a stable isotope study of mammal skeletal remains of mid pleistocene age arago cave eastern pyrenees france evidence of taphonomic and diagenetic effects abstract this study reports a set of 85 oxygen isotope measurements carried out on fossil bones of cervus elaphus ovis sp and equus sp from archaeological excavations in the arago cave eastern pyrenees south eastern france of ages ranging from about 650 to 450 ka a large section of the thick sediment sequence filling the cave was flushed for an unknown time by meteoric water through a large opening in the limestone ceiling caused by karst erosion under these conditions part of the biogenic material underwent partial solution and diagenesis these processes may have caused considerable effects on the original isotopic composition of bone phosphate the range of the isotopic values obtained from each stratigraphic level is quite wide particularly in the case of horse remains whose 18o po3 4 values cover a range of about 5 in the same stratigraphic level however a few isotopically heavy values were obtained from the three species which suggest the possibility of very warm climatic episods or alternatively of climatically dry periods altogether the results clearly show that it is not possible to obtain quantitative palaeoclimatological and palaeoenvironmental information from fossils which underwent taphonomic and diagenetic effects that these effects may take place readily and that time is one of the less important parameters affecting bone preservation the uncertainties existing in the case of relatively old fossil bones not always shared by isotope geochemists are thus directly confirmed

analyzing the ages of south polar craters on the moon implications for the sources and evolution of surface water ice abstract surface water ice in the permanently shadowed polar regions of the moon has a patchy surficial distribution and is not found within all available cold trapping areas to date it is not well understood when the ice was delivered which has important implications for the surficial characteristics of the ice as well as for possible delivery mechanisms here we present absolute model ages for 20 south polar craters that host surface water ice providing maximum estimates of the ages of surface ice contained within these craters we quantify the amount of available cold trapping surface area that is occupied by water ice in order to examine the relationship between the patchiness of ice within each crater and the age of each host crater the majority of surface ice is contained in old craters 3 1 gyr where the majority of cold trapping area on the pole exists the ice is these ancient craters is very patchy in surficial distribution occupying siegler et al 2016 if true polar wander did occur on the moon then the ages of ice bearing craters presented here set an upper limit for the age of post true polar wander hydrogen emplacement of 4 1 0 1 gyr

effects of orbital evolution on lunar ice stability 1 many regions near the lunar poles are currently cold enough that surface water ice would be stable against sublimation losses for billions of years however most of these environments are currently too cold to efficiently drive ice downward by thermal diffusion leaving impact burial as the primary means of protection from surface loss processes in this respect most of the present near surface thermal environments on the moon may actually be quite poor traps for water ice this was not always the case long term orbital changes have dramatically altered the lunar polar thermal environment we develop a simple model of the evolution of the lunar orbit and spin axis to examine the thermal environments available for volatile deposition and retention in the past our calculations show that some early lunar polar environments were in the right temperature regime to have collected subsurface ice if a supply were available however a high obliquity period which occurred when the moon was at about half its present distance from the earth would either have driven this ice out into space or deep into the lunar subsurface since that time as the lunar obliquity has slowly decreased to its present value environments have undergone their own thermal evolution and each of the current cold traps experienced a period when they were most efficient at thermally burying ice we examine the thermal history of a lunar polar crater to provide a framework for examining other processes effecting volatiles in the moon s near surface cold traps

organic and organo mineral colloids in discontinuous permafrost zone on going permafrost thaw in discontinuous permafrost regions produces significant amounts of small permafrost subsidence and depressions while large lakes are likely to drain into streams and rivers the intensification of permafrost thaw may alter the size distribution and chemical composition of organo fe al colloids in lakes and rivers we used a continuum of surface water bodies from permafrost subsidence small depressions and thaw ponds to large lakes and rivers that drain the western siberia lowland wsl to assess oc major and the trace element size distribution between the 20 m 5 m 1 2 m 0 45 m 0 22 m 0 025 m and 1 kda 1 4 nm size fractions this approach allowed us to distinguish the organic and organo ferric colloids that were responsible for the transport of trace elements in surface waters and address their evolution during possible physico chemical and biological processes both conventionally dissolved 0 22 m and low molecular weight 1 kda fractions exhibited an order of magnitude decrease in doc fe in the landscape continuum depressions and permafrost subsidence thaw ponds thermokarst lakes streams rivers thermodynamic modeling and on site size separation suggested that a number of trace elements tes including alkaline earth elements and several micronutrients zn ba mn and ni decreased the degree of their binding to dom along the landscape continuum whereas the majority of insoluble tes al fe co cd cu pb rees th and u remained complexed with dom in the lmw 1 kda fraction two primary sites of colloid generation included i ground vegetation and peat leaching which supplied dom complexes of divalent metals and organo al entities to thaw ponds and lakes and ii fe2 oxidation and te co precipitation with fe hydroxides in the presence of surface dom at groundwater discharge sites within the riparian hyporheic zones of rivers under a warming climate scenario an increase in the thickness of the thawing depth will intensify the input of inorganic components from deep mineral horizons and possibly underground waters thus producing the enrichment of large lakes in fe rich colloids and particles the speciation of divalent metal micronutrients cu ni and co and toxic metals al cd pb and u that are complexed within dom will most likely remain conservative overall the wsl s surface water colloidal composition may shift from dom rich and dom al rich to fe rich and the export of low soluble trivalent and tetravalent hydrolysates from the soil to rivers will increase

