gis based variability of building materials towards the ile de france cuesta paris basin france inventory distribution uses and relationship with the environment the pays re mois in the eastern paris basin is an administrative area of 1394 km2 in the surroundings of reims france two main geological substrata are separated by the i le de france cuesta the tertiary substratum in the western part is composed of various types of geomaterials clay sandstone limestone burrstone whereas the substratum in the eastern part is composed only of cretaceous chalk a field survey in each commune of the pays re moisidentified 26 building materials documented in a geographic information system database gis database that includes information about them lithology petrographical and petrophysical data weathering and the corresponding buildings e g town georeferenced data building type position on the fac ade the spatial analysis of the building materials distribution standard deviational ellipse with gis identifies their uses and the criteria established for the selection of the materials availability efficiency workability and durability some lithologies were preferred for particular buildings or selected for their efficiency in specific positions the study also defines the relation between the stones origin local and non local stones and their application this database is useful to establish stone replacement strategies in the pays re mois

documenting drainage evolution in bir kiseiba southern egypt constraints from ground penetrating radar and implications for mars 1 ground penetrating radar gpr helps to constrain the origin of relict and largely buried fluvial channels in the bir kiseiba region of southern egypt our results indicate that the trunk channel to a tributary system identified in shuttle imaging radar data is incised 10 12 m into bedrock was southwest draining in its final configuration and laterally migrating toward the northwest and accentuated relief along the nearby kiseiba escarpment alluvium partially filling the main channel likely reflects effects of increasing aridity and bed load combined with less frequent flashier precipitation in contrast to defining channel margins radar data do not indicate subtle stratigraphic changes in bedding related to fluvial aggradation but do highlight local reflections likely corresponding to relict alluvial bedforms our results support the contention that an impulse gpr system currently under development could be deployed on a future mars rover and assist in defining the regional evolution of the landscape and specific targets for sampling

salt crystallization in pores quantification and estimation of damage the objective of this study is to understand and predict the alteration of porous rock by crystallization of salts samples of different rocks have been tested according to the en 12370 standard test two parameters are proposed to evaluate the alteration of a rock during these tests the alteration index ai represents the cycle in which the first damages occur the alteration velocity av represents the alteration rate at the end of the experiment when the decay has become regular these parameters can be estimated with the help of a microstructural study of the rocks the most relevant intrinsic parameters of the stones for this estimation are capillary coefficient evaporation coefficient tensile strength and p waves velocity an evaluation of the alteration pattern is also proposed depending on the eventual heterogeneities and anisotropies of the rocks the influence of the dimension and shape of the samples is also discussed

subsurface imaging in south central egypt using low frequency radar bir safsaf revisited we present the capabilities of low frequency radar systems to sound the subsurface for a site located in south central egypt the bir safsaf region this site was already intensively studied since the sir a and sir b orbital radars revealed buried paleodrainage channels our approach is based on the coupling between two complementary radar techniques the orbital synthetic aperture radar sar in c and l bands 5 3 and 1 25 ghz for imaging large scale subsurface structures and the ground penetrating radar gpr at 500 and 900 mhz for sounding the soil at a local scale we show that the total backscattered power computed from l band sar and 900 mhz gpr profiles can be correlated and we combined both data to derive the geological structure of the subsurface gpr data provide information on the geometry of the buried scatterers and layers while the analysis of polarimetric sar data provides information on the distribution of rocks in the sedimentary layers and at the interface between these layers the analysis of 500 mhz gpr data revealed some deeper structures that should be detected by lower frequency sars such as a p band system

feasibility of nonhyperbolic moveout inversion in transversely isotropic media inversion of reflection traveltimes in anisotropic media can provide estimates of anisotropic coefficients required for seismic processing and lithology discrimination nonhyperbolic p wave moveout for transverse isotropy with a vertical symmetry axis vti media is controlled by the parameter or alternatively by the horizontal velocity vhor which is also responsible for the influence of anisotropy on all time processing steps including dip moveout dmo correction and time migration here we recast the nonhyperbolic moveout equation originally developed by tsvankin and thomsen as a function of vhor and normal moveout nmo velocity vnmo and introduce a correction factor in the denominator that increases the accuracy at intermediate offsets then we apply this equation to obtain vhor and from nonhyperbolic semblance analysis on long common midpoint cmp spreads and study the accuracy and stability of the inversion procedure our error analysis shows that the horizontal velocity becomes relat

