river stage influences on uranium transport in a hydrologically dynamic groundwater surface water transition zone a well field within a uranium u plume in the groundwater surface water transition zone was monitored for a 3 year period for water table elevation and dissolved solutes the plume discharges to the columbia river which displays a dramatic spring stage surge resulting from snowmelt groundwater exhibits a low hydrologic gradient and chemical differences with river water river water intrudes the site in spring specific aims were to assess the impacts of river intrusion on dissolved uranium uaq specific conductance spc and other solutes and to discriminate between transport geochemical and source term heterogeneity effects as a result of water table elevation fluctuations river water intrusion and changes in groundwater flow directions time series trends for uaq and spc were found to be complex and displayed large temporal and well to well variability the wells were clustered into subsets exhibiting common behaviors resulting from the intrusion dynamics of river water and the location of source terms hot spots in uaq varied in location with increasing water table elevation through the combined effects of advection and source term location heuristic reactive transport modeling with pflotran demonstrated that mobilized uaq was transported between wells and source terms in complex trajectories and was diluted as river watermore entered and exited the groundwater system moreover while uaq time series concentration trends varied significantly from year to year as a result of climate caused differences in the spring hydrograph common and partly predictable response patterns were observed that were driven by water table elevation and the extent and duration of river water intrusion less

cracks and fins in sulfate sand evidence for recent mineral atmospheric water cycling in meridiani planum outcrops gypsum dunes at white sands national monument new mexico provide an excellent analog to sulfate rich eolian outcrops on meridiani planum mars as characterized by the rover opportunity numerous outcrops imaged by opportunity contain polygonal cracks that crosscut bedding and extend across most surfaces of boulders some of these cracks are associated with millimeter thick platy fins that protrude as much as a few centimeters above outcrops similar cracks crosscut bedding at white sands on erosional stoss slopes and in pedestals of cemented dune sand the cracks at white sands form in response to cementation of damp gypsum sand followed by contraction due to dehydration during warm seasons cracked sand is dry and cracks rarely grow although some may form after rainstorms two types of fins form along cracks and differentially eroded laminae white fins represent subsurface differential cementation along cracks followed by differential erosion tan fins form due to cementation of crack edges and laminae on exposed dune surfaces wind blown sediment adheres to damp tan fins similar processes may be important for crack and fin formation in meridiani planum outcrops implying recent water cycling between sulfate outcrops and the martian atmosphere

calcium sulfate veins characterized by chemcam curiosity at gale crater mars the curiosity rover has analyzed abundant light toned fracture fill material within the yellowknife bay sedimentary deposits the chemcam instrument coupled with mastcam and chemcam remote micro imager images was able to demonstrate that these fracture fills consist of calcium sulfate veins many of which appear to be hydrated at a level expected for gypsum and bassanite anhydrite is locally present and is found in a location characterized by a nodular texture an intricate assemblage of veins crosses the sediments which were likely formed by precipitation from fluids circulating through fractures the presence of veins throughout the entire similar to 5 m thick yellowknife bay sediments suggests that this process occurred well after sedimentation and cementation lithification of those sediments the sulfur rich fluids may have originated in previously precipitated sulfate rich layers either before the deposition of the sheepbed mudstones or from unrelated units such as the sulfates at the base of mount sharp the occurrence of these veins after the episodes of deposition of fluvial sediments at the surface suggests persistent aqueous activity in relatively nonacidic conditions

high resolution thermal inertia derived from the thermal emission imaging system themis thermal model and applications 1 thermal inertia values at 100 m per pixel are determined using nighttime temperature data from the thermal emission imaging system themis on the mars odyssey spacecraft producing the highest resolution thermal inertia data set to date themis thermal inertia values have an overall accuracy of 20 a precision of 10 15 and are consistent with both thermal emission spectrometer orbital and miniature thermal emission spectrometer surface thermal inertia values this data set enables the improved quantification of fine scale surface details observed in high resolution visible images in the tharsis region surface textures and crater rims observed in visible images have no corresponding variation in the themis thermal inertia images indicating that the dust mantle is pervasive at themis scales and is a minimum of a few centimeters and up to 1 2 m thick the thermal inertia of bed form material indicates particle diameters expected for aeolian sediments and these materials are likely currently saltating variations in the thermal inertia within interior layered deposits in hebes chasma can be distinguished and the thermal inertia is too low to be consistent with bedrock or a lava flow thus a secondary emplacement of volcanic material or a volcanic ash deposit is a more likely method of formation higher resolution themis thermal inertia enables the identification of exposed bedrock on the martian surface in nili patera and ares vallis bedrock material corresponds to distinct compositional and morphologic surfaces indicating that a specific unit is exposed and is likely currently being kept free of unconsolidated material by aeolian processes

