importance of depth and intensity of convection on the isotopic composition of water vapor as seen from iasi and tes δd observations abstract we use tropical observations of the water vapor isotopic composition derived from iasi and tes spaceborne measurements to show that the isotopic composition of water vapor in the free troposphere is sensitive to both the depth and the intensity of convection we find that for any given precipitation intensity vapor associated with deep convection is isotopically depleted relative to vapor associated with shallow convection the intensity of precipitation also plays a role as for any given depth of convection the relative enrichment of water vapor decreases as the intensity of precipitation increases shallow convection via the uplifting of enriched boundary layer air into the free troposphere and the convective detrainment enriches the free troposphere in contrast deep convection is associated with processes that deplete the water vapor in the free troposphere such as rain re evaporation the results of this study allow for a better identification of the parameters controlling the isotopic composition of the free troposphere and indicate that the isotopic composition of water vapor can be used to evaluate the relative contributions of shallow and deep convection in global models

coordinated hydrological regimes in the indo pacific region during the past two millennia instrumental data suggest that major shifts in tropical pacific atmospheric dynamics and hydrology have occurred within the past century potentially in response to anthropogenic warming to better understand these trends we use the hydrogen isotopic ratios of terrestrial higher plant leaf waxes delta d wax in marine sediments from southwest sulawesi indonesia to compile a detailed reconstruction of central indo pacific warm pool ipwp hydrologic variability spanning most of the last two millennia our paleodata are highly correlated with a monsoon reconstruction from southeast asia indicating that intervals of strong east asian summer monsoon easm activity are associated with a weaker indonesian monsoon im furthermore the centennial scale oscillations in our data follow known changes in northern hemisphere climate e g the little ice age and medieval warm period implying a dynamic link between northern hemisphere temperatures and ipwp hydrology the inverse relationship between the easm and im suggests that migrations of the intertropical convergence zone and associated changes in monsoon strength caused synoptic hydrologic shifts in the ipwp throughout most of the past two millennia

improved gravity field of the moon from lunar prospector an improved gravity model from doppler tracking of the lunar prospector lp spacecraft reveals three new large mass concentrations mascons on the nearside of the moon beneath the impact basins mare humboltianum mendel ryberg and schiller zucchius where the latter basin has no visible mare fill although there is no direct measurement of the lunar farside gravity lp partially resolves four mascons in the large farside basins of hertzsprung coulomb sarton freundlich sharonov and mare moscoviense the center of each of these basins contains a gravity maximum relative to the surrounding basin the improved normalized polar moment of inertia 0 3932 0 0002 is consistent with an iron core with a radius of 220 to 450 kilometers

timing of crystallization of the lunar magma ocean constrained by the oldest zircon the primitive moon was covered with a thick layer of melt known as the lunar magma ocean whose crystallization resulted in the moon s surface as it is observed today dating of the oldest zircon so far in lunar rocks indicates that much of the magma was probably crystallized within 100 million years of the moon s formation

proportions of convective and stratiform precipitation revealed in water isotope ratios distinguishing convective and stratiform rainfall is key to understanding how the water cycle responds to climate change an analysis of satellite and surface data shows that rain isotope ratios reflect the proportions of these types of rain

the bombardment history of the moon as recorded by 40 ar 39 ar chronology new petrography and 40ar 39ar ages have been obtained for 1 3 mm sized rock fragments from apollo 16 station 13 soil 63503 north ray crater ejecta and chips from three rocks collected by apollo 16 and apollo 17 missions selection of these samples was aimed at the old 40ar 39ar ages to understand the early history of the lunar magnetic field and impact flux fifteen samples were studied including crustal material polymict feldspathic fragmental breccias and impact melts the impact ages obtained range between approximately 3 3 and 4 3 billion years ga polymict fragmental breccia 63503 1 exhibits the lowest signs of recrystallization observed and a probable old relic age of 4 547 0 027 the plateau age of 4 293 0 044 ga obtained for impact melt rock 63503 13 represents the oldest known age for such a lithology possibly this age represents the minimum age for the south pole aitken spa basin in agreement with literature data these results show that impact ages 3 9 ga are found in lunar rocks especially within soil 63503 impact exhumation of deep seated warm crustal material onto the lunar surface is considered to explain the common 4 2 ga ages obtained for weakly shocked samples from soil 63503 and apollo 17 this would directly imply that one or more basin forming events occurred at that time some rock fragments showing none to limited petrologic features indicate thermal annealing these rocks may have lost ar while resident within the hot ejecta of a large basin concurrent with previous studies these results lead us to advocate for a complex impact flux in the inner solar system during the initial approximately 1 3 ga

lunar impact history constrained by grail derived basin relaxation measurements abstract grail observations have been used to derive an updated catalog of lunar impact basins with diameters 450 km in this study we assess the age and relaxation state of these basins and find that the 13 15 stratigraphically younger basins are significantly less relaxed than the 8 16 identifiable older basins the change in relaxation state is most likely a signature of the cooling of the base of the lunar crust below 1300 1400 k which we infer happened between 4 21 4 45 ga based on geochronological measurements we compare the predicted number of basins before and after this reference point with several different modeled lunar cratering chronologies while these models are sensitive to the ratio of 1km 450 km craters we conclude that a model with a broad period of late heavy bombardment a sawtooth is more likely to fit both the number of relaxed and unrelaxed basins and the mass of material delivered as a late veneer

water isotopes in precipitation data model comparison for present day and past climates abstract variations of hdo and h2 18 o concentrations are observed in precipitation both on a geographical and on a temporal basis these variations resulting from successive isotopic fractionation processes at each phase change of water during its atmospheric cycle are well documented through the iaea wmo network isotope concentrations are in middle and high latitudes linearly related to the annual mean temperature at the precipitation site paleoclimatologists have used this relationship to infer paleotemperatures from isotope paleodata extractable from ice cores deep groundwater and other such sources for this application to be valid however the spatial relationship must also hold in time at a given location as the location undergoes a series of climatic changes progress in water isotope modeling aimed at examining and evaluating this assumption has been recently reviewed jouzel et al 1997 with a focus on polar regions and more specifically on greenland we extend this review in comparing the results of two different isotopic agcms nasa giss and echam and in examining with a more global perspective the validity of the above assumption i e the equivalence of the spatial and temporal isotope temperature relationships these results confirm the dominating role of local temperature changes on the paleo isotope signal in most regions however the exact calibration of this valuable paleothermometer is biased by for example the seasonality of precipitation and other factors we forced the two models by the climatic boundary conditions of the mild holocene at 6 kyr bp which only slightly differs from today s climate the isotope response on this weak forcing is quite heterogeneous the only robust common response is the intensification of the hydrological cycle in low latitudes and therefore isotopically more depleted precipitation in the tropics and subtropics we also examine recent progress made in modeling the relationship between the conditions prevailing in moisture source regions for precipitation and the deuterium excess of that precipitation

large variations in holocene solar activity constraints from 10be in the greenland ice core project ice core 1 cosmogenic radionuclides extracted from ice cores hold a unique potential for reconstructing past solar activity changes beyond the direct instrumental period taking the geomagnetic modulation into account the solar activity in terms of the heliospheric modulation function can quantitatively be reconstructed in high resolution throughout the holocene for this period our results reveal changes in heliospheric modulation of galactic cosmic rays significantly larger than the variations reconstructed on the basis of neutron monitor measurements of galactic cosmic rays for the last 50 years moreover the 10be data from the greenland ice core project ice core as well as 14c support a high current solar activity however although the reconstruction of solar activity on long timescales is difficult our result suggests that the modern activity state of the sun is not that exceptional regarding the entire holocene this extended solar activity record provides the basis for further detailed investigations on solar and cosmic ray physics as well as on solar forcing of the earth s climate whose importance is suggested by increasing paleoclimatic evidences

physical state of the very early earth abstract the earliest surface environment of the earth is reconstructed in accordance with the planetary formation theory formation of an atmosphere is an inevitable consequence of earth s formation the atmosphere near the close of accretion is composed of 200 300 bars of h2 and h2o and several tens of bars of co and co2 either by the blanketing effect of the proto atmosphere or heating by large planetesimal impacts a magma ocean is formed during accretion we can distinguish three stages for the thermal evolution of the magma ocean and proto crust stage 0 is characterized by a super liquidus or completely molten regime near the surface at this stage the surface of the earth is covered by a super liquidus magma ocean no chemical differentiation is expected during this stage once the energy flux released by planet formation decreases to the 200 w m2 level the super liquidus magma ocean then disappears within a time interval of 1 m y this is the transition from stage 0 to 1 stage 1 is characterized by a partially molten magma ocean in the magma ocean consisting of 20 30 partial melt heat transport is controlled by melt solid separation a type of compositional convection rather than thermal convection chemical differentiation of the mantle mainly occurs in this stage once the energy flux drops to the 160 w m2 level more than 90 of water vapor in the proto atmosphere condense to form the proto oceans several tens of bars of co and co2 remain in the atmosphere just after formation of the oceans water oceans are occasionally evaporated by large impacts after each such event recondensation of the ocean takes several hundred years although the surface is covered by a chilled proto crust it is short lived because of extensive volcanic resurfacing activity as well as meteorite impacts resurfacing this stage ends when the energy flux drops to 0 1 1 w m2 level the duration time of stage 1 is estimated to be several hundred million years the best estimate is about 400 m y stage 2 is characterized by solid state convection this stage continues to the present day one of the most important change on the proto earth is the transition from stage 1 to 2 which occurs several hundred million years after the earth formation long lived crust is formed only after this transition

beryllium 10 transport to antarctica results from seasonally resolved observations and modeling 1 cosmogenic 10be measured in polar ice cores has important application in the reconstruction of past solar activity however the processes controlling its atmospheric transport and deposition to the ice sheets are not fully understood here we use the seasonal changes in 10be concentrations in a 10 year monthly resolved ice core record from the law dome site east antarctica in conjunction with echam5 ham general circulation model gcm simulations of 10be and 7be deposition as tools to examine this problem maximum 10be concentrations are observed in the ice core during the austral late summer to early autumn summer autumn while minimum concentrations are observed during the austral winter the gcm simulations corroborated by earlier observations of 10be 7be ratios in antarctica from the georg von neumayer air sampling station suggest that the 10be concentration maximum is linked to direct input of stratospheric 10be from the antarctic stratosphere to the lower levels of the antarctic troposphere during the austral summer autumn this result contrasts with the modeled transport of 10be to greenland where the seasonal maximum in stratospheric input is seen in the late winter to spring synchronous with the timing of the seasonal maximum in midlatitude stratosphere to troposphere exchange our results suggest that a different combination of processes is responsible for the transport of 10be to the antarctic and greenland ice sheets

