apollo 16 regolith breccias characterization and evidence for early formation in the mega regolith all of the apollo 16 regolith breccias 8 specimens have been characterized in terms of their petrography grain size distribution porosity major and trace element composition noble gas contents and ferromagnetie resonance properties these breccias vary signkqcantly with respect to their density and porosity with the more dense breccias showing significant shock damage the regolith breccias resemble the soils in grain size distribution and in the relative proportions of major petrological components except agglutinates many of the breecias are compositionally different from the apollo 16 soils in that they lack an important marie component present in the soils although some groupings occur the petrologic and chemical compositions of the regolith breedas do not correlate with the station location of the samples all but one of the breceias show some evidence of irradiation at the lunar surface solar gases measurable fmr agglutinates and analyses made on grain size separates from two disaggregated breedas indicate that this irradiation occurred before compaction when the breccia material was finely disseminated on the surface however the concentrations of surface irradiation parameters solar gases fmr agglutinates for most breedas are far less than seen in any lunar soils or in regolith breccias from other apollo missions several breedas also contain unusually high trapped 4oar 36ar ratios of 8 12 and a significant fission xe component in excess of that expected from in situ production these observations suggest that the surface irradiation of these breedas occurred as early as 4 x 109 years ago we conclude that most of the apollo 16 regolith breedas were not formed from any known apollo 16 soil they appear to be well comminuted material that contains ancient regolith developed during the late stage heavy bombardment of the moon when large impacts were much more common relative to small impacts so that regoliths did not have time to significantly mature before being diluted by fresh ejecta and buffed this ancient megaregolith is significantly different from more recent lunar regolith but may be similar to asteroidal regoliths from which some brecciated meteorites have formed

new views of lunar geoscience an introduction and overview beyond the earth the moon is the only planetary body for which we have samples from known locations the analysis of these samples gives us ground truth for numerous remote sensing studies of the physical and chemical properties of the moon and they are invaluable for our fundamental understanding of lunar origin and evolution prior to the return of the apollo 11 samples the moon was thought by many to be a primitive undifferentiated body e g urey 1966 a concept shattered by the data returned from the apollo and luna missions ever since new data have helped to address some of our questions but of course they also produced new questions in this chapter we provide a summary of knowledge about lunar geologic processes and we describe major scientific advancements of the last decade that are mainly related to the most recent lunar missions such as galileo clementine and lunar prospector 1 1 the moon in the planetary context compared to terrestrial planets the moon is unique in terms of its bulk density its size and its origin fig 1 1a c all of which have profound effects on its thermal evolution and the formation of a secondary crust fig 1 1d numerous planetary scientists considered the moon as an endmember among the planetary bodies in our solar system because its lithosphere has been relatively cool rigid and intact throughout most of geological time a one plate planet and its surface has not been affected by plate recycling an atmosphere water or life therefore the moon recorded and preserved evidence for geologic processes that were active over the last 4 4 5 b y and offers us the unique opportunity to look back into geologic times for which evidence on earth has long been erased fig 1 1c d impact cratering an exterior process is considered the most important surface process on the moon internal

modeling the provenance of the apollo 16 regolith 1 the regolith at the apollo 16 landing site the only apollo landing site in the central lunar highlands contains material derived from a number of sources a model that accounts for the introduction of basin ejecta and mixing of the megaregolith is used to estimate the abundance of basin material in the apollo 16 regolith megaregolith mixing model estimates of the abundance of primary ejecta from the imbrium serenitatis and nectaris basins are found to be present in roughly equal 8 10 proportions additionally the presence of mare derived material in the apollo 16 regolith suggests that a significant component of the regolith 15 23 is derived from lateral transport there are inherent difficulties in directly comparing model results with ground truth at apollo 16 results suggest shallower mixing during ejecta emplacement than predicted by oberbeck et al 1975

geochemistry of grain size fractions of luna 24 soil comments on the lunar regolith chemistry and petrology of luna 24 grain size fractions by j c laul o d rode s b simon and j j papike

major lunar crustal terranes surface expressions and crust mantle origins in light of global remotely sensed data the igneous crust of the moon can no longer be viewed as a simple globally stratified cumulus structure composed of a flotation upper crust of anorthosite underlain by progressively more mafic rocks and a residual melt kreep sandwich horizon near the base of the lower crust instead global geochemical information derived from clementine multispectral data and lunar prospector gamma ray data reveals at least three distinct provinces whose geochemistry and petrologic history make them geologically unique 1 the procellarum kreep terrane pkt 2 the feldspathic high lands terrane fht and 3 the south pole aitken terrane spat the pkt is a mafic province coincident with the largely resurfaced area in the procellarum imbrium region whose petrogenesis relates to the early differentiation of the moon here some 40 of the th in the moon s crust is concentrated into a region that constitutes only about 10 of the crustal volume this concentration of th average 5 ppm and by implication the other heat producing elements u and k led to a fundamentally different thermal and igneous evolution within this region compared to other parts of the lunar crust lower crustal materials within the pkt likely interacted with underlying mantle materials to produce hybrid magmatism leading to the magnesian suite of lunar rocks and possibly kreep basalt although rare in the apollo sample collection widespread mare volcanic rocks having substantial th enrichment are indicated by the remote data and may reflect further interaction between enriched crustal residues and mantle sources the fht is characterized by a central anorthositic region that constitutes the remnant of an anorthositic craton resulting from early lunar differentiation basin impacts into this region do not excavate significantly more mafic material suggesting a thickness of tens of kilometers of anorthositic crust the feldspathic lunar meteorites may represent samples from the anorthositic central region of the fht ejecta from deep penetrating basin impacts outside of the central anorthositic region however indicate an increasingly mafic composition with depth the spat a mafic anomaly of great magnitude may include material of the upper mantle as well as lower crust thus it is designated a separate terrane whether the spa basin impact simply uncovered lower crust such as we infer for the fht remains to be determined

seismic stratigraphic record of the amundsen sea embayment shelf from pre glacial to recent times evidence for a dynamic west antarctic ice sheet studies of the sedimentary architecture and characteristics of the antarctic continental margin provide clues about past ice sheet advance retreat cycles and help improve constraints for paleo ice dynamic models since early glacial periods a first seismostratigraphic analysis of the amundsen sea embayment shelf and slope of west antarctica reveals insights into the structural architecture of the continental margin and shows stages of sediment deposition erosion and transport reflecting the history from pre glacial times to early glaciation and to the late pleistocene glacial interglacial cycles the shelf geometry consists of a large pre and syn rift basin in the middle shelf region between basement cropping out on the inner shelf and buried basement ridge and highs on the outer shelf a subordinate basin within the large basin on the mid shelf may be associated with motion along an early west antarctic rift system branch at least 4 km of pre glacial strata have been eroded from the present inner shelf and coastal hinterland by glacial processes six major sedimentary units ass 1 to ass 6 separated by five major erosional unconformities ass u1 to ass u5 are distinguished from bottom to top unconformity ass u4 results from a major truncational event by glacial advance to the middle and outer shelf which was followed by several episodes of glacial advance and retreat as observed from smaller scale truncational unconformities within the units above ass u4 some of the eroded sediments were deposited as a progradional wedge that extends the outer shelf by 25 to 65 km oceanward of the pre glacial shelf break we compare the observed seismic characteristics with those of other antarctic shelf sequences and assign an early cretaceous age to bottom sedimentary unit ass 1 a late cretaceous to oligocene age to unit ass 2 an early to mid miocene age to unit ass 3 a mid miocene age to unit ass 4 a late miocene to early pliocene age to unit ass 5 and a pliocene to pleistocene age to the top unit ass 6 buried grounding zone wedges in the upper part of unit ass 5 on the outer shelf suggest pronounced warming phases and ice sheet retreats during the early pliocene as observed for the ross sea shelf and predicted by paleo ice sheet models our data also reveal that on the middle and outer shelf the flow path of the pine island thwaites paleo ice stream system has remained stationary in the central pine island trough since the earliest glacial advances which is different from the ross sea shelf where glacial troughs shifted more dynamically this study and its stratigraphic constraints will serve as a basis for future drilling operations required for an improved understanding of processes and mechanisms leading to change in the west antarctic ice sheet such as the contemporary thinning and grounding line retreat in the amundsen sea drainage sector

geological record of ice shelf break up and grounding line retreat pine island bay west antarctica the catastrophic break ups of the floating larsen a and b ice shelves antarctica in 1995 and 2002 and associated acceleration of glaciers that flowed into these ice shelves were among the most dramatic glaciological events observed in historical time this raises a question about the larger west antarctic ice shelves do these shelves with their much greater glacial discharge have a history of collapse here we describe features from the seafloor in pine island bay west antarctica which we interpret as having been formed during a massive ice shelf break up and associated grounding line retreat this evidence exists in the form of seafloor landforms that we argue were produced daily as a consequence of tidally influenced motion of mega icebergs maintained upright in an iceberg armada produced from the disintegrating ice shelf and retreating grounding line the break up occurred prior to ca 12 ka and was likely a response to rapid sea level rise or ocean warming at that time

