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

eruption history of the elysium volcanic province mars abstract volcanism has played a significant role in shaping the surface of mars volatiles released during eruptions profoundly altered the composition and density of the martian atmosphere in the past quantifying the amounts of volcanic outgassing has been attempted regionally and globally however volume estimates of erupted volcanic material in time are still poorly constrained here we show the first eruption frequency record of a volcanic region the elysium volcanic province which is the second largest volcanic province on mars studied lava flows show model ages ranging from 3 4 ga to 60 ma together with observed resurfacing ages the visible record of volcanic activity extends back to 3 9 ga based on our 190 model ages continuous volcanic activity is apparent with a major peak at 2 2 ga in the last 1 gyr the activity rapidly waned although the majority of volcanic material including volatiles released to the atmosphere erupted within a short time span of less than 200 ma activity continued until the very recent past extrapolating the eruption record it appears likely that this region of mars is still volcanically active today our derivation of the eruption record has profound implications for global thermal and atmospheric modeling indicating sustained heat production melt generation and magma ascent at a single location over most of the planet s geological history

evolution of the interior of mercury influenced by coupled magmatism mantle convection system and heat flux from the core to discuss mantle evolution in mercury i present two dimensional numerical models of magmatism in a convecting mantle thermal compositional and magmatic buoyancy drives convection of temperature dependent viscosity fluid in a rectangular box placed on the top of the core that is modeled as a heat bath of uniform temperature magmatism occurs as a permeable flow of basaltic magma generated by decompression melting through a matrix widespread magmatism caused by high initial temperature of the mantle and the core makes the mantle compositionally stratified within the first several hundred million years of the 4 5 gyr calculated history the stratified structure persists for 4 5 gyr when the reference mantle viscosity at 1573 k is higher than around 1020 pa s the planet thermally contracts by an amount comparable to the one suggested for mercury over the past 4 gyr mantle upwelling however generates magma only for the first 0 1 0 3 gyr at lower mantle viscosity in contrast a positive feedback between magmatism and mantle upwelling operates to cause episodic magmatism that continues for the first 0 3 0 8 gyr convective current stirs the mantle and eventually dissolves its stratified structure to enhance heat flow from the core and temporarily resurrect magmatism depending on the core size these models however predict larger contraction of the planet coupling between magmatism and mantle convection plays key roles in mantle evolution and the difficulty in numerically reproducing the history of magmatism of mercury without causing too large radial contraction of the planet warrants further exploration of this coupling

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

simulation of a surface penetrating radar for mars exploration 1 in the near future several exploratory missions to mars are planned which will include orbital radar sounders capable of characterizing the planet s subsurface structure to depths of up to a few kilometers due to the limited amount of resources concerning the properties of the martian soils in particular those governing electromagnetic propagation and scattering the ability of a radar system to detect and distinguish between subsurface interfaces is difficult to predict up to this time most radar sounding simulations have been based on simplified models and do not accurately account for many of the factors that influence the response to aid in the system evaluation and data interpretation for these missions we developed a radar simulator to accurately model the response for various geological conditions the simulator uses a frequency domain algorithm and is capable of modeling the effects of dielectric layering volume debris frequency dispersion ohmic losses and interface roughness in this paper a geophysical model appropriate to the radar simulator is described and the simulation algorithms are presented in detail factors influencing wave propagation and scattering are identified including those that directly impact radar performance specifically pertaining to expected penetration depths and unambiguous detection of water or ice finally using a set of standard crustal models of different geological regions simulation results are generated and presented

a combined spectrophotometric and morphometric study of the lunar mare dome fields near cauchy arago hortensius and milichius in this study we examine the spectral and morphometric properties of the four important lunar mare dome fields near cauchy arago hortensius and milichius we utilize clementine uv vis mulfispectral data to examine the soil composition of the mare domes while employing telescopic ccd imagery to compute digital elevation maps in order to determine their morphometric properties especially flank slope height and edifice volume after reviewing previous attempts to determine topographic data for lunar domes we propose an image based 3d reconstruction approach which is based on a combination of photoclinometry and shape from shading accordingly we devise a classification scheme for lunar marc domes which is based on a principal component analysis of the determined spectral and morphometric features for the effusive mare domes of the examined fields we establish four classes two of which are further divided into two subclasses respectively where each class represents distinct combinations of spectral and morphometric dome properties as a general trend shallow and steep domes formed out of low tio2 basalts are observed in the hortensius and milichius dome fields while the domes near cauchy and arago that consist of high tio2 basalts are all very shallow the intrusive domes of our data set cover a wide continuous range of spectral and morphometric quantities generally characterized by larger diameters and shallower flank slopes than effusive domes a comparison to effusive and intrusive mare domes in other lunar regions highland domes and lunar cones has shown that the examined four mare dome fields display such a richness in spectral properties and 3d dome shape that the established representation remains valid in a more global context furthermore we estimate the physical parameters of dome formation for the examined domes based on a rheologic model each class of effusive domes defined in terms of spectral and morphometric properties is characterized by its specific range of values for lava viscosity effusion rate and duration of the effusion process for our data set we report lava viscosities between about 10 2 and 10 8 pas effusion rates between 25 and 600 m 3 s 1 and durations of the effusion process between three weeks and 18 years lava viscosity decreases with increasing r 415 r 750 spectral ratio and thus tio2 content however the correlation is not strong implying an important influence of further parameters like effusion temperature on lava viscosity