stone properties and weathering induced by salt crystallization of maltese globigerina limestone most monuments and buildings in the maltese islands are constructed of the local globigerina limestone today this globigerina limestone shows considerable damage in many buildings particularly through alveolar weathering which is frequently very intense owing to malta s marine environment salt crystallization in the stone s pore spaces has been recognized as the main weathering process responsible for the deterioration of the country s monuments in order to obtain more information on the fabric dependent weathering processes of globigerina limestone detailed analyses were carried out globigerina limestone samples obtained from stone types with two different known qualities were characterized according to petrographical geochemical and physical properties these included porosity pore radii distribution and tensile strength as well as water and humidity transport properties investigations by means of salt crystallization tests on quarry samples of both stone types reinforced the idea that the extent of salt weathering depends on salt type and concentration and pore space properties visible weathering damage was recorded and evaluated for a representative monument the church of santa marija ta cwerra in siggiewi by means of a monument mapping method which was carried out twice over a period of 9 years 1995 and 2004 the identified weathering forms were also correlated with a previously developed weathering model for globigerina limestone according to the results of the mapping salt analyses carried out on samples from the church and salt loading tests on quarry samples there exists a significant correlation between visible damage and salt load the zoning of weathering damage is obviously related to different salt concentrations the zone with severe weathering damage is characterized by a high concentration of halite consequently salt weathering represents the main damage process for the globigerina limestone of malta the maltese archipelago of malta comino and gozo lies in the central mediterranean sea approximately 90 km south of sicily during the geological epochs of the oligocene and miocene 30 5 ma ago extensive sedimentation took place in this area this sedimentation led to the laying down of beds of limeand mudstones pedley et al 2002 the maltese globigerina limestone formation is one of five main formations and varies in thickness from 20 to over 200 m the material used for building is located stratigraphically in the lower part of the globigerina limestone formation called the lower globigerina limestone during the deposition of the sediments that eventually formed this stone far away from the continent and below the action of waves only minor but variable amounts of clay in suspension were carried from a distant land source the globigerina limestone also contains numerous shells algae and planktonic fossils mainly the planktonic foraminifera globigerina pedley et al 2002 as can be widely seen in the maltese islands the local limestone has always been used as the predominant building material the maltese prehistoric temples which were constructed approximately 6000 years ago bear testimony to this cassar vannucci 2001 between 1530 and 1798 the order of the knights of st john built kilometres of fortifications to protect the island from the expanding ottoman empire fortifications impressive churches fig 1 and palaces were built of the local building stone during this period the capital city of valletta is included in the unesco world heritage list as are the prehistoric temples even today the local building stone is still much in demand many modern buildings are constructed using the globigerina limestone fig 2a and many local quarries are still active fig 2b from p ikryl r smith b j eds building stone decay from diagnosis to conservation geological society london special publications 271 189 198 0305 8719 07 15 00 the geological society of london 2007

the influence of petrophysical properties on the salt weathering of porous building rocks the influence of pore structure water transport properties and rock strength on salt weathering is evaluated by means of a thorough rock characterisation and a statistical analysis the pore structure was described in terms of its porosity pore size distribution quantified by mean pore radius and specific surface area density and water transport was characterised by means of water permeability saturated flow and capillary imbibition unsaturated flow whilst the rock strength test was carried out using uniaxial compressive strength compressional and shear wave velocities dynamic elastic constants and waveform energy and attenuation were obtained from the digital analysis of the transmitted signal a principal component analysis and a stepwise multiple regression model was carried out in order to examine the direct relationships between salt weathering and petrophysical properties from the principal component analysis two main components were obtained and assigned a petrophysical meaning the first component is mostly linked to mechanical properties porosity and density whereas the second component is associated with the water transport and pore structure salt weathering quantified by the percentage of weight loss after salt crystallisation was included in both principal components showing its dependence on their petrophysical properties the stepwise multiple regression analysis found that rock strength has a predominant statistical weight in the prediction of salt weathering with a minor contribution of water transport and pore structure parameters

