diviner lunar radiometer observations of cold traps in the moon s south polar region diviner lunar radiometer experiment surface temperature maps reveal the existence of widespread surface and near surface cryogenic regions that extend beyond the boundaries of persistent shadow the lunar crater observation and sensing satellite lcross struck one of the coldest of these regions where subsurface temperatures are estimated to be 38 kelvin large areas of the lunar polar regions are currently cold enough to cold trap water ice as well as a range of both more volatile and less volatile species the diverse mixture of water and high volatility compounds detected in the lcross ejecta plume is strong evidence for the impact delivery and cold trapping of volatiles derived from primitive outer solar system bodies

the lunar far uv albedo indicator of hydration and weathering 1 we present an analysis of lunar reconnaissance orbiter lro lyman alpha mapping project lamp measurements of the dayside lunar surface at far ultraviolet wavelengths we use the strong 165 nm h2o absorption edge to look for diurnal variations in hydration we find that diurnal variations in spectral slope are indeed present they are superimposed on latitudinal and spatial variations related to composition and weathering we use two different spectral regions 164 173 nm and 175 190 nm to separate out these effects highlands and mare regions have distinct reflectance spectra with mare regions being spectrally bluer than highlands regions a consequence of the greater abundance of opaque minerals in mare regions bright ray terrains and areas known to be young such as giordano bruno crater are found to be relatively spectrally flat or red in the far uv this is consistent with a lack of space weathering which tends to make the far uv spectrum bluer due to the spectral behavior of nanophase iron large scale latitudinal variations in fuv slope are distinct and are likely due to a gradient in space weathering the diurnal variation in hydration is consistent with a solar wind origin and with loss of h2o at temperatures above 320 k far uv spectroscopy is thus shown to represent a viable method for mapping aqueous alteration even on the dayside of the moon and potentially elsewhere in the solar system

global distribution of large lunar craters implications for resurfacing and impactor populations by using high resolution altimetric measurements of the moon we produced a catalog of all impact craters 20 kilometers in diameter on the lunar surface and analyzed their distribution and population characteristics the most densely cratered portion of the highlands reached a state of saturation equilibrium large impact events such as orientale basin locally modified the prebasin crater population to 2 basin radii from the basin center basins such as imbrium orientale and nectaris which are important stratigraphic markers in lunar history are temporally distinguishable on the basis of crater statistics the characteristics of pre and postmare crater populations support the hypothesis that there were two populations of impactors in early solar system history and that the transition occurred near the time of the orientale basin event

biomarker based reconstructions of holocene lake level changes at lake gahai on the northeastern tibetan plateau holocene hydrological changes in regions dominated by the westerlies significantly differ from those by the asian summer monsoon the high elevated northeastern tibetan plateau located in between is likely influenced by the interactions of both circulation systems here we attempt to use biomarkers n alkanes and alkenones to reconstruct holocene lake level changes at lake gahai in the qaidam basin we choose a sediment core drilled at the lake shore where biomarkers would be sensitive to lake level changes the n alkane records show high average chain length acl high carbon preference index cpi and low proportion of aquatic macrophyte paq values at 7 2 kyr thousand calibrated years ago with peaked values around 6 kyr whereas low acl low cpi and high paq values occurred after 2 kyr and before 7 kyr no alkenones were detected at 7 2 kyr suggesting that lake level at this period was incapable of constantly reaching to the coring site therefore combined results provide unambiguous evide

summary of the results from the lunar orbiter laser altimeter after seven years in lunar orbit in june 2009 the lunar reconnaissance orbiter lro spacecraft was launched to the moon the payload consists of 7 science instruments selected to characterize sites for future robotic and human missions among them the lunar orbiter laser altimeter lola was designed to obtain altimetry surface roughness and reflectance measurements the primary phase of lunar exploration lasted one year following a 3 month commissioning phase on completion of its exploration objectives the lro mission transitioned to a science mission after 7 years in lunar orbit the lola instrument continues to map the lunar surface the lola dataset is one of the foundational datasets acquired by the various lro instruments lola provided a high accuracy global geodetic reference frame to which past present and future lunar observations can be referenced it also obtained high resolution and accurate global topography that were used to determine regions in permanent shadow at the lunar poles lola further contributed to the study of polar volatiles through its unique measurement of surface brightness at zero phase which revealed anomalies in several polar craters that may indicate the presence of water ice in this paper we describe the many lola accomplishments to date and its contribution to lunar and planetary science

a lacustrine gdgt temperature calibration from the scandinavian arctic to antarctic renewed potential for the application of gdgt paleothermometry in lakes quantitative climate reconstructions are fundamental to understand long term trends in natural climate variability and to test climate models used to predict future climate change recent advances

late holocene coupled moisture and temperature changes on the northern tibetan plateau the northern tibetan plateau involves complex interactions between the mid latitude westerly circulation and the subtropical asia monsoon circulation acting as a bridge communicating high and low latitude climatic processes previous studies from the region suggest relatively wet conditions in cold periods during the late holocene for instance the little ice age lia however the inference of such temperature moisture association is subject to the large uncertainty in lacustrine 14c chronology due to the particularly large lake reservoir effect in the region here we take a different approach by reconstructing paired temperature and moisture records from the same sediment cores to assess the temperature moisture association independent of chronology uncertainty we use alkenone indices uk 37 and c37 4 to reconstruct high resolution temperature and moisture changes simultaneously from two lakes in the qaidam basin northern tibetan plateau over the last 2500 years characterized by marked climatic variability our paired records confirm the warm dry and cold wet association in arid northwestern china during the late holocene opposite to the warm wet and cold dry association in subtropical asian monsoonal regions our moisture records further suggest substantially drier conditions during the medieval warm period mwp than the current warm period lastly the temperature and moisture changes inferred from our records can be well correlated with solar irradiance changes suggesting a possible link between solar forcing and natural climate variability during the late holocene on the northern tibetan plateau

mercury s albedo from mariner 10 implications for the presence of ferrous iron mariner 10 clear filter 490 nm images of mercury were recalibrated and photometrically normalized to produce a mosaic of nearly an entire hemisphere of the planet albedo contrasts are slightly larger than seen in the lunar highlands excluding maria variegations indicative of compositional differences include diffuse low albedo units often overlain by smooth plains the high albedo smooth plains of borealis planitia and high albedo enigmatic crater floor deposits a higher level of contrast between immature crater ejecta and average mature material on mercury compared to the moon is consistent with a more intense space weathering environment on mercury that results in a more mature regolith immature lunar highlands materials are 1 5 times higher in reflectance than analogous immature mercurian materials immature materials of the same composition would have the same reflectance on both bodies thus this observation requires that mercury s crust contains a significant darkening agent either opaque minerals or ferrous iron bearing silicates in abundances significantly higher than those of the lunar highlands if the darkening agent is opaque minerals e g ilmenite or ulvospinel mercury s crust may contain significant ferrous iron and yet not exhibit a 1 m absorption band

unravelling the mystery of lunar anomalous craters using radar and infrared observations in miniature radio frequency mini rf radar images anomalous craters are those having a high circular polarization ratio cpr in their interior but not exterior to their rims previous studies found that most cpr anomalous craters contain permanently shadowed regions psrs and that their population is overabundant in the polar regions however there is considerable controversy in the interpretation of these signals both water ice deposits and rocks surface roughness have been proposed as the source of the elevated cpr values to resolve this controversy we have systematically analyzed 4000 impact craters with diameters between 2 5 and 24 km in the mini rf radar image and diviner rock abundance ra map we first constructed two controlled orthorectified global mosaics using 6818 tracks of mini rf raw data and then analyzed the correlations between radar cpr and surface slope rock abundance and depth diameter ratios of impact craters our results show that cpr anomalous craters are distributed relatively uniformly across the lunar surface with no apparent difference in cpr between the polar potentially icy and non polar not icy craters most cpr anomalous craters are relatively young with a large depth diameter ratio and they actually represent an intermediate stage of crater evolution comparison with a two component radar scattering model suggests that rocks and surface roughness are major contributors to the observed cpr values using craters of 4 7 22 km in diameter with known ages we find that craters spend up to 120 ma with a high exterior ra and 3 ga in the cpr anomalous phase