origin of giant martian polygons extensive areas of the martian northern plains in utopia and acidalia planitiae are characterized by polygonal terrane polygonal terrane consists of material cut by complex troughs defining a pattern resembling mudcracks columnar joints or frost wedge polygons on earth however the martian polygons are orders of magnitude larger than these potential earth analogues leading to severe mechanical difficulties for genetic models based on simple analogy arguments plate bending and finite element models indicate that shrinkage of desiccating sediment or cooling volcanics accompanied by differential compaction over buried topography can account for the stresses responsible for polygon troughs as well as the large size of the polygons although trough widths and depths relate primarily to shrinkage the large scale of the polygonal pattern relates to the spacing between topographic elevations on the surface buried beneath polygonal terrane material geological relationships favor a sedimentary origin for polygonal terrane material but our model is not dependent on the specific genesis our analysis also suggests that the polygons must have formed at a geologically rapid rate

polygonal cracks in bedrock on earth and mars implications for weathering polygonal crack systems with domal microrelief imaged by the mars exploration rover mer opportunity show remarkable similarity to terrestrial crack systems developed on outcrop surfaces study of jurassic navajo sandstone surfaces show development of crack systems in relatively isotropic host rock as a result of tensile weathering stresses these terrestrial analogs are utilized to understand potential weathering processes on mars

small scale polygonal features on mars seasonal thermal contraction cracks in permafrost a time dependent viscoelastic model of thermal stress in martian ice rich permafrost is developed to test the hypothesis that small scale polygonal features observed from orbit and by the viking lander 2 are the result of thermal contraction cracking as commonly occurs in terrestrial permafrost results indicate that significant tensile stress occurs in martian ice rich permafrost as a result of seasonal cycles in the ground temperature using conservative rheological parameters appropriate for ice at low temperatures tensile stresses poleward of about 20 to 30 latitude easily exceed the tensile strength assumed to be 2 to 3 mpa and fractures should readily form in the equatorial regions special conditions may allow tensile stresses to approach the tensile strength these results support a thermal contraction origin of observed small scale polygonal features and emphasize the utility of these features as valuable morphological indicators of ground ice

characteristics and origin of polygonal terrain in southern utopia planitia mars results from mars orbiter laser altimeter and mars orbiter camera data giant polygons on mars with several kilometers in diameter were first observed in mariner 9 and viking orbiter images and their origin formation and evolution have remained enigmatic since that time new data obtained by the mars orbiter laser altimeter mola and the mars orbiter camera moc on board the mars global surveyor spacecraft now permit analysis of topography and morphology of the polygonal terrain in unprecedented detail mola data show that 1 giant polygonal terrain in utopia is located at the lower slopes of a basin structure that is the utopia basin 2 the onset of polygonal terrain in utopia is close to the same elevation in several profiles and lies at about the same elevation as a terrace which was interpreted as a shore line of an ancient body of standing water within the utopia basin proper 3 polygonal terrain occurs over a wide range of elevations on regional slopes of 0 1 4 the depths of the troughs range from 5 m to 115 m averaging about 30 m and tend to be greater toward the center of the utopia basin 5 the mean width of polygonal troughs is of the order of 2 km ranging from 0 5 to 7 5 km data from the mars orbiter camera moc indicate that 1 the troughs are generally broad graben like features with varying morphologies i e terraces and lobateness and dimensions widths and depths 2 trough morphology has been modified by aeolian processes 3 polygonal troughs are weakly interconnected at moc resolutions and there are no smaller polygons observed within the giant polygons 4 circular depressions which are probably related to subsurface collapse sometimes occur at the bottoms of polygonal troughs 5 small scale polygonal terrain on the ejecta blankets of young craters with fluidized ejecta in the investigated area exhibits different characteristics i e smaller size presence of rims greater degree of interconnections than giant polygons in the viking images we see that 1 old impact craters are increasingly buried with younger materials toward the basin center and that 2 a large number of superposed impact craters on polygonal terrain exhibit distinctive ejecta morphologies such as rampart ejecta blankets and single and double lobate ejecta blankets mola and moc observations are consistent with the formation of polygonal terrain in the area of a former standing body of water but polygon size seems too large to be readily accounted for by desiccation or freezing processes alone on the basis of the observed characteristics we propose that the giant polygons are primarily of tectonic origin being caused by uplift of the floor of the utopia basin there are several candidates for the cause of uplift 1 the removal of the load representing former standing bodies of water water thickness estimated for the utopia basin is about 1 km in this scenario removal of this load comparable to loads placed on terrestrial continental lithosphere by the laurentide and scandinavian ice sheets by loss of the water or ice could cause uplift of the floor and polygon formation 2 the freezing and expansion of residual water buried by sediments or in the near subsurface or 3 a combination of these from the discussion of alternative models in the light of the mola and moc data we conclude that formation of giant polygons by tectonic uplift of the basin floor is most likely and deserves further investigation