integration of lunar polar remote sensing data sets evidence for ice at the lunar south pole in order to investigate the feasibility of ice deposits at the lunar south pole we have integrated all relevant lunar polar data sets these include illumination data arecibo ground based monostatic radar data newly processed clementine bistatic radar data and lunar prospector neutron spectrometer measurements the possibility that the lunar poles harbor ice deposits has important implications not only as a natural resource for future human lunar activity but also as a record of inner solar system volatiles e g comets and asteroids over the past billion years or more we find that the epithermal neutron flux anomalies measured by lunar prospector are coincident with permanently shadowed regions at the lunar south pole particularly those associated with shackleton crater furthermore these areas also correlate with the 0 circular polarization ratio cpr enhancements revealed by new processing of clementine bistatic radar echoes which in turn are colocated with areas of anomalous high cpr observed by arecibo observatory on the lower sun shadowed wall of shackleton crater estimates of the extent of high cpr from arecibo observatory and clementine bistatic radar data independently suggest that 10 km2 of ice may be present on the inner earth facing wall of shackleton crater none of the experiments that obtained the data presented here were ideally suited for definitively identifying ice in lunar polar regions by assessing the relative merits of all available data we find that it is plausible that ice does occur in cold traps at the lunar south pole and that future missions with instruments specifically designed to investigate these anomalies are worthy

fluxes of fast and epithermal neutrons from lunar prospector evidence for water ice at the lunar poles maps of epithermal and fast neutron fluxes measured by lunar prospector were used to search for deposits enriched in hydrogen at both lunar poles depressions in epithermal fluxes were observed close to permanently shaded areas at both poles the peak depression at the north pole is 4 6 percent below the average epithermal flux intensity at lower latitudes and that at the south pole is 3 0 percent below the low latitude average no measurable depression in fast neutrons is seen at either pole these data are consistent with deposits of hydrogen in the form of water ice that are covered by as much as 40 centimeters of desiccated regolith within permanently shaded craters near both poles

the clementine bistatic radar experiment during the clementine 1 mission a bistatic radar experiment measured the magnitude and polarization of the radar echo versus bistatic angle beta for selected lunar areas observations of the lunar south pole yield a same sense polarization enhancement around beta 0 analysis shows that the observed enhancement is localized to the permanently shadowed regions of the lunar south pole radar observations of periodically solar illuminated lunar surfaces including the north pole yielded no such enhancement a probable explanation for these differences is the presence of low loss volume scatterers such as water ice in the permanently shadowed region at the south pole

the retention of primary oxygen isotope compositions of fossil elephant skeletal phosphate fossil elephant remains from sediments of plio pleistocene age in the vicinity of lake turkana kenya provide insights into the ability of the phosphate oxygen system to preserve original 18o values 18op in the depositional environment individual fossil specimens exhibit systematic variations in the 18op values of their various tooth and bone components differences in 18op values between these skeletal components can be as high as 3 6 despite the fact that equivalent phases for individual modern elephants have 18op values which vary by less than 0 6 xrd traces of the different skeletal phases of modern and fossil samples also infer differential preservation of primary apatite crystallinities among the various fossil phases fossil samples of dentine cementum and bone have x ray spectra with sharper and more intense peaks compared to their modern counterparts but little change in crystallinity is observed for fossil enamel samples a model based on the premise that the enamel phase preserves primary isotope signatures and that the accompanying skeletal phases are partially re equilibrated with the fluids associated with the microbial decomposition of the elephant s carcass is consistent with the features of the 18op dataset this isotopic evidence in conjunction with the physical and chemical attributes of enamel has led us to postulate that enamel could be preserving primary isotope signatures while other skeletal components are affected to varying degrees by alteration processes in the burial environment