petrogenesis and chronology of lunar meteorite northwest africa 4472 a kreepy regolith breccia from the moon northwest africa nwa 4472 is a polymict lunar regolith meteorite the sample is kreep rich high concentrations of potassium rare earth elements and phosphorus and comprises a heterogeneous array of lithic and mineral fragments these clasts and mineral fragments were sourced from a range of lunar rock types including the lunar high magnesian suite the high alkali suite kreep basalts mare basalts and a variety of impact crater environments the kreep rich nature of nwa 4472 indicates that the sample was ejected from regolith on the nearside of the moon in the procellarum kreep terrane and we have used lunar prospector gamma ray remote sensing data to show that the meteorite is most similar to and most likely sourced from regoliths adjacent to the imbrium impact basin u pb and pb pb age dates of nwa 4472 phosphate phases reveal that the breccia has sampled pre nectarian 4 35 ga rocks related to early episodes of kreep driven magmatism some younger phosphate u pb and pb pb age dates are likely indicative of impact resetting events at 3 9 4 ga consistent with the suggested timing of basin formation on the moon our study also shows that nwa 4472 has sampled impact melts and glass with an alkali depleted incompatible trace element rich high sc low rb th ratios low k compositional signature not related to typical apollo high k kreep or that sampled by kreepy lunar meteorite sayh al uhaymir sau 169 this provides evidence that there are numerous sources of kreep rich protoliths on the moon

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

ages and stratigraphy of mare basalts in oceanus procellarum mare nubium mare cognitum and mare insularum accurate estimates of mare basalt ages are necessary to place constraints on the duration and the flux of lunar volcanism as well as on the petrogenesis of lunar mare basalts and their relationship to the thermal evolution of the moon we performed new crater size frequency distribution measurements in order to investigate the stratigraphy of mare basalts in oceanus procellarum and related regions such as mare nubium mare cognitum and mare insularum we used high resolution clementine color data to define 86 spectrally homogeneous units within these basins which were then dated with crater counts on lunar orbiter iv images our crater size frequency distribution measurements define mineralogical and spectral surface units and offer significant improvements in accuracy over previous analyses our data show that volcanism in the investigated region was active over a long period of time from 3 93 to 1 2 b y a total of 2 7 b y volumetrically most of the basalts erupted in the late imbrian period between 3 3 and 3 7 b y and we see evidence that numerous units have been resurfaced during the eratosthenian period significantly less basalt was erupted depending on the absolute model ages that one can assign to the lunar chronostratigraphic systems five units might be of copernican age younger basalts are generally exposed in the center of the investigated area that is closer to the volcanic centers of the aristarchus plateau and marius hills older basalts occur preferentially along the northwestern margin of oceanus procellarum and in the southeastern regions of the studied area i e in mare cognitum and mare nubium combining the new data with our previously measured ages for basalts in mare imbrium serenitatis tranquillitatis humorum australe and humboldtianum we find that the period of active volcanism on the moon lasted 2 8 b y from 4 b y to 1 2 b y on the basis of the basalts dated so far which do not yet include the potentially young basalts of mare smythii e g schultz and spudis 1983 we conclude that oceanus procellarum not only exhibits the widest range of ages of all investigated basins but probably also is the location of some of the youngest basalts on the lunar surface

impact microcrater morphology on australasian microtektites scanning electron microscopy of 137 australasian microtektites and fragments from 4 sediment cores in the central indian ocean reveals more than 2000 impact generated features in the size range of 0 3 to 600 m 2 dominant crater number densities in m and sub m sizes therefore tektite producing impacts can lead to the generation of microcraters that mimic those found on lunar surface materials and for the lunar rocks to qualify as reliable cosmic dust flux detectors their tumbling histories and lunar surface orientations have to be known precisely