near far side asymmetry in the tidally heated moon abstract using viscoelastic mass spring model simulations to track heat distribution inside a tidally perturbed body we measure the near far side asymmetry of heating in the crust of a spin synchronous moon in eccentric orbit about the earth with the young moon within 8 earth radii of the earth we find that tidal heating per unit area in a lunar crustal shell is asymmetric due to the octupole order moment in the earth s tidal field and is 10 to 20 higher on its near side than on its far side tidal heating reduces the crustal basal heat flux and the rate of magma ocean crystallization assuming that the local crustal growth rate depends on the local basal heat flux and the distribution of tidal heating in latitude and longitude a heat conductivity model illustrates that a moderately asymmetric and growing lunar crust could maintain its near far side thickness asymmetry but only while the moon is near the earth

the tidal rotational shape of the moon and evidence for polar wander analysis of the moon s topography reveals that when its largest basins are removed the lunar shape is consistent with processes controlled by early earth tides and implies a reorientation of the moon s principal shape axes attempts to assess the various theories for the formation of the moon and to determine its true shape are complicated by the presence of several large basins on its surface that formed after the crust solidified here ian garrick bethell et al concentrate on the topography and gravity outside these basins and propose that the long wavelength shape of the moon has evolved through a combination of two early tidal processes first a crust building process controlled by early tidal heating throughout the moon and second the later development of a frozen tidal rotational bulge the authors also infer that an uneven distribution of internal density eventually reoriented the moon s polar axis by about 36 to the configuration that we see today the origin of the moon s large scale topography is important for understanding lunar geology1 lunar orbital evolution2 and the moon s orientation in the sky3 previous hypotheses for its origin have included late accretion events4 large impacts5 tidal effects6 and convection processes7 however testing these hypotheses and quantifying the moon s topography is complicated by the large basins that have formed since the crust crystallized here we estimate the large scale lunar topography and gravity spherical harmonics outside these basins and show that the bulk of the spherical harmonic degree 2 topography is consistent with a crust building process controlled by early tidal heating throughout the moon the remainder of the degree 2 topography is consistent with a frozen tidal rotational bulge that formed later at a semi major axis of about 32 earth radii the probability of the degree 2 shape having both tidal heating and frozen shape characteristics by chance is less than 1 we also infer that internal density contrasts eventually reoriented the moon s polar axis by 36 4 to the configuration we observe today together these results link the geology of the near and far sides and resolve long standing questions about the moon s large scale shape gravity and history of polar wander

a new view of lunar ferroan anorthosites postmagma ocean petrogenesis 1 new melting experiments in the range of 0 1 mpa to 4 7 gpa provide the basis for calculations of polybaric crystallization which show that both a 300 km deep magma ocean mo enriched in refractory elements and a 600 km deep magma ocean with refractory element concentrations similar to the earth s upper mantle produce sufficient amounts of differentiated residual liquid capable of crystallizing the troctolitic noritic mineral assemblages that are prevalent in lunar ferroan anorthosites lfa however the both oceans become saturated with augite after 20 30 crystallization of the plagioclase saturated residuum and thereafter are no longer capable of producing noritic assemblages a second set of melting experiments reveals the existence of a previously unrecognized equilibrium augite liquid pigeonite plagioclase and a thermal minimum on the pigeonite plagioclase liquidus surface at 0 6 gpa these equilibria will produce melts of mafic cumulates with lower wo content than those from which the cumulates originally formed in a postmagma ocean environment of overturning mafic cumulates melt thus formed and entrained in a buoyant segregation of plagioclase would then form diapiric masses that would crystallize troctolitic noritic assemblages after intruding upward diapiric intrusions could also provide the local deformational environment needed to produce the apparently high 95 plagioclase modes of the lfa an unstable density profile in the cumulate pile following crystallization of most of the mo should provide the impetus for overturn and the heat for partially remelting mafic cumulates

magnetic field generation in the lunar core the role of inner core growth abstract the source of the magnetic field recorded in the lunar crust remains an unresolved problem the field was most likely produced by a self sustaining dynamo in the moon s electrically conducting metal core but heat flux across the core mantle boundary was probably insufficient to power a dynamo for the field s currently known duration from 4 2 to 3 56 ga since seismic measurements indicate the existence of a solid iron inner core in addition to a still liquid iron alloy outer core inner core solidification and its associated thermochemically driven convection in the outer core could have been responsible for extending the dynamo s lifetime even in the absence of superadiabatic heat flux here we present a coupled mantle core thermal evolution model of the moon and show that core solidification could explain the onset and shutoff of the lunar dynamo consistent with the global magnetic field inferred from the paleomagnetic record

evidence of impact melt sheet differentiation of the lunar south pole aitken basin the south pole aitken spa basin is the largest basin on the moon the basin forming impact likely melted the upper part of the mantle and formed an impact melt sheet impact melt of large terrestrial craters differentiated following a general magmatic differentiation sequence however it is still debated whether or not the spa melt sheet underwent differentiation to address this we investigated the vertical and lateral variations in mineral composition of the spa impact melt sheet area by analyzing the surface mineralogy including 277 post spa craters using remote sensing reflectance data we identified a 7 km thick high ca pyroxene rich layer and below that a 8 km thick low ca pyroxene rich layer both filled the entire impact melt sheet area 630 km in diameter considering the vast distribution of these two layers their thicknesses their feo abundances around 13 5 wt which are lower than most of the lunar mare basalt but within the estimated range of the differentiated spa impact melt and that the observed lithologies are consistent with a differentiation model we conclude that the spa impact melt was differentiated moreover based on the lunar magma ocean differentiation model al2o3 and cao abundances of the upper part of the mantle would be much lower after the mantle overturn if the spa impact occurred after overturn these elemental abundances of the initial impact melt would be much lower than that of the before overturn impact case and result in different solidified layers our observation matches only the after overturn case which may imply that the spa impact occurred after overturn

geological constraints on the precambrian history of earth s rotation and the moon s orbit over the past decade the analysis of sedimentary cyclic rhythmites of tidal origin i e stacked thin beds or laminae usually of sandstone siltstone and mudstone that display periodic variations in thickness reflecting a strong tidal influence on sedimentation has provided information on earth s paleorotation and the evolving lunar orbit for precambrian time before 540 ma depositional environments of tidal rhythmites range from estuarine to tidal delta with a wave protected distal ebb tidal delta setting being particularly favorable for the deposition and preservation of long detailed rhythmite records the potential sediment load of nearshore tidal currents and the effectiveness of the tide as an agent of sediment entrainment and deposition are related directly to tidal range or maximum tidal height and consequent current speed hence the thickness of successive laminae deposited by tidal currents can be a proxy tidal record with paleotidal and paleorotational values being determined by analysis of measured records of lamina and cycle thickness the validity of the findings can be investigated by testing the primary observed values for internal self consistency through application of the laws of celestial mechanics paleotidal and paleorotational values provided by late neoproterozoic 620 ma tidal rhythmites in south australia are validated by these tests and indicate 13 1 0 1 synodic lunar months yr 400 7 solar days yr a length of day of 21 9 0 4 h and a relative earth moon distance a a0 of 0 965 0 005 the mean rate of lunar recession since that time is 2 17 0 31 cm yr which is little more than half the present rate of lunar recession of 3 82 0 07 cm yr obtained by lunar laser ranging the late neoproterozoic data militate against significant overall change in earth s moment of inertia and radius at least since 620 ma cyclicity displayed by paleoproterozoic 2450 ma banded iron formation in western australia may record tidal influences on the discharge and or dispersal of submarine hydrothermal plumes and suggests 14 5 0 5 synodic months yr and a a0 0 906 0 029 the combined rhythmite data give a mean rate of lunar recession of 1 24 0 71 cm yr during most of the proterozoic 2450 620 ma suggesting that a close approach of the moon did not occur during earlier time concentrated study of precambrian tidal rhythmites promises to illuminate the evolving dynamics of the early earth moon system and may permit the lunar orbit to be traced back to near the time of the moon s origin

crustal thickness of the moon new constraints from gravity inversions using polyhedral shape models a new method is presented for estimating crustal thickness from gravity and topography data on the moon by calculating analytically the exterior gravitational field for a set of arbitrarily shaped polyhedra relief along the crust mantle interface can be inverted for that satisfies the observational constraints as this method does not rely upon filtering the bouguer anomaly which was required with previous inversions performed in the spherical harmonic domain and as the dramatic variations in spatial quality of the lunar gravity field are taken into account our crustal thickness model more faithfully represents the available data using our model results we investigate various aspects of the prominent nearside impact basins the crustal thickness in the central portion of the orientale and crisium basins is found to be close to zero suggesting that these basins could have conceivably excavated into the lunar mantle furthermore given our uncertain knowledge of the density of the crust and mantle it is possible that the humorum humboldtianum nectaris and smythii basins could have excavated all the way through the crust as well the crustal structure for most of the young impact basins implies a depth diameter ratio of about 0 08 for their excavation cavities as noted in previous studies however the crustal structure of imbrium and serenitatis is anomalous which is conceivably a result of enhanced rates of post impact viscous relaxation caused by the proximity of these basins to the procellarum kreep terrane impact basins older than smythii show little or no evidence for crustal thinning suggesting that these ancient basins were also affected by high rates of viscous relaxation resulting from higher crustal temperatures early in the moon s evolution the lithosphere beneath many young basins is found to be supporting a downward directed force even after the load associated with the mare basalts is removed and this is plausibly attributed to superisostatic uplift of the crust mantle interface those basins that are close to achieving a pre mare isostatic state are generally found to reside within or close to the procellarum kreep terrane

early lunar magnetism it is uncertain whether the moon ever formed a metallic core or generated a core dynamo the lunar crust and returned samples are magnetized but the source of this magnetization could be meteoroid impacts rather than a dynamo here we report magnetic measurements and 40ar 39ar thermochronological calculations for the oldest known unshocked lunar rock troctolite 76535 these data imply that there was a long lived field on the moon of at least 1 microtesla approximately 4 2 billion years ago the early age substantial intensity and long lifetime of this field support the hypothesis of an ancient lunar core dynamo