age constraints of mercury s polar deposits suggest recent delivery of ice abstract surface ice at the poles of mercury appears as several m thick deposits that are composed of nearly pure water we provide new age estimates of the surfaces of mercury s polar deposits from combined analyses of poisson statistics and direct observations of crater densities within permanently shadowed radar bright regions imaged by the messenger spacecraft these age estimates conservatively suggest that ice was delivered to mercury within the last 330 myr the geologically young ages suggest that the surfaces have been recently refreshed and this may be accomplished by the delivery of ice in a young impactor or impactors a single recent impactor is more consistent with the relative purity of the ice as suggested by the earth based radar observations in contrast to ice on mercury observations of the lunar poles are suggestive of a highly patchy distribution of surface frost the patchiness of lunar polar deposits is consistent with long exposure times to the space weathering environment given enough time the polar deposits on mercury may age into a more heterogeneous spatial distribution similar to that on the moon

an explanation of bright areas inside shackleton crater at the lunar south pole other than water ice deposits 1 whether water molecules of cometary and or solar wind origin migrated to and accumulated in cold permanently shadowed areas at the lunar poles has long been debated from the perspective of scientific interest and expectations for future utilization recently high reflectance condition was observed inside the lunar south pole shackleton crater for the 1064 4 nm of the lunar orbiter laser altimeter on the lunar reconnaissance orbiter and the high reflectance was explained to perhaps be due to a surface frost layer in excess of 20 water ice here we investigate the crater with the selenological engineering explorer multi band imager that has nine bands in the visible to near infrared range including a 1050 nm band 62 m pixel resolution part of the illuminated inner wall of shackleton crater exhibits high reflectance at 1050 nm but also exhibits the diagnostic 1250 nm spectral absorption a signature that is consistent with naturally bright purest anorthosite

dinosaur bones fossils or pseudomorphs the pitfalls of physiology reconstruction from apatitic fossils abstract a prerequisite to any attempt to reconstruct thermophysiology of ancient animals through analysis of stable isotopes of oxygen is the assumption that apatitic fossils are isotopically unaltered parts of their original skeletons we suggest that sufficient evidence is available to seriously question this assumption because living bones contain about 1 3 by weight of organic matrix mass balance considerations show that at least half of an apatitic fossil must be new material added post mortem furthermore living apatitic skeletons contain almost no rare earth elements and uranium whereas apatitic fossils bear high concentrations of these elements additionally we found that while in living fish correlation between 18o of oxygen in the phosphate and that in the carbonate of apatite is poor these two values are linearly correlated in fossil fish this suggests diagenetic recrystallization has taken place perfect preservation of micro textures such as haversian canals does not prove the pristine condition of a fossil some of the most beautifully preserved fossils are highly silicified most apatitic fossils probably are pseudomorphs replacing original skeletal elements whereas distribution of stable isotopes of oxygen in fossils might provide information about their burial environment it could be misleading in attempts to interpret the organisms physiology this cautionary note is supported by the similarity of 18op in bones of coexisting fossil fish dinosaurs and various other reptiles at different latitudes the overlap of predicted 18op values in fish and mammals living in contact with the same environmental water also weakens the hope that ectotherms can be distinguished from endotherms by the isotopic composition of oxygen in their bones and teeth

early diagenetic evolution of bone phosphate an x ray diffractometry analysis abstract a new crystallinity index ci based on the x ray powder diffractometric pattern of fossil bone carbonate hydroxylapatite is defined this ci value provides a semi quantitative way to estimate the diagenetic changes in archaeological and palaeontological bone phosphate the studied samples are 71 human bones from the french merovingian cemetery of saint linaire 1200 1700 bp 37 human bones from two necropoleis in niger 1000 5000 bp two cave bear bones from aldene cave southern france around 70 000 bp five bones of miocene mammals and 14 bones of mesozoic reptiles the main results are that 1 there is no correlation between the increase in the ci and the age of the sample even in one given locality 2 the ci seems to be related to the taphonomical conditions in archaeological and fossil bones 3 an increase in the ci is correlated with a loss in organic matter in one archaeological site but the quality of preservation of organic matter in fossil bones does not depend on the changes in the ci 4 the correlation between the increase in the ci and the decrease of co3amount in bones from the niger necropolies suggests a possible mechanism for the increase in crystallinity the changes of crystallinity reflect early diagenetic changes and depend on the burial environments

