magmatic effects of the lunar late heavy bombardment abstract large volumes of mare basalts are present on the surface of the moon located preferentially in large impact basins mechanisms relating impact basins and mare basalt eruptions have previously been suggested lunar impacts removed low density material that may have inhibited eruption and created cracks for fluid flow icarus 139 1999 246 and lunar basins have long been described as catchments for magma e g rev geophys space phys 18 1980 107 and references therein we present a new model for melt creation under near side lunar basins that is triggered by the impacts themselves magma can be produced in two stages first crater excavation depressurizes underlying material such that it may melt in situ second the cratered lithosphere rises isostatically warping isotherms at the lithosphere asthenosphere boundary which may initiate convection in which adiabatic melting can occur the first stage produces by far the largest volume of melt but convective melting can continue for up to 350 ma we propose that giant impacts account for a large portion of the volume and longevity of mare basalt volcanism as well as for several compositional groups including high alumina high titanium kreep rich and picritic magmas

the shape and internal structure of the moon from the clementine mission global topographic and gravitational field models derived from data collected by the clementine spacecraft reveal a new picture of the shape and internal structure of the moon the moon exhibits a 16 kilometer range of elevation with the greatest topographic excursions occurring on the far side lunar highlands are in a state of near isostatic compensation whereas impact basins display a wide range of compensation states that do not correlate simply with basin size or age a global crustal thickness map reveals crustal thinning under all resolvable lunar basins the results indicate that the structure and thermal history of the moon are more complex than was previously believed

planetary surface dating from crater size frequency distribution measurements partial resurfacing events and statistical age uncertainty abstract we describe the procedure to fit a cumulative production function polynomial to a partial crater size frequency distribution the technique is of particular use in deriving ages for surfaces which have undergone partial resurfacing events namely erosional or depositional events which have affected a limited diameter range of the crater population we demonstrate its use in obtaining times for both the surface formation and the resurfacing event we give a practical outline of the method for making age measurements from crater counts and how to identify resurfacing effects in the results we discuss the conversion of production function polynomials between common presentations and the statistical uncertainty of the determined ages with respect to the non linear chronology function and a minor refinement of data binning

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

a model for the thermal and chemical evolution of the moon s interior implications for the onset of mare volcanism crystallization of the lunar magma ocean creates a chemically stratified moon consisting of an anorthositic crust and magma ocean cumulates overlying the primitive lunar interior within the magma ocean cumulates the last liquids to crystallize form dense ilmenite rich cumulates that contain high concentrations of incompatible radioactive elements the underlying olivine orthopyroxene cumulates are also stratified with later crystallized denser more fe rich compositions at the top this paper explores the chemical and thermal consequences of an internal evolution model accounting for the possible role of these sources of chemical buoyancy rayleigh taylor instability causes the dense ilmenite rich cumulate layer and underlying fe rich cumulates to sink toward the center of the moon forming a dense lunar core after this overturn radioactive heating within the ilmenite rich cumulate core heats the overlying mantle causing it to melt in this model the source region for high tio2 mare basalts is a convectively mixed layer above the core mantle boundary which would contain small and variable amounts of admixed ilmenite and kreep this deep high pressure melting as required for the generation of mare basalts occurs after a reasonable time interval to explain the onset of mare basalt volcanism if the content of radioactive elements in the core and the chemical density gradients above the core are sufficiently high but within a range of values that might have been present in the moon regardless of details implied by particular model parameters gravitational overturn driven by the high density of magma ocean fe rich cumulates should concentrate high tio2 mare basalt sources and probably a significant fraction of radioactive heating toward the center of the moon this will have important implications for both the thermal evolution of the moon and for mare basalt genesis

formation of venusian canali considerations of lava types and their thermal behaviors because liquid water is unstable at present venusian surface conditions the discovery of channels termed canali on venus thousands of kilometers long was not predicted low viscosity lavas that remain fluid for several thousand kilometers are considered to be the canali forming agents possible compositions of venusian canali forming lavas include komatiite and high fe ti lunar type basalts results of analytical and numerical models of these lavas reveal that total cooling is more efficient on venus than on earth suggesting that venusian lavas rapidly form insulating crusts and thus that the canali lavas were essentially tube fed the models also reveal that thermal erosion should be less efficient on venus than on earth suggesting that venusian channels are either the product of mechanical rather than thermal erosion or constructional processes

compositional and temporal investigation of exposed lunar basalts in the mare imbrium region abstract this paper presents an updated stratigraphical and compositional study of the exposed maria within the imbrium basin on the moon clementine multispectral data were employed to derive tio2 and feo wt abundance estimates of potentially distinct basaltic flows additionally nasa lunar orbiter images were used to estimate flow ages using crater count statistics mare imbrium shows evidence of a complex suite of low to high ti basaltic lava units infilling the basin over an 800 million year timescale more than a third 37 of identified mare basalts were found to contain 1 3 wt tio2 two other major mare lithological units representing about 25 of the surface each show tio2 values between 3 5 and 7 9 wt the dominant fraction 55 of the sampled maria contain feo between 16 and 18 wt followed by 27 of maria having 18 20 wt and the remaining 18 14 16 wt feo a crater frequency count for diameters 500 m shows that in three quarters of the sampled mare crater counts range between 3 5 and 5 5 10 2 per km2 which translates according to a lunar cratering model chronology into estimated emplacement ages between 3 3 and 2 5 ga a compositional convergence trend between the variations of iron and titanium oxides was identified in particular for materials with tio2 and feo content broadly above 5 and 17 wt respectively suggesting a related petrogenesis and evolution according to these findings three major periods of mare infill are exposed in the imbrium basin despite each period showing a range of basaltic compositions classified according to their tio2 content it is apparent that at least within these local geological settings the igneous petrogenesis generally evolved through time towards more tio2 and feo rich melts

the role of magma buoyancy on the eruption of lunar basalts it has long been recognized that mare basalts on the moon are preferentially located both on the earth facing hemisphere and within large impact basins a popular model that accounts for this observation assumes that these magmas were denser than the lunar crust that they accumulated at the crust mantle interface and that eruptions occurred only when this magma chamber became overpressurized in this paper we re evaluate this model and argue that it is not consistent with the available data nor with models of dike propagation as an alternative hypothesis we propose that magma buoyancy is the predominant factor that determines whether mare basalts erupt at the surface or form crustal intrusions instead we have computed the densities of mare basaltic magmas and find that some are in fact less dense than the moon s upper anorthositic crust based on the widely accepted view that the lunar crust becomes more mafic with depth we also show that all mare basaltic magmas should be less dense than the lower portion of the crust thus if the upper anorthositic crust was regionally removed by an impact event then any mare basaltic magma could have risen to the surface there based on buoyancy considerations alone in support of this model we note that mare basalts are indeed found wherever geophysical crustal thickness models predict the upper crust to be absent furthermore many of the basalts that erupted within the anorthositic highlands are predicted to be less dense than the underlying crust based on remote sensing data the high titanium flows within oceanus procellarum are somewhat problematical to our model in that an anorthositic crust is predicted to be present beneath them using results from recent lunar thermal models we suggest that these magmas may have overcome their negative buoyancy in the crust by possessing superliquidus temperatures if magma buoyancy does indeed control whether or not a basaltic eruption will occur then this implies that the quantity of magma produced beneath the south pole aitken basin was about 10 times less than that of the nearside fl 2001 elsevier science b v all rights reserved

on the relative and absolute ages of seven lunar front face basins ii from the crater counts abstract from counts of postbasin craters larger than 30 km in diameter lying within or near to seven giant front face lunar basins relative ages for the basins may be obtained these relative ages correlate well with absolute basin ages found from viscosity arguments in r b baldwin 1987 icarus 70 from crater counts the basins are in the following sequence of increasing relative age orientale imbrium crisium serenitatis nectaris humorum and the unnamed basin lying between werner and the altai ring the absolute ages from baldwin 1987 range from 3 80 to 4 30 109 years while a correlation with the relative ages of this paper yields a range of 3 79 to 4 27 109 years the discrepancy is largely due to serenitatis where the debris from imbrium has presumably buried some post serenitatis craters from both sets of data there is no evidence that a terminal lunar cataclysm ever occured