the lunar mascons revisited the entire spectra of the surface topography and gravity field of lunar mascons are well presented by the high resolution clementine data the negative correlation between the topography and gravitational potential of the mascons suggests that they are dynamically supported both elastic support and viscous decay models are examined for the elastic support models the spectral characteristics and the lateral variations of the thickness of the elastic layer are determined on the basis of the thin spherical shell flexure formulation and using only the antivarying harmonics of the topography and potential an elastic layer thickness of about 50 km is required to support imbrium serenitatis and nectaris mascons about 35 km for crisium mascon and about 30 km for smythii and humorum mascons a layer of about 20 km thickness can support orientale mascon the strength envelopes of the upper 100 km of the moon within 4 3 gyr ago show that the elastic layer was not thick enough to support the mascons in the early history they decayed through viscous deformation of the lunar interior a lower limit of 6 1024 pa s is estimated for the lunar viscosity within 3 6 3 gyr ago we also determine the thicknesses of the crust and mare flows of the mascon basins on the basis of the assumption that the basins were isostatically compensated prior to the mascon formation the crust beneath the mascon basins is about 30 40 km except for crisium and orientale where the crust is about 20 km the mare flows of about 3 6 km are obtained for almost all of the mascon basins the topography and gravitational potential of aitken basin shows that the basin is compensated at 52 54 km depth the mantle beneath the basin has rebounded upward by about 20 30 km and is overlain by about 20 25 km of a mixture of the excavated crustal and mantle material the lack of a mascon and pervasive mare flows in the basin brings into question the current models of the mascon formation

local to regional scale variability of annual net accumulation on the greenland ice sheet from parca cores a suite of spatially distributed cores collected under the program for arctic regional climate assessment parca provides an unprecedented opportunity to assess local to regional variability of annual accumulation rates over the greenland ice sheet parca cores are unique in their broad spatial distribution and accurate dating of annual layers using multiple seasonally varying indicators the core data provide 1 a more rigorous evaluation of spatial and temporal variations in accumulation rates 2 critical input to ice sheet mass balance estimates 3 ground truth measurements for satellite observations and climate model based precipitation estimates and 4 important constraints on paleoclimatic interpretations from ice cores multiple closely spaced cores demonstrate that signals of high frequency annual to possibly decadal scale climate variability preserved in the ice sheet are partially masked by glaciological noise two 350 year accumulation histories one from northwest greenland and one from the summit area reveal significant multidecadal variability the regional trends show long periods 60 90 years of strong positive correlation and an equally long period of strong negative correlation since 1940 the trends have been decoupled this spatial variability reflects the strong modulation of greenland precipitation and the climate information it contains by changes in north atlantic atmospheric circulation patterns proxy records from the parca cores document that climate reconstructions from a single core must be interpreted cautiously with application of appropriate filters to reduce local noise and careful extrapolations from local to regional scales richer more robust ice core derived data sets should result from combining multiple more widely spaced cores to produce regional stacked records

lunar degree 2 potential love number determination from satellite tracking data 1 the lunar potential love number k2 has been determined using available satellite tracking data coming from the lunar orbiters i v the apollo 15 and 16 subsatellites clementine and lunar prospector some smart 1 spacecraft tracking data are also included a previous determination using spacecraft data reported k2 0 026 0 003 ten times the formal error whereas lunar laser ranging results report lower values around k2 0 0210 0 0025 the best estimate obtained here results in k2 0 0213 0 0075 ten times the formal error as well closer in agreement with the lunar laser ranging values

using the sunspot cycle to date ice cores for many ice cores the snow accumulation rate is too low to preserve annual stratigraphy precluding direct measurement of annual layer thickness for selected holocene sections of the taylor dome core east antarctica we instead use high resolution 10be measurements to establish a nominal 11 year thickness taking advantage of the solar cycle in cosmogenic isotope production we compare measured thicknesses with the layer thickness profile predicted by a finite element ice flow model the results are in good agreement supporting the assumption that the length of the solar cycle has remained essentially constant throughout the holocene for ice cores where annual layers are not preserved the 10be 11 year layer method can be used as an independent check on flow model estimates of layer thickness and to estimate past accumulation rates it should be possible to accurately date ice cores by counting 11 year layers detected with continuous high resolution 10be measurements

forming the lunar farside highlands by accretion of a companion moon the moon is a satellite of two distinct halves the nearside that faces us all the time is low in altitude flat and dark in colour whereas the farside is mountainous and deeply cratered martin jutzi and erik asphaug propose that this lunar dichotomy might be the consequence of the late accretion of a companion moon companion moons are a common outcome of giant impact and protolunar disk simulations the new calculations suggest that a collision with a companion at subsonic impact velocity leads to an accretionary pile rather than a crater resulting in a hemispheric layer consistent with the dimensions and crustal structure of the topography of the farside highlands the most striking geological feature of the moon is the terrain and elevation dichotomy1 between the hemispheres the nearside is low and flat dominated by volcanic maria whereas the farside is mountainous and deeply cratered associated with this geological dichotomy is a compositional and thermal variation2 3 with the nearside procellarum kreep potassium rare earth element phosphorus terrane and environs interpreted as having thin compositionally evolved crust in comparison with the massive feldspathic highlands the lunar dichotomy may have been caused by internal effects for example spatial variations in tidal heating4 asymmetric convective processes5 or asymmetric crystallization of the magma ocean6 or external effects such as the event that formed the south pole aitken basin1 or asymmetric cratering7 here we consider its origin as a late carapace added by the accretion of a companion moon companion moons are a common outcome of simulations8 of moon formation from a protolunar disk resulting from a giant impact and although most coplanar configurations are unstable9 a 1 200 km diameter moon located at one of the trojan points could be dynamically stable for tens of millions of years after the giant impact10 most of the moon s magma ocean would solidify on this timescale11 12 whereas the companion moon would evolve more quickly into a crust and a solid mantle derived from similar disk material and would presumably have little or no core its likely fate would be to collide with the moon at 2 3 km s 1 well below the speed of sound in silicates according to our simulations a large moon moon size ratio 0 3 and a subsonic impact velocity lead to an accretionary pile rather than a crater contributing a hemispheric layer of extent and thickness consistent with the dimensions of the farside highlands1 13 and in agreement with the degree two crustal thickness profile4 the collision furthermore displaces the kreep rich layer to the opposite hemisphere explaining the observed concentration2 3

coupled thermal orbital evolution of the early moon abstract coupled thermal orbital histories of early lunar evolution are considered in a simple model we consider a plagioclase lid overlying a magma ocean overlying a solid mantle tidal dissipation occurs in the plagioclase lid and heat transport is by conduction and melt migration we find that large orbital eccentricities can be obtained in this model we discuss possible consequences of this phase of large eccentricities for the shape of the moon and geochronology of lunar samples we find that the orbit can pass through the shape solution of garrick bethell et al garrick bethell i wisdom j zuber m 2006 science 313 652 but we argue that the shape cannot be maintained against elastic deformation as the orbit continues to evolve

gravity and tectonic patterns of mercury effect of tidal deformation spin orbit resonance nonzero eccentricity despinning and reorientation 1 we consider the effect of spin orbit resonance nonzero eccentricity despinning and reorientation on mercury s gravity and tectonic pattern large variations of the gravity and shape coefficients from the synchronous rotation and zero eccentricity values j2 c22 10 3 and b c a c 1 4 arise because of nonsynchronous rotation and nonzero eccentricity even in the absence of reorientation or despinning reorientation or despinning induces additional variations the large gravity coefficients j2 6 2 10 5 and c22 1 0 5 10 5 estimated from the mariner 10 flybys cannot be attributed to caloris alone since the required mass excess in this case would have caused caloris to migrate to one of mercury s hot poles similarly a large remnant bulge due to a smaller semimajor axis and spin orbit resonance can be dismissed since the required semimajor axis is unphysically small 0 1 au reorientation of a large remnant bulge recording an epoch of faster rotation without significant semimajor axis variations can explain the large gravity coefficients this requires initial rotation rates 20 times the present value and a positive gravity anomaly associated with caloris capable of driving 10 45 equatorward reorientation the required gravity anomaly can be explained by infilling of the basin with material of thicknesses 7 km or an annulus of volcanic plains emplaced around the basin with an annulus width 1200 km and fill thicknesses 2 km the predicted tectonic pattern due to these despinning and reorientation scenarios including some radial contraction is in good agreement with the lobate scarp pattern observed by mariner 10 we also predict that lobate scarps will follow a ne sw orientation in the eastern hemisphere and a positive gravity anomaly of a few hundred mgal associated with caloris

late 20th century increase in south pole snow accumulation a compilation of the 37 year history of net accumulation at the south pole mosley thompson et al 1995 suggests an increase in net annual accumulation since 1965 this record is sporadic and its quality is compromised by spatially restricted observations and nonsystematic measurement procedures results from a new spatially extensive network of 236 accumulation poles document that the current 5 year 1992 1997 average annual net accumulation at the south pole is 84 5 8 9 mm water equivalent w e this accumulation rate reflects a 30 increase since the 1960s when the best although not optimal records indicate that it was 65 mm w e identification of two prominent beta radioactivity horizons 1954 1955 and 1964 1965 in six firn cores confirms an increase in accumulation since 1965 viewed from a longer perspective of accumulation provided by ice cores and a snow mine study the net accumulation of the 30 year period 1965 1994 is the highest 30 year average of this millennium limited data suggest this recent accumulation increase extends beyond the south pole region and may be characteristic of the high east antarctic plateau enhanced accumulation over the polar ice sheets has been identified as a potential early indicator of warmer sea surface temperatures and may offset a portion of the current rise in global sea level

solar and climate influences on ice core 10be records from antarctica and greenland during the neutron monitor era abstract cosmogenic 10be in polar ice cores is a primary proxy for past solar activity however interpretation of the 10be record is hindered by limited understanding of the physical processes governing its atmospheric transport and deposition to the ice sheets this issue is addressed by evaluating two accurately dated annually resolved ice core 10be records against modern solar activity observations and instrumental and reanalysis climate data the cores are sampled from the dss site on law dome east antarctica spanning 1936 2009 and the das2 site southeast greenland 1936 2002 permitting inter hemispheric comparisons concentrations at both dss and das2 are significantly correlated to the 11 yr solar cycle modulation of cosmic ray intensity r xy 0 54 with 95 ci 0 31 0 70 and r xy 0 45 with 95 ci 0 22 0 62 respectively for both sites if fluxes are used instead of concentrations then correlations with solar activity decrease the strength and spectral coherence of the solar activity signal in 10be is enhanced when ice core records are combined from both antarctica and greenland the amplitudes of the 11 yr solar cycles in the 10be data appear inconsistent with the view that the ice sheets receive only 10be produced at polar latitudes significant climate signals detected in the 10be series include the zonal wave three pattern of atmospheric circulation at dss r xy 0 36 with 95 ci 0 57 0 10 and the north atlantic oscillation at das2 r xy 0 42 with 95 ci 0 64 0 15 the sensitivity of 10be concentrations to modes of atmospheric circulation advises caution in the use of 10be records from single sites in solar forcing reconstructions