characterisation of fe bearing particles and colloids in the lena river basin ne russia abstract rivers are significant contributors of fe to the ocean however the characteristics of chemically reactive fe remain poorly constrained especially in large arctic rivers which drain landscapes highly susceptible to climate change and carbon cycle alteration the aim of this study was a detailed characterisation size mineralogy and speciation of riverine fe bearing particles 0 22 m and colloids 1 kda 0 22 m and their association with organic carbon oc in the lena river and tributaries which drain a catchment almost entirely underlain by permafrost samples from the main channel and tributaries representing watersheds that span a wide range in topography and lithology were taken after the spring flood in june 2013 and summer baseflow in july 2012 fe bearing particles were identified using transmission electron microscopy as large 200 nm 1 m aggregates of smaller 20 30 nm spherical colloids of chemically reactive ferrihydrite in contrast there were also large 500 nm 1 m aggregates of clay illite particles and smaller 100 200 nm iron oxide particles dominantly hematite that contain poorly reactive fe tem imaging and scanning transmission x ray microscopy stxm indicated that the ferrihydrite is present as discrete particles within networks of amorphous particulate organic carbon poc and attached to the surface of primary produced organic matter and clay particles together these larger particles act as the main carriers of nanoscale ferrihydrite in the lena river basin the chemically reactive ferrihydrite accounts for on average 70 15 of the total suspended fe in the lena river and tributaries these observations place important constraints on fe and oc cycling in the lena river catchment area and fe bearing particle transport to the arctic ocean

patterns of diagenesis in bone i the effects of site environments abstract we have measured a suite of diagenetic parameters for several populations of archaeological bones buried in a number of northwest european sites since the last ice age these are the structural damage due to microbes changes in bone micro and macro porosity protein content a measure of the crystallinity of hydroxyapatite as reflected in the phosphate infra red spectrum peak splitting and a measure of the carbonate content as given by the ratio of carbonate to phosphate infra red absorption peaks the results provide a database that clearly characterises the patterns which are often site dependent of diagenetic change in buried bone our main conclusions are that individual site hydrology appears to have a strong influence on the outcome of bone preservation and that porosity is the most effective single diagenetic parameter which both determines and reflects the preservation of bone in the burial environment

using boulder tracks as a tool to understand the bearing capacity of permanently shadowed regions of the moon permanently shadowed regions psrs are abundant at the lunar poles they experience no direct sunlight and reach temperatures as low as 30 k psrs are of interest as evidence suggests that some may contain water ice h2o oh which could provide a record of the evolution of volatiles in the inner solar system this water ice is also a critical resource for life support systems and rocket propellant a better understanding of mechanical properties of psr regolith such as its bearing capacity will help optimize the design of future exploration rovers and landers thirteen boulder tracks were identified on the edge of or inside south polar lunar psr enhanced imagery and used to estimate the strength of the psr regolith at latitudes of 70 to 76 in sites with maximum annual temperatures of 65 to 210 k psr boulder track features are similar to those observed in highland mare and pyroclastic regions of the moon implying similar properties of the regolith measured features were used to estimate bearing capacity for psr regolith at depths of 0 28 to 4 68 m estimated bearing capacity values suggest that these psrs may be somewhat stronger than highland and mare regions at depths of 0 28 to 1 00 m bearing capacity in these psrs is statistically the same as those in other regions of the moon at depths of 1 00 to 2 00 m the results of this study can be used to infer bearing capacity as one measure for the trafficability of lower latitude psrs of the type measured here

oxygen isotope variations in phosphate of biogenic apatites i fish bone apatite rechecking the rules of the game abstract the major advantage of the oxygen in phosphate isotope paleothermometry is that it is a system which records temperatures with great sensitivity while bone and teeth building organisms are alive and the record is nearly perfectly preserved after death fish from seven water bodies of different temperatures 3 23 c and different 18 o values 16 to 3 of the water were analysed the 18 o values of the analysed po 4 vary from 6 to 25 the system passed the following tests a the temperatures deduced from isotopic analyses of the sequence of fish from lake baikal are in good agreement with the temperatures measured in the thermally stratified lake b the isotopic composition of fish bone phosphate is not influenced by the isotopic composition of the phosphate which is fed to the fish but only by temperature and water composition isotopic analysis of fossil fish in combination with analysis of mammal bones should be a useful tool in deciphering continental paleoclimates

lro lamp detection of geologically young craters within lunar permanently shaded regions abstract the upper 25 100 nm of the lunar regolith within the permanently shaded regions psrs of the moon has been demonstrated to have significantly higher surface porosity than the average lunar regolith by observations that the lyman albedo measured by the lunar reconnaissance orbiter lro lyman alpha mapping project lamp is lower in the psrs than the surrounding region we find that two areas within the lunar south polar psrs have significantly brighter lyman albedos and correlate with the ejecta blankets of two small craters

iron behavior in a northern estuary large pools of non sulfidized fe ii associated with organic matter the estuaries of the northern baltic sea gulf of bothnia receive an abundance of diagenetically reactivecatchment derived fe which is to a large degree complexed with organic matter or present a

