of dark regolith material overlying a substrate of brighter material at spatial scales of 620 m spectrum psyche crater wall materials exhibit albedo contrasts of 32 40 at 0 946 m associated spectral variations occur at a much lower level of 4 8 2 4 we report results of scattering model and lunar analogy investigations into several possible causes for these albedo and spectral trends grain size differences olivine pyroxene and troilite variations and optical surface maturation we find that the albedo contrasts in psyche crater are not consistent with a cause due solely to variations in grain size olivine pyroxene or lunar like optical maturation a grain size change sufficient to explain the observed albedo contrasts would result in strong color variations that are not observed olivine and pyroxene variations would produce strong band correlated variations that are not observed a simple lunar like optical maturation effect would produce strong reddening that is not observed the contrasts and associated spectral variation trends are most consistent with a combination of enhanced troilite a dark spectrally neutral component simulating optical effects of shock and lunar like optical maturation these results suggest that space weathering processes may affect the spectral properties of eros materials causing surface exposures to differ optically from subsurface bedrock however there are significant spectral differences between eros proposed analog meteorites ordinary chondrites and or primitive achondrites and eros freshest exposures of subsurface bright materials after accounting for all differences in the measurement units of our reflectance comparisons we have found that the bright materials on eros have reflectance values at 0 946 m consistent with meteorites but spectral continua that are much redder than meteorites from 1 5 to 2 4 m most importantly we calculate that average eros surface materials are 30 40 darker than meteorites

geomechanical and geochemical effects on sandstones caused by the reaction with supercritical co2 an experimental approach to in situ conditions in deep geological reservoirs the geochemical and geomechanical behaviour of reservoir rocks from deep saline aquifers during the injection and geological storage of co2 is studied in laboratory experiments a combination of geochemical and geomechanical studies was carried out on various sandstones from the north german basin after the mineralogical geochemical and petrophysical characterization a set of sandstone samples was exposed to supercritical sc co2 and brine for 2 4 weeks in an autoclave system one sample was mineralogically and geochemically characterised and then loaded in a triaxial cell under in situ pressure and temperature conditions to study the changes of the geomechanical rock properties after treatment in the autoclaves geochemical alterations mainly in the carbonate but also in the sheet silicate cements as well as in single minerals of the sandstones were observed affecting the rocks granular structure in addition to partial solution effects during the geochemical experiments small grains of secondary carbonate and other mineral precipitations were observed within the pore space of the treated sandstones results of additional geomechanical experiments with untreated samples show that the rock strength is influenced by the saturation degree the confining pressure the pore fluid pressure and temperature the exposure to pure scco2 in the autoclave system induces reduced strength parameters modified elastic deformation behaviour and changes of the effective porosity in comparison to untreated sandstone samples experimental results show that the volume of pore fluid fluxing into the pore space of the sandstones clearly depends on the saturation level of the sample

long term phosphorus flux to deep sea sediments abstract phosphorus and carbonate free accumulation correlate in three equatorial pacific cores for the past 10 my p accumulation exhibits a secular decrease through time with strong superimposed oscillations conservative extrapolation suggests that deep sea sediments compete with shelf phosphorite formation for phosphorus consuming at least half of dissolved riverine input

3 d 40ar39ar geochronology in the parana continental flood basalt province new 40ar39ar analyses of borehole samples from the parana etendeka continental flood basalt province provide critical evidence of eruption rates in unexposed regions when combined with surface samples the new data clarify the duration of this major volcanic province new ages from both surface and borehole samples confirm a 10 12 million year duration of magmatism which post dates the tithonian mass extinction and provide a unique 3 dimensional picture of the spatial and temporal eruption of the lava pile chemically defined magma types are diachronous and the onset of magmatism occurred 500 1000 km inland migrating southeast towards the incipient south atlantic ocean calculated eruption rates increased from 0 03 km3 yr 1 between 138 and 135 ma through 0 13 km3 yr 1 between 135 and 133 ma to 0 21 km3 yr 1 between 133 and 131 ma supporting the notion that the rate of magmatism increased with time and proximity to the developing south atlantic after 131 ma the continental eruption rates dropped dramatically to 0 01 km3 yr 1 presumably because rifting had occurred and eruption centred in the oceanic rio grande rise with eruption rates of around 0 3 0 5 km3 yr 1 given the available constraints on the potential temperature of the plume thickness of the continental lithosphere and degrees of extension through time predicted melt production rates within the plume seriously underestimate the calculated eruption rates on the continent however the eruption rates can be reconciled if melting occurred by conductive heating of volatile enriched mantle the diachronous nature of the magma types supports the idea that melting occurred over a wide area and that the different magma types reflect different source regions rather than the temporal evolution of magmas from a single source given that 10 million years is appropriate to the timescales for conductive heating above the mantle plume it is suggested that these distinct source regions were located within the lithospheric mantle consistent with geochemical studies

