a ferroan region of the lunar highlands as recorded in meteorites mac88104 and mac88105 macalpine hills 88104 and 88105 mac88104 5 are paired meteorites of noritic anorthosite composition from the lunar highlands mac88105 is a breccia composed mainly of melt breccia clasts in a fine grained fragmental and partly glassy matrix the most abundant melt lithologies are feldspathic and are similar in composition to the bulk meteorite other melt lithologies include feldspathic melt rocks mafic melt breccias and a rare melt breccia relatively enriched in incompatible trace elements subordinate lithic clasts are granulitic breccias and ferroan relatively low mg mg fe igneous lithologies including troctolitic anorthosite anorthositic norite gabbronorite and anorthosite igneous clasts having mafic mineral compositions more magnesian than fo55 and en60 were not observed rare fragments of glass spheres and shards as well as glass clasts indicate that the meteorite was derived from an immature regolith the bulk composition of mac88105 is characterized by a molar mg mg fe ratio of 0 62 at the extreme low end of the range for meteorites from the lunar highlands its low concentrations of incompatible trace elements and feldspathic bulk composition 29 al2o3 suggest that it like the other lunar meteorites formed at a site far removed from the areas sampled by the apollo missions similarities in mineral compositions among the different lithologies of the breccia melt breccia clasts granulitic breccias igneous fragments and the distribution of mineral fragments suggest that most components of the meteorite were derived from a crustal section dominated by material with a noritic anorthosite composition and an affinity to the ferroan suite of plutonic rocks the mafic melt breccias have roughly peritectic melt compositions similar to many low k fra mauro melt breccias in the apollo collection but much more ferroan and represent a source material distinct from the noritic anorthosite moderate ce anomalies both positive and negative occur in some separated clasts and to a lesser extent in some small chips dominated by matrix but not in powder prepared from 20 g of bulk meteorite these anomalies are almost certainly terrestrial weathering effects one granulitic breccia clast is rich in siderophile elements as a result of a large amount of fe ni metal the auir ratio of the clast 0 64 ci normalized is distinctly different from that of metal rich impact melts from apollo 16 3 ci normalized the compositional range observed among the nonmare lunar meteorites alha81005 y791197 y82192 3 y86032 and mac88104 5 is equivalent to that observed among representative samples of 1 mm fines from apollo 16 thus compositional data provide little constraint on the number of impacts required to eject these meteorites from the moon

feldspathic lunar meteorites pecora escarpment 02007 and dhofar 489 contamination of the surface of the lunar highlands by post basin impacts abstract pca pecora escarpment 02007 and dhofar 489 are both meteorites from the feldspathic highlands of the moon pca 02007 is a feldspathic breccia consisting of lithified regolith from the lunar surface it has concentrations of both incompatible and siderophile elements that are at the high end of the ranges for feldspathic lunar meteorites dhofar 489 is a feldspathic breccia composed mainly of impact melted material from an unknown depth beneath the regolith concentrations of incompatible and siderophile elements are the lowest among brecciated lunar meteorites among 19 known feldspathic lunar meteorites all of which presumably originate from random locations in the highlands concentrations of incompatible elements like sm and th tend to increase with those of siderophile elements like ir feldspathic meteorites with high concentrations of both suites of elements are usually regolith breccias iridium derives mainly from micrometeorites that accumulate in the regolith with duration of surface exposure micrometeorites have low concentrations of incompatible elements however so the correlation must reflect a three component system we postulate that the correlation between sm and ir occurs because the surface of the feldspathic highlands terrane has become increasingly contaminated with time in sm rich material from the procellarum kreep terrane that has been redistributed across the lunar surface by impacts of moderate sized post basin impacts the most sm rich regolith breccias among feldspathic lunar meteorites are about 3 enriched compared to the most sm poor breccias but this level of enrichment requires only a few percent sm rich material typical of the procellarum kreep terrane the meteorite data suggest that nowhere in the feldspathic highlands are the concentrations of k rare earths and th measured by the lunar prospector mission at the surface representative of the underlying bedrock all surfaces covered by old regolith as opposed to fresh ejecta are at least slightly contaminated dhofar 489 is one of 15 paired lunar meteorite stones from oman total mass of meteorite 1037 g on the basis of its unusually high mg fe ratio the meteorite is likely to have originated from northern feldspathic highlands

understanding the lunar surface and space moon interactions the surface of the moon is a critical boundary that shapes our understanding of the moon as a whole all geologic mapping and remote sensing techniques utilize only the outermost portion of the moon before leaving the moon for study in our laboratories all lunar samples that have been studied existed at or very near the surface with the exception of the deeply probing geophysical techniques our understanding of the interior of the moon is derived from surficial but not superficial information coupled with boundary of the lunar crust it is the lower boundary layer of the tenuous lunar atmosphere and constitutes both a source and a sink for atmospheric gases the surface is also where the moon interacts with the space environment causing changes in the physical nature of lunar materials and provides a laboratory for the study of processes that occur on all airless bodies the data obtained remotely by the galileo clementine and lunar prospector missions as well as data derived from lunar meteorites have resulted in major changes to our understanding of global distributions of chemistry and rocks this chapter summarizes the current understanding of this critical interface the surface of the moon in its role as the lower boundary of the lunar atmosphere the upper boundary of the crust and the window through which we view through remote sensing the composition of the crust and the history of the moon in this post lunar prospector time the view of the moon has changed lending new perspectives to lunar samples and lunar processes but the new view will likely remain in flux as we continue to digest the results from these recent space missions and move forward to a new era of lunar exploration despite the freshness of our perspective this is an important moment to capture

importance of groundwater sulfate to acidification in the goose river watershed maine 1 the role of groundwater sulfate discharge to ponds and streams within the goose river basin 33 3 km2 is examined while airborne sulfate deposition has declined acidity in surface waters locally remains elevated monthly so42 analyses 1999 2002 of wet deposition and surface waters are reported and a sulfate budget for six catchments of the goose river watershed maine is calculated groundwater values from different bedrock types are beneficial in identifying groundwater source s of sulfate in surface waters and discriminating them from atmospheric sulfate deposition the variability of proposed sulfide oxidation among certain local chalcophile rocks and the depth of aeration in these sheared granitoids are elucidated from and data cosmogenic residence times estimate new atmospheric so42 deposition in the catchments and production of so42 from water rock interactions among some fractured granitoids

the effects of historic abstraction of groundwater from the london basin aquifers on groundwater quality abstract the basal sands and chalk aquifers in the lee valley and enfield haringey areaas of north london have considerable potential for artificial recharge having been dewatered by groundwater abstraction since the late 1800s trials have been undertaken periodically since the mid 1950s however one of the drawbacks is the potential for developing poor quality groundwater as a result of pyrite oxidation in the basal sands analysis of pumped groundwaters from the basal sands has confirmed the presence of relatively high concentrations of dissolved so4 along with k ca total fe and li porewater chemistry profiles have been obtained from fresh cores through the basal sands and underlying chalk at four sites the site with the highest so4 concentration up to 33 000 mg 1 1 had a porewater ph of 3 45 and has remained dewatered owing to overpumping for more than 70 a water pumped from the chalk showed little evidence of these extreme conditions there was no overall correlation between the bulk pyrite or gypsum content of the sediment and the porewater so4 concentration within the sediment the principal mechanism governing the generation of so4 is the oxidation of pyrite which is present in small amounts the extremely high concentrations of so4 in the porewaters indicate that the extent of oxidation is controlled by the entry of air rather than the input of dissolved oxygen or nitrate in the groundwater or recharge water abstraction from the chalk aquifer over many decades has resulted in the dewatering of the overlying basal sands aquifer allowing air entry and has led to the localized oxidation of pyrite and the accumulation of poor quality porewater in the basal sands the rate of oxidation is probably greatest near to wells and boreholes which allow ready access of air the solutes produced are only available for abstraction after the water table has risen dilution with native chalk groundwater will tend to minimize potential water quality problems future oxidation will be minimized by maintaining a high water table

degradation of mid latitude craters on mars abstract recent geomorphic remote sensing and atmospheric modeling studies have shown evidence for abundant ground ice deposits in the martian mid latitudes numerous potential water ice rich flow features have been identified in craters in these regions including arcuate ridges gullies and small flow lobes previous studies such as in newton basin have shown that arcuate ridges and gullies are mainly found in small craters 2 30 km in diameter these features are located on both pole facing and equator facing crater walls and their orientations have been found to be dependent on latitude we have conducted surveys of craters 20 km in diameter in two mid latitude regions one in the northern hemisphere in arabia terra and one in the southern hemisphere east of hellas basin in these regions prominent lobes potentially ice rich are commonly found on the walls of craters with diameters between 20 100 km additional water ice rich features such as channels valleys alcoves and debris aprons have also been found in association with crater walls in the eastern hellas study region channels were found to be located primarily on pole facing walls whereas valleys and alcoves were found primarily on equator facing walls in the arabia terra study region these preferences are less distinct in both study regions lobate flows gullies and arcuate ridges were found to have pole facing orientation preferences at latitudes below 45 and equator facing orientation preferences above 45 similar to preferences previously found for gullies and arcuate ridges in smaller craters interrelations between the features suggest they all formed from the mobilization of accumulated ice rich materials the dependencies of orientations on latitude suggest a relationship to differences in total solar insolation along the crater walls differences in slope of the crater wall differences in total solar insolation with respect to wall orientation and variations in topography along the crater rim can explain the variability in morphology of the features studied the formation and evolution of these landforms may best be explained by multiple cycles of deposition of ice rich material during periods of high obliquity and subsequent modification and transport of these materials down crater walls