diffusion in zircon despite its low abundance in most rocks zircon is extraordinarily useful in interpreting crustal histories the importance of u th pb isotopic dating of zircon is well and long established davis et al this volume parrish et al this volume zircon also tends to incorporate trace elements useful as geochemical tracers such as the ree y and hf a number of characteristics of zircon encourage the preservation of internal isotopic and chemical variations often on extremely fine scale which provide valuable insight into thermal histories and past geochemical environments the relative insolubility of zircon in crustal melts and fluids as well as its general resistance to chemical and physical breakdown often result in the existence of several generations of geochemical information in a single zircon grain the fact that this information is so frequently retained as evidenced through backscattered electron or cathodoluminescence imaging that often reveal fine scale zoning down to the sub micron scale has long suggested that diffusion of most elements is quite sluggish in zircon in this chapter we present an overview of the findings to date from laboratory measurements of diffusion of cations and oxygen in zircon because of its importance as a geochronometer attempts have been made to measure diffusion especially of pb for over 30 years but only in the last decade or so have profiling techniques with adequate depth resolution been employed in these studies resulting in a plethora of new diffusion data these findings have important implications for isotopic dating interpretation of stable isotope ratios closure temperatures and formation and preservation of primary chemical composition and zoning in zircon efforts have been made for some time to quantify and characterize diffusion in zircon most notably of pb in deference to its significance in interpreting pb isotopic signatures and refining understanding of thermal histories as is evident from

measurements of the elastic thickness under ancient lunar terrain abstract the part of a planet s gravity that is coherent with its topography provides information about the deflection of its crust after loading and hence the resistance of its lithosphere to bending at the time the load was emplaced we used observed line of sight accelerations from lunar prospector together with the accelerations we would have expected if anomalies in the gravity field were only caused by topography to estimate the admittance and coherence between topography and gravity over several regions of the lunar nearside we then compared our estimates to what we would expect if the lithosphere behaved as a floating elastic plate or shell assuming a linear relationship between topography and gravity we found in the region surrounding the southern highland crater clavius that the data can be modeled using a thin plate with t e 12 5 km and uncorrelated loads at the surface and base of the upper crust a spherical shell model with surface loading is less satisfactory to fit the admittance adequately requires topography with wavelengths over 400 km to be formed when t e 1 km and the remainder when t e 7 5 km by contrast the apparent lack of compensation around the youngest giant impact basins requires a plate with t e 80 km or a shell with t e 25 km our results indicate the thickness of the lunar lithosphere increased from 12 km in the pre nectarian to 25 km in the nectarian

vertical motions of the tropical convective cloud spectrum over darwin australia three months of profiler observations from darwin australia are separated into seven cloud types shallow mid level and deep convective weak and robust stratiform rain and transitional and ice only anvil to provide vertical velocity statistics on the full spectrum of tropical convective clouds over the course of a monsoon season consistent with past studies convective updraughts increase in height and magnitude as the convective cloud height increases shallow mid level deep convection has a mean maximum value of 0 3 m s 1 at 3 km 0 6 m s 1 at 5 km 2 5 m s 1 at 8 km deep convective extremes approach 18 m s 1 above 8 km while downdraughts in all convective cloud types are maximum below 4 km stratiform vertical velocities are weaker and less varied than in active convection with maximum mean values 0 25 m s 1 however stratiform rain regions associated with larger near surface reflectivities and thus rain rates have stronger mesoscale up and downdraughts than weaker stratiform rain regions anvil cloud with little or no rain near the surface also exhibits mesoscale up and downdraughts but the vertical velocity profile is shifted up in height by at least 2 km in addition anvil updraughts were only 20 50 of the magnitudes in the stratiform rain region overall the vertical motion statistics were similar across the pre active and suppressed monsoon periods the vertical velocity distributions for each cloud type were also generally consistent with the reflectivity distributions i e the strongest updraughts were often linked to the largest reflectivities allowing for some linkages between the dynamical and microphysical cloud properties for example strong updraughts above the 0 c level in deep convection are associated with strongly sloping reflectivity profiles supporting the importance of cold rain growth processes and stronger vertical motions are associated with stratiform rain that has a robust bright band

solar activity during the last 1000 yr inferred from radionuclide records identification of the causes of past climate change requires detailed knowledge of one of the most important natural factors solar forcing prior to the period of direct solar observations radionuclide abundances in natural archives provide the best known proxies for changes in solar activity here we present two independent reconstructions of changes in solar activity during the last 1000 yr which are inferred from be 10 and c 14 records we analyse the tree ring c 14 data shcal intca104 from 1000 to 1510 ad and annual data from 1511 to 1950 ad and four be 10 records from greenland ice cores camp century grip milcent and dye3 together with two be 10 records from antarctic ice cores dome concordia and south pole in general the be 10 and c 14 records exhibit good agreement that allows us to obtain reliable estimates of past solar magnetic modulation of the radionuclide production rates differences between be 10 records from antarctica and greenland indicate that climatic changes have influenced the deposition of be 10 during some periods of the last 1000 yr the radionuclide based reconstructions of past changes in solar activity do not always agree with the sunspot record which indicates that the coupling between those proxies is not as close as has been sometimes assumed the tree ring c 14 record and be 10 from antarctica indicate that recent solar activity is high but not exceptional with respect to the last 1000 yr c 2006 elsevier ltd all rights reserved less

water hydrogen in the lunar mantle results from petrology and magma ocean modeling abstract measurements of hydroxyl or water in lunar materials are being used to suggest that melting source regions within the moon contained tens to hundreds of ppm water the compositions of magmatic source regions in the moon can be calculated using magma ocean fractional solidification models given an initial bulk composition our magma ocean models demonstrate that to make a source region with 10 to 200 ppm water the bulk magma ocean must contain 100 to 1000 ppm water or more and in a 1000 km deep lunar magma ocean 1000 ppm water is equivalent to 5 of an earth ocean by weight as solidification of the magma ocean continues water and other incompatible elements are progressively enriched in the evolving liquids the final kreep like liquids would contain the greatest fraction of water we suggest that a bulk magma ocean with over 100 ppm water is prohibited by constraints on these kreep like final magma ocean liquids and by the thermodynamic equilibrium requirement with metallic iron in mare basalts we conclude that bulk lunar interior water contents must be at the low end of the range posited by recent observations

variations in the geomagnetic dipole moment over the last 12 000 years summary an analysis has been made of archaeointensity data for the past 12 000 years there are 3243 results from diverent areas of the world covering the past 12 000 years of these 2203 are from the european region and 1040 are from the rest of the world the archaeointensity data set analysed in the present study is almost three times larger than that used by mcelhinny senanayake 1982 although there is no major diverence between our global data and the earlier data the data for the non european region have been improved and we now have a data set for asia

secular effects of oceanic tidal dissipation on the moon s orbit and the earth s rotation the earth and moon are considered as a two body system in gravitational isolation from the sun and other planets the lunar orbit is taken as circular and the solid earth is assumed to be a rigid sphere with no tidal deformation so that there are no precessional torques other than those arising from the tidally deformed ocean numerical solutions to laplace s tidal equations with dissipation by linear bottom friction are used to obtain ocean wide distributions of tidal amplitude for two idealized continentalities a single circular continent spherical cap centered at the north pole and a single spherical cap centered on the equator calculations are made for two different values of the frictional resistance coefficient thus giving rise to four sets of solutions the computed tidal amplitudes are used to calculate the oceanic tidal torque which in turn is used to integrate the orbital equations backward in time for solution of the two body problem the coriolis parameter and the tidal frequencies change with time thus requiring that the tidal equations be solved several times during the course of each orbital integration in this manner the earth s rotational and the moon s orbital histories are determined on a geologic time scale for each of the four models the calculated position of the lunar orbit at 4 5 billion years ago is found to range from 38 to 53 earth radii in the four models and corresponds to a sidereal month of 330 to 550 hours the sidereal day would have been 12 to 18 hours with a relative inclination of 3 to 22 between the terrestrial and lunar poles these results are in sharp contrast to those from previous studies of the earth moon system most of which indicated a roche limit approach of the two bodies roughly 1 to 2 billion years ago and presented therefore a time scale difficulty in theories of lunar origin this contrast arises mainly from the fact that previous modelers avoided solution of laplace s tidal equations by prescribing a constant frictional phase lag angle between the angular position of the moon and the major axis of the second degree harmonic of the tidally deformed surface of the earth the amount of phase lag was established from the present astronomically deduced rate of tidal dissipation but this precluded dynamic variations in tidal torque over geologic time which are critical for determination of the orbital time scale the present rate of oceanic tidal dissipation is evidently anomalously high because of the near resonance of the oceanic response in both frequency and shape to the tidal forcing for the earth and moon to have evolved to their present separation from a distance of less than about 35 earth radii solely on the basis of oceanic tidal dissipation would have required the m2 response to have been near resonance for a significant portion of geologic history a rather implausible scenario the calculations reported here show that on the contrary frictional coupling between the earth and moon was much weaker than at present throughout most of the orbital history and consequently the moon s closest approach could not have been as small as 35 earth radii although idealized continentalities were used in these calculations the general conclusion of a weaker frictional coupling in the past is believed to be relatively insensitive to the continental configuration this is because at faster paleorotation the semidiurnal tidal frequencies would be resonant only with smaller scale normal modes of the ocean rather than with global scale modes as at present the time scale difficulty heretofore present in models of orbital evolution is thereby eliminated it should be noted that the orbital history developed here supports the theory of binary planetary accretion for lunar origin as opposed to fission or tidal capture