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

geology of mare deposits in south pole aitken basin as seen by clementine uv vis data a multispectral analysis of 21 discrete lunar mare deposits within the south pole aitken basin was undertaken in order to model the general mineralogical composition of farside mare deposits so that the near and farside may be compared in terms of magma generation and emplacement determination of each deposit s mineralogy was based upon albedo the 0 75 0 95 m ratio indicating the presence of a 1 0 m absorption band and the strength and shape of that band a combination of improved spatial resolution and the availability of the general multispectral signature for each pond allowed deposits to be examined for homogeneity in order to assess the nature and number of flows represented feo and tio 2 abundances were also estimated based upon the resultant data 19 out of 21 ponds were determined to be mare deposits of these 19 15 had spectra well defined enough to classify general mineralogy nine having high ca pyroxene signatures indicative of basalt and six showing low ca signatures suggesting a substantial noritic component we believe these noritic signatures can plausibly be attributed to vertical lateral soil mixing processes for the smallest ponds although a unique lithology cannot be ruled out for the largest pond a majority of ponds in this study region have homogeneous spectral signatures interpreted to represent individual eruptive phases this indicates that very large volumes for these regions may be typical also because such volumes are comparable to the largest terrestrial eruptions they may have formed by a similar mechanism of emplacement the vast majority of mature soils are spectrally redder and thus have a lower estimated feo abundance than the mare serenitatis soil standard ms 2 in particular and nearside basalts in general these soils also average low to medium estimated tio 2 abundance similar to apollo 12 and 15 and luna 24 the observations made here are consistent with a scenario in which basalts with low feo and low to medium tio 2 contents were deposited during the lunar peak volcanic period that occurred in the late imbrian 3 80 3 20 ga and because of their small areal extent were more susceptible to mixing processes than nearside basalts

space weathering on airless bodies resolving a mystery with lunar samples using new techniques to examine the products of space weathering of lunar soils we demonstrate that nanophase reduced iron npfe0 is produced on the surface of grains by a combination of vapor deposition and irradiation effects the optical properties of soils both measured and modeled are shown to be highly dependent on the cumulative amount of npfe0 which varies with different starting materials and the energetics of different parts of the solar system the measured properties of intermediate albedo asteroids the abundant s type asteroids in particular are shown to directly mimic the effects predicted for small amounts of npfe0 on grains of an ordinary chondrite regolith this measurement and characterization of space weathering products seems to remove a final obstacle hindering a link between the abundant ordinary chondrite meteorites and common asteroids

formation of an eroded lava channel within an elysium planitia impact crater distinguishing between a mechanical and thermal origin a lava channel identified on the wall of an elysium planitia impact crater is investigated to identify the dominant erosion mechanism mechanical vs thermal acting during channel formation observations of channel morphology are used to supplement analytical models of lava channel formation in order to calculate the duration of channel formation the velocity of the lava flowing through the channel and the erosion rate in each erosion regime considered results demonstrate that the channel observed in the elysium planitia impact crater formed primarily due to mechanical erosion in a more general sense results of this study suggest that lava channels can form primarily due to thermal erosion in the presence of more gradual slopes and more consolidated substrates whereas lava channels can form primarily due to mechanical erosion in the presence of more energetic flows on steeper slopes and more poorly consolidated substrates therefore both erosion regimes must be considered when analyzing origins of eroded lava channels that cut through strata of different strengths

pyroxene spectroscopy revisited spectral compositional correlations and relationship to geothermometry the authors wish to thank the various agencies which have provided the necessary support for this project including grants in aid of research from sigma xi the scientific research society to e a c the geological society of america grant 3741 87 to e a c and nasa planetary geology and geophysics grant nagw 642 to m j g

crustal thickness of the moon implications for farside basin structures 1 based on the latest selene lunar gravity and topography model obtained by kaguya mission we compute the lunar crustal thickness map to investigate differences between farside basin structures the thickest crust is located in the southern rim of the dirichlet jackson basin and the thinnest crust at the moscoviense basin the thickest crust corresponds to the highest topography and is consistent with airy isostasy the thinnest crust is due to an abnormally large mantle plug the crustal thicknesses at apollo 12 14 sites of our crustal thickness model are 45 1 and 49 9 km the crustal thickness map indicates that the differences between recently proposed type i and type ii basins are probably controlled by the ratio between pre impact crustal thickness and impact scale

buried stratigraphic relationships along the southwestern shores of oceanus procellarum implications for early lunar volcanism the composition of mare highland boundaries is investigated in the region of southwestern oceanus procellarum using multispectral images from the galileo solid state imaging system the data are analyzed using a linear image based spectral mixture model to map the distribution and abundance of spectral end members representing mare basalt mature highland soils and fresh crater materials the fraction images that result from the mixture modeling are then integrated into a geographic information system database to analyze the relationship between the compositional gradients and regional geologic and geomorphic units within this framework three basic types of mixing gradients are recognized narrow mixing zones broad mixing zones and complex mixing zones the narrow zones appear to be the result of simple postformation lateral mass transport of surface materials due to the time averaged effects of impact cratering and regolith gardening the broad or moderate mixing zones exhibit evidence for significant incorporation of basalt into the distal basin ejecta of orientale and thus are interpreted to indicate that pre orientale volcanism and volcanic deposits were widespread in the procellarum region this is further corroborated by the mare rich ejecta blanket observed for the 100 km diameter impact crater letronne the complex mixing zones show evidence for extensive pre orientale and perhaps pre imbrium cryptomare as well as some volcanism extending into the late imbrian period these results indicate that mare highland boundaries frequently contain a convolved geologic record that allows insight into the geologic events prior to the final one apparently recorded by surface deposits for this region of the moon we now recognize that volcanism was well established and widespread in early imbrian time but had become more focused to a few major volcanic regions humorum procellarum by the late imbrian

volumes of lunar lava ponds in south pole aitken and orientale basins implications for eruption conditions transport mechanisms and magma source regions in an effort to characterize individual eruptive phases and events 86 isolated mare deposits ponds in the lunar south pole aitken and orientale regions were analyzed to obtain information on areas volumes and other characteristics deposits likely to represent single eruptive episodes have area mean values of 2000 km2 in the south pole aitken basin and 1100 km2 in the orientale basin pond volumes range from 35 to 8745 km3 with a mean value of 860 km3 for south pole aitken and 10 to 1280 km3 with a mean value of 240 km3 for the orientale region no evidence was found for shallow crustal magma reservoirs the relatively common occurrence of sinuous rilles in orientale is consistent with very high effusion rates and the large volumes of individual eruptive episodes tens to many hundreds of km3 are comparable to flood basalt eruption volumes on earth pond morphologies are consistent with extrusion from deep probably subcrustal reservoirs distribution of deposits suggests that many ponds may be derived from single reservoirs comparison of ponds in both basins shows a higher areal density and average volume of lava ponds in the south pole aitken basin relative to the orientale area this is plausibly attributed to the extreme depths of the south pole aitken basin and the correspondingly thinner crust there relative to the orientale region these observations are consistent with magma ascent and eruption mechanisms that are strongly dependent on the overpressurization of deep seated source regions the subsequent propagation of dikes and the thickness of the intervening lunar crust through which these dikes must rise

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

the deep structure of lunar basins implications for basin formation and modification we present models for the structure of the crust and upper mantle beneath lunar impact basins from an inversion of gravity and topographic data from the nearside of the moon all basin models display a thinner crust and an elevated moho beneath the central basin region compared to surrounding areas a signature of the processes of basin excavation and mantle uplift during collapse of the transient cavity there is a general decrease in the magnitude of apparent uplift of mantle material with increasing basin age we attribute this relation primarily to enhanced rates of ductile flow of crustal material early in lunar history when crustal temperatures were relatively high and the effective elastic lithosphere was thin the more relaxed topographic and moho relief associated with older basins on the central nearside may in particular be at least partly a consequence of the extensive subsurface heating associated with the formation of the large procellarum basin the deep structure of the youngest basins constrains the geometry of the cavity of excavation and the amount of crustal material ejected beyond the basin rim from the volumes of the topographic basin of mare basalt fill and of uplifted mantle material the volume of crustal material ejected beyond the basin rim for an orientale sized event was of the order of 107 km 3 a near constant thickness of nonmare crustal material beneath the central regions of young basins of various diameters and preimpact crustal thicknesses suggests that the transient cavity excavated to at least the base of the crust for the largest basins significant excavation into the mantle may have been impeded by an abrupt increase in strength at the lunar moho

the isotopic record of lunar volcanism abstract the timing and extent of lunar volcanism was determined primarily by the internal thermal evolution of the moon a late heavy bombardment produced most of the observable lunar basins easily recognized stratigraphic markers and also may have influenced lunar volcanism most of the nearside basins seem to have been produced 3 8 4 0 ga ago during a period often referred to as the lunar cataclysm the pre cataclysm period was characterized by formation of the lunar crust plutonic rocks within the crust and pre mare volcanism isotopic analysis of breccia clasts pre dating the cataclysm has yielded an outline of this period the isotopic record of post cataclysm mare volcanism is clear but incomplete because samples from the youngest mare areas are lacking specifically the isotopic data show that some lunar anorthosites formed 4 45 ga ago consistent with early formation of an anorthositic lunar crust some mg suite norites troctolites and dunites also formed approximately contemporaneously with the oldest anorthosites but others are up to 200 300 ma younger more evolved rocks granites and quartz monzodiorites also formed between 4 4 and 4 0 ga ago the earliest known pre mare volcanism at 4 25 ga ago included aluminous mare like basalts and an olivine gabbronorite similar to apollo 12 basalts kreep basalt volcanism began at least 4 1 ga ago approximately contemporaneously with that of the ancient mare like basalts and continued during the cataclysm recorded instances of high ti mare basalt volcanism began during or immediately after the cataclysm low ti mare basalt volcanism is the most recent for which samples are available the isotopic data record an early primary lunar differentiation during which mare basalt sources formed probably by crystallization of cumulus minerals from a lunar magma ocean the isotopic record of post cataclysm basalts indicates a heterogeneous lunar mantle and can be explained by partial melting of cumulate sources but more complex petrogenesis also has been suggested more complex petrogenetic processes including assimilation and assimilation fractional crystallization afc seem to be required for pre mare volcanics the isotopic data contain a hint that petrogenesis of the oldest pre mare volcanics may be linked to formation of the so called procellarum basin possibly the oldest and largest lunar basin such a basin would provide a geologic context for the pre mare volcanics and its formation may have been a defining moment in lunar history