apollo 15 green glass compositional distribution and petrogenesis abstract we have characterized a comprehensive suite of individual green glass beads from apollo 15 soil to determine interelement behavior and to constrain petrogenetic relationships we analyzed 365 particles for trace elements by instrumental neutron activation analysis and analyzed 52 of them selected to cover the compositional ranges observed for trace elements for major elements by electron microprobe analysis we confirm the observation of delano 1979 that the beads comprise discrete compositional groups although two of the groups he denned are further split on the basis of trace element compositions each of the resulting seven groups has distinct average rare earth abundances the coherence between major and trace element data was masked in previous studies by imprecision correlated error and nonrepresentative sampling of the different groups most of the compositional characteristics of the green glasses can be explained by a model for batch equilibrium melting of a nearly homogeneous ultramafic source region when the complicating effects of high pressure and low oxygen fugacity are taken into account the previously puzzling behavior of ni and co as apparently incompatible elements may arise from partial reduction of those elements to the zero oxidation state resulting in low mineral melt partition coefficients the model also offers explanations for why the green glasses form boomerang shaped trends on many two element variation diagrams and why certain compositions groups a and d are more abundant than glasses with other compositions

global distribution of neutrons from mars results from mars odyssey global distributions of thermal epithermal and fast neutron fluxes have been mapped during late southern summer northern winter using the mars odyssey neutron spectrometer these fluxes are selectively sensitive to the vertical and lateral spatial distributions of h and co 2 in the uppermost meter of the martian surface poleward of 60 latitude is terrain rich in hydrogen probably h 2 o ice buried beneath tens of centimeter thick hydrogen poor soil the central portion of the north polar cap is covered by a thick co 2 layer as is the residual south polar cap portions of the low to middle latitudes indicate subsurface deposits of chemically and or physically bound h 2 o and or oh

thermal conductivity and thermodynamics of majoritic garnets implications for the transition zone abstract thermal conductivity at room temperature and pressure k 0 and heat capacity and total entropy as functions of temperature are calculated for majorite pyrope garnets from new and previous infrared reflectivity and raman scattering data the thermodynamic properties including the effect of cation disorder vary by less than 4 over this binary whereas k 0 changes by 400 due to cation disorder for mantle garnet compositions 70 mol majorite k 0 is 2 3 w m k which is 25 k 0 of ringwoodite the other major mineral in earth s transition zone tz the dynamics of the tz is governed by its two dominant minerals having disparate values for k and viscosity which parallels the situation in the lower mantle if the tz has substantial 60 70 proportions of majoritic garnet as suggested by petrological models then heat flow therein is inhibited relative to the upper and lower mantles sub adiabatic temperatures are implied which is consistent with steep velocity gradients in the tz association of low thermal conductivity with high temperatures should contribute to the buoyancy of the tz layer weaken it and promote transformation to garnet such destablization through positive feedback possibly provides a mechanism for catastrophic overturns of the tz and upper mantle

effect of sulfidogenesis cycling on the biogeochemical process in arsenic enriched aquifers in the lanyang plain of taiwan evidence from a sulfur isotope study summary this study evaluated the biogeochemical interactions between arsenic as and sulfur s in groundwater to understand the natural and anthropogenic influences of s redox processes on as mobilization in the lanyang plain taiwan cl and the sulfate isotopic composition 34 s so 4 were selected as conservative tracers river water and saline seawater were considered as end members in the binary mixing model thirty two groundwater samples were divided into four types of groundwater i pyrite oxidation ii iron and sulfate reducing iii sulfate reducing and iv anthropogenic and others the binary mixing model coupled with discriminant analysis was applied to yield a classification with 97 correctness indicating that the do orp values and 34 s so 4 and fe 2 concentrations are effective redox sensitive indicators type i groundwater is mostly located in a mountainous recharge area where pyrite oxidation is the major geochemical process a high 18 o enrichment factor e so 4 h 2 o and high 34 s enrichment factor e 34 s fes 2 so 4 indicate that disproportionation and dissimilatory sulfate reduction are both involved in type ii and type iii groundwater the process of bacterial sulfate reduction may coprecipitate and sequester as a mechanism that is unlikely to occur in type ii groundwater the presence of high as and fe 2 concentrations and enriched 34 s so 4 in type ii groundwater suggest that biogeochemical reactions occurred under anaerobic conditions the reductive dissolution of as bearing fe oxyhydroxides together with microbial disproportionation of sulfur explains the substantial correlations among the high as concentration and enriched 34 s so 4 and fe 2 concentrations in the iron and sulfate reducing zone type ii the as concentration in type iii groundwater sulfate reducing is lower than that in type ii groundwater because of bacterial sulfate reduction and coprecipitation with as furthermore the dissolution of sulfate minerals is not the major source of aqueous so 4 based on the sulfur isotopic composition of solid phase sulfate 34 s sulfate mineral finally the anthropogenic influence of fertilizers with wide s isotopic ranges is proposed as the plausible sulfate budget in type iv groundwater the results of this study suggest that the as release into groundwater involves the reductive dissolution of as bearing fe hydroxides bacterial sulfate reduction and microbial disproportionation in the lanyang plain

lunar and martian meteorite delivery services launch mechanisms for lunar and martian meteorites have been investigated by integrating physical modeling constraints geochemical cosmic ray exposure cre constraints and petrologic constraints the potential source region for lunar meteorites is remarkably small compared to the final crater volume cre constraints indicate that most launches start at depths of 3 2 m and cratering theory implies derivation of suitably accelerated objects from a subvolume with diameter only about 0 3 the final crater diameter the shallow depth provenance is probably related to shock wave interference enhanced by the lunar regolith s extremely low compressional wave velocity cre constraints alone imply that four to five separate launch events are represented among the eight well studied lunar meteorites most of the lunar meteorites are regolith breccias which tend to show only limited compositional diversity within any kilometer scale region of the moon several others are polymict breccias which also show relatively subdued compositional diversity compared to igneous rocks the observed diversity among these samples in terms of abundances of mare basalt and kreep and in mg mg fe ratio implies that among eight well studied lunar meteorites only two potential source crater pairings are plausible between asuka 881757 y 793169 most probable and between y 793274 eet875721 altogether these eight lunar meteorites apparently represent at least six separate source craters including three in the past 105 years and five in the past 106 years cre constraints imply that snc meteorites are launched from systematically greater depths than lunar meteorites sncs are also systematically bigger and all nine well studied sncs are uncommonly young by martian standards mafic igneous rocks comparison between viking and apollo results reveals that rocks the size of common meteorites are remarkably scarce in the martian regolith probably due to pervasive weathering a plausible explanation for these trends is that most old small and shallow rocks on mars have been weakened by a two stage process of brecciation followed by pervasive weathering to the point where they seldom survive the stresses of spallation off the planet the scarcity of source crater pairing among the lunar meteorites implies that these objects can be launched from craters much smaller than previously estimated and tends to support the suggestion of rabinowitz 1993 astrophys j 407 412 427 that present day cratering rates for the earth moon region may be higher than previously estimated

context camera investigation on board the mars reconnaissance orbiter 1 the context camera ctx on the mars reconnaissance orbiter mro is a facility instrument i e government furnished equipment operated by a science team not responsible for design and fabrication designed built and operated by malin space science systems and the mro mars color imager team marci ctx will 1 provide context images for data acquired by other mro instruments 2 observe features of interest to nasa s mars exploration program e g candidate landing sites and 3 conduct a scientific investigation led by the marci team of geologic geomorphic and meteorological processes on mars ctx consists of a digital electronics assembly a 350 mm f 3 25 schmidt type telescope of catadioptric optical design with a 5 7 field of view providing a 30 km wide swath from 290 km altitude and a 5000 element ccd with a band pass of 500 700 nm and 7 m pixels giving 6 m pixel spatial resolution from mro s nearly circular nearly polar mapping orbit raw data are transferred to the mro spacecraft flight computer for processing e g data compression before transmission to earth the ground data system and operations are based on 9 years of mars global surveyor mars orbiter camera on orbit experience ctx has been allocated 12 of the total mro data return or about 3 terabits for the nominal mission this data volume would cover 9 of mars at 6 m pixel but overlapping images for stereo mosaics and observation of changes and meteorological events will reduce this area ctx acquired its first instrument checkout images of mars on 24 march 2006