gpr a ground penetrating radar for the netlander mission in the coming decade several missions are planned that will land on the surface of mars landers or instrumented geophysical stations among the scientific objectives of these projects one of the most important will be to unravel the many unknowns in the geological and hydrological history of the planet the netlander mission offers a unique opportunity to explore the interior of mars its subsurface its atmosphere and its distant environment from four landing sites that will be selected to offer a variety of different geophysical conditions we have thus proposed to fly on these four landers a ground penetrating radar gpr to explore the geological characteristics of the subsurface and search for water reservoirs down to a depth which may be sufficient to allow a possible detection of liquid water we provide in this paper a short description of this radar which is based on a new concept to allow a 3 d imaging of the subsurface by determining the range and direction of the underground reflectors in order to access to deep layers it will operate at a low frequency of 2 mhz some results obtained by a numerical modeling of the radar operation in an electromagnetic model of the martian subsurface are presented in order to illustrate the main capabilities of the radar in the last section preliminary results from an initial field test are reported in addition to its primary goal as a ground penetrating radar the gpr will also be operated on mars as an ionospheric sounder and in a passive mode as a hf receiver to measure the radio electric background

enhanced carbonate petrography using fluorescence microscopy abstract fluorescence microscopy can recognize depositional facies and delineate diagenetic fabrics and porosity relationships in certain highly dolomitized or recrystallized limestones previously uninterpretable using standard petrographic techniques this tool has other valuable applications in the study of carbonate rocks these other applications include differentiating carbonate cements from neomorphic spar enhancing depositional and diagenetic fabrics rapidly evaluating mineralogical stabilization and recrystallization in holocene and pleistocene deposits and improving delineation of porosity and pore geometries in sedimentary rocks fluorescence microscopy is a rapid easily used and nondestructive technique that can be applied to unpolished thin sections or rock slabs by itself or in conjunction with other petrographic and geochemical tools it has the potential to expand our understanding of carbonate diagenetic processes and products in particular dolomitization and neomorphism and carbonate porosity evolution we strongly encourage routine usage of fluorescence microscopy in future carbonate petrographic studies

normal moveout coefficients for horizontally layered triclinic media abstractsedimentary layers affected by vertical compaction and strong lateral tectonic stresses are often characterized by low anisotropic symmetry e g tilted orthorhombic tor monoclinic or even triclinic considering all types of pure mode and converted waves we derive the normal moveout nmo series coefficients of near normal incidence reflected waves in arbitrarily anisotropic horizontally layered media for a leading error term of order six the nmo series can be either a function of the invariant horizontal slowness slowness domain or the surface offset offset domain the nmo series coefficients referred to also as effective parameters are associated with the corresponding azimuthally varying nmo velocity functions we distinguish between local single layer and global overburden multilayer effective parameters which are related by forward and inverse dix type transforms we derive the local effective parameters for an arbitrary anisotropic triclinic layer which is the main contr

self affine behavior of martian topography at kilometer scale from mars orbiter laser altimeter data 1 we used mars orbiter laser altimeter mola data from the current mars global surveyor mission to characterize the topographic roughness of the martian surface and to provide a mean to evaluate clutter at long 10 300 m wavelengths such wavelengths are relevant for the marsis and sharad subsurface radars which will be flown in future missions to mars the method of analysis is based on the assumption that topography can be described as a self affine fractal 30 km long segments of mola altimetry profiles have thus been reduced to the topographic parameters rms height rms slope and hurst exponent this last related to the fractal dimension which can be used as inputs to a near nadir radar scattering model the values of the hurst exponent are greater than 0 5 for most of the surface meaning a scaling behavior which is almost self similar maps of rms height and hurst exponent show that these two parameters have very different spatial distributions whereas the rms height is patterned after the north south dichotomy the hurst exponent follows a latitudinal trend we make use of a multivariate method called g mode to classify profiles in the three dimensional parameter space we find several roughness units some of which have a strong correlation with certain geologic units while others are bound by latitude however at scales between 300 m and 3 km large stretches of the surface of mars share common statistical properties of topography independent from the north south dichotomy