stability of polar frosts in spherical bowl shaped craters on the moon mercury and mars following svitek martian water frost control of global distribution by small scale processes ph d thesis california institute of technology 1992 analytic solutions are presented for the effective albedo the effective emissivity and the radiative equilibrium temperature in the shadowed portions of a spherical bowl shaped crater the model assumes that the surface is a lambert scatterer with visual albedo and infrared emissivity each independent of wavelength across their respective spectral ranges absorption emission and multiple scattering from the walls of the crater are treated rigorously to all orders for airless bodies whose surfaces are in radiative equilibrium all shadowed portions of any individual crater have the same temperature whose value depends on four quantities the insolation product of the solar constant and the sine of the solar elevation angle the depth diameter ratio of the crater the visual albedo and the infrared emissivity as long as the crater is deep enough to have shadows the lowest temperatures are for the shallowest crater those with the smallest depth diameter ratio the model is applied first to the moon and mercury using a depth diameter ratio of 0 2 which is typical of the lunar highlands according to pike geophys res lett 1 291 294 1974 in impact and explosion cratering roddy et al eds pp 489 509 pergamon new york 1977 for mercury and the moon temperatures in shadows in polar craters are below 102 k so the sublimation rate of water ice calculated according to the model of watson et al j geophys res 66 3033 3015 1961 is less than 1 cm per byr the latitudinal extent of the cold zone on the moon is greater than that on mercury although temperatures at the poles of the two planets are similar the other application is to polar frosts on mars illuminated water frosts in radiative equilibrium grow rougher because the average temperature of a depression is greater than that of flat ground subliming co 2 frosts which are always at the same temperature grow rougher at low solar elevation angles because the heat flux absorbed by a depression is greater than that for a flat surface at high insolation rates high sun near perihelion the average heat flux to a depression is less than for a flat surface the latter evaporates faster which makes the average surface smoother and leads to a high average albedo this behavior helps explain the fact that the south co 2 cap which receives its greatest insolation near perihelion has a higher effective albedo and therefore can survive the summer whereas the north co 2 cap has a lower effective albedo and disappears each year around summer solstice

middle and late holocene paleotemperatures reconstructed from oxygen isotopes and gdgts of sediments from lake pupuke new zealand abstract quantitative holocene temperature reconstructions for southern hemisphere terrestrial environments are still restricted to few records and multi proxy methods are rarely applied to the same system here we test the applicability and comparability of temperature reconstructions inferred from different methodological approaches we combined sedimentary cellulose and diatom oxygen isotope data from lake pupuke north island new zealand to derive a record of lake water temperatures this record is complemented with mean annual air temperatures derived from the branched gdgt index mbt measured on the same sedimentary record the datasets of both reconstructions show little temperature variation for the period 1320 7110 cal bp the exceptions are a warmer period culminating between 1700 and 1600 cal bp reflected in both proxies and centennial scale intervals with cooler water temperatures at 3380 and 2750 cal bp recorded in the oxygen isotope based temperature reconstruction but not in the mbt inferred air temperature estimates we suggest that variations in lake circulation are the likely reason for deviations between temperature reconstructed from different proxies

the clementine mission to the moon scientific overview in the course of 71 days in lunar orbit from 19 february to 3 may 1994 the clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths these data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side in addition laser ranging measurements provided the first view of the global topographic figure of the moon the topography of many ancient impact basins has been measured and a global map of the thickness of the lunar crust has been derived from the topography and gravity

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

environmental controls on branched tetraether lipid distributions in tropical east african lake sediments abstract quantifying past continental temperature changes is an important aspect of paleoclimate research as it allows us to constrain the amplitude of natural variability test predictive climate models and provide a proper context for changes that may arise in response to anthropogenically induced climate change the recently developed biomarker based methylation index of branched tetraethers cyclization ratio of branched tetraethers mbt cbt proxy shows potential as a new method for continental temperature reconstruction but thus far it has only been applied successfully in ocean margin sediments to assess whether this proxy is also applicable to the sedimentary record in tropical lacustrine systems we investigated the distribution of branched glycerol dialkyl glycerol tetraethers gdgts in recently deposited sediments from 46 lakes in tropical east africa these lakes span a substantial range in surface elevation 770 4500 m above sea level and thus also a wide gradient of mean annual temperature we find that saline lakes excepted branched gdgts are universally abundant in the lakes investigated and can be used to predict mean annual air temperature maat with a high degree of accuracy however the existing global mbt cbt calibration for maat based on soils predicts inaccurate temperatures when applied to our african lake dataset this observation together with the fact that surface water ph and to lesser extent lake depth appear to influence the distribution of branched gdgts among sites leads us to conclude that in situ production of branched gdgts in lakes is likely the robust relationship between branched gdgt distribution and the temperature and ph of african freshwater lakes makes these compounds suitable for paleoenvironmental reconstruction however we urge caution in using branched gdgts in lake sediments to infer past temperatures unless their exact origin can be determined

the global albedo of the moon at 1064 nm from lola the lunar orbiter laser altimeter lola measures the backscattered energy of the returning altimetric laser pulse at its wavelength of 1064 nm and these data are used to map the reflectivity of the moon at zero phase angle with a photometrically uniform data set global maps have been produced at 4 pixels per degree about 8 km at the equator and 2 km resolution within 20 latitude of each pole the zero phase geometry is insensitive to lunar topography so these data enable characterization of subtle variations in lunar albedo even at high latitudes where such measurements are not possible with the sun as the illumination source the geometric albedo of the moon at 1064 nm was estimated from these data with absolute calibration derived from the kaguya multiband imager and extrapolated to visual wavelengths the lola estimates are within 2 of historical measurements of geometric albedo no consistent latitude dependent variations in reflectance are observed suggesting that solar wind does not dominate space weathering processes that modify lunar reflectance the average normal albedo of the moon is found to be much higher than that of mercury consistent with prior measurements but the normal albedo of the lunar maria is similar to that of mercury suggesting a similar abundance of space weathering products regions within permanent shadow in the polar regions are found to be more reflective than polar surfaces that are sometimes illuminated limiting analysis to data with slopes less than 10 eliminates variations in reflectance due to mass wasting and shows a similar increased reflectivity within permanent polar shadow steep slopes within permanent shadow are also more reflective than similar slopes that experience at least some illumination water frost and a reduction in effectiveness of space weathering are offered as possible explanations for the increased reflectivity of permanent shadow porosity is largely ruled out as the sole explanation the south polar crater shackleton is found to be among the most reflective craters in its size range globally but is not the most reflective so mass wasting cannot be ruled out as a cause for the crater s anomalous reflectance models of the abundance of ice needed to account for the reflectance anomaly range from 3 to 14 by weight or area depending on assumptions regarding the effects of porosity on reflectance and whether ice is present as patches or is well mixed in the regolith if differences in nanophase iron abundances are responsible for the anomaly the permanently shadowed regions have between 50 and 80 the abundance of nanophase iron in mature lunar soil

fluxes and distribution of tetraether lipids in an equatorial african lake constraints on the application of the tex86 palaeothermometer and bit index in lacustrine settings abstract the distribution of isoprenoid and branched glycerol dialkyl glycerol tetraether gdgt lipids was studied in material from various sources in and around lake challa a crater lake on the southeastern slope of mt kilimanjaro tanzania to examine the provenance of gdgts in lake sediments and their potential application as palaeoenvironmental and palaeoclimatic proxies the study material included samples collected at monthly intervals in a sediment trap over one complete annual cycle particles suspended in the stratified water column profundal surface sediments and soils surrounding the lake the sediment trap time series revealed that crenarchaeol and related isoprenoid gdgts were predominantly produced in january and february following the locally prominent short rain season november december the tex 86 inferred temperature derived from sedimenting particles corresponded well with lake surface water temperature at this time of largest crenarchaeol flux molecular ecological analysis showed that group 1 1a and 1 1b crenarchaeota are the most likely source organisms of these gdgts gdgt 0 in the lake sediments does not only originate from lake surface dwelling crenarchaeota but seems predominantly derived from archaea residing in the deeper anoxic part of the water column the main flux of branched gdgts to the sediment was during the short rain season and is most probably derived from eroded catchment soils in surface run off however a contribution from in situ production of branched gdgts in the lake sediment or water or in groundwater cannot be fully excluded we conclude that palaeoclimatic reconstruction based on branched gdgt distributions in lake sediments should only be performed when the origin of those branched gdgts is well constrained

temperature variations since 1750 ce inferred from an alpine lake in the southeastern margin of the tibetan plateau abstract high altitude regions are thought to be very sensitive to global climate change especially under current global warming however due to the lack of paleoclimate archives such as ice core and tree rings above the modern tree line limited paleoclimate data have been extracted to extend instrumental data over the past few centuries which will help understand the interannual to decadal scale climate variability in high altitude regions here we present a high resolution 1 6 yr quantitative temperature record from a remote alpine lake at the southeastern margin of the tibetan plateau by applying a novel proxy based on branched glycerol dialkyl glycerol tetraethers brgdgts contrary to the often documented warming trend over the past few centuries but consistent with temperature record from the northern tibetan plateau our data show a gradual decreasing trend of 0 3 c in mean annual air temperature from 1750 to 1970 ce this result suggests a gradual cooling trend in some high altitude regions over this interval which could provide a new explanation for the observed decreasing asian summer monsoon in addition our data indicate an abruptly increased interannual to decadal scale temperature variations of 0 8 2 2 c after 1970 ce in terms of both magnitude and frequency indicating that the climate system in high altitude regions would become more unstable under current global warming

response of δd values of sedimentary n alkanes to variations in source water isotope signals and climate proxies at lake nam co tibetan plateau abstract compound specific d values of sedimentary n alkanes from nam co were compared with oxygen isotope values from three different ice cores of the tibetan plateau and other climate proxies including temperature and solar radiation this enabled estimation of the importance of source water and of environmental factors at the ecosystem scale on variations of the isotopic composition of sedimentary n alkanes the ice core records from dasuopu puruogangri and rongbuk glacier of the past 1000 years recording the source water isotopes show a continuous deuterium enrichment indicating a warming trend or decreased precipitation sedimentary n alkane d values also represent the same general tendency to enrichment in heavier isotopes however the correlation to the 18o values derived from the ice record is very weak the d values of n alkanes agree with known climatic events such as the little ice age and medieval warm period showing depleted and enriched d values respectively the d values of the n alkanes were best related to environmental drivers including temperature and solar radiation the results suggest that d values of sedimentary n alkanes mainly record evapotranspiration and relative humidity that strongly influence d values at the plant level while variability of the source signal is less important

