refugia from asteroid impacts on early mars and the early earth impacts of asteroids and comets posed a major hazard to the continuous existence of early life on mars as on earth the chief danger was presented by globally distributed ejecta including transient thick rock vapor atmospheres on earth much of the thermal radiation is absorbed by boiling the oceans any surviving life is either in deep water or well below the surface global thermal excursions are buffered by the heat capacity of the oceans but when impacts are large enough to vaporize the oceans l028 j thermal buffering serves only to prolong the disaster for thousands of years while the oceans rain out without oceans thermal buffering does not occur on mars relatively small impacts 1026 j frequently heat the surface everywhere to the melting point however owing to the low martian escape velocity the most energetic ejecta including the rock vapor more easily escape to space while massive quantities of less energetic ejecta are globally distributed survival in deep subsurface environments is more likely on mars because 1 mars lower background heat flow and lower gravity allow deeper colonies and 2 the thermal heat pulse from a major impact is briefer only thermophile organisms could have survived impacts of asteroids large enough to leave heat or boil the entire terrestrial ocean studies of terrestrial microorganisms indicate that the last common ancestor may have been thermophile and the survivor of such a catastrophe this organism should be distinguished from the first common ancestor an additional refugium is ejection of rock to space by impacts and thier return to a habitable planet

the sinkhole of doganella pontina plain central italy a case study describes the recent catastrophic subsidence of the land surface neighboring the lepini karstic range lazio region a number of sinkholes in the pontina plain are shown on the early topographic maps dated 1850 their origin is natural and related to subsidence that occurred during the holocene a review of sinkholes in central italy was made by facenna and others 1993 the aim of this study is to clarify the possible relationships between tectonics and sinkhole formation the subsidence phenomena have been related to the slow dissolution of the buried carbonate bedrock due to fluids rich in co2 h2s and so2 which migrate through major tectonic fractures lowering of piezometric levels in waterbearing formations and seismic events are also important factors as they may upset the stability of a cave system buried by unconsolidated deposits

mechanics of upward propagation of cover collapse sinkholes cover collapse sinkholes occur by failure of the walls of a soil void above cavernous bedrock i examine conditions for failure in compression by crack propagation and coalescence and for failure by sloughing in which pore water pressure produces a net tension perpendicular to the wall of the void compressive failure without relaxation of stress does not explain observed long term stability of thick soils nor failures in thin residual soils if stress relaxation occurs with compressive failure soil voids tend to stabilize and sinkholes are not predicted sloughing failure is not predicted for steady state pore pressure fields even for a perched water table at the surface over a drained void transient pore pressure conditions that could produce sloughing may result from 1 rapid drawdown causing soil consolidation and transient high pore pressure gradients 2 approach of a wetting front in unsaturated soil with high permeability behind the front 3 dissolution of air from bubbles in the soil and exsolution near the void producing a low permeability zone near the void

the martian subsurface as a potential window into the origin of life few traces of earth s geologic record are preserved from the time of life s emergence over 3 800 million years ago consequently what little we understand about abiogenesis the origin of life on earth is based primarily on laboratory experiments and theory the best geological lens for understanding early earth might actually come from mars a planet with a crust that s overall far more ancient than our own on earth surface sedimentary environments are thought to best preserve evidence of ancient life but this is mostly because our planet has been dominated by high photosynthetic biomass production at the surface for the last 2 500 million years or more by the time oxygenic photosynthesis evolved on earth mars had been a hyperarid frozen desert with a surface bombarded by high energy solar and cosmic radiation for more than a billion years and as a result photosynthetic surface life may never have occurred on mars therefore one must question whether searching for evidence of life in martian surface sediments is the best strategy this perspective explores the possibility that the abundant hydrothermal environments on mars might provide more valuable insights into life s origins ancient hydrothermal deposits formed in the martian subsurface may be the best targets for finding evidence for ancient life on mars and clues about the origin of life on earth

deep crustal carbonate rocks exposed by meteor impact on mars mars may have once had a co2 rich atmosphere but carbonate rocks that could provide evidence for such conditions are sparse spectral analyses of rocks exposed from deep within an impact crater reveal that carbonate deposits may be extensive on mars but are buried under layers of younger volcanic rocks

sinkholes in italy first results on the inventory and analysis the italian geological survey apat carried out field surveys and analysis of collapse phenomena sinkholes in italy the main goal of the project is to collect geological geomorphological geochemical and hydrogeological data about the sinkhole prone areas in italy in order to develop a spatial database of the characteristics of each phenomenon the preliminary results of this study provide information on the distribution geological setting and monitoring and remediation actions associated with these natural collapses in italy many italian regions are affected by these natural disasters some of them are caused by karst collapses or anthropic activity however some occur in areas characterized by buried carbonate bedrock up to 190 m as well as by peculiar geological structural and geochemical scenarios in these areas it is not reasonable to ascribe the formation mechanism to karst activity instead these types of cavities quickly develop in terrains with a variable granulometry often in connection with upwelling fluids in this work some natural specific cases have been studied in order to define the relationships between the geology regional tectonic elements mineral spring waters and strong gas vents and the genesis of the sinkholes a first attempt of sinkhole classification is also presented

comparison of warm and wet and cold and icy scenarios for early mars in a 3 d climate model we use a 3 d general circulation model to compare the primitive martian hydrological cycle in warm and wet and cold and icy scenarios in the warm and wet scenario an anomalously high solar flux or intense greenhouse warming artificially added to the climate model are required to maintain warm conditions and an ice free northern ocean precipitation shows strong surface variations with high rates around hellas basin and west of tharsis but low rates around margaritifer sinus where the observed valley network drainage density is nonetheless high in the cold and icy scenario snow migration is a function of both obliquity and surface pressure and limited episodic melting is possible through combinations of seasonal volcanic and impact forcing at surface pressures above those required to avoid atmospheric collapse 0 5 bar and moderate to high obliquity snow is transported to the equatorial highland regions where the concentration of valley networks is highest snow accumulation in the aeolis quadrangle is high indicating an ice free northern ocean is not required to supply water to gale crater at lower surface pressures and obliquities both h2o and co2 are trapped as ice at the poles and the equatorial regions become extremely dry the valley network distribution is positively correlated with snow accumulation produced by the cold and icy simulation at 41 8 obliquity but uncorrelated with precipitation produced by the warm and wet simulation because our simulations make specific predictions for precipitation patterns under different climate scenarios they motivate future targeted geological studies

a review on natural and human induced geohazards and impacts in karst karst environments are characterized by distinctive landforms related to dissolution and a dominant subsurface drainage the direct connection between the surface and the underlying high permeability aquifers makes karst aquifers extremely vulnerable to pollution a high percentage of the world population depends on these water resources moreover karst terrains frequently underlain by cavernous carbonate and or evaporite rocks may be affected by severe ground instability problems impacts and hazards associated with karst are rapidly increasing as development expands upon these areas without proper planning taking into account the peculiarities of these environments this has led to an escalation of karst related environmental and engineering problems such as sinkholes floods involving highly transmissive aquifers and landslides developed on rocks weakened by karstification the environmental fragility of karst settings together with their endemic hazardous processes have received an increasing attention from the scientific community in the last decades concurrently the interest of planners and decision makers on a safe and sustainable management of karst lands is also growing this work reviews the main natural and human induced hazards characteristic of karst environments with specific focus on sinkholes floods and slope movements and summarizes the main outcomes reached by karst scientists regarding the assessment of environmental impacts and their mitigation

a generalized genetic framework for the development of sinkholes and karst in florida u s a karst topography in florida is developed on the tertiary limestones of the floridan aquifer post depositional diagenesis and solution have made these limestones highly permeable t ca 50 000 m2 d zones of megaporosity have formed at unconformities and dissolution has enlarged joints and fractures erosion of the overlying clastic miocene hawthorn group strata on one flank of a structural arch has exposed the limestone the elevated edge of the hawthorn cover forms the cody scarp ubiquitous solution pipes have previously formed at joint intersections and are now filled downwashing of the fill deeper into solution cavities in the limestone and subsidence of the overlying unconsolidated sediments causes surface collapse a subsidence doline or sinkhole this process may penetrate up to 60 m of the semi consolidated hawthorn cover as occurred when the winter park sinkhole developed dense clusters of solution pipes may have formed cenotes which are now found on the exposed limestone terrain

storm track dynamics this paper reviews the current state of observational theoretical and modeling knowledge of the midlatitude storm tracks of the northern hemisphere cool season observed storm track structures and variations form the first part of the review the climatological storm track structure is described and the seasonal interannual and interdecadal storm track variations are discussed in particular the observation that the pacific storm track exhibits a marked minimum during midwinter when the background baroclinicity is strongest and a new finding that storm tracks exhibit notable variations in their intensity on decadal timescales are highlighted as challenges that any comprehensive storm track theory or model has to be able to address physical processes important to storm track dynamics make up the second part of the review the roles played by baroclinic processes linear instability downstream development barotropic modulation and diabatic heating are discussed understanding of these processes forms the core of our current theoretical knowledge of storm track dynamics and provides a context within which both observational and modeling results can be interpreted the eddy energy budget is presented to show that all of these processes are important in the maintenance of the storm tracks the final part of the review deals with the ability to model storm tracks the success as well as remaining problems in idealized storm track modeling which is based on a linearized dynamical system are discussed perhaps on a more pragmatic side it is pointed out that while the current generation of atmospheric general circulation models faithfully reproduce the climatological storm track structure and to a certain extent the seasonal and enso related interannual variations of storm tracks in depth comparisons between observed and modeled storm track variations are still lacking