tepees modern southern australia and ancient permian texas and new mexico a comparison abstract tepee structures are forming today about the edges of a number of holocene groundwater lakes coastal salinas in the coastal zone of south australia tepees form by the groundwater induced deformation of an extensive sheet of fenestral limestone known as a veneer boundstone underlying the veneer boundstone is an extremely porous aquifer known as a boxwork boundstone areas of groundwater resurgence in these salinas are characterized by an association of tepee structures boxwork boundstones and stromatolites the tepees in these salinas are termed groundwater or boxwork tepees to emphasize the importance of resurging groundwater in their formation preliminary studies of tepee structures in the back reef strata of guadalupian age in the guadalupe mountains of west texas and new mexico has shown that these tepees are also groundwater tepees such tepee structures in the guadalupe mountains are often associated with remnants of an underlying boxwork boundstone and or an underlying sandy palaeoaquifer they are tepees which formed in zones of groundwater resurgence at a time when the nearby reef was a subaerially exposed barrier limestone sheets composed of vadose pisolites were deformed coincident with tepee formation this association implies that vadose pisolites like tepees formed in areas of periodic groundwater resurgence characterized by a complex schizohaline hydrological regime

spatial relationships between patterned ground and ground ice detected by the neutron spectrometer on mars 1 patterned grounds like polygonal features are the signature of climatic effects in periglacial regions on earth identifying similar features on mars is important for an understanding of the past martian climate in this study we mapped fresh patterned landforms from the systematic analysis of mars orbiter camera high resolution images we show that most of them are distributed at latitudes poleward of 55 making a climatic control likely this distribution correlates to the distribution of ground ice detected by the neutron spectrometer aboard mars odyssey this correlation is likely the consequence of the neutron spectrometer detecting ice no deeper than about 1 m patterned ground formation requires ice in this range of depth because these features are triggered by the propagation of a thermal wave that is driven by seasonal or diurnal changes in insolation which affect the temperature in the uppermost ground layers sublimation seems to play a role in the shaping of many of the small patterns observed at latitudes between 55 and 70 no widespread polygonal features are correlated to the equatorial regions where hydrogen is detected by the neutron spectrometer

a habitable fluvio lacustrine environment at yellowknife bay gale crater mars the curiosity rover discovered fine grained sedimentary rocks which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy this aqueous environment was characterized by neutral ph low salinity and variable redox states of both iron and sulfur species carbon hydrogen oxygen sulfur nitrogen and phosphorus were measured directly as key biogenic elements by inference phosphorus is assumed to have been available the environment probably had a minimum duration of hundreds to tens of thousands of years these results highlight the biological viability of fluvial lacustrine environments in the post noachian history of mars