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

mapping and characterization of non polar permanent shadows on the lunar surface abstract we present the first globally complete inventory of permanent shadows on the lunar surface that are detectable with the current global instrument datasets including discovery of regions with persistent shadows over geologic time periods as close to the equator as 58 of latitude these results were obtained through application of a ray tracing technique to the latest global topographic datasets from the lunar reconnaissance orbiter our analysis reveals that 13 361 km2 of surface in the northern hemisphere and 17 698 km2 in the southern hemisphere are permanently shadowed we present maps showing the locations of all the permanent shadows detectable using these datasets then turn our focus toward the permanent shadows farthest from the poles each permanent shadow on the equator side of 65 of latitude is shown in detail surface brightness temperature data derived from the diviner mid infrared radiometer on board the lunar reconnaissance orbiter have been analyzed for four of these locations and found to have mid day temperatures 75 120 k less than nearby comparison locations that experience direct daytime illumination in some cases the permanently shadowed locations have nighttime temperatures 10 25 k lower than surroundings the temperature results support our finding that these non polar craters are permanently shadowed the surface brightness temperature results also raise interesting questions about their ability to cold trap volatiles discovery of these non polar permanently shadowed regions increases possible locations of water resources and high priority exploration targets on the moon

image reconstruction techniques in neutron and gamma ray spectroscopy improving lunar prospector data we present improved resolution maps of the lunar prospector neutron spectrometer thermal epithermal and fast neutron data and gamma ray spectrometer th line fluxes via global application of pixon image reconstruction techniques with the use of mock data sets we show that the pixon image reconstruction method compares favorably with other methods that have been used in planetary neutron and gamma ray spectroscopy the improved thermal neutron maps are able to clearly distinguish variations in composition across the lunar surface including within the lunar basins of hertzsprung and schrodinger the improvement in resolution reveals a correlation between albedo and thermal neutron flux within the basins the consequent increase in dynamic range confirms that hertzsprung basin contains one of the most anorthositic parts of the lunar crust including nearly pure anorthite over a region tens of kilometers in diameter at orientale the reconstructed epithermal neutron data show broad overlap with circular polarization ratio but there remains a mismatch between measures of regolith maturity that sample the surface and those that probe the near subsurface which is consistent with a complex layering scenario

one moon many measurements 2 photometric corrections abstract observations of the lunar surface within the past 10 years have been made with various lunar remote sensing instruments the moon mineralogy mapper m 3 onboard the chandrayaan 1 mission the spectral profiler sp the multiband imager mi the terrain camera tc onboard the selene mission and the ground based usgs robotic lunar observatory rolo for some of them the lunar phase functions derived from these datasets which are used in the photometric modeling to correct for the various illumination conditions of the data are compared to assess their differences and similarity in order to improve interpretations of lunar surface spectra the phase functions are found to be similar across various phase angles except in the 0 20 range differences across the 0 20 range likely result from two different inputs in the photometric modeling of the m 3 and sp data 1 m 3 has larger emission angles due to the characteristics of the instrument and the attitude of the spacecraft and 2 m 3 viewing geometry was derived from the local topography whereas sp used a spherical moon no topography the combination of these two different inputs affects the phase function at small phase angles where shadows play a more substantial role with spatial resolution differences between m 3 and sp being another possible source for the differences sp data are found to be redder i e steeper slope with increasing wavelengths than mi m 3 and rolo finally the m 3 overall reflectance is also found to be lower than that the other instruments i e mi sp and rolo generally at least 10 darker than mi these differences can be observed at local scales in specific examples at hundreds of meters resolutions at regional and global scales the same differences are found which demonstrates the overall stability of the various datasets the observations from m 3 tc sp and mi are very stable and agree well however caution should be used when making interpretations based on the spectral slope of sp data or on the absolute reflectance of m 3 data

distributions of branched gdgts in soils and lake sediments from western uganda implications for a lacustrine paleothermometer bacterially produced branched glycerol dialkyl glycerol tetraethers gdgts are ubiquitous in soils and lake sediments and can potentially be used to reconstruct past temperatures in lakes however it is still unclear if these compounds are derived from eroded soils or if they are produced in situ to better understand environmental controls on the distributions of these compounds and the sources of branched gdgts to lake sediments we compare branched gdgt distributions and concentrations in lake sediments and catchment soils within a 3600 m altitudinal transect in western uganda reconstructed mean annual air temperature maat determined from the degree of methylation mbt and cyclisation cbt of branched gdgts in soils decreases with increasing altitude as is expected from the air temperature gradient in our transect however we observe significant offsets between observed and reconstructed temperatures in soils from wet high elevation soils but not in most dry low elevation soils branched gdgt distributions differ significantly between lake sediments and soils at all elevations with greater differences at low elevations than at high elevations these data support previous hypotheses that branched gdgts are produced in situ in lakes and suggest that the abundance of water in soil environments may play a role in controlling the distribution of branched gdgts while branched gdgts in lacustrine sediments can be used to reconstruct temporal temperature variations in lakes we urge caution in utilizing this proxy in lacustrine systems with high soil loadings especially if there is evidence of changing clastic fluxes through time

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

properties of the hermean regolith iv photometric parameters of mercury and the moon contrasted with hapke modelling a comparison of the photometric properties of mercury and the moon is performed based on their integral phase curves and disk resolved image data of mercury obtained with the swedish vacuum solar telescope proper absolute calibration of integral v band

ti content in huguangyan maar lake sediment as a proxy for monsoon induced vegetation density in the holocene the provenance of element ti in huguangyan maar lake hgy sediment has been under debate since yancheva et al 2007a proposed its eolian source from the chinese loessplateau clp and applied it as a proxy for asian wintermonsoon we performed a comprehensive study on ti carryingminerals and ti uxes in lake sediments wall rocks andloess from the clp here we show that the chemicalcompositions and morphological features of magnetite the most important ti carrier in hgy surface sediments are identical to those in wall rocks around the lake butsubstantially different from those in clp loess samples ourcalculated modern eolian ti ux from the clp is negligiblecompared to the average total ti ux to hgy and ti uxfrom catchment erosion can provide enough ti indicating tiin hgy sediment are predominantly from wall rock erosion inverse correlation between total organic carbon toc vegetation density and ti ca ratio terrestrial input in theholocene suggests monsoon induced vegetation densitypredominates over runoff in controlling ti input to hgy s ratio represents toc directly mediated reductive diagenesisof iron oxides magnetite preservation rather than anoxic oxic condition at the bottom water induced by wintermonsoon our record shows a decreased vegetation density increased ti input and weakened reductive diagenesisthrough the holocene driven by a weakened summermonsoon

records of the 8200calbp cold event reflected in the composition of subfossil cladocera in the sediments of three lakes in poland abstract the 8200 cal bp cold event was documented by analyzing cladoceran subfossil remains in sediments of three polish lakes to date this cold event has primarily been identified in areas located at higher latitudes of the northern hemisphere it has mainly been confirmed by results of oxygen and carbon stable isotope analyses this survey represents an attempt to find traces of the 8200 cal bp cold event in lake sediments based on changes in the species composition and frequency of cladoceran individuals both archival accurately dated sediments lake ostrowite lake go ci z and recently cored samples lake charzykowskie were used the analysis of subfossil cladocerans was performed at a high resolution this allowed derivation of detailed conclusions regarding early holocene changes within lakes and therefore conclusions on short term climate changes in lakes ostrowite charzykowskie and go ci z changes in the zooplankton cladocera composition occurred at the same time as the cold event certain species disappeared completely and the percentage share of the majority of zooplankters decreased significantly certain species camptocercus lilljeborgi alonopsis elongata that are typical of lakes in northern areas appeared during the cold event although not in large numbers