high resolution measurements of absolute thorium abundances on the lunar surface the lunar prospector lp gamma ray spectrometer grs has been used to map the global abundance of thorium on the lunar surface a global map of absolute thorium abundances on a 2 by 2 equal area pixel scale is presented using new detector modeling results and low altitude lp data because thorium is relatively abundant in kreep rich material these data provide fundamental information regarding the locations and importance of terranes that are rich in kreep bearing materials

bedform signature of a west antarctic palaeo ice stream reveals a multi temporal record of flow and substrate control abstract the presence of a complex bedform arrangement on the sea floor of the continental shelf in the western amundsen sea embayment west antarctica indicates a multi temporal record of flow related to the activity of one or more ice streams in the past mapping and division of the bedforms into distinct landform assemblages reveals their time transgressive history which implies that bedforms can neither be considered part of a single downflow continuum nor a direct proxy for palaeo ice velocity as suggested previously a main control on the bedform imprint is the geology of the shelf which is divided broadly between rough bedrock on the inner shelf and smooth dipping sedimentary strata on the middle to outer shelf inner shelf bedform variability is well preserved revealing information about local complex basal ice conditions meltwater flow and ice dynamics over time these details which are not apparent at the scale of regional morphological studies indicate that past ice streams flowed across the entire shelf at times and often had onset zones that lay within the interior of the antarctic ice sheet today in contrast highly elongated subglacial bedforms on sedimentary strata of the middle to outer shelf represent a timeslice snapshot of the last activity of ice stream flow and may be a truer representation of fast palaeo ice flow in these locations a revised model for ice streams on the shelf captures complicated multi temporal bedform patterns associated with an antarctic palaeo ice stream for the first time and confirms a strong substrate control on a major ice stream system that drained the west antarctic ice sheet during the late quaternary

the case for an imbrium origin of the apollo thorium rich impact melt breccias abstract mafic th rich impact melt breccias most of which are identified with the composition known as low k fra mauro lkfm are the most common rock type in the nonmare regoliths of the apollo lunar landing sites the origin of mafic impact melt breccias bears on many lunar problems the nature of the late meteoroid bombardment cataclysm the spatial distribution of kreep both near the surface and at depth the ages of the major basins and the composition of the early crust of the nearside lunar highlands thus it is crucial that the origin of mafic impact melt breccias be accurately understood because of both intra and intersite differences in compositions of mafic impact melt breccia samples apparent differences in crystallization age and differences in siderophile element ratios previous studies have argued that either 1 most mafic impact melt breccias are the products of several large craters local to the site at which they were found but that some are of basin origin or that 2 they are all from the imbrium apollos 14 and 15 nectaris apollo 16 and serenitatis apollo 17 basins here we reconsider the hypothesis that virtually all of the th rich mafic impact melt breccias from the apollo missions are products of the imbrium impact ejecta deposit modeling based on modern crater scaling indicates that the imbrium event produced ejecta deposits that average hundreds of meters thick or more at all apollo highland sites which is thicker than some previous estimates substantial amounts of imbrium ejecta should have been sampled at every apollo highland site we suggest that the mafic impact melt breccias may be the principal form of those ejecta the imbrium projectile impacted into th rich material that we regard as part of a unique mafic lunar geochemical province we call the high th oval region based on the surface distribution of th only basins within the high th oval region excavated th rich material the th concentrations of the highlands as observed by the apollo orbiting ray experiments are consistent with the estimates from ejecta modeling of the younger basin forming impacts only imbrium was large enough to produce the copious amount of melt required by the ubiquitous presence of mafic impact melt breccias in the apollo sampled regolith the high th oval region still may have been molten or hot at shallow depths 4 ga ago when the imbrium projectile struck we reason that compositional heterogeneity of ejected melt breccia is to be expected under these circumstances we argue that siderophile element fingerprints of mafic impact melt breccias are not inconsistent with production of all common types by a single projectile we suggest that the narrow range of ages of 3 7 4 0 ga for all successfully dated mafic impact melt breccias may reflect a single event whose age is difficult to measure precisely rather than a number of discrete impact events closely spaced in time such that reported age variations among mafic impact melt breccias reflect the ability to measure 40ar 39ar ages with greater precision than the accuracy with which measured portions of mafic impact melt breccias have recorded the time of their formation

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

on lateral mixing efficiency of lunar regolith 1 to reexamine the potential for lateral mixing over large distances 100 km by impact craters a mathematical model utilizing the stable probability distribution is proposed for estimating lateral mixing efficiency on the moon the proposed model divides material mixing into shallow slope and steep slope regimes mixing in the shallow slope regime conforms to the condition that the exponent of the power law describing lunar crater size frequency is larger than the exponent of the power law describing the rim thickness plus 2 otherwise the mixing is called the steep slope regime the model suggests that in the shallow slope regime lateral mixing on the moon is efficient enough to deliver 20 30 exotic components over distances greater than 100 km e g highland material to the mare the model indicates that lateral mixing conforming to the steep slope regime is not efficient if linear addition of ejecta deposits is assumed because in this regime impact cratering is driven by small craters reworking lunar surface and the addition of crater ejecta is an invalid assumption if the result of the proposed model for the shallow slope regime is applied to regolith layers below the reworked zone a significant number of exotic components is predicted

subglacial bedforms reveal complex basal regime in a zone of paleo ice stream convergence amundsen sea embayment west antarctica the flow of ice streams which account for most discharge from large ice sheets is controlled by processes operating at the ice stream bed data from modern ice stream beds are difficult to obtain but where ice advanced onto continental shelves during glacial periods extensive areas of the former bed can be imaged using modern swath sonar tools we present new multibeam swath bathymetry data analyzed alongside sparse preexisting data from the amundsen sea embayment the compilation is the most extensive continuous area of multi beam data coverage yet obtained on the inner continental shelf of antarctica the data reveal streamlined subglacial bedforms that define a zone of paleo ice stream convergence but in contrast to previous models do not show a simple downflow progression of bedform types along paleo ice stream troughs we interpret high spatial variability of bedforms as indicating a complex mechanical and hydrodynamic regime at the former ice stream beds consistent with observations from some modern ice streams we conclude that care must be taken when using bedforms to infer paleo ice stream velocities

a revised algorithm for calculating tio2 from clementine uvvis data a synthesis of rock soil and remotely sensed tio2 concentrations 1 investigating mare basalt compositions at both the sample and remote sensing level for the apollo and luna mare sites reveals the need for a more complex regression procedure than previously proposed in order to extract accurate tio2 concentrations from clementine spectral reflectance csr data the tio2 algorithm of lucey and coworkers is modified by using two different sets of regression parameters to relate measured regolith compositions from sampling locations to the csr properties of these sites one regression trend fits the majority of apollo data and the second regression is a fit to the apollo 11 luna 16 and luna 24 data which were considered to be anomalous in previous tio2 calibrations these three sites have unusually low albedo compared to other mare landing sites and some 32 of nearside mare regions appear to share this characteristic possible reasons for these differences related to proximity of the other sites to mare highland boundaries are discussed using the dual regression method we find 1 that tio2 concentrations calculated for the basaltic landing sites faithfully reproduce a bimodal distribution as seen in the sample data 2 that when coupled with the effects of other thermal neutron absorbers ti concentrations are more consistent with observed epithermal to thermal neutron flux ratios than are previous clementine based derivations of tio2 for basaltic regions and 3 that basalts of intermediate tio2 concentrations occur most frequently in the oceanus procellarum region and that these intermediate concentrations appear to be inherent to the flows underlying the regolith and presumably to the basalt source regions

compositional variations of the lunar crust results from radiative transfer modeling of central peak spectra 1 we present model mineralogy of impact crater central peaks combined with crustal thickness and crater central peak depth of origin models to report multiple perspectives of lunar crustal composition with depth here we report the analyses of 55 impact crater central peaks and how their compositions directly relate to the lunar highlands sample suite a radiative transfer model is used to analyze clementine visible plus near infrared spectra to place compositional constraints on these central peak materials central peaks analyzed are dominantly magnesian and plagioclase poor strong compositional similarities to lunar mg suite materials are evident relative to crustal thickness estimates central peak mineralogy becomes more plagioclase rich as the crust thickens relative to the crust mantle boundary the origin of peaks with dominantly mafic mineralogy are confined to the lower crust and primarily within the south pole aitken and procellarum kreep terranes pkt additionally central peaks with anorthositic mineralogy 60 vol plagioclase are transported to the surface from all depths in the crustal column and confined to the feldspathic highlands terrane fht the discovery of mafic and magnesian materials consistent with mg suite rocks of the sample collection in all lunar terranes suggests that the process and sources that give rise to these types of rocks is not unique to the pkt and not necessarily dependent on incompatible elements for formation the identification of ferroan and magnesian anorthositic material near the crust mantle boundary of the fht is also inconsistent with an increasing mafic feldspar ratio and mg with depth in the crust

lunar surface geochemistry global concentrations of th k and feo as derived from lunar prospector and clementine data abstract accurate estimates of global concentrations of th k and feo have an important bearing on understanding the bulk chemistry and geologic evolution of the moon we present empirical ground truth calibrations transformations for lunar prospector gamma ray spectrometer data k and th and a modified algorithm for deriving feo concentrations from clementine spectral reflectance data that incorporates an adjustment for tio 2 content the average composition of soil samples for individual landing sites is used as ground truth for remotely sensed data among the apollo and luna sites apollo 12 and 14 provide controls for the incompatible element rich compositions apollo 16 and luna 20 provide controls for the feldspathic and incompatible element poor compositions and apollo 11 15 and 17 and luna 16 and 24 provide controls for fe rich compositions in addition to these apollo and luna sample data we include the composition of the feldspathic lunar meteorites as a proxy for the northern farside highlands to extend the range of the calibration points thus providing an additional anorthositic end member composition these empirical ground truth calibrations for lunar prospector th and k provide self consistency between the existing derived data and lunar sample data clementine spectral reflectance data are used to construct a tio 2 sensitive feo calibration that yields higher feo concentrations in areas of high fe low ti mare basalt rich surfaces than previous feo algorithms the data set so derived is consistent with known sample compositions and regolith mixing relationships