some things we can infer about the moon from the composition of the apollo 16 regolith randy l korotev department of earth and planetary sciences and mcdonnell center for the space sciences washington university st louis missouri 63130 usa author s e mail address rlk levee wustl edu received 1996 september 16 accepted in revised form 1997 may 12 abstract characteristics of the regolith of cayley plains as sampled at the apollo 16 lunar landing site arereviewed and new compositional data are presented for samples of 1 mm fines soils and 1 2 mm rego lith particles as a means of determining which of the many primary igneous and secondary crystalline brec cias lithoiogic components that have been identified in the soil are volumetrically important and providing anestimate of their relative abundances more than 3 x 106 combinations of components representing nearly everylithology that has been observed in the apollo 16 regolith were systematically tested to determine which com binations best account for the composition of the soils conclusions drawn from the modeling include the fol lowing at the site mature soil from the cayley plains consists of 64 5 2 7 components representing prebasin materials anorthosites feldspathic breccias and a small amount 2 6 1 5 of total soil ofnonmare mafic plutonic rocks mostly gabbronorites on average these components are highly feldspathic with average concentrations of 31 32 a1203 and 2 3 feo and a molar mg mg fe ratio of 0 68 theremaining 36 of the regolith is syn and postbasin material 28 8 2 4 mafic impact melt breccias mimbs i e lkfm and vha basalts created at the time of basin formation 6 0 1 4 mare derived material impact and volcanic glass crystalline basalt with an average tio2 concentration of 2 4 and 1 postbasin meteoritic material the mimbs are the principal 80 90 carrier of incompatible traceelements rare earths th etc and the carrier of about one half of the siderophile elements and elementsassociated with mafic mineral phases fe mg mn cr sc most 71 of the fe in the present regolithderives from syn and postbasin sources mimbs mare derived material and meteorites thus althoughthe bulk composition of the apollo 16 regolith is nominally that of noritic anorthosite the noritic part themimbs and the anorthositic part the prebasin components are largely unrelated there is compositionalevidence that 3 4 of the soil is th rich material such as that occurring at the apollo 14 site and one frag ment of this type was found among the small regolith particles studied here if regolith such as that repre sented by the apollo 16 ancient regolith breccias was a protolith of the present regolith such regolith cannotexceed 71 of the present regolith the rest must be material added or redistributed since closure of theancient regolith breccias the postclosure material includes the mare derived material and the apollo 14 like component compositions of all mature surface soils from apollo 16 even those collected 4 km apart on the cayleyplains are very similar which is in stark contrast to the wide compositional range of the lithologies of whichthe soil is composed this uniformity indicates that the ratio of mimbs to feldspathic prebasin componentsis not highly variable in the megaregolith over distances of a few kilometers that there are no large sub surface concentrations of pure mafic impact melt breccia and that the intimate mixing is inherent to thecayley plains at a gross scale thus the mixing ofmafic impact melt breccias and feldspathic prebasin com ponents must have occurred during formation and deposition of the cayley plains such uniformity could nothave been achieved by small postdeposition impacts into a stratified megaregolith using this conclusion asone constraint and the known distribution of th on the lunar surface as another and the assumption that the im brium impact is primarily responsible for formation of the cayley plains arguments are presented that theapollo 16 mimbs derive from the imbrium region and consequently that one fourth of the apollo 16 regolithis primary imbrium ejecta in the form of mafic impact melt breccias

new lunar meteorites impact melt and regolith breccias and large scale heterogeneities of the upper lunar crust we have analyzed nine highland lunar meteorites lunaites using mainly inaa several of these rocks are difficult to classify dhofar 081 is basically a fragmental breccia but much of its groundmass features a glassy fluidized texture that is indicative of localized shock melting also much of the matrix glass is swirly brown suggesting a possible regolith derivation we interpret dar al gani dag 400 as an extremely immature regolith breccia consisting mainly of impact melt breccia clasts we interpret dhofar 026 as an unusually complex anorthositic impact melt breccia with scattered ovoid globules that formed as clasts of mafic subophitic impact melt the presence of mafic crystalline globules in a lunar material even one so clearly impact heated suggests that it may have originated as a regolith our new data and a synthesis of literature data suggest a contrast in al2o3 incompatible element systematics between impact melts from the central nearside highlands where apollo sampling occurred and those from the general highland surface of the moon impact melts from the general highland surface tend to have systematically lower incompatible element concentration at any given al2o3 concentration than those from apollo 16 in the case of dhofar 026 both the bulk rock and a comparatively al poor composition 14 wt al2o3 7 g g sm extrapolated for the globules manifest incompatible element contents well below the apollo 16 trend impact melts from luna 20 57e distribute more along the general highland trend than along the apollo 16 trend siderophile elements also show a distinctive composition for apollo 16 impact melts ni ir averaging 1 8x chondritic in contrast lunaite impact melt breccias have consistently chondritic ni ir impact melts from luna 20 and other apollo sites show average ni ir almost as high as those from apollo 16 the prevalence of this distinctive ni ir ratio at such widely separated nearside sites suggests that debris from one extraordinarily large impact may dominate the megaregolith siderophile component of a nearside region 2300 km or more across highland polymict breccia lunaites and other kreep poor highland regolith samples manifest a strong anticorrelation between al2o3 and mg the magnesian component probably represents the chemical signature of the mg suite of pristine nonmare rocks in its most pure form unaltered by the major kreep assimilation that is so common among apollo mg suite samples the average composition of the ferroan anorthositic component is now well constrained at al2o3 29 30 wt implying about 17 19 wt modal mafic silicates in good agreement with the composition predicted for flotation crust over a ferroan magma ocean warren 1990

the constitution and structure of the lunar interior the current state of understanding of the lunar interior is the sum of nearly four decades of work and a range of exploration programs spanning that same time period missions of the 1960s including the rangers surveyors and lunar orbiters as well as earth based telescopic studies laid the groundwork for the apollo program and provided a basic understanding of the surface its stratigraphy and chronology through a combination of remote sensing surface exploration and sample return the apollo missions provided a general picture of the lunar interior and spawned the concept of the lunar magma ocean in particular the discovery of anorthite clasts in the returned samples led to the view that a large portion of the moon was initially molten and that crystallization of this magma ocean gave rise to mafic cumulates that make up the mantle and plagioclase flotation cumulates that make up the crust smith et al 1970 wood et al 1970 this model is now generally accepted and is the framework that unifies our knowledge of the structure and composition of the moon the intention of this chapter is to review the major advances that have been made over the past decade regarding the constitution of the moon s interior much of this new knowledge is a direct result of data acquired from the successful clementine and lunar prospector missions as well as the analysis of new lunar meteorites as will be seen results from these studies have led to many fundamental amendments to the magma ocean model much of what we know from sample analyses has been previously summarized elsewhere and only their most important aspects will be discussed in this chapter the reader is referred to the relevant chapters in the books basaltic volcanism on the terrestrial planets basaltic volcanism study project 1981 the

high resolution subsurface water ice distributions on mars theoretical models predict that the depth at which water ice is stable in the subsurface of mars will vary due to local surface features such as rocks and slopes and the thermal inertia of the ground above the water so far measurements have been limited to overviews of the several hundred kilometre footprint covered by the ray spectrometer on board the mars odyssey spacecraft but joshua bandfield has now used the seasonal temperature response of the martian surface from odyssey s themis package to map water ice distribution at the sub kilometre scale the observations reveal significant regional and local water ice depth variability at potential landing sites for the mars phoenix mission due for launch later this year the phoenix lander s robotic arm will be able to dig up to half a metre or so into the soil to search for water ice and these results suggest that it may encounter considerable variation in the depth to the ice layer the seasonal temperature response of the martian surface is used to map local surface heterogeneities such as rocks slopes and thermal inertia of ground cover at subkilometre scale these observations show significant regional and local water ice depth variability and indicate that the depth to the water ice table is highly variable in the potential phoenix spacecraft landing ellipses theoretical models indicate that water ice is stable in the shallow subsurface depths of 1 2 m of mars at high latitudes1 2 3 4 5 6 7 these models have been mainly supported by the observed presence of large concentrations of hydrogen detected by the gamma ray spectrometer suite of instruments on the mars odyssey spacecraft8 9 10 the models and measurements are consistent with a water ice table that steadily increases in depth with decreasing latitude more detailed modelling has predicted that the depth at which water ice is stable can be highly variable owing to local surface heterogeneities such as rocks and slopes and the thermal inertia of the ground cover11 12 13 measurements have however been limited to the footprint several hundred kilometres of the gamma ray spectrometer suite preventing the observations from documenting more detailed water ice distributions here i show that by observing the seasonal temperature response of the martian surface with the thermal emission imaging system on the mars odyssey spacecraft14 it is possible to observe such heterogeneities at subkilometre scale these observations show significant regional and local water ice depth variability and in some cases support distributions in the subsurface predicted by atmospheric exchange and vapour diffusion models the presence of water ice where it follows the depth of stability under current climatic conditions implies an active martian water cycle that responds to orbit driven climate cycles15 16 17 several regions also have apparent deviations from the theoretical stability level indicating that additional factors influence the ice table depth the high resolution measurements show that the depth to the water ice table is highly variable within the potential phoenix spacecraft landing ellipses and is likely to be variable at scales that may be sampled by the spacecraft