timing of water plume eruptions on enceladus explained by interior viscosity structure water plume eruptions on saturn s icy moon enceladus are delayed relative to the peak tidal stresses simulations suggest the delay can be explained by the moon s interior structure and the presence of a subsurface ocean at the south pole of saturn s icy moon enceladus eruptions of water vapour and ice emanate from warm tectonic ridges1 2 3 4 observations in the infrared5 and visible6 spectra have shown an orbital modulation of the plume brightness which suggests that the eruption activity is influenced by tidal forces however the observed activity seems to be delayed by several hours with respect to predictions based on simple tidal models6 7 here we simulate the viscoelastic tidal response of enceladus with a full three dimensional numerical model8 9 and show that the delay in eruption activity may be a natural consequence of the viscosity structure in the south polar region and the size of the putative subsurface ocean by systematically comparing simulations of variations in normal stress along faults with plume brightness data we show that the observed activity is reproduced for two classes of interior models with contrasting thermal histories a low viscosity convective region above a polar sea extending about 45 60 from the south pole at a depth below the surface as small as 30 km or a convecting ice shell of 60 70 km in thickness above a global ocean our analysis further shows that the eruption activity is controlled by the average normal stress applied across the cracks thus providing a constraint on the eruption mechanism

baroclinic development in observations and nasa gsfc general circulation models abstract comparative diagnostic analyses of developing synoptic scale baroclinic disturbances in ncep ncar reanalyses and the nasa ncar nascar and aries nasa s seasonal to interannual prediction project nsipp general circulation model simulations are performed in particular lag composite analyses of wintertime cyclonic and anticyclonic events occurring in the north pacific and north atlantic storm tracks are constructed to pursue a synoptic and dynamic characterization of eddy development the data are also seasonally stratified to study aspects of the north pacific midwinter suppression phenomenon winter averaged results indicate that the model simulated events are generally too weak in amplitude particularly in the upper troposphere for the north pacific storm track model simulated events are also anomalously distended in the meridional direction the existing model biases in eddy structure and magnitude lead to anomalously weak baroclinic energy conversions for both cyclonic and anticycloni

evidence of ancient life at 207 m depth in a granitic aquife the results of electron microscopy investigations of calcite precipitated in a water conducting fracture in a ca 1800 ma granitic rock from 207 m below sea level at the island of aspo on the southeastern baltic coast of sweden are compared with measurements of carbon oxygen and sulfur isotope composition of the calcite and embedded pyrite parts of the calcite had extremely low 13c values indicative of biological activity and contained bacteria like microfossils occurring in colonies and as typical biofilms x ray microanalysis demonstrated these fossils to be enriched in carbon our results provide evidence for ancient life in deep granitic rock aquifers and suggest that the modern microbial life found there is intrinsic modeling historical and present geochemical processes in deep granitic aquifers should therefore preferably include biologically catalyzed reactions the results also suggest that the search for life on other planets e g mars should include subsurface material

u rich archaean sea floor sediments from greenland indications of 3700 ma oxygenic photosynthesis abstract 3700 ma metamorphosed pelagic shale from west greenland contains up to 0 4 wt reduced carbon with 13c values down to 25 6 pdb peedee belemnite the isotopic signature and mode of occurrence suggest that the carbon derived from planktonic organisms the pb isotopic composition shows that the shale had high primary u th this indicates that organic debris produced a local reducing environment which precipitated u transported to the site of sedimentation by oxidized ocean water the existence of highly productive plankton that fractionated c isotopes strongly and set up oxidation contrast in the environment suggests that oxygenic photosynthesis evolved before 3700 ma

fracture controlled fluid circulation and dissolutional weathering in sinkhole prone carbonate rocks from central italy abstract fractures karstic cavities and calcite precipitates are analysed on mesozoic carbonate strata from the cornicolani mountains central italy to quantify the relationships between fractures and related karstic cavities and to infer the fracture controlled fluid pathways the study area is characterized by active sinkholes and other karstic caves which are among the deepest ones in the world results show a clear control of fractures on the process of dissolutional weathering and therefore on the fluid circulation a model is proposed in which two different modes of dissolutional weathering coexist i a mode of diffuse weathering consisting in the dissolutional enlargement of closely spaced joints and bedding surfaces this process affects the strata situated at depths of up to 5 m ii a mode of more concentrated weathering active along highly permeable fault damage zones at depths of at least 70 m these processes are mostly connected with the shallow circulation of calcite dissolving meteoric waters and are controlled by the disparity of permeability between the fault damage zones and the surrounding jointed strata some calcite precipitates along the studied fault damage zones may be connected with a dissolutional process operated by waters that interacted with the adjacent quiescent volcanic district such calcite dissolving waters and the presence of high permeable fault damage zones along which the waters may ascent are probably the cause for the development of some of the deep sinkholes along faults in the study area

groundwater fluxes into a submerged sinkhole area central italy using radon and water chemistry abstract the groundwater contribution into green lake and black lake vescovo lakes group two cover collapse sinkholes in pontina plain central italy was estimated using water chemistry and a 222 rn budget these data can constrain the interactions between sinkholes and deep seated fluid circulation with a special focus on the possibility of the bedrock karst aquifer feeding the lake the rn budget accounted for all quantifiable surface and subsurface input and output fluxes including the flux across the sediment water interface the total value of groundwater discharge into green lake and black lake 540 160 l s 1 obtained from the rn budget is lower than but comparable with historical data on the springs group discharge estimated in the same period of the year 800 90 l s 1 besides being an indirect test for the reliability of the rn budget tool it confirms that both green and black lake are effectively springs and not simply water filled sinkholes new data on the water chemistry and the groundwater fluxes into the sinkhole area of vescovo lakes allows the assessment of the mechanism responsible for sinkhole formation in pontina plain and suggests the necessity of monitoring the changes of physical and chemical parameters of groundwater below the plain in order to mitigate the associated risk

simulation experiment on sinkhole formation caused by soils disintegration and the advance forecasting of sinkhole risk sinkholes are a common geological hazard around the world however it is difficult to carry out the associated indoor simulation experiments because of the complicated factors involved our previous research showed that sinkholes in the aerated zone caused by soil disintegration exhibit accurate critical conditions therefore the kind of sinkhole formation is simulated in the paper before the simulate experiment the critical value of the disintegration of clay samples is tested which helps to control the simulation conditions with a designed simulation apparatus soil disintegration was conducted 70 times from october 23 2017 to june 1 2018 and a sinkhole formed this experiment results indicate two developmental laws of sinkholes forming in the aerated zone one is the forming process which has three stages soil void formation soil void expansion and roof collapse second is that the two conditions water content is less than the critical value and contact between water and soil causing the sinkhole formation at the forming two conditions are clear and can easily be monitored by the associated factors in the field where sinkholes have occurred or are about to occur according to the principle another simulation experiment was carried out as a result an advanced prediction of a sinkhole is achieved in the aerated zone

earth fissures triggered by groundwater withdrawal and coupled by geological structures in jiangsu province china earth fissures in jiangsu province china have caused serious damages to properties farmlands and infrastructures and adversely affected the local or regional economic development under the geological and environmental background in jiangsu province this paper presents the earth fissures caused by excessive groundwater withdrawal and coupled by distinctive geological structures such as ancient yellow river fault in xuzhou karst area and ancient yangtze river course and bedrock hills in suzhou wuxi and changzhou area although all the earth fissures are triggered by groundwater exploitation the characteristics are strongly affected by the specific geological and hydrogeological settings in particular in the water thirsty xuzhou city the cone of depression caused by groundwater extraction enlarged nearly 20 times and the piezometric head of groundwater declined 17 m over a decade as groundwater is extracted from the shallowly buried karst strata in the ancient yellow river fault zone the development of earth fissures is highly associated with the development of karstic cavities and sinkholes and their distribution is controlled by the ancient yellow river fault with all the 17 sinkholes on the fault on the other hand in the rapidly developing southern jiangsu province groundwater is mainly pumped from the second confined aquifer in the quaternary which is distributed neither homogeneously nor isotropically the second confined aquifer comprises more than 50 m thick sand over the ancient yangtze river course but this layer may completely miss on the riverbank and bedrock hills with a typical drawdown rate of 4 6 m per annum the piezometric head of groundwater in the second confined aquifer has declined 76 m at maocunyuan since 1970s and 40 m at changjing since mid 1980s and a large land subsidence e g 1 100 mm at maocunyuan is triggered coupled with the dramatic change of the bedrock topography that was revealed through traditional geological drilling and modern seismic reflection methods the geological structure controlled differential settlement and earth fissures are phenomenal in this area