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

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

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

pristine lunar glasses criteria data and implications major element analyses of several thousand glasses from all of the apollo landing sites have resulted in the identification of 25 groups of pristine i e volcanic glass the nickel in these pristine glasses is shown to be indigenous not meteoritic contamination and to be correlated with mg the chemical data indicate that these glasses are consistently better candidates for primary magmas than the majority of crystalline mare basalts the pristine glasses support the view that assimilative processes ringwood and kesson 1976 involving two cumulate systems in the differentiated mantle operated during mare petrogenesis the reality of those assimilative interactions is evident by the occurrence of two linear arrays among the chemistries of the glasses data suggest that these cumulate components in the differentiated mantle persist for lateral distances of at least 1000 km and therefore appear to be products of a vast magma ocean that existed early in lunar history alternative hypotheses claiming that the highlands crust and mare source regions were produced by serial magmatism without a magma ocean have not yet considered all of the constraints derived from the pristine glasses

pleistocene collapse of the west antarctic ice sheet some glacial sediment samples recovered from beneath the west antarctic ice sheet at ice stream b contain quaternary diatoms and up to 108 atoms of beryllium 10 per gram other samples contain no quaternary diatoms and only background levels of beryllium 10 less than 10 6 atoms per gram the occurrence of young diatoms and high concentrations of beryllium 10 beneath grounded ice indicates that the ross embayment was an open marine environment after a late pleistocene collapse of the marine ice sheet

subglacial bathymetry and sediment distribution beneath pine island glacier ice shelf modeled using aerogravity and in situ geophysical data new results pine island glacier pig in the amundsen sea sector of the west antarctic ice sheet wais is losing mass and contributing to global sea level rise at an accelerating rate although recent observations and modeling have identified the incursion of relatively warm circumpolar deep water cdw beneath the pig ice shelf pigis as the main driver of this ice mass loss the lack of precise bathymetry limits furthering our understanding of the ice ocean interactions and improving the accuracy of modeling here we present updated bathymetry and sediment distribution beneath the pigis modeled by the inversion of aerogravity data with constraints from active source seismic data observations from an autonomous underwater vehicle and the regional gravity anomaly field derived from satellite gravity observations modeled bathymetry shows a submarine ridge beneath the middle of pigis that rises 350 to 400 m above the surrounding sea floor with a minimum water column thickness of 200 m above it this submarine ridge continues across the whole width of the 45 km wide ice shelf with no deep troughs crossing it confirming the general features of the previously predicted sub ice shelf ocean circulation however the relatively low resolution of the aerogravity data and limitations in our inversion method leave a possibility that there is an undetected few kilometers wide or narrower trough that may alter the predicted sub ice shelf ocean circulation modeled sediment distribution indicates a sedimentary basin of up to 800 m thick near the current grounding zone of the main pig trunk and extending farther inland and a region seaward of the submarine ridge where sediments are thin or absent with exposed crystalline basement that extends seaward into pine island bay therefore the submarine ridge marks the transition from a thick sedimentary basin providing a smooth interface over which ice could flow easily by sliding or sediment deformation to a region with no to little sediments and instead a rough interface over which ice flows mainly by deformation we hypothesize that the post last glacial maximum retreat of pig stabilized at this location because of the spatial transition in basal conditions this in turn supports the hypothesis that the recent retreat of pig was strongly forced probably by changes in ocean circulation rather than occurring because of ongoing response to the end of the ice age or other changes inland of or beneath pig

ascent and eruption of a lunar high titanium magma as inferred from the petrology of the 74001 2 drill core abstract an analysis of the orange glasses and crystallized beads from the 68 cm deep 74001 2 core has been conducted to understand the processes occurring during ascent and eruption of the apollo 17 orange glass magma equilibrium between melt and metal blebs fe85ni14co1 within the core along with cr contents in olivine phenocrysts suggest there was an oxidation of c and a reduction of the melt at an o fugacity of iw 1 3 and 1320 c to form co gas at 200 bars or 4 km depth this was followed by development of more oxidized conditions during ascent also during ascent there was formation of euhedral homogeneous fo81 olivine crystals and spinel crystals with higher al and mg contents than the smaller spinels in the crystallized beads both the metal blebs and al rich spinels were trapped inside the fo81 olivine phenocrysts as they grew prior to eruption the composition of the orange glasses are homogeneous throughout the core except for a few distinct glasses at the top that appear to have been mixed in by micrometeorite reworking a few glassy melt inclusions of orange glass composition trapped in the fo81 phenocrysts contain 600 100 ppm s and 50 ppm cl compared to the 200 ppm s and 50 ppm cl in the orange glass melt when quenched these inclusions therefore document the addition of 400 ppm s to the co rich volcanic gas during the eruption the size and distribution of different volcanic beads in the apollo 17 deposit indicate a mode of eruption in which the orange glasses and partially crystallized beads formed further away from the volcanic vent where cooling rates were faster progressively larger and more numerous crystals in the black beads reflect slower cooling rates at higher optical densities in the volcanic plume the development of a brown texture in the orange glasses at the bottom of the core where the black beads dominate is interpreted to result from devitrification by subsolidus heating either as the orange glasses fell back through the hot plume or after deposition on the surface the change from domination by orange glasses to black beads in the core probably reflects a decrease in gas content over time which consequently would increase the plume optical density and favor slower cooling rates

laboratory spectroscopic detection of hydration in pristine lunar regolith abstract reflectance spectroscopy of apollo lunar soil samples curated in an air and water free sealed environment since recovery and return to earth has been carried out under water oxygen co 2 and organic controlled conditions spectra of these pristine samples contain features near 3 m wavelength similar to those observed from the lunar surface by the chandrayaan 1 moon mineralogy mapper m 3 cassini visual and infrared mapping spectrometer vims and deep impact extrasolar planet observation and deep impact extended investigation epoxi high resolution instrument hri instruments spectral feature characteristics and inferred oh h 2 o concentrations are within the range of those observed by spacecraft instruments these findings confirm that the 3 m feature from the lunar surface results from the presence of hydration in the form of bound oh and h 2 o implantation of solar wind h appears to be the most plausible formation mechanism for most of the observed lunar oh and h 2 o

the origin and evolution of lunar high ti basalts periodic melting of a single source at mare tranquillitatis abstract five groups of basalts a b1 b2 b3 d with three principal ages exist at the apollo 11 site these range from the low k low rare earth element ree groups b1 b2 and b3 to the low k high ree group d basalts to the high k high ree group a basalts the group a basalts are the only high k 0 2 wt k2o basalts and youngest with an age of 3 59 02 ga groups b3 and b1 are 3 71 02 and 3 67 02 ga respectively group b2 basalts are the oldest at 3 85 02 ga group d basalts have not been dated fractionation modelling for major and trace elements indicates that the b1 basalts could have formed from a b3 like parent liquid the b2 and d basalts can also be related to liquids similar to the b3 b1 composition through the presence of varying amounts of modal whitlockite thus the entirety of low k high ti basalts at apollo 11 may have formed through melting of the same source region the group a basalt compositions are consistent with formation from a different parent liquid with the composition of apollo 11 orange glass modelling of major and trace elements in the apollo 11 orange glass indicate that the composition of the group a basalts is consistent with fractionation of this glass coupled with some assimilation 7 5 15 of an evolved kreep like material however this component is much younger than primitive kreep 4 4 ga this neukreep component similar to the composition of quartz monzodiorites described from the apollo 15 site probably represents evolved material formed during plutonism prior to the formation of the apollo 11 orange glass liquid

