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 competition between thermal contraction and differentiation in the stress history of the moon the scarcity of both extension and compression features on the moon strongly constrains the history of the lunar radius to variations of less than 1 km over the past 3 8 gyr this limit has traditionally been interpreted as requiring a delicate balance between thermal contraction of the near surface and expansion of a substantial cold interior region recent theories of lunar origin e g giant impact in contrast favor a hot initial state we propose that a reconciliation may be possible by taking account of the volume change v v d due to differentiation we calculate stp densities based on simplified normative mineralogies for a suite of estimates of the bulk lunar composition of primary lunar basalt and of the residuum left when the maximum amount of the latter is extracted from the former typically v v d 2 to 5 an expansion equivalent to heating by 10 3 k provided the timing of differentiation is correct one might offset the cooling of a magma ocean as much as 630 km deep by differentiation of the remainder of the moon which need not start much below the solidus temperature a large but not impossible amount of gabbroic melt production is implied 100 times the volume of mare basalts known to have been extruded we do not address the detailed genetic relationship of this melt to the basalts observed on the lunar surface but point out that it need not have reached the surface directly or even have entered the crust in order for the expansion to have occurred to assess the timing of melt formation we investigate a simple conductive lunar thermal model which takes account of both v v d and thermal contraction our initial state is characterized by a central temperature t c and a depth z 0 above which the material derived from the magma ocean is already at the solidus and is not suceptible to volume changes upon further differentiation we find a range of models satisfying the limits on radius increase and decrease the hottest has t c 1210 k z 0 400 km without v v d we would need a larger or colder or both core e g t c 700 k for z0 200 400 km in agreement with previous investigators our modeling thus lends credence to the idea that the moon could have been initially 50 molten with the remainder relatively close to the solidus and yet experienced little volume change over the last 3 8 gyr

investigating the origin of candidate lava channels on mercury with messenger data theory and observations received 12 april 2012 revised 31 august 2012 accepted 1 november 2012 published 31 march 2013 1 volcanic plains identified on mercury are morphologically similar to lunar mare plains but lack constructional and erosional features that are prevalent on other terrestrial planetary bodies we analyzed images acquired by the messenger spacecraft to identify features on mercury that may have formed by lava erosion we used analytical models to estimate eruption flux erosion rate and eruption duration to characterize the formation of candidate erosional features and we compared results with analyses of similar features observed on earth the moon and mars results suggest that lava erupting at high effusion rates similar to those required to form the teepee butte member of the columbia river flood basalts 0 1 1 2 10 6 m 3 s 1 would have been necessary to form wide valleys 15km wide observed in mercury s northern hemisphere first by mechanical erosion to remove an upper regolith layer then by thermal erosion once a lower rigid layer was encountered alternatively results suggest that lava erupting at lower effusion rates similar to those predicted to have formed rima prinz on the moon 4400 m 3 s 1 would have been required to form via thermal erosion narrower channels 7km wide observed on mercury although these results indicate how erosion might have occurred on mercury the observed features may have formed by other processes including lava flooding terrain sculpted during the formation of the caloris basin in the case of the wide valleys or impact melt carving channels into impact ejecta in the case of the narrower channels citation hurwitz d m j w head p k byrne z xiao s c solomon m t zuber d e smith and g a neumann 2013 investigating the origin of candidate lava channels on mercury with messenger data theory and observations j geophys res planets 118 471 486 doi 10 1029 2012je004103

ferrovolcanism iron volcanism on metallic asteroids metallic asteroids the exposed cores of disrupted planetesimals are expected to have been exposed while still molten some would have cooled from the outside in crystallizing a surface crust which would then grow inward because the growing crust is expected to be more dense than the underlying melt this melt will tend to migrate toward the surface whenever it is able compressional stresses produced in the crust while it cools will be relieved locally by thrust faulting which will also provide potential conduits for melt to reach the surface we predict iron volcanism to have occurred on metallic asteroids as they cooled and discuss the implications of this process for both the evolution and the modern appearance of these bodies

lithological mapping of central part of mare moscoviense using chandrayaan 1 hyperspectral imager hysi data abstract we conducted spectral analysis of central region of the mare moscoviense area on the far side of the moon using the hyperspectral imager hysi data from the chandrayaan 1 mission in an effort to identify and map the major lithological units present in the area various spectral band parameters namely band curvature band tilt and band strength have been used for lithological discrimination based on the nature of the spectral profile these band parameters essentially measure the shape position and strength of the absorption feature near 1000 nm arising due to electronic transition of fe 2 in crystallographic sites of major rock forming silicates spectral band parameters have been used for generating rock type composite image based on spectral studies and rock type composite image as obtained using band parameters five major compositional units have been identified highland basin soils ancient mature mare highland contaminated mare buried unit with abundant low ca pyroxene lcp and youngest mare unit in the present study a multispectral approach in the form of spectral band parameters has been adopted for analysing the hysi hyperspectral data from chandrayaan 1 mission present study clearly shows that the spectral band parameters obtained using selected hysi channels could efficiently be used to discriminate and delineate the major litho units present across the central part of mare moscoviense and the same approach can thus be used for lithological mapping of other parts of lunar surface using hysi data

absence of large shield volcanoes and calderas on the moon consequence of magma transport phenomena large shield volcanoes and calderas are not observed on the moon theoretical assessments show that melt ascending from the mantle will stall at rheological traps or at the shallower density trap at the base of the low density lunar crust magma will then only reach the surface along dikes propagated from these deep reservoirs and such events will be infrequent and characterized by very large volume eruptions these conditions favor the formation of sinuous rules single long flows and widespread flow units rather than abundant small eruptions from a central edifice the absence of large shield volcanoes and calderas on the moon is interpreted to be related to the fact that shallow neutral buoyancy zones and magma reservoirs are not favored on the moon

compositional variations in the vicinity of the lunar crust mantle interface from moon mineralogy mapper data moon mineralogy mapper spectroscopic data were used to investigate the mineralogy of a selection of impact craters central peaks or peak rings in order to characterize the lunar crust mantle interface and assess its lateral and vertical heterogeneity the depth of origin of the craters central peaks or peak rings was calculated using empirical equations and compared to gravity recovery and interior laboratory crustal thickness models to select craters tapping within 10 20 km of the crust mantle interface our results show that plagioclase is widely detected including in craters allegedly sampling lower crustal to mantle material except in central peaks where low calcium pyroxene was detected olivine detections are scarce and identified in material assumed to be derived from both above and below the crust mantle interface mineralogical detections in central peaks show that there is an evolution of the pyroxene composition with depth that may correspond to the transition from the crust to the mantle the correlation between high calcium pyroxene and some pyroxene dominated mixture spectra with the location of maria and cryptomaria hints at the existence of lateral heterogeneities as deep as the crust mantle interface

remote sensing and geologic studies of the schiller schickard region of the moon near infrared reflectance spectra multispectral images and photogeologic data for the schiller schickard ss region were obtained and analyzed in order to determine the composition and origin of a variety of geologic units these include light plains deposits orientale related deposits mare units and dark haloed impact craters dhcs spectral data indicate that the pre orientale highland surface was dominated by noritic anorthosite near ir spectra show that dhcs in the region have excavated ancient 3 8 ga mare basalts from beneath highland bearing material emplaced by the orientale impact ancient mare basalts were widespread in the ss region prior to the orientale event and their distribution appears to have been controlled by the presence of several old impact basins including the schiller zucchius basin and a basin previously unrecognized both near ir spectra and multispectral images indicate that light plains and other orientale related units in the ss region contain major amounts of local pre orientale mare basalt the amounts of local material in these deposits approach but seldom exceed the maximum values predicted by the local mixing hypothesis of oberbeck and co workers

mineralogy of the mafic anomaly in the south pole aitken basin implications for excavation of the lunar mantle the mineralogy of south pole aitken basin spa the largest confirmed impact basin on the moon is evaluated using five color images from clementine although olivine rich material as well as basalts rich in clinopyroxene are readily identified elsewhere on the farside the dominant rock type observed across the interior of spa is of a very noritic composition this mineralogy suggests that lower crust rather than the mantle is the dominant source of the mafic component at spa the lack of variation in observed noritic composition is probably due to basin formation processes during which extensive melting and mixing of target materials are likely to occur

evidence for basaltic volcanism on the moon within the past 100 million years the majority of basaltic volcanism on the moon occurred more than 3 billion years ago small mounded formations on the lunar nearside may be products of basaltic eruptions less than 100 million years ago suggesting a long decline of magmatic activity

lunar dark haloed impact craters origin and implications for early mare volcanism remote sensing and photogeologic data were used to determine the composition and origin of lunar dark haloed craters near infrared reflectance spectra were obtained for numerous dark haloed impact craters located on either the ejecta blankets of large impact craters or imbrian and nectarian age light plains deposits spectral thermal radar and photogeologic data conclusively demonstrate that copernicus h and other dark haloed craters on the ejecta blanket of copernicus excavated mare basalts from beneath lighter surface deposits rich in highlands material analyses of reflectance spectra of dark haloed craters on light plains indicate that in every instance these craters exposed mare basalt which had previously been covered by varying thicknesses of highlands debris in the schiller schickard region a relatively thick highlands unit was emplaced as a result of the orientale impact event on the interior of balmer basin marelike basalt has been excavated from beneath much thinner highlands deposits emplaced by nearby craters mafic orbital geochemical anomalies are commonly associated with regions with abundant light plains deposits which exhibit dark haloed impact craters apparently some mare material has been incorporated into the regolith either by local mixing during the emplacement of the highlands debris or by subsequent vertical mixing the results of recent remote sensing photogeologic and lunar sample studies strongly indicate that mare volcanism was a significant process during much of the pre imbrian and may have been initiated as early as 4 2 4 3 ga these very early volcanic episodes contributed materials to the lunar surface which were incorporated into the upper portion of the highlands crust by subsequent impact mixing models concerning the extent and duration of mare volcanism as well as those involving the composition and thermal evolution of the lunar interior will have to be revised