resurfacing time of terrestrial surfaces by the formation and maturation of polygonal patterned ground 1 to help interpret the polygonal patterned ground on mars we present recent findings about a similar form of patterned ground in a particularly cold and arid region on earth the dry valleys of antarctica in this region distinct arrays of interconnected polygons which we refer to herein simply as patterned ground characterize many surfaces reflecting a subsurface network of interconnected subvertical wedges of sand that grow incrementally as sand progressively fills soil fractures the fractures form initially as thermoelastic stresses arise during periods of rapid cooling of frozen ground and they continue to open and close in response to thermal cycles we describe the initiation and maturation of the patterned ground using data for the growth of sand wedges and for the evolution of crack patterns and microrelief over time scales ranging up to 106 years

paleoclimate of mars as captured by the stratigraphic record in gale crater a kilometers thick sedimentary sequence in gale crater exhibits stratigraphic changes in lithology that are consistent with transitions in aqueous and climatic conditions purported to be global in scale the sequence is divided into two formations where the lower formation exhibits a net transition in mineralogy from clay sulfate to sulfate oxide assemblages and is separated from the overlying upper formation by an erosional unconformity superposition and crater counts suggest strata in the lower formation lie along the noachian hesperian time stratigraphic boundary whereas beds in the upper formation which lack signatures indicative of clay minerals or sulfates are thinner more regularly spaced and clearly younger the observed stratigraphic trends are consistent with the rocks at gale crater recording a global transition from a climate favorable to clay mineral formation to one more favorable to forming sulfates and other salts

discovery of columnar jointing on mars we report on the discovery of columnar jointing in marte valles mars these columnar lavas were discovered in the wall of a pristine 16 km diameter impact crater and exhibit the features of terrestrial columnar basalts there are discontinuous outcrops along the entire crater wall suggesting that the columnar rocks covered a surface area of at least 200 km 2 assuming that the rocks obliterated by the impact event were similarly jointed we also see columns in the walls of other fresh craters in the nearby volcanic plains of elysium planitia amazonis planitia which include marte vallis and in a well preserved crater in northeast hellas

a review of the origin and setting of tepees and their associated fabrics carbonate hardgrounds often occur at the surface of shallow subtidal to supratidal lacustrine and subaerial carbonate shelf sediments these are commonly disrupted and brecciated when the surface area of these crusts increases in the subtidal environment megapolygons form when cementation of the matrix causes the surface area of the hardgrounds to expand similar megapolygons form in the supratidal lacustrine and subaerial settings when repeated incremental fracturing and fracture fill by sediment and or cement also causes the area of the hardgrounds to expand the arched up antiform margins of expansion megapolygons are known as tepees the types of tepees found in the geological record include 1 submarine tepees which form in shallow carbonate saturated waters where fractured and bedded marine grainstones are bound by isopachous marine phreatic acicular and micritic cements the surfaces of these brecciated crusts have undergone diagenesis and are bored unlike tepees listed below they contain no vadose pisolites or gravity cements 2 peritidal and lacustrine tepees are formed of crusts characterized by fenestral pisolitic and laminar algal fabrics this similarity in fabric makes these tepees of different origins difficult to separate peritidal tepees occur where the marine phreatic lens is close to the sediment surface and the climate is tropical they are associated with fractured and bedded tidal flat carbonates their fracture fills contain geopetal asymmetric travertines of marine vadose origin and or marine phreatic travertines and or terra rossa sediments the senile form of these peritidal tepees are cut by labyrinthic dissolution cavities filled by the same material lacustrine tepees form in the margins of shallow salinas where periodic groundwater resurgence is common they include groundwater tepees which form over evaporitic boxwork carbonates and extrusion tepees which also form where periodic groundwater resurgence occurs at the margins of shallow salinas but the dominant sediment type is carbonate mud these latter tepee crusts are coated and crosscut by laminated micrite the laminae extend from the fractures downward into the underlying dolomitic micrite below the crust both peritidal and lacustrine tepees form where crusts experience alternating phreatic and vadose conditions in time intervals of days to years cement morphologies reflect this and the crusts often contain gravitational meniscus vadose cements as well as phreatic isopachous cement rinds 3 caliche tepees which are developed within soil profiles in a continental setting they are formed by laminar crusts which contain pisolites and fractures filled by micritic laminae microspar spar and terra rossa most of the cements are gravitational and or meniscoid in ancient carbonates when their cementation and diagenetic fabric can be interpreted tepee structures can be used as environmental indicators they can also be used to trace the evolution of the depositional and hydrological setting