extreme iron isotope fractionation between colloids and particles of boreal and temperate organic rich waters abstract significant and systematic variations of iron isotopic composition in surface water sample fractions obtained by frontal cascade filtration and ultrafiltration have been recorded in 1 subarctic organic rich boreal river and stream mire lake and soil solutions in northern taiga zone karelia nw russia and 2 temperate river and lake waters of the southern boreal zone central russia water samples were filtered in the field employing progressively decreasing pore size from 100 m to 1 kda followed by iron isotope analysis in all river samples there was a gradual increase of 57fe relative to irmm 14 with decreasing pore size from 0 4 0 1 at 100 m up to 4 2 0 1 at 10 kda fraction in the subarctic zone and from 0 024 0 2 at 100 m up to 1 2 0 2 at 10 kda in the temperate zone in the series of filtrates ultrafiltrates of subarctic and temperate streams and rivers the 57fe value decreases with increasing molar fe corg ratio therefore small size fe poor c rich colloids 1 10 kda and low molecular weight lmw fractions of oxygenated water exhibit strong enrichment in heavy isotope whereas high molecular weight fe rich colloids 100 kda 0 22 m and particles 1 100 m are isotopically lighter and closer to the continental crust fe isotope composition the relative enrichment of 1 10 kda ultrafiltrates in heavy isotopes suggests that low molecular weight ligands bind fe more strongly fe o c bonds than fe iii oxy hydr oxides fe o fe bonds in accord with quantum mechanics principles highly positive 57fe of the lmw fraction of labile and potentially bioavailable fe in small subarctic rivers may turn out to be a very important source of isotopically heavy fe in the arctic ocean the mechanisms involved in the production of this isotopically heavy fe may lead this tracer to become a new indicator of environmental changes occurring in the boreal zone

an upper limit for ice in shackleton crater as revealed by lro mini rf orbital radar 1 although diverse measurements have indicated h oh or h2o species in the lunar polar regions pinpointing its location form and abundance in specific reservoirs has proven elusive here we report on the first orbital radar measurements of shackleton crater near the lunar south pole mini rf observations indicate a patchy heterogeneous enhancement in cpr circular polarization ratio on the crater walls whose strength decreases with depth toward the crater floor a result that is most consistent with a roughness effect due to less mature regolith present on the crater wall slopes however the results do not rule out a modest ice contribution and an upper limit of 5 10 wt h2o ice up to 30 vol present in the uppermost meter of regolith is also consistent with the observations

xas study of iron speciation in soils and waters from a boreal catchment iron fe is a key element strongly influencing the biogeochemistry of soils sediments and waters but the knowledge about the variety of fe species present in these systems is still limited in

no evidence for thick deposits of ice at the lunar south pole the rim of the shackleton crater at the lunar south pole is a candidate crash site for nasa s lcross probe lunar crater observation and sensing satellite due to launch in 2008 the plume of debris kicked up by the crash is to be analysed in the hope that it will reveal the water thought to be there suggestions of lunar ice date from 1996 when data from the clementine spacecraft gave some indications of the presence of ice on crater walls at the south pole now using high resolution radar imagery the radar scattering parameter thought indicative of thick ice deposits has been found also to match radar echoes from the rock strewn walls and ejecta of young impact craters at all lunar latitudes there is no evidence for thick ice though there could be grains of water ice spread more thinly through the lunar soil shackleton crater at the moon s south pole has been suggested as a possible site of concentrated deposits of water ice on the basis of modelling of bi static radar polarization properties and interpretations of earlier earth based radar images1 2 this suggestion and parallel assumptions about other topographic cold traps is a significant element in planning for future lunar landings hydrogen enhancements have been identified in the polar regions3 but these data do not identify the host species or its local distribution the earlier earth based radar data lack the resolution and coverage for detailed studies of the relationship between radar scattering properties cold traps in permanently shadowed areas and local terrain features such as the walls and ejecta of small craters here we present new 20 m resolution 13 cm wavelength radar images that show no evidence for concentrated deposits of water ice in shackleton crater or elsewhere at the south pole the polarization properties normally associated with reflections from icy surfaces in the solar system4 5 6 were found at all the observed latitudes and are strongly correlated with the rock strewn walls and ejecta of young craters including the inner wall of shackleton there is no correlation between the polarization properties and the degree of solar illumination if the hydrogen enhancement observed by the lunar prospector orbiter3 indicates the presence of water ice then our data are consistent with the ice being present only as disseminated grains in the lunar regolith