on the interaction of pure and impure supercritical co2 with rock forming minerals in saline aquifers an experimental geochemical approach abstract the aim of this experimental study was to evaluate and compare the geochemical impact of pure and impure co2 on rock forming minerals of possible co2 storage reservoirs this geochemical approach takes into account the incomplete purification of industrial captured co2 and the related effects during injection and provides relevant data for long term storage simulations of this specific greenhouse gas batch experiments were conducted to investigate the interactions of supercritical co2 brine and rock forming mineral concentrates albite microcline kaolinite biotite muscovite calcite dolomite and anhydrite using a newly developed experimental setup after up to 42 day 1000 h experiments using pure and impure supercritical co2 the dissolution and solution characteristics were examined by xrd xrf sem and eds for the solid and icp ms and ic for the fluid reactants respectively experiments with mixtures of supercritical co2 99 5 vol and so2 or no2 impurities 0 5 vol suggest the formation of h2so4 and hno3 reflected in ph values between 1 and 4 for experiments with silicates and anhydrite and between 5 and 6 for experiments with carbonates these acids should be responsible for the general larger amount of cations dissolved from the mineral phases compared to experiments using pure co2 for pure co2 a ph of around 4 was obtained using silicates and anhydrite and 7 8 for carbonates dissolution of carbonates was observed after both pure and impure co2 experiments anhydrite was corroded by approximately 50 wt and gypsum precipitated during experiments with supercritical co2 no2 silicates do not exhibit visible alterations during all experiments but released an increasing amount of cations in the reaction fluid during experiments with impure co2 nonetheless precipitated secondary carbonates could not be identified

spatial distribution of ice blocks on enceladus and implications for their origin and emplacement we have mapped the locations of over 100 000 ice blocks across the south polar region of saturn s moon enceladus thus generating the first quantitative estimates of ice block number density distribution in relation to major geological features ice blocks were manually identified and mapped from twenty of the highest resolution 4 25 m per pixel cassini imaging science subsystem iss narrow angle images using arcgis software the 10 100 m diameter positive relief features are marginally visible at the resolution of the images making ice block identifications difficult but not impossible our preliminary results reveal that ice blocks in the southern hemisphere are systematically most concentrated within the geologically active south polar terrain spt and exhibit peak concentrations within 20 km of the tiger stripe fractures as well as close to the south pole we find that ice blocks are concentrated just as heavily between tiger stripe fractures as on the directly adjacent margins although significant local fluctuations in ice block number density do occur we observe no clear pattern with respect to the tiger stripes or jet sources we examine possible roles of several mechanisms for ice block origin emplacement and evolution impact cratering ejection from fissures during cryovolcanic eruptions tectonic disruption of lithospheric ice mass wasting seismic disturbance and vapor condensation around icy fumeroles we conclude that impact cratering as well as mass wasting perhaps triggered by seismic events cannot account for a majority of ice block features within the inner spt the pervasiveness of fracturing at many size scales the ubiquity of ice blocks in the inner spt as well as the occurrence of linear block arrangements that parallel through cutting crack networks along the flanks of tiger stripes indicate that tectonic deformation is an important source of blocky ice features in the spt ejection during catastrophic cryovolcanic eruptions and condensation around surface vents however cannot be ruled out further sublimation processes likely erode and disaggregate ice blocks from solid exposures of ice especially near the warm tiger stripe fractures the relative paucity of blocks beyond the bounds of the spt particularly on stratigraphically old cratered terrains may be explained in part by mantling of the surface by fine particulate ice grains that accumulate over time

impact history of eros craters and boulders abstract preliminary measurements of craters and boulders have been made in various locations on eros from images acquired during the first nine months of near shoemaker s orbital mission including the october 2000 low altitude flyover we offer some very preliminary qualitative analysis of later laf images and very high resolution images obtained during near s landing on 12 february 2001 craters on eros 100 m diameter closely resemble the saturated crater population of ida eros is more heavily cratered than gaspra but lacks the saturated giant craters of mathilde these craters and the other large scale geological features were formed over a duration of very roughly 2 gyr while eros was in the main asteroid belt between the time when its parent body was disrupted and eros was injected into an earth approaching orbit probably tens of myr ago saturation equilibrium had been expected to shape eros crater population down to very small sizes as on the lunar maria however craters