volumetric estimates of ancient water on mount sharp based on boxwork deposits gale crater mars while the presence of water on the surface of early mars is now well known the volume distribution duration and timing of the liquid water have proven difficult to determine this study makes use of a distinctive boxwork rich sedimentary layer on mount sharp to map fluid based cementation from orbital imagery and estimate the minimum volume of water present when this sedimentary interval was formed the boxwork structures on mount sharp are decameter scale light toned polygonal ridges that are unique compared to previous observations of martian fractured terrain because they are parallel sided ridges with dark central linear depressions this texture and the sedimentary setting strongly imply that the ridges are early diagenetic features formed in the subsurface phreatic groundwater zone high resolution orbital imagery was used to map the volume of light toned cemented ridges based on the cemented volume a minimum of 5 25 105 m 3 of cement was deposited within the fractures using a brine composition based on observations of other martian cements and modeling the degree of evaporation each volume of cement requires 800 6700 pore volumes of water so the mapped boxwork ridge cements require a minimum of 0 43 km 3 of water this is a significant amount of groundwater that must have been present at the 3620 m level 1050 m above the current floor of gale crater providing both a new constraint on the possible origins of mount sharp and a possible future science target for the curiosity rover where large volumes of water were present and early mineralization could have preserved a once habitable environment

potential desiccation cracks on mars a synthesis from modeling analogue field studies and global observations potential desiccation polygons pdps are polygonal surface patterns that are a common feature in noachian to hesperian aged phyllosilicate and chloride bearing terrains and have been observed with size scales that range from cm wide by current rovers to 10s of meters wide the global distribution of pdps shows that they share certain traits in terms of morphology and geologic setting that can aid identification and distinction from fracturing patterns caused by other processes they are mostly associated with sedimentary deposits that display spectral evidence for the presence of fe mg smectites al rich smectites or less commonly kaolinites carbonates and sulfates in addition pdps may indicate paleolacustrine environments which are of high interest for planetary exploration and their presence implies that the fractured units are rich in smectite minerals that may have been deposited in a standing body of water a collective synthesis with new data particularly from the hirise camera suggests that desiccation cracks may be more common on the surface of mars than previously thought a review of terrestrial research on desiccation processes with emphasis on the theoretical background field studies and modeling constraints is presented here as well and shown to be consistent with and relevant to certain polygonal patterns on mars

crater floor polygons desiccation patterns of ancient lakes on mars 1 global mapping of intermediate size 100 200 m polygonal troughs occurring mainly in impact crater floors was carried out using high resolution images from spacecraft currently orbiting mars earlier works have classified these polygonal networks as periglacial features on account of their apparent occurrence at higher latitudes and morphological similarities to thermal contraction polygons tcps crater floor polygons cfps have diameters ranging from 15 to 350 m they morphologically resemble terrestrial tcps and desiccation cracks their size distribution however is significantly different from that of tcps that are ubiquitous in the high latitudes an analytical model based on fracture mechanics reveals that under current climatic conditions the maximum fracture spacing attainable by thermal stresses alone is 75 m at the most more reasonable values fall within 18 and 22 m which is the range for tcps on mars as a result we propose desiccation to be a dominant mechanism for the formation of cfps without ruling out thermal contraction as a possible contributor in some cases this implies that lakes or water rich sediments occupied the craters in the past many such aqueous environments have no apparent external source of water and thus hydrothermal processes occurring shortly after the impact event may be viable explanations for the observed evidence the association of features which correspond to terrestrial lakes such as sedimentary deposits mounds and shorelines corroborates lake formation and their eventual desiccation to form cfps the variation of cfp sizes with location can be indicative of different hydrologic environments