vis nir reflectance of water ice regolith analogue mixtures and implications for the detectability of ice mixed within planetary regoliths permanently shadowed regions at the poles of the moon and mercury have been pointed out as candidates for hosting water ice at their surface we have measured in the laboratory the visible and near infrared spectral range vis nir bidirectional reflectance of intimate mixtures of water ice and the jsc 1af lunar simulant for different ice concentrations particle sizes and measurement geometries the nonlinearity between the measured reflectance and the amount of ice in the mixture can be reproduced to some extent by the mixing formulas of standard reflectance models in particular those of hapke and hiroi which are tested here estimating ice concentrations from reflectance data without knowledge of the mixing coefficientsstrongly dependent on the size shape of the grainscan result in large errors according to our results it is possible that considerable amounts of water ice might be intimately mixed in the regolith of the moon and mercury without producing noticeable photometric signatures

oxygen isotopic composition of fossil equid tooth and bone phosphate an archive of difficult interpretation abstract variation in the concentration of the stable isotopes of hydrogen oxygen and carbon have been tested in continental records as tools for quantitative or semi quantitative paleoclimatological studies among the different methods the potential use of oxygen isotopes in mammal bone and tooth phosphate has recently been recognized measurements carried out on fossil mammal bones of holocene age and their paleoclimatological interpretation corresponded well with paleontological and paleobotanical records in the case of considerably older fossils diagenetic processes may change the primary oxygen isotopic composition of phosphate fossil horse bones and teeth principally of the species equus stenonis were studied to ascertain how far back in time fossil mammal remains may be considered reliable material for paleoclimatological studies the samples come from 13 different locations in southeastern spain their age ranging from maspinian late pleistocene to middle villafranchian pliocene apart from the variations of the 18o po43 values which may be related to climatic changes it is apparent that the isotopic composition of bones and teeth from the same deposit are frequently rather different from one another the isotopic differences range from a few tenths of one to several this suggests a strong influence of taphonomy over the measured isotopic values of fossils in each deposit time can be considered neither the only variable nor the most important one responsible for the change of the primary isotopic composition of fossils under these conditions it is rather difficult to establish lower or upper limits for the age of fossils to be studied for reliable paleoclimatological information since the limits are directly related to taphonomic history this in turn is related to local environmental conditions and not only to the age of fossils

the age of lunar south circumpolar craters haworth shoemaker faustini and shackleton implications for regional geology surface processes and volatile sequestration abstract the interiors of the lunar south circumpolar craters haworth shoemaker faustini and shackleton contain permanently shadowed regions psrs and have been interpreted to contain sequestered volatiles including water ice altimetry data from the lunar orbiter laser altimeter lola onboard the lunar reconnaissance orbiter provide a new means of examining the permanently shadowed interiors of these craters in unprecedented detail in this study we used extremely high resolution gridded lola data of haworth shoemaker faustini and shackleton to determine the size frequency distributions and the spatial density of craters superposing their rims inner slopes and floors based on their population of superposed d 2 km craters haworth shoemaker and faustini have pre nectarian formation ages shackleton is interpreted as having a late imbrian age on the basis of craters with diameter d 0 5 km superposed on its rim the local density of craters with sub km diameters across our study area is strongly dependent on slope because of its steep interior slopes the lifetime of craters on the interior of shackleton is limited the slope dependence of the small crater population implies that the population in this size range is controlled primarily by the rate at which craters are destroyed this is consistent with the hypothesis that crater removal and resurfacing is a result of slope dependent processes such as diffusive mass wasting and seismic shaking linked to micrometeorite and meteorite bombardment epithermal neutron flux data and uv albedo data show that these circumpolar psrs particularly shoemaker may have 1 2 water ice by mass in their highly porous surface regolith and that shoemaker may have 5 or more water ice by mass in the near subsurface the ancient formation ages of shoemaker faustini and haworth and the late imbrian 3 5 ga crater retention ages of their floors suggests that any water ice that might have been deposited in their permanently shadowed areas was insufficient to modify the superposed crater population since that time

reflections of surface water seasonality and climate in stable oxygen isotopes from tyrannosaurid tooth enamel abstract patterns of isotopic variation in enamel of eight albertosaurus teeth from the campanian maastrichtian horseshoe canyon formation alberta were measured by serial sampling along the growth axis cycles in the isotopic values appear to correlate to published tooth growth rates for tyrannosaurids tyrannosaurid dinosaur teeth of 50 mm in length provide ideal repositories of terrestrial climatic information as each records a full annual cycle of body water isotopic variation the relatively thin enamel precludes problems associated with time averaging associated with complex growth patterns found in thick mammalian enamel the most consistent and striking pattern associated with all of the teeth are two relatively closely spaced subequal maxima these appear to be associated with onset of a seasonal episode of high humidity after the activation of the amount effect where the influence of ambient temperature on surface water and body water 18 o ends while temperatures remain above 20 c teeth within a single fossiliferous horizon show the same general isotopic pattern and range a notable difference in pattern shape and magnitude of isotopic variation between tyrannosaurid teeth from several stratigraphic intervals of the lower horseshoe canyon formation section indicates a climatic changes from strong seasonality high annual temperature range with distinct precipitation and humidity maxima during each year at the base of the section to milder seasonality at the top