structure and evolution of baroclinic waves as inferred from regression analysis abstract the structure of transient disturbances with periods shorter than a week is documented an the basis of one point regression maps and longitude height sections derived from the national meteorological center nmc operational analyses for nine winter seasons the reference time series for the regression coefficients is highpass filtered normalized 500 mb height at a grid point in the pacific stormtrack the field variables that were regreesed on the reference time series were not filtered the regression statistics yield quantitative estimates of the amplitudes of the high frequency fluctuations in the geopotential height temperature wind ageostrophic wind vorticity divergence vertical velocity and outgoing longwave radiation fields the observed high frequency fluctuations exhibit a vertical and meridional structure suggestive of baroclinic waves evolving through the mature phase of their life cycle most of the results are in qualitative agreement with previous studies but the ageostrop

development of collapse sinkholes in areas of groundwater discharge abstract collapse sinkholes are found in groundwater recharge zones throughout the world they cause substantial loss of property each year and occasional fatalities in such settings the formation of these features occurs through the downward migration of regolith into karst voids the presence of a void in the bedrock and sufficient seepage pressure or gravitative force in the regolith is required for their creation we investigated the development of cover collapse sinkholes in an unusual setting areas of groundwater discharge rather than recharge upward hydraulic gradients and the likelihood of groundwater saturated with respect to calcite are difficult to reconcile with standard models for collapse development short flowpaths or renewed groundwater aggressivity towards calcite via mischungskorrosion thermally driven circulation or deep seated gaseous sources are hypothetical mechanisms that could generate the subsurface voids that are needed to allow cover collapse development in discharge areas for the two field sites in central italy that we investigated calculated carbon dioxide partial pressures in springs ranged from 7 38 10 2 to 7 29 10 1 atm this indicates that deep seated gaseous sources are most likely the mechanism allowing the development of the sinkholes groundwater is recharged in surrounding limestone massifs the water moves through the carbonates and becomes saturated with calcite as it circulates deeply in to the adjacent valleys it mixes with deep seated waters and gaseous fluxes from major fault systems acquiring renewed aggressivity towards calcite finally the water ascends into confined aquifers in the valley fill and dissolves carbonate material present within leading to surface collapse

biomarker hydrogen isotope composition δd as proxy for holocene hydroclimatic change and seismic activity in sw peloponnese greece we present a 6000 year long record tracing hydroclimate changes in sw greece based on hydrogen isotope composition of aquatic plant derived n c 23 alkanes d c23 in a sediment core from the messe

active formation of chaos terrain over shallow subsurface water on europa the galileo spacecraft revealed a number of chaos regions on jupiter s moon europa where the surface terrain appears to have been disrupted from below in many places the surface contains sharp edged blocks or rafts of ice that have at some point been flipped or rotated some characteristics of these regions have been hard to explain such as the fact that the archetypal conamara chaos stands above its surroundings and contains matrix domes schmidt et al apply lessons learned from analogous processes within earth s subglacial volcanoes and ice shelves to an analysis of archival data that suggests chaos terrain forms above liquid water lenses that are perched only 3 kilometres deep within the ice shell the data suggest that ice water interactions and freeze out give rise to the varied morphology of chaos terrains implying that more water is involved than has been previously appreciated for instance the sunken topography of thera macula a large chaos area may indicate that europa is actively resurfacing over a lens comparable in volume to north america s great lakes europa the innermost icy satellite of jupiter has a tortured young surface1 2 3 4 and sustains a liquid water ocean1 2 3 4 5 6 below an ice shell of highly debated thickness1 2 3 4 5 7 8 9 10 quasi circular areas of ice disruption called chaos terrains are unique to europa and both their formation and the ice shell thickness depend on europa s thermal state1 2 3 4 5 7 8 9 10 11 12 13 14 15 16 17 no model so far has been able to explain why features such as conamara chaos stand above surrounding terrain and contain matrix domes10 18 melt through of a thin few kilometre shell3 7 8 is thermodynamically improbable and cannot raise the ice10 18 the buoyancy of material rising as either plumes of warm pure ice called diapirs1 9 10 11 12 13 14 15 or convective cells16 17 in a thick 10 kilometres shell is insufficient to produce the observed chaos heights and no single plume can create matrix domes10 18 here we report an analysis of archival data from europa guided by processes observed within earth s subglacial volcanoes and ice shelves the data suggest that chaos terrains form above liquid water lenses perched within the ice shell as shallow as 3 kilometres our results suggest that ice water interactions and freeze out give rise to the diverse morphologies and topography of chaos terrains the sunken topography of thera macula indicates that europa is actively resurfacing over a lens comparable in volume to the great lakes in north america

hydrothermal activity recorded in post noachian aged impact craters on mars hydrothermal systems have previously been reported in ancient noachian and hesperian aged craters on mars using crism but not in amazonian aged impact craters however the nakhlite meteorites do provide evidence of amazonian hydrothermal activity this study uses crism data of 144 impact craters of 7 km diameter and 14 smaller craters 3 7 km diameter within terrain mapped as amazonian to search for minerals that may have formed as a result of impact induced hydrothermal alteration or show excavation of ancient altered crust no evidence indicating the presence of hydrated minerals was found in the 3 7 km impact craters hydrated minerals were identified in three complex impact craters located at 52 42 n 39 86 e in the ismenius lacus quadrangle at 8 93 n 141 28 e in elysium and within the previously studied stokes crater these three craters have diameters 20 km 62 km and 51 km the locations of the hydrated mineral outcrops and their associated morphology indicate that two of these three impact craters the unnamed ismenius lacus crater and stokes crater possibly hosted impact induced hydrothermal systems as they contain alteration assemblages on their central uplifts that are not apparent in their ejecta chlorite and fe serpentine are identified within alluvial fans in the central uplift and rim of the ismenius lacus crater whereas stokes crater contains a host of fe mg al phyllosilicates however excavation origin cannot be precluded our work suggests that impact induced hydrothermalism was rare in the amazonian and or that impact induced hydrothermal alteration was not sufficiently pervasive or spatially widespread for detection by crism

overview of the spirit mars exploration rover mission to gusev crater landing site to backstay rock in the columbia hills spirit landed on the floor of gusev crater and conducted initial operations on soil covered rock strewn cratered plains underlain by olivine bearing basalts plains surface rocks are covered by wind blown dust and show evidence for surface enrichment of soluble species as vein and void filling materials and coatings the surface enrichment is the result of a minor amount of transport and deposition by aqueous processes layered granular deposits were discovered in the columbia hills with outcrops that tend to dip conformably with the topography the granular rocks are interpreted to be volcanic ash and or impact ejecta deposits that have been modified by aqueous fluids during and or after emplacement soils consist of basaltic deposits that are weakly cohesive relatively poorly sorted and covered by a veneer of wind blown dust the soils have been homogenized by wind transport over at least the several kilometer length scale traversed by the rover mobilization of soluble species has occurred within at least two soil deposits examined the presence of monolayers of coarse sand on wind blown bedforms together with even spacing of granule sized surface clasts suggests that some of the soil surfaces encountered by spirit have not been modified by wind for some time on the other hand dust deposits on the surface and rover deck have changed during the course of the mission detection of dust devils monitoring of the dust opacity and lower boundary layer and coordinated experiments with orbiters provided new insights into atmosphere surface dynamics

detection of preferential infiltration pathways in sinkholes using joint inversion of self potential and em 34 conductivity data the percolation of water in the ground is responsible for measurable electric potentials called self potentials these potentials are influenced by the distribution of the electrical conductivity of the ground because sinkholes are associated both with self potential and electrical conductivity anomalies a joint inversion of em 34 conductivity and self potential data is proposed as a way of delineating the location of these features self potential and em conductivity data were obtained at a test site in normandy france where sinkholes and crypto sinkholes are present over a karstic area in a chalk substratum overlain by clay with flint and loess covers the presence of sinkholes and crypto sinkholes is associated with negative self potential anomalies with respect to a reference electrode located outside the area where the sinkholes are clustered the sinkholes also have a conductivity signature identified by the em 34 conductivity data we used the simulated annealing method which is a global optimization technique to invert jointly em 34 conductivity and self potential data self potential and electrical conductivity provide clear complementary information to determine the interface between the loess and clay with flint formations the sinkholes and crypto sinkholes are marked by depressions in this interface focusing the groundwater flow towards the aquifer contained in the chalk substratum

mars in the aftermath of a colossal impact abstract the abundance of highly siderophile elements hses inferred for mars mantle from martian meteorites implies a late veneer lv mass addition of 0 8 wt with broadly chondritic composition late accretion to mars by a differentiated ceres sized 1000 km diameter object can account for part of the requisite lv mass and geochronological constraints suggests that this must have occurred no later than ca 4480 ma here we analyze the outcome of the hypothetical lv giant impact to mars with smoothed particle hydrodynamics simulations together with analytical theory results show that in general about 50 of the impactor s metallic core shatters into 10 m fragments that subsequently fragment into sub mm metallic hail at re accretion this returns a promising delivery of hses into martian mantle compared to either a head on and hit and run collision in both cases 10 myr a dense pre noachian co2 atmosphere should lower the escape efficiency of hydrogen by ir emission a more detailed hydrodynamic atmospheric model of this early hydrogen atmosphere is warranted to examine its effect on pre noachian mars