volcanic gas composition metal dispersion and deposition during explosive volcanic eruptions on the moon abstract the transport of metals in volcanic gases on the moon differs greatly from their transport on the earth because metal speciation depends largely on gas composition temperature pressure and oxidation state we present a new thermochemical model for the major and trace element composition of lunar volcanic gas during pyroclastic eruptions of picritic magmas calculated at 200 1500 c and over 10 9 10 3 bar using published volatile component concentrations in picritic lunar glasses we have calculated the speciation of major elements h o c cl s and f in the coexisting volcanic gas as the eruption proceeds the most abundant gases are co h 2 h 2 s cos and s 2 with a transition from predominantly triatomic gases to diatomic gases with increasing temperatures and decreasing pressures hydrogen occurs as h 2 h 2 s h 2 s 2 hcl and hf with h 2 making up 0 5 0 8 mol fractions of the total h water h 2 o concentrations are at trace levels which implies that h species other than h 2 o need to be considered in lunar melts and estimates of the bulk lunar composition the cl and s contents of the gas control metal chloride gas species and sulfide gas and precipitated solid species we calculate the speciation of trace metals zn ga cu pb ni fe in the gas phase and also the pressure and temperature conditions at which solids form from the gas during initial stages of the eruption elemental gases are the dominant metal species as the gas loses heat chloride and sulfide species become more abundant our chemical speciation model is applied to a lunar pyroclastic eruption model with isentropic gas decompression the relative abundances of the deposited metal bearing solids with distance from the vent are predicted for slow cooling rates 2 o co 2 and cl rich volcanic gas from erta ale volcano ethiopia as an analogy for more oxidized planetary eruptions in the terrestrial cl rich gas the metals are predominantly transported as chlorides as opposed to metallic vapors and sulfides in the lunar gas due to the presence of cl species metal transport is more efficient in the volcanic gas from erta ale compared to the moon

lunar topographic roughness maps from lunar orbiter laser altimeter lola data scale dependence and correlation with geologic features and units we present maps of the topographic roughness of the moon at hectometer and kilometer scales the maps are derived from range profiles obtained by the lunar orbiter laser altimeter lola instrument onboard the lunar reconnaissance orbiter lro spacecraft as roughness measures we used the interquartile range of profile curvature at several baselines from 115 m to 1 8 km and plotted these in a global map format the maps provide a synoptic overview of variations of typical topographic textures and utilize the exceptional ranging precision of the lola instrument we found that hectometer scale roughness poorly correlates with kilometer scale roughness because they reflect different sets of processes and time scales hectometer scale roughness is controlled by regolith accumulation and modification processes and affected by the most recent events primarily geologically recent 1 2 ga meteoritic impacts kilometer scale roughness reflects major geological impact volcanic and tectonic events in earlier geological history young large impact craters are rough and their roughness decreases with age the global roughness maps revealed a few unusually dense clusters of hectometer and decameter size impact craters that differ in their morphology and settings from typical secondary crater clusters and chains the origin of these features is enigmatic the maps can assist in the geological mapping of the lunar maria by revealing contacts between volcanic plain units the global roughness maps also clearly reveal cryptomaria old volcanic plains superposed by younger materials primarily crater and basin ejecta

mariner 10 multispectral images of the eastern limb and farside of the moon we present the first analysis of mariner 10 multispectral image data for the eastern limb and farside of the moon a new rigorous calibration of these data is used that provides results that are consistent with independently derived data sets from these newly calibrated data a color ratio image 0 48 0 58 m is produced to show relative tio2 abundances in mare units on the eastern limb and farside of the moon our results indicate that the farside lunar mare deposits examined have tio2 contents that are intermediate to low 2 5 tio2 relative to mare deposits on the nearside we find no evidence for areally extensive deposits of either very low titanium vlt or high to very high titanium vht basalts in these portions of the moon our findings support previous interpretations that the source regions for lunar mare basalts are laterally heterogeneous additionally examination of highland units reveals a relatively blue region that corresponds with a previously proposed cryptomare suggesting enhanced tio2 for this unit finally based on these mariner 10 data telescopic spectral data galileo multispectral image data and lunar meteorite analyses we speculate that volcanism in farside mare deposits did not include high titanium basalts 8 wt

magma source transition of lunar mare volcanism at 2 3 ga mare basalts provide insights into the composition and thermal history of the lunar mantle the ages of mare basalts suggest a first peak of magma activity at 3 2 3 8 ga and a second peak at 2 ga in this study we reassess the correlation between the titanium contents and the eruption ages of mare basalt units using the compositional and chronological data updated by selene kaguya using morphological and geological criteria we calculated the titanium content of 261 mare units across a representative area of each mare unit in the procellarum kreep terrane where the latest eruptions are located an increase in the mean titanium content is observed during the eratosthenian period as reported by previous studies we found that the increase in the mean titanium content occurred within a relatively short period near approximately 2 3 ga suggesting that the magma source of the mare basalts changed at this particular age moreover the high titanium basaltic eruptions are correlated with a second peak in volcanic activity near 2 ga the high titanium basaltic eruptions occurring during the last volcanic activity period can be explained by the three possible scenarios 1 the ilmenite bearing cumulate rich layer in the core mantle boundary formed after the mantle overturn 2 the basaltic material layers beneath the lunar crust formed through upwelling magmas and 3 ilmenite bearing cumulate blocks remained in the upper mantle after the mantle overturn

a compositional study of the aristarchus region of the moon using near infrared reflectance spectroscopy newly obtained near infrared reflectance spectra for features on or near the aristarchus plateau demonstrate the diversity of compositions in the region highland units are of three probable compositions a feldspar and clinopyroxene assemblage a probable clinopyroxene olivine and possibly feldspar assemblage and an assemblage composed of olivine or olivine and feldspar the feldspar clinopyroxene assemblage is tentatively correlated with the major th anomaly centered on aristarchus crater the regional pyroclastic deposits on the plateau are composed of greater than 90 fe2 bearing glass the aristarchus cratering event fully penetrated any mare or pyroclastics in the target evidence for mare related material is found in the ejecta on the mare side of the mare plateau contact

a comparison of volcanic eruption processes on earth moon mars io and venus the silicate planets and satellites display a wide range of physical chemical and atmospheric characteristics which may influence the nature of volcanism a major geological process common to the evolution of the surfaces of these bodies consideration of the process of magma ascent and eruption from first principles allows predictions to be made concerning volcanic eruption styles and expected landforms and deposits on each planetary body examination of actual land forms and deposits in light of these predictions leads to a better understanding of the nature of volcanic eruption processes and outlines outstanding problems

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

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

haze and cloud structure of saturn s north pole and hexagon wave from cassini iss imaging abstract in this paper we present a study of the vertical haze and cloud structure in the upper two bars of saturn s northern polar atmosphere using the imaging science subsystem iss instrument onboard the cassini spacecraft we focus on the characterization of latitudes from 53 to 90 n the observations were taken during june 2013 with five different filters vio bl1 mt2 cb2 and mt3 covering spectral range from the 420 nm to 890 nm in a deep methane absorption band absolute reflectivity measurements of seven selected regions at all wavelengths and several illumination and observation geometries are compared with the values produced by a radiative transfer model the changes in reflectivity at these latitudes are mostly attributed to changes in the tropospheric haze this includes the haze base height from 600 200 mbar at the lowest latitudes to 1000 300 mbar in the pole its particle number density from 20 2 particles cm3 to 2 0 5 particles cm3 at the haze base and its scale height from 18 0 1 km to 50 0 1 km we also report variability in the retrieved particle size distribution and refractive indices we find that the hexagonal wave dichotomizes the studied stratospheric and tropospheric hazes between the outer equatorward regions and the inner polar regions this suggests that the wave or the jet isolates the particle distribution at least at tropospheric levels

global occurrence trend of high ca pyroxene on lunar highlands and its implications we present details of the global distribution of high ca pyroxene hcp rich sites in the lunar highlands based on the global data set of hyperspectral reflectance obtained by the selene spectral profiler most hcp rich sites in the lunar highlands are found at fresh impact craters in each crater most of the detection points are distributed on the ejecta rim and floor of the impact craters rather than the central peaks while the central peaks are dominated by purest anorthosite pan this indicates that hcp rich materials originate from relatively shallower regions of the lunar crust than pan in addition while all ray craters with sizes larger than 40 km possess hcp rich materials small fresh craters with sizes less than 6 10 km do not indicating that the uppermost mixing layers in the lunar crust are not dominated by hcp based on these results we propose that in the upper lunar crust a hcp rich zone overlying the pan layer exists below the uppermost mixing layer this hcp rich zone may originate from interstitial melt during the formation of the flotation anorthositic cumulate while an impact ejecta origin impact melt origin and or magmatic intrusion into the upper lunar crust may also account for the occurrence of hcp rich sites in the highlands

remote sensing studies of the lomonosov fleming region of the moon 1 lomonosov fleming is a 620 km pre nectarian impact basin centered at 19 n 105 e clementine multispectral images and a variety of spacecraft photographs were used to investigate the composition and origin of geologic units in the region mare basalt deposits in the lomonosov fleming region are small and exhibit varying degrees of highlands contamination four previously unrecognized dark mantle deposits of probable pyroclastic origin were identified and mapped a major expanse of cryptomare was mapped in and around the lomonosov fleming basin spectral and chemical data obtained for dark haloed craters dhc established that these impact craters excavated mare basalt from beneath higher albedo highlands rich surface units the buried basalts exposed by dhcs in the region exhibit a variety of compositions which range from very low titanium basalt to intermediate tio2 mare basalt nectarian aged units with subjacent cryptomare are much more extensive than imbrian aged deposits with underlying basalt at least some of the buried mare basalts in the region may have been emplaced during pre nectarian time while both impact basins and craters played a role in cryptomare formation by transporting highlands material to mare surfaces the evidence indicates that most of the cryptomare inside the basin are of the distal basin ejecta type the enhanced feo and tio2 abundances exhibited by these cryptomare surfaces usually light plains units demonstrate that ballistic erosion and sedimentation played an important role in their formation

the 3 d geological model around chang e 3 landing site based on lunar penetrating radar channel 1 data high frequency lunar penetrating radar lpr data from an instrument on the lunar rover yutu from the chang e 3 ce 3 robotic lander were used to build a three dimensional 3 d geological model of the lunar subsurface structure the ce 3 landing site is in the northern mare imbrium more than five significant reflection horizons are evident in the lpr profile which we interpret as different period lava flow sequences deposited on the lunar surface the most probable directions of these flows were inferred from layer depths thicknesses and other geological information moreover the apparent imbrian paleoregolith homogeneity in the profile supports the suggestion of a quiescent period of lunar surface evolution similar subsurface structures are found at the nasa apollo landing sites indicating that the cause and time of formation of the imaged phenomena may be similar between the two distant regions