images of surface volatiles in mercury s polar craters acquired by the messenger spacecraft images acquired by nasa s messenger spacecraft have revealed the morphology of frozen volatiles in mercury s permanently shadowed polar craters and provide insight into the mode of emplacement and evolution of the polar deposits the images show extensive spatially continuous regions with distinctive reflectance properties a site within prokofiev crater identified as containing widespread surface water ice exhibits a cratered texture that resembles the neighboring sunlit surface except for its uniformly higher reflectance indicating that the surficial ice was emplaced after formation of the underlying craters in areas where water ice is inferred to be present but covered by a thin layer of dark organic rich volatile material regions with uniformly lower reflectance extend to the edges of the shadowed areas and terminate with sharp boundaries the sharp boundaries indicate that the volatile deposits at mercury s poles are geologically young relative to the time scale for lateral mixing by impacts and either are restored at the surface through an ongoing process or were delivered to the planet recently

lack of exposed ice inside lunar south pole shackleton crater the inside of shackleton crater at the lunar south pole is permanently shadowed it has been inferred to hold water ice deposits the terrain camera tc a 10 meter resolution stereo camera onboard the selenological and engineering explorer selene spacecraft succeeded in imaging the inside of the crater which was faintly lit by sunlight scattered from the upper inner wall near the rim the estimated temperature of the crater floor based on the crater shape model derived from the tc data is less than 90 kelvin cold enough to hold water ice however at the tc s spatial resolution the derived albedo indicates that exposed relatively pure water ice deposits are not on the crater floor water ice may be disseminated and mixed with soil over a small percentage of the area or may not exist at all

space weathering effects on lunar cold trap deposits 1 both steady and episodic sources have been proposed as sources of hydrogen observed by lunar prospector in association with the regions of permanent shadow at the poles of the moon either source could supply significant quantities of water to the poles however space weathering processes affect the retention of water in the cold traps we investigate those effects by simulating the evolution of a column of regolith in the region of permanent shadow over time we determine the hydrogen concentration as a function of depth using a monte carlo model of discrete impacts and of delivery from the solar wind we treat the delivery sublimation sputtering and very small scale impacts as continual processes comparing the amount of water delivered to the poles to the amount remaining after space weathering we find a retention efficiency of 5 6 the retention efficiency of the polar cold traps is adequate for preserving volatile deposits over long periods of time the average hydrogen concentration in the regolith column is 4100 ppm in the top meter after 1 gyr this is a saturation level in the regolith increasing the amount of time deepens the enriched layer but does not lead to increased concentrations in 1 gyr about 1 6 m of the regolith is gardened therefore the top meter which is probed by the neutron spectroscopy technique has reached steady state in the simulations the 4100 ppm saturation level is about half of the amount of hydrogen inferred from the lunar prospector neutron data

the preservation of glacial interglacial climatic signatures in the oxygen isotopes of elephant skeletal phosphate abstract phosphate 18o values 18op of modern elephant bone and teeth are found to vary linearly according to the 18o of local meteoric water 18omw a parameter with close ties to regional and local climatic conditions enamel dentine cementum and bone separates from individual fossil elephant specimens of late pleistocene age have op values which vary by up to elephant specimens the larger spread in the 18op values of the various skeletal phases for the fossil samples is interpreted as evidence for post depositional alterantion of primary 18op signatures of some if not all of these fossil skeletal components in the fossil samples investigated enamel and dentine phases have systematically lower 18o values than associated bone and cementum phases differential re equilibration with soil waters either by the wholesale replacement of primary apatite or by processes of isotopic exchange is suggested as a mechanism to account for the observed spread in the fossil phosphate 18o data