wind blown sandstones cemented by sulfate and clay minerals in gale crater mars gale crater contains mount sharp a 5km thick stratigraphic record of mars early environmental history the strata comprising mount sharp are believed to be sedimentary in origin but the specific depositional environments recorded by the rocks remain speculative we present orbital evidence for the occurrence of eolian sandstones within gale crater and the lower reaches of mount sharp including preservation of wind blown sand dune topography in sedimentary strata a phenomenon that is rare on earth and typically associated with stabilization rapid sedimentation transgression and submergence of the land surface the preserved bedforms in gale are associated with clay minerals and elsewhere accompanied by typical dune cross stratification marked by bounding surfaces whose lateral equivalents contain sulfate salts these observations extend the range of possible habitable environments that may be recorded within gale crater and provide hypotheses that can be tested in situ by the curiosity rover payload

scaling behaviour of vertical magnetic susceptibility and its fractal characterization an example from the german continental deep drilling project ktb the variations of rock magnetism reflect the geological inhomogeneities of the earth s crust i e its petrological mineralogical and structural organization the present state of the crust bears meaningful information of its past dynamic processes and evolution we analysed magnetic susceptibility data series from the boreholes of the german continental deep drilling project ktb by means of spectral and rescaled range r s analyses we could detect a scaling behaviour of magnetic data series and quantify it in fractal terms in particular the r s method yields more precise results than the fourier analysis and leads to hurst coefficients h 0 5 which means that the magnetic variations exhibit some persistence with depth because of the relation between rock magnetism and crustal features we suggest that the magnetic vertical inhomogeneities in the ktb area can be described by a self affine model with h 0 8 corresponding to a fractal dimension d 1 2

impact fracturing and structural modification of sedimentary rocks at meteor crater arizona 1 meteor crater provides a rare opportunity to study impact deformation of sedimentary target rocks and isolate those features from preexisting tectonic deformation and impact generated reactivation of preexisting tectonic features this study reports over 2500 new measurements of orientations of bedding faults and fractures in crater walls and in surrounding bedrock target rocks are characterized by horizontal bedding planes that are cut by at least three prominent sets of preimpact tectonic fracture systems the crater rim is also cut by three distinct groups of fractures radial concentric and conical fractures when the crater rim is restored to preimpact condition the radial and concentric fractures resemble preimpact fracture populations indicating that crater wall deformation and rim uplift were partly accommodated by activation of preexisting fractures in contrast the conical fractures are dissimilar to the preimpact fractures and apparently formed as a direct result of impact deformation some of the preimpact fractures were transformed into tear faults during the impact event and motion along those faults appears to have controlled the geometry of the impact deformational features the crater rim is thus square in plan view rather than circular faults occurring in the crater diagonals are prominent ones allowing greater vertical displacement the deformation pattern of meteor crater is different from that at lonar crater which was excavated in basalt with fewer preimpact fractures the differences between deformation at meteor crater and lonar crater may reflect the same disparities seen in simple craters produced in different target lithologies on mars and other planetary surfaces

field observations of syngenetic ice wedge polygons outer mackenzie delta western arctic coast canada 1 low centered ice wedge polygons in the big lake delta plain of the outer mackenzie delta are unusual because their bounding ramparts appear to have a single ridge twenty two ice wedges in the area were examined between 2006 and 2009 to describe their morphology and diagnose their growth processes the ground above ice wedges had a subtle microtopography with ridges of 0 12 m relief and 4 0 m total width bisected by troughs only 0 05 m wide and 0 09 m deep the troughs initially obscured by vegetation growth and organic matter were underlain by ice wedges with average widths that increased downward in the uppermost 1 m of permafrost from 0 03 to 0 95 m shoulders on the ice wedges indicated vertical growth stages temperatures near the top of permafrost were favorable to thermal contraction cracking and ice veins connected to the top of wedge ice were observed in the active layer at five sites these observations indicate the ice wedges are syngenetic and active although without dating control we cannot unequivocally dismiss the possibility that the wedges are epigenetic features that were truncated by a recent thaw unconformity muted relief above the ice wedges which is uncommon above epigenetic ice wedges was largely due to aggradation of the surface secondary ice wedges have not developed within the polygons suggesting that climate variability has not led to polygon network development in this area wedge ice occupied only about 1 5 of the uppermost 1 m of permafrost a much smaller volumetric proportion than in epigenetic settings