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

small scale density variations in the lunar crust revealed by grail abstract data from the gravity recovery and interior laboratory grail mission have revealed that 98 of the power of the gravity signal of the moon at high spherical harmonic degrees correlates with the topography the remaining 2 of the signal which cannot be explained by topography contains information about density variations within the crust these high degree bouguer gravity anomalies are likely caused by small scale 10 s of km shallow density variations here we use gravity inversions to model the small scale three dimensional variations in the density of the lunar crust inversion results from three non descript areas yield shallow density variations in the range of 100 200 kg m 3 three end member scenarios of variations in porosity intrusions into the crust and variations in bulk crustal composition were tested as possible sources of the density variations we find that the density anomalies can be caused entirely by changes in porosity characteristics of density anomalies in the south pole aitken basin also support porosity as a primary source of these variations mafic intrusions into the crust could explain many but not all of the anomalies additionally variations in crustal composition revealed by spectral data could only explain a small fraction of the density anomalies nevertheless all three sources of density variations likely contribute collectively results from this study of grail gravity data combined with other studies of remote sensing data and lunar samples show that the lunar crust exhibits variations in density by 10 over scales ranging from centimeters to 100 s of kilometers

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

high temperature silicon isotope geochemistry abstract silicon si is the defining element of silicate reservoirs yet despite its dominance in major earth processes there is still no clear understanding of how much is hosted in earth s core how the enriched continental crust forms or even if the crust is isotopically different from the mantle because of a long history of weathering erosion and subduction with the advent of multiple collector inductively coupled plasma mass spectrometry it has become relatively straightforward to explore small 100 ppm level mass dependent variations in si isotopic composition resulting from high temperature fractionation and to develop new isotopic fingerprints of magmatic processes and source regions this paper reviews the technique developments the new data and the veracity of current interpretations only a small si isotopic effect is associated with basalt formation via mantle melting however there now is compelling evidence based on a considerable number of samples 100 that the silicate earth is isotopically fractionated by 100 200 ppm per amu to a heavy composition relative to that of chondrites and also all differentiated stony meteorites this could reflect variability in the circumstellar disc but this is not well supported by data for enstatite chondrites which are isotopically light the most plausible current explanation is that si is a light element in earth s core and that differences in the bond stiffness between silicate and metal hosted si resulted in substantial fractionation interestingly the moon has the same si isotope composition as earth s mantle which is hard to explain unless the moon s atoms were mainly derived from earth differentiated magmatic sequences such as those of hekla iceland display a systematic relationship between isotopic composition and si content more complex magmatic suites such as i and s type granites reveal a range of isotopic compositions not well correlated with chemical composition similar effects are found in lower crustal granulite facies xenoliths nonetheless the overall composition of the continental crust is only slightly heavy relative to the mantle in fact the effect is barely resolvable therefore the amounts of surface dissolved heavy si removed to the mantle via weathering over time have been small or these losses have been balanced by subduction of isotopically light clay

remote sensing and geologic studies of the balmer kapteyn region of the moon 1 the balmer kapteyn b k region is located just east of mare fecunditatis on the east limb of the moon it is centered on the balmer kapteyn basin a pre nectarian impact structure that exhibits two rings approximately 225 km and 450 km in diameter clementine multispectral images and lunar prospector lp gamma ray spectrometer grs data were used to investigate the composition age and origin of geologic units in the region a major expanse of cryptomare was mapped within the b k basin spectral and chemical data obtained for dark haloed craters dhcs established that these impact craters excavated mare basalt from beneath higher albedo highland rich surface units the buried basalts exposed by dhcs in the region are dominated by low titanium mare basalts the fresh dhc feo values 15 0 15 7 wt that best represent those of buried mare basalts are well within the range of values exhibited by high alumina mare basalts while most cryptomare deposits occur beneath surfaces that range in age from imbrian to nectarian it is possible that some mare flows were emplaced during pre nectarian time most cryptomare deposits in the b k region were formed by the contamination of mare surfaces by highland rich distal ejecta from surrounding impact craters these balmer type cryptomare deposits are usually associated with light plains units major lp grs feo enhancements are associated with cryptomaria in the balmer kapteyn lomonosov fleming schiller schickard and mendel rydberg regions

lunar mare basalt flow units thicknesses determined from crater size frequency distributions accurate lava flow unit thicknesses estimates are necessary to place constraints on volcanic flux estimates we refine the technique of using the shape of crater size frequency distribution csfd curves to estimate the thickness of individual lunar mare flow units we find that a characteristic knee often observed in csfd curves is reasonably interpreted to represent the presence of two lava flow units separated in time and that the diameter at which this knee occurs is related to the thickness of the overlying flow unit examination of 58 curves with this characteristic knee in several lunar nearside basins oceanus procellarum imbrium tranquillitatis humorum cognitum nubium and insularum allowed us to identify flow units that have not been detected in low sun images we found that the range of flow unit thickness is 20 220 m and the average is 30 60 m this technique expands considerably the ability to assess lava flow unit thicknesses and volumes on the moon and planets

mineral chemistry and in situ upb geochronology of the mare basalt northwest africa 10597 implications for low ti mare volcanism around 3 0 ga abstract unbrecciated mare basalts are rare in the lunar meteorite collection found in 2015 northwest africa nwa 10597 is a medium grained low ti mare basalt with a subophitic texture the meteorite consists mostly of mm sized pyroxene and plagioclase with minor olivine spinel ilmenite phosphates silica and trace zr rich minerals such as baddeleyite zirconolite and tranquillityite a portion of plagioclase and silica has been transformed to their high pressure polymorphs due to shock metamorphism nwa 10597 has a low tio2 content 2 9 wt but is relatively enriched in rare earth elements ree laaverage 65 ci with an overall unfractionated pattern except for a negative eu anomaly calculated ree concentrations of parent melts in equilibrium with mg rich pyroxene and ca rich plagioclase suggest no significant assimilation of ree rich melts after the onset of pyroxene crystallization in situ u pb analyses of baddeleyite and apatite reveal a mutually consistent age of 3 0 ga which is also in excellent agreement with that of low ti mare basalts nwa 4734 and lapaz icefield lap 02205 dated with other independent techniques the concordance suggests no significant thermal disturbance in the u pb isotopic system of nwa 10597 although it was heavily shocked nwa 10597 closely resembles nwa 4734 in terms of petrographic texture mineral chemistry and geochronology indicating a pairing relationship

comparative radiocarbon dating of terrestrial plant macrofossils and aquatic moss from the ice free corridor of western canada in order to assess the reliability of aquatic moss for radiocarbon dating sup 14 c analyses were performed on a stratigraphic series of terrestrial plant macrofossils and samples of drepanocladus crassicostatus from a small hard water lake ph 8 2 in the ice free corridor of alberta all sup 14 c dating was done by using accelerator mass spectrometry mazama ash provided an independent chronological control the aquatic bryophyte samples consistently produced sup 14 c ages significantly older than the terrestrial macrofossils the relation between the radiocarbon dates from the macrofossils and the moss was not linear and age differences ranged from approximately 1400 to 6400 yr the sup 14 c content of d crassicostatus growing in the lake at present was less than 85 modern despite the apparent inability to take up sup 14 c deficient carbon by the direct incorporation of bicarbonate the bryophytes clearly do not provide reliable material sup 14 c dating the sup 14 c deficiency of aquatic mosses may be explained by the generation of sup 14 c deficient co sub 2 through isotopic exchange the formation of co sub 2 from bicarbonate by chemical processes and metabolic co sub 2 production these results demonstrate the potential unreliability of sup 14 c dates from aquatic mosses and raise serious concernsmore about the deglaciation dates from the ice free corridor that were obtained from aquatic drepanocladus less

a spectral survey of the crisium basin region of the moon the crisium basin region harbors a number of interesting features including geochemical and radar anomalies light plains units and possible hidden mare deposits cryptomaria this report presents preliminary results of a telescopic near infrared spectral study concerning a variety of surface units in the crisium region observations were made of mare crisium light plains deposits north of taruntius crater and the terra associated with the crisium basin

mare volcanism in the lunar farside moscoviense region implication for lateral variation in magma production of the moon 1 accurate estimates of the duration and volume of extrusive volcanism of the moon are essential for understanding the lunar thermal evolution here using new high resolution images obtained by the selene terrain camera we determined the thicknesses and ages of basalts in mare moscoviense one of the most prominent mare deposits on the farside mare volcanism in mare moscoviense was active for at least 1 5 ga following the formation of the moscoviense basin mare basalts are estimated to be at least 600 m thick corresponding to a total volume of 9 500 16 000 km 3 the long duration and large volume of extrusive volcanism are plausibly attributed to the thinner crust of the moscoviense basin relative to those of other farside basins from a comparison with mare volume within a same sized nearside basin we concluded that a magma production in the farside mantle was 3 10 times less than that of the nearside

the basalts of mare frigoris this paper discusses the methodology and results of a detailed investigation of mare frigoris using remote sensing data from clementine lunar prospector and lunar reconnaissance orbiter with the objective of mapping and characterizing the compositions and eruptive history of its volcanic units with the exception of two units in the west mare frigoris and lacus mortis are filled with basalts having low tio2 to very low tio2 low feo and high al2o3 abundances these compositions indicate that most of the basalts in frigoris are high al basalts a potentially undersampled yet important group in the lunar sample collection for its clues about the heterogeneity of the lunar mantle thorium abundances of most of the mare basalts in frigoris are also low although much of the mare surface appears elevated due to contamination from impact gardening with the surrounding high th imbrium ejecta there are however a few regional thorium anomalies that are coincident with cryptomare units in the east the two youngest mare basalt units and some of the scattered pyroclastic deposits and volcanic constructs in addition mare frigoris lies directly over the northern extent of the major conduit for a magma plumbing system that fed many of the basalts that filled oceanus procellarum as interpreted by andrews hanna et al 2014 using data from the gravity recovery and interior laboratory mission the relationship between this deep reaching magma conduit and the largest extent of high al basalts on the moon makes mare frigoris an intriguing location for further investigation of the lunar mantle