water isotopic variability in response to mesoscale convective system over the tropical ocean 1 in tropical regions the empirical negative relationship between the isotopic content of precipitation and rainfall amount known as the amount effect has been used as a rationale for paleohydroclimate reconstruction from isotope records however there is still no comprehensive physical explanation for this empirical effect here we reconsider the well known amount effect using newly available isotope data for both surface water vapor and precipitation obtained from shipboard observations in this study we hypothesized that stratiform rainfall associated with mesoscale convective systems mcss is a key process in reducing tropical water isotopic concentrations and tested this hypothesis with an idealized mcs model our conceptual model reasonably accounted for several observed features and indicated that isotopic reductions in tropical oceanic regions reflect a precipitating system s change relatively high isotope ratios corresponded to disorganized convection on the other hand mcss were characterized by lower isotope ratios with increasing stratiform area in addition the amplitude of this isotopic depletion was related to the scale of the precipitation system the lowest isotopic ratios were observed during the passage of large scale disturbances corresponding to the madden julian oscillation convective envelope in which mcss are embedded this means that the frequent appearance of mcss results in further decreases in the isotopic ratio of surface vapor and precipitation from this we conclude that the amount effect can be interpreted as the development of a precipitation system from an isolated convection cell into a large scale system containing several mcss and that past large scale convective activity can be reconstructed from isotope records

lunar multiring basins and the cratering process abstract numerous studies of the lunar gravity field have concluded that the lunar moho is substantially uplifted beneath the young multiring basins this uplift is presumably due to the excavation of large quantities of crustal material during the cratering process and subsequent rebound of the impact basin floor using a new dual layered crustal thickness model of the moon the excavation cavities of some nearside multiring basins grimaldi and larger and younger than tranquillitatis were reconstructed by restoring the uplifted moho to its preimpact location the farside south pole aitken spa basin was also considered due to its importance in deciphering lunar evolution restoring the moho to its preimpact position beneath these basins resulted in a roughly parabolic depression from which the depth and diameter of the excavation cavity could be determined using these reconstructed excavation cavities the basin forming process was investigated excavation cavity diameters were generally found to be on the small side of most previous estimates for orientale the modeled excavation cavity lies within the inner rook ring additionally with the exception of the three largest basins serenitatis imbrium and south pole aitken the depth diameter ratios of the excavation cavities were found to be 0 115 0 005 a value consistent with theoretical and experimental results for impact craters orders of magnitude smaller in size the three largest basins however appear to have significantly shallower depths of excavation compared to this trend it is possible that this may reflect a different physical process of crater formation e g nonproportional scaling special impact conditions or postimpact modification processes the crustal thickness model also shows that each basin is surrounded by an annulus of thickened crust we interpret this thickened crust as representing thick basin ejecta deposits and we show that the radial variation in the thickness of these deposits is consistent with scaling laws obtained from small scale experimental studies if multiring basins ever possessed a terraced main crater rim this terraced zone may be presently unrecognizable at the surface due to the emplacement of ejecta deposits that exceed a few kilometers in thickness exterior to the excavation cavity rim we also show that the interiors of many basins were superisostatic before mare volcanism commenced those basins that were closest to approaching a premare isostatic state lie close to or within an anomalous geochemical province rich in heat producing elements

stable water isotopes and large scale vertical motions in the tropics a complete understanding of the interaction between convection and the large scale circulation in the tropics remains an outstanding problem although there is evidence that the vertical structure of convective heating has great influence in the large scale response and that this structure also presents considerable geographical variations more need to be done one of the questions that are still unanswered is how the vertical structure of the convective heating or similarly of vertical velocity varies across the tropical pacific here it is suggested that some light can be shed on this debate by considering stable water isotopes because these tend to be progressively less abundant with increasing height precipitation associated with top heavy profiles should be expected to be more depleted than that associated with bottom heavy profiles this claim is verified with a variety of data first using observations from iaea wmo global network of isotopes in precipitation stations then using a simple model based on the budget of water isotopes in precipitation finally using a more complex isotope enabled general circulation model evidence provided by these sources confirms that different structures of vertical velocities are associated with different isotopic abundances with top heavy profiles giving rise to more depleted rainfall finally the data from over the pacific although scarce seem to suggest that precipitation in the eastern part is more enriched than in the western thus hinting at velocity profiles over the east being more bottom heavy than over the west pacific

a sawtooth like timeline for the first billion years of lunar bombardment abstract we revisit the early evolution of the moon s bombardment our work combines modeling based on plausible projectile sources and their dynamical decay rates with constraints from the lunar crater record radiometric ages of the youngest lunar basins and the abundance of highly siderophile elements in the lunar crust and mantle we deduce that the evolution of the impact flux did not decline exponentially over the first billion years of lunar history but also there was no prominent and narrow impact spike 3 9 gy ago unlike that typically envisioned in the lunar cataclysm scenario instead we show the timeline of the lunar bombardment has a sawtooth like profile with an uptick in the impact flux near 4 1 gy ago the impact flux at the beginning of this weaker cataclysm was 5 10 times higher than the immediately preceding period the nectaris basin should have been one of the first basins formed at the sawtooth we predict the bombardment rate since 4 1 gy ago declined slowly and adhered relatively close to classic crater chronology models neukum and ivanov 1994 overall we expect that the sawtooth event accounted for about one fourth of the total bombardment suffered by the moon since its formation consequently considering that 12 14 basins formed during the sawtooth event we expect that the net number of basins formed on the moon was 45 50 from our expected bombardment timeline we derived a new and improved lunar chronology suitable for use on pre nectarian surface units according to this chronology a significant portion of the oldest lunar cratered terrains has an age of 4 38 4 42 gyr moreover the largest lunar basin south pole aitken is older than 4 3 gy and therefore was not produced during the lunar cataclysm

tectonic patterns on reoriented and despun planetary bodies abstract several processes may produce global tectonic patterns on the surface of a planetary body the stresses associated with distortions of biaxial figures due to despinning or reorientation were first calculated by vening meinesz vening meinesz f a 1947 trans am geophys union 28 1 1 23 we adopt a mathematically equivalent but physically more meaningful treatment for distortions associated with rotation the new approach allows us to find analytic solutions for the general case of stresses associated with distortions of biaxial or triaxial planetary figures distortions of biaxial figures may be driven by variations in rotation rate rotation axis orientation or the combination of both distortions of triaxial figures may be driven by the same mechanisms and or variations in tidal axis orientation for tidally deformed satellites while the magnitude of the resulting stresses depends on the adopted elastic and physical parameters the expected tectonic pattern is independent of these parameters for these mechanisms reorientation of the rotation tidal axis alone is expected to produce normal thrust faulting provinces enclosing the initial rotation tidal poles and thrust normal faulting provinces enclosing the final rotation tidal poles reorientation of both the rotation and tidal axis results in a wide variety of tectonic patterns for different reorientation geometries on europa the tidal axis reorientation which generally accompanies rotation axis reorientations may provide an alternative explanation for tectonic features that have been interpreted as evidence for non synchronous rotation the observed tectonic pattern on enceladus is more easily explained by a large reorientation 90 of the rotation axis than by rotation rate variations

volcanic and solar activity and atmospheric circulation influences on cosmogenic 10be fallout at vostok and concordia antarctica over the last 60years abstract the cosmogenic nuclide beryllium 10 10be recovered from ice cores is often used to study solar activity on long timescales however the 10be signal is also influenced by factors other than the sun to identify and quantify various contributions to the 10be signal two antarctic snow records from the vostok and concordia sites spanning the last 60 years were studied at a sub annual resolution three factors that contribute to the 10be signal were identified first a significant period of approximately 11 yr that can be associated with the modulation of 10be production by solar activity was detected in both records the solar imprint constitutes 20 35 of the variance within the total signal the 11 yr 10be snow component was attenuated by a factor of 0 5 and was delayed by 1 4 yr compared to the 10be production expected within the polar atmosphere the result could be interpreted as the composite response of a stratospheric 10be reservoir with an 11 yr modulation that was attenuated and delayed with respect to 10be polar production and to a tropospheric 10be reservoir with an 11 yr modulation that was not attenuated or delayed then peaks in 10be concentrations that were 66 and 35 higher than the average concentration were observed during the stratospheric volcanic eruptions of agung in 1963 and pinatubo in 1991 respectively in light of these new results published 10be ice core records could be reinterpreted because spikes in 10be concentration appear at the time of several stratospheric events the data indicate that stratospheric volcanic eruptions can impact 10be transport and deposition as a result of the roles played by the sedimentation of sulfate aerosols and the formation and rapid settling of polar stratospheric clouds psc also an interannual variability of 4 yr was determined in both 10be records corresponding to 26 of the variance within the signal at vostok as with species of marine origin sodium this 4 yr variability is interpreted as a tropospheric modulation the 4 yr variability could be associated with atmospheric circulation associated with the coupled southern ocean ocean atmosphere system the results presented here from sites within the high antarctic plateau open new possibilities for ice core dating over the last few centuries and for the reconstruction of past solar activity in relation to climate

timing of mantle overturn during magma ocean solidification abstract solidification of magma oceans mos formed early in the evolution of planetary bodies sets the initial condition for their evolution on much longer time scales ideal fractional crystallization would generate an unstable chemical stratification that subsequently overturns to form a stably stratified mantle the simplest model of overturn assumes that cumulates remain immobile until the end of mo solidification however overturning of cumulates and thermal convection during solidification may act to reduce this stratification and introduce chemical heterogeneity on scales smaller than the mo thickness we explore overturning of cumulates before the end of mo crystallization and the possible consequences for mantle structure and composition in this model increasingly dense iron rich layers crystallized from the overlying residual liquid mo are deposited on a thickening cumulate layer overturn during solidification occurs if the dimensionless parameter r c measuring the ratio of the mo time of crystallization m o to the timescale associated with compositional overturn o v g h exceeds a threshold value if overturn did not occur until after solidification this implies that the viscosity of the solidified mantle must have been sufficiently high possibly requiring efficient melt extraction from the cumulate for a given rate of solidification for the lunar mo possible implications for the generation of the mg suites and mare basalt are suggested