thermal history of the enstatite chondrites from silica polymorphs here we report the results of our petrologic and mineralogical study of enstatite e chondrites in order to explore their thermal histories we studied silica phases in 20 e chondrites by laser micro raman spectroscopy to determine the silica polymorphs they contain silica phases are commonly present in e chondrites and their polymorphs reflect the physical conditions of formation the samples studied here include eh3 5 el3 6 e chondrite melt rocks and an anomalous e chondrite we identified quartz tridymite cristobalite and silica glass in the samples studied eh4 5 and eh melt rocks are divided into high and low temperature classes based on niningeritealabandite solid solutions eh3 el3 and some eh melt rocks of the high temperature class contain tridymite and cristobalite we suggest that tridymite and cristobalite crystallized in chondrules and e chondrite melts followed by rapid cooling leading to the survival of these silica polymorphs eh4 and el4 chondrites also contain tridymite and cristobalite in their chondrules indicating that these silica polymorphs survived low temperature metamorphism as estimated from opaque mineral geothermometers because of the sluggishness of the transition to a more stable polymorph tridymite and cristobalite in el6 chondrites reflect the high temperature processes experienced by these meteorites on the other hand some eh5 chondrites and eh melt rocks of the low temperature class contain quartz which may be a product of the transition from tridymite or cristobalite during a long period of low temperature metamorphism although the thermal history of e chondrites have been previously estimated from opaque minerals such compositions mainly reflect low temperature processes however we can reconstruct the primordial thermal processes and subsequent cooling histories of e chondrites from their silica polymorphs the e chondrites have complicated thermal histories which produced the observed variations among them

global distribution of lunar composition new results from lunar prospector 1 maps of thorium th feo the ratio of epithermal to thermal neutrons e t and fast neutrons fn from lunar prospector were studied to determine their global distribution on the moon these distributions are compared to that of the 750 nm lunar albedo from clementine to aid in their interpretation all distributions were parameterized using a spherical harmonic expansion out to order l 30 resultant harmonic coefficients generally decrease with increasing l value as a power law in l for all five variables the axes of all dipole components l 1 cluster closely about a centroid given by 14 1 latitude and 16 4 west longitude this location is very close to the symmetry axes of their quadrupole components l 2 which cluster about a centroid given by 24 6 latitude and 25 1 west longitude both centroids are near the center of a suggested procellarum basin given by whitaker 1981 at 23 latitude and 15 west longitude this suggestion is strengthened by a sharp decrease of the intensities of all three variables at 50 from the centroids which is close to the boundary of the putative procellarum basin the coincidence of the global concentration of heat producing elements through th and mare deposits on the lunar surface through feo t e and fn with the circular outline of a putative procellarum basin suggests that the events that were responsible for producing oceanus procellarum perhaps a single giant impact must figure importantly in shaping the global distribution of surface composition a second apparently older circular structure having its center near 5 latitude and 65 east longitude and a radius of 50 is also hinted at in the data

the lunar rayed crater population characteristics of the spatial distribution and ray retention abstract the global statistics for young impact craters on the moon is used to unravel potential spatial asymmetries that may have been introduced by the particular orbital configuration of a synchronously rotating satellite only craters that exhibit bright ejecta rays extending for several crater radii were considered in this study this crater population is younger than about 750 ma the shape of the crater size frequency distribution does not show strong dependence on the target properties mare vs highlands however slightly lower frequencies indicate a shorter retention of the visibility of rays in mare units when their visibility is purely due to immaturity and not due to composition rays of small craters fade away much faster large old rayed craters sustain their visibility longer than the average crater population because of the compositional contrast between rays and mare material and thus obscure the cratering record when investigated for spatial variations using the existence of rays purely based on optical maturity instead of visibility as marker horizon for the copernican eratosthenian boundary suggests a shift from 1 1 ga to 750 ma the spatial distribution of lunar rayed craters namely the latitudinal and longitudinal frequency variations does not agree with previous analytical and numerical studies although there is an apparent hemispherical asymmetry centred close to the apex the density distribution is patchy and no predicted spatial pattern could be confirmed spatial distribution corrections accounting for the lower frequencies in the mare areas did not result in a better agreement with the analytical estimates density variations are less than 15 over vast parts of the lunar surface and the uncertainties for absolute surface ages are similar however variations of up to 50 are found even for the more numerous small craters these extreme values are located at high latitudes a combination of crater forming projectile flux distribution and micrometeorite bombardment which acts on maturation of the ray systems could prove as an explanation for the contradicting observed rayed crater distribution an analysis of the older craters is more challenging on the moon because earlier geological processes complicate the setting and the orbital configuration of the moon earth sun projectile system altered with time