mare volcanism reinterpretation based on kaguya lunar radar sounder data the lunar radar sounder lrs onboard kaguya selene detected widespread horizontal reflectors under some nearside maria previous studies estimated that the depths of the subsurface reflectors were up to several hundreds of meters and suggested that the reflectors were interfaces between mare basalt units the comparison between the reflectors detected in the lrs data and surface age maps indicating the formation age of each basalt unit allows us to discuss the lower limit volume of each basalt unit and its space and time variation we estimated volumes of basalt units in the ages of 2 7 ga to 3 8 ga in the nearside maria including mare crisium mare humorum mare imbrium mare nectaris mare serenitatis mare smythii and oceanus procellarum the lower limit volumes of the geologic units estimated in this study were on the order of 103 to 104 km3 this volume range is consistent with the total amount of erupted lava flows derived from numerical simulations of thermal erosion models of lunar sinuous rille formation and is also comparable to the average flow volumes of continental flood basalt units formed after the paleozoic and calculated flow volumes of archean komatiite flows on the earth the lower limits of average eruption rates estimated from the unit volumes were on the order of 10 5 to 10 3 km3 yr the estimated volumes of the geologic mare units and average eruption rate showed clear positive correlations with their ages within the same mare basin while they vary among different maria compared within the same age range

magma reservoirs and neutral buoyancy zones on venus implications for the formation and evolution of volcanic landforms we examine the production of magma reservoirs and neutral buoyancy zones nbzs on venus and the implications of their development for the formation and evolution of volcanic landforms the high atmospheric pressure on venus reduces volatile exsolution and generally serves to inhibit the formation of nbzs and shallow magma reservoirs for a range of common terrestrial magma volatile contents magma ascending and erupting near or below mean planetary radius mpr should not stall at shallow magma reservoirs such eruptions would be characterized by relatively high total volumes and effusion rates for the same range of volatile contents at 2 km above mpr about half of the cases result in direct ascent of magma to the surface and half in the production of neutral buoyancy zones in general neutral buoyancy zones and shallow magma reservoirs begin to appear as gas content increases and are nominally shallower on venus than on earth for a fixed volatile content nbzs become deeper with increasing elevation over the range of elevations treated here 1 km to 4 4 km depths differ by a factor of 2 4 these analyses reveal several factors that may help to account for the low height of volcanoes on venus larger primary reservoirs cause the wide dispersal of conduits building edifices models of the position of the shallow nbz reservoir during edifice growth show that for earth the magma chamber center remains at a constant depth below the growing edifice summit thus keeping pace with the increasing elevation while on venus the chamber center becomes deeper relative to the summit of the growing edifice because of the major change in atmospheric pressure as a function of altitude therefore neutral buoyancy zones and magma reservoirs on venus will remain in the prevolcano substrate longer and in many cases may not emerge into the edifice at all the lower rate of vertical migration implies that magma reservoirs would tend to stabilize undergo greater lateral growth and become larger on venus than earth the proportion of the available magma going into production of the edifice relative to that intruded into the substrate is smaller on venus than earth large reservoirs would encourage multiple and more widely dispersed source vents and large volumes for individual eruptions in large reservoirs positively buoyant materials are likely to be produced from differentiation substrate remelting and volatile exsolution nonbuoyant materials exsolving volatiles in a shallow reservoir will need higher gas bubble concentrations to produce eruptions than on earth and when this gas enriched melt emerges at the surface it is more likely to retain its bubbles than to undergo explosive disruption due to the high surface atmospheric pressure therefore there is the potential for the production of a range of erupted lavas that have very high gas bubble concentrations leading to anomalous more viscous rheological properties inhibition of disruption of volatile rich magma for both basaltic and more evolved compositions can lead to the production of 1 more bubble rich vesicular flows characterized by higher viscosity and greater thicknesses the venus equivalent of effusions that would have lost much of their volatiles in the fire fountaining process on earth 2 high volume high discharge rate extremely gas rich basaltic effusions that increase viscosity considerably upon surface extrusion and produce domes whose volumes are considerably higher than their dense rock equivalent and 3 more evolved compositions that are gas rich but do not undergo disruption upon effusion and produce domes and flows of high viscosity the venus equivalent of terrestrial ignimbrites on the basis of these analyses we predict that intrusions and dike emplacement should be common particularly around both shallow and deep magma reservoirs and the tops of dikes should be manifested as radial fractures there should be a range of diameters of circular features associated with the presence of both shallow nbz related and deep plumerelated magma reservoirs large volume lava outpourings should be favored at lower elevations and shallow reservoirs and edifices should be more common at intermediate elevations at the highest elevations magma reservoirs are predicted to be large and relatively deep with low associated edifices direct ascent of magma where neutral buoyancy zones are unlikely low elevations and the propensity for relatively larger magma reservoirs on venus when they do form are both factors which will tend to favor high volume eruptions independent of variations in magma temperature or chemistry individual volcanic features should be interpreted in terms of regional geologic setting and the dynamics of elevation changes commonly associated with various scales of mantle processes and magma emplacement in order to assess global crustal growth processes on venus

petrologic province maps of the lunar highlands derived from orbital geochemical data orbital and sample geochemical data from the lunar highlands are combined in variation diagrams to determine a the coincidence between the two data sets and b the geologic validity of extrapolating observed diagrammatic relations to an image format we examined three variation diagrams mg 100 mg mg fe molar versus th ti c ratio normalized to chondrites al versus mg th ti c and fe versus th ti c for the orbital data within each diagram we establish a petrologic classification based on the data s clustering or coincidence with sample compositions or both the spatial distributions of each diagram s classes are shown as petrologic units on color coded classification maps the mg th ti c diagram which is similar to the mg sm ti c diagram that has been used in sample studies is inferior to the al mg th ti c diagram in discriminating kreep from mg suite rock types the orbital geochemical spectrometers analyzed the regolith in which mg varies much less than al although the fe th ti c diagram shows a diverse distribution of orbital data similar to that shown by the al mg th ti c diagram it is unable to discriminate adequately between kreep and mg suite rock types the fe th ti c diagram is nonetheless very useful because of its greater areal coverage orbital and soil sample compositions of the four highland landing sites correspond in both the al mg th ti c and the fe th ti c data the diagrams show some units of virtually pure anorthosite and norite most units show the effects of mixing of pristine rock types in the regolith one unit which dominates the eastern limb and farside highlands has a composition so mafic that with the chosen end members it requires a 30 mare basalt component we interpret this to mean that the highlands experienced a significantly greater amount of mare volcanism before the end of heavy bombardment than has been previously suggested the average global composition of the highlands under the apollo groundtracks is that of anorthositic gabbro an average that has significant implications for the role of near global plagioclase fractionation in lunar crustal genesis our analysis has shown that the simultaneous use of orbital and sample geochemical data in variation diagrams can 1 bridge the mechanical gap between orbital and sample studies by relating orbital data to sample petrology 2 present the results of several elemental databases as one map for rapid geologic analysis and 3 display quantitative mixing relations of different crustal materials in a spatial format this technique will be valuable for petrologic interpretation of the global geochemical data to be received from the future lunar geosciences orbiter mission

spectral properties of the marius hills volcanic complex and implications for the formation of lunar domes and cones we have used multispectral data from the clementine uv visible camera to study the volcanic features of the marius hills complex and their comparison to other lunar domes and cones there are several mare units identified in the complex each with a unique ti content as indicated by their 415 750 nm value the domes in marius hills are spectrally identical to the mare plains of the complex supporting similar compositions in contrast most of the volcanic cones of the complex are lower in reflectance bluer in color and have weaker mafic absorptions than the mare and domes the spectral characteristics of the cones can best be explained by fine grained crystallization in the spatter that compose the cones other lunar cones such as mons esam in northern tranquillitatis have spectral properties similar to those at marius hills the rima parry cones and their associated dark mantle deposit appear redder with a stronger mafic absorption than the marius hills cones the cones isis and osiris in southern mare serenitatis the domes of rumker hills and several domes in northern mare tranquillitatis are spectrally similar to adjacent mare units the mairan and gruithuisen domes in northern oceanus procellarum have a feldspathic signature characteristic of highland material although they are redder and brighter than adjacent highland soils they appear to represent highland material that resembles domes rather than actual mare domes like those at marius and rumker hills the diversity of lunar volcanic features can best be explained by differences in accumulation rates and cooling of ejected clasts from various eruption styles mare domes may have formed at lower effusion rates thereby allowing lava to construct small shields with slopes 3 the steeper domes at marius hills require higher viscosities resulting from even lower effusion rates and enhanced crystallization in the magmas during the terminal stages of earlier eruptions that emplaced the mare cones like mons esam rima parry isis and osiris are aligned along linear rilles and are interpreted to result from degassing of near surface dikes in contrast the cones of marius hills show no linear alignment and may result from strombolian eruptions at the terminal stages of earlier effusive eruptions that emplaced the domes and mare in the complex

heterogeneous impact transport on the moon impact cratering is the dominant process for transporting material on the moon s surface an impact transports both proximal material continuous ejecta locally and distal ejecta crater rays to much larger distances quantifying the relative importance of locally derived material versus distal material requires understandings of lunar regolith evolution and the mixing of materials across the lunar surface the moon has distinctive albedo units of darker mare basalt and brighter highland materials and the contacts between these units are ideal settings to examine this question information on the amount of material transported across these contacts comes from both the sample collection and remote sensing data though earlier interpretations of these observations are contradictory the relatively narrow 4 5 km wide mixing zone at mare highland contacts had been interpreted as consistent with most material having been locally derived from underneath mare plains however even far from these contacts where the mare is thick highland material is abundant in some soil samples 20 requiring transport of highland material over great distances any model of impact transport on the moon needs to be consistent with both the observed width of mare highland contacts and the commonality of nonmare material in mare soil samples far from any contact in this study using a three dimensional regolith transport model we match these constraints and demonstrate that both local and distal material transports are important at the lunar surface furthermore the nature of the distal material transport mechanism in discrete crater rays can result in substantial heterogeneity of surface materials