a siberian precursor to midwinter intraseasonal variability in the north pacific storm track 1 an observational diagnostic analysis is performed to study variations in the behavior of upper tropospheric rossby waves prior to intraseasonal variability in the north pacific storm track the research is motivated from considerations of the midwinter suppression of the north pacific storm track during midwinter strong upper tropospheric cyclone events in the north pacific storm track are preceded 7 days by a large scale cyclonic circulation anomaly located over siberia the siberian precursor anomaly is found to be strongly linked to one of the primary modes of upper tropospheric intraseasonal variability over asia more generally this asian mode is determined to provide a substantial modulation in the structure and amplitude of the north pacific storm track at lead times of 5 to 8 days this downstream influence is concentrated during midwinter and is likely related to intraseasonal variations in the east asian winter monsoon

widespread surface weathering on early mars a case for a warmer and wetter climate abstract early mars 3 ga underwent aqueous alteration as evidenced by fluvial lacustrine morphologies and the recent discovery of widespread hydrous clays despite compelling evidence for diverse and localized aqueous environments the possibility for sustained liquid water globally on the martian surface and over geological timescales is still highly debated instead a durably cold and dry mars scenario is often proposed by studying specific fe mg and al rich clay stratigraphies on mars by means of a planetary scale orbital investigation we present new evidence that mars experienced an early era 3 7 ga of widespread aqueous alteration consistent with surface weathering

characterizing hydrological processes on loess slopes using electrical resistivity tomography a case study of the heifangtai terrace northwest china abstract from the perspective of engineering geology loess has long been considered as a homogeneous and porous material it is commonly believed that water penetrates loess via pores and in some cases causing mass movements however several researchers have expressed doubts about this mechanism as a cause of slope failures in loess and moreover the actual hydrological processes operating in loess deposits and their effect on slope failures have not been fully investigated here we present the results of an electrical resistivity survey of the heifangtai loess terrace in northwestern china designed to characterize the hydrological processes in loess slopes and their relationship with slope failures the heifangtai loess terrace is located on the fourth terrace of the yellow river and consists of 57 m thickness of aeolian loess 2d and 3d electrical resistivity tomography ert was used to monitor the movement of ground water before and after irrigation and rainfall events and the evolution of a sink hole in the toe of the landslide deposits our main findings are as follows 1 based on the 2d ert results the depth of infiltration into the thick unsaturated loess is not more than 5 m in the profile at the top of the landslide 2 electrical resistivity decreased as a result of water infiltration through sinkholes and this process can increase the soil water content and induce soil liquefaction which can eventually result in land sliding 3 landslide deposits block the groundwater drainage channels through the loess which results in the concentration of water in the toe of the landslide consequently groundwater together with rainfall triggers the failure of sinkholes or cracks which may induce a continuing process of new slope failures at the sites of past landslide

the role of the central asian mountains on the midwinter suppression of north pacific storminess abstractthe role of the central asian mountains on north pacific storminess is examined using an atmospheric general circulation model by varying the height and the areas of the mountains a series of model integrations show that the presence of the central asian mountains suppresses the north pacific storminess by 20 30 during boreal winter their impact on storminess is found to be small during other seasons the mountains amplify stationary waves and effectively weaken the high frequency transient eddy kinetic energy in boreal winter two main causes of the reduced storminess are diagnosed first the decrease in storminess appears to be associated with a weakening of downstream eddy development the mountains disorganize the zonal coherency of wave packets and refract them more equatorward as the zonal traveling distance of wave packets gets substantially shorter downstream eddy development gets weaker second the central asian mountains suppress the global baroclinic energy conversion the decre

intraseasonal variation of the strength of the east asian trough and its climatic impacts in boreal winter abstractthe east asian trough eat is a distinct component of the boreal winter circulation whose strength corresponds to the amplitude of the northern hemispheric stationary waves in this study the mechanism and climatic impacts of the intraseasonal variations of the eat s strength are investigated through composite analysis and dynamical diagnostics the significant roles played by the low frequency rossby wave rw and synoptic transient eddy te are revealed before the peaks of strong eat events an upper tropospheric rw train propagates across northern eurasia and interacts with preexisting surface cold anomalies over central siberia this pattern intensifies the siberian high and causes rw convergence toward the eat leading to 30 of the eat s amplification directly via the rw induced feedback forcing meanwhile rw weakens the background baroclinicity and reduces te activities near the entrance region of the north pacific storm track the te induced feedback forcing leads to another 30 of th

the impact of wave packets propagating across asia on pacific cyclone development abstract in this paper ecmwf 40 yr reanalysis data have been examined to study the influence of upper level wave packets propagating across asia into the pacific on surface cyclone development over the pacific previous studies have shown that in winter wave packets propagate across asia over two branches a northern branch over siberia and a southern branch along the subtropical jet across southern asia results presented here show that subsequent to the presence of wave packets on either branch the frequency of occurrence of deep cyclones defined as cyclones with central pressure below 960 hpa as well as explosively deepening cyclones those with a deepening rate of 1 bergeron or more are significantly enhanced this enhancement also clearly follows the wave packet eastward as it propagates across the pacific wave packets from the two branches are found to interfere with each other such that if wave packets of the appropriate configuration are present on both the northern and southern branch s

habitability of the marine serpentinite subsurface a case study of the lost city hydrothermal field the lost city hydrothermal field is a dramatic example of the biological potential of serpentinization microbial life is prevalent throughout the lost city chimneys powered by the hydrogen gas an

midwinter suppression of baroclinic wave activity in the pacific abstract seasonal variations in baroclinic wave activity and jet stream structure in the northern hemisphere are investigated based upon over 20 years of daily data baroclinic wave activity at each grid point is represented for each day by an envelope function the lowpass filtered time series of the squared highpass filtered geopotential height baroclinic wave activity over the atlantic exhibits a single maximum in january whereas in the pacific it exhibits peaks in late autumn and in early spring and a significant weakening in midwinter which is more evident at the tropopause level than near the surface this suppression occurs despite the fact that the low level baroclinity and the intensity of the jet stream are strongest in midwinter based on the analysis of 31 day running mean fields for individual winters it is shown that over both the oceans baroclinic wave activity is positively correlated with the strength of the upper tropospheric jet for wind speeds up to 45 m s 1 when the strength of t

fluvial sedimentary deposits on mars ancient deltas in a crater lake in the nili fossae region 1 new spacecraft observations in the nili fossae region of mars reveal two valley networks 80 and 200 km long that each formed distributary fans as they entered an ancient 40 km diameter impact crater an outlet channel on the eastern crater rim lying at an elevation above the fans suggests these fans formed as subaqueous deltas in a crater lake water flowing in the valley networks entered the crater and deposited the fans and ponded to a maximum depth of about 450 m the lake then overtopped and breached the crater rim incising it and dropping the lake level by 100 m geological evidence combined with the volume of water necessary to fill the crater suggests the duration of flow through this system was prolonged the existence of the deposits described here implies that the early martian environment supported overland flow and ponding of water for an extended period of time

observed changes in baroclinic wave activity during the life cycles of low frequency circulation anomalies abstract anomalous baroclinic wave activity during the onset and decay of blocking patterns in the northern hemisphere winter is investigated based upon a 30 year record of 500 mb height and sea level pressure a slowly varying envelope function is defined at each gridpoint in order to represent the modulation of the amplitude of baroclinic wave activity by the low frequency circulation anomalies related to blocking the envelope function fields and the low frequency circulation fields are composited relative to the onset and decay times of four persistent dipole patterns in low frequency circulation anomalies located downstream of the climatological mean stormtracks one polarity of the anomaly patterns corresponds to dipole or modon like blocking patterns over the eastern oceans and the other to strong zonal flow patterns each of the eight composites is comprised of more than 50 persistent blocking or zonal flow episodes the most striking common feature observed during the onset of blocking over th

sinkholes dolines in lateritised sediments western sturt plateau northern territory australia abstract sinkholes up to 50 m diameter and 15 m deep are developed in the lateritised mullaman lower cretaceous quartzitic and argillaceous beds of the western sturt plateau in the monsoonal north of the northern territory australia some sinkholes are degraded and of some antiquity though their age is not precisely known they formed during the late cenozoic following the uplift and desiccation of the latertte others are fresh and a few have formed in living memory some sinkholes may be due to collapse of the mullaman beds into voids in the underlying cambrian limestone but most have evolved wholly within the highly siliceous mullaman beds which have been dissolved or altered creating either voids or compartments filled with uncosolidated material subsequent water table lowering and collapse of the overlying beds into the low density zones caused the formation of sinkholes fractures have significantly influenced the location pattern and detailed plan shape of sinkholes sinkholes also occur within and at the margins of old drainage lines the water table stood higher in the late pleistocene bringing alkaline groundwaters into contact with the country rock a late cenozoic fall in regional water table caused slacking or disaggregation litter derived from a eucalyptus dominated woodland facilitated iron mobilisation biogenic agents may have accelerated the weathering of the silica silicates and iron oxides of which the country rock and laterite are largely composed