geochemistry and petrology of lunar meteorite queen alexandra range 94281 a mixed mare and highland regolith breccia with special emphasis on very low titanium mafic components queen alexandra range que 94281 a lunar meteorite recently discovered in antarctica is a glassy matrix clast rich regolith breccia containing a mixture of mafic volcanic glass and gabbroic constituents and a diverse set of highland constituents in thin section the clast assemblage is dominated by coarse mineral debris from a shallow intrusive or hypabyssal setting or from deep within a thick mare flow abundant coarse grained pyroxene clasts have fine scale exsolution lamellae and compositions similar to pyroxenes of known lunar very low ti vlt basalts and other lunar meteorites of basaltic composition pyroxene compositions follow fe enrichment extending to hedenbergite which is associated with fayalite and cristobalite indicating slow cooling we refer to the protolith of the crystalline vlt component as vlt gabbro fragments of pyroclastic glasses that have high fe and low ti concentrations similar to the pyroclastic green glasses known from apollo samples are common lithic clasts include abundant subrounded glassy to cryptocrystalline aluminous 17 30 wt al2o3 kreep poor melt breccias of highland origin and a variety of other feldspathic impactites on the basis of composition of our subsamples que 94281 consists of 54 wt mafic or mare components and 46 wt feldspathic or highland components the bulk composition of que 94281 is similar to that of yamato y 793274 but que 94281 has slightly greater concentrations of some siderophile elements and slightly lower concentrations of those elements contributed mainly by mafic constituents differences in siderophile element concentrations are consistent with longer surface exposure of que 94281 minor differences in trace element variations of subsamples of the two meteorites suggest subtle differences in the composition of their highland constituents nonetheless the overall similarity of compositions supports the possibility that they were ejected from the same source region on the moon the crystalline vlt component of que 94281 differs from those known from apollo 17 and luna 24 vlt lithologies and from that of basaltic breccia elephant moraine eet 87521 the vlt gabbro component and the ferroan vlt volcanic glasses in que 94281 have compositions that may be petrogenetically related by derivation from a common picritic parent composition represented by an ultramafic glass found in que 94281

expanded secondary craters in the arcadia planitia region mars evidence for tens of myr old shallow subsurface ice abstract a range of observations indicates widespread subsurface ice throughout the mid and high latitudes of mars in the form of both pore filling and excess ice it is generally thought that this ice was recently emplaced and is not older than a hundred thousand to a few millions of years old based on ice stability and orbital induced climate change we analyze the distribution of subsurface ice in arcadia planitia located in the northern mid latitudes by mapping thermokarstically expanded secondary craters providing additional evidence for extensive excess ice down to fairly low latitudes less than 40 n we further infer the minimum age of this subsurface ice based on the ages of the four primary craters that are thought to be the source of a large portion of these secondaries which yields estimates on the order of tens of millions of years old much more ancient than anticipated this estimated ancient age suggests that ice can be preserved in the shallow subsurface for long periods of time at least in some parts of arcadia planitia where expanded secondary craters are especially abundant we estimate the amount of ice lost to sublimation during crater expansion based on measurements of expanded secondary craters in hirise digital terrain models the loss is equivalent to a volume of ice between 140 and 360 km 3 which would correspond to a global layer of 1 2 5 mm thick we further argue that much more ice at least 6000 km 3 is likely preserved beneath the un cratered regions of arcadia planitia since significant loss of this excess ice would have caused extensive terrain dissection and the removal of the expanded secondary craters both the loss of ice due to secondary crater expansion and the presence of this ice today have implications for the martian climate

18oso4 and 18oh2o as prospective indicators of elevated arsenic in the goose river ground watershed maine anomalous geogenic arsenic occurs in drinking water from the goose river crystalline ground watershed in mid coastal maine isotope investigations were useful in understanding release areas of arsenic into affected water wells the isotope composition of sulfate associated with probable arsenian pyrite oxidation is described correlation of 18oso4 enrichment 4 57 to 7 46 vienna standard mean ocean water vsmow is discussed with specific and recurring areas of elevated arsenic 10 52 g l 1 although arsenic concentrations were highly variable over 2 years per well 18oso4 values were always consistent and suggested a specific and consistent risk for elevated arsenic occurrences for each well the 18o values in the water molecule 12 07 to 8 81 vsmow and the 18oso4 values may serve as prospective indicators of prominent zones of aeration at depth in discrete fracture zones the 18o values in the water molecule and sulfate ion appear to indicate that more than 60 of o2 incorporated into the so4 2 ion are from dissolved oxygen and belong to distinct fractured areas these aeration zones or oxidation fronts as outlined by oxygen isotopes are sentinels for high arsenic risk in groundwater

revised crism spectral parameters and summary products based on the currently detected mineral diversity on mars the investigation of hyperspectral data from the mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars crism and the observatoire pour la mineralogie l eau les glaces et l activitie omega on mars express has revealed an increasingly diverse suite of minerals present on the martian surface a revised set of 60 spectral parameters derived from corrected spectral reflectance at key wavelengths in crism targeted observations and designed to capture the known diversity of surface mineralogy on mars is presented here as summary products some of the summary products have strong heritage to omega spectral parameter calculations this paper also presents newly derived parameters that highlight locations with more recently discovered spectral signatures type locations for the diversity of currently identified mineral spectral signatures have been compiled into a library presented in this work our analysis indicates that the revised set of summary products captures the known spectral diversity of the surface and successfully highlights and differentiates between locations with differing spectral signatures the revised spectral parameter calculations and related products provide a useful tool for scientific interpretation and for future mission landing site selection and operations

initiation and growth of martian ice lenses abstract water ice in the upper meters of the martian regolith is a major volatile reservoir although the geographic extent burial depth and thermal stability of this shallow ice are well understood its origin history and stratigraphy are not over the past decade a growing body of observational evidence has indicated that shallow ground ice exceeds the pore volume of its host soil over large regions of both martian hemispheres this is confounding given that 1 the physical theory that accurately predicts the location of ground ice also assumes that ice should be pore filling in the upper meter of regolith and 2 the phoenix spacecraft uncovered far more pore filling ice than excess ice at its landing site in the northern hemisphere the development of ice lenses by low temperature in situ segregation analogous to the processes that generate frost heave on earth has been hypothesized to explain shallow excess ice on mars we have developed a numerical model of ice lens initiation and growth in the martian environment and used it to test this hypothesis for the first time we carried out a large suite of numerical simulations in order to place quantitative constraints on the timing and location of ice lens initiation and on the magnitude of ice lens growth in a variety of host soils we find that ice lens initiation is a ubiquitous process in the martian high latitudes but the ultimate magnitude of lens growth or frost heave is sensitive to the properties of the host soil depending on the specific properties of martian soils in situ segregation may be a very slow process sufficient to explain the excess ice observed in the dodo goldilocks trench at the phoenix landing site but without regionally significant effects alternatively if clay sized particles or perchlorate salts are present in situ segregation may be a vigorous process that has significantly affected the stratigraphy of ground ice in the upper meter of regolith throughout the high latitudes

preservation of midlatitude ice sheets on mars national science foundation nsf dge 1143953 nasa earth and space sciences fellowship nessf nnx16ap09h nasa mars data analysis program mdap award nnx15am62g

analysis of subsurface flow and formation anisotropy in a fractured aquitard using transient water level data a new methodology is proposed to estimate the actual direction of water flow in a fractured aquitard according to the conceptual model the flow direction in a fractured aquitard is dictated by the azimuth of the fractures since almost no flow occurs within the rock matrix which possesses very low hydraulic conductivity thus while groundwater in reality continues to flow along the fractures calculations based on water level data may incorrectly indicate changes in hydraulic gradients and azimuth of flow the present methodology is based on simultaneous analysis of hydraulic gradients and flow direction as calculated from equipotential surfaces the approach was tested in a fractured chalky aquitard and the calculated direction of principal fractures was found to be in good agreement with subsurface fracture data obtained from a tunnel excavated in the vicinity of the study area

antarctic meteorite alha81005 not just another lunar anorthositic norite seven subsamples of meteorite alha81005 a regolith breccia from the lunar highlands were analyzed by inaa for 32 elements four of them were also studied petrographically in bulk composition the rock corresponds to anorthositic norite with a very small component of kreep and is very similar to estimates of average lunar highlands surface compositions of the white clasts and the dark matrix are similar but the clasts are more magnesian and 30 50 as rich in kreep related elements the white clasts have fine grained granulitic textures and are generally similar to apollo 16 and 17 granulitic anorthositic norites but are more magnesian and only 20 as rich in kreep related elements some granulitic clasts are dominated by a magnesian anorthositic norite component not represented among the pristine apollo samples

provenance of geogenic arsenic in the goose river basin maine usa occurrences of arsenic as are sporadic in drinking water from many wells in mid coastal maine this is particularly the case where water supplies are pumped from fractured igneous and metamorphic bedrock although health risk based as contamination levels are lowered it is likely that the provenance of trace as concentrations will need to be scrutinized approximately 33 of wells sampled in the goose river ground watershed had at least one occurrence of 10 g l 1 as geologic mapping in combination with the rock petrology and mineral chemistry were important in deciphering probable local source areas for arsenic median whole rock as is greater than 39 mg kg 1 in the bucksport formation and anatectic granitoids of the waldoboro pluton complex 34s isotopic composition of arsenian pyrites indicate that local areas of anomalous arsenic bearing transported soils are not the source of trace as in groundwater but instead the as is derived from oxidation processes in the fractured bedrock along the western margin of the ground watershed in groundwater the as3 as5 ratios ranged from 0 01 to 4 45 and were inconsistent spatially and temporally although it is probable that the stability field in most groundwater supplies is haso42 arsenic speciation is not necessarily an aid to predicting transport instead an isotopic evaluation of associated groundwater so42 clearly indicates a consistent correlation of elevated as with enriched 34sso4 the 34sso4 ranges of 4 05 to 4 61 may be characteristic of local oxidation in the fractured groundwater flow systems potential areas of geogenic as transport may be predictable