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

oxidation states and ascent history of the apollo 17 volcanic beads as inferred from metal glass equilibria abstract the composition mode of occurrence and relationships of metal blebs in the apollo 17 74001 2 core have been examined to provide insight into variations in oxidation states during ascent and eruption of the lunar volcanic glasses the 74001 2 core is composed of 99 orange volcanic glasses and their crystallized equivalents black beads with olivine phenocrysts metal blebs and in the upper 8 cm of the core lithic fragments composing the remaining 1 in an analysis of this core twenty nine metal blebs larger than 4 m in size were discovered in thin sections taken along the length of the 68 cm deep core these blebs are classified into three types on the basis of their shape composition and distribution fourteen of the metal blebs were found trapped inside or between olivine phenocrysts type i blebs microprobe analyses showed that these spherical blebs have a homogeneous composition of 85 fe 14 ni and 1 1 co from core to rim six type ii rounded blebs were discovered trapped inside volcanic beads their core compositions are similar to the type i but near the rim these blebs have a sharp decrease in fe and increase in ni content in the lower half of the 74001 2 core where the beads are predominantly black many contain 5 m amoeba shaped type iii metal blebs type iii blebs are composed of fe with trace amounts of ni two angular metal fragments could not be classified into any of the three types we propose that the type i blebs formed initially at 4 0 km depth and 1 3 log units below iw at a pressure of 200 bars and a temperature of 1320 c by the formation of c o gas during graphite oxidation once trapped by olivine phenocrysts the blebs were buffered from further reactions with the melt the type ii blebs remained in contact with the melt during ascent and experienced loss of fe to the surrounding melt phase by oxidation reactions which range from 1 3 to 0 9 log below iw finally type iii blebs formed either by exsolution of fe during crystallization in the fire fountain or by loss of volatiles originally coordinated with fe to the volcanic gas phase under the reduced conditions in the fountain

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

beginning and end of lunar mare volcanism mare volcanism on the moon is commonly attributed to an important but relatively short lived epoch of internal heating after 3 900 myr bp but before about 2 500 myr bp refs 1 2 although some studies suggested that mare volcanism had started earlier3 5 than times indicated by dated lunar samples only recently have photogeological spectral and geochemical data6 8 documented the importance of a pre 4 000 myr bp epoch similarly early earth based geological mapping revealed a bright rayed crater lichtenberg superposed by mare units9 thereby indicating that mare volcanism must have extended to times significantly more recent than 3 100 myr bp lunar orbital photography confirmed this inferred strati graphical relationship10 but crater statistics indicated that the youngest units were at least twice the age of copernicus or between 1 700 and 2 000 myr bp refs 11 13 we present here the inferred distribution and style of the early phases of mare volcanism based on current evidence and conclude that certain regions of the moon underwent two distinct pulses of igneous activity we then examine crater statistics for the post lichtenberg mare unit and other selected units and conclude that mare volcanism extended to a time comparable with that of the copernicus impact or 1 myr bp these reassessments of the oldest and youngest maria provide new constraints on geophysical models of the internal thermal history of the moon

the evolution of impact basins viscous relaxation of topographic relief we evaluate the hypothesis that viscous relaxation has been an important process for modifying the topographic profiles of ancient large impact basins on the moon we adopt a representative topographic profile of the orientale basin the youngest large impact basin on the moon as an estimate of the initial topography of older basins of similar horizontal dimensions and we predict the topographic profiles that would result from viscous relaxation according to a number of simple analytical representations of the rheological response of the moon to surface topography at wavelengths greater than the thickness of a high viscosity lithosphere both a decrease in viscosity with depth and the partial to complete isostatic compensation of topographic relief have pronounced effects on the wavelength dependent relaxation times and must be considered in modeling viscous relaxation for features as large as impact basins the effect of a decrease in viscosity with depth is to enhance the rate of viscous relaxation at long wavelengths while the rate of relaxation decreases substantially for the fraction of long wavelength topography which is isostatically compensated as an initial condition these models are applied to two pre nectarian basins on the moon the tranquillitatis basin on the lunar nearside and the much larger and older south pole aitken basin on the farside the topographic profile of tranquillitatis after correcting for the effect of mare basalt fill is consistent with significant viscous relaxation of relief prior to the oldest episode of mare volcanism preserved as a surface unit the large topographic relief of the larger farside basin on the contrary is not consistent with significant viscous relaxation and implies a mean crustal viscosity at least a factor of 10 higher than for the central nearside over the time interval during which substantial viscous relaxation of older nearside basins such as tranquillitatis probably occurred a difference in typical crustal temperature profiles between the farside and nearside is the most likely explanation of such a viscosity difference such a nearside farside asymmetry in near surface temperature may date from the time of crust mantle differentiation and may have persisted because of the different histories of late stage impact basin formation and mare volcanism on the two hemispheres

long lived volcanism on the lunar farside revealed by selene terrain camera we determined model ages of mare deposits on the farside of the moon on the basis of the crater frequency distributions in 10 meter resolution images obtained by the terrain camera on selene selenological and engineering explorer kaguya most mare volcanism that formed mare deposits on the lunar farside ceased at 3 0 billion years ago suggesting that mare volcanism on the moon was markedly reduced globally during this period however several mare deposits at various locations on the lunar farside also show a much younger age clustering at 2 5 billion years ago these young ages indicate that mare volcanism on the lunar farside lasted longer than was previously considered and may have occurred episodically

goldschmidt crater and the moon s north polar region results from the moon mineralogy mapper m3 1 soils within the impact crater goldschmidt have been identified as spectrally distinct from the local highland material high spatial and spectral resolution data from the moon mineralogy mapper m3 on the chandrayaan 1 orbiter are used to examine the character of goldschmidt crater in detail spectral parameters applied to a north polar mosaic of m3 data are used to discern large scale compositional trends at the northern high latitudes and spectra from three widely separated regions are compared to spectra from goldschmidt the results highlight the compositional diversity of the lunar nearside in particular where feldspathic soils with a low ca pyroxene component are pervasive but exclusively feldspathic regions and small areas of basaltic composition are also observed additionally we find that the relative strengths of the diagnostic oh h2o absorption feature near 3000 nm are correlated with the mineralogy of the host material on both global and local scales the strongest hydrous absorptions occur on the more feldspathic surfaces thus m3 data suggest that while the feldspathic soils within goldschmidt crater are enhanced in oh h2o compared to the relatively mafic nearside polar highlands their hydration signatures are similar to those observed in the feldspathic highlands on the farside

lunar floor fractured craters modes of dike and sill emplacement and implications of gas production and intrusion cooling on surface morphology and structure abstract lunar floor fractured craters ffcs represent the surface manifestation of a class of shallow crustal intrusions in which magma filled cracks dikes rising to the surface from great depth encounter contrasts in host rock lithology breccia lens rigid solidified melt sheet and intrude laterally to form a sill laccolith or bysmalith thereby uplifting and deforming the crater floor recent developments in the knowledge of lunar crustal thickness and density structure have enabled important revisions to models of the generation ascent and eruption of magma and new knowledge about the presence and behavior of magmatic volatiles has provided additional perspectives on shallow intrusion processes in ffcs we use these new data to assess the processes that occur during dike and sill emplacement with particular emphasis on tracking the fate and migration of volatiles and their relation to candidate venting processes ffcs result when dikes are capable of intruding close to the surface but fail to erupt because of the substructure of their host impact craters and instead intrude laterally after encountering a boundary where an increase in ductility base of breccia lens or rigidity base of solidified melt sheet occurs magma in dikes approaching the lunar surface experiences increasingly lower overburden pressures this enhances co gas formation and brings the magma into the realm of the low pressure release of h2o and sulfur compounds both factors adding volatiles to those already collected in the rising low pressure part of the dike tip high magma rise velocity is driven by the positive buoyancy of the magma in the part of the dike remaining in the mantle the dike tip overshoots the interface and the consequent excess pressure at the interface drives the horizontal flow of magma to form the intrusion and raise the crater floor if sill intrusion were controlled by the physical properties at the base of the melt sheet dikes would be required to approach to within 300 m of the surface and thus eruptions rather than intrusions would be very likely to occur instead dynamical considerations strongly favor the sub crustal breccia lens as the location of the physical property contrast localizing lateral intrusion at a depth of several kilometers the end of lateral and vertical sill growth occurs when the internal magma pressure equals the external pressure the intrusion just supports the weight of the overlying crust dynamical considerations lead to the conclusion that dike magma volumes are up to 1100 km3 and are generally insufficient to form ffcs on the lunar farside the estimated magma volumes available for injection into sills on the lunar nearside up to 800 km3 are comparable to the observed floor uplift in many smaller ffcs and thus consistent with these ffcs forming from a single dike emplacement event in contrast the thickest intrusions in the largest craters imply volumes requiring multiple dike contributions these are likely to be events well separated in time rather than injection of new magma into a recently formed and still cooling intrusion we present a temporal sequence of 1 dike emplacement 2 sill formation and surface deformation 3 bubble rise foam layer formation and collapse 4 intrusion cooling and a synthesis of predicted deformation sequence and eruption styles initial lateral injection of the sill at a depth well below the upper dike tip initiates upbowing of the overburden leveraging deformation of the crater floor melt sheet above this is followed by lateral spreading of the sill toward the edges of the crater floor where crater wall and rim deposit overburden inhibit further lateral growth and the sill grows vertically into a laccolith or bysmalith uplifting the entire floor above the intrusion subsidiary dikes can be emplaced in the fractures at the uplift margins and will rise to the isostatic level of the initial dike tip if these contain sufficient volatiles to decrease magma density eruptions can also occur this initial phase of intrusion sill lateral spreading and floor uplift occurs within a few hours after initial dike emplacement during the subsequent cooling of the sill bubbles can rise hundreds of meters to the top of the intrusion to create a foam layer when drainage of gas bubble wall magma occurs in the foam layer a continuous gas layer forms above the foam gas formation and upward migration produces an increase in sill thickness while subsequent cooling and solidification cause a thickness decreases and subsidence the total topographic evolution history following an initial 2 km thick sill intrusion and floor uplift hours includes further floor uplift by gas formation and migration decades 30 m followed by cooling solidification and subsidence a century 350 m an initial 2 km thick sill is predicted to have a final thickness of 1 7 km this predicted sequence of events can be compared with the sequence of floor deformation and volcanism in ffcs in order to test and refine this model

basalt thickness in mare humorum the crater excavation method basalt thicknesses in mare basins have been determined using assumptions about the premare topography of partly buried craters and by comparison to the orientale basin differences in those assumptions have led to a factor of 4 difference in mare thickness estimates further knowledge of thickness is restricted to areas in which buried craters are present using mixing models applied to multispectral images acquired by the clementine spacecraft we have shown that craters in the mare sometimes excavate highland material from below the mare cover using such craters and assumptions about their depth of excavation we obtain independent estimates of basalt thickness our results are in agreement with the lowest of previous thickness estimates we derive a volume of 40 000 km 3 for basalts in mare humorum considerably less than the 110 000 km 3 from previous estimates we also confirm a diameter of 425 km for thc humorum multiring basin based on the clementine gridded global topography assuming an original morphology like orientale