mechanisms of intraseasonal amplification of the cold siberian high mechanisms of intraseasonal amplification of the siberian high are investigated on the basis of composite anomaly evolution for its strongest events at each of the grid points over siberia at each location the amplification of the surface high is associated with formation of a blocking ridge in the upper troposphere over central and western siberia what may be called wave train atlantic origin type is common where a blocking ridge forms as a component of a quasi stationary rossby wave train propagating across the eurasian continent a cold air outbreak follows once anomalous surface cold air reaches the northeastern slope of the tibetan plateau it is found through the potential vorticity pv inversion technique that interaction between the upperlevel stationary rossby wave train and preexisting surface cold anomalies is essential for the strong amplification of the surface high upper level pv anomalies associated with the wave train reinforce the cold anticyclonic anomalies at the surface by inducing anomalous cold advection that counteracts the tendency of the thermal anomalies themselves to migrate eastward as surface thermal rossby waves the surface cold anomalies thus intensified in turn act to induce anomalous vorticity advection aloft that reinforces the blocking ridge and cyclonic anomalies downstream of it that constitute the propagating wave train the baroclinic development of the anomalies through this vertical coupling is manifested as a significant upward flux of wave activity emanating from the surface cold anomalies which may be interpreted as dissipative destabilization of the incoming external rossby waves

the structure dynamics and tropospheric signature of the polar annular mode 1 intraseasonal variability in the stratospheric polar vortex is intrinsically linked to concomitant tropospheric variability via the annular modes the primary mode the northern annular mode nam represents variability in the polar vortex strength while the second mode the lesser studied polar annular mode pam represents variability in the latitudinal position of the polar vortex the current study examines the structural evolution zonal mean dynamical forcing and tropospheric impact of discrete pam episodes occurring during boreal winter the analysis identifies large amplitude positive and negative pam events occurring in the absence of nam or sudden stratospheric warming events composite time evolution analyses are performed for both positive and negative pam events the onset of positive negative pam events is preceded by a weak and broad acceleration deceleration within the stratospheric polar vortex at midlatitudes during pam onset the canonical pam structure in zonal mean zonal wind develops over a 5 day period in association with robust stratosphere troposphere coupling zonal wind changes occurring during onset are induced by anomalous wave driving associated with low frequency rossby wave activity after pam onset the zonal wind anomaly features at high latitudes quickly weaken while those in the subtropics and midlatitudes persist for a period of 2 3 weeks during this time pam events provide a statistically significant impact upon the tropospheric circulation with large scale perturbations in a surface air temperature over north america and eurasia and b the structure and amplitude of the primary storm tracks

experimental delta formation in crater lakes and implications for interpretation of martian deltas 1 the morphology of delta deposits in crater lakes on mars is indicative of upstream e g flow discharge and sediment properties and downstream e g basin characteristics parameters from which the hydrological conditions at the time of formation can be inferred to investigate the influences of these parameters on delta morphology we experimentally created deltas in crater shaped basins by feeding a range of constant flow discharges over a feeder channel of various sand textures we reproduced three categorically different types of deltas including most of the types that have been identified on mars our most striking observation is that water level behavior itself a unique function of flow discharge basin size and hypsometry and basin floor permeability can explain most delta morphologies observed on mars stepped retrograding deltas formed during water level rise prograding deltas formed during water level still stand and during water level fall deltas were partially destroyed by erosion on mars numerous retrograding and prograding deltas were preserved most of them without indications of channel incisions or other fluvial modification we conclude that the main difference between a single foreset prograding delta and a multiple foreset retrograding delta is the behavior of the water level in the basin these simple delta morphologies cannot be reconciled with long duration hydrological activity because that would imply crater lake fluctuations due to inherent complex water level histories along with complex sediment delivery histories our experiments and numerical verifications demonstrate that such deltas preferentially form during one aqueous event which parsimoniously argues for short duration hydrological activity

developing wave packets in the north pacific storm track developing wave packets in the western north pacific storm track are diagnosed observationally an abrupt upstream edge to baroclinic wave activity over the western north pacific facilitates comparisons between the observational results and previous theoretical predictions on the spatiotemporal evolution of an impulse disturbance results show that surface cyclogenesis events are preceded by a sharply peaked wave packet that originates poleward of the himalaya plateau and develops rapidly across the north pacific to north america composite wave packet structure is broadly consistent with linear theory for idealized models such as eady s the longitude height structure of the mature packet reveals deep growing waves with horizontal wavelengths of approximately 4000 km near the packet peak downstream from the peak amplitude decays exponentially and wavelength decreases approximately linearly to about 2500 3000 km at the leading edge meridional potential vorticity gradients are concentrated near the tropopause in contrast to linear theory the packets show an abrupt upstream edge and no evidence of upstream development as the packet travels through the along stream variations of the pacific jet stream the packet peak and leading edge group velocity vary these accelerations change the packet length and suggest that the pacific jet may act to focus the packets a sample of north atlantic storm track events reveals similar results and suggests that the atlantic storm track is often seeded by wave packets that originate over the western north pacific ocean in contrast atlantic packets refract equatorward and become trapped on the subtropical jet to the south of himalaya plateau suggesting perhaps less potential for seeding disturbances in the pacific storm track

serpentinization and the origin of hydrogen gas in kansas hydrogen gas occurs in ten kansas wells near the mid continent rift system since 1982 two wells have yielded small amounts of gases containing an average of 29 37 mole h2 the remainder being chiefly n2 with only traces of hydrocarbons isotopic compositions for hydrogen dgrd 740 to 836 pmil imply near ambient about 10 c equilibration temperatures for the gases which are among the most deuterium depleted in nature and resemble the h2 rich gases described from ophiolites in oman isotopic values for the kansas n2 differ slightly from those of the atmosphere but not enough to rule out an atmospheric origin because they are low in ch4 and co2 expected byproducts of biogenic activity the gases are probably abiogenic in origin the existence of such gases near a major rift system containing mafic rocks and not far from known kimberlites is consistent with an origin from reactions involving fe 2 oxidation for example during serpentinization because the gases may be associated with kimberlites and deep seated rifting mantle outgassing is possible but such an origin would be difficult to reconcile with the low isotopic temperatures the h2 gases from kansas and elsewhere seem to be too low in pressure to have commercial value however neither the kansas gases nor those from other h2 occurrences have been adequately examined to assess their importance as potential resources

the romeriksporten railway tunnel drainage effects on peatlands in the lake northern puttjern area this study presents the results of an investigation of drainage effects of the romeriksporten railway tunnel on peatlands in the lake northern puttjern area drainage impacts on peatlands occurred in marked depressions reflecting faults or weakness zones in bedrocks the impacts were most evident near the tunnel trace but dry peatlands and streams were observed as far as 600 m from the tunnel trace several types of drainage effects were observed on peatland surfaces after tunnelling surface subsidence and formation of local depressions peat slides peat cracking dry peat holes and death of vegetation the effects depended clearly on peatland properties the greatest and most damaging effects were associated with thick peat layers around open water surface here lowering of the water table caused peat slides such areas will generally be extremely vulnerable to lowering of the water level the magnitude of subsidence of peatlands depends on peat thickness peat decomposition and groundwater lowering even after seven years with artificial infiltration in bedrock wells in dry periods to counteract water table lowering peat subsidence and peat slides were evident demonstrating that temporary draw down of water can result in irreversible impacts on peatlands to better be able to avoid damaging effects of tunnel drainage on environment investigations of properties of peatlands above possible tunnel traces should be integrated in the planning procedure for tunnel constructions in mires above such traces the occurrence of floating peat mats degree of peat decomposition peat thickness deliveries of water from surrounding catchments in dry periods and possible pathways of leakage through subsoils and bedrocks should be examined as basis for assessment of vulnerability of peatlands to tunnel drainage and selection of tunnel traces that evade the most vulnerable peatlands when such areas can not be avoided requirements should be set to the tightening of the tunnel to prevent damaging water draw downs in dry periods observations of drainage effects on peatland surfaces can complement hydrological information from measurements of tunnel leakages and groundwater levels and thus contribute to provide a broader picture of hydrological impacts and bedrock hydrogeology