a lava flow without a source the cohassett flow and its compositional components sentinel bluffs member columbia river basalt group abstract the eruption of sentinel bluffs member lava flows at approximately 15 5 ma marked the end of grande ronde basalt volcanism the most voluminous period of the columbia river basalt group more than 10 000 km3 of lava erupted from northerly trending feeder dikes in eastern washington and northern oregon and flowed westward down an ancestral paleoslope covering more than 169 700 km2 of the flood basalt province the sentinel bluffs member consists of six phases or types defined by their compositions lava flows having the first compositional type were the most voluminous and reached the pacific ocean the volume of later lava flows having the other compositional types declined with time until the final eruption produced the second largest volume of basalt at the source area compositional variation in sentinel bluffs lava flows is relatively small this homogeneity allows the individual compositional types and thus phases of the eruption to be easily recognized farther west however composition

on the source region of the lunar mare basalt the lack of pervasive flooding of the south pole aitken spa basin raises questions about the mare basalt source region models whether deep or shallow this paper investigates the dichotomy between the nearside imbrium sized flooded basins and the unflooded spa basin by modeling the effects of giant impacts on the dynamics of the lunar mantle we allow an initially spherically symmetric moon model to evolve through mantle convection for a few hundred million years and then let an imbrium or spa sized impact occur the subsequent thermal convection in the lunar mantle resulting from the thermal energy introduced by an impact is determined for the next 100 m y the mantle is assumed to be incompressible with an infinite prandtl number and a temperature dependent viscosity it is shown that the mantle circulation induced by an imbrium sized impact can only slightly push aside the radioactive rich potassium rare earth element and phosphorous kreep layer from beneath the surrounding crust this concentrates the radioactive elements beneath the low thermal conductive ejecta blanket and provides a suitable condition for enhancement of radioactive heating and subsequent partial melting and basaltic flow to the basin on the other hand a spa sized impact is capable of generating mantle circulation vigorous enough to strip away the kreep layer from beneath the surrounding crust within a time period of 40 m y this removal prevents radioactive heating and partial melting beneath the surrounding crust thus explaining the lack of flooding of spa basin these results are insensitive to the time of impacts but are strongly dependent on their sizes

mapping the feo and tio2 content of the lunar surface with multispectral imagery the derivation of quantitative elemental concentrations from multispectral imaging of the moon has long been a goal of lunar remote sensing concentration maps at the spatial resolutions available from the recent clementine mission would provide a revolutionary new tool for understanding the origin and evolution of the lunar crust lucey et al 1995 presented a method for extracting the concentration of fe from multispectral imaging of the moon this paper examines and quantifies important aspects ofthat technique left unexamined by lucey et al which had the potential to severely limit its utility these aspects include the effects of maturity grain size mineralogy shading due to topography and the presence of glass we also present a new algorithm for derivation of tio2 from multispectral imaging of both mare and highland units we find that both techniques are only weakly sensitive to maturity and that they have about 1 wt accuracy based on examination of the spectral properties and compositions of resolved lunar sampling stations presented by blewett et al 1997 we also discuss these findings in the context of two contrasting views of the effect of composition on lunar spectral properties presented by pieters and coworkers and hapke and coworkers we find the view of hapke and coworkers to be more consistent with our observations using a global mosaic of clementine multispectral data and these element derivation algorithms we find that the global modal abundance of feo is 4 5 wt 1 wt and the global modal abundance of tio2 is 0 45 wt 1 wt

lunar regional dark mantle deposits geologic multispectral and modeling studies clementine five channel uv visible uvvis data have been used to study seven regional dark mantle deposits dmds on the moon the dmds were mapped in distribution to determine their extent and stratigraphic relationship to other geologic units based upon the spectral properties for each dmd the crystallization of the beads in each deposit was inferred and used to estimate cooling rates in the volcanic plumes that emplaced the deposits deposits with a high concentration of glasses reflect volcanic plumes that had low optical densities and high cooling rates whereas deposits dominated by crystallized beads indicate plumes with slower cooling rates due to higher optical densities spectral data from each of the regional dmds show that their glass crystallized bead ratio can be estimated based upon their 415 750 and 750 950 nm values and comparison to laboratory spectra for the beads patches of young dark mantle in the sinus aestuum dmd represent one extreme with the bluest color highest 415 750 and weakest glass band absorption lowest 750 950 of all the dmds at the other extreme is the aristarchus plateau dmd with the reddest color and strongest glass band absorption the other nearside dmds including taurus littrow sulpicius gallus rima bode and mare vaporum lie between these two extremes due to intermediate mixtures of the crystallized beads and glasses with other local soils the orientale ring dmd on the western limb is dominated by volcanic glasses and is spectrally similar to the localized dmds found in alphonsus crater we have identified a central vent for the orientale ring dmd and model the eruption as degassing of a near surface dike to produce a 20 km high umbrella shaped plume with ejection velocities of 360 m s and deposition of the glasses at an average radius of 80 km from the vent although we cannot identify the exact sources for the other regional dmds probably because they are buried beneath younger mare the eruptions most likely resulted from dikes breaching the surface and producing a volcanic plume dominated by larger greater than submillimeter hot clasts that formed mare and sinuous rules the small percent of clasts that form the volcanic beads are carried by the expanding gas cloud to large distances in some cases 100 km to produce the observed continuous regional dmds the lack of basalt samples that can be petrologically related to the volcanic glasses may be a result of their spatial separation with the basalts flowing into the basins while the beads are deposited both into the basins and on the adjacent highlands

crustal diversity of the moon compositional analyses of galileo solid state imaging data the multispectral images of the lunar limb and farside obtained by the solid state imaging ssi system on board the galileo spacecraft provide the first new pulse of compositional data of the moon by a spacecraft in well over a decade the wavelength range covered by ssi filters 0 4 1 0 m is particularly sensitive to the composition of mare basalts the abundance of mafic ferrous minerals and the maturity of the regolith to a first order the limb and farside material is consistent with previous characterization of nearside lunar spectral types for mare and highland soils and craters most basalts are of an intermediate tio 2 composition and most of the highland crust is feldspathic with local variations in mafic content identified principally at impact craters dark manfling material on the farside can be interpreted in terms of known properties of lunar pyroclastic glass regions of cryptornate are shown to have spectral properties intermediate between those of highland and mare soils as would be expected from a mixture of the two there are several important exceptions and surprises however unlike the basalt types identified on the nearside limb and farside basalts exhibit an exceptionally weak 1 xm ferrous absorption band this may indicate a compositionally distinct lunar basalt group that for example is more mg rich than most basalts of the nearside some of the most notable compositional anomalies are associated with south pole aitken basin this large region has a much lower albedo than surrounding highlands the inner darkest portion of the basin exhibits optical properties indistinguishable low ti basalts deposits to the south exhibit unique properties with a strong and broad ferrous 1 xrn absorption most consistent with abundant olivine the unusual compositions associated with south pole aitken and their spatial e3tent suggests the impact creating this huge lunar basin excavated mafic rich lower crust or perhaps mantle material 1 intro oucri ion

moon near infrared spectral reflectance a first good look a positive identification of the minerals olivine plagioclase and several types of pyroxenes were made at several locations on the lunar surface by using remote measurements for example the crater aristarchus is found to have an average pyroxene composition of augite and plagioclase is obviously present a dark mantle deposit in the crater j herschel is at least partly composed of a mixture of 70o7o olivine and 30o7o pyroxene these determinations were possible because the reflectance spectra for 10 20 km diameter lunar areas have been measured for the first time in the ir spectral region 0 65 2 5 m with sufficient spectral resolution and photometric precision to define mineral electronic absorption bands the reflectance for all lunar regions observed over 100 to present continues to increase toward longer wavelengths to at least 2 5 m and several mineral absorption bands appear the telescopic spectra are of similar quality and contain features similar to laboratory spectra of lunar samples the absorption features in several spectra have been quantitatively analyzed using newly developed computer processing techniques including thermal flux removal and absorption band fitting to produce these mineral identifications detection and quantitative analysis of these absorptions provide a much improved basis for remotely determining and mapping surface mineralogy quantitatively from the ground or using airborne or spacecraft platforms