testing the relation between uv vis color and tio2 content of the lunar maria reflectance spectroscopy is important for placing lunar samples into a regional and global geologic context to this end the ultraviolet visible uv vis color ratio used to estimate the tio2 composition of mature mare basalts has been one of the most widely used spectral parameters in lunar exploration we examine the correlation between uv vis color and tio2 content using a combination of clementine lunar prospector and sample data to document the extent to which color is dependent upon tio2 examination of the remotely sensed data reveals that the correlation between uv vis ratio and tio2 composition is best represented by a sigmoidal trend rather than the canonical linear or curvilinear correlation with this information we are then able to evaluate between two models that propose different explanations for the relationship between uv vis color and tio2 the first model attributes the correlation between tio2 and uv vis color to spectrally neutral opaques i e ilmenite while the other emphasizes the effect of fe ti charge transfer in lunar glasses and dual scattering mechanisms between high and low ti basalts we do not find evidence in the spectral data to support the occurrence of fe ti charge transfer in lunar glass as the principal cause for color in high ti basalts the data also do not substantiate the existence of different scattering mechanisms e g volume v surface scattering between high and low tio2 basalts instead our analyses substantiate that the spectral effects of ilmenite exhibit a major influence over the uv vis ratio by including sample data we find that in addition to ilemenite tio2 content factors such as feo content ilmenite grain size modal abundance of plagioclase and the olivine to pyroxene ratio in a mare soils can influence the uv vis continuum these findings point to promising avenues of research that future uv vis spectral techniques can exploit in order to yield more accurate tio2 estimates and potentially additional petrologic information

a new look at the apollo 11 regolith and kreep although the apollo 11 mission landed in mare tranquillitatis 50 km from the nearest exposure of highlands small nonmare particles are conspicuous in the regolith the nonmare portion of the apollo 11 regolith is compositionally similar to the apollo 16 regolith at both sites most of the nonmare material is from the feldspathic highlands but some is mafic impact melt breccia with the chemical signature known as kreep for its high concentrations of k rare earth elements and p the composition of the apollo 11 regolith corresponds best to a mixture of 66 crystalline mare basalt 5 orange volcanic glass 20 material of the feldspathic highlands 8 kreep bearing impact melt breccia and 1 meteoritic material the volcanic glass and kreep bearing melt breccia components account for the high concentrations of mg and cr in the regolith the most kreep rich sample known from apollo 11 10085 1187 is an impact melt breccia that bears a strong textural and compositional similarity to a unique apollo 16 melt breccia 64815 although not of the maria such breccias are also not of the highlands provenance global data obtained from orbit show that kreep bearing materials are most common at low elevations in the imbrium procellarum region and are rare at high elevations thus as at apollo 16 the kreep bearing breccias of apollo 11 are probably ejecta from the imbrium impact into the low lying procellarum kreep terrane on the basis of these observation and others we suggest that the general acceptance of kreep as a material of the highlands is not supported by the data and results largely from historical accident

grounding line retreat of the west antarctic ice sheet from inner pine island bay ice loss from the marine based potentially unstable west antarctic ice sheet wais contributes to current sea level rise and may raise sea level by 3 3 m or even 5 m in the future over the past few decades glaciers draining the wais into the amundsen sea embayment ase have shown accelerated ice flow rapid thinning and fast retreat of the grounding line gl however the long term context of this ice loss is poorly constrained limiting our ability to accurately predict future wais behavior here we present a new chronology for wais retreat from the inner continental shelf of the eastern ase based on radiocarbon dates from three marine sediment cores the ages document a retreat of the gl to within 100 km of its modern position before ca 10 000 calibrated cal yr b p this early deglaciation is consistent with ages for gl retreat from the western ase our new data demonstrate that in contrast to the ross sea wais retreat from the ase shelf was largely complete by the start of the holocene our results further suggest either slow gl retreat from the inner ase shelf throughout the holocene or that any episodes of fast gl retreat must have been short lived thus today s rapid retreat may be exceptional during the holocene and may originate in recent changes in regional climate ocean circulation or ice sheet dynamics

palaeo ice stream pathways and retreat style in the easternmost amundsen sea embayment west antarctica revealed by combined multibeam bathymetric and seismic data multibeam swath bathymetry data sets collected over the past two decades have been compiled to identify palaeo ice stream pathways in the easternmost amundsen sea embayment we mapped 3000 glacial landforms to reconstruct ice flow in the 250 km long cross shelf abbot trough this bathymetric feature was occupied by a large ice stream which was fed by two tributaries cosgrove and abbot and reached the continental shelf edge during the last maximum ice sheet advance geomorphological mapping has enabled a clear differentiation between subglacial landforms indicating warm e g megascale glacial lineations and cold based e g hill hole pairs ice conditions on the continental shelf during the last glaciation grounding zone wedges and recessional moraines mapped within the palaeo ice stream troughs and on adjacent sea floor highs referred to as inter ice stream ridges indicate grounding line stillstands or re advances of the west antarctic ice sheet during the last deglaciation of the shelf we observe that the locations of grounding zone wedges coincide with trough constrictions as well as local topographic highs of harder substrate this combination of trough bottlenecks and local pinning points on an otherwise retrograde slope is likely to have modified the pace of grounding line retreat causing the grounding zone to pause and deposit grounding zone wedges the episodic retreat recorded within abbot trough corresponds to post glacial episodic retreat interpreted for the neighbouring pine island thwaites palaeo ice stream trough thus suggesting a uniform pattern of retreat across the eastern amundsen sea embayment locally indications are strong that a change in basal thermal regime of the ice from warm to cold based conditions occurred prior to final retreat as hill hole pairs overprint megascale glacial lineations further the correlation of grounding zone wedges with geological boundaries emphasises the influence of subglacial geology on ice stream flow our new geomorphological map of the easternmost amundsen sea embayment resolves the pathways of palaeo ice streams that were probably all active during the last maximum extent of the ice sheet and the extent of adjacent inter ice stream ridges it reveals information about the style of and the basal thermal regime during the subsequent grounding line retreat such information provides an important empirical framework by which the accuracy of ice sheet models can be gauged

carbon and oxygen isotope composition of nautilus macromphalus a record of thermocline waters off new caledonia abstract this study investigates the controls on the stable isotope composition of shell nacreous layer of a modern nautilus macromphalus from new caledonia closely spaced samples were taken both along growth lines isochrons and growth axis time series carbon isotope compositions 13 c 0 3 to 1 pdb of the shell decrease in the domains of maximal growth 0 3 and muscle insertion 0 4 maximal 13 c variations of about 1 are recorded in time series a global ontogenetic decrease of 13 c values is observed for both dorsal and ventral areas 0 4 to 0 8 and can be ascribed to a metabolic effect with age or to changes in the food source by contrast oxygen isotope compositions are quite constant 1 1 18 o

flow and retreat of the late quaternary pine island thwaites palaeo ice stream west antarctica multibeam swath bathymetry and sub bottom profiler data are used to establish constraints on the flow and retreat history of a major palaeo ice stream that carried the combined discharge from the parts of the west antarctic ice sheet now occupied by the pine island and thwaites glacier basins sets of highly elongated bedforms show that at the last glacial maximum the route of the pine island thwaites palaeo ice stream arced north northeast following a prominent cross shelf trough in this area the grounding line advanced to within similar to 68 km of and probably reached the shelf edge minimum ice thickness is estimated at 715 m on the outer shelf and we estimate a minimum ice discharge of similar to 108 km 3 yr 1 assuming velocities similar to today s pine island glacier similar to 2 5 km yr 1 additional bed forms observed in a trough northwest of pine island bay likely formed via diachronous ice flows across the outer shelf and demonstrate switching ice stream behavior the style of ice retreat is also evident in five grounding zone wedges which suggest episodic deglaciation characterized by halts in grounding line migration up trough stillstands occurred in association with changes in ice bed gradient and phases of inferred rapid retreat correlate to higher bed slopes supporting theoretical studies that show bed geometry as a control on ice margin recession however estimates that individual wedges could have formed within several centuries still imply a relatively rapid overall retreat our findings show that the ice stream channeled a substantial fraction of west antarctica s discharge in the past just as the pine island and thwaites glaciers do today

topography of the moon from the clementine lidar range measurements from the lidar instrument carried aboard the clementine spacecraft have been used to produce an accurate global topographic model of the moon this paper discusses the function of the lidar the acquisition processing and filtering of observations to produce a global topographic model and the determination of parameters that define the fundamental shape of the moon our topographic model a 72nd degree and order spherical harmonic expansion of lunar radii is designated goddard lunar topography model 2 gltm 2 this topographic field has an absolute vertical accuracy of approximately 100 m and a spatial resolution of 2 5 the field shows that the moon can be described as a sphere with maximum positive and negative deviations of 8 km both occurring on the farside in the areas of the korolev and south pole aitken s p aitken basins the amplitude spectrum of the topography shows more power at longer wavelengths as compared to previous models owing to more complete sampling of the surface particularly the farside a comparison of elevations derived from the clementine lidar to control point elevations from the apollo laser altimeters indicates that measured relative topographic heights generally agree to within 200 m over the maria while the major axis of the lunar gravity field is aligned in the earth moon direction the major axis of topography is displaced from this line by approximately 10 to the east and intersects the farside 24 north of the equator the magnitude of impact basin topography is greater than the lunar flattening 2 km and equatorial ellipticity 800 m which imposes a significant challenge to interpreting the lunar figure the floors of mare basins are shown to lie close to an equipotential surface while the floors of unflooded large basins except for s p aitken lie above this equipotential the radii of basin floors are thus consistent with a hydrostatic mechanism for the absence of significant farside maria except for s p aitken whose depth and lack of mare require significant internal compositional and or thermal heterogeneity a macroscale surface roughness map shows that roughness at length scales of 10 1 10 2 km correlates with elevation and surface age