a sawtooth like timeline for the first billion years of lunar bombardment abstract we revisit the early evolution of the moon s bombardment our work combines modeling based on plausible projectile sources and their dynamical decay rates with constraints from the lunar crater record radiometric ages of the youngest lunar basins and the abundance of highly siderophile elements in the lunar crust and mantle we deduce that the evolution of the impact flux did not decline exponentially over the first billion years of lunar history but also there was no prominent and narrow impact spike 3 9 gy ago unlike that typically envisioned in the lunar cataclysm scenario instead we show the timeline of the lunar bombardment has a sawtooth like profile with an uptick in the impact flux near 4 1 gy ago the impact flux at the beginning of this weaker cataclysm was 5 10 times higher than the immediately preceding period the nectaris basin should have been one of the first basins formed at the sawtooth we predict the bombardment rate since 4 1 gy ago declined slowly and adhered relatively close to classic crater chronology models neukum and ivanov 1994 overall we expect that the sawtooth event accounted for about one fourth of the total bombardment suffered by the moon since its formation consequently considering that 12 14 basins formed during the sawtooth event we expect that the net number of basins formed on the moon was 45 50 from our expected bombardment timeline we derived a new and improved lunar chronology suitable for use on pre nectarian surface units according to this chronology a significant portion of the oldest lunar cratered terrains has an age of 4 38 4 42 gyr moreover the largest lunar basin south pole aitken is older than 4 3 gy and therefore was not produced during the lunar cataclysm

on the value of dolines in gypsum terrains as a geological heritage an example from sivas basin turkey karst topography is a landscape shaped by the dissolution of a layer or layers of soluble bedrock usually limestone and evaporites karstification in the sivas basin turkey has sculpted a beautiful landscape with a distinctive beauty and appeal for both local inhabitants and visitors dolines are very special geological landscape features found in karst regions and the sivas basin has several giant dolines amongst its thousands of smaller dolines the basin constitutes a distinctive karst architecture with a system of collapse and or dolines and caves anyone who walks along the shores of a lake resulting from the collapse in this gypsum terrain will be amazed with the lake and rocks that surround them in this paper dolines in the gypsum terrain are evaluated and discussed according to their value as a geological heritage three main characteristics of dolines namely their scientific aesthetic and ecosystem importance are considered and discussed dolines and karstified areas as representative examples of landform types possess the three attributes for them to be considered as a geological heritage in that they demonstrate the effect of erosion on the landform geomorphic processes that are still active and a range of features characteristic of the rock unit involved

trapping of synoptic scale disturbances into the north pacific subtropical jet core in midwinter 1 over the northwestern nw pacific a subtropical jet stream develops at 30 n in midwinter as the east asian winter monsoon intensifies eddies with subweekly periods propagating through the midlatitude tropopause into the nw pacific storm track tend to be trapped into the jet core 1000 km away from a surface baroclinic zone at 40 n while lifted up by 3 km the trapping appears to weaken the interaction of the upper level eddies with the baroclinic zone thus acting against eddy amplification and thereby contributing to the midwinter minimum in the eddy activity as observed before the late 1980s since then under the reduced trapping effect by the weakened jet upper level eddies tended to propagate right above the surface baroclinic zone while strongly interacting it even in midwinter as in fall and spring this midwinter tendency acted to enhance the eddy amplification that led to the recent disappearance of the activity minimum

sagging and collapse sinkholes over hypogenic hydrothermal karst in a carbonate terrain abstract we show that clusters of karst sinkholes can occur on carbonate hypogene karst terrains unlike common doline karst of dissolution origin the studied sinkholes form mainly by sagging and collapse thermal survey osl dating and morphologic analysis during quarrying and excavations are applied to study the sinkholes at the ayyalon karst israel the thermal survey shows the spatial pattern of rising warm water plumes whose temperature is 2 c warmer than the surrounding aquifer water these plumes dissolve the limestone creating large voids and maze caves mass wasting forms surface sinkholes mainly by sagging and collapse both types of deformation often occur within the same depression lack of hydrologic connection between the surface and underground voids constrain drainage and promote rapid accumulation of colluvium dust and pedogenic clays these have filled the sinkholes up to their rim before the late holocene osl dating constrains the rate of sediment accumulation within the sinkholes the average filling rate thickness divided by elapsed time is 47 mm ka 1 for the last 53 4 ka in sinkhole 1 while in sinkhole 2 nesher ramla karst depression the rate is 61 mm ka 1 from 200 to 78 ka and 173 mm ka 1 since 78 ka between 170 and 78 ka sinkhole 2 was intensively used by middle paleolithic hominins the studied sinkholes may be considered as a type locality for hypogene sinkhole terrain on carbonate rocks

martian surface mineralogy from observatoire pour la mineralogie l eau les glaces et l activite on board the mars express spacecraft omega mex global mineral maps 1 after 2 years of operation the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer on board mars express has acquired data coverage of the martian surface with spatial resolution varying between 300 m and 4 8 km depending on the pericenter altitude of the spacecraft s elliptical orbit we report the global surface distributions of some minerals using the omega observations in the visible and near infrared vnir wavelength domains 0 35 2 5 m global maps of ferric phases mafic minerals pyroxenes and olivines and hydrated minerals have been derived from spectral parameters the limits of detection in terms of abundance for some minerals of different grain size distributions are given the distribution of pyroxenes is in general agreement with the mineral maps of previous telescopic and space observations the fe3 absorption feature in the visible wavelength region is present everywhere on the surface the spectra of the bright regions compare with anhydrous nanophase ferric oxides terrains with water bearing minerals cover a very small fraction of the martian surface olivine mg rich compositions is detected in more extensive regions of the pyroxene rich zones than previously reported olivine with higher iron content and or larger grain size 100 m is only detected in isolated areas the mineralogy of the northern low albedo regions is discussed in the light of these mineral maps chemical alteration or oxidation during extrusion producing a coating or varnish of anhydrous ferric phases over a dark basaltic surface best accounts for the vnir spectral properties of these regions although a glassy composition resulting from impact is also considered

a fracture history on enceladus provides evidence for a global ocean 1 the region surrounding the south pole of saturn s moon enceladus shows a young pervasively fractured surface that emanates enough heat to be detected by the cassini spacecraft to explain the elevated heat and eruptive icy plumes originating from large cracks informally called tiger stripes in the surface many models implicitly assume a global liquid ocean beneath the surface here we show that the fracture patterns in the south polar terrain spt of enceladus are inconsistent with contemporary stress fields but instead formed in a temporally varying global stress field related to nonsynchronous rotation of a floating ice shell above a global liquid ocean this finding increase to at least three the number of outer planet satellites likely to possess a subsurface liquid water layer

investigation of sinkholes spatial distribution using the weights of evidence method and gis in the vicinity of karapinar konya turkey abstract there are many sinkholes 182 in the vicinity of karapinar approximately 20 large sinkholes 10 m in diameter were formed within the obruk plateau between 1970 and 2012 the formation of sinkholes is the most important geological hazard in the study area because they can damage engineering structures settlements agricultural areas and eventually be a source of casualties to date no study has been conducted on the distribution of sinkholes in this region in this study the spatial distribution of the sinkholes and the factors controlling sinkhole development were studied through the use of geographical information systems using a sinkhole inventory and a spatial database containing information on the topography geology hydrogeology and land use initially 182 sinkholes were identified in the area by examining the digital elevation model produced for this study the sinkholes were verified in the field thirty two factor maps were produced to investigate their relationship with sinkholes using the weights of evidence method the sinkholes are mainly related to dissolution of the neogene age lacustrine insuyu formation consisting of limestone and clayey limestone sinkhole frequency increases in the vicinity of drainages 2000 3000 m and faults

submonthly polar vortex variability and stratosphere troposphere coupling in the arctic abstract a principal component analysis is performed to characterize intraseasonal variability in the boreal stratospheric polar vortex in contrast to previous studies the current analysis examines daily zonal mean variability within a limited spatial domain encompassing the stratospheric polar vortex the leading eofs are vertically coherent north south dipoles in the zonal mean zonal wind extending through the lower stratosphere the first mode represents variability in polar vortex strength and is highly correlated with the stratospheric northern annular mode snam the second mode the polar annular mode pam represents variability in the latitudinal position of the polar vortex and possesses a poleward retracted dipole anomaly structure composite analyses indicate that large amplitude pam events are relatively short lived 1 2 weeks compared to snam events 1 month or longer trend analyses further reveal that recent decadal trends in the boreal polar vortex project more strongly onto pam tha

lava tubes on earth moon and mars a review on their size and morphology revealed by comparative planetology abstract sinuous collapse chains and skylights in lunar and martian volcanic regions have often been interpreted as collapsed lava tubes also known as pyroducts this hypothesis has fostered a forty years debate among planetary geologists trying to define if analogue volcano speleogenetic processes acting on earth could have created similar subsurface linear voids in extra terrestrial volcanoes on earth lava tubes are well known thanks to speleological exploration and mapping in several shield volcanoes with examples showing different genetic processes inflation and overcrusting and morphometric characters on the moon subsurface cavities have been inferred from several skylights in maria smooth plains and corroborated using gravimetry and radar sounder while on mars several deep skylights have been identified on lava flows with striking similarities with terrestrial cases nonetheless the literature on this topic is scattered and often presents inaccuracies in terminology and interpretation a clear understanding of the potential morphologies and dimensions of martian and lunar lava tubes remains elusive although it is still impossible to gather direct information on the interior of martian and lunar lava tube candidates scientists have the possibility to investigate their surface expression through the analysis of collapses and skylight morphology morphometry and their arrangement and compare these findings with terrestrial analogues in this review the state of the art on terrestrial lava tubes is outlined in order to perform a morphological and morphometric comparison with lava tube candidate collapse chains on mars and the moon by comparing literature and speleological data from terrestrial analogues and measuring lunar and martian collapse chains on satellite images and digital terrain models dtms this review sheds light on tube size depth from surface eccentricity and several other morphometric parameters among the three different planetary bodies the dataset here presented indicates that martian and lunar tubes are 1 to 3 orders of magnitude more voluminous than on earth and suggests that the same processes of inflation and overcrusting were active on mars while deep inflation and thermal entrenchment was the predominant mechanism of emplacement on the moon even with these outstanding dimensions with total volumes exceeding 1 billion of m3 lunar tubes remain well within the roof stability threshold the analysis shows that aside of collapses triggered by impacts tectonics most of the lunar tubes could be intact making the moon an extraordinary target for subsurface exploration and potential settlement in the wide protected and stable environments of lava tubes