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 recent ice age on mars evidence for climate oscillations from regional layering in mid latitude mantling deposits 1 two end member hypotheses have been proposed to account for the emplacement and distribution of ice in the near subsurface of mars at mid to high latitudes during recent spin axis orbital variation induced climate change in the first diffusion of atmospheric water vapor into and out of a porous regolith forms ice cemented soils whose latitudinal stability migrates as a function of orbitally controlled climatic conditions in the alternative hypothesis atmospheric deposition of ice snow and dust produces dusty ice rich layers during periods of higher obliquity new image data reveal meters thick layered deposits exposed on mid latitude pole facing slopes supporting the latter hypothesis these observations suggest that the near surface ice detected by the grs instrument suite and the phoenix lander at high latitudes is linked to thick buried ice that was atmospherically deposited during recent ice ages and that significant amounts of subsurface ice may remain today in the 30 50 mid latitude regions where fresh craters imaged by hirise expose abundant ice

mars nature and evolution of young latitude dependent water ice rich mantle 1 high resolution altimetry and imaging have revealed the presence of a meters thick sedimentary layer at middle to high northern and southern latitudes presently covering at least 23 of the planet the layer is interpreted to be water ice rich and to undergone degradation recently its activity very likely coincided with the last major obliquity excursion a few hundred thousand years ago the majority of the layer at higher latitudes however persisted for a much longer time in the late amazonian stratigraphic analysis suggests a complex history of successive episodes of deposition and removal repeated deposition and removal of the mantles are interpreted to be responsible for the unusual statistical properties of kilometer scale topography in the transitional mid latitude zones

high resolution imaging science experiment hirise images of volcanic terrains from the first 6 months of the mars reconnaissance orbiter primary science phase 1 in the first 6 months of the mars reconnaissance orbiter s primary science phase the high resolution imaging science experiment hirise camera has returned images sampling the diversity of volcanic terrains on mars while many of these features were noted in earlier imaging they are now seen with unprecedented clarity we find that some volcanic vents produced predominantly effusive products while others generated mostly pyroclastics flood lavas were emplaced in both turbulent and gentle eruptions producing roofed channels and inflation features however many areas on mars are too heavily mantled to allow meter scale volcanic features to be discerned in particular the major volcanic edifices are extensively mantled though it is possible that some of the mantle is pyroclastic material rather than atmospheric dust support imaging by the context imager ctx and topographic information derived from stereo imaging are both invaluable in interpreting the hirise data

lunar basalt breccia identified among antarctic meteorites the antarctic meteorite elephant moraine eet 87521 is a lunar mare basalt breccia this 30 7 g meteorite was originally identified as a brecciated eucrite1 but new petrographic evidence from a more representative thin section fig 1 indicates that it is a breccia of mainly very low titanium vlt basalt and should be reclassified as a lunar meteorite the four or five antarctic lunar meteorites collected previously at allan hills yamato mountains and macalpine hills alha81005 y79117 y793274 y82192 82193 y86032 and mac88104 88105 have all sampled only the plagioclase rich lunar highlands2 3 which dominate the surface of the moon eet87521 extends the lunar meteorite collections to include the less abundant basaltic provinces the maria of the lunar crust

modeling sublimation of ice exposed by new impacts in the martian mid latitudes abstract new impacts in the martian mid latitudes have exposed near surface ice this ice is observed to slowly fade over timescales of months in the present martian climate exposed surface ice is unstable during summer months in the mid latitudes and will sublimate we model the sublimation of ice at five new impact sites and examine the implications of its persistence even with generally conservative assumptions for most reasonable choices of parameters it is likely that over a millimeter of sublimation occurred in the period during which the ice was observed to fade the persistence of visible ice through such sublimation suggests that the ice is relatively pure rather than pore filling such ice could be analogous to the nearly pure ice observed by the phoenix lander in the dodo goldilocks trench and suggests that the high ice contents reported by the mars odyssey gamma ray spectrometer at high latitudes extend to the mid latitudes our observations are consistent with a model of the martian ice table in which a layer with high volumetric ice content overlies pore filling ice although other structures are possible

compositional variation in apollo 16 impact melt breccias and inferences for the geology and bombardment history of the central highlands of the moon abstract high precision data for the concentrations of a number of lithophile and siderophile elements were obtained on multiple subsamples from 109 impact melt rocks and breccias mostly crystalline from the apollo 16 site compositions of nearly all apollo 16 melt rocks fall on one of two trends of increasing sm concentration with increasing sc concentration the eastern trend lower sm sc mg fe and sm yb ratios consists of compositional groups 3 and 4 of previous classification schemes these melt rocks are feldspathic poor in incompatible and siderophile elements and appear to have provenance in the descartes formation to the east of the site the western trend higher sm sc mg fe and sm yb ratios consists of compositional groups 1 and 2 these relatively mafic kreep bearing breccias are a major component 35 of the cayley plains west of the site and are unusual compared to otherwise similar melt breccias from other sites in having high concentrations of fe ni metal 1 2 the metal is the carrier of the low ir au 0 3 chondritic siderophile element signature that is characteristic of the apollo 16 site four compositionally distinct groups 1m 1f 2db and 2nr of western trend melt breccias occur that are each represented by at least six samples compositional group 1 of previous classification schemes the poikilitic or lkfm melt breccias can be subdivided into two groups group 1m represented by six samples including 60315 is characterized by lower al2o3 concentrations higher mgo and alkali concentrations and higher mg fe and cr sc ratios than group 1f represented by fifteen samples including 65015 group 1m also has siderophile element concentrations averaging about twice those of group 1f and ir au and ir ni ratios that are even lower than those of other western trend melt rocks ir au 0 24 0 03 ci normalized at the mafic extreme of group 2 vha melt breccias the melt lithology occurring as clasts in feldspathic fragmental breccias from north ray crater group 2nr is compositionally distinct from the melt lithology of dimict breccias from the cayley plains group 2db in having higher concentrations of sc cr and heavy rare earth elements and lower concentrations of siderophile elements the distinct siderophile element signature high absolute abundances low ir au ratio suggest that the four groups of mafic melt breccia are all somehow related ratios of some lithophile elements also suggest that they are more closely related to each other than they are to melt breccias from other apollo sites however none of the breccia compositions can be related to any of the others by any simple process of igneous fractionation or mixing involving common lunar materials thus the origin of the four groups of mafic melt breccia is enigmatic if they were produced in only one or two impacts then a mechanism exists for generating regimes of impact melt breccia in a single impact that are substantially different from each other in composition for various reasons including the problem of delivering large volumes of four different types of melt to the apollo 16 site it is unlikely that any of these breccias were produced in basin forming impacts if they were produced in as many as four crater forming impacts then the unusual siderophile element signature is difficult to explain possible explanations are 1 1 the four groups of melt breccia all contain metal from a single earlier impact 2 2 they were each formed by related metal rich meteoroids or 3 3 some common postimpact process has resulted in metal of similar composition in each of four melt pools within a compositional group most intrasample and intersample variation in lithophile element concentrations is caused by differences among samples in the proportion of a component of normative anorthosite or noritic anorthosite in most cases this compositional variation probably reflects variation in clast abundance for group 2db and probably 2nr differences in abundance of a component of ferroan anorthosite estimated al2o3 32 accounts for the compositional variation for groups 1m and 1f the anorthositic component is more mafic estimated al2o3 26 some group 2 samples may be related by a troctolitic component of varying abundance

labile trace elements in basaltic achondrites can they distinguish between meteorites from the moon mars and v type asteroids we report data for 14 mainly labile trace elements ag au bi cd cs ga in rb sb se te tl u and zn in eight whole rock lunar meteorites asuka a 881757 dar al gani dag 262 elephant moraine eet 87521 queen alexandra range que 93069 que 94269 que 94281 yamato y 793169 and y 981031 and martian meteorite dag 476 and incorporate these into a comparative study of basaltic meteorites from the moon mars and v type asteroids multivariate cluster analysis of data for these elements in 14 lunar 13 martian and 34 howardite eucrite and diogenite hed meteorites demonstrate that materials from these three parents are distinguishable using these markers of late low temperature episodes this distinguishability is essentially as complete as that based on markers of high temperature igneous processes concentrations of these elements in 14 lunar meteorites are essentially lognormally distributed and generally more homogeneous than in martian and hed meteorites mean siderophile and labile element concentrations in the 14 lunar meteorites indicate the presence of a ci equivalent micrometeorite admixture of 2 6 when only feldspathic samples are considered our data show a slightly higher value of 3 4 consistent with an increasing micrometeorite content in regolith samples of higher maturity concentrations of labile elements in the 8 feldspathic samples hint at the presence of a fractionated highly labile element component possibly volcanic in origin at a level comparable to the micrometeorite component apparently the process es that contributed to establishing lunar meteorite siderophile and labile trace element contents occurred in a system open to highly labile element transport