the lassell massif a silicic lunar volcano abstract lunar surface volcanic processes are dominated by mare producing basaltic extrusions however spectral anomalies landform morphology and granitic or rhyolitic components found in the apollo sample suites indicate limited occurrences of non mare geochemically evolved si enriched volcanic deposits recent thermal infrared spectroscopy high resolution imagery and topographic data from the lunar reconnaissance orbiter lro show that most of the historic red spots and other less well known locations on the moon are indeed silica rich relative to basalt here we present a geologic investigation of the lassell massif 14 65 s 350 96 e near the center of alphonsus a basin in mare nubium where high silica thermal emission signals correspond with morphological indications of viscous possibly also explosive extrusion and small scale low reflectance deposits occur in a variety of stratigraphic relationships multiple layers with stair step lobate forms suggest different eruption events or pulsing within a single eruption absolute model ages derived from crater size frequency distributions csfds indicate that the northern parts of the massif were emplaced at 4 ga before the surrounding mare however csfds also indicate the possibility of more recent resurfacing events the complex resurfacing history might be explained by either continuous resurfacing due to mass wasting and or the emplacement of pyroclastics relatively low reflectance deposits are visible at meter scale resolutions below detection limits for compositional analysis at multiple locations across the massif suggestive of pyroclastic activity a quenched flow surface or late stage mafic materials compositional evidence from 7 band uv vis spectral data at the kilometer scale and morphologic evidence for possible caldera collapse and or explosive venting support the interpretation of a complex volcanic history for the lassell massif

shock metamorphism of ordinary chondrites a revised petrographic classification of progressive stages of shock metamorphism of ordinary chondrites is proposed six stages of shock s1 to s6 are defined based on shock effects in olivine and plagioclase as recognized by thin section microscopy the characteristic shock effects of each shock stage are s1 unshocked sharp optical extinction of olivine s2 very weakly shocked undulatory extinction of olivine s3 weakly shocked planar fractures in olivine s4 moderately shocked mosaicism in olivine s5 strongly shocked isotropization of plagioclase maskelynite and planar deformation features in olivine and s6 very strongly shocked recrystallization of olivine sometimes combined with phase transformations ringwoodite and or phases produced by dissociation reactions s6 effects are always restricted to regions adjacent to melted portions of a sample which is otherwise only strongly shocked in stages s3 to s6 localized melting results from stress and temperature peaks which locally deviate from the equilibration shock pressure due to differences in shock impedance these melting effects are a opaque melt veins shock veins b melt pockets with interconnecting melt veins c melt dikes and d troilite metal deposits in fractures based on a critical evaluation of data from shock recovery experiments a shock pressure calibration for the six shock stages is proposed which defines the s1 s2 s2 s3 s3 s4 s4 s5 and s5 s6 transitions at 5 5 10 15 20 30 35 and 45 55 gpa respectively whole rock melting and formation of impact melt rocks or melt breccias occurs at about 75 90 gpa the symbol for the shock stage may be used in combination with the symbol for the petrologic type to abbreviate the complete classification of a chondrite e g h5 s3 we propose this new shock classification and pressure calibration system to replace previous systems which are out of date with respect to the pressure calibration nominally restricted to l chondrites and based on incomplete and in part illdefined sets of shock effects we have classified seventy six ordinary chondrites using the new classification system and conclude the following 1 1 shock effects and the sequence of progressively increasing degrees of shock metamorphism are very similar in h l and ll groups differences in the frequency distribution of shock stages are relatively minor e g l chondrites appear to have the largest fraction with stages s5 and s6 this suggests that the collisional histories of the h l and ll parent bodies were similar 2 2 petrologic type 3 chondrites are deficient in stages s4 to s6 and with increasing petrologic type the frequency of stages s4 to s6 increases we suggest that the more porous and volatile rich type 3 chondrites are subject to melting at a lower shock pressure than the nonporous chondrites of higher petrologic type volatiles trapped in pores cause shock induced dispersal of the shocked and melted material into small particles which are not expected to survive as meteorites 3 3 stage s3 is the most abundant in nearly all petrologic types 4 4 at shock pressures in excess of about 35 gpa s5 and s6 4he and 40ar are almost completely lost pressures below 10 gpa s1 and s2 do not cause noble gas losses