the role of rift zone storage in controlling the site and timing of eruptions and intrusions of kilauea volcano hawaii repeated eruptive and intrusive activity on the east rift zone of kilauea volcano allows dikes to exist within the rift zone for extended periods of time leakage of magma from the summit storage region into the rift zone can cause inflation of a rift zone dike inflation raises the excess pressure at the dike centre and increases the stress intensity at the dike edges if the inflation is sufficiently large the stress intensity may exceed the fracture toughness of the country rocks and allow vertical or lateral dike emplacement to occur theoretical modelling can be used to predict the conditions under which vertical or lateral dike propagation and hence eruptive or intrusive activity may occur over typical ranges of dike half height and regional tension gradient vertical propagation and hence eruption are favored by high fracture toughness relatively low dike half heights and low regional tension gradients lateral propagation can occur when the fracture toughness is low when dike half height is higher and when the regional tension gradient is high the results of from the model constrain the fracture toughness within the east rift zone to be 100 110 mpa m and the regional tension gradient to be 1000 pa m

early crustal building processes on the moon models for the petrogenesis of the magnesian suite abstract the plutonic rocks of the magnesian suite mg suite represent the period of lunar basaltic magmatism and crustal growth 4 46 to 4 1 ga that immediately followed the initial differentiation of the moon by magma ocean lmo formation and crystallization the volume and distribution of the mg suite and its petrogenetic relationship to latter stages of lunar magmatism mare basalts remains obscure these plutonic rocks exhibit a range of compositions and include ultramafics troctolites spinel troctolites norites and gabbronorites a distinguishing characteristic of this suite is that they contain some of the most magnesium rich phases fo95 90 that had crystallized from lunar magmas yet they also are significantly enriched in an incompatible element component referred to as kreep a late stage product of lmo crystallization containing abundant potassium k rare earth elements ree phosphorous p uranium and thorium ion microprobe analyses of individual mineral phases olivine pyroxene and plagioclase from the mg suite have shown some very unexpected characteristics that have profound implications on the origin of these basaltic magmas although the mg suite lithologies are typified by silicates with relatively high mg early liquidus phases such as olivine are fairly low in ni co and cr relative to more iron rich olivines in the younger mare basalts the high y and ti y in early phases such as olivine and orthopyroxene indicate that the parental basaltic melts were high in incompatible elements and contained an ilmenite fractionation signature however the y in olivine from many of the troctolites and ultramafic lithologies are only slightly greater than that of the olivine in the mare basalts whereas olivine in the norites gabbronorites and apollo 14 troctolites are exceedingly high the kreep component may have been added to the mg suite parent magmas by assimilation or mixing into the mantle source the volume of kreep required to be added to the parental magmas of the mg suite tends to favor the latter mechanism for kreep incorporation the extremely high abundances of kreep in the norites and gabbronorites are a product of substantial crystallization 40 to 70 of kreep enriched mg suite parental magmas basaltic magmatism associated with kreep extended for over 1 5 billion years and appears to have changed over time the early stages of this style of lunar magmatism mg suite appear to represent melting of early lmo cumulates with low abundances of ni co cr and v later stages of kreep rich basaltic magmatism seemed to clearly involve melting of a variety of lmo cumulate assemblages with higher incompatible element enrichment it appears that the heat derived from the kreep component was instrumental in at least initiating melting of the lunar mantle over this period of time

explosive volcanism on mercury analysis of vent and deposit morphology and modes of eruption abstract the messenger mission revealed for the first time conclusive evidence of explosive volcanism on mercury several previous works have cataloged the appearance and location of explosive volcanism on the planet using a variety of identifying characteristics including vent presence and deposit color as seen in multispectral image mosaics we present here a comprehensive catalog of vents of likely volcanic origin our classification scheme emphasizes vent morphology we have analyzed the morphologies of all vents in our catalog and recognize three main morphologies simple vent pit vent and vent with mound the majority of vents we identify are located within impact craters the spatial distribution of vents does not correlate with the locations of volcanic smooth plains deposits in contrast to the moon nor do vents correlate with the locations of large impact basins except for the caloris and tolstoj basins using the degradation state of the vent host crater as a proxy for maximum age we suggest that vent formation has been active through the mansurian and into the kuiperian periods although the majority of vents were likely formed much earlier in mercurian history the morphologies and locations of vents are used to investigate a set of plausible formation geometries we find that the most likely and most prevalent formation geometry is that of a dike stalled at depth which then explosively vents to the surface we compare the vent and deposit size of mercurian pyroclastic deposits with localized and regional lunar pyroclastic deposits and find a range of possible eruption energies and corresponding variations in eruption style localized lunar pyroclastic deposits and the majority of mercurian pyroclastic deposits show evidence for eruption that is consistent with the magmatic foam at the top of a dike reaching a critical gas volume fraction a subset of mercurian vents including the prominent copland rachmaninoff vent to the northeast of the rachmaninoff basin indicates eruption at enhanced gas volume fractions this subset of vents shows a similar eruptive behavior to the lunar orientale dark mantle ring deposit suggesting that the dikes that formed these vents and deposits on mercury underwent some form of additional volatile build up either through crustal volatile incorporation or magma convection within the dike there also exists a population of mercurian vents that no longer retain a visible associated pyroclastic deposit we hypothesize that the visible signature of the pyroclastic deposit has been lost through space weathering and regolith mixing processes together these results provide a comprehensive analysis of explosive volcanism on mercury and inform continued research on the thermal history of mercury and magma composition and evolution

lunar intrusive domes morphometric analysis and laccolith modelling abstract this study examines a set of lunar domes with very low flank slopes which differ in several respects from the frequently occurring lunar effusive domes some of these domes are exceptionally large and most of them are associated with faults or linear rilles of presumably tensional origin accordingly they might be interpreted as surface manifestations of laccolithic intrusions formed by flexure induced vertical uplift of the lunar crust or alternatively as low effusive edifices due to lava mantling of highland terrain or kipukas or structural features all of them are situated near the borders of mare regions or in regions characterised by extensive effusive volcanic activity clementine multispectral uvvis imagery indicates that they do not preferentially occur in specific types of mare basalt our determination of their morphometric properties involving a combined photoclinometry and shape from shading technique applied to telescopic ccd images acquired at oblique illumination reveals large dome diameters between 10 and more than 30 km flank slopes below 0 9 and volumes ranging from 0 5 to 50 km 3 we establish three morphometric classes the first class in1 comprises large domes with diameters above 25 km and flank slopes of 0 2 0 6 class in2 is made up by smaller and slightly steeper domes with diameters of 10 15 km and flank slopes between 0 4 and 0 9 and domes of class in3 have diameters of 13 20 km and flank slopes below 0 3 while the morphometric properties of several candidate intrusive domes overlap with those of some classes of effusive domes we show that a possible distinction criterion are the characteristic elongated outlines of the candidate intrusive domes we examine how they differ from typical effusive domes of classes 5 and 6 defined by head and gifford head j w gifford a 1980 lunar mare domes classification and modes of origin moon planets 22 235 257 and show that they are likely no highland kipukas due to the absence of spectral contrast to their surrounding these considerations serve as a motivation for an analysis of the candidate intrusive domes in terms of the laccolith model by kerr and pollard kerr a d pollard d d 1998 toward more realistic formulations for the analysis of laccoliths j struct geol 20 12 1783 1793 to estimate the geophysical parameters especially the intrusion depth and the magma pressure which would result from the observed morphometric properties accordingly domes of class in1 are characterised by intrusion depths of 2 3 3 5 km and magma pressures between 18 and 29 mpa for the smaller and steeper domes of class in2 the magma intruded to shallow depths between 0 4 and 1 0 km while the inferred magma pressures range from 3 to 8 mpa class in3 domes are similar to those of class in1 with intrusion depths of 1 8 2 7 km and magma pressures of 15 23 mpa as an extraordinary feature we describe in some detail the concentric crater archytas g associated with the intrusive dome ar1 and discuss possible modes of origin in comparison to the candidate intrusive domes terrestrial laccoliths tend to be smaller but it remains unclear if this observation is merely a selection effect due to the limited resolution of our telescopic ccd images an elongated outline is common to many terrestrial laccoliths and the putative lunar laccoliths while the thickness values measured for terrestrial laccoliths are typically higher than those inferred for lunar laccoliths but the typical intrusion depths are comparable

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

mineralogical survey of the anorthositic feldspathic highlands terrane crust using moon mineralogy mapper data abstract spectroscopic data from the moon mineralogy mapper m 3 instrument are used to study the mineralogy of the central peak or peak ring of 75 craters located in the lunar anorthositic feldspathic highlands terrane fht a as defined by jolliff et al 2000 the thickness of south pole aitken spa ejecta at the location of the selected craters is estimated crustal thickness models are used with empirical cratering equations to estimate the depth of origin of the material excavated in the studied central peaks and its distance to the crust mantle interface the goal of this survey is to study the composition of the fht a crust and the extent of its potential lateral and vertical heterogeneities high calcium pyroxene hcp and featureless spectra are mostly detected throughout the entire fht a whereas the number of pure plagioclase detections is small no relationship between the central peak composition and the distance to spa or the depth within the spa ejecta is observed the spa ejecta material cannot be spectrally distinguished from crustal material we interpret the paucity of plagioclase spectra in the fht a which contrasts with more frequent plagioclase detections in the central peaks of craters sampling the crust in younger lunar terranes using identical spectroscopic techniques martinot et al 2018b as a possible effect of terrane maturation or of mixing with mafic components that mask their signature in the visible near infrared overall the fht a appears homogeneous laterally however data hint at a pyroxene compositional change with increasing depth from high calcium content in the upper crust towards less calcic compositions with increasing depth which is consistent with prior studies of the architecture of the lunar crust