abundance and distribution of iron on the moon the abundance and distribution of iron on the moon is derived from a near global data set from clementine the determined iron content of the lunar highlands crust 3 percent iron by weight supports the hypothesis that much of the lunar crust was derived from a magma ocean the iron content of lower crustal material exposed by the south pole aitken impact basin on the lunar farside is higher 7 to 8 percent by weight and consistent with a basaltic composition this composition supports earlier evidence that the lunar crust becomes more mafic with depth the data also suggest that the bulk composition of the moon differs from that of the earth9s mantle this difference excludes models for lunar origin that require the earth and moon to have the same compositions such as fission and coaccretion and favors giant impact and capture

hirise observations of new impact craters exposing martian ground ice twenty small new impact craters or clusters have been observed to excavate bright material inferred to be ice at mid latitudes and high latitudes on mars in the northern hemisphere the craters are widely distributed geographically and occur at latitudes as low as 39 n stability modeling suggests that this ice distribution requires a long term average atmospheric water vapor content around 25 precipitable micrometers more than double the present value which is consistent with the expected effect of recent orbital variations alternatively near surface humidity could be higher than expected for current column abundances if water vapor is not well mixed with atmospheric co2 or the vapor pressure at the ice table could be lower due to salts ice in and around the craters remains visibly bright for months to years indicating that it is clean ice rather than ice cemented regolith although some clean ice may be produced by the impact process it is likely that the original ground ice was excess ice exceeding dry soil pore space in many cases observations of the craters suggest small scale heterogeneities in this excess ice the origin of such ice is uncertain ice lens formation by migration of thin films of liquid is most consistent with local heterogeneity in ice content and common surface boulders but in some cases nearby thermokarst landforms suggest large amounts of excess ice that may be best explained by a degraded ice sheet

subsurface ice on mars with rough topography high latitude ground ice on mars discovered by the gamma ray spectrometer suite is thought to be thermally stable owing to the presence of vapor in the martian atmosphere however local slopes can alter surface and subsurface temperatures substantially and hence allow ground ice to persist at locations where it would otherwise be unstable global statistics of the topography of mars are computed processed and extrapolated to derive a description of surface roughness on spatial scales to which ground ice should be sensitive this slope distribution is convolved with a new thermal model for the dependence of subsurface ice on slope to produce a prediction of the global ice distribution that includes the effect of topographic roughness in the highest latitudes slopes reduce the amount of buried ice while in lower latitudes the ice fraction increases widening the geographic boundary of the ice table at the high latitudes where ice is stable beneath horizontal ground the estimated reduction of ice is small compared to the existing ice volume areas in the midlatitudes with high surface roughness that have previously been predicted to be ice free are predicted to contain quantities of ice that may be detectable at present and accessible in the future slopes cause ground ice to be stable to latitudes of about 25 degrees in both hemispheres including for example areas within the northern olympus mons aureole deposits hecates tholus and hellas basin ice is unstable at equatorial latitudes even when accounting for surface slopes

history and anatomy of subsurface ice on mars abstract ice buried beneath a thin layer of soil has been revealed by neutron spectroscopy and explored by the phoenix mars lander it has also been exposed by recent impacts this subsurface ice is thought to lose and gain volume in response to orbital variations milankovitch cycles we use a powerful numerical model to follow the growth and retreat of near surface ice as a result of regolith atmosphere exchange continuously over millions of years if a thick layer of almost pure ice has been deposited recently it has not yet reached equilibrium with the atmospheric water vapor and may still remain as far equatorward as 43 n where ice has been revealed by recent impacts a potentially observable consequence is present day humidity output from the still retreating ice we also demonstrate that in a sublimation environment subsurface pore ice can accumulate in two ways the first mode widely known is the progressive filling of pores by ice over a range of depths the second mode occurs on top of an already impermeable ice layer subsequent ice accumulates in the form of pasted on horizontal layers such that beneath the ice table the pores are completely full with ice most or all of the pore ice on mars today may be of the second type at the phoenix landing site where such a layer is also expected to exist above an underlying ice sheet it may be extremely thin due to exceptionally small variations in ice stability over time

trace element identification of three chemically distinct very low titanium vlt basalt glasses from apollo 17 abstract lunar basaltic samples of vlt very low titanium composition occur primarily as small glass fragments in the regolith at the apollo 17 landing site electron microprobe analyses of glasses from the double drive tube 79001 2 90 150 m size fraction of soils from mean depths of 0 8 16 8 cm indicate that 34 of 90 38 are of vlt composition a subset of twenty glasses was removed from the thin sections using a micro coring device and analyzed using special micro inaa techniques to obtain major and trace element abundances on the basis of the results we delineate three distinct groups which have been named for their relative amounts of co hico meco and loco apollo 17 vlts the most magnesian hico basalt glasses 4 of 34 or about 12 of the vlt glasses are probably pristine pyroclastics soil breccias 79135 and 70295 apparently contain only this type of vlt glass the medium co meco glasses 6 of 34 18 strongly resemble the largest sample of vlt composition the olivine vitrophyre 78526 as well as all three of the apollo 17 vlt lithic fragments that have been analyzed for trace elements the loco vlt glasses 23 of 34 68 are more enigmatic trace element concentrations require that these three vlt compositions cannot be related by simple igneous processes the distribution of the three types provides important information on the sequence of events that produced the regolith at the apollo 17 site

martian cratering 8 isochron refinement and the chronology of mars abstract this paper reviews and refines the technique of dating martian surfaces by using impact crater isochrons defined as size distributions of impact craters on undisturbed martian surfaces of specified ages in the 1970s this system identified not only abundant ancient martian volcanic surfaces but also extensive lava plains with ages of a few 108 y old this dating was initially controversial but confirmed in the 1980s and 90s by martian meteorites the present update utilizes updated estimates of the mars moon cratering ratio the most important calibration factor improves treatment of gravity and impact velocity scaling effects combines aspects of the crater size distribution data from earlier work by both neukum and hartmann and for the first time applies a correction for loss of small meteoroids in the martian atmosphere from popova et al 2003 meteorit planet sci 38 905 925 the updated isochrons are not radically different from the previous 2002 iteration but fit observed data better and give somewhat older model ages for features dated from small craters diameter d 100 m crater counts from young lava flows in various areas give good fits to the new isochrons over as much as 3 orders of magnitude in d confirming the general isochron shape and giving crater retention ages in the range of some 106 to some 108 y interpreted as lava flow ages more complex older units are also discussed uncertainties are greatest if only small craters d 100 m are used suggestions by other workers of gross uncertainties due to local secondary craters and deposition exhumation are discussed they do not refute our conclusions of significant volcanic fluvial and other geologic activity in the last few percent of martian geologic time or the importance of cratering as a tool for studying processes such as exhumation indeed crater count data suggest certain very recent episodes of deposition exhumation and ice flow possibly associated with obliquity cycles of 10 7 y timescale evidence from ancient surfaces suggests higher rates of volcanism fluvial activity glaciation and other processes in noachian hesperian time than in amazonian time

petrography mineralogy and trace element geochemistry of lunar meteorite dhofar 1180 here we report the petrography mineralogy and trace element geochemistry of the dhofar 1180 lunar meteorite dhofar 1180 is predominantly composed of fine grained matrix with abundant mineral fragments and a few lithic and glassy clasts lithic clasts show a variety of textures including cataclastic gabbroic granulitic ophitic subophitic and microporphyritic both feldspathic and mafic lithic clasts are present most feldspathic lithic clasts have a strong affinity to ferroan anorthositic suite rocks and one to magnesian suite rocks mafic lithic clasts are moderately to extremely fe rich the ti ti cr fe fe mg compositional trend of pyroxenes in mafic lithic clasts is consistent with that of low ti mare basalts glasses display a wide chemical variation from mafic to feldspathic some glasses are very similar to those from apollo 16 soils kreep components are essentially absent in dhofar 1180 one glassy clast is rich in k ree and p but its mg mg fe is very low 0 25 it is probably a last stage differentiation product of mare basalt molar fe mn ratios of both olivine and pyroxene are essentially consistent with a lunar origin

near tropical subsurface ice on mars near surface perennial water ice on mars has been previously inferred down to latitudes of about 45 and could result from either water vapor diffusion through the regolith under current conditions or previous ice ages precipitations in this paper we show that at latitudes as low as 25 in the southern hemisphere buried water ice in the shallow 1 m subsurface is required to explain the observed surface distribution of seasonal co2 frost on pole facing slopes this result shows that possible remnants of the last ice age as well as water that will be needed for the future exploration of mars are accessible significantly closer to the equator than previously thought where mild conditions for both robotic and human exploration lie copyright 2010 by the american geophysical union