buried impact craters a topographic analysis of quasi circular depressions utopia basin mars 1 many quasi circular depressions qcds revealed in the mars orbiter laser altimeter data set have no obvious structural representation in visible images of mars it has been suggested that these qcds are surface representations of buried impact craters and on the basis of this assumption cumulative count versus diameter plots of qcds in the northern lowlands have been constructed to date the buried lowland floor if the qcds are in fact buried impact craters their surface relief should scale directly with their diameter this relationship holds true for 115 qcds with diameters ranging from 7 to 100 km within roughly 1500 km of the center of the utopia basin the coefficient of determination r2 of the relationship more closely approaches 1 when qcds in zones of comparable cover thickness are evaluated the surface relief versus diameter relationship of 55 randomly selected pseudo qcds was also determined their poor correlation indicates that the direct relationship of surface relief to diameter of actual qcds is due to differential compaction of a cover material over buried impact craters and is not just a random effect of qcd diameter the slope of the trend of the qcds surface relief versus diameter when divided into zones of comparable cover thickness can be used to determine which zones have thicker or thinner cover

mineralogical geochemical and microfabric evidences of gypsum crusts a case study from budapest high levels of so2 and particulate pollution enable the rapid development of gypsum rich weathering crusts in budapest two types of white crusts thin and thick ones and two forms of black crusts laminar and framboidal ones were studied in limestone buildings of the parliament and citadella the percentage of crust cover and damage categories were documented on selected walls petrographic xrd xrf and sulphur isotope analyses were performed under laboratory conditions to understand the mechanism of crust formation white crusts found both on exposed and sheltered walls display a calcite rich layer with gypsum while black crusts are enriched with gypsum the sulphur isotopic composition of white and black crusts overlaps but the crusts are slightly enriched in heavy isotopes compared to rainwater s content si al ratios and particulates in black crusts suggest that air pollution so2 dust contributes to black crust formation the accumulation of sulphur and zn enrichment of white crusts were also documented indicating that under high pollution levels even these compound can accumulate on exposed facades

probing structural elements of small buried craters using ground penetrating radar in the southwestern egyptian desert implications for mars shallow sounding we report results from a field survey performed on a recently discovered impact field in the southwestern egyptian desert using a 270 mhz ground penetrating radar gpr this hyperarid region has significant similarities to the martian heavily eroded mid latitude cratered terrains in terms of crater density size and geomorphology profiles across small buried craters revealed a coherent sequence of tilted layers constituting the cratonic infill resulting from aeolian deposits in the intercrater areas the radargram revealed a poorly defined subsurface stratigraphy and the presence of shallow structural elements associated with potential evidences of the consequences of the shock effects i e faulting fractures and chaotic bedrock the radar penetration depth varied from 2 to 15 m depending mainly on the amplitude of the volume and multiple scattering in the subsurface caused by fractures and debris created by the impacts we conclude that mid frequency gpr onboard future martian rovers can successfully perform similar structural mapping

generalized dix equation and analytic treatment of normal moveout velocity for anisotropic media despite the complexity of wave propagation in anisotropic media reflection moveout on conventional common midpoint cmp spreads is usually well described by the normal moveout nmo velocity defined in the zero offset limit in their recent work grechka and tsvankin showed that the azimuthal variation of nmo velocity around a fixed cmp location generally has an elliptical form i e plotting the nmo velocity in each azimuthal direction produces an ellipse and is determined by the spatial derivatives of the slowness vector evaluated at the cmp location this formalism is used here to develop exact solutions for the nmo velocity in anisotropic media of arbitrary symmetry for the model of a single homogeneous layer above a dipping reflector we obtain an explicit nmo expression valid for all pure modes and any orientation of the cmp line with respect to the reflector strike the contribution of anisotropy to nmo velocity is contained in the slowness components of the zero offset ray along with the derivatives of the vertical slowness with respect to the horizontal slownesses quantities that can be found in a straightforward way from the christoffel equation if the medium above a dipping reflector is horizontally stratified the effective nmo velocity is determined through a dix type average of the matrices responsible for the interval nmo ellipses in the individual layers this generalized dix equation provides an analytic basis for moveout inversion in vertically inhomogeneous arbitrarily anisotropic media for models with a throughgoing vertical symmetry plane i e if the dip plane of the reflector coincides with a symmetry plane of the overburden the semi axes of the nmo ellipse are found by the more conventional rms averaging of the interval nmo velocities in the dip and strike directions modelling of normal moveout in general heterogeneous anisotropic media requires dynamic ray tracing of only one zero offset ray remarkably the expressions for geometrical spreading along the zero offset ray contain all the components necessary to build the nmo ellipse this method is orders of magnitude faster than multi azimuth multi offset ray tracing and therefore can be used efficiently in traveltime inversion and in devising fast dip moveout dmo processing algorithms for anisotropic media this technique becomes especially efficient if the model consists of homogeneous layers or blocks separated by smooth interfaces the high accuracy of our nmo expressions is illustrated by comparison with ray traced reflection traveltimes in piecewise homogeneous azimuthally anisotropic models we also apply the generalized dix equation to field data collected over a fractured reservoir and show that p wave moveout can be used to find the depth dependent fracture orientation and to evaluate the magnitude of azimuthal anisotropy