correlations between microbial tetraether lipids and environmental variables in chinese soils optimizing the paleo reconstructions in semi arid and arid regions the bacterial membrane lipid based continental paleothermometer the mbt cbt or mbt cbt proxy methylation index of branched tetraethers cyclization of branched tetraethers results in a large temperature deviation when applied in semiarid and arid regions here we propose new calibration models based on the investigation of 100 surface soils across a large climatic gradient with a particular focus on semiarid and arid regions of china and apply them to a loess paleosol sequence as reported elsewhere mbt values exhibit a much higher correlation with maat than with summer temperature suggesting a minimal seasonality bias however mbt is apparently insensitive to temperature 20 degrees c additional complexities are apparent in alkaline and arid soils which are characterized by different relationships to climatic parameters than those in the complete chinese or global dataset for example mbt and cbt indices exhibit a negative correlation in alkaline and arid soils in contrast to their positive correlation in acid soils moreover the cyclization ratio of bgdgts cbt previously defined as a proxy for soil ph is apparently primarily controlled by maat in these alkaline soils thus we propose 1 a local chinese calibration of the mbt cbt proxy and 2 an alternative temperature proxy for use in semiarid and arid regions based on the fractional abundances of bgdgts the latter has a markedly higher determination factor and lower root mean square error in alkaline soils than the chinese local calibration and is suggested to be preferred for paleotemperature reconstruction in chinese loess paleosol sequences these new bgdgt proxies have been applied to the weinan holocene paleosol section of the chinese loess plateau clp the fractional abundance calibration when applied in the weinan holocene paleosol produces a total holocene temperature variation of 5 2 degrees c and a temperature for the topmost sample that is consistent with the modern temperature previously we showed that the ratio of archaeal isoprenoid gdgts to bgdgts r i b increases at map 0 5 in the clp suggest the presence of enhanced aridity in the late holocene in north china in combination the high r i b ratios 0 5 and the associated low mbt values 0 4 reveal the co occurrence of dry and cold events especially in the latest holocene in the loess paleosol sequences in clp and probably also in cold and arid regions outside of clp c 2013 elsevier ltd all rights reserved

global regolith thermophysical properties of the moon from the diviner lunar radiometer experiment we used infrared data from the lunar reconnaissance orbiter lro diviner lunar radiometer experiment to globally map thermophysical properties of the moon s regolith fines layer thermal conductivity varies from 7 4 10 4 w m 1 k 1 at the surface to 3 4 10 3 w m 1 k 1 at depths of 1 m given density values of 1100 kg m 3 at the surface to 1800 kg m 3 at 1 m depth on average the scale height of these profiles is 7 cm corresponding to a thermal inertia of 55 2 j m 2 k 1 s 1 2 at 273 k relevant to the diurnally active near surface layer 4 7 cm the temperature dependence of thermal conductivity and heat capacity leads to a 2x diurnal variation in thermal inertia at the equator on global scales the regolith fines are remarkably uniform implying rapid homogenization by impact gardening of this layer on timescales 100 j m 2 k 1 s 1 2 in the interiors and ejecta of copernican aged impact craters and lower thermal inertia 50 j m 2 k 1 s 1 2 within the lunar cold spots identified by bandfield et al 2014 observed trends in ejecta thermal inertia provide a potential tool for age dating craters of previously unknown age complementary to the approach suggested by ghent et al 2014 several anomalous regions are identified in the global 128 pixels per degree maps presented here including a high thermal inertia deposit near the antipode of tycho crater

extended megadroughts in the southwestern united states during pleistocene interglacials the potential for increased drought frequency and severity linked to anthropogenic climate change in the semi arid regions of the southwestern united states us is a serious concern1 multi year droughts during the instrumental period2 and decadal length droughts of the past two millennia1 3 were shorter and climatically different from the future permanent dust bowl like megadrought conditions lasting decades to a century that are predicted as a consequence of warming4 so far it has been unclear whether or not such megadroughts occurred in the southwestern us and if so with what regularity and intensity here we show that periods of aridity lasting centuries to millennia occurred in the southwestern us during mid pleistocene interglacials using molecular palaeotemperature proxies5 to reconstruct the mean annual temperature mat in mid pleistocene lacustrine sediment from the valles caldera new mexico we found that the driest conditions occurred during the warmest phases of interglacials when the mat was comparable to or higher than the modern mat a collapse of drought tolerant c4 plant communities during these warm dry intervals indicates a significant reduction in summer precipitation possibly in response to a poleward migration of the subtropical dry zone three mat cycles 2 c in amplitude occurred within marine isotope stage mis 11 and seem to correspond to the muted precessional cycles within this interglacial in comparison with mis 11 mis 13 experienced higher precessional cycle amplitudes larger variations in mat 4 6 c and a longer period of extended warmth suggesting that local insolation variations were important to interglacial climatic variability in the southwestern us comparison of the early mis 11 climate record with the holocene record shows many similarities and implies that in the absence of anthropogenic forcing the region should be entering a cooler and wetter phase

near surface ice on mercury and the moon a topographic thermal model abstract a thermal model that can be easily adapted to craters of arbitrary shape is developed and applied to high latitude impact craters on mercury and the moon chao meng fu crater at 87 5 l on mercury an unnamed bowl shaped crater at 86 7 l on mercury and peary crater at 88 6 l on the moon for an assumed input topography and grid of surface elements the model computes for each element the irradiation from direct insolation and reflected and emitted radiation from other elements taking into account shadowing by the walls of the crater partial obscuration of the solar disk near the poles and the diurnal orbital and seasonal cycles temperatures are computed over the surface grid as functions of depth and time from the surface to a specified depth and over the pertinent astronomical cycles including the effects of direct and indirect surface irradiation infrared radiation heat conduction and interior heating vapor fluxes and ice recession times are computed as functions of ice depth over the surface grid temperatures profiles vapor fluxes and ice recession times were computed for flat surfaces not associated with craters near the poles of mercury and the moon it was found that water ice could have existed throughout geologic time within the maximum radar detection depth of recent observation of mercury j k harmon and m a slade 1992 science 258 640 643 poleward of 87 88 l on mercury and poleward of 73 l on the moon for chao meng fu crater it was found that 40 of the crater floor is permanently shadowed from direct solar insolation while the remainder of the crater floor is periodically illuminated by a partially obscured sun temperatures at the upper levels of the south wall can slightly exceed 550 k surface temperatures in the permanently shadowed region of the crater floor are under 130 k which could have allowed water ice to exist throughout geologic time within the radar detection depth of recent observation of mercury for the small bowl shaped crater on mercury it was found that most of the crater is permanently shadowed from direct solar radiation except for a narrow semicircular band bordering the north rim however temperatures in the permanently shadowed region periodically reach a maximum near 315 k due to efficient heating of the small crater by thermal emission and reflection from the small sunlit region which periodically reaches temperatures exceeding 630 k water ice could not have existed throughout geologic time anywhere in this crater within the radar detection depth for peary crater on the moon the entire crater floor is permanently shadowed from direct solar insolation with maximum temperatures under 120 k the upper level of the north wall periodically reaches a maximum temperature near 310 k the low temperatures on the crater floor would have allowed water ice to exist near the surface throughout geologic time provided that the moon s obliquity was always as low as it is at present

space weathering from mercury to the asteroid belt the variety of evidence bearing on the nature of space weathering is reviewed the effects of space weathering include spectral darkening reddening and subdued absorption bands and the distinctive magnetic electron spin resonance caused by single domain metallic iron particles ever since the apollo missions two paradigms have dominated the thinking of the planetary science community concerning space weathering 1 the optical effects are caused by impact vitrified glass in agglutinates and 2 the submicroscopic metallic iron results from the reduction of ferrous iron by the impact melting of minerals whose surfaces have been saturated with hydrogen from the solar wind however studies carried out since the apollo program showed that both of these paradigms are invalid a hypothesis first suggested by the author and his colleagues 26 years ago but not generally accepted at that time now appears to be essentially correct both the optical and magnetic effects are caused by metallic iron particles smaller than the wavelength in ubiquitous vapor deposited coatings on soil particle surfaces and inside agglutinates the vapor is generated by both solar wind sputtering and micrometeorite impact vaporization and injected preferentially downward into the porous regolith the iron is reduced by a physical process the selective loss of oxygen that occurs during deposition of the vapor and does not require heating melting or a reducing environment a mathematical theory that describes the optical effects of the submicroscopic iron quantitatively is derived and applied to the regoliths of the moon mercury and an s asteroid