the distribution and behavior of martian ground ice during past and present epochs mars undergoes significant oscillations in its orbit which will have a pronounced effect on its climate and in particular on the behavior of subsurface water ice we explore and map the behavior of ice in the martian near surface regolith over the past 1 m y using a diffusion and condensation model presented in an earlier paper with two primary modifications to include orbitally induced variations in insolation and atmospheric water abundance we find that the past behavior of ground ice differs significantly from that at the present epoch primarily the result of high amplitude oscillations in obliquity presently 25 in midlatitude and equatorial regions ground ice will condense from atmospheric water during times of higher obliquity filling the top few meters of the regolith with significant amounts of ice at an obliquity of 32 ground ice becomes stable globally during times of lower obliquity ground ice will sublime and diffuse back into the atmosphere dessicating the regolith to a depth of about 1 to 2 m equatorward of 60 to 70 latitude in the high latitude regions these oscillations are considerably subdued below this depth of cyclic saturation and dessication a long term stability of ice exists in some geographic regions we present a map of the distribution of ice expected at the present epoch cyclic exchange of water between the global regolith and polar regions will have significant implications for surface geology and the polar layered deposits

detection of 3h and 85kr in groundwater from arsenic bearing crystalline bedrock of the goose river basin maine presence of young groundwater post 1950 in the goose river basin is demonstrated with 3h and 85kr analyses a total of 96 wells and four springs were sampled quarterly from 1999 to 2001 to determine the extent of any recent recharge and to what depth hydraulic continuity existed in the groundwatershed 33 3 km2 recharge groundwater is less than 50 years in about 31 3h to 37 85kr of sampled wells and 75 of sampled springs young groundwater ages are recorded in wells up to 320 m in depth within fractured and arsenic bearing crystalline bedrock total arsenic 10 g l 1 occurs significantly in drinking water with young groundwater flowing through the pumping well intervals astotal occurs in 89 85kr to 93 3h of all wells with post 1950 groundwater ages young groundwater recharge and elevated geogenic arsenic were discovered only in the anatectic granitoids and migmatized country rock of the southwestern part of the goose river basin

lunar meteorite queen alexandra range 94281 glass compositions and other evidence for launch pairing with yamato 793274 abstract lunar meteorite queen alexandra range 94281 is remarkably similar to yamato 793274 pairing in the conventional earth entry sense is difficult to reconcile with the 2500 km separation between the find locations for these two samples nonetheless both of these regolith breccias are dominated by very low ti vlt mare basalt the pyroxenes of which feature exsolution lamellae on a remarkably coarse scale typical lamella width 0 5 1 m by mare standards the pyroxenes also show similar compositional variations e g fe vs ti trends which confirm parentage from vlt mare basalt plots using al2o3 or feo as a tracer of the highland component indicate indistinguishable internal mare highland geochemical mixing trends the same two distinctive glass types dominate the mare glass populations of both breccias glass type yq1 features 0 37 0 63 wt tio2 10 17 wt mgo and 9 11 wt al2o3 glass type yq2 features higher tio2 0 99 1 22 wt which is inversely correlated with mgo 12 6 13 8 wt and nearly constant 8 8 wt al2o3 all of these similarities suggest that y 793274 and que 94281 are a launch pair which we designate yq most of these similarities also extend to another mare breccia meteorite elephant moraine 87521 however the eet 87521 mare basalt is unusually v poor 88 g g whereas the yq mare component contains 166 g g queen alexandra range 94281 features a variety of textural domains discrete patches of dark matrix material appear to represent clods of mature regolith that have been mixed with a coarser relatively immature material interior to a frothy fusion crust are areas of massive glass that probably formed as a splash coating on que 94281 when it was still on the moon the coarse yq and eet 87521 pyroxene exsolution features imply relatively slow cooling in either a very shallow sill or an unusually thick ponded lava and or later annealing within a cryptomare mare pyroclastic glasses including the two yq varieties are systematically mgo rich compared to crystalline mare basalts this disparity may be a consequence of limited survival of graphite the main fuel for explosive volcanism during formation of the mare source regions as magma ocean cumulates graphite 2 2 g cm3 survived preferentially in regions that avoided extensive early melting and thus remained mgo rich an apparent bimodality in the tio2 contents of mare volcanics especially the pyroclastic glasses also seems a plausible consequence of petrogenesis by remelting of magma ocean cumulates cumulates deposited after the magma ocean evolved to ilmenite saturation had vastly higher tio2 contents than cumulates deposited shortly before the yq regolith s subequal proportions of mare and highland matter are consistent with derivation from a terrain close to a mare highland boundary however a similar mixture might also develop through vertical mixing in a cryptomare or a region of thin mare coverage thus unfortunately the yq bulk composition is not a very useful clue to the identity of the source crater

paleowaters in silurian devonian carbonate aquifers geochemical evolution of groundwater in the great lakes region since the late pleistocene abstract changes in the climatic conditions during the late quaternary and holocene greatly impacted the hydrology and geochemical evolution of groundwaters in the great lakes region increased hydraulic gradients from melting of kilometer thick pleistocene ice sheets reorganized regional scale groundwater flow in paleozoic aquifers in underlying intracratonic basins here we present new elemental and isotopic analyses of 134 groundwaters from silurian devonian carbonate and overlying glacial drift aquifers along the margins of the illinois and michigan basins to evaluate the paleohydrology age distribution and geochemical evolution of confined aquifer systems this study significantly extends the spatial coverage of previously published groundwaters in carbonate and drift aquifers across the midcontinent region and extends into deeper portions of the illinois and michigan basins focused on the freshwater saline water mixing zones in addition the hydrogeochemical data from silurian devonian aquifers were integrated with deeper basinal fluids and brines in upper devonian black shales and underlying cambrian ordovician aquifers to reveal a regionally extensive recharge system of pleistocene age waters in glaciated sedimentary basins elemental and isotope geochemistry of confined groundwaters in silurian devonian carbonate and glacial drift aquifers show that they have been extensively altered by incongruent dissolution of carbonate minerals dissolution of halite and anhydrite cation exchange microbial processes and mixing with basinal brines carbon isotope values of dissolved inorganic carbon dic range from 10 to 2 87sr 86sr ratios range from 0 7080 to 0 7090 and 34 s so 4 values range from 10 to 30 a few waters have elevated 13cdic values 15 from microbial methanogenesis in adjacent organic rich upper devonian shales radiocarbon ages and 18o and d values of confined groundwaters indicate they originated as subglacial recharge beneath the laurentide ice sheet 14 50 ka bp 15 to 13 18o these paleowaters are isolated from shallow flow systems in overlying glacial drift aquifers by lake bed clays and or shales the presence of isotopically depleted waters in paleozoic aquifers at relatively shallow depths illustrates the importance of continental glaciation on regional scale groundwater flow modern groundwater flow in the great lakes region is primarily restricted to shallow unconfined glacial drift aquifers recharge waters in silurian devonian and unconfined drift aquifers have 18o values within the range of holocene precipitation 11 to 8 and 7 to 4 5 for northern michigan and northern indiana ohio respectively carbon and sr isotope systematics indicate shallow groundwaters evolved through congruent dissolution of carbonate minerals under open and closed system conditions 13cdic 14 7 to 11 1 and 87sr 86sr 0 7080 0 7103 the distinct elemental and isotope geochemistry of pleistocene versus holocene age waters further confirms that surficial flow systems are out of contact with the deeper basinal scale flow systems these results provide improved understanding of the effects of past climate change on groundwater flow and geochemical processes which are important for determining the sustainability of present day water resources and stability of saline fluids in sedimentary basins

alha 81005 meteorite chemical evidence for lunar highland origin based on the well established characteristic lunar and meteoritic ratios of feo mno cr2o3 v and k la and ree patterns alha 81005 meteorite is undoubtedly of lunar highland origin the alha 81005 meteorite is an anorthositic gabbro 72 pl and matches closely in chemical composition to apollo 15 15418 and luna 16 21013 highland rocks the rock is a non kreepy and vlt type the siderophiles au ni and ir content is high 1 5 cl equivalent and similar to other lunar highland breccias the clast has a different ancient meteorite component than the bulk and matrix the meteorite has a young terrestrial age implying a recent lunar cratering event therefore during major lunar basins formation in early eons the earth must have received a significant amount of lunar material which is now mixed in the crust the finding of a lunar meteorite lends credibility to the suggestion that snc achondrites may come from mars

compositions of subsurface ices at the mars phoenix landing site 1 nasa s phoenix lander uncovered two types of ice at its 2008 landing site on the northern plains of mars a brighter slab like ice that broke during robotic arm operations and a darker icy deposit spectra from the phoenix surface stereo imager ssi are used to demonstrate that the brighter material consists of nearly pure water ice which probably formed by migration and freezing of liquid water the darker icy material consists of 30 20 wt ice with the remainder composed of fine grained soil indicating that it probably formed as pore ice these two types of ice represent two different emplacement mechanisms and periods of deposition