interior structure of the moon constraints from seismic tomography gravity and topography abstract seismic tomography can be combined with constraints from geoid topography and other surface observations to gain information about mantle structure and dynamics this approach has been taken with much success for the earth mantle and here it is for the first time applied to the moon lunar tomography has much lower resolution as for the earth and is mostly restricted to the near side nevertheless we can assess under what assumptions the fit between predicted geoid based on a tomography model and observed geoid is best among the models tested we find the most similar pattern correlation about 0 5 if we only consider tomography below 225 km depth if density anomalies cause little or no dynamic topography and if we compare to the geoid with the flattening l 2 m 0 term removed this could mean that a like for the earth seismic anomalies shallower than 225 km are caused by a combination of thermal and compositional effects and therefore cannot be simply converted to density anomalies b the lithosphere is sufficiently thick to prevent dynamic topography more than a small fraction of total topography and c flattening is a fossil bulge unrelated to present day mantle anomalies however we have to be cautious with interpreting our results because for models with a comparatively higher correlation and a conversion from seismic velocity to density anomalies similar to the earth s upper mantle the amplitude of the predicted geoid is much lower than observed this could either mean that the tomography model is strongly damped or that the geoid is mostly due to shallow causes such as crustal thickness variations with only a small part coming from the deeper mantle

isostasy of the moon from high resolution gravity and topography data implication for its thermal history 1 the lunar prospector line of sight acceleration data after terrain correction have been inverted to the high resolution bouguer gravity anomalies of the lunar nearside lithospheric thicknesses of the early moon were investigated by comparing the gravity anomalies of craters and impact basins of various dimensions the lithosphere was already thick enough to support craters with diameters up to 300 km in the pre nectarian and nectarian periods degree of isostatic compensation of larger impact basins suggested lithospheric thickness of 20 60 km at that time which depended more on localities rather than age differences

evidence for lunar true polar wander and a past low eccentricity synchronous lunar orbit as first noted 200 years ago by laplace the moon s rotational and tidal bulges are significantly larger than expected given the moon s present orbital and rotational state this excess deformation has been ascribed to a fossil figure frozen in when the moon was closer to the earth however the observed figure is only consistent with an eccentric and non synchronous orbit contrary to our understanding of the moon s formation and evolution here we show that lunar mascons and impact basins have a significant contribution to the observed lunar figure removing their contribution reveals a misaligned fossil figure consistent with an early epoch of true polar wander driven by the formation of the south pole aitken basin and an early low eccentricity synchronous lunar orbit this new self consistent model solves a long standing problem in planetary science and will inform future studies of the moon s dynamical evolution and early dynamo

model based constraints on interpreting 20th century trends in ice core 10be 1 beryllium 10 ice core records are useful for understanding solar magnetic field changes over time and in particular over the 20th century during which there are a variety of relevant observations however differences between 10be snow concentration records from different locations complicate the process of developing a coherent understanding of changes in cosmogenic isotope production we use the goddard institute for space studies modele general circulation model to simulate the production and transport of beryllium isotopes for this time period we compare our results with surface air observations and with ice core records from dye 3 taylor dome and south pole we find that unforced weather related internal variability causes modeled trends in 10be snow concentration to vary from the ensemble mean by 50 and greater at all three ice core locations lower levels of internal variability at taylor dome and south pole relative to dye 3 make the simulated 10be values at these locations better estimates of the ensemble mean trend in 10be snow concentration in addition the ensemble mean concentration trend at dye 3 was significantly different from the expected modeled trend based on applied production changes alone overall the results imply that during the 20th century 10be data from multiple cores are likely to be required to make meaningful inferences about 10be production changes the model simulations imply that data from antarctica are likely to be more robust

lunar cryptomaria physical characteristics distribution and implications for ancient volcanism cryptomaria lunar volcanic deposits obscured by crater and basin impact ejecta can provide important information about the thermal and volcanic history of the moon the timing of cryptomare deposition has implications for the duration and flux of mare basalt volcanism in addition knowing the distribution of cryptomaria can provide information about mantle convection and lunar magma ocean solidification here we use multiple datasets e g m3 lola lroc diviner to undertake a global analysis to identify the general characteristics e g topography surface roughness rock abundance albedo etc of lunar light plains in order to better distinguish between ancient volcanic deposits cryptomaria and impact basin and crater ejecta deposits we find 20 discrete regions of cryptomaria covering approximately 2 of the moon which increase the total area covered by mare volcanism to 18 of the lunar surface comparisons of light plains deposits indicate that the two deposit types volcanic and impact produced are best distinguished by mineralogic data on the basis of cryptomaria locations the distribution of mare volcanism does not appear to have changed in the time prior to its exposed mare basalt distribution there are several hypotheses explaining the distribution of mare basalts which include the influence of crustal thickness mantle convection patterns asymmetric distribution of source regions kreep distribution and the influence of a proposed procellarum impact basin the paucity of farside mare basalts means that multiple factors such as crustal thickness variations and mantle convection are likely to play a role in mare basalt emplacement

isotopic evidence for a young lunar magma ocean abstract mare basalt sources and ferroan anorthosite suite cumulates define a linear array on a 146sm 144nd versus 142nd 144nd isochron plot demonstrating these materials were derived from a common reservoir at 4336 31 32 ma the minimum proportion of the moon that was in isotopic equilibrium at this time is estimated to be 1 3 of its entire volume based on the geographic extent from which the analyzed samples were collected and the calculated depths from which the samples were derived scenarios in which large portions of the moon were molten to depths of many hundreds of kilometers are required to produce the observed sm nd isotopic equilibrium between the mantle and crustal rocks at 4 34 ga this is a consequence of the fact that limited heating of a solid moon above the blocking temperature of the sm nd isotopic system is insufficient to diffusively homogenize radiogenic nd throughout the mantle and crust there are three scenarios that might account for global scale isotopic equilibrium on the moon relatively late in solar system history including 1 sm nd re equilibration of a solid moon resulting from widespread melting in response to mantle overturn or a very large impact 2 early accretion of the moon followed by delayed cooling due to the presence of an additional heat source that kept a large portion of the moon molten until 4 34 ga or 3 late accretion of the moon followed by rapid cooling of the magma ocean late in solar system history neither density driven overturn of the mantle nor a large impact are likely to homogenize the mantle and crust to the extent required by the sm nd isochron likewise secondary heating mechanisms such as tidal heating or radioactive decay are not efficient enough to keep the moon molten to the depth of the mare basalt source regions for many tens to hundreds of millions of years instead the age of equilibrium between such a compositionally diverse set of rocks produced on a global scale likely records the time of primordial solidification of the moon from a magma ocean this scenario accounts for both the petrogenetic characteristics of lunar rock suites as well as their sm nd isotopic systematics it is supported by the preponderance of 4 35 ga ages obtained for other hypothetical magma ocean crystallization products such as ferroan anorthosite suite rocks and k ree and p enriched cumulates that are thought to represent flotation cumulates of the magma ocean and the last vestiges of magma ocean solidification respectively

the timeline of the lunar bombardment revisited abstract the timeline of the lunar bombardment in the first gy of solar system history remains unclear basin forming impacts e g imbrium orientale occurred 3 9 3 7 gy ago i e 600 800 my after the formation of the moon itself many other basins formed before imbrium but their exact ages are not precisely known there is an intense debate between two possible interpretations of the data in the cataclysm scenario there was a surge in the impact rate approximately at the time of imbrium formation while in the accretion tail scenario the lunar bombardment declined since the era of planet formation and the latest basins formed in its tail end here we revisit the work of morbidelli et al 2012 that examined which scenario could be compatible with both the lunar crater record in the 3 4 gy period and the abundance of highly siderophile elements hse in the lunar mantle we use updated numerical simulations of the fluxes of asteroids comets and planetesimals leftover from the planet formation process under the traditional assumption that the hses track the total amount of material accreted by the moon since its formation we conclude that only the cataclysm scenario can explain the data the cataclysm should have started 3 95 gy ago however we also consider the possibility that hses are sequestered from the mantle of a planet during magma ocean crystallization due to iron sulfide exsolution o neil 1991 rubie et al 2016 we show that this is likely true also for the moon if mantle overturn is taken into account based on the hypothesis that the lunar magma ocean crystallized about 100 150 my after moon formation elkins tanton et al 2011 and therefore that hses accumulated in the lunar mantle only after this timespan we show that the bombardment in the 3 4 gy period can be explained in the accretion tail scenario this hypothesis would also explain why the moon appears so depleted in hses relative to the earth we also extend our analysis of the cataclysm and accretion tail scenarios to the case of mars the accretion tail scenario requires a global resurfacing event on mars 4 4 gy ago possibly associated with the formation of the borealis basin and it is consistent with the hse budget of the planet moreover it implies that the noachian and pre noachian terrains are 200 my older than usually considered

solar modulation of cosmogenic nuclide production over the last millennium comparison between 14c and 10be records for about the last 30 years it has been recognized that the high frequency component of the tree rings 14c 12c record is dominated by the modulation of the cosmic ray flux by the solar wind in particular it has been demonstrated that the three most recent periods of low sunspot occurrence were characterized by high values of atmospheric 14c 12c during the last millennium other periods of high 14c 12c values were observed but their solar origin is still debatable in the present work we compare these fluctuations with an independent record of cosmogenic 10be measured in ice from the south pole to check the solar origin of the observed 14c 12c variations in order to compare quantitatively the results obtained on 10be and 14c it is necessary to take into account the different behaviour of these two cosmogenic isotopes and especially the damping effect of the carbon cycle in the case of 14c as an input to a 12 box numerical model we used the relative fluctuations of the 10be concentrations record measured in south pole ice and converted it into a synthetic 14c record we took into account the fact that 10be modulation is enhanced in polar regions due to the orientation of the geomagnetic field as expected the fluctuations of the modelled 14c record are much smaller a factor of 20 than those observed for the raw 10be record in addition the variations are smoother and shifted in time by a few decades the 10be based 14c variations closely resemble the 14c measurements obtained on tree rings r 0 81 in particular it is easy to identify periods of maximal 14c 12c which correspond to solar activity minima centred at about 1060 1320 wolf 1500 sporer 1690 maunder and 1820 dalton yr a d cross correlation calculations suggest that there is no significant lag between the 10be based 14c and the tree ring 14c records our study strongly suggests the dominance of the solar modulation on the cosmonuclide production variations during the last millennium