decadal multi decadal temperature discrepancies along the eastern margin of the tibetan plateau abstract knowledge of the synchronicity and discrepancy of temperature variations along the eastern margin of the tibetan plateau etp is critical in understanding the driving forcing of regional temperature variations in this study we established 15 n timeseries in organic matter and 13 c timeseries in ostracod shells from sediments of lake lugu and attributed their variations to decadal multi decadal temperature variations we compared temperature variations along the etp transect during the past four centuries based on our presently developed and previously developed temperature proxy indices as well as temperature variations reconstructed by other researchers we found that 1 over the north etp area n etp the decadal multi decadal variations in temperature correlate well with each other 2 over the south etp area s etp temperature variations correlate not so well with each other while those at south to west portion of the tibetan plateau are rather local 3 the decadal variations in temperature are generally synchronous with those in precipitation over the n etp area and they are broadly anti phase out of phase with the corresponding ones over the s etp area 4 the long term temperature and precipitation trends are coupling over the n etp but decoupling over the s etp we speculate that because the n etp is located at the frontier of the asian summer monsoon asm region temperature variations there are not as strongly influenced by the asm they are most likely dominated by changes in solar activities and show general similarity to the average of the northern hemisphere over the s etp area decadal temperature variations are obviously influenced by precipitation because the decadal multi decadal precipitation variations are anti phase and or out of phase between the n etp and s etp the decadal multi decadal temperature variations between these two regions are also anti phase and or out of phase

distribution of bacterial and archaeal ether lipids in soils and surface sediments of tibetan lakes implications for gdgt based proxies in saline high mountain lakes bacterial and archaeal lipids such as glycerol dialkyl glycerol tetraethers gdgts and dialkyl glycerol diethers are increasingly used as proxies for specific environmental parameters such as air temperature and soil ph in lacustrine environments little is known however about the distribution and applicability of bacterial and archaeal lipids on the tibetan plateau we investigated nine different watersheds across the plateau by way of sediments from lakes and rivers as well as the surrounding soils our transect study included a salinity gradient and focused on saline lakes which are rarely examined we analyzed archaeal isoprenoid i and bacterial branched b gdgts as well as archaeol to trace their sources and environmental factors influencing their distributions we could show that igdgts were produced in situ and bgdgts were primarily soil derived although we could not exclude in situ production of bgdgts in the lakes the most important environmental variables correlating with gdgt distributions were temperature and salinity bacterial gdgt distributions correlated mainly with salinity while archaeal lipid distributions correlated with temperature based on the correlation of methylation mbt and cyclisation cbt indices of bgdgts with ph and mean annual air temperature maat we established local calibrations for the tibetan lakes tex86 could also be applied to reconstruct temperature which was strongly biased towards measured summer lake water temperature indicating enhanced production of igdgts in the summer months existing proxies show therefore potential for palaeoclimate reconstruction on the tibetan plateau if local calibrations are applied

decreasing monsoon precipitation in southwest china during the last 240 years associated with the warming of tropical ocean based on an absolutely dated stalagmite 18o record from yunnan province china we reconstructed monsoon precipitation variations in southwest china since 1760 ad with a resolution of about 2 years combining the speleothem 18o and observed rainfall records we find an overall decreasing trend in monsoon precipitation in this region and suggest that the recent drought in 2009 2012 ad has been the driest since 1760 ad our speleothem record is consistent with the monsoon precipitation records reconstructed from tree rings in the nepal himalaya and southeastern tibetan plateau however it is anti correlated with a speleothem record from central india which confirms the observed anti phase variations of indian monsoon precipitation with moistures from the bay of bengal and arabian sea on multi decadal to centennial timescales during historical time the long term warming of tropical ocean may have caused the decrease of the land sea thermal gradient and the amount of moisture transported from the bay of bengal which may reduce precipitations in southwest china during the last 240 years on decadal scale el nino like conditions of tropical pacific sea surface temperature may cause drought in this region climate model simulations suggest el nino like conditions exist in tropical pacific under global warming scenarios as a result it is crucial to have adaptive strategies to overcome future declines in precipitation and or drought events in southwest china

latitudinal variation in spectral properties of the lunar maria and implications for space weathering abstract space weathering alters the optical properties of exposed surfaces over time complicating the interpretation of spectroscopic observations of airless bodies like asteroids mercury and the moon solar wind and micrometeoroids are likely the dominant agents of space weathering but their relative contributions are not yet well understood based primarily on clementine mosaics we report a previously unrecognized systematic latitudinal variation in the near infrared spectral properties of the lunar maria and show that the characteristics of this latitudinal trend match those observed at lunar swirls where magnetic fields alter local solar wind flux without affecting the flux of micrometeoroids we show that the observed latitudinal color variations are not artifacts of phase angle effects and cannot be accounted for by compositional variation alone we propose that reduced solar wind flux which should occur both at swirls and toward higher latitudes is the common mechanism behind these color variations this model helps us quantify the distinct effects of solar wind and micrometeoroid weathering and could aid in interpreting the spectra of airless bodies throughout the solar system

late cenozoic evolution of the eastern margin of the tibetan plateau inferences from 40ar 39ar and u th he thermochronology high topography in central asia is perhaps the most fundamental expression of the cenozoic indo asian collision yet an understanding of the timing and rates of development of the tibetan plateau remains elusive here we investigate the cenozoic thermal histories of rocks along the eastern margin of the plateau adjacent to the sichuan basin in an effort to determine when the steep topographic escarpment that characterizes this margin developed temperature time paths inferred from 40 ar 39 ar thermochronology of biotite multiple diffusion domain modeling of alkali feldspar 40 ar release spectra and u th he thermochronology of zircon and apatite imply that rocks at the present day topographic front of the plateau underwent slow cooling 30 50 c m y coincident with exhumation from inferred depths of 8 10 km at denudation rates of 1 2 mm yr samples from the interior of the plateau continued to cool relatively slowly during the same time period 3 c m y suggesting limited exhumation 1 2 km however these samples record a slight increase in cooling rate from 1 to 3 c m y at some time during the middle tertiary the tectonic significance of this change remains uncertain regardless late cenozoic denudation in this region appears to have been markedly heterogeneous with the highest rates of exhumation focused at the topographic front of the plateau margin we infer that the onset of rapid cooling at the plateau margin reflects the erosional response to the development of regionally significant topographic gradients between the plateau and the stable sichuan basin and thus marks the onset of deformation related to the development of the tibetan plateau in this region the present margin of the plateau adjacent to and north of the sichuan basin is apparently no older than the late miocene or early pliocene 5 12 ma

a review of molecular organic proxies for examining modern and ancient lacustrine environments molecular organic geochemical proxies are increasingly being utilized to reconstruct past environmental conditions as new tools continue to be discovered and developed to date organic geochemical proxies have been developed mainly for use in marine systems and are widely used in paleoceanography in contrast organic proxies have been less commonly used on lacustrine sedimentary records one reason for this is that the wide range in the physical and chemical properties of lakes complicates application of some organic geochemical proxies in lacustrine settings furthermore in comparison to marine studies presently only a small number of studies have conducted or are currently conducting fundamental research aimed at developing organic geochemical proxies for use in lacustrine settings despite this an increasing number of paleo limnological studies are currently applying organic geochemical techniques to examine present and past environmental conditions in this manuscript we review the use of a number of commonly utilized organic geochemical and isotopic proxies and discuss their potential for environmental reconstruction in quaternary lacustrine deposits

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

tree ring based annual precipitation reconstruction since ad 1480 in south central tibet abstract a tree ring width chronology of 528 years was developed from tibetan junipers juniperus tibetica kom from south central tibet in western china the correlation and response analysis displays high correlation between tree ring width and observed mean annual precipitation series during the period 1960 2008 based on a linear regression model an annual prior july to current june precipitation series from ad 1480 to 2008 was reconstructed this is the first well calibrated precipitation reconstruction for south central tibet the results show that periods of wet years occurred in ad 1480 1535 1626 1639 1651 1671 1704 1798 1845 1872 1888 1907 1917 1940 and after 1994 whereas relatively dry periods prevailed during ad 1536 1625 1640 1650 1672 1703 1799 1844 1873 1887 1908 1916 and 1914 1993 the dry intervals in ad 1500s 1550s 1710s 1800s 1850s 1870s and 1900s 1920s and the wet intervals in ad 1550s 1630s 1680s 1720s 1800s 1850s and 1960s 1990s occurred contemporaneously in northeastern tibet reflecting regional climatic variations

distribution of glycerol dialkyl glycerol tetraether gdgt lipids in a hypersaline lake system isoprenoid glycerol dialkyl glycerol tetraethers isogdgts of archaeal origin and branched br gdgts of bacterial origin occur in a diverse range of lacustrine sedimentary environments they have attracted attention as potential temperature proxies providing high resolution palaeo environmental reconstruction from continental interiors for this study the distribution of gdgts in and application of gdgt based proxies to surface samples from chaka salt lake china as well as soils and in flow river sediments were investigated to assess whether gdgt based proxies were applicable to this hypersaline lake system we show that iso and brgdgts were present in all sediments and soils from the chaka salt lake system gdgt 0 and crenarchaeol were generally the two most abundant isogdgts suggesting thaumarchaeota as a major biological source of isogdgts the low ratio of crenarchaeol crenarchaeol regioisomer suggests that thaumarchaeota of the lake sediments is likely thaumarchaeota group i 1b derived from the surrounding alkaline soils arguing against the use of the tex86 proxy in this system because alkaline soils generally have high isogdgt concentrations it is likely that a large allochthonous input of isogdgts would be a pervasive challenge to palaeoclimate applications in such settings on the other hand the brgdgt distributions in the lake and river sediments differed markedly from those in the surrounding soils suggesting that instead of deriving from the surrounding soils at least part of the brgdgts is synthesized in situ or delivered from more distal upland soils taken together our results indicate that the mixed sources of gdgts in chaka salt lake complicate the application of gdgt based proxies and it will be challenging to use such proxies in this system