new insights into the genesis of the miocene collapse structures of the island of gozo malta central mediterranean sea the large palaeosinkholes located in the nw of gozo central mediterranean sea malta offer excellent exposures that provide information on the geometry and kinematics of large karst related collapse structures detailed geological analysis of these peculiar palaeosinkholes indicates that deep seated evaporite dissolution is the most feasible hypothesis to explain their formation according to the following evidence 1 several structures have been formed by progressive foundering of cylindrical blocks with limited internal deformation as revealed by the synsedimentary subsidence recorded by their miocene sedimentary fill this subsidence mechanism is more compatible with interstratal dissolution of evaporites than karstification and cave development in limestone formations 2 the dimensions and deformation style of the palaeosinkholes are similar to those of other collapse structures related to deep seated dissolution of salt bearing evaporites 3 the arcuate monocline associated with some of these collapse structures is also a characteristic feature of subsidence related to dissolution of evaporites however no major evaporite formations have been documented so far in the subsurface of the malta platform supplementary material detailed descriptions of the collapse structures of the island of gozo malta central mediterranean sea are available at www geolsoc org uk sup18808

hydrous minerals on mars as seen by the crism and omega imaging spectrometers updated global view 1 the surface of mars has preserved the record of early environments in which its basaltic crust was altered by liquid water these aqueous environments have survived in the form of hydrological morphologies and alteration minerals including clays and hydrated salts because these minerals probe on earth aqueous environments compatible with biotic activity understanding their formation processes on mars is of great exobiological relevance and also offers insight into earth s now erased ancient water environments using remote sensing we conducted a large scale investigation of the distribution composition age and geomorphic settings of hydrous minerals on mars providing a sharpened global view of the early aqueous environments and their evolution with time aqueous alteration seems to have produced clays on a planetary scale but these are found to be restricted to the oldest observable terrains on mars 4 gyr however very diverse aqueous environments have also been found which suggest widespread complex aqueous settings from the surface to kilometric depths and spanning over 1 gyr by building a robust statistical sample of detections the global trends inferred here attempt to provide a broad view of our current understanding of hydrous minerals on mars and provide context for more localized in depth analyses collectively these trends suggest that at least transient conditions have existed on mars which may have been favorable for pre biotic to biotic activity

hidden sinkholes and karst cavities in the travertine plateau of a highly populated geothermal seismic territory tivoli central italy abstract sinkholes and other karst structures in settled carbonate lands can be a significant source of hazard for humans and human works acque albule the study area of this work is a plio pleistocene basin near rome central italy superficially filled by a large and thick deposit of late pleistocene thermogene travertine human activities blanket large portions of the flat territory covering most evidence from geological surface processes and potentially inducing scientists and public officials to underestimate some natural hazards including those connected with sinkholes to contribute to the proper assessment of these hazards a geomorphologic study of the basin was performed using digital elevation models dems recent aerial photographs and field surveys historical material such as old aerial photographs and past geomorphologic studies both pre dating the most part of quarrying and village building was also used together with memories of the elderly population this preliminary study pointed out the presence of numerous potentially active sinkholes that are at present largely masked by either quarrying or overbuilding where this first study pointed out the apparent absence of sinkholes in areas characterized by high density of buildings a detailed subsurface study was performed using properly calibrated electrical resistivity tomography ert and dynamic penetration measurements dpsh together with some borehole logs made available from the local municipality this second study highlighted the presence of sinkholes and caves that are this time substantially hidden to the resolution of standard methods and materials such as aerial photographs dems and field surveys active sinkhole subsidence in the acque albule basin may explain at least in part the frequent damages that affect numerous buildings in the area the main conclusion from this study is that the mitigation of sinkhole hazard in highly populated areas has to pass through a thorough search of hidden sinkholes that can be masked by the anthropocenic molding and blanketing of the territory for these purposes data from historical pre anthropocene documents as well as where possible subsurface investigations are fundamental

cover collapse sinkholes in the tournaisis area southern belgium abstract in the tournaisis area southern belgium cover collapse sinkholes have been reported since the beginning of this century in this area the relatively flat lying carboniferous limestone is overlain by an unconformable mesocenozoic cover recent research has shown that these sinkholes developed from reactivated paleokarsts the intensive pumping for domestic and industrial water supply combined with the dewatering due to deep limestone quarries operations resulted in the lowering of groundwater levels this triggered the reactivation of paleokarstic systems and thus the occurrence of cover collapse sinkholes these sudden and unexpected collapses have already had major impacts in the region in 1977 about thirty sinkholes opened up along the escaut river downstream from the city of tournai as a consequence the groundwater was polluted by an extensive loss of river water into the carboniferous aquifer more recently a house and industrial facilities were severely damaged by such cover collapse sinkholes in this context a geoharzard map would be a valuable tool as far as regional development is concerned this points at the importance to develop methods to locate and characterize hidden paleokarsts a study site has been chosen in an area where sinkholes have been opening up for about ten years a geophysical survey of the site which included electrical resistance mapping of the area has shown weakness lineaments these lineaments are parallel to a main fault affecting the region

silica deposits in the nili patera caldera on the syrtis major volcanic complex on mars the martian surface features abundant volcanoes and evidence for past liquid water extant or relict martian volcanic hydrothermal systems have therefore been sought in the pursuit of evidence for habitable environments the mars exploration rover spirit detected deposits highly enriched in silica with accessory minerals suggesting formation by hydrothermal leaching of basaltic rocks by low ph solutions however extensive erosion has obscured the context of the formation environment of these deposits silica deposits have also been identified remotely but also with limited contextual clues to their formation aqueous alteration products of basalt and volcanic ash are the most likely sources here we report the detection from orbit of hydrated silica deposits on the flanks of a volcanic cone in the martian syrtis major caldera complex near infrared observations show dozens of localized hydrated silica deposits as a result of the morphology of these deposits and their location in and around the cone summit we suggest that the deposits were produced by a volcanically driven hydrothermal system the cone and associated lava flows post date early hesperian volcano formation we conclude that if a relict hydrothermal system was associated with the silica deposits it may preserve one of the most recent habitable microenvironments on mars

assessment of cover collapse sinkholes in sw sardinia italy the sw part of sardinia has been afflicted in recent years by several cover collapse sinkholes mostly occurring in low density population areas the study area that lies in the iglesiente sulcis region is characterized by the cropping out of the palaeozoic basement related to the south european hercynian chain covered with tertiary quaternary sediments the main rock types that crop out are palaeozoic metasandstones metadolostones metalimestones shales and metaconglomerates and tertiary quaternary fluvial lacustrine continental sediments the combined application of several geophysical techniques integrated with boreholes and geotechnical as well as hydrogeological measurements proved to be very useful and promising in defining in detail the geological context in which each sinkhole has formed moreover the gravity method even when used alone proved to be very effective in detecting the regional geological structures to which sinkholes are related eventually the historical analysis of phenomena the geological knowledge of the iglesiente sulcis area and the results of properly designed geophysical surveys allows the most probable areas for cover collapse sinkholes to occur in the future to be determined in fact this research pointed out that the depth of the sediment covered palaeozoic bedrock is one of the major constraints in delimiting hazardous areas leading to the construction of a preliminary hazard map this map shows a belt of high risk and also suggests the areas in which further geophysical and geotechnical investigations should be carried out to estimate the depth of the bedrock cover collapse sinkholes forming on karst terrains covered with more or less loose sediments have been described from many areas of the world beck 1986 newton 1987 twidale 1987 soriano simon 1995 kaufmann quinif 1999 salvati sasowsky 2002 waltham et al 2005 these phenomena are often triggered by human intervention especially by water extraction and modifications in surface drainage patterns and are further enhanced by the increasing occurrence of extreme meteorological events similar hazards have been occurring in several areas of sw sardinia italy since the early 1990s with increasing frequency balia et al 2001 de waele muntoni 2001 one of the most interesting and impressive sinkholes formed in october 1998 in the cixerri valley at guardia su merti only 50 m away from the main railway that connects cagliari to iglesias balia et al 2001 other major sinkholes occurred 1 year later some kilometres south in an area named planu francau close to the main road from villamassargia to carbonia fadda fais 2002 de waele et al 2003 the increase in the formation of these sinkholes has led local and regional stakeholders and decision makers to consider studying these phenomena that could seriously endanger local infrastructures and human lives in the near future geological setting cover collapse sinkholes have been reported from several covered karst areas in sw sardinia near the villages of carbonia iglesias narcao sant anna arresi and villamassargia balia et al 2001 de waele muntoni 2001 fadda fais 2002 de waele et al 2003 the study area fig 1 is characterized by the outcrops of palaeozoic metasediments ranging in age from early cambrian to upper carboniferous covered with tertiary quaternary sediments and volcanic rocks from bottom to top the palaeozoic sequence is composed of metasandstones shales oolithic limestones calcareous sandstones dolostones intensely karstified limestones and shales pillola 1989 bechstadt boni 1996 carmignani et al 2001 postpalaeozoic sedimentation starts only during the lower tertiary with marly limestones marls and mudstones with coal seams of eocene age murru matteucci 2002 sedimentation continues with alluvial and lacustrine deposits composed of conglomerates and sandstones of the cixerri formation of middle eocene upper oligocene age carmignani et al 2004 immediately south of villamassargia these sediments are overlain with andesites and basaltic andesites of oligocene lower miocene age beccaluva et al 1985 from parise m gunn j eds natural and anthropogenic hazards in karst areas recognition analysis and mitigation geological society london special publications 279 47 57 doi 10 1144 sp279 5 0305 8719 07 15 00 the geological society of london 2007 fig 1 geological map of the study area and surrounding region f ardau et al 48