lithological variation with depth and decoupling of maturity parameters in apollo 16 regolith core 68001 2 using ferromagnetic resonance fmr and instrumental neutron activation analysis inaa we have determined the maturity surface exposure parameter zjfeo and concentrations of twenty five chemical elements on samples taken every half centimeter down the 61 cm length of the 68001 2 regolith core double drive tube collected at station 8 on the apollo 16 mission to the moon contrary to premission expectations no ejecta or other influence from south ray crater is evident in the core although a small inflection in the fe0 profile at 3 cm depth may be related the south ray crater impact regolith maturity generally decreases with depth as in several previously studied cores we recognize five compositionally distinct units in the core which we designate a through e although all are similar in composition to each other and to other soils from the cayley plains at the apollo 16 site unit a o 33 cm is mature to submature throughout zjfeo 89 34 units and is indistinguishable in composition from surface soils collected at station 8 unit b 33 37 cm is enriched slightly in a component of anorthositic norite composition unit d 42 53 cm is compositionally equivalent to 80 wt unit a soil plus 20 wt apollo 16 type dimict breccia consisting of subequal parts anorthosite and impact melt breccia compared to unit a unit e 53 61 cm contains a small proportion up to 4 of some component compositionally similar to apollo 14 sample 14321 unit c 37 42 cm is unusual for lithophile and siderophile elements it is similar to units a and d however fe0 is low throughout the unit 30 units and in a bluish gray zone at 41 cm depth zjfeo drops to 1 6 units the lowest value that we have observed in several hundred apollo 16 soil samples samples from the bluish gray zone also have low zn concentrations lo pg g compared to 20 30 pg g for the rest of the core although both values are consistent with fragmented rock material that has received virtually no surface exposure the abundance of agglutinates in the bluish gray soil of unit c is moderately high typical of a submature soil that would ordinarily have zjfeo 30 we believe that the anomalously low values of zjfeo and zn concentration result because the soil was heated to 8oo 1000 c probably during an impact this temperature range is sufficient to volatize the surface correlated zn and agglomerate the nanophase metal giving rise to the fmr signal but is not great enough to sinter the soil alternatively the unusual soil interval may represent a disaggregated or incipient regolith breccia although there is no significant difference in the texture or clast matrix relationships between unit c and adjacent units copyright 0 1997 elsevier science ltd

chemistry of the apollo 11 highland component chemical data 28 major minor and trace elements were obtained by instrumental neutron activation analysis inaa for 38 hand picked highland fragments 1 20 mg from coarse fines 10085 the apollo 11 highland chemical groups are represented by a range of petrographic types six major chemical highland groups are identified in the apollo 11 fragments these are 1 high k kreep 2 anorthosite e g 15415 60015 with 10 chondrite rare earth elements ree abundances a positive eu anomaly anorthosite with 30 chondrite abundances and a positive eu anomaly 3 anorthosite norite troctolite ant 67075 4 low k fra mauro lkfm 77135 5 anorthositic gabbro 68415 with no eu anomaly anorthositic gabbro 65055 67955 with a positive eu anomaly and anorthositic gabbro 68516 60015 with a negative eu anomaly and 6 apollo 11 dominant highland component 2 10 chondrite ree abundances with a positive 10 14 chondrite eu anomaly there are three newly recognized groups in the apollo 11 highland suite based on the ree patterns these are a ant with 5 chondrite la 22 chondrite abundances and a positive eu anomaly b 10 chondrite flat pattern with 14 chondrite positive eu anomaly and c 2 3 chondrite flat pattern with 10 chondrite positive eu anomaly the apollo 11 highland suite is very low in potassium non kreepy overall the apollo 11 highland suite is quite similar to the apollo 16 suite most previously recognized highland chemical groups are represented in the apollo 11 highland component

mixing levels the apennine front soil component and compositional trends in the apollo 15 soils variations in concentrations of lithophile elements in samples of apollo 15 soil can be explained in terms of only four chemical components three components are represented by extrusive rock types found at the apollo 15 site mare basalt kreep basalt and the pyroclastic green glass associated with breccia 15426 the fourth component the highlands component can be represented by soil from the apennine front particularly the soil obtained from the 55 57 cm depth interval of station 2 core 15007 8 among samples of apennine front soil this one appears to be the least contaminated by mare materials and may be our most typical sample of the apennine front highlands although soil fron the apennine front is itself a complex mixture of many types of highlands rocks it behaves as a single component with respect to mixing with the other three rock type components the various subcomponents of the apennine front soil e g melt rock and anorthositic norite that have been used in some mixing models are not required as discrete components in order to explain the compositional variation among samples of apollo 15 soil most of this compositional variation results from mare highlands mixing i e apennine front soil with mare basalt kreep basalt which probably derives from local possibly unexposed sources is also a variable component of the soil and is most prevalent in the soil from stations lm 6 and 9

post lgm deglaciation in pine island bay west antarctica abstract to date understanding of ice sheet retreat within pine island bay pib following the last glacial maximum lgm was based on seven radiocarbon dates and only fragmentary seafloor geomorphic evidence during the austral summer 2009 2010 restricted sea ice cover allowed for the collection of 27 sediment cores from the outer pib trough region combining these cores with data from prior cruises over 133 cores have been used to conduct a detailed sedimentological facies analysis these results augmented by 23 new radiocarbon dates are used to reconstruct the post lgm deglacial history of pib our results record a clear retreat stratigraphy in pib composed of from top to base terrigenous sandy silt distal glacimarine pebbly sandy mud ice proximal glacimarine and till initial retreat from the outer continental shelf began shortly after the lgm and before 16 4 k cal yr bp as a likely response to rising sea level bedforms in outer pib document episodic retreat in the form of back stepping grounding zone wedges and are associated with proximal glacimarine sediments a sub ice shelf facies is observed in central pib and spans 12 3 10 6 k cal yr bp it is possible that widespread impingement of warm water onto the continental shelf caused an abrupt and widespread change from sub ice shelf sedimentation to distal glacimarine sedimentation dominated by widespread dispersal of terrigenous silt between 7 8 and 7 0 k cal yr bp the final phase of retreat ended before 1 3 k cal yr bp when the grounding line migrated to a location near the current ice margin

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

deglacial history of the west antarctic ice sheet in the western amundsen sea embayment abstract the amundsen sea embayment ase drains approximately 35 of the west antarctic ice sheet wais and is one of the most rapidly changing parts of the cryosphere in order to predict future ice sheet behaviour modellers require long term records of ice sheet melting to constrain and build confidence in their simulations here we present detailed marine geological and radiocarbon data along three palaeo ice stream tributary troughs in the western ase to establish vital information on the timing of deglaciation of the wais since the last glacial maximum lgm we have undertaken multi proxy analyses of the cores core description shear strength x radiographs magnetic susceptibility wet bulk density total organic carbon nitrogen carbonate content and clay mineral analyses in order to 1 characterise the sedimentological facies and depositional environments and 2 identify the horizon s in each core that would yield the most reliable age for deglaciation in accordance with previous studies we identify three key facies which offer the most reliable stratigraphies for dating deglaciation by recording the transition from a grounded ice sheet to open marine environments these facies are i subglacial ii proximal grounding line and iii seasonal open marine in addition we incorporate ages from other facies e g glaciomarine diamictons deposited at some distance from the grounding line such as glaciogenic debris flows and iceberg rafted diamictons and turbates into our deglacial model in total we have dated 78 samples mainly the acid insoluble organic aio fraction but also calcareous foraminifers which include 63 downcore and 15 surface samples through careful sample selection prior to dating we have established a robust deglacial chronology for this sector of the wais our data show that deglaciation of the western ase was probably underway as early as 22 351 calibrated years before present cal yr bp reaching the mid shelf by 13 837 cal yr bp and the inner shelf to within c 10 12 km of the present ice shelf front between 12 618 and 10 072 cal yr bp the deglacial steps in the western ase broadly coincide with the rapid rises in sea level associated with global meltwater pulses 1a and 1b although given the potential dating uncertainty additional more precise ages are required before these findings can be fully substantiated finally we show that the rate of ice sheet retreat increased across the deep up to1600 m basins of the inner shelf highlighting the importance of reverse slope and pinning points in accelerated phases of deglaciation