small scale lunar farside volcanism abstract we identified and mapped 28 mare basalt occurrences between the australe and south pole aitken basins on the southern lunar farside and determined their absolute model ages amas by performing crater size frequency distribution csfd measurements our study area can be subdivided into seven major mare basalt occurrences in and around bolyai roche v rosseland pauli and roche craters south of both rosseland and coblentz craters as well as mare patches between eotvos and roche craters the amas of the mare basalts in and around bolyai crater range from 2 1 ga to 3 5 ga two units varying drastically within short distances the mare patches south of coblentz crater contain nine units that have amas ranging from 2 1 ga to 3 8 ga the mare basalts in roche v crater show an ama of 2 2 ga we mapped seven volcanic units in rosseland crater and derived amas for five of these units the mare basalts in rosseland crater show the youngest amas found in our study area ranging from 1 5 ga to 2 9 ga the mare basalt occurrence south of rosseland crater shows significantly older ages with an ama of 3 3 ga the mare basalts in pauli and roche craters show amas from 1 7 ga to 3 1 ga the mare patches between eotvos and roche craters show a similar range of amas from 1 9 ga to 3 1 ga the amas of the mare basalts in our study show that the lunar farside was volcanically active for nearly as long as the lunar nearside 1 2 ga ago or at least longer than previously thought 2 5 ga ago and predicted by models of the ascent and eruption of lunar basalts in addition we calculated thicknesses and volumes of the investigated mare basalts with thicknesses between 21 m and 172 m and volumes from 0 1 km3 to 379 km3 the mare basalts in our study area show a wide range of dimensions similar to other mare basalts of the lunar near and farsides

mineralogical diversity and geology of humboldt crater derived using moon mineralogy mapper data moon mineralogy mapper m3 spectroscopic data and high resolution imagery data sets were used to study the mineralogy and geology of the 207 km diameter humboldt crater analyses of m3 data using a custom made method for m3 spectra continuum removal and spectral parameters calculation reveal multiple pure crystalline plagioclase detections within the humboldt crater central peak complex hinting at its crustal origin however olivine spinel and glass are observed in the crater walls and rims suggesting these minerals derive from shallower levels than the plagioclase of the central peak complex high calcium pyroxenes are detected in association with volcanic deposits emplaced on the crater s floor geologic mapping was performed and the age of humboldt crater s units was estimated from crater counts results suggest that volcanic activity within this floor fractured crater spanned over a billion years the felsic mineralogy of the central peak complex region which presumably excavated deeper material and the shallow mafic minerals olivine and spinel detected in humboldt crater walls and rim are not in accordance with the general view of the structure of the lunar crust our observations can be explained by the presence of a mafic pluton emplaced in the anorthositic crust prior to the humboldt forming impact event alternatively the excavation of australe basin ejecta could explain the observed mineralogical detections this highlights the importance of detailed combined mineralogical and geological remote sensing studies to assess the heterogeneity of the lunar crust

igneous activity in the southern highlands of the moon 1 detailed investigations of both endogenic and exogenic dark haloed craters can provide critical information concerning the geology composition and evolution of portions of the lunar surface several dark haloed and dark rayed craters have been identified in the maurolycus region in the southeastern nearside highlands clementine and galileo multispectral imagery as well as earth based remote sensing data were used to investigate the composition and origin of dark haloed craters in the region a striking albedo anomaly is associated with buch b crater which exhibits both a dark halo and dark rays the result of a morphologic analysis clearly indicated that buch b is an impact structure not a volcanic vent the optical maturity image shows that the buch b ejecta deposits are immature and the radar and thermal data indicate a high abundance of fresh rocks and fragments in the 1 50 cm size range feo and tio2 data as well as five point spectra extracted from clementine uv vis images indicate that the dark ejecta is composed of immature mare like material and may contain minor amounts of highland debris buch b excavated either an isolated cryptomare or more likely a mafic intrusion one or more dikes of basaltic composition are possible candidates minor low albedo anomalies have been identified around three other impact craters maurolycus a and b and barocius m in the region while small feo enhancements are seen in portions of the ejecta deposits associated with these craters they do not approach the feo values 12 14 wt exhibited by the dark deposits of buch b and they do fall within the range of feo abundances 5 9 wt exhibited by highland terrain in the maurolycus region hence the presence of a basaltic component is not required and it cannot be concluded that either cryptomare or mafic intrusions were present in the target sites of these craters

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

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

magnetic signature of the lunar south pole aitken basin character origin and age 1 a new magnetic map of the moon based on lunar prospector magnetometer observations sheds light on the origin of the south pole aitken basin spa the largest and oldest of the recognized lunar basins a set of wnw trending linear to arcuate magnetic features evident in both the radial and scalar observations covers much of a 1000 km wide region centered on the nw portion of spa the source bodies are not at the surface because the magnetic features show no first order correspondence to any surface topographic or structural feature patchy mare basalts of possible late imbrian age are emplaced within spa and are inferred to have been emplaced through dikes directly from mantle sources we infer that the magnetic features represent dike swarms that served as feeders for these mare basalts as evident from the location of the thomson mare ingenii van de graaff and leeuwenhoek mare basalts on the two largest magnetic features in the region modeling suggests that the dike zone is between 25 and 50 km wide at the surface and dike magnetization contrasts are in the range of 0 2 a m we theorize that the basaltic dikes were emplaced in the lunar crust when a long lived dynamo was active based on pressure temperature and stress conditions prevalent in the lunar crust dikes are expected to be a dominantly subsurface phenomenon consistent with the observations reported here

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

chemical variation of the large apollo 15 olivine normative mare basalt rock samples most chemical analyses of apollo 15 olivine normative mare basalts have been conducted on subsamples of 4 g to obtain greater whole rock representivity these subsamples were individually ground and homogenized and splits were taken for analysis furthermore we used both x ray fluorescence and neutron activation techniques to analyze for a comprehensive set of elements suitable for petrogenetic interpretation the analyses show that the samples form a single coherent suite with almost all of the variation corresponding with olivine control 15 range a few of the coarser rocks are not quite represented even at this sampling size the analyses show that the rocks are individually distinct and that analyses are not merely of unrepresentative pieces of a single rock undifferentiated rock unit or rocks differing only by short range unmixing of residual fluids the petrographic features including the low abundance of olivine and its small size and the vesicularity of even some of the coarser samples show that the olivine that controlled the chemical variation is not accumulated in any of the rocks the apollo 15 olivine normative mare basalts were extruded as a series of magmas from a shallow but not locally surficial olivine accumulating magma system and formed a sequence of thin flows a greater understanding of the relationships within and among other mare basalt sequences would be obtained by obtaining comprehensive chemical analyses on splits taken from subsamples of 5 g of all rocks large enough to obtain such subsamples

constraints on the history of open basin lakes on mars from the composition and timing of volcanic resurfacing 1 abundant evidence exists for valley network related fluvial activity near the noachian hesperian transition on mars and areally significant quantities of volcanic ridged plains were emplaced during this period as well thus it is worthwhile to explore the hypothesis that lava water interaction occurred on the surface of mars at this time we analyzed the morphology physical properties composition and surface ages of thirty open basin lakes topographic lows with both an inlet valley and an outlet valley that were also resurfaced by volcanic flows hyperspectral imaging data from the compact reconnaissance imaging spectrometer for mars crism and observatoire pour la mineralogie l eau les glaces et l activite omega instruments indicate that of the 30 basins 12 exhibit the spectral properties of basaltic lithologies with diagnostic absorptions of olivine high calcium pyroxene and low calcium pyroxene an olivine high calcium pyroxene mixture is the most commonly identified mineral assemblage consistent with other hesperian aged volcanic units therefore our mineralogical results for over a third of the open basin lake floors analyzed support prior interpretations that the basins were resurfaced by volcanic flows supporting evidence for resurfacing by volcanic flows is also given by the observed morphology and physical properties e g surface roughness thermal inertia of the resurfaced open basin lake floors in these 30 examples however no evidence was found for lava water interaction the ages of emplacement derived through counts of superposed craters of all 30 of the open basin lake volcanic resurfacing units show that resurfacing began in the late noachian near the noachian hesperian boundary was concentrated in the hesperian and continued into the early amazonian the lack of geologic features indicative of lava water interaction suggests that the basins were likely to have been mostly devoid of water at the time of the latest phase of volcanic resurfacing we conclude that there is no geologic evidence that suggests the fluvial activity associated with the studied paleolakes was coeval with the emplacement of the observed volcanic resurfacing units several of which date to the late noachian early hesperian

remelting mechanisms for shallow source regions of mare basalts abstract two mechanisms are studied which could induce remelting at shallow depths within the moon a radioactive heating model in which remelting is the result of lateral variations of the heat source concentration emplaced by the end of the initial differentiation event and a thermal insulation model in which remelting is induced by lateral variations of near surface conductivity as a result of a high porosity ejecta blanket created by basin forming impacts the effects of these perturbations are studied by evaluating the thermal evolution of an otherwise radially symmetric lunar model the radioactive heating models predict extensive pre basin volcanism which would probably remove from the source region many of the heat producing elements potentially responsible for melting therefore localized high concentrations of heat producing elements emplaced early would most probably not be heat sources for the basin filling mare basalts however they are plausible heat sources for pre basin mare basalts the thermal insulation model predicts a delay of about 200 m y between impact and volcanism thermal insulation may also allow for the persistence of source regions for young basalts at shallow depths if greater basin ages are correct from 4 2 to 3 9 ga and most volcanism occurred between 3 8 and 3 6 ga then the thermal insulation model may explain the delay between impact and basin filling if the basins formed during a terminal cataclysmic event at about 3 9 ga then the earliest stages of basin filling at about 3 8 ga may have been a result of melting beneath the basin as a result of mantle uplift basin filling may have been characterized by a migration of the source region from beneath the basin to beneath the adjacent highlands cooling of the top 200 km beneath the basin after 200 m y because of its high surface conductivity is consistent with the mascon support requirement

global petrologic variations on the moon a ternary diagram approach ltrbil kreep rich rocks 5j portions of the east limb and 4 highlands have considerable amounts of a mafic chondritic th ti component like mare basalt whose occurrences coincide with mapped concentrations of light plains that display dark halo craters the presence of this component supports the hypothesis that mare volcanism had occurred within this highland region before the end of final heavy bombardment