lunar mare volcanism stratigraphy eruption conditions and the evolution of secondary crusts abstract lunar mare basalt deposits cover 17 of the lunar surface occur preferentially in topographic lows on the nearside and have a total volume estimated at 1 107 km3 analysis of returned samples and photogeologic and remote sensing studies shows that mare volcanism began prior to the end of heavy bombardment the period of cryptomare formation in pre nectarian times and continued until the copernican period a total duration approaching 3 5 4 ga stratigraphic analyses show that the flux was not constant but peaked in early lunar history during the imbrian period which spans the period 3 85 3 2 ga average volcanic output rate during this peak period was about 10 2 km 3 a very low relative to the present global terrestrial volcanic output rate and comparable to the present local output rates for individual volcanoes such as vesuvius and kilauea hawaii volcanic landforms indicate that many eruptions were of high volume and long duration some eruptions associated with sinuous rules may have lasted of the order of a year and emplaced 103 km3 of lava representing the equivalent in one year of about 70 000 years at the average flux shallow magma chambers were uncommon the nearsidefarside mare deposit asymmetry can be readily explained by differences in crustal thickness magma ascending from the mantle or from a buoyancy trap at the base of the crust should preferentially extrude to the surface on the nearside but should generally stall and cool in dikes in the farside crust extruding only in the deepest basins the occurrence of farside maria within craters whose diameter is generally near to or less than the thickness of the crust may be accounted for by the difference between local and regional compensation dikes that establish pathways to the surface on the nearside should have very high volumes comparable to the volumes associated with many observed flows and sinuous rilles an abundance of dikes should exist in the lower crust of the moon many more than those feeding surface eruptions the upper limit is 37 50 of the crust by volume the presence and abundance of such dike swarms have important implications for the interpretation of the average composition of the lunar crust and the composition of basin and crater ejecta the interplay between thermal contraction and differentiation leads to net cooling and ultimate contraction of the outer portions of the moon resulting in a regional horizontal compressive stress acting on the lunar crust in addition overall cooling and deepening of sources require the production of ever larger volumes of magma in order to reach the surface with time stresses became high enough so that few dikes could open to the surface causing eruptive activity to be severely diminished in the eratosthenian and perhaps to cease in the copernican period lower stress levels are required to terminate eruptive activity on the lunar farside consistent with the imbrian age of the farside maria and the nearside location of the youngest maria lunar mare deposits provide an example of the transition from primary crusts to secondary crusts and illustrate the significance of several factors in the evolution of secondary crusts such as crustal density variations in crustal thickness presence of impact basins state and magnitude of stress in the lithosphere and general thermal evolution these factors are also responsible for the extremely low volcanic flux even during periods of peak extrusion

ages of mare basalts on the lunar nearside the chronology of lunar volcanism is based on radiometric ages determined from apollo and luna landing site samples regional stratigraphic relationships and crater degradation and size frequency distribution data for units largely defined prior to the end of the apollo program here we report on new crater size frequency distribution data for 139 spectrally and morphologically defined basalt units which are exposed in six nearside impact basins australe tranquillitatis humboldtianum humorum serenitatis and imbrium crater size frequency distribution measurements are a statistically robust and accurate method to derive absolute model ages of unsampled regions of the moon compared to crater degradation ages crater size frequency ages performed on spectrally defined units offer significant improvements in accuracy our investigation showed that 1 in the investigated basins lunar volcanism was active for at least 1 5 2 0 b y starting at about 3 9 4 0 b y and ceasing at 2 0 b y 2 most basalts erupted during the late imbrian period at about 3 6 3 8 b y 3 significantly fewer basalts were emplaced during the eratosthenian period 4 basalts of copernican age were not found in any of the investigated basins 5 lunar basin filling volcanism probably started within 100 m y after the formation of the individual basins we also assessed the relationship between impact basin age and the history of mare basalt emplacement in these basins we found that 1 in all pre nectarian basins australe and tranquillitatis as well as in the humboldtianum basin which is of nectarian age the distribution of surface ages is clearly dominated by only a single peak in the number of erupted units at 3 6 3 8 b y 2 in the younger basins humorum serenitatis and imbrium a second peak at 3 3 3 5 b y is observed 3 basalt eruptions younger than 2 6 b y occur only intermittently and 4 in the youngest basins serenitatis and imbrium we see an extended period of active basin filling volcanism 1 5 1 6 b y which is 500 m y longer than in the australe and humorum and even 1 0 b y longer than in tranquillitatis and humboldtianum

compositional analyses of lunar pyroclastic deposits abstract the 5 band clementine uvvis data at 100 m pixel were used to examine the compositions of 75 large and small lunar pyroclastic deposits lpds and these were compared to representative lunar maria and highlands deposits results show that the albedo spectral color and inferred composition of most lpds are similar to those of low titanium mature lunar maria these lpds may have consisted largely of fragmented basalt with substantial components of iron bearing mafic minerals pyroxenes olivine and smaller amounts if any of volcanic glass several smaller lpds also show substantial highland components three classes of very large deposits can be distinguished from most lpds and from each other on the basis of crystallinity and possible titanium content of their pyroclastic components one class has spectral properties that are dominated by high titanium crystallized black beads e g taurus littrow a second consists of a mixture of high titanium glasses and beads with a higher glass bead ratio sulpicius gallus than that of taurus littrow and a third has a significant component of quenched iron bearing volcanic glasses aristarchus with possible moderate titanium contents although areally extensive these three classes of very large pyroclastic deposits compose only 20 of the 75 deposits studied 27 and eruption of such materials was thus likely to have been less frequent on the moon

thermal evolution of a thicker kreep liquid layer we consider the thermal evolution of the thickened potassium rare earth element and phosphorous kreep liquid layer that extends over a significant fraction of the lunar nearside with a prescribed thickness and heat production and beneath an insulating anorthosite crust this layer represents a subcrustal heat source beneath the procellarum imbrium terrane and may be responsible for the localized and anomalous enrichments of highly incompatible elements in this terrane in some models this thickened liquid layer is the thermal source for the remelting of mare basalts and also produces the parent magmas of the magnesian suite indeed a kreep liquid layer thickened from 5 to 10 km with more than 200 times chondritic heat producing elements does not continue to cool but undergoes a reheating and grows in thickness by dissolving several times its mass of anorthosite and ultramafic cumulates however such a liquid layer cannot give rise to the parent magmas to the magnesian suite because it cannot account for the extraordinarily high incompatible element content the primitive major element content or the positive end of the magnesian suite this growing layer will also form an impenetrable barrier to the eruption of mare basalts and is generally inconsistent with a number of geophysical constraints of the moon specifically the existence of mascons subsequent to the basin filling by mare basalts a thickened kreep liquid layer can however explain the asymmetry in the distribution of kreep rich rock on the lunar crust such a kreep layer must be efficiently cooled and be quickly solidified to avoid some of the difficulties described above a thinned anorthosite crust would allow efficient heat loss and induce crystallization of such a layer early in lunar history

compositional studies of the orientale humorum nectaris and crisium lunar basins we have used full resolution 250 m pixel clementine images to map the compositions of ejecta from four multiring basins on the moon orientale humorum nectaris and crisium all basins have relatively feldspathic ejecta with iron contents ranging from 2 to 6 wt feo some basins show remarkably homogeneous ejecta blankets orientale while others display distinct compositional zoning within exterior sectors of the basin crisium in some cases this zoning correlates with morphologically observed ejecta facies nectaris the iron poor composition of most basin ejecta indicates that the crust of the moon at these locations is feldspathic down to depths of at least several tens of kilometers the likely sampling depth of basin forming impacts the inner rings of all four basins display massifs and small crater floors of nearly pure anorthosite feo 1 wt virtually the only such occurrences of this rock type on the moon because basin rings are structurally emplaced topographic elements derived from depths of at least 10 20 km into the moon we postulate that basin inner rings are sampling a unique stratigraphic level in the moon and at these depths the primordial pristine anorthositic crust of the moon is largely preserved below this zone of anorthosite is the more mafic region of the lower crust probably having highland basalt composition feo 10 wt al2o3 18 22 wt the petrologic nature of lower crustal levels remains uncertain but must at least in part include members of the mafic highland suite such as norites and troctolites

compositional analysis of the orientale basin using full resolution clementine data some preliminary results clementine imaged the moon globally in eleven different wavelengths we used these data to construct a full resolution 250 m pixel multispectral image of the orientale basin using this image in conjunction with other data sets such as earth based spectra we mapped the compositional units of the basin to obtain insights into its formation and evolution the basin ejecta units are largely uniform in composition with the inner montes rook formation being slightly more mafic than the outer hevelius formation the inner and outer rook mountains display many outcrops of pure anorthosite these and other findings are consistent with a three layer model for the lunar crust consisting of a mixed zone megaregolith tens of kilometres thick overlying a layer of anorthosite above a basaltic layer