morphology and mineralogy of weathering crusts on highly porous oolitic limestones a case study from budapest black crusts are very common on limestones in polluted urban environments but white crusts are less frequently developed on the soft porous and inherently weak oolitic limestone of budapest both crusts are frequent and indeed white ones are more common on the stone walls of the studied fortress in this paper black and white crusts and the host rock have been described using morphological criteria mineralogical analyses xrd dta elements analyses microprobe and micro morphological sem tests the analyses have shown that on white crusts the surface dissolution is combined with the precipitation of gypsum and calcite in the pores and accumulation of gypsum on the underside of the crust thin white crusts are removed by a combination of salt crystallisation gypsum and frost action while very thick stone layers scale off due to freeze thaw cycles black crusts are enriched in gypsum relative to white crusts gypsum accumulates on the crust surface and signs of dissolution have not been observed airborne particulates flyash silt sized quartz and organic debris adhere to the crust surface of sheltered black crusts these particles are later incorporated into the expanding gypsum crystals that are visible on the underside of the crust the host rock also contains gypsum but it is washed off the surface when the crust is removed further exposure of the host rock may lead to the dissolution of calcite crystals as it is observed by sem the micro environment influences the crust formation and adherence of the crusts on frequently wet and dry surfaces crust removal is more common the crust serves as a protective layer on the stone surface but this protection is temporary since trigger mechanisms such as salt crystallisation or frost action can cause rapid surface loss

slowness domain offset and traveltime approximations in layered vertical transversely isotropic media considering horizontally layered transversely isotropic media with vertical symmetry axis and all types of pure mode and converted waves we present a new wide angle series approximation for the kinematical characteristics of reflected waves horizontal offset intercept time and total reflection traveltime as functions of horizontal slowness the method is based on combining gluing both zero offset and large finiteoffset series coefficients the horizontal slowness is bounded by the critical value characterised by nearly horizontal propagation within the layer with the highest horizontal velocity the suggested approximation uses five parameters to approximate the offset six parameters to approximate the intercept time or the traveltime and seven parameters to approximate any two or all three kinematical characteristics overall the method is very accurate for pure mode compressional waves and shear waves polarised in the horizontal plane and for converted waves the application of the method to pure mode shear waves polarised in the vertical plane is limited due to cusps and triplications to demonstrate the high accuracy of the method we consider a synthetic multi layer model and we plot the normalised errors with respect to numerical ray tracing

rational interpolation of qp traveltimes for semblance based anisotropy estimation in layered vti media the p domain is the natural domain for anisotropy parameterestimationinhorizontallylayeredmedia theneedto transformthedatatothe p domainortopicktraveltimesin thet xdomainis however apracticaldisadvantage toovercomethis wecombine p derivedtraveltimesandoffsetsin horizontally layered transversely isotropic media with a verticalsymmetryaxisvtiwitharationalinterpolationprocedureappliedinthet xdomain thiscombinationresultsinan accurate and efficient t x based semblance analysis for anisotropy parameter estimation from the moveout of qpwaves in horizontally layered vti media the semblance analysisisappliedtothemoveouttosearchdirectlyfortheinterval values of the relevant parameters to achieve this the method is applied in a layer stripping fashion we demonstrate the method using synthetic data examples and show thatitisrobustinthepresenceofrandomnoiseandmoderate statics

converted wave seismic exploration applications converted seismic waves specifically downgoing p waves that convert on reflection to upcoming s waves are increasingly being used to explore for subsurface targets rapid advancements in both land and marine multicomponent acquisition and processing techniques have led to numerous applications for p s surveys uses that have arisen include structural imaging e g seeing through gas bearing sediments improved fault definition enhanced near surface resolution lithologic estimation e g sand versus shale content porosity anisotropy analysis e g fracture density and orientation subsurface fluid description and reservoir monitoring further applications of p s data and analysis of other more complicated converted modes are developing