calibration and application of the branched gdgt temperature proxy on east african lake sediments branched glycerol dialkyl glycerol tetraethers brgdgts are a novel proxy for mean annual air temperature maat and have the potential to be broadly applicable to climate reconstruction using lacustrine sediments several calibrations have been put forth relating brgdgt distributions to maat using a variety of linear regressions including the methylation mbt and cyclization cbt indices of brgdgts the relative abundances of the major non cyclized brgdgts mbrgdgts and best subsets regression bsr of the fractional abundances of the nine most common brgdgts however these calibrations have rarely been applied to lake sediment cores to reconstruct temperatures and test the applicability of this proxy as a paleothermometer we present an expanded east african lakes surface sediment brgdgt dataset based upon 111 lakes and examine three methods of calibrating brgdgts to maat these methods include recalculations of the east african lake mbt cbt calibration and mbrgdgts calibrations as well as a new stepwise forward selection sfs calibration that uses the four combined brgdgts that explain the most variance in temperature in our calibration set we apply these new calibrations as well as five previously published lacustrine brgdgt calibrations to the brgdgt distributions of our surface sediment dataset and a 48 kyr sediment core from sacred lake mt kenya producing the first brgdgt temperature reconstruction available from a small tropical lake we compare the reconstructed temperatures to previously published paleotemperature records from east africa to help us assess the performance of the brgdgt calibrations we find that the sfs calibration has a consistently low root mean squared error of prediction rmsep over the entire range of maat while the mbt cbt and mbrgdgt calibrations have relatively large rmseps particularly between lakes with similar temperatures but variable ph this suggests that these techniques do not properly deconvolve the temperature and ph signals recorded in the distributions of the brgdgts we further find that only the sfs calibration produces a credible reconstructed temperature history from sacred lake when compared to other last glacial maximum paleotemperature estimates from east africa thus we advocate for the use of the sfs calibration when reconstructing paleotemperatures from brgdgts in east africa

distributions of branched gdgts in a tropical lake system implications for lacustrine application of the mbt cbt paleoproxy branched glycerol dialkyl glycerol tetraether gdgt lipids are abundant and ubiquitous in lake sediments potentially allowing for a paleolimnological application of the so called mbt cbt proxy methylation index of branched tetraethers cyclization ratio of branched tetraethers to investigate the origin and characteristics of these compounds in lacustrine environments we examined the distributions of gdgts in soils river sediments and lake sediments from lake towuti on the island of sulawesi indonesia we found significant differences in the degree of methylation and cyclization expressed by way of the mbt and cbt indices between the soil samples and the aquatic samples suggesting that there may be in situ production of gdgts in the aquatic environment based on these findings we urge caution in the application of the mbt cbt paleoproxy to lake sediments and encourage more rigorous study of these compounds in freshwater environments

the nature and origin of rims on lunar soil grains abstract space weathering processes that operate in the lunar regolith modify the surfaces of lunar soil grains transmission electron microscope analysis of the lunar soil grains from the fine size fraction of several lunar soils show that most grains are surrounded by thin 60 200 nm thick rims the microstructure and chemical compositions of the rims can be used to classify rims into four broad categories amorphous inclusion rich multiple and vesicular amorphous rims are noncrystalline generally lack crystalline inclusions show evidence for preferential sputtering of cations and are produced largely by solar wind irradiation damage inclusion rich rims contain abundant nanometer sized grains of fe metal as randomly dispersed inclusions or as distinct layers embedded in an amorphous silica rich matrix inclusion rich rims are compositionally distinct from their host grains and typically contain accumulations of elements that are not indigenous to the host inclusion rich rims are formed largely by the deposition of impact generated vapors with a contribution from the deposition of sputtered ions a continuum in the chemical and microstructural properties exists between typical amorphous rims and typical inclusion rich rims multiple rims consist of a distinct radiation damaged layer up to 50 nm thick that is overlain by vapor deposited material of comparable thickness vesicular rims are compositionally similar to their hosts and are characterized by an abundance of small the formation of rims on lunar soils is complex and involves several processes whose effects may be superimposed from this study it is shown that one process does not dominate and that the relative importance of vapor deposition is comparable to radiation damage in the formation of rims on lunar silicate grains the presence of rims on lunar soil grains particularly those with nanometer sized fe metal inclusions may have a major influence on the optical and magnetic properties of lunar soils

geochemistry of the lunar highlands as revealed by measurements of thermal neutrons thermal neutron emissions from the lunar surface provide a direct measure of bulk elemental composition that can be used to constrain the chemical properties of near surface depth 85 are generally associated with large impact basins and are colocated with clusters of nearly pure plagioclase identified with spectral reflectance data

two hundred fifty years of reconstructed and modeled tropical temperatures 1 recent large scale palaeoclimate reconstructions of past temperature have been essentially biased to the extratropics owing to a paucity of proxy data in tropical regions herein we describe the first coral based reconstruction of sea surface temperatures ssts for the whole of the tropics 30 n 30 s it was developed from 14 disparate coral records located in the indian and pacific oceans over the most replicated period the reconstruction explains 57 of the tropical sst variance however the strength of this signal weakens markedly as the number of coral records decreases the reconstruction is robust between 1850 and 1993 but some fidelity is indicated back as far as the mid 18th century these results suggest that ambiguities in the low frequency domain of 18o measurements can be partially overcome by pooling together multiple time series from different locations around the tropics agreement with simulations from two general circulation models indicates that the late 20th century is likely the warmest period in the tropics for the last 250 years and that this recent warming can only be explained by anthropogenic forcing the high frequency variability is dominated by the el nino southern oscillation the reconstruction owing to the small number of coral records is unfortunately restricted both in time and space therefore we hope that this study will spur the palaeoclimate community to develop new and longer proxy series to improve the current meager data base of temperature sensitive series in the tropics

bright and dark polar deposits on mercury evidence for surface volatiles measurements of surface reflectance of permanently shadowed areas near mercury s north pole reveal regions of anomalously dark and bright deposits at 1064 nanometer wavelength these reflectance anomalies are concentrated on poleward facing slopes and are spatially collocated with areas of high radar backscatter postulated to be the result of near surface water ice correlation of observed reflectance with modeled temperatures indicates that the optically bright regions are consistent with surface water ice whereas dark regions are consistent with a surface layer of complex organic material that likely overlies buried ice and provides thermal insulation impacts of comets or volatile rich asteroids could have provided both dark and bright deposits

initial observations from the lunar orbiter laser altimeter lola as of june 19 2010 the lunar orbiter laser altimeter an instrument on the lunar reconnaissance orbiter has collected over 2 0 10 9 measurements of elevation that collectively represent the highest resolution global model of lunar topography yet produced these altimetric observations have been used to improve the lunar geodetic grid to 10 m radial and 100 m spatial accuracy with respect to the moon s center of mass lola has also provided the highest resolution global maps yet produced of slopes roughness and the 1064 nm reflectance of the lunar surface regional topography of the lunar polar regions allows precise characterization of present and past illumination conditions lola s initial global data sets as well as the first high resolution digital elevation models dems of polar topography are described herein

asymmetric space weathering on lunar crater walls using new topography corrected spectral data from the selene spacecraft here we report a new lunar crater property produced by space weathering we find the optical properties of north south east and west walls vary systematically across the moon pole facing walls are brighter and less red i e less mature than their equator facing counterparts as latitude increases which we explain by reduced solar wind flux in pole facing slopes on the nearside we find that east west differences in crater wall brightness and redness vary with longitude which we explain by solar wind shielding as the moon passes through the earth s magnetosphere because micrometeoroids are largely unaffected by magnetosphere passage the longitudinal effect is used to discriminate between micrometeoroid and solar wind effects thus for the first time we quantify how surface optical properties vary with solar wind flux