transition from complex craters to multi ringed basins on terrestrial planetary bodies scale dependent role of the expanding melt cavity and progressive interaction with the displaced zone 1 the observed differences between complex craters and multi ringed basins are described and a combined transient cavity displaced zone melt cavity model is explored to account for the observations in this nested melt cavity model the increasing influence of the percentage of the target undergoing impact melting at the sub impact point with increasing size the differential melt scaling of cintala and grieve 1998 causes fundamental changes in the nature of the transient cavity its relationship to the displaced zone and its short term collapse behavior the transition from complex craters to two ring basins involves expansion of the melting front into the displaced zone formation of a two component excavation cavity and a concomitant radial expansion outward of the zone of maximum elastic rebound the short term modification stage is then dominated by the strength differences between the fluid melt in the inner cavity and rocks of the displaced zone the highly shocked rocks at the outer margin of the expanded parabolic melting front rebound to form the expanded peak ring moving upward and laterally inward easily displacing fluid melt filling the inner depression at larger sizes differential melt scaling causes the peak ring diameter to expand relatively more rapidly than the basin rim and upon collapse the increased volume of melt ponds in the rebounded melt cavity inside the expanding peak ring as the transient melt cavity further increases proportionally in size it penetrates through the base of the displaced zone with significant consequences the resulting modification stage now incorporates into the collapse process inward and upward movement along the base of the displaced zone listric failure occurs inward into the fluid melt cavity beginning at the edge of the melt cavity and extending out along the base of the displaced zone up to the base of the rim structural uplift at 1 5 crater radii this forms an additional outer ring and a resulting megaterrace modifying the radial ejecta on the collapsed rim to form a domical facies at multi ring basin scales the significantly deeper penetration that occurs in the expanding melt cavity accounts for the maximum crustal thickness decrease that occurs inside the peak ring in the final basin early onset and higher density of peak ring basins on mercury is predicted by higher mean impact velocity and differential melt scaling

measuring moonlight an overview of the spatial properties lunar coverage selenolocation and related level 1b products of the moon mineralogy mapper 1 the moon mineralogy mapper m3 a high resolution high precision imaging spectrometer flew on board india s chandrayaan 1 mission from october 2008 through august 2009 this paper describes some of the spatial sampling aspects of the instrument the planned mission and the mission as flown we also outline the content and context of the resulting level 1b spatial products that form part of the m3 archive while designed and planned to operate for 2 years in a 100 km lunar orbit m3 was able to meet its lunar coverage requirements despite the shortened mission an increase of the orbit altitude to 200 km and several relevant problems with spacecraft attitude timing and ephemeris the unexpected spacecraft issues required us to invent a novel two step approach for selenolocation leveraging newly available lunar reconnaissance orbiter lunar orbiter laser altimeter lola topography and an improved spacecraft ephemeris we have created a method that permits us to bootstrap spacecraft attitude estimates from the image data themselves this process performs a nonlinear optimization to honor a set of data derived image to image tie points and image to lola control points error analysis of the final results suggests we have converged to a selenolocation result that has image to image root mean square rms errors less than 200 m and image to lola rms errors less than 450 m despite using data derived spacecraft attitude results the level 1b products include the lunar coordinates resulting from this inversion process and 10 relevant observational geometry parameters that fully characterize the ray tracing geometry on a pixel by pixel basis

impact induced convection as the main mechanism for formation of lunar mare basalts 1 using a suite of numerical models we show that impact induced convection in the moon can explain the formation of lunar mare basalts the depth range of their source region the observed delay between impact basin formation and starting time of mare flows and the long duration of the basaltic flows the effects of an impact on the thermal evolution of the moon and melt production in the mantle are investigated using convection calculations in an axisymmetric cylindrical coordinate system an ascending mantle plume is allowed to melt as it crosses the depth of the solidus temperature we consider two different models permeable and impermeable five different viscosity models and three different impact basin sizes are examined the total amount of melt produced by the permeable model with 1000 times viscosity contrast across the computation domain is comparable to the observed mare flows in imbrium and orientale basins moreover the starting time of major melting in the mantle and its duration are also compatible with the observations the model also allows a rigid lithosphere to develop beneath the basins that is capable of supporting the mascons largely created during the peak mare flow period the model for south pole aitken basin results in a substantial amount of melting in the mantle which does not seem to be compatible with the observations a potassium rare earth elements and phosphorus kreep layer with high concentration of radioactive elements incorporated directly beneath the crust has minor effects on the melt production in the mantle

visible near infrared spectra of experimentally shocked plagioclase feldspars 1 high shock pressures cause structural changes in plagioclase feldspars such as mechanical fracturing and disaggregation of the crystal lattice at submicron scales the formation of diaplectic glass maskelynite and genuine melting past studies of visible near infrared spectra of shocked feldspars demonstrated few spectral variations with pressure except for a decrease in the depth of the absorption feature near 1250 1300 nm and an overall decrease in reflectance new visible near infrared spectra 400 2500 nm of experimentally shocked 17 56 gpa albite and anorthite rich rock powders demonstrate similar trends including the loss of minor hydrated mineral bands near 1410 1930 2250 and 2350 nm however the most interesting new observations are increases in reflectance at intermediate pressures followed by subsequent decreases in reflectance at higher pressures the amount of internal scattering and overall sample reflectance is controlled by the relative proportions of micro fractures submicron grains diaplectic glass and melts formed during shock metamorphism we interpret the observed reflectance increases at intermediate pressures to result from progressively larger proportions of submicron feldspar grains and diaplectic glass the ensuing decreases in reflectance occur after diaplectic glass formation is complete and the proportion of genuine melt inclusions increases the pressure regimes over which these reflectance variations occur differ between albite and anorthite consistent with thermal infrared spectra of these samples and previous studies of shocked feldspars these types of spectral variations associated with different peak shock pressures should be considered during interpretation and modeling of visible near infrared remotely sensed spectra of planetary and asteroidal surfaces

gruithuisen domes region a candidate for an extended nonmare volcanism unit on the moon small lunar areas known as red spots are thought to represent good candidates for nonmare volcanic units predating or contemporaneous with the period of mare volcanism in this study we present imaging telescopic and orbital clementine multispectral surveys of the gruithuisen region located in the northwestern border of mare imbrium which contains imbrian age domical features of likely viscous volcanic origin with spectral characteristics of red spot areas a rather spectrally homogeneous unit having typical characteristics of red spots is found to coincide with the material within the morphological boundaries of the gruithuisen delta gamma and northwest domes an extended dome like unit is identified spectrally and surrounds and extends to the west and the north of the domes this unit shows spectral characteristics close to those of the domes suggesting the presence of a significant amount of dome material extending many kilometers away from the domes themselves both the spectral characteristics of the dome and the dome like unit are clearly different from those of highlands and the surrounding mare basalts the spectral identification of a widespread dome like unit suggests that the specific style of eruption that is inferred for the formation of the domes i e viscous flows of possible more silicic composition might have occurred on a regional scale in this part of the moon prior to the iridum event about 3 8 gyr ago this volcanic style appears to be more widespread in the early part of lunar history than previously thought

lunar red spots stratigraphic sequence and ages of domes and plains in the hansteen and helmet regions on the lunar nearside 1 basaltic mare materials extruded between 4 ga and 1 2 ga ago and formed large expanses on the lunar nearside in contrast to the maria volcanic shields domes and cones also occur but cover only a small area of the total lunar surface one specific type of dome is characterized 1 by steep slopes 2 by a high albedo similar to lunar highlands and 3 by a strong absorption in the ultraviolet because of this latter feature they appear spectrally red and therefore were termed red spots their morphology suggests that these domes were created by much more viscous silica rich lava also red spots which are believed to be possibly volcanic in origin are associated with light plains materials in order to constrain the formation of these presumed volcanic features in context with the formation of the surrounding mare and highland materials we carried out 1 geologic and morphologic mapping of high resolution lunar orbiter iv and apollo 16 frames and 2 measurements of superimposed crater frequencies on geologic units in order to assess stratigraphy and geological history in the following two volcanic provinces in which red spots occur 1 the hansteen region dominated by the dome hansteen also known as the arrowhead and 2 the helmet region dominated by light plains possibly of volcanic origin such as the feature called the helmet and darney and the southern montes riphaeus in the hansteen region the dome hansteen postdates craters billy 3 88 ga and hansteen 3 87 ga but predates most of the mare materials 3 51 ga cratering model ages of the dome range from 3 74 to 3 65 ga placing its major activity as extending into the late imbrian in the helmet region presumed highland volcanism associated with red spots started in the nectarian with darney 3 94 ga cratering model ages measured on the helmet light plains range from 3 8 to 2 08 ga the origin of these light plains and local resurfacing processes in this unit however highland volcanism or impact remains an open question locally younger processes of eratosthenian or even copernican age such as emplacement of mare materials or mass wasting deposits could be dated in the higher resolution apollo 16 frame