lunar floor fractured craters classification distribution origin and implications for magmatism and shallow crustal structure 1 floor fractured craters ffcs are a class of lunar craters characterized by anomalously shallow floors cut by radial concentric and or polygonal fractures additional interior features are moats ridges and patches of mare material two formation mechanisms have been hypothesized floor uplift in response to shallow magmatic intrusion and sill formation and floor shallowing in response to thermally driven viscous relaxation this study combines new lunar orbiter laser altimeter lola and lunar reconnaissance orbiter camera lroc data to characterize and categorize the population of ffcs and map their distribution on the moon and uses variations in floor fractured crater morphology and regional distribution to investigate the proposed formation mechanisms the population of ffcs was categorized according to the classes outlined by schultz 1976 the distribution of these ffc categories shows an evolution of crater morphology from areas adjacent to lunar impact basins to areas in the lunar highlands we propose that this trend is supportive of formation by shallow magmatic intrusion and sill formation crustal thickness determines the magnitude of magmatic driving pressure and thus either piston like floor uplift for high magnitude or a convex floor profile for low magnitude predictions from previous studies modeling viscous relaxation are inconsistent with the observed altimetric profiles of ffcs hence our analysis favors ffc formation by shallow magmatic intrusion with the variety of ffc morphologies being intimately linked with location and crustal thickness and the driving pressure of the intrusion data from the grail gravity recovery and interior laboratory mission will help to test these conclusions

tsiolkovsky crater a window into crustal processes on the lunar farside mineralogy and distribution of rock types in the tsiolkovsky region of the lunar farside are evaluated in terms of crustal stratigraphy and evolution calibrated multispectral images from five orbits of clementine data provide compositional information at a scale that allows diverse geologic features to be analyzed and compared the entire region is seen to be highly anorthositic with outcrops of relatively pure anorthosite quite common the crater itself has excavated blocks of anorthosite and noritic anorthosite from the near surface highland crust often in a mixed jumble the central peaks of tsiolkovsky which have exhumed much deeper material however are composed of relatively pure anorthosite with olivine rich zones concentrated near the ridge crests boundaries between the anorthosite and olivine rich zones are sharp but spatial relations suggest the coherent olivine rich zone is relatively thin 1 km the composition of the mare material filling tsiolkovsky is shown to be low titanium basalt smaller exposures of mare basalt occur about one crater radius from the rim the crustal structure to 25 km in this region prior to the tsiolkovsky impact appears to be top to bottom a few kilometers of anorthositic breccias comprising the megaregolith a zone of crystalline anorthosite with pockets of noritic anorthosite a zone of anorthosite devoid of iron bearing minerals and a zone of relatively pure anorthosite containing olivine rich material possibly emplaced as intrusions

intercrater plains on mercury insights into unit definition characterization and origin from messenger datasets abstract orbital observations by the mercury surface space environment geochemistry and ranging messenger spacecraft are used to re evaluate the nature and origin of the oldest mapped plains deposits on mercury the intercrater and intermediate plains units defined by mariner 10 investigators despite the large areal extent of these plains which comprise approximately one third of the planetary surface area viewed by mariner 10 their formation mechanism was not well constrained by mariner 10 imaging one hypothesis attributed plains formation to ponding of fluidized impact ejecta to create relatively smooth surfaces another hypothesis was that these plains are of volcanic origin to assess the origin of these older plains and the contribution of early volcanism to resurfacing on mercury we have used messenger data to analyze the morphology spectral properties impact crater statistics and topography of mariner 10 type areas of intercrater and intermediate plains on the basis of new criteria for the identification of intercrater and intermediate plains derived from these observations we have remapped 18 of the surface of mercury we find that the intercrater plains are a highly textured unit with an abundance of secondary craters whereas the intermediate plains are composed of both intercrater and smooth plains we suggest that the term intermediate plains not be used to map the surface of mercury henceforth but rather this unit should be subdivided into its constituent intercrater and smooth plains units we argue that a substantial percentage of the intercrater plains are composed of volcanic materials on the basis of 1 examples of areas where ejecta from a small number of superposed craters have transformed smooth plains deposits of volcanic origin into a unit indistinguishable from intercrater plains 2 the range in ages of intercrater plains deposits as interpreted from crater size frequency distributions and 3 the near global distribution of intercrater plains compared with the uneven distribution of impact basins and their associated ejecta deposits

the uniform k distribution of the mare deposits in the orientale basin insights from chang e 2 gamma ray spectrometer the composition of mare basalt units in the orientale basin are investigated by using the potassium k map derived from chang e 2 gamma ray spectrometer ce 2 grs and feo map derived from clementine uv vis data set together with crater retention ages of the mare basalts from literature data we aim to investigate possible magma sources underneath the orientale basin and their chemical evolution over time analyses of the chemical composition of the resurfaced mare basalts together with the reported eruption ages suggest a unique magma generating process for the resurfaced mare deposits the early mare basalts in the central mare orientale and the later resurfaced mare deposits probably derived from magma generated by heat release due to high radioactive element concentrations based on forward modeling the similar k abundances observed in the small mare deposits of the sw polygon area lacus veris and lacus autumni and those in the central mare orientale imply the same heat source for these lava eruptions the chemical similarities e g k feo and tio2 of these regions suggest that mare basalts within the orientate basin are a result of multiple eruptions from a relatively homogeneous source underneath the basin c 2014 elsevier b v all rights reserved

mineralogical variation of the late stage mare basalts the last major phases of lunar volcanism occurred mainly in oceanus procellarum and mare imbrium and produced spectrally unique medium and high titanium basalts the composition and distribution of these basalts provide a record of the late stage thermal evolution of the moon to study the spectral and mineralogical variations of the late stage mare basalts 31 distinct units were mapped employing a range of remote sensing data their inferred mineralogical characteristics were studied by analyzing the spectral features of small fresh craters derived from the moon mineralogy mapper m3 data the strongest olivine spectral signatures were found around lichtenberg crater while the units with the lowest olivine pyroxene ratio occurred mainly in the southern kepler crater and some local areas in oceanus procellarum the olivine pyroxene ratio decreases progressively from the lichtenberg crater to the southern units the northern and southern units within mare imbrium have higher olivine pyroxene ratios than the central ones the inferred abundance of olivine appears to vary stratigraphically with the younger flows being more olivine rich however the stratigraphically younger units around euler crater in mare imbrium which present as dark red hues in the integrated band depth image of m3 were found to have lower olivine pyroxene ratios than the units around lichtenberg crater shown as light red hues in oceanus procellarum it could be interpreted that the late stage mare basalts around lichtenberg crater originated from a more olivine rich source than those around euler crater

remote sensing of lunar pyroclastic mantling deposits abstract mantling deposits on the moon are considered to be pyroclastic units emplaced on the lunar surface as a result of explosive fire fountaining these pyroclastic units are characterized as having low albedos having smooth fine textured surfaces and consisting in part of homogeneous febearing volcanic glass and partially crystallized spheres mantling units exhibit low returns on depolarized 3 8 cm radar maps indicating an absence of surface scatterers in the 1 to 50 cm size range a number of reflectance spectra from several regional pyroclastic deposits are presented for the first time these data support a previous interpretation that mantling units have a unique spectral signature which is indicative of the presence of a significant fe bearing volcanic glass component the rima bode region is discussed as an example of an area in which several types of remote sensing data including 3 8 cm radar spectral reflectance and multispectral vidicon data were used to reconstruct the geologic events surrounding the emplacement of a regional pyroclastic mantling deposit the recognition of numerous varieties of volcanic glass samples especially relatively high albedo e g green yellow glasses suggests the existence of additional unrecognized mantling deposits with albedos higher than those studied to date on the basis of the remote sensing data summarized and presented five new areas have been identified which may represent higher albedo regional pyroclastic deposits

characteristics of lunar mare deposits in smythii and marginis basins implications for magma transport mechanisms an analysis of 34 lunar lava flows and ponds in the eastern limb smythii and marginis basins was undertaken to examine and model the first stages of secondary crustal formation and assess processes involved in magma transport and eruption in order to isolate the characteristics of single eruptive episodes we focused on discrete mare ponds adjacent to the major mafia mean values for areas and volumes of deposits estimated to be good candidates for single eruptive phases are large approximately 950 1000 km 2 and 200 km 3 respectively these eruptive volumes are commensurate with the largest known terrestrial eruptions flood basalts the lack of geomorphological structures indicative of shallow magma reservoirs indicates that deep probably subcrustal source regions are prevalent with respect to crustal thickness relationships the magnitude and frequency of eruptive events are observed to be greatest in areas of thinnest crust specifically regions of major maria mare smythii mare marginis occur in areas of thinnest crust while isolated ponds occur where the crust is relatively thicker this is consistent with the correlation observed globally between crustal thickness and the magnitude and frequency of eruptive events ages of volcanic flows and pyroclastic events range from early imbrian to imbfian eratosthenian but are concentrated most heavily between 3 80 3 60 ga suggesting a period of peak volcanism beginning around 3 85 ga and lasting approximately 200 ma however the existence of dark halo crater clusters in non mare units within the region suggests the presence of cryptomaha which would indicate an earlier onset of volcanism and a volume of mare matehal potentially greater than that currently exposed on the surface typical nearest neighbor distances suggest deposits derive from reservoirs 100 km in diameter the observations made here are consistent with a magma transport model in which plumes rising diapirically stall at a density boundary under the lunar crust and propagate dikes to the surface through overpressufization

growth of planetary crusts the planets and satellites of the solar system show much diversity but most have formed crusts which differ substantially from their bulk compositions three principal types of crust may be broadly distinguished primary formed after accretional heating e g lunar highlands secondary formed following partial melting in planetary mantles e g lunar maria terrestrial oceanic crust and tertiary formed by processing of secondary crusts of which the continental crust of the earth is the only identifiable example crustal growth before 3800 m y was complicated by the heavy planetesimal bombardment active erosion on the earth is likely to have destroyed the brecciated rubble resulting from over 200 mare orientale scale events in this period the mercurian crust is probably primary perhaps analogous to the lunar highlands in contrast the observable martian and venusian crusts are secondary dominated by basaltic volcanism the icy crusts of the satellites of the outer planets are mixtures of both primary and secondary crusts with complex histories ganymede is of special interest in displaying a secondary grooved terrain water ice crust which has split an older more heavily cratered possibly primary crust slight expansion has resulted probably from polymorphic transitions from high density ice viii to low density ice i the primary lunar crust 12 of lunar volume grew in 108 years secondary crusts derived by partial melting of mantles grow at a much slower rate total production of terrestrial oceanic crust over 4000 m y is only 2 of planetary volume whereas terrestrial continental crustal growth is even slower producing over the same period a volume only about 0 33 that of the earth crustal growth on the other planets appears to be an irreversible process without evidence of recycling no evidence for massive planetary expansion as required by expanding earth hypotheses is apparent on the other planets or satellites of the solar system

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