traveltime approximation in vertical transversely isotropic layered media the well known asymptotic fractional four parameter traveltime approximation and the five parameter generalised traveltime approximation in stratified multi layer transversely isotropic elastic media with a vertical axis of symmetry have been widely used for pure mode and converted waves the first three parameters of these traveltime expansions are zero offset traveltime normal moveout velocity and quartic coefficient ensuring high accuracy of traveltimes at short offsets the additional parameter within the four parameter approximation is an effective horizontal velocity accounting for large offsets which is important to avoid traveltime divergence at large offsets the two additional parameters in the above mentioned five parameter approximation ensure higher accuracy up to a given large finite offset with an exact match at this offset in this paper we propose two alternative five parameter traveltime approximations which can be considered extensions of the four parameter approximation and an alternative to the five parameter approximation previously mentioned the first three short offset parameters are the same as before but the two additional long offset parameters are different and have specific physical meaning one of them describes the propagation in the high velocity layer of the overburden nearly horizontal propagation in the case of very large offsets and the other characterises the intercept time corresponding to the critical slowness that includes contributions of the lower velocity layers only unlike the above mentioned approximations both of the proposed traveltime approximations converge to the theoretical asymptotic linear traveltime at the limit case of very large infinite offsets their accuracy for moderate to very large offsets for quasi compressional waves converted waves and shear waves polarised in the horizontal plane is extremely high in cases where the overburden model contains at least one layer with a dominant higher velocity compared with the other layers we consider the implementation of the proposed traveltime approximations in all classes of problems in which the above mentioned approximations are used such as reflection and diffraction analysis and imaging

three term taylor series for t2 x2 curves of p and s waves over layered transversely isotropic ground the arrival time curve of a reflection from a horizontal interface beneath a homogeneous isotropic layer is a hyperbola in the x t domain if the subsurface is one dimensionally inhomogeneous horizontally layered or if some or all of the layers are transversely isotropic with vertical axis of symmetry the statement is no longer strictly true though the arrival time curves are still hyperbola like in the case of transverse isotropy however classical interpretation of these curves fails interval velocities calculated from t 2 x 2 curves do not always approximate vertical velocities and therefore cannot be used to calculate depths of reflectors to study the relationship between velocities calculated from t 2 x 2 curves and the true velocities of a transversely isotropic layer we approximate t 2 x 2 curves over a vertically inhomogeneous transversely isotropic medium by a three term taylor series and calculate expressions for these terms as a function of the elastic parameters it is shown that both inhomogeneity and transverse isotropy affect slope and curvature of t 2 x 2 curves for p waves the effect of transverse isotropy is that the t 2 x 2 curves are convex upwards for sv waves the curves are convex downwards for sh waves transverse isotropy has no effect on curvature

converted wave seismic exploration methods multicomponent seismic recording measurement with vertical and horizontal component geophones and possibly a hydrophone or microphone captures the seismic wavefield more completely than conventional single element techniques in the last several years multicomponent surveying has developed rapidly allowing creation of converted wave or p s images these make use of downgoing p waves that convert on reflection at their deepest point of penetration to upcoming s waves survey design for acquiring p s data is similar to that for p waves but must take into account subsurface vp vs values and the asymmetric p s ray path p s surveys use conventional sources but require several times more recording channels per receiving location some special processes for p s analysis include anisotropic rotations s wave receiver statics asymmetric and anisotropic binning nonhyperbolic velocity analysis and nmo correction p s to p p time transformation p s dip moveout prestack migration with two velocities and wa

ground penetrating radar as a tool for probing the shallow subsurface of mars 1 design and testing of an impulse ground penetrating radar gpr for possible rover deployment on mars in 2009 is well underway the gpr has mass power volume and data rate targets of 0 5 kg 3 w peak 3400 cm3 and 0 3 mb d and will possess easily modified bistatic high frequency e g 500 600 mhz and monostatic rat tail e g 100 mhz antennas the gpr should be capable of measuring in situ radar properties on mars to depths of up to 10 20 m thereby helping to constrain near surface geology and structure initial gpr tests at the site of the 2001 fido rover field trials near cronese lake california confirm the value of the instrument in defining local geologic setting and in providing context for data collected using other rover science payload elements a rover deployed gpr may enable three dimensional mapping of local stratigraphy which in turn can assist in evaluating the history of aqueous activity and the accessibility of near surface water