thermal and magmatic evolution of the moon as with all science our continually developing concepts of lunar evolution are firmly tied to both new types of observations and the integration of these observations to the known pool of data this process invigorates the intellectual foundation on which old models are tested and new concepts are built just as the application of new observational tools to lunar science in 1610 galileo s telescope and 1840 photography yielded breakthroughs concerning the true nature of the lunar surface the computational and technological advances highlighted by the apollo and post apollo missions and associated scientific investigations provided a new view of the thermal and magmatic evolution of the moon 1 1 pre apollo view of the thermal and magmatic evolution of the moon many of the early views of the moon manifested in mythology and art throughout the world were primarily tied to lunar and terrestrial cycles and the relationships between the sun and the moon prophetically myths involving the lunar deities mwuetsi from zimbabwe and coyolxauhqui from mexico told of rather violent or catastrophic events in which the moon was expunged from the earth numerous ancient scientific observations were made about the nature of the moon ranging from those uncovered in early neolithic sites that correctly identified mare crisium and mare humorum to the insights made by greek philosophers such as anaxagoras ca 500 428 b c and democritus ca 460 370 b c who attached terrestrial analogues to its character stone mountains with the advent of the telescope 1610 and photography 1840 as scientific tools for lunar exploration semiquantitative data could be collected that would provide an intellectual foundation for scientific interpretation initially modern terrestrial geological analogs were extended to the moon lunar highlands volcanic craters seas combined with the rigors of computational modeling these observational data were extended to predict the original thermal state of the moon and its thermal and magmatic history its proximity to the earth

space weathering on airless planetary bodies clues from the lunar mineral hapkeite physical and chemical reactions occurring as a result of the high velocity impacts of meteorites and micrometeorites and of cosmic rays and solar wind particles are major causes of space weathering on airless planetary bodies such as the moon mercury and asteroids these weathering processes are responsible for the formation of their regolith and soil we report here the natural occurrence of the mineral hapkeite a fe2si phase and other associated fe si phases iron silicides in a regolith breccia clast of a lunar highland meteorite these fe si phases are considered to be a direct product of impact induced vapor phase deposition in the lunar soil all part of space weathering we have used an in situ synchrotron energy dispersive single crystal x ray diffraction technique to confirm the crystal structure of hapkeite as similar to the structure of synthetic fe2si this mineral hapkeite is named after bruce hapke of the university of pittsburgh who predicted the presence and importance of vapor deposited coatings on lunar soil grains some 30 years ago we propose that this mineral and other fe si phases are probably more common in the lunar regolith than previously thought and are directly related to the formation of vapor deposited nanophase elemental iron in the lunar soils

the lunar crust global structure and signature of major basins new lunar gravity and topography data from the clementine mission provide a global bouguer anomaly map corrected for the gravitational attraction of mare fill in mascon basins most of the gravity signal remaining after corrections for the attraction of topography and mare fill can be attributed to variations in depth to the lunar moho and therefore crustal thickness the large range of global crustal thickness 20 120 km is indicative of major spatial variations in melting of the lunar exterior and or significant impact related redistribution the 61 km average crustal thickness constrained by a depth to moho measured during the apollo 12 and 14 missions is preferentially distributed toward the farside accounting for much of the offset in center of figure from the center of mass while the average farside thickness is 12 km greater than the nearside the distribution is nonuniform with dramatic thinning beneath the farside south pole aitken basin with the global crustal thickness map as a constraint regional inversions of gravity and topography resolve the crustal structure of major mascon basins to half wavelengths of 150 km in order to yield crustal thickness maps with the maximum horizontal resolution permitted by the data the downward continuation of the bouguer gravity is stabilized by a three dimensional minimum slope and curvature algorithm both mare and non mare basins are characterized by a central upwarped moho that is surrounded by rings of thickened crust lying mainly within the basin rims the inferred relief at this density interface suggests a deep structural component to the surficial features of multiring lunar impact basins for large 300 km diameter basins moho relief appears uncorrelated with diameter but is negatively correlated with basin age in several cases it appears that the multiring structures were out of isostatic equilibrium prior to mare emplacement suggesting that the lithosphere was strong enough to maintain their state of stress to the present

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

lunar gruithuisen and mairan domes rheology and mode of emplacement characteristics of the domes to estimate the yield strengths 10 5 pa plastic viscosities 10 9 pa s and effusion rates 50 m 3 s of the magmas which formed them these values are similar to those of terrestrial rhyolites dacites and basaltic andesites and support the hypothesis that these domes are an unusual variation of typical highlands and mare compositions the dikes which formed them are predicted to have had widths of 50 m and lengths of about 15 km the magma rise speed implied by this geometry is very low 7 10 5 m s and the reynolds number of the motion is 2 10 8 implying a completely laminar flow regime estimates of emplacement duration range from one to several decades these new calculations confirm the unusual nature of these features and support previous qualitative suggestions that they were formed from magmas with significantly higher viscosity than those typical of mare basalts index terms 5480 planetology solid surface planets volcanism 8450 5410 planetology solid surface planets composition 5460 planetology solid surface planets physical properties of materials 8429 volcanology lava rheology and morphology keywords moon volcanism domes

rock types of south pole aitken basin and extent of basaltic volcanism the enormous pre nectarian south pole aitken spa basin represents a geophysically and compositionally unique region on the moon we present and analyze the mineralogical diversity across this basin and discuss the implications for basin evolution rock types are derived from clementine multispectral data based on diagnostic characteristics of ferrous absorptions in fresh materials individual areas are characterized as noritic dominated by low ca pyroxene gabbroic basaltic dominated by high ca pyroxene feldspathic 3 6 feo and olivine gabbro dominated by high ca pyroxene and olivine the anorthositic crust has effectively been removed from the interior of the basin the style of volcanism within the basin extends over several 100 myr and includes mare basalt and pyroclastic deposits several areas of ancient pre orientale volcanism or cryptomaria have also been identified the nonmare mafic lithology that occurs across the basin is shown to be noritic in composition and is pervasive laterally and vertically we interpret this to represent impact melt breccia deposits derived from the lower crust a few localized areas are identified within the basin that contain more diverse lithologies gabbro olivine gabbro some of which may represent material from the deepest part of the lower crust and perhaps uppermost mantle involved in the spa event

nature of local magma storage zones and geometry of conduit systems below basaltic eruption sites pu u o o kilauea east rift hawaii example the fluid dynamics of the well documented eruptive episodes at pu u o o kilauea wolfe et at 1987 are used to investigate quantitativeely the size and shape of the shallow conduit system beneath the vent cooling calculations are employed to study the long term survival of conduits and the consequences of multiple dike injection events we find that the subvent conduit must have a planar geometry at depths greater than a few tens to at most a few hundreds of meters with a width of less than a few meters a length of the order of 100 m and a height of the order of 1 kin this structure is clearly the residue of the preeruption dikes although such a feature can be widened somewhat by repeated dike emplacement events there is no evidence to suggest that a larger and much more equant magma reservoir should develop at shallow depth the extensive degassing often occurring after single eruptions or between repeated eruptions previously thought to imply the presence of a large equidimensional shallow magma chamber can be readily explained by the volume of magma in a dikelike subvent planar magma storage zone on the basis of these observations which we infer to apply commonly to basaltic eruption sites we suggest that the terms chamber or reservoir be used with caution because they most often connote a relatively large equant magma body distinct from the feeder dike lying just below the vent we find that the subvent region has the same basic geometric characteristics as the parental dike and we propose that it be referred to as a planar magma storage zone

genesis of flood basalts and basin and range volcanic rocks from steens mountain to the malheur river gorge oregon the middle and south forks of the malheur river provide a unique mapping corridor connecting two flood basalt successions steens basalt to the south and the basalt of malheur gorge to the north each contains chemically defined subtypes which merge stratigraphically across the north south length of the map area the lowermost flows of steens basalt are stratigraphically equivalent to the lowermost flows of the basalt of malheur gorge the uppermost flows of steens basalt pinch out in the map area but are partly interbedded with the middle and uppermost flows of the basalt of malheur gorge which continue to thicken northward the upper part of the tholeiitic succession is interbedded with a group of previously unrecognized lavas the venator ranch basalt flows tholeiitic volcanism ceased at ca 15 3 ma the last tholeiitic unit erupted is the hunter creek basalt which also thickens northward subsequent younger than 15 3 ma more localized eruptions were dominated by calc alkaline to mildly alkaline lavas associated with basin and range extension local uplift generated deep canyons which were filled by andesitic lavas of the keeney sequence ca 13 10 ma the final eruptive products include the devine canyon tuff ca 9 7 ma the drinkwater basalt ca 6 9 ma and the voltage flow older than 32 000 yr b p major and trace element analyses demonstrate that 1 crystal fractionation was a universal process in the derivation of the