a synchronized dating of three greenland ice cores throughout the holocene as part of the effort to create the new greenland ice core chronology 2005 gicc05 a synchronized stratigraphical timescale for the holocene parts of the dye 3 grip and ngrip ice cores is made by using volcanic reference horizons in electri cal conductivity measurements to match the cores the main annual layer counting is carried out on the most suited records only exploit ing that the three ice cores have been drilled at locations with different climatic con ditions and differences in ice flow however supplemental counting on data from all cores has been performed between each set of reference horizons in order to verify the valid ity of the match after the verification the main dating is transferred to all records us ing the volcanic reference horizons as tie points an assessment of the mean annual layer thickness in each core section confirms that the new synchronized dating is consistent for all three cores the data used for the main annual layer counting of the past 7900 years are the dye 3 grip and ngrip stable isotope records as the high accumulation rate at the dye 3 drill site makes the seasonal cycle in the dye 3 stable isotopes very resistant to firn diffusion an effort has been made to extend the dye 3 holocene record the new syn chronized dating relies heavily on this record of 75 000 stable isotope samples the dat ing of the early holocene consists of an already established part of gicc05 for grip and ngrip which has now been transferred to the dye 3 core gicc05 dates the younger dryas termination as defined from deuterium excess to 11 703 b2k 130 years earlier than the previous grip dating

coherent isotope history of andean ice cores over the last century 1 isotope records from andean ice cores provide detailed and high resolution climate information on various time scales however the relationship between these valuable isotope records and local or regional climate remains poorly understood here we present results from two new drillings in bolivia from the illimani and the sajama ice caps all four high altitude isotope signals in the andes now available huascaran quelccaya illimani and sajama show near identical decadal variability in the 20th century comparison with general circulation model results and meteorological data suggest that the andean high altitude records are primarily controlled by precipitation variability over the amazon basin

geochronology of an apollo 16 clast provides evidence for a basin forming impact 4 3 billion years ago we examined lithic breccias from the apollo sample collection in order to identify ferroan anorthosite samples suitable for geochronology and better define the age relationships between rocks of the lunar highlands clast 3a is a previously unstudied noritic anorthosite from apollo 16 lithic breccia 60016 with textural evidence of slow subsolidus recrystallization we estimate a cooling rate of 10 c myr and calculate a pyroxene solvus temperature of 1 100 1 000 c pyroxene exsolution lamellae 1 3 m indicate that the last stage of cooling was rapid at 0 2 c year typical of rates observed in thick ejecta blankets we calculate concordant ages from the 147sm 143nd 146sm 142nd rb sr and ar ar isotopic systems of 4 302 28 4 296 39 53 4 275 38 and 4 311 31 ma respectively with a weighted average of 4 304 12 ma the closure temperature of the sm nd system is 855 14 c whereas the closure temperature of the ar ar system is 275 25 c cooling from 855 to 275 c at 10 c myr should result in an age difference between the two isotopic systems of 60 myr the concordant sm nd rb sr and ar ar ages imply that they record the time the rock was excavated by a large impact from the midcrust the ages clearly predate various late accretion scenarios in which an uptick in impacts at 3 8 ga is preceded by a period of relative quiescence between 4 4 and 4 1 ga and instead are consistent with decreasing accretion rates following the formation of the moon

fossil figure contribution to the lunar figure abstract the unusual shape of the moon given its present rotational and orbital state has been explained as due to a fossil figure preserving a record of remnant rotational and tidal deformation jeffreys h 1915 mem r astron soc 60 187 217 lambeck k pullan s 1980 phys earth planet interiors 22 29 35 garrick bethell i wisdom j zuber m t 2006 science 313 652 655 however previous studies assume infinite rigidity and ignore deformation due to changes in the rotational and orbital potentials as the moon evolves to the present state we interpret the global lunar figure with a physical model that takes into account this deformation although the moon deforms in response to rotational and orbital changes a fossil figure capable of explaining the observed figure can be preserved by an elastic lithosphere

thermal and chemical evolution of the terrestrial magma ocean abstract the earth is likely to have experienced a magma ocean stage during accretion thermal and chemical evolution of magma ocean is investigated based on a one dimensional two phase flow heat and mass transfer model differentiation at lower mantle pressure depends on the type of magma ocean and surrounding atmosphere if the magma ocean is formed by the blanketing effect of a solar type proto atmosphere extensive differentiation proceeds at lower mantle pressure if the magma ocean is formed by the blanketing effect of an impact induced steam atmosphere no differentiation at lower mantle pressure is likely if a very deep magma ocean is formed by a giant impact whether differentiation proceeds at lower mantle pressure or not depends on grain size viscosity of melt and or properties of a transient atmosphere on the contrary chemical differentiation likely proceeds at upper mantle pressure irrespective of magma ocean type a shallow magma ocean can remain for 100 200 my without any heating processes

climate variability during the last 1000 years inferred from andean ice cores a review of methodology and recent results abstract andean ice core investigations began approximately 30 years ago today 10 drilling sites from 0 to 52 s have been explored for paleoclimate reconstructions most of the ice cores reaching the bedrock cover the last 20 000 years with seasonal resolution over the last few centuries to the last 1000 years for the quelccaya site we discuss both the potential and the limitations of tropical ice cores as climate archives with regard to the collaborative effort to reconstruct past climate variations in south america over the last 1000 years we point out the uniqueness of south american ice cores due to their location at high altitude and also their two main limitations which are related to i the interpretation of certain proxies in terms of climate and ii the relatively poor dating when seasonal cycles are no longer resolved in addition we present an overview of the proxies that have been used so far to analyze tropical climate dynamics finally we discuss records of enso the little ice age and the 20th century decadal variability including the anthropogenic period which are all preserved in ice cores

understanding the origin and evolution of water in the moon through lunar sample studies a paradigm shift has recently occurred in our knowledge and understanding of water in the lunar interior this has transpired principally through continued analysis of returned lunar samples using modern analytical instrumentation while these recent studies have undoubtedly measured indigenous water in lunar samples they have also highlighted our current limitations and some future challenges that need to be overcome in order to fully understand the origin distribution and evolution of water in the lunar interior another exciting recent development in the field of lunar science has been the unambiguous detection of water or water ice on the surface of the moon through instruments flown on a number of orbiting spacecraft missions considered together sample based studies and those from orbit strongly suggest that the moon is not an anhydrous planetary body as previously believed new observations and measurements support the possibility of a wet lunar interior and the presence of distinct reservoirs of water on the lunar surface furthermore an approach combining measurements of water abundance in lunar samples and its hydrogen isotopic composition has proved to be of vital importance to fingerprint and elucidate processes and source s involved in giving rise to the lunar water inventory a number of sources are likely to have contributed to the water inventory of the moon ranging from primordial water to meteorite derived water ice through to the water formed during the reaction of solar wind hydrogen with the lunar soil perhaps two of the most striking findings from these recent studies are the revelation that at least some portions of the lunar interior are as water rich as some mid ocean ridge basalt source regions on earth and that the water in the earth and the moon probably share a common origin

hydrostatic interfaces in bodies with nonhydrostatic lithospheres below the lithospheres of the terrestrial planets dwarf planets and moons density interfaces adjust over geologic time to align with surfaces of constant gravitational potential it is well known that the shape of such hydrostatic surfaces is controlled by the pseudo rotational potential tidal potential and the induced potential of nonspherical density interfaces in the body when a lithosphere is present however additional gravitational terms must be considered that arise from for example surface relief and crustal thickness variations a first order formalism is presented for calculating the shape of hydrostatic density interfaces beneath the lithosphere when the gravity field and surface shape of the body are known using an arbitrary discretized density profile the shapes are obtained by solving a simple matrix equation as examples lithospheric gravity anomalies account for about 10 of the relief along hydrostatic interfaces in mars whereas for the moon the lithospheric gravity is the dominant contributor to the core shape spherical harmonic degree 1 mass anomalies in the lithosphere generate degree 1 relief along the core mantle boundary and for mars and the moon the core is offset from the center of mass of the body by about 90 m the moments of inertia of the core of these bodies are also misaligned with respect to the principal moments of the entire body an improved crustal thickness map of mars is constructed that accounts for gravity anomalies beneath the lithosphere and the consequences of core relief on the martian free core nutation are quantified plain language summary the shapes of the solid planets and moons are largely hydrostatic and are determined by their rotation rate if the body has gravity anomalies that arise from within a rigid lithosphere these will act to perturb the shape of hydrostatic density interfaces beneath the lithosphere such as the core mantle boundary we present a method to compute the shape of density interfaces beneath the lithosphere when the gravity field of the body is known as examples of our technique we compute the shape of the core mantle boundary for mars and the moon both of which are shown to have important contributions that arise from the lithosphere we also generate a new crustal thickness map that accounts for gravity anomalies generated beneath the lithosphere

the relative timing of lunar magma ocean solidification and the late heavy bombardment inferred from highly degraded impact basin structures the solidification of the lunar magma ocean lmo and formation of impact basins are important events that took place on the early moon the relative timing of these events however is poorly constrained the aim of this study is to constrain the formation ages of old impact basins based on inferences of their thermal state most proposed basins formed before pre nectarian pn 5 stage do not exhibit clear concentric features in either topography or gravity suggesting substantial viscous lateral flow in the crust recent geodetic measurements reveal that the lunar crust is thinner than previously estimated indicating that an extremely high crustal temperature is required for lateral flow to occur in this study we calculate lunar thermal evolution and viscoelastic deformation of basins and investigate the thermal state at the

a chemical model for generating the sources of mare basalts combined equilibrium and fractional crystallization of the lunar magmasphere abstract it is generally considered that mare basalts were generated by the melting of a cumulate mantle formed in an early moon wide magma ocean or magmasphere however the nature and chemistry of this cumulate mantle and the logistics of its origin have remained elusive extensive studies of terrestrial layered mafic intrusions over the past sixty years have emphasized the imperfection of fractional crystallization and attendant crystal crystal and crystal liquid separation in a convecting magma chamber crystal liquid and crystal crystal separations were similarly inefficient during evolution of the lunar magma ocean lmo allowing for the trapping of interstitial liquid and entrainment of a small proportion of less dense plagioclase into the denser mafic cumulate mush indeed petrography of lunar highlands samples demonstrates this for anorthosites with 1 10 olivine the residual liquid after 80 90 crystallization was very evolved in fact kreepy and even in small proportions 1 5 would have a noticeable effect on the trace element chemistry of melts generated from these cumulates this trapped residual liquid would elevate total ree abundances in the cumulate pile while synchronously deepening the already negative eu anomaly essentially this trapped liquid will make the cumulate more fertile for melting to generate both kreep basalt and mare basalt magmas plagioclase entrained in the mafic cumulate pile adds an essential al component to the high ti basalt source and will moderate the requisite negative eu anomaly in the cumulate early in the evolution of the lunar mantle when the lmo still was largely liquid it is likely that vigorous convection was an important factor in crystallization such convection would allow crystals to remain suspended and in equilibrium with the lmo liquid for relatively long periods of time this extended period of equilibrium crystallization would then have been followed by fractional crystallization once plagioclase became a liquidus phase and began to float to form the lunar highlands crust previous authors have proposed a three component model for the evolution of high ti mare basalt source regions this model includes kreep early olivine rich high mg cumulates and late ilmeniterich low mg cumulates in various proportions however we propose a model for high ti basalt parent magmas which is in accord with studies of terrestrial layered intrusions this model for the high ti source includes trapped instantaneous residual liquid tirl 1 3 and entrainment of a small 2 5 proportion of plagioclase into the late stage cumulate pile in order to account for both the observed al compositions and trace element characteristics of high ti mare basalts melting of this relatively shallow ilmenite and clinopyroxene bearing late stage cumulate can generate high ti mare basalt magmas furthermore we are in agreement with other workers that only through a process of nonmodal melting will the high ti values for the parent magmas be realized large scale convective overturn of the cumulate pile and mixing of kreep with early and late stage cumulates is not required however localized overturn of the upper tenth of the cumulate pile is likely and in fact required to achieve an appropriate major element balance for the high ti mare basalt source region