shoemaker crater as the source of most ejecta blocks on the asteroid 433 eros the loose material regolith on the surfaces of asteroids is thought to represent ballistically emplaced ejecta from impacts but the identification of source craters and the detailed study of the regolith modification have been hampered by the limited spatial resolution and area coverage of the few asteroids imaged by spacecraft here we report the results of global mapping of the asteroid 433 eros from high resolution images obtained by the near shoemaker spacecraft based on the images and ejecta emplacement models we suggest that most large ejecta blocks on eros originate from a relatively young 7 6 km diameter crater a large fraction of the ejecta from impacts pre dating that crater has apparently been buried or eroded the images also show evidence for the action of a variety of sorting environments for regolith particles after they are deposited on the surface

first images of asteroid 243 ida the first images of the asteroid 243 ida from galileo show an irregular object measuring 56 kilometers by 24 kilometers by 21 kilometers its surface is rich in geologic features including systems of grooves blocks chutes albedo features crater chains and a full range of crater morphologies the largest blocks may be distributed nonuniformly across the surface lineaments and dark floored craters also have preferential locations ida is interpreted to have a substantial regolith the high crater density and size frequency distribution 3 differential power law index indicate a surface in equilibrium with saturated cratering a minimum model crater age for ida and therefore for the koronis family to which ida belongs is estimated at 1 billion years older than expected

enhanced deformation of limestone and sandstone in the presence of high fluids 1 geological repositories subject to the injection of large amounts of anthropogenic carbon dioxide will undergo chemical and mechanical instabilities for which there are currently little experimental data this study reports on experiments where low and high 8 mpa aqueous fluids were injected into natural rock samples the experiments were performed in flow through triaxial cells where the vertical and confining stresses temperature and pressure and composition of the fluid were separately controlled and monitored the axial vertical strains of two limestones and one sandstone were continuously measured during separate experiments for several months with a strain rate resolution of 10 11 s 1 fluids exiting the triaxial cells were continuously collected and their compositions analyzed the high fluids induced an increase in strain rates of the limestones by up to a factor of 5 compared to the low fluids injection of high fluids into the sandstone resulted in deformation rates one order of magnitude smaller than the limestones the creep accelerating effect of high fluids with respect to the limestones was mainly due to the acidification of the injected fluids resulting in a significant increase in solubility and reaction kinetics of calcite compared to the limestones the much weaker response of the sandstone was due to the much lower solubility and reactivity of quartz in high fluids in general all samples showed a positive correlation between fluid flow rate and strain rate x ray tomography results revealed significant increases in porosity at the inlet portion of each core the porosity increases were dependent on the original lithological structure and composition the overall deformation of the samples is interpreted in terms of simultaneous dissolution reactions in pore spaces and intergranular pressure solution creep

monitoring co2 saturation using time lapse amplitude versus offset analysis of 3d seismic data from the ketzin co2 storage pilot site germany the injection of co2 at the ketzin pilot site commenced in june 2008 and was terminated in august 2013 after 67 kt had been injected into a saline formation at a depth of 630 650 m as part of the site monitoring program four 3d surface seismic surveys have been acquired to date one baseline and three repeats of which two were conducted during the injection period and one during the post injection phase the surveys have provided the most comprehensive images of the spreading co2 plume within the reservoir layer both petrophysical experiments on core samples from the ketzin reservoir and spectral decomposition of the 3d time lapse seismic data show that the reservoir pore pressure change due to co2 injection has a rather minor impact on the seismic amplitudes therefore the observed amplitude anomaly is interpreted to be mainly due to co2 saturation in this study amplitude versus offset analysis has been applied to investigate the amplitude versus offset response from the top of the sandstone reservoir during the injection and post injection phases and utilize it to obtain a more quantitative assessment of the co2 gaseous saturation changes based on the amplitude versus offset modelling a prominent decrease in the intercept values imaged at the top of the reservoir around the injection well is indeed associated solely with the co2 saturation increase any change in the gradient values which would in case it was positive be the only signature induced by the reservoir pressure variations has not been observed the amplitude versus offset intercept change is therefore entirely ascribed to co2 saturation and used for its quantitative assessment the estimated co2 saturation values around the injection area in the range of 40 60 are similar to those obtained earlier from pulsed neutron gamma logging the highest values of 80 are found in the second seismic repeat in close vicinity to the injection and observation wells