isotope geochemistry of oxygen and carbon in phosphate and carbonate of phosphorite francolite oxygen isotope ratios in phosphate delta sup 18 o sub p were determined in 219 samples of phosphoritic rocks from all major phosphogenic provinces of the world ranging in age from lower proterozoic to recent in 58 samples oxygen was analyzed in the two oxygen lattice sites of francolite both in phosphate and in structural carbonate delta sup 18 o sub c delta sup 13 c was also analyzed in the latter and in coexisting calcite for 10 of them both delta sup 18 o sub p and delta sup 18 o sub c decrease sharply from the recent to the cretaceous and decrease with a gentler slope to the precambrian the nature of the time variation is elucidated by means of a delta sup 18 o sub p vs delta sup 18 o sub c plot which suggests that a the main cause of the time trends is the increase in temperature between recent and the cretaceous b the pre cretaceous trend is overprinted by both low temperature nonequilibrium exchange between sup 18 o depleted water and the rocks and higher temperature exchange between phosphate and carbonate c the observed trend cannot be explained by sup 18 o depleted cretaceous and paleozoic oceans the calcite coexisting with apatite in phosphatic rocks is similar in both delta sup 18 o and delta sup 13 c to the structural carbonatemore of the apatite even though phosphate may exchange its oxygen with environmental water to a greater extent than the authors originally claimed it is probably still a very good isotopic recorder of sedimentary environments less

the lunar reconnaissance orbiter mission six years of science and exploration at the moon abstract since entering lunar orbit on june 23 2009 the lunar reconnaissance orbiter lro has made comprehensive measurements of the moon and its environment the seven lro instruments use a variety of primarily remote sensing techniques to obtain a unique set of observations these measurements provide new information regarding the physical properties of the lunar surface the lunar environment and the location of volatiles and other resources scientific interpretation of these observations improves our understanding of the geologic history of the moon its current state and what its history can tell us about the evolution of the solar system scientific results from lro observations overturned existing paradigms and deepened our appreciation of the complex nature of our nearest neighbor this paper summarizes the capabilities measurements and some of the science and exploration results of the first six years of the lro mission

polar hydrogen deposits on the moon neutron and gamma ray data measured using the lunar prospector spectrometers were analyzed to define the enhanced hydrogen deposits near both poles of the moon combining the new low altitude neutron data 30 15 km with previous high altitude 100 20 km neutron data and the results of several recent radar investigations sharply constrains the characteristics of each of the polar deposits the deposits at the north appear to be in the form of many small pockets or of generally distributed hydrogen that average to a 100 ppm weight fraction enhancement over that which exists in regolith at more equatorial latitudes those deposits in the permanently shaded craters near the south pole are consistent with a thick ferroan anorthosite regolith containing an enhancement of 1670 890 ppm hydrogen which if in the form of water ice amounts to 1 5 0 8 weight fraction of h sub 2 o neutron data alone cannot discriminate between hydrogen implanted in lunar soil from the solar wind hydrated minerals or h sub 2 o these craters appear to be surrounded by regolith that either contains small pockets of enhanced hydrogen or is soil that is uniformly impregnated with hydrogen enhanced on average by about 100 ppm above that contained in soils at more equatorial latitudes c more 2000 american geophysical union less

constraints on the volatile distribution within shackleton crater at the lunar south pole shackleton crater is nearly coincident with the moon s south pole its interior receives almost no direct sunlight and is a perennial cold trap making shackleton a promising candidate location in which to seek sequestered volatiles however previous orbital and earth based radar mapping and orbital optical imaging have yielded conflicting interpretations about the existence of volatiles here we present observations from the lunar orbiter laser altimeter on board the lunar reconnaissance orbiter revealing shackleton to be an ancient unusually well preserved simple crater whose interior walls are fresher than its floor and rim shackleton floor deposits are nearly the same age as the rim suggesting that little floor deposition has occurred since the crater formed more than three billion years ago at a wavelength of 1 064 nanometres the floor of shackleton is brighter than the surrounding terrain and the interiors of nearby craters but not as bright as the interior walls the combined observations are explicable primarily by downslope movement of regolith on the walls exposing fresher underlying material the relatively brighter crater floor is most simply explained by decreased space weathering due to shadowing but a one micrometre thick layer containing about 20 per cent surficial ice is an alternative possibility

iron isotope fractionation in river colloidal matter temporal variations in the iron isotopic composition 56fe between 0 13 and 0 31 have been measured in the suspended fraction in a boreal river the major mechanism behind these variations is temporal mixing between two types of particles colloids fe oxyhydroxides and fe c colloids data in this study indicate that these two types of colloids have different fe isotope composition the fe c colloid has a negative 56fe value whereas the fe oxyhydroxide colloid is enriched in 56fe these two types of colloidal matter have different hydrogeochemical origin the fe c colloid reaches the river during storm events when the upper sections of the soil profile o and e horizons are flooded by a rising water table colloidal fe oxyhydroxides reach the river via inflow and subsequent oxidation of groundwater enriched in dissolved fe ii