the presence and stability of ground ice in the southern hemisphere of mars abstract we calculate new estimates of ground ice stability and the depth distribution of the ice table the depth boundary between ice free soil above and ice cemented soil below and compare these theoretical estimates of the distribution of ground ice with the observed distribution of leakage neutrons measured by the neutron spectrometer instrument of the mars odyssey spacecraft s gamma ray spectrometer instrument suite our calculated ground ice distribution contains improvements over previous work in that we include the effects of the high thermal conductivity of ice cemented soil at and below the ice table we include the surface elevation dependence of the near surface atmospheric humidity and we utilize new high resolution maps of thermal inertia albedo and elevation from mars global surveyor observations results indicate that ground ice should be about 5 times shallower than in previous predictions while results are dependent on the atmospheric humidity depths are generally between a few millimeters and a few meters with typical values of a few centimeters results are also geographically similar to previous predictions with differences due to the higher resolution of thermal inertia and the inclusion of elevation effects on humidity comparison with the measured epithermal neutron count rates in the southern hemisphere indicate that the geographic distribution of the count rate is best correlated with ground ice in equilibrium with 10 to 20 pr m precipitable micrometers column abundance of atmospheric water assuming a uniform distribution with co2 however given the uncertainties 5 to 30 pr m also may be viable this water abundance represents a longer term average over 100 to 1000 yr there is a high degree of correlation between the depth of the ice table and the epithermal count rate that agrees remarkably well with predicted count rates as a function of ice table depth these results indicate that ground ice in the upper meter of the martian soil is in diffusive equilibrium with the atmosphere since ground ice in this depth zone is expected to undergo saturation desiccation cycles with orbital variations this ice should be younger than about 500 kyr and was emplaced under similar cold and dry climate conditions of today remaining differences between the predicted depths of the ice table and those inferred from the neutron data are likely to be due to subpixel heterogeneity in the martian surface including the presence of rocks slopes and patches of soil with varying thermophysical properties

feldspathic lunar meteorites and their implications for compositional remote sensing of the lunar surface and the composition of the lunar crust we present new compositional data for six feldspathic lunar meteorites two from cold deserts yamato 791197 and 82192 and four from hot deserts dhofar 025 northwest africa 482 and dar al gani 262 and 400 the concentrations of feo or al2o3 and th or any other incompatible element together provide first order compositional information about lunar polymict samples breccias and regoliths and regions of the lunar surface observed from orbit concentrations of both elements on the lunar surface have been determined from data acquired by orbiting spacecraft although the derived concentrations have large uncertainties and some systematic errors compared to sample data within the uncertainties and errors in the concentrations derived from orbital data the distribution of feo and th concentrations among lunar meteorites which represent 18 source regions on the lunar surface is consistent with that of 18 random samples from the surface approximately 11 of the lunar meteorites are low feo and low th breccias consistent with large regions of the lunar surface particularly the northern farside highlands almost all regoliths from apollo sites on the other hand have larger concentrations of both elements because they contain fe rich volcanic lithologies from the nearside maria and th rich lithologies from the high th anomaly in the northwestern nearside the feldspathic lunar meteorites thus offer our best estimate of the composition of the surface of the feldspathic highlands and we provide such an estimate based on the eight most well characterized feldspathic lunar meteorites the variable but high on average mg fe ratio of the feldspathic lunar meteorites compared to ferroan anorthosites confirms a hypothesis that much of the plagioclase at the surface of the feldspathic highlands is associated with high mg fe feldspathic rocks such as magnesian granulitic breccia not ferroan anorthosite geochemically the high mg fe breccias appear to be unrelated to the mafic magnesian suite rocks of the apollo collection models for the formation of the upper lunar crust as a simple flotation cumulate composed mainly of ferroan anorthosite do not account for the complexity of the crust as inferred from the feldspathic lunar meteorites

planetary surface dating from crater size frequency distribution measurements multiple resurfacing episodes and differential isochron fitting abstract the analysis of crater size frequency distributions and absolute densities forms the basis of current approaches for estimating the absolute and relative ages of planetary surfaces users of the neukum system of crater dating have conventionally used a cumulative presentation of the data but because of the recent proliferation of interest in identifying resurfacing ages it is worth emphasising the utility of the differential presentation of crater data in identifying resurfacing events and particularly in distinguishing the signature of short lived events such as volcanic flows from long acting processes such as aeolian erosion the work describes some additional considerations for making isochron fits to differentially plotted crater populations with respect to the removal of a binning bias for incrementally differentially plotted data the hartmann approach has not typically employed the fitting of isochrons but differential fitting would be a natural choice for this system and is implemented in the craterstats software a revised calculation of the martian epoch boundary times in both chronology systems is provided

ground ice at the phoenix landing site stability state and origin 1 a primary objective of the phoenix mission was to examine the characteristics of high latitude ground ice on mars we report observations of ground ice its depth distribution and stability characteristics and examine its origins and history high latitude ground ice was explored through a dozen trench complexes and landing thruster pits over a range of polygon morphological provinces shallow ground ice was found to be abundant under a layer of relatively loose ice free soil with a mean depth of 4 6 cm which varied by more than 10x from trench to trench these variations can be attributed mainly to slope effects and thermal inertia variations in the overburden soil affecting ground temperatures the presence of ice at this depth is consistent with vapor diffusive equilibrium with respect to a mean atmospheric water content of 3 4 1019 m 3 consistent with the present day climate significant ice heterogeneity was observed with two major forms ice cemented soil and relatively pure light toned ice ice cemented soils which comprised about 90 of the icy material exposed by trenching are best explained as vapor deposited pore ice in a matrix supported porous soil light toned ice deposits represent a minority of the subsurface and are thought to consist of relatively thin near surface deposits the origin of these relatively pure ice deposits appears most consistent with the formation of excess ice by soil ice segregation such as would occur by thin film migration and the formation of ice lenses needle ice or similar ice structures

geogenic arsenic in groundwaters in the western alps summary groundwater arsenic as of geogenic origin in the western alps is generally associated with aquifers in crystalline rock the external crystalline massifs ecm are in particular noted for occurrences of elevated concentrations of as in groundwaters the present study is based on as in groundwaters that have been measured in the ecm in both france and switzerland arsenic bearing sulfide minerals such as pyrite arsenian pyrite and arsenopyrite are the most likely sources of as leached within the crystalline ecm rocks while it is not known how as concentrations vary with time at all of the reported water sources we measured on a weekly basis the concentration of as at one thermal source over a period of one year and found the as concentrations to be variable however the cause of the variability is at present not understood even though many studies have applied 34 s so4 as a tool for understanding as mobilization in the ecm there is no consensus at present finally we present some perspectives on the possible effects of climate change and anthropogenic activities on as mobility in the ecm in particular droughts have the potential to increase as concentrations in groundwaters

patterns of accumulation and flow of ice in the mid latitudes of mars during the amazonian evidence has accumulated that non polar portions of mars have undergone significant periods of glaciation during the amazonian period this evidence includes tropical mountain glacial deposits lobate debris aprons lineated valley fill concentric crater fill pedestal craters and related landforms some of which suggest that ice thicknesses exceeded a kilometer in many places in some places several lines of evidence suggest that ice is still preserved today in the form of relict debris coved glaciers the vast majority of deposit morphologies are analogous to those seen in cold based glacial deposits on earth suggesting that little melting has taken place although these features have been broadly recognized and their modes of ice accumulation and flow analyzed at several scales they have not been analyzed and well characterized globally despite their significance for understanding the evolution of the martian climate a major outstanding question is the global extent of accumulation and flow of ice during periods of non polar glaciation as a mechanism to address this question we outline two end member scenarios to provide a framework for further discussion and analysis 1 ice accumulation was mainly focused within individual craters and valleys and flow was largely local to regional in scale and 2 ice accumulation was dominated by global latitudinal scale cold based ice sheets similar in scale to the laurentide continental ice sheets on earth in order to assess these end members we conducted a survey of ice related features seen in context camera ctx images in each hemisphere and mapped evidence for flow directions within well preserved craters in an effort to decipher orientation preferences that could help distinguish between these two hypotheses regional hemispheric glaciation or local accumulation and flow these new crater data reveal a latitudinal dependence on flow direction at low latitudes in each hemisphere 40 45 slopes of all orientations show signs of ice accumulation and ice related flow this latitudinal onset of concentric flow of ice within craters in each hemisphere correlates directly with the lowest latitudes at which typical pedestal craters have been mapped taken together these observations demarcate an important latitudinal boundary that partitions each hemisphere into two zones 1 poleward of 45 where net accumulation of ice is interpreted to have occurred on all surfaces and 2 equatorward of 45 where net accumulation of ice occurred predominantly on pole facing slopes these results provide important constraints for deciphering the climatic conditions that characterized mars during periods of extensive amazonian non polar glaciation

a lunar meteorite found outside the antarctic our knowledge of the moon s surface composition has come from samples returned by the apollo and luna missions and from eleven lunar meteorites all of which were discovered in antarctica1 2 here we report the discovery of a new lunar meteorite calcalong creek in a desert region of australia which is analogous to antarctica in its ability to preserve meteorites of different types3 on the basis of a diagnostic fe mn ratio of 73 78 and other element abundances we conclude that calcalong creek is a lunar breccia containing both highland and mare materials whereas the apollo and luna missions selectively sampled only 5 of the lunar crust lunar meteorites should provide a random sample4 nevertheless there has been some concern that the antarctic meteorite population may be biased in some way5 calcalong creek will add to our understanding of lunar petrology and as the first non antarctic lunar meteorite may also shed new light on the transfer of impact ejecta from the moon to the earth