near surface temperatures on mercury and the moon and the stability of polar ice deposits abstract in order to assess the thermal stability of polar ice deposits we present model calculated temperatures of flat surfaces and surfaces within bowl shaped and flat floored polar impact craters on mercury and the moon our model includes appropriate insolation cycles realistic crater shapes multiple scattering of sunlight and infrared radiation and depth and temperature dependent regolith thermophysical properties unshaded water ice deposits on the surface of either body are rapidly lost to thermal sublimation a subsurface water ice deposit is stable within 2 latitude of the moon s poles meter thick water ice deposits require billions of years to sublime if located in the permanently shaded portions of flat floored craters within 10 latitude of the poles of mercury and 13 latitude of the poles of the moon results for craters associated with radar features on mercury are consistent with the presence of stable water ice deposits if a thin regolith layer thermally insulates deposits at lower latitudes and within smaller craters a regolith cover would also reduce losses from diffusion ion sputtering impact vaporization and h ly and is implied independently by the radar observations permanently shaded areas near the moon s poles are generally colder than those near mercury s poles but the moon s obliquity history its orbit through earth s magnetospheric tail and its radar opaque regolith may limit the volume and radar detectability of ice deposits there

radiostratigraphy and age structure of the greenland ice sheet 2015 the authors several decades of ice penetrating radar surveys of the greenland and antarctic ice sheets have observed numerous widespread internal reflections analysis of this radiostratigraphy has produced valuable insights into ice sheet dynamics and motivates additional mapping of these reflections here we present a comprehensive deep radiostratigraphy of the greenland ice sheet from airborne deep ice penetrating radar data collected over greenland by the university of kansas between 1993 and 2013 to map this radiostratigraphy efficiently we developed new techniques for predicting reflection slope from the phase recorded by coherent radars when integrated along track these slope fields predict the radiostratigraphy and simplify semiautomatic reflection tracing core intersecting reflections were dated using synchronized depth age relationships for six deep ice cores additional reflections were dated by matching reflections between transects and by extending reflection inferred depth age relationships using the local effective vertical strain rate the oldest reflections dating to the eemian period are found mostly in the northern part of the ice sheet within the onset regions of several fast flowing outlet glaciers and ice streams reflections typically do not conform to the bed topography disrupted radiostratigraphy is also observed in a region north of the northeast greenland ice stream that is not presently flowing rapidly dated reflections are used to generate a gridded age volume for most of the ice sheet and also to determine the depths of key climate transitions that were not observed directly this radiostratigraphy provides a new constraint on the dynamics and history of the greenland ice sheet

improved calibration of reflectance data from the lro lunar orbiter laser altimeter lola and implications for space weathering abstract the lunar orbiter laser altimeter lola experiment on lunar reconnaissance orbiter lro is a laser altimeter that also measures the strength of the return pulse from the lunar surface these data have been used to estimate the reflectance of the lunar surface including regions lacking direct solar illumination a new calibration of these data is presented that features lower uncertainties overall and more consistent results in the polar regions we use these data along with newly available maps of the distribution of lunar maria also derived from lro instrument data to investigate a newly discovered dependence of the albedo of the lunar maria on latitude hemingway et al 2015 we confirm that there is an increase in albedo with latitude in the lunar maria and confirm that this variation is not an artifact arising from the distribution of compositions within the lunar maria using data from the lunar prospector neutron spectrometer radiative transfer modeling of the albedo dependence within the lunar maria is consistent with the very weak to absent dependence of albedo on latitude in the lunar highlands the lower abundance of the iron source for space weathering products in the lunar highlands weakens the latitude dependence to the extent that it is only weakly detectable in current data in addition photometric models and normalization may take into account the fact that the lunar albedo is latitude dependent but this dependence can cause errors in normalized reflectance of at most 2 for the majority of near nadir geometries we also investigate whether the latitude dependent albedo may have obscured detection of small mare deposits at high latitudes we find that small regions at high latitudes with low roughness similar to the lunar maria are not mare deposits that may have been misclassified owing to high albedos imposed by the latitude dependence finally we suggest that the only modest correlations among space weathering indicators defined for the lunar samples may be due to mixing of soils from distinct latitudes

evidence for surface water ice in the lunar polar regions using reflectance measurements from the lunar orbiter laser altimeter and temperature measurements from the diviner lunar radiometer experiment abstract we find that the reflectance of the lunar surface within 5 of latitude of the south pole increases rapidly with decreasing temperature near 110 k behavior consistent with the presence of surface water ice the north polar region does not show this behavior nor do south polar surfaces at latitudes more than 5 from the pole this south pole reflectance anomaly persists when analysis is limited to surfaces with slopes less than 10 to eliminate false detection due to the brightening effect of mass wasting and also when the very bright south polar crater shackleton is excluded from the analysis we also find that south polar regions of permanent shadow that have been reported to be generally brighter at 1064 nm do not show anomalous reflectance when their annual maximum surface temperatures are too high to preserve water ice this distinction is not observed at the north pole the reflectance excursion on surfaces with maximum temperatures below 110 k is superimposed on a general trend of increasing reflectance with decreasing maximum temperature that is present throughout the polar regions in the north and south we attribute this trend to a temperature or illumination dependent space weathering effect e g hemingway et al 2015 we also find a sudden increase in reflectance with decreasing temperature superimposed on the general trend at 200 k and possibly at 300 k this may indicate the presence of other volatiles such as sulfur or organics we identified and mapped surfaces with reflectances so high as to be unlikely to be part of an ice free population in this south we find a similar distribution found by hayne et al 2015 based on uv properties in the north a cluster of pixels near that pole may represent a limited frost exposure

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

bistatic radar observations of the moon using mini rf on lro and the arecibo observatory the miniature radio frequency mini rf instrument aboard nasa s lunar reconnaissance orbiter lro is a hybrid dual polarized synthetic aperture radar sar that operated in concert with the arecibo observatory to collect bistatic radar data of the lunar nearside from 2012 to 2015 the purpose of this bistatic campaign was to characterize the radar scattering properties of the surface and near surface as a function of bistatic angle for a variety of lunar terrains and search for a coherent backscatter opposition effect indicative of the presence of water ice a variety of lunar terrain types were sampled over a range of incidence and bistatic angles including mare highland pyroclastic crater ejecta and crater floor materials responses consistent with an opposition effect were observed for the ejecta of several copernican aged craters and the floor of the south polar crater cabeus the responses of ejecta material varied by crater in a manner that suggests a relationship with crater age the response for cabeus was observed within the portion of its floor that is not in permanent shadow the character of the response differs from that of crater ejecta and appears unique with respect to all other lunar terrains observed analysis of data for this region suggests that the unique nature of the response may indicate the presence of near surface deposits of water ice

multispectral photometry of the moon and absolute calibration of the clementine uv vis camera abstract we present a multispectral photometric study of the moon between solar phase angles of 0 and 85 using clementine images obtained between 0 4 and 1 0 m we produce a comprehensive study of the lunar surface containing the following results 1 empirical photometric functions for the spectral range and viewing and illumination geometries mentioned 2 photometric modeling that derives the physical properties of the upper regolith and includes a detailed study of the causes for the lunar opposition surge 3 an absolute calibration of the clementine uv vis camera the calibration procedure given on the clementine calibration web site produces reflectances relative to a halon standard and further appear significantly higher than those seen in groundbased observations by comparing clementine observations with prior groundbased observations of 15 sites on the moon we have determined a good absolute calibration of the clementine uv vis camera a correction factor of 0 532 has been determined to convert the web site www planetary brown edu clementine calibration html reflectances to absolute values from the calibrated data we calculate empirical phase functions useful for performing photometric corrections to observations of the moon between solar phase angles of 0 and 85 and in the spectral range 0 4 to 1 0 m finally the calibrated data is used to fit a version of hapke s photometric model modified to incorporate a new formulation developed in this paper of the lunar opposition surge which includes coherent backscatter recent studies of the lunar opposition effect have yielded contradictory results as to the mechanism responsible shadow hiding coherent backscatter or both we find that most of the surge can be explained by shadow hiding with a halfwidth of 8 however for the brightest regions the highlands at 0 75 1 0 m a small additional narrow component halfwidth of