frictional properties and slip stability of active faults within carbonate evaporite sequences the role of dolomite and anhydrite seismological observations show that many destructive earthquakes nucleate within or propagate through thick sequences of carbonates and evaporites for example along the apennines range italy carbonate and evaporite sequences are present at hypocentral depths for recent major earthquakes 5 0 mw 6 3 however little is known about the frictional properties of these rocks which are dominated by dolomite and anhydrite and differ from typical quartzofeldspathic rocks here we report on laboratory experiments designed to illuminate friction constitutive properties and associated microstructures of anhydrite and dolomite fault rocks we performed frictional sliding experiments on powdered samples for a range of normal stresses n from 10 to 150 mpa and sliding velocities from 1 to 300 m s experiments employed the double direct shear configuration and were conducted both dry at room temperature and water saturated at 75 c under true triaxial stresses at 25 c sliding friction is 0 65 for all samples and conditions studied at 75 c samples develop cohesive strength and sliding friction ranges from 0 4 to 0 5 for n from 10 to 35 mpa velocity step tests were used to assess rate state frictional behavior at 25 c the slip behavior is velocity strengthening neutral for all samples microstructural observations indicate localized deformation on r1 riedel and incipient y shear planes with marked grain size reduction at 75 c and larger strain we find that rate state friction behavior correlates with velocity dependent layer dilation and compaction and this is associated with the development of through going y shear planes we conclude that elevated temperature strain and the presence of pore fluids enhance shear localization into continuous y shear planes which could promote frictional instability at seismogenic depth within dolomite anhydrite sequences

compositional gradients across mare highland contacts importance and geological implication of lateral transport observations of mixing across mare highland contacts using high resolution clementine data allow a new assessment of the relative importance of vertical versus lateral mass transport on the moon at least at mare highland contact we analyze mare highland contacts in the grimaldi orientale and fecunditatis basins and tsiolkovsky crater through image based nonlinear spectral mixture modeling of clementine ultraviolet visible uv vis light spectrometer multi spectral data the mare in these regions differ in ages but they are characterized by having simple geological contacts the symmetric distribution of mare and highland soil constituents across their geological contact indicates that lateral transport is more efficient than deep vertical transport during the formation of the observed mixing zones observations across the lunar limb with the clementine uv vis filters show that there is a stray light component of scattered light across high contrast albedo boundaries however the magnitude and spatial properties of scattered light do not significantly affect the nature of compositional boundaries determined here since repetitive meteorite bombardment governs lateral transport across the geological contacts and is a random process a stochastic model is developed to describe this lateral transport analysis of the power decay law for crater ejecta thickness indicates that the high velocity ejecta travels long distances and follows a 3 power decay law this results in an infinite variance which requires an anomalous diffusion model since a classical diffusion model would be invalid mathematical modeling supports this result where it is shown that classical diffusion produces a relatively poor fit to profiles of material abundance while the anomalous diffusion model fits the profiles adequately these results indicate that high velocity ejecta dominates the formation of the observed compositional gradients while the ejecta near the crater rim is relatively less important on the basis of these ejecta distributions and the assumption of random impact cratering we derive a relationship that can be used as an index for relative age dating of geological contacts as well as for investigating cratering rates

remote compositional analysis of lunar olivine rich lithologies with moon mineralogy mapper m3 spectra 1 a systematic approach for deconvolving remotely sensed lunar olivine rich visible to near infrared vnir reflectance spectra with the modified gaussian model mgm is evaluated with chandrayaan 1 moon mineralogy mapper m3 spectra whereas earlier studies of laboratory reflectance spectra focused only on complications due to chromite inclusions in lunar olivines we develop a systematic approach for addressing through continuum removal the prominent continuum slopes common to remotely sensed reflectance spectra of planetary surfaces we have validated our continuum removal on a suite of laboratory reflectance spectra suites of olivine dominated reflectance spectra from a small crater near mare moscoviense the copernicus central peak aristarchus and the crater marius in the marius hills were analyzed spectral diversity was detected in visual evaluation of the spectra and was quantified using the mgm the mgm derived band positions are used to estimate the olivine s composition in a relative sense spectra of olivines from moscoviense exhibit diversity in their absorption features and this diversity suggests some variation in olivine fe mg content olivines from copernicus are observed to be spectrally homogeneous and thus are predicted to be more compositionally homogeneous than those at moscoviense but are of broadly similar composition to the moscoviense olivines olivines from aristarchus and marius exhibit clear spectral differences from those at moscoviense and copernicus but also exhibit features that suggest contributions from other phases if the various precautions discussed here are weighed carefully the methods presented here can be used to make general predictions of absolute olivine composition fe mg content

integrated spectral analysis of mare soils and craters applications to eastern nearside basalts abstract high spatial resolution clementine images are examined to measure the reflectance properties of small and optically immature mare craters that have sampled discrete compositional units the spectral properties of these relatively crystalline mare materials are compared to associated mature soils to determine the effects of space weathering on specific basalt types space weathering is observed to alter the optical properties of distinct lunar basalt units in a systematic manner allowing compositional distinctions to be recognized across maturity states ultraviolet visible reflectance properties of mare basalts are sensitive to titanium content but are relatively independent of maturity state and demonstrate only a slight reddening as regoliths mature to soils other compositional distinctions between basalt types are identified by differences in albedo and band strength of ferrous minerals that are maintained over a full range of maturity states immature deposits within large craters are compared to the spectral properties of well defined mare units to examine the composition of buried materials when craters excavate through the mare highland contamination is readily identified as a mixing relation between mafic and feldspathic lithologies the approach presented here provides new information on the composition and stratigraphy of several nearside mare deposits including the identification of thin low iron and very low titanium basalts in lacus somniorum and more iron rich low titanium basalts in eastern mare frigoris

cratering history and lunar chronology the moon is exceptional and important because it is the only planetary body besides the earth for which we have both a detailed stratigraphic history and datable rock samples that can be related to specific geomorphologic units fig 5 1 the moon has preserved much of its magmatic and impact record of at least the last 4 billion years while its endogenic history is of great interest for the fundamentals of planetary interiors and surfaces the moon has become a calibration plate for the cratering record of the earth moon system and by extrapolation of the entire inner solar system if one assumes a heliocentric origin for impactor populations these populations range from asteroids through long and short period comets to interplanetary dust and cover a size range from hundreds of kilometers to micrometers figure 5 1 telescopic view of the nearside of the earth s moon with landing sites of the apollo and luna missions this chapter reviews the presently available data sets in support of this paradigmatic assumption as follows 1 the phenomenology of lunar impact craters 2 the terrestrial record of the impact cratering process and the interpretation of terrestrial impactites as far as this ground truth is relevant for the interpretation of lunar impact craters and datable lunar impact breccias and melt rocks 3 the theory and numerical simulation of the cratering process and the characteristics of the earth moon crossing population of impactors asteroids and comets 4 the principles of relative age dating of lunar surface units and the general lunar stratigraphy 5 the stratigraphic significance and ages of lunar samples impactites and basalts and based on this data set the absolute ages of lunar surface units 6 the cratering rate of the moon as a function of time and 7 the time calibration of this cratering rate based on the

lunar mare deposits associated with the orientale impact basin new insights into mineralogy history mode of emplacement and relation to orientale basin evolution from moon mineralogy mapper m3 data from chandrayaan 1 1 moon mineralogy mapper m3 image and spectral reflectance data are combined to analyze mare basalt units in and adjacent to the orientale multiring impact basin models are assessed for the relationships between basin formation and mare basalt emplacement mare basalt emplacement on the western nearside limb began prior to the orientale event as evidenced by the presence of cryptomaria the earliest post orientale event mare basalt emplacement occurred in the center of the basin mare orientale and postdated the formation of the orientale basin by about 60 100 ma over the next several hundred million years basalt patches were emplaced first along the base of the outer rook ring lacus veris and then along the base of the cordillera ring lacus autumni with some overlap in ages the latest basalt patches are as young as some of the youngest basalt deposits on the lunar nearside m3 data show several previously undetected mare patches on the southwestern margins of the basin interior regardless the previously documented increase in mare abundance from the southwest toward the northeast is still prominent we attribute this to crustal and lithospheric trends moving from the farside to the nearside with correspondingly shallower density and thermal barriers to basaltic magma ascent and eruption toward the nearside the wide range of model ages for orientale mare deposits 3 70 1 66 ga mirrors the range of nearside mare ages indicating that the small amount of mare fill in orientale is not due to early cessation of mare emplacement but rather to limited volumes of extrusion for each phase during the entire period of nearside mare basalt volcanism this suggests that nearside and farside source regions may be similar but that other factors such as thermal and crustal thickness barriers to magma ascent and eruption may be determining the abundance of surface deposits on the limbs and farside the sequence timing and elevation of mare basalt deposits suggest that regional basin related stresses exerted control on their distribution our analysis clearly shows that orientale serves as an excellent example of the early stages of the filling of impact basins with mare basalt