the annual cycle of northern hemisphere storm tracks part ii regional detail abstractin part i of this study the annual cycle of the northern hemisphere storm tracks was investigated using feature tracking and eulerian variance based diagnostics applied to both the vortici

alluvial dolines in the central ebro basin spain a spatial and developmental hazard analysis abstract alluvial dolines are abundant in quaternary terraces and pediments overlying neogene gypsum in the zaragoza area central ebro basin spatial analysis and experimental simulation show that sulphate content in the groundwater grain size of the detrital cover topography of the tertiary quaternary boundary annual variation of the water table and thickness of the detrital cover are the main factors controlling their development taking into account these variables a theoretical spatial hazard model has been elaborated expressed as a mathematical equation and a hazard map both experiments and field data show a high correspondance between two basic mechanisms of evacuation and subsidence dragging slow subsidence and collapse of cavities and two basic types of morphology and internal structure of dolines basin doline funnel structure and well doline vault structures respectively a genetic classification of dolines and some evolutionary patterns based on these criteria are developed historical changes observed in doline distribution as well as field surveys of urban damage and microtopographic profiles allow us to evaluate the present day activity of dolines local subsidence rates measured in urban areas range from 2 5 to 10 cm year although doline generation and reactivation in the whole area tend to be compensated by filling by human activity

a small s mif signal in martian regolith pyrite implications for the atmosphere abstract the past martian atmosphere is often compared to the archean earth s as both were dominated by co2 rich and o2 poor chemistries archean earth rocks preserve mass independently fractionated sulfur isotopes s mif non zero 33s and 36s originating from photochemistry in an anoxic atmosphere thus martian crustal rocks might also be expected to preserve a s mif signature providing insights into past atmospheric chemistry we have used secondary ion mass spectrometry sims to investigate in situ the sulfur isotope systematics of nwa 8171 paired to nwa 7034 a martian polymict breccia containing pyrite that formed through hydrothermal sulfur addition in a near surface regolith setting in this meteorite pyrite grains have a weighted mean of 33s of 0 14 0 08 and 36s 0 70 0 40 2 s e m so the s mif signature is subtle sulfur isotope data for four additional shergottites yield 33s values that are not resolvable from zero as in previous studies of shergottites at first glance the result for the polymict breccia might seem surprising but no martian meteorite yet has yielded a s mif signature akin to the large deviations seen on earth we suggest that s mif bearing aerosols h2so4 and s8 were produced when volcanic activity pushed a typically oxidising martian atmosphere into a reduced state after rain out of these aerosols s8 would tend to be oxidised by chlorate dampening the s mif signal which might be somewhat retained in the more abundant photolytic sulfate then in the regolith mixing of aqueous surface derived sulfate with igneous sulfide the latter with zero mif to form the abundant pyrite seen in nwa 8171 would further dampen the s mif signal nonetheless the small negative 33s anomalies seen in martian meteorites imply that volcanic activity was sufficient to produce a reducing atmosphere at times this volcanically driven atmospheric evolution would tend to produce high levels of carbonyl sulfide ocs given that ocs is a relatively long lived strong greenhouse gas the s mif signal implies that volcanism periodically generated warmer conditions perhaps offering an evidence based solution to the young wet mars paradox

fluid mixing and the deep biosphere of a fossil lost city type hydrothermal system at the iberia margin subseafloor mixing of reduced hydrothermal fluids with seawater is believed to provide the energy and substrates needed to support deep chemolithoautotrophic life in the hydrated oceanic mantle i e serpentinite however geosphere biosphere interactions in serpentinite hosted subseafloor mixing zones remain poorly constrained here we examine fossil microbial communities and fluid mixing processes in the subseafloor of a cretaceous lost city type hydrothermal system at the magma poor passive iberia margin ocean drilling program leg 149 hole 897d brucite calcite mineral assemblages precipitated from mixed fluids ca 65 m below the cretaceous paleo seafloor at temperatures of 31 7 4 3 c within steep chemical gradients between weathered carbonate rich serpentinite breccia and serpentinite mixing of oxidized seawater and strongly reducing hydrothermal fluid at moderate temperatures created conditions capable of supporting microbial activity dense microbial colonies are fossilized in brucite calcite veins that are strongly enriched in organic carbon up to 0 5 wt of the total carbon but depleted in 13c 13ctoc 19 4 we detected a combination of bacterial diether lipid biomarkers archaeol and archaeal tetraethers analogous to those found in carbonate chimneys at the active lost city hydrothermal field the exposure of mantle rocks to seawater during the breakup of pangaea fueled chemolithoautotrophic microbial communities at the iberia margin possibly before the onset of seafloor spreading lost city type serpentinization systems have been discovered at midocean ridges in forearc settings of subduction zones and at continental margins it appears that wherever they occur they can support microbial life even in deep subseafloor environments

orbital evidence for more widespread carbonate bearing rocks on mars carbonates are key minerals for understanding ancient martian environments because they are indicators of potentially habitable neutral to alkaline water and may be an important reservoir for paleoatmospheric co 2 previous remote sensing studies have identified mostly mg rich carbonates both in martian dust and in a late noachian rock unit circumferential to the isidis basin here we report evidence for older fe and or ca rich carbonates exposed from the subsurface by impact craters and troughs these carbonates are found in and around the huygens basin northwest of hellas in western noachis terra between the argyre basin and valles marineris and in other isolated locations spread widely across the planet in all cases they cooccur with or near phyllosilicates and in huygens basin specifically they occupy layered rocks exhumed from up to 5 km depth we discuss factors that might explain their observed regional distribution arguments for why carbonates may be even more widespread in noachian materials than presently appreciated and what could be gained by targeting these carbonates for further study with future orbital or landed missions to mars

role of biomineralization as an ultraviolet shield implications for archean life cyanobacteria isolated from the krisuvik hot spring iceland were mineralized in an iron silica solution and irradiated with high levels of ultraviolet light analysis of the rates of photosynthesis chlorophyll a content and phycocyanin autofluorescence revealed that these mineralized bacteria have a marked resistance to uv compared to nonmineralized bacteria naturally occurring sinters composed of iron silica biominerals collected from

giant solution subsidence structure in the western mediterranean related to deep substratum dissolution terra nova 24 181 188 2012 abstract sinkholes are frequently observed where soluble rocks are present in meteoritic recharge areas or when subsurface dissolution causes ground collapse seismic profiles on the inner shelf of the gulf of lions w mediterranean display a giant atypical sub circular structure up to 800 m thick and 2 km wide it is characterized by down warped internal seismic reflections forming a concave v shaped depression rooted in the substratum most likely carbonated this structure is interpreted as a poly phased solution subsidence collapse structure of plio quaternary age the last phase of deformation probably occurred during the last sea level low stand phase the mechanism proposed for the creation of this structure is collapse dissolution of the soluble substratum as a result of a combination of several possible factors including pre existing deep messinian palaeo karst with active groundwater flows during plio quaternary lowstands and deep rooted acidic fluids ascending through the substratum

a serpentinite hosted ecosystem the lost city hydrothermal field the serpentinite hosted lost city hydrothermal field is a remarkable submarine ecosystem in which geological chemical and biological processes are intimately interlinked reactions between seawater and upper mantle peridotite produce methane and hydrogen rich fluids with temperatures ranging from 40 to 90 c at ph 9 to 11 and carbonate chimneys 30 to 60 meters tall a low diversity of microorganisms related to methane cycling archaea thrive in the warm porous interiors of the edifices macrofaunal communities show a degree of species diversity at least as high as that of black smoker vent sites along the mid atlantic ridge but they lack the high biomasses of chemosynthetic organisms that are typical of volcanically driven systems