the procellarum kreep terrane implications for mare volcanism and lunar evolution geophysical remote sensing and sample data demonstrate that the procellarum and imbrium regions of the moon make up a unique geochemical crustal province here dubbed the procellarum kreep terrane geochemical studies of imbrium s ejecta and the crustal structure of the imbrium and serenitatis basins both suggest that a large portion of the lunar crust in this locale is composed of a material similar in composition to apollo 15 kreep basalt kreep basalt has about 300 times more uranium and thorium than chondrites so this implies that a large portion of moon s heat producing elements is located within this single crustal province the spatial distribution of mare volcanism closely parallels the confines of the procellarum kreep terrane and this suggests a causal relationship between the two phenomena we have modeled the moon s thermal evolution using a simple thermal conduction model and show that as a result of the high abundance of heat producing elements that are found in the procellarum kreep terrane partial melting of the underlying mantle is an inevitable outcome specifically by placing a 10 km kreep basalt layer at the base of the crust there our model predicts that mare volcanism should span most of the moon s history and that the depth of melting should increase with time to a maximum depth of about 600 km we suggest that the 500 km seismic discontinuity that is observed in the apollo seismic data may represent this maximum depth of melting our model also predicts that the kreep basalt layer should remain partially molten for a few billion years thus the imbrium impact event most likely excavated into a partially molten kreep basalt magma chamber we postulate that the kreep basalt composition is a by product of mixing urkreep with shallow partial melts of the underlying mantle since mg suite rocks are likely derived from crystallizing kreep basalt the provenance of these plutonic rocks is likely to be unique to this region of the moon

crater ejecta scaling laws fundamental forms based on dimensional analysis a model of crater ejecta is constructed using dimensional analysis and a recently developed theory of energy and momentum coupling in cratering events general relations are derived that provide a rationale for scaling laboratory measurements of ejecta to larger events specific expressions are presented for ejection velocities and ejecta blanket profiles in two limiting regimes of crater formation the so called gravity and strength regimes in the gravity regime ejecta velocities at geometrically similar launch points within craters vary as the square root of the product of crater radius and gravity this relation implies geometric similarity of ejecta blankets that is the thickness of an ejecta blanket as a function of distance from the crater center is the same for all sizes of craters if the thickness and range are expressed in terms of crater radii in the strength regime ejecta velocities are independent of crater size consequently ejecta blankets are not geometrically similar in this regime for points away from the crater rim the expressions for ejecta velocities and thickness take the form of power laws the exponents in these power laws are functions of an exponent that appears in crater radius scaling relations thus experimental studies of the dependence of crater radius on impact conditions determine scaling relations for ejecta predicted ejection velocities and ejecta blanket profiles based on measured values of are compared to existing measurements of velocities and debris profiles

compositional and lithological diversity among brecciated lunar meteorites of intermediate iron concentration we present new compositional data for 30 lunar stones representing about 19 meteorites most have iron concentrations intermediate to those of the numerous feldspathic lunar meteorites 3 7 feo and the basaltic lunar meteorites 17 23 feo all but one are polymict breccias some as implied by their intermediate composition are mainly mixtures of brecciated anorthosite and mare basalt with low concentrations of incompatible elements such as sm 1 3 g g these breccias likely originate from points on the moon where mare basalt has mixed with material of the fht feldspathic highlands terrane others however are not anorthosite basalt mixtures three 17 75 g g sm consist mainly of nonmare mafic material from the nearside pkt procellarum kreep terrane and a few are ternary mixtures of material from the fht pkt and maria some contain mafic nonmare lithologies like anorthositic norites norites gabbronorites and troctolite these breccias are largely unlike breccias of the apollo collection in that they are poor in sm as well as highly feldspathic anorthosite such as that common at the apollo 16 site several have high th sm compared to apollo breccias dhofar 961 which is olivine gabbronoritic and moderately rich in sm has lower eu sm than apollo samples of similar sm concentration this difference indicates that the carrier of rare earth elements is not kreep as known from the apollo missions on the basis of our present knowledge from remote sensing among lunar meteorites dhofar 961 is the one most likely to have originated from south pole aitken basin on the lunar far side

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

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

mebo70 seabed drilling on a polar continental shelf operational report and lessons from drilling in the amundsen sea embayment of west antarctica a multibarrel seabed drill rig was used for the first time to drill unconsolidated sediments and consolidated sedimentary rocks from an antarctic shelf with core recoveries between 7 and 76 we deployed the marum mebo70 drill device at nine drill sites in the amundsen sea embayment three sites were located on the inner shelf of pine island bay from which soft sediments presumably deposited at high sedimentation rates in isolated small basins were recovered from drill depths of up to 36 m below seafloor six sites were located on the middle shelf of the eastern and western embayment drilling at five of these sites recovered consolidated sediments and sedimentary rocks from dipping strata spanning ages from cretaceous to miocene this report describes the initial coring results the challenges posed by drifting icebergs and sea ice and technical issues related to deployment of the mebo70 we also present recommendations for similar future drilling campaigns on polar continental shelves

petrology of the apollo 11 highland component new data for 38 highland fragments hand picked from apollo 11 coarse fines are reported petrographic mineralogic and bulk chemical data show that 1 the apollo 11 highland component is non kreepy and like that of apollo 16 2 poikilitic rocks granulitic breccias and the anorthosite norite troctolite suite are the most abundant rock types followed by polymict breccias and glasses 3 both the ferroan anorthosite and mg rich plutonic suites are represented in the apollo 11 highland component 4 except for one sample the intermediate k fra mauro and high k fra mauro groups are not represented the data and observations are consistent with local derivation of the highland material from beneath relatively thin basalt flows and addition to the regolith via vertical mixing

small area thorium features on the lunar surface 1 using an improved understanding of the lunar prospector gamma ray spectrometer lp grs spatial footprint we have derived a new map of global thorium abundances on the lunar surface this map has a full width half maximum spatial resolution of 80 km 2 and is mapped on the lunar surface using 0 5 0 5 pixels this map has allowed the identification and classification of 42 small area 3 g g in southwestern mare tranquillitatis near the apollo 11 landing site with our better understanding of the lp grs spatial footprint we have been able to constrain the surface thorium abundance at the compton belkovich thorium anomaly to 40 55 g g which is higher than any other measured location on the lunar surface and higher than most samples finally using 1 km pixel feo abundances from clementine and lp grs spatial footprint information we have been able to obtain plausible thorium distributions around kepler crater at a resolution of 1 km pixel the materials around kepler crater appear to be a relatively simple mixing of thorium rich mib compositions and high thorium mare basalts

the great lunar hot spot and the composition and origin of the apollo mafic lkfm impact melt breccias thorium rich mafic impact melt breccias from the apollo 14 17 missions that is those breccias identified with the composition known as lkfm are regarded largely as products of basin forming impacts that penetrated the feldspathic crust and sampled underlying mafic material and magma ocean residuum carrying the compositional signature of kreep potassium rare earth elements phosphorous despite considerable compositional variation among such breccias compositions of all of them correspond to mixtures of only four components 1 a norite with composition generally similar to that of apollo 15 basalt mean abundance 58 range 30 95 2 fo 90 dunite mean 13 range 1 27 3 feldspathic upper crust mean 29 range 4 50 and feni metal 0 1 1 7 petrographic evidence has shown that much of the feldspathic component but none of the kreep component is clastic this observation and the high proportion of kreep norite component in the breccias suggest that the melt zone of the impact or impacts forming the breccias contained little feldspathic material but consisted predominantly of material with the average composition of kreep norite the dunite component probably derives ultimately from the upper mantle these conclusions support the hypothesis that the breccias were not formed in typical feldspathic crust but instead by one or more impacts into what is designated here the great lunar hot spot that is the anomalous th rich terrane in the imbrium procellarum area identified by the apollo and lunar prospector gamma ray spectrometers the lkfm composition is a special product of the great lunar hot spot and is not the average composition of the lower crust in typical feldspathic highlands similarly mg suite and alkali suite plutonic rocks of the apollo collection are likely all differentiation products of the hot spot not of plutons that might occur in typical feldspathic crust

the international bathymetric chart of the southern ocean ibcso version 1 0 a new bathymetric compilation covering circum antarctic waters the international bathymetric chart of the southern ocean ibcso version 1 0 is a new digital bathymetric model dbm portraying the seafloor of the circum antarctic waters south of 60 degrees s