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

the mars observer laser altimeter investigation the primary objective of the mars observer laser altimeter mola investigation is to determine globally the topography of mars at a level suitable for addressing problems in geology and geophysics secondary objectives are to characterize the 1064 nm wavelength surface reflectivity of mars to contribute to analyses of global surface mineralogy and seasonal albedo changes to assist in addressing problems in atmospheric circulation and to provide geodetic control and topographic context for the assessment of possible future mars landing sites the principal components of mola are a diode pumped neodymium doped yttrium aluminum garnet laser transmitter that emits 1064 nm wavelength laser pulses a 0 5 m diameter telescope a silicon avalanche photodiode detector and a time interval unit with 10 ns resolution mola will provide measurements of the topography of mars within approximately 160 m footprints and a center to center along track foot print spacing of 300 m along the mars observer subspacecraft ground track the elevation measurements will be quantized with 1 5 m vertical resolution before correction for orbit and pointing induced errors mola profiles will be assembled into a global 0 2 deg x 0 2 deg grid that will be referenced to mars center of mass with an absolute accuracy of approximately 30 m other data products will include a global grid of topographic gradients corrected individual profiles and a global 0 2 deg x 0 2 deg grid of 1064 nm surface reflectivity

climate and tectonic effects on holocene development of an alpine lake muge co se margin of tibet south west china is an important area for determining variability of the sw asian monsoon it is however also tectonically very active palaeolimnological studies in this region generally focus on climate as a direct driver of ecological change rarely considering the effects of tectonic activity and catchment ontogeny we present diatom and organic matter data from a holocene sediment record from muge co an alpine lake located on an active fault zone in the southeast margin of tibet and explore the possible drivers of ecological change a major change occurred at 9000 cal bp when the diatom assemblage switched from benthic to predominantly planktonic forms and organic matter content decreased rapidly comparison of the holocene diatom record with a regional data set of lake surface sediments using detrended canonical correspondence analysis dcca suggests that this change in diatom development was mainly associated with changing water depth most likely linked to a seismically triggered landslide

distributional variations in marine crenarchaeotal membrane lipids a new tool for reconstructing ancient sea water temperatures it has recently been shown that membrane lipids of marine crenarchaeota a ubiquitous and abundant component of plankton occur in relatively high concentrations in recent and ancient sediments in this study we investigated the environmental controls on the relative distribution of these lipids in surface sediments we especially focussed on temperature as it is known from the thermophilic genetic relatives of marine crenarchaetoa that the composition of their membrane strongly depends on growth temperature indeed a significant linear correlation r2 0 92 is found between the number of cyclopentane rings in sedimentary membrane lipids derived from marine crenarchaeota and the annual mean sea surface temperatures this suggests that the mechanism of physical adaptation of their membrane compositions to temperature is identical to that of their thermophilic relatives in turn archaeal lipid distributions in sediments may thus allow the reconstruction of sea water temperatures of ancient marine environments

lunar impact basins new data for the western limb and far side orientale and south pole aitken basins from the first galileo flyby compositional aspects of impact basin materials can be analyzed using multispectral image data acquired by the galileo solid state imaging ssi experiment during the december 1990 lunar encounter these data provide important information on the spectral properties of the western lunar limb and parts of the far side the ssi images cover the wavelength range 0 4 1 0 m allowing measurement of spectral slope and estimation of the strength of the 1 m absorption due to iron in the mafic minerals olivine and pyroxene among deposits of the 930 km diameter orientale basin exterior ejecta comprising the hevelius formation is relatively homogeneous and spectrally similar to mature apollo 16 soils suggesting an upper crustal source the centrally located maunder formation is distinct from the younger mare basalts but comparable to the hevelius formation in its spectral reflectance properties supporting an interpretation as basin impact melt the montes rook formation located in an annulus between the maunder and the hevelius shows a slightly stronger mafic absorption and may be the deepest crustal material excavated the distal orientale deposits show local mafic enhancements in the schiller schickard and mendel rydberg regions interpreted to represent pre orientale mare deposits or cryptomaria intermixed with overlying basin ejecta in this case maria of sizes comparable to those presently observed were widespread in this region before the orientale impact mixing model analyses are consistent with the ballistic erosion and sedimentation model for ejecta emplacement in the distal regions beyond the continuous ejecta deposit on the southern lunar farside a huge area with an enhanced mafic absorption corresponds to the interior and rim of the pre nectarian south pole aitken impact basin 2000 2500 km in diameter the anomaly is interpreted to be due to several factors including excavation into the more mafic lower crust and the presence of extensive early volcanic fill cryptomare similar to that seen in ancient basins such as smythii and australe these results show that although basin forming events are an important factor in producing lateral heterogeneities in crustal composition and in modifying preexisting deposits such as cryptomaria the majority of material in even the largest basins was excavated from crustal levels our results suggest a gradational vertical crustal stratigraphy consisting of an uppermost mixed crustal layer of anorthosite basin ejecta and cryptomaria deposits generally corresponding to the megaregolith an upper crustal layer of anorthosite and a lower more noritic layer many of the basic questions remaining from this study could be addressed by global high resolution geochemical and mineralogical data obtained by polar orbiting spacecraft

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

distributions and temperature dependence of branched glycerol dialkyl glycerol tetraethers in recent lacustrine sediments from china and nepal 1 glycerol dialkyl glycerol tetraether gdgt membrane lipids in surface sediments from 24 lakes in china and nepal were analyzed the result shows that branched gdgt lipids occur widely in the studied lake sediments the different distribution of branched gdgts between the chinese soils from weijers et al 2007b and the chinese lake sediments indicates that the branched gdgts in the lacustrine sediment are the mixture of allochthonous and autochthonous branched gdgts our result supports the suggestion that temperature is the principal factor affecting the distribution of gdgts seasonality sources and precipitation increase the uncertainty of the correlation between the methylation index of branched tetraethers mbt cyclization ratio of branched tetraethers cbt proxy and the temperature the correlations of the mbt cbt index with mean annual air temperature t for the global lakes are t 6 803 7 062 cbt 37 090 mbt n 139 p 0 0001 r2 0 62 and rmse 5 24 c for the global lakes with ph 8 5 t 3 949 5 593 cbt 38 213 mbt n 100 p 0 0001 r2 0 73 and rmse 4 27 c the significant correlation suggests that the mbt cbt proxy might be used as a potential paleotemperature proxy in the limnic environment the mbt cbt proxy provides an independent way to evaluate and verify the sensitivities of the different proxies for paleotemperature reconstruction from lacustrine sediments

the global topography of mars and implications for surface evolution elevations measured by the mars orbiter laser altimeter have yielded a high accuracy global map of the topography of mars dominant features include the low northern hemisphere the tharsis province and the hellas impact basin the northern hemisphere depression is primarily a long wavelength effect that has been shaped by an internal mechanism the topography of tharsis consists of two broad rises material excavated from hellas contributes to the high elevation of the southern hemisphere and to the scarp along the hemispheric boundary the present topography has three major drainage centers with the northern lowlands being the largest the two polar cap volumes yield an upper limit of the present surface water inventory of 3 2 to 4 7 million cubic kilometers

increased multidecadal variability of the north atlantic oscillation since 1781 the north atlantic oscillation controls winter climate variability in eastern north america and europe coral derived records of sea surface temperature in bermuda suggest that multidecadal variability of the north atlantic oscillation has increased in the past few decades relative to the early nineteenth century

evaluation of glycerol dialkyl glycerol tetraether proxies for reconstruction of the paleo environment on the qinghai tibetan plateau the uplift of the qinghai tibetan plateau has a great effect on local and global climate changes here we report the late holocene climate change in the northern plateau by using a 3490 year sediment core record from kusai lake glycerol dialkyl glycerol tetraethers gdgts collected from the core were examined in combination with other paleo environmental proxies the reconstructed mean annual air temperatures maat using branched gdgt membrane lipids of certain bacteria proxies are higher than the measured maat but much closer to measured summer air temperatures suggesting a possibility of a bias of the reconstructed maat towards summer temperatures the ph values derived from a branched gdgt proxy show a negative correlation with toc a lake productivity indicator in arid regions furthermore both cbt ph and toc show temporal cyclic changes which suggest that the branched gdgt derived ph index may be useful in reconstructing paleo ph values in a lacustrine system lastly the composition of isoprenoid gdgts membrane lipids of archaea shows a major shift around 1400 bp which is in line with a large increase in sediment soluble salts at this time but lags behind the onset of salt mineral precipitation by 600 yr suggesting that change in archaeal community composition and salt mineral precipitation may require different threshold values of salinity the results of this study demonstrate that useful paleo climatic and paleo environmental information can be extracted from the gdgts preserved in lake sediments

lunar swirls examining crustal magnetic anomalies and space weathering trends 1 we have used multispectral images from clementine and data from lunar prospector s magnetometer to conduct a survey of lunar crustal magnetic anomalies prominent lunar swirls and lesser known swirl markings to provide new information on the nature of swirls and their association with magnetic anomalies we find that all swirls and swirl like albedo patterns are associated with areas of magnetized crust but not all areas of magnetized crust are colocated with swirl like albedo anomalies all observed swirls exhibit spectral characteristics similar to immature material and generally have slightly lower feo values compared with their surroundings as determined with a multispectral iron mapping method we discuss these results in relation to the various hypotheses for swirl formation the comet impact hypothesis for lunar swirls would not predict a difference in the spectrally determined feo content between swirls and nearby ordinary surfaces the compositional difference could be explained as a consequence of 1 magnetic shielding of the surface from the solar wind which could produce anomalous space weathering little darkening with limited reddening and potentially alter the predictions of the multispectral iron mapping algorithm while the compositional contrast could be enhanced by delivery of lower feo ejecta from outside the swirl and 2 accumulation of fine plagioclase rich dust moving under the influence of electric fields induced by solar wind interactions with a magnetic anomaly therefore we cannot at present clearly distinguish between the solar wind shielding and electrostatic dust accumulation models for swirl formation we describe future measurements that could contribute to solution of the puzzle of swirl origin

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