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

determining provenance of marine metal pollution in french bivalves using cd zn and pb isotopes abstract cadmium zn and pb isotopic compositions mc icp ms and elemental concentrations hr icp ms have been used to distinguish between natural and anthropogenic sources of these metals in bivalves collected from the coastlines of france english channel atlantic and mediterranean coasts the cd isotopic signatures 114cd 1 08 to 0 52 exhibited by bivalves from the coastlines of france excluding those from ne france are within the range of those exhibited by bivalves from the usa east coast 114cd 1 20 to 0 54 this indicates the high prevalence of industry as well as the low natural contributions of cd from north atlantic waters in both regions thus the significance of anthropogenic cd sources is similar these significant anthropogenic contributions are identified for bivalves with a large range in tissue cd concentrations importantly french bivalves from the gironde estuary and marennes oleron basin regions of historic and modern importance for oyster farming respectively exhibited the highest cd levels of the study their cd isotopic signatures indicate historical smelting emissions remain the primary cd source despite the cessation of local smelting activities in 1986 and subsequent remedial efforts no significant variability is observed in the 66zn values of the french bivalves 0 53 with the exception of the much heavier compositions exhibited by oysters from the polluted gironde estuary 1 19 1 27 lead isotopes do not fractionate during processing like cd and zn they can therefore be used to identify emissions from industrial processes and the consumption of unleaded gasoline and diesel fuel as metal sources to french bivalves cadmium and zn isotopes are successfully used here as tracers of anthropogenic processing emissions and are combined with pb isotope fingerprinting techniques to identify metal sources

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

gravitational differentiation due to initial chemical stratification origin of lunar asymmetry by the creep of dense kreep abstract models for the evolution of the moon must explain a number of important characteristics of its magmatic history primary among them is the emplacement of mare basalts primarily on one side of the moon and in a region of the surface roughly correlating with that containing high subsurface concentrations of kreep it is thus important to explore mechanisms which will regionally concentrate a kreep layer early in lunar evolution and which 400 500 myr later give rise to mare basalt generation beneath the same region gravitational instability of a chemically dense ilmenite rich cumulate created during the fractionation of an anorthositic crust is one candidate model if so gravitational instability must occur at long wavelength to explain the hemispheric asymmetry we examine the rayleigh taylor instability of a dense layer near the surface of a sphere representing the lunar mantle in which the viscosity varies with depth our results show that spherical harmonic degree 1 is the fastest growing wavelength of instability if the viscosity of the dense layer is sufficiently low relative to that of the deeper mantle or if the viscosity of the mantle increases with depth however the viscosity increase cannot be distributed over a depth that is too large we explore whether a residual kreep like layer near the base of anorthositic crust might give rise to these needed conditions

impacts do not initiate volcanic eruptions eruptions close to the crater many papers on meteorite impact suggest that large impacts can induce volcanic eruptions through decompression melting of the underlying rocks we perform numerical simulations of the impact of an asteroid with a diameter of 20 km striking at 15 km s 1 into a target with a near surface temperature gradient of 13 k km 1 cold case or 30 k km 1 hot case the impact creates a 250 300 km diameter crater with 10 000 km3 of impact melt however the crater collapses almost flat and the pressure field returns almost to the initial lithostat even an impact this large cannot raise mantle material above the peridotite solidus by decompression statistical considerations also suggest that impacts cannot be the common initiator of large igneous provinces any time in post heavy bombardment earth history

galileo imaging observations of lunar maria and related deposits the galileo spacecraft imaged parts of the western limb and far side of the moon in december 1990 ratios of 0 41 0 56 gin filter images from the solid state hnaging ssi experiment provided information on the titanium content of mare deposits ratios of the 0 76 0 99 gm images indicated 1 gin absorptions associated with fe 2 in mafic minerals mare ages were derived froin crater statistics obtained from lunar orbiter images results on mare coinpositions in western oceanus procellarum and the humorurn basin are consistent with previous earth based observations thus providing confidence in the use of galileo data to extract compositional information mare units in the grimaldi and riccioli basins range in age froin 3 25 to 3 48 ga and consist of medium to medium high titanium 4 to 7 tio2 content lavas the schiller zucchius basin shows a higher 0 76 0 99 gm ratio than the surrounding highlands indicating a potentially higher mafic mineral content consistent with previous interpretations that the area includes mare deposits blanketed by highland ejecta and light plains materials the oldest mare materials in the orientale basin occur in south central mare orientale and are 3 7 ga old youngest mare materials are in lacus autumni and are 2 85 ga old these units are medium to medium high titanium 4 to 7 tio2 basalts thus volcanism was active in orientale for 0 85 ca but lavas were relatively constant in composition galileo data suggest that mendel rydberg mare is similar to mare orientale cryptomare are present as well thus the mare lavas on the western limb and far side to 178oe are remarkably uniform in coinposition being generally of medium to medium high titanium content and having relatively low 0 76 0 99 gin ratios this region of the moon is between two postulated large impact structures the procellarum and the south pole aitken basins and may have a relatively thick crust in areas underlain by an inferred thinner crust i e zones within large basins as at apollo titanium content is often higher however no mare deposits with titanium abundances approaching those of the high titanium 9 to 14 tio2 apollo 11 and 17 basalts nor of the high titanium regions of central oceanus procellarum are seen on the western limb or eastern far side light plains deposits are generally indistinct froin the surrounding highlands in the ssi data and are inferred to be derived primarily from the same material that forins the highlands some of the light plains are too young to be related to basin forming impacts suggesting possible volcanic origin dark mantle deposit compositions derived from ssi data are consistent with earth based observations of similar near side deposits and are interpreted to be pyroclastic materials however the modernitc albedo and 1 gin absorption of the dark mantle deposit on the southwest margin of the orientale basin suggest it is a local pyroclastic deposit contaminated with underlying highland materials from the orientale impact

the mineralogy of late stage lunar volcanism as observed by the moon mineralogy mapper on chandrayaan 1 1 the last major phases of lunar volcanism produced spectrally unique high titanium basalts on the western nearside of the moon the moon mineralogy mapper m3 on chandrayaan 1 has provided detailed measurements of these basalts at spatial and spectral resolutions necessary for mineralogical interpretation and mapping of distinct compositional units the m3 imaging spectrometer acquired data in 85 spectral bands from 430 to 3000 nm at 140 to 280 m pixel in its global mapping mode during the first half of 2009 reflectance data of several key sites in the western maria were also acquired at higher spatial and spectral resolutions using m3 s target mode prior to the end of the chandrayaan 1 mission these new observations confirm that both fresh craters and mare soils within the western high ti basalts display strong 1 m and weak 2 m absorptions consistent with olivine rich basaltic compositions the inferred abundance of olivine is observed to correlate with stratigraphic sequence across different mare regions and absolute ages the apparent stratigraphic evolution and fe rich compositions of these basalts as a whole suggest an origin from evolved residual melts rather than through the assimilation of more primitive olivine rich sources mare deposits with spectral properties similar to these late stage high ti basalts appear to be very limited outside the procellarum imbrium region of the moon and where present appear to occur as small areas of late stage regional volcanism detailed analyses of these new data and supporting measurements are in progress to provide further constraints on the mineralogy olivine abundance and compositions of these final products of lunar volcanism and the nature and evolution of their source regions

a reassessment of the emplacement and erosional potential of turbulent low viscosity lavas on the moon we have reevaluated the role of thermal erosion by low viscosity lunar lavas as a mechanism for the formation of the lunar sinuous rules we have adapted the model of williams et al 1998 and used the compositions of an apollo 12 basalt and a terrestrial komatiitic basalt to investigate the compositional and environmental effects on the flow behavior of low viscosity lavas on the moon and the earth our model predicts that lunar lavas could have erupted as turbulent flows that were capable of flowing hundreds of kilometers on a sufficiently flat unobstructed substrate these results are consistent with previous studies modeling of lavas over a substrate of the same composition shows that thermal erosion rates would have been low 10 cm d 1 as a result long duration eruptions approximately months to years would have been required to incise deep tens to hundreds of meters channels partial melting and mechanical removal of the substrate a mechanism suggested by hulme 1973 to enhance erosion only slightly increases thermal erosion rates other factors such as higher flow rates or lava superheating could have produced deep rules by thermal erosion during shorter duration eruptions a superheated lunar lava not only would have had a higher erosion rate 40 cm d 1 but also would have remained uncrusted for tens of kilometers which is consistent with the open channel morphology of most sinuous rules for lunar lavas with large volatile i e vesicle contents the presence of vesicles would have tended to increase viscosity at low strain rates resulting in shorter turbulent flow distances lower thermal erosion rates and thus shallower erosion channel depths for given eruption durations