basaltic magmatism on the moon a perspective from volcanic picritic glass beads abstract it is widely accepted that basaltic magmas are products of partial fusion of periodotite within planetary mantles as such they provide valuable insights into the composition structure and processes of planetary interiors those compositions which approach primary melt compositions provide the most direct information about planetary interiors and serve as a starting point to understand basaltic evolution within the collection of lunar samples returned by the apollo and luna missions are homogeneous picritic glass beads of volcanic origin these picritic glasses are our closest approximations to primary magmas as such these glass beads provide a unique perspective concerning the origin of mare basalts the characteristics of the lunar interior and processes in the early differentiation of the moon we have obtained trace element data for these picritic glasses using sims techniques these data and literature isotopic and experimental data on the picritic glasses are placed within the framework of mare basaltic magmatism the volcanic glasses are very diverse in their trace element characteristics for example they have a wide range of ree pattern shapes and concentrations like the crystalline mare basalts all picritic glasses have a negative eu anomaly unlike the crystalline mare basalts there is little correlation between the size of the eu anomaly and overall ree concentrations trace element differences among the various glasses suggests that a kreep component was incorporated into their mantle source this implies large scale mixing of the lunar magma ocean derived cumulate pile subtle differences among glasses suggest that local mixing of sources may also have been an important process preservation of subtle chemical differences in the picritic glasses and crystalline basalts may be interpreted as indicating that they were produced by small to moderate degrees of partial melting and that the lunar mantle did not experience extensive melting during episodes of mare volcanism several lines of evidence are consistent with the view that the picritic glasses were derived from mantle sources that were compositionally distinct from the sources for crystalline mare basalts these are parallel but no common liquid lines of descent chemical differences between picritic glasses and the more primitive crystalline mare basalts experimental studies indicating that the picritic glasses are multiply saturated at depths greater than that of the mare basalts differences in lead isotopic data and the mode of eruption i e fire fountaining for glass beads these data also provide circumstantial evidence that suggests that the picritic glasses were derived from a source somewhat more volatile rich than that of the mare basalts several petrogenetic models are suggested by the trace element characteristics of the picritic glasses 1 1 partial melting of heterogeneous lunar mantle at depths greater than 300 km to produce the parental magmas picritic for both the mare basalts and picritic glasses picritic magmas represented by glass beads were erupted to the surface with small degrees of fractional crystallization while mare basalts were produced by larger degrees of fractional crystallization 15 30 of similar but not identical picritic magmas 2 2 picritic magmas represented by the glass beads were generated at depths greater than 400 km in a volatile enriched relative to the mare basalt source heterogeneous mantle while mare basalts are fractional crystallization products of picritic magmas generated at depths of less than 400 km 3 3 the picritic magmas represented by the glass beads represent polybaric melting that initiated at depths of at least 1000 km a primitive mantle component or less processed cumulate mantle components may have been involved in the generation of the picritic glasses in any of these models

apollo 16 site geology and impact melts implications for the geologic history of the lunar highlands the geology of the apollo 16 site is reconsidered on the basis of data from photogeology geochemical remote sensing and lunar samples the site possesses an upper surface of anorthositic gabbro and related rocks mafic components were deposited as basin ejecta the events involved in its geological evolution were the nectaris impact and the imbrium impact the role of large local craters in the history of the region was to serve as topographic depressions to accumulate basin ejecta the most abundant melt composition at apollo 16 is an aluminous variety of lkfm basalt supplied by the nectaris impact as ejected basin impact melt the mafic lkfm melt may have been supplied by the imbrium impact more aluminous melt groups are probably derived from local small craters the remainder of the deposits in the region are composed of anorthositic clastic debris derived from the nectaris basin the local crustal substrate and imbrium and other basins

mare tranquillitatis basalt emplacement history and relation to lunar samples galileo and clementine multispectral data of the mare tranquillitatis region have been analyzed to investigate the stratigraphy of basaltic units and the effects of lateral and vertical mixing processes within the mare the distribution of compositionally distinct mare units is observed to be correlated with previous uv vis ratio images although estimates of soil titanium contents are low in some areas as a result of mixing of local basalts with nonmare feldspathic materials basalt units identified by their spectral properties and spectral mixture analysis are compared with groups of apollo 11 samples defined by previous workers on the basis of age and chemistry spectral studies presented here indicate that the apollo 11 site lies at the edge of a localized western mare unit which includes the youngest and most titanium rich basalts in tranquillitatis apollo 11 high k high ti samples in southern tranquillitatis these basalts have been contaminated by a large degree of mixing with nonmare feldspathic materials nonmare materials near the apollo 11 site are attributed largely to crater rays from theophilus 100 km in diameter which is located approximately 300 km to the south a more extensive and stratigraphically older unit exposed near apollo 11 is related to the low k high ti apollo 11 samples and appears to extend as a coherent surface unit as far north as the apollo 17 site in southern serenitatis the distribution of this spectrally identified basalt unit supports petrologic and geochemical evidence for the grouping of the high ti low k apollo 11 and 17 basalt samples into the same regional volcanic events multispectral analysis of tranquillitatis deposits also identify low titanium basalts in the northeastern and southeastern portions of the basin that are older than the high ti basalts and are believed to be unsampled by apollo 11 several lines of evidence suggest that the cayley formation along the western tranquillitatis margin may indeed lie on top of an ancient mare deposit buried by imbrium basin ejecta e g a cryptomare deposit the distribution of vertically excavated feldspathic premare material within the mare provides information on the depth of the mare units and the proximity of the underlying basin topography compositional stratigraphy observed in both sets of multispectral data supports an asymmetric premare fill basin topography containing thicker basalts in the northwestern portion of the basin than previously predicted by crater flooding data

the imbrium impact event and the thorium distribution at the lunar highlands surface late in the moon s heavy bombardment period the impact that formed the imbrium basin excavated and melted a tremendous volume of material that was subsequently distributed over most of the moon s surface the apollo orbiting ray experiments metzger et al 1977 show that the imbrium projectile struck in a th rich area called the high th oval region here and regarded as a unique lunar geochemical province imbrium primary ejecta were thus probably rich in th it is shown here using ejecta deposit modeling that the distribution of th in the highlands surface along the ground tracks of the ray spectrometers is consistent with the distribution expected for imbrium ejecta deposits deep basins other than imbrium appear to have excavated regions of lower crust that were mafic and fe bearing but not th rich the possibility that the surface th distribution arises mainly from imbrium ejecta has implications for the nature of the moon s igneous differentiation and the nature of the proposed cataclysm or late bombardment with large meteoroids

glaciomarine sedimentation dynamics of the abbot glacial trough of the amundsen sea embayment shelf west antarctica sedimentary sequences of the continental shelf of the eastern amundsen sea embayment in west antarctica represent records of past outlet glaciers and ice streams the former flow of ice streams was channelled through glacial troughs which now form large bathymetric depressions we therefore selected one of the largest troughs the abbot glacial trough in the outer shelf to analyse its glacial depositional and erosional history based on horizon stratigraphy derived from seismic data several basement highs channellized the delivery of sediment and controlled the grounded ice sheet in early glacial periods both pre glacial and full glacial seismic facies were identified glacially transported and deposited sediments extended the shelf break by 75 km from the pre glacial shelf edge the main abbot glacial trough contains sediment from confluent ice flows of the pine island thwaites cosgrove and abbot glacier systems as well as smaller contributions from local ice streams emanating from thurston island sherman island of peacock sound played an important role in the dynamics of the abbot glacier by dividing the ice flow into two ice streams which interfered with the main glacial sediment transport paths from the south this study contributes to an understanding of the formation of the amundsen sea shelf and the extent of past ice sheet advances

antarctic ice sheet loss driven by basal melting of ice shelves accurate prediction of global sea level rise requires that we understand the cause of recent widespread and intensifying glacier acceleration along antarctic ice sheet coastal margins atmospheric and oceanic forcing have the potential to reduce the thickness and extent of floating ice shelves potentially limiting their ability to buttress the flow of grounded tributary glaciers indeed recent ice shelf collapse led to retreat and acceleration of several glaciers on the antarctic peninsula but the extent and magnitude of ice shelf thickness change the underlying causes of such change and its link to glacier flow rate are so poorly understood that its future impact on the ice sheets cannot yet be predicted here we use satellite laser altimetry and modelling of the surface firn layer to reveal the circum antarctic pattern of ice shelf thinning through increased basal melt we deduce that this increased melt is the primary control of antarctic ice sheet loss through a reduction in buttressing of the adjacent ice sheet leading to accelerated glacier flow the highest thinning rates occur where warm water at depth can access thick ice shelves via submarine troughs crossing the continental shelf wind forcing could explain the dominant patterns of both basal melting and the surface melting and collapse of antarctic ice shelves through ocean upwelling in the amundsen and bellingshausen seas and atmospheric warming on the antarctic peninsula this implies that climate forcing through changing winds influences antarctic ice sheet mass balance and hence global sea level on annual to decadal timescales

cretaceous and early tertiary climates of antarctica evidence from fossil wood abstract fossil wood is abundant in cretaceous and early tertiary sediments of the northern antarctic peninsula region the wood represents the remains of vegetation that once grew in high palaeolatitudes when the polar regions were warmer during former greenhouse climates fossil wood is a unique data store of palaeoclimate information analyses of growth rings and anatomical characters in fossil wood provide important information about temperature rainfall seasonality and climate trends for this time period in antarctica climate signals from fossil wood supported by sedimentary and geochemical evidence indicate a trend of cool climates during the early cretaceous followed by peak warmth during the coniacian to early campanian narrower growth rings suggest that the climate cooled during the maastrichtian and palaeocene cool wet and possibly seasonal climates prevailed at this time with tentatively estimated mean annual temperatures mats falling from 7 c to 4 8 c respectively determined from dicotyledonous dicot wood anatomy the late palaeocene early eocene was once again warm with estimated mats of 7 15 c from dicot wood analysis but conditions subsequently deteriorated through the latter part of the eocene when cold seasonal climates developed ultimately leading to the onset of cenozoic ice sheets and the elimination of vegetation from most of antarctica