changes in continental and sea salt atmospheric loadings in central greenland during the most recent deglaciation model based estimates by fitting a very simple atmospheric impurity model to high resolution data on ice accumulation and contaminant fluxes in the gisp2 ice core we have estimated changes in the atmospheric concentrations of soluble major ions insoluble particulates and 10 be during the transition from glacial to holocene conditions for many species changes in concentration in the ice typically overestimate atmospheric changes and changes in flux to the ice typically underestimate atmospheric changes because times of increased atmospheric contaminant loading are also times of reduced snowfall the model interpolates between the flux and concentration records by explicitly allowing for wet and dry deposition processes compared to the warm preboreal that followed we estimate that the atmosphere over greenland sampled by snow accumulated during the younger dry as cold event contained on average four seven times the insoluble particulates and nearly seven times the soluble calcium derived from continental sources and about three times the sea salt but only slightly more cosmogenic 10 be

accumulation at south pole comparison of two 900 year records two 900 year records of annual accumulation at south pole are compared to evalu ate the origin and significance of observed variations despite difficulties establishing absolute timescales due to problems identifying annual layer markers the two records can be correlated with confidence after moderate smoothing this correlation shows that over the time period considered 1050 1956 a d no climatically significant changes in accumulation occurred in stead fluctuations preserved in the two cores reflect spatial variations in snow accumulation as sociated with nonuniform deposition induced by surface relief on the scale of several kilometers

10 be and delta 2 h in polar ice cores as a probe of the solar variability s influence on climate and discussion by using the technique of accelerator mass spectrometry it is now possible to measure detailed profiles of cosmogenic cosmic ray produced 10 be in polar ice cores recent work has demonstrated that these profiles contain information on solar activity via its influence on the intensity of galactic cosmic rays arriving in the earth s atmosphere it has been known for some time that as a result of temperature dependent fractionation effects the stable isotope profiles delta 2 o and delta 2 h in polar ice cores contain palaeoclimate information thus by comparing the 10 be and stable isotope profiles in the same ice core one can test the influence of solar variability on climate and this independent of possible uncertainties in the absolute chronology of the records we present here the results of such a comparison for two antarctic ice cores one from the south pole covering the past ca 1000 years and one from dome c covering the past ca 3000 years

very high k kreep rich clasts in the impact melt breccia of the lunar meteorite sau 169 new constraints on the last residue of the lunar magma ocean abstract in the impact melt breccia imb of sayh al uhaymir sau 169 the most kreep rich lunar meteorite to date gnos et al 2004 clasts of a new type of lithologies were discovered consisting of ca poor and ca rich pyroxenes 60 8 vol ba rich k feldspar 27 9 vol phosphates 5 6 vol nb rich ilmenite 4 0 vol zircon 1 2 vol and minor sulfide 0 6 vol these mafic lithic clasts are more enriched in kreep component 1500 ci than the host meteorite and are highly enriched in potassium they are referred to as very high k vhk kreep lithology and probably most close to the last residual liquid of the lunar magma ocean without significant dilution by other mg rich magmas the fine grained matrix of the sau 169 imb has very similar mineral chemistry to the vhk kreep lithology but contains abundant plagioclase with trace k feldspar the matrix shows decoupling of k from the reep like component however it cannot be simply interpreted by mixing the vhk kreep lithology with anorthosites which should have diluted the reep like component with the same proportion sims pb pb dating was conducted on zircons in various petrographic settings and with different crystal habits all analyses show a main age peak at 3921 3 ma and a smaller one at 4016 6 ma the main age peak is identical to the previous pb pb age by gnos et al 2006 and u pb age by liu et al 2009 dating the catastrophic shock event contributed to the formation of sau 169 imb the older ages are consistent with the previous report of an older bulk u pb age by kramers et al 2007 suggestive of presence of relict crystals in a few large zircon grains the vhk kreep clasts predated the fine grained matrix but have the same zircon pb pb ages as the latter within the analytical uncertainties plagioclase was converted to maskelynite whereas zircon was shocked to diaplectic glass probably by a second event at 2 8 ga however the identical zircon pb pb ages of the amorphous parts and the remained crystalline areas indicate no resetting of pb pb isotopes by the later shock metamorphism or there was another severe impact event postdated solidification of the fine grained matrix within a few million years

differentiation of the south pole aitken basin impact melt sheet implications for lunar exploration we modeled the differentiation of the south pole aitken spa impact melt sheet to determine whether noritic lithologies observed within spa formed as a result of the impact results indicate differentiation of spa impact melt can produce noritic layers that may accommodate observed surface compositions but only in specific scenarios one of nine modeled impact melt compositions yielded layers of noritic materials that account for observations of noritic lithologies at depths of 6 km in this scenario impact occurred before a hypothesized lunar magma ocean cumulate overturn the 50 km deep melt sheet would have formed an insulating quenched layer at the surface before differentiating the uppermost differentiated layers in this scenario have feo and tio2 contents consistent with orbital observations if they were subsequently mixed with the uppermost quenched melt layer and with less feo and tio2 enriched materials such as ejecta emplaced during younger impacts these results verify that noritic lithologies observed within spa could have formed as a direct result of the impact therefore locations within spa that contain noritic materials represent potential destinations for collecting samples that can be analyzed to determine the age of the spa impact potential destinations include central peaks of bhabha bose finsen and antoniadi craters as well as walls of leibnitz and schrodinger basins additionally potential remnants of the uppermost quenched melt may be preserved in gabbroic material exposed in mafic mound exploring and sampling these locations can constrain the absolute age of spa a task that ranks among the highest priorities in lunar science

constraining the timing and sources of volcanism at the apollo 12 landing site using new pb isotopic compositions and crystallisation ages abstract the basaltic suites collected at the apollo 12 landing site have been interpreted as representing a stratigraphic sequence of volcanic flows emplaced in the oceanus procellarum region between approximately 3100 3300 ma this study presents secondary ion mass spectrometry sims pb isotopic analyses of samples from each of the basaltic suites which have been used to constrain precise crystallisation ages and initial pb isotopic compositions the new crystallisation ages are consistent with the three main basaltic suites olivine pigeonite and ilmenite being emplaced over a period of approximately 60 million years and the improved precision of these ages has made it possible to reinterpret the stratigraphic sequence of basalt flows underlying the apollo 12 landing site contrary to previous studies the three ilmenite basalts are determined as having the oldest ages with a weighted average of 3187 6 ma 2 and are therefore interpreted as representing the lowest unit in the sequence underlying the olivine and pigeonite basalts with an age range constrained by the oldest and youngest pigeonite basalts 3176 6 ma and 3129 10 ma 2 the initial pb isotopic compositions have been compared with recalculated initial sr and nd isotopic compositions and are consistent with the three main basaltic suites originating from magmatic sources that incorporated different proportions of a common primitive mafic cumulate and the residual trapped liquid fraction remaining after a majority of the lunar magma ocean had crystallised our data also demonstrate that the feldspathic basalt 12038 is unique both in terms of its crystallisation age 3242 13 ma and its derivation from a distinct mantle reservoir

spatial and temporal variability in the stable isotope systematics of modern precipitation in china implications for paleoclimate reconstructions the stable isotopic composition of materials such as glacial ice tree rings lake sediments and speleothems from low to mid latitudes contains information about past changes in temperature t and precipitation amount p however the transfer functions which link 18op to changes in t or p d 18op dt and d 18op dp can exhibit significant temporal and spatial variability in these regions in areas affected by the southeast asian monsoon past variations in 18o and d of precipitation have been attributed to variations in monsoon intensity storm tracks and or variations in temperature proper interpretation of past 18op variations here requires an understanding of these complicated stable isotope systematics since temperature and precipitation are positively correlated in china and have opposite effects on 18op it is necessary to determine which of these effects is dominant for a specific region in order to perform even qualitative paleoclimate reconstructions here we evaluate the value of the transfer functions in modern precipitation to more accurately interpret the paleorecord the strength of these transfer functions in china is investigated using multiple regression analysis of data from 10 sites within the global network for isotopes in precipitation gnip 18op is modeled as a function of both temperature and precipitation the magnitude and signs of the transfer functions at any given site are closely related to the degree of summer monsoon influence 18op values at sites with intense summer monsoon precipitation are more dependent on the amount of precipitation than on temperature and therefore exhibit more negative values in the summer in contrast 18op values at sites that are unaffected by summer monsoon precipitation exhibit strong relationships between 18op and temperature the sites that are near the northern limit of the summer monsoon exhibit dependence on both temperature and amount of precipitation comparison with simple linear models 18op as a function of t or p and a geographic model 18op as a function of latitude and altitude shows that the multiple regression model is more successful at reproducing 18op values at sites that are strongly influenced by the summer monsoon the fact that the transfer function values are highly spatially variable and closely related to the degree of summer monsoon influence suggests that these values may also vary temporally since the southeast asian monsoon intensity is known to exhibit large variations on a number of timescales annual to glacial interglacial and the magnitude and sign of the transfer functions is related to monsoon intensity we suggest that as monsoon intensity changes the magnitude and possibly even the sign of the transfer functions may vary therefore quantitative paleoclimate reconstructions based on 18op variations may not be valid