lunar iron and titanium abundance algorithms based on final processing of clementine ultraviolet visible images the clementine mission to the moon returned global imaging data collected by the ultraviolet visible uvvis camera this data set is now in a final state of calibration and a five band multispectral digital image model dim of the lunar surface will soon be available to the science community we have used observations of the lunar sample return sites and stations extracted from the final dim in conjunction with compositional information for returned lunar soils to revise our previously published algorithms for the spectral determination of the feo and tio2 content of the lunar surface the algorithms successfully normalize the effects of space weathering so that composition may be determined without regard to a surface s state of maturity these algorithms permit anyone with access to the standard archived dim to construct high spatial resolution maps of feo and tio2 abundance such maps will be of great utility in a variety of lunar geologic studies

reconstruction of the west antarctic ice sheet in pine island bay during the last glacial maximum and its subsequent retreat history abstract marine geological and geophysical studies were conducted to determine the late quaternary glacial history of the west antarctic ice sheet in pine island bay antarctica the data set includes sea floor imagery in the form of multibeam swath bathymetry and deep tow side scan sonar surveys distribution of sedimentary deposits and basal surface conditions are revealed through intermediate resolution seismic data and chirp 3 5 khz sub bottom profiles sedimentary deposits were sampled with piston cores and calcareous material was dated using ams radiocarbon techniques results from the study indicate the ice sheet was grounded on the outer shelf during its maximum extent sometime in the past thick ice flowing slowly and resting on crystalline bedrock was influenced by significant amounts of subglacial meltwater on the inner shelf thinner but more rapidly flowing ice characterized the seaward extent of the ice sheet which was grounded on a sedimentary substrate deglaciation occurred in two phases beginning soon after the last glacial maximum the outer most extension of the ice sheet retreated gradually pausing on a bathymetric high on the middle shelf by 16 000 14c years ago between 16 000 and 12 000 14c years ago ice sheet retreat resumed and may have proceeded rapidly to reach a present day position by 10 000 14c years ago

progressive cenozoic cooling and the demise of antarctica s last refugium the antarctic peninsula is considered to be the last region of antarctica to have been fully glaciated as a result of cenozoic climatic cooling as such it was likely the last refugium for plants and animals that had inhabited the continent since it separated from the gondwana supercontinent drill cores and seismic data acquired during two cruises shaldril i and ii in the northernmost peninsula region yield a record that when combined with existing data indicates progressive cooling and associated changes in terrestrial vegetation over the course of the past 37 million years mountain glaciation began in the latest eocene approximately 37 34 ma contemporaneous with glaciation elsewhere on the continent and a reduction in atmospheric co2 concentrations this climate cooling was accompanied by a decrease in diversity of the angiosperm dominated vegetation that inhabited the northern peninsula during the eocene a mosaic of southern beech and conifer dominated woodlands and tundra continued to occupy the region during the oligocene approximately 34 23 ma by the middle miocene approximately 16 11 6 ma localized pockets of limited tundra still existed at least until 12 8 ma the transition from temperate alpine glaciation to a dynamic polythermal ice sheet took place during the middle miocene the northernmost peninsula was overridden by an ice sheet in the early pliocene approximately 5 3 3 6 ma the long cooling history of the peninsula is consistent with the extended timescales of tectonic evolution of the antarctic margin involving the opening of ocean passageways and associated establishment of circumpolar circulation

nonlinear spectral mixture modeling of lunar multispectral data implications for lateral transport linear and nonlinear spectral mixture models applied to clementine multispectral images of the moon result in roughly similar spatial distributions of end member abundances however there are important differences in the absolute values of the predicted abundances the magnitude of these differences and the implications for understanding geological processes are investigated across a geologic contact between mare and highland in the grimaldi basin on the western nearside of the moon vertical and lateral mass transport due to impact cratering has redistributed mare and highland materials across the contract creating a gradient in composition solutions to linear and nonlinear spectral mixture models for identical spectral end members of mature mare mature highland and fresh crater materials are compared across this simple geologic contact in the grimaldi basin formal estimates of uncertainty in the calculated fractions of the end members are 1 profiles of mare abundance across the contact are extracted and compared quantitatively profiles from the linear mixture models indicate that the geologic contact has an average mare abundance of 60 and the compositional boundary is asymmetric with more mare transported onto the highland side of the contact than highland onto the mare side of the contact in contrast the nonlinear abundance profiles indicate that the geologic contact has an average mare abundance of 50 and the compositional boundary is remarkably symmetric given the expectation that materials will be intimately mixed on the surface of the moon and that the asymmetries implied by the linear model are not consistent with our understanding of lunar surface processes the non linear spectral mixture model is preferred and should be applied whenever quantitative abundance information is required the remarkable symmetry in the compositional gradients across this contact indicates that lateral mass transport dominates over vertical transport at this boundary

the materials of the lunar procellarum kreep terrane a synthesis of data from geomorphological mapping remote sensing and sample analyses major features of the moon s procellarum kreep terrane include subdued relief and extensive resurfacing with mare basalt consistent with high concentrations of th and other heat producing elements at depth we relate the chemistry of sampled materials to the geomorphology th surface concentrations determined by the lunar prospector 2 pixels and feo and tio2 concentrations derived from clementine ultraviolet visible spectral data on the basis of geologic maps each pixel was classified as mare terra or mixed near the periphery of the terrane terra pixel compositions are relatively feldspathic in the interior they mainly represent imbrium basin rim or ejecta deposits and are mainly incompatible trace element rich norites and presumably represent materials from a thick section tens of kilometers of the pre imbrium crust of the terrane excavated by the imbrium event although imbrium ejecta are the principal source of surface terra materials the imbrium event did not create the th rich procellarum kreep terrane broad continuous expanses of mare pixels are observed with little interruption from protruding terra or terra penetrating craters the mare basalt dominated regoliths of these areas have a wide range of tio2 concentrations 18 leading to the conclusion that the high th concentrations are in the mare basalts and are not present in the regoliths as terra derived materials volcanic glasses and impact glasses of mare basalt composition collected from the procellarum kreep terrane support this conclusion

lunar coordinates in the regions of the apollo landers laser retroreflectors were placed on the moon by apollo 11 apollo 14 apollo 15 and lunakhod 2 since then lunar laser ranging retroreflector measurements of the true distances between retroreflectors and earth based laser telescopes have been made by recording transit times the accuracy of these measurements has evolved from 10 cm in the 1970s to 3 cm in the 1990s accurate lunar coordinates of the retroreflectors were determined from these measurements williams et al 1996 apollo lunar surface experiment packages alsep were delivered to the lunar surface on missions 12 14 15 16 and 17 coordinates of these stations were determined from very long baseline interferometry vlbi measurements of their transmissions the vlbi measurements were combined with the laser ranging coordinates available at that time king et al 1976 these solutions for the alsep locations have been modified to be compatible with the current retroreflector solutions coordinates of lunar module locations and nearby craters are given

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

iron distribution of the moon observed by the kaguya gamma ray spectrometer geological implications for the south pole aitken basin the orientale basin and the tycho crater abstract in this study we describe the distribution of iron on the moon as obtained by the kaguya high energy resolution gamma ray spectrometer kgrs we achieved for the first time the identification of iron based on the fast neutron flux obtained by the kgrs the iron distribution obtained by kgrs is compared to that of the lunar prospector gamma ray spectrometer lp grs showing that the feo distributions observed by kgrs and lp grs in general are in good agreement furthermore we compare the iron content data obtained by kgrs and lp grs to spectral reflectance measurements of the clementine kaguya and chandrayaan 1 spacecraft as well as those inferred from returned samples we found differences in feo concentration and distribution in areas of moderate abundance 6 15 wt of the south pole aitken basin mare orientale and around the crater tycho crater it implies that high concentrations of feo at mare ingenii in the south pole aitken basin and mare orientale are due to the presence of mare basalts whereas the enriched feo content in the central depression of the south pole aitken basin and the tycho crater indicates the presence of mafic materials such as impact melt breccia

a chemical and petrological model of the lunar crust and implications for lunar crustal origin we utilize a variety of lunar sample and orbital geochemical data in conjunction with current knowledge of impact cratering processes to develop a chemical and petrological model of the lunar crust orbital chemical data indicate that the upper highlands surface on the moon has the bulk composition of anorthositic gabbro al2o3 26 28 wt greater than 90 of the area covered is dominated by material having compositional affinities with the ferroan anorthosites rather than with apollo type mg suite rocks considerations of the cumulative bombardment history of the moon indicate that the outer zone of impact brecciation extends tens of kilometers into the crust given the resolution of the orbital gamma ray data the ferroan anorthositic composition derived for the highlands surface may represent the bulk composition of the upper half of the lunar crust the observed enrichment in noritic components in basin ejecta with increasing basin size together with considerations of impact melt petrogenesis in lunar basins suggest that the bulk composition of the lower lunar crust is noritic al2o3 20 wt samples of lower crustal material are probably present in the apollo collections in the form of low k fra mauro lkfm and very high alumina vha basaltic impact melts our estimated value of total crustal al2o3 content 24 25 wt suggests that the lunar crust contains too much aluminum to have originated by a purely serial magmatism mechanism the large abundance of plagioclase within the lunar crust is probably a result of global scale fractionation of plagioclase in early lunar history the magma ocean hypothesis of crustal origin more readily explains the bulk composition of the lunar crust