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

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

origin and history of impact melt rocks of enstatite chondrite parentage we have conducted petrologic chemical and isotopic studies of two impact produced rocks of enstatite chondrite parentage ilafegh 009 is a total impact melt rock with no residual lithic clasts formation on the el chondrite parent body is suggested by its mineralogy and mineral compositions cooling of the impact melt was rapid at melt temperatures and decreased at subsolidus temperatures in contrast to previous studies we show that happy canyon is not a new enstatite achondrite but an impactmelt breccia of enstatite chondrite and not aubrite parentage this rock formed by impact melting and incorporation into the melt of clastic material which resulted in relatively rapid cooling at all temperatures mineralogical and bulk compositional data probably biased by the heterogeneous nature of this rock do not allow unequivocal determination of its parent body i e el vs eh although some data such as bulk total fe content seem to favor el parentage both rocks were subjected to post solidification shock which was more severe for ilafegh 009 than for happy canyon it appears that both impact melt rocks could have formed by impact melting 4 57 ga ago as is indicated by the nearly identical ixe closure ages of 1 6 and 1 4 ma before bjurbole for ilafegh 009 and happy canyon respectively an apparently younger 39ar40ar age of 4 53 ga for happy canyon may be due to small biases in the intercalibration of the ixe and 39ar40ar chronometers whereas the much younger 4 34 4 44 ga age for ilafegh 009 reflects thermal resetting during shock metamorphism shallowater which was impact derived from a different enstatite achondrite parent body has an ixe closure age 0 4 ma younger than that for ilafegh 009 and an 39ar40ar age of 4 53 ga the ancient ages of these three rocks attest to the intense early bombardment in this region of the solar system

global survey of lunar wrinkle ridge formation times abstract wrinkle ridges are a common feature of the lunar maria and record subsequent contraction of mare infill constraining the timing of wrinkle ridge formation from crater counts is challenging because they have limited areal extent and it is difficult to determine whether superposed craters post date ridge formation or have alternatively been uplifted by the deformation some wrinkle ridges do allow determination to be made this is possible where a ridge shows a sufficiently steep boundary or scarp that can be identified as deforming an intersecting crater or the crater obliterates the relief of the ridge such boundaries constitute only a small fraction of lunar wrinkle ridge structures yet they are sufficiently numerous to enable us to obtain statistically significant crater counts over systems of structurally related wrinkle ridges we carried out a global mapping of mare wrinkle ridges identifying appropriate boundaries for crater identification and mapping superposed craters selected groups of ridges were analyzed using the buffered crater counting method we found that except for the ridges in mare tranquilitatis the ridge groups formed with average ages between 3 5 and 3 1 ga ago or 100 650 ma after the oldest observable erupted basalts where they are located we interpret these results to suggest that local stresses from loading by basalt fill are the principal agent responsible for the formation of lunar wrinkle ridges as others have proposed we find a markedly longer interval before wrinkle ridge formation in tranquilitatis which likely indicates a different mechanism of stress accumulation at this site

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

emplacement and tectonic deformation of smooth plains in the caloris basin mercury abstract messenger s first flyby of mercury provided the first complete view of the caloris basin and its interior smooth plains multispectral imaging shows that the interior plains are spectrally distinct from surrounding terrain with a reflectance about 15 20 higher and a steeper spectral slope than the global average the caloris basin rim massifs and hummocky material in contrast have lower reflectance and a shallower spectral slope than the global average and extend around the entire basin isolated relatively red patches along the margins of caloris each surround irregularly shaped scalloped edged rimless depressions that are interpreted to be volcanic vents some with associated pyroclastic deposits a nearly continuous annulus of smooth plains exterior to the basin displays spectral characteristics that contrast sharply with those of the basin interior smooth plains the exterior smooth plains are lower in reflectance and spectrally similar to the caloris rim massifs and the hummocky materials the rims and floors of larger impact craters in the interior plains expose low reflectance material there is widespread evidence of contractional and extensional tectonic deformation of the caloris interior smooth plains a set of linear radial graben pantheon fossae radiates outward from a zone near the basin center and some of these graben extend to and intersect a set of generally basin concentric graben distributed along the outer margin of the caloris basin floor the average areal extensional strain expressed by the mapped system of graben is 0 08 wrinkle ridges also deform the interior smooth plains and predate both basin radial and basin concentric graben the average areal contractional strain expressed by the mapped wrinkle ridges is 0 07 the density of wrinkle ridges on the western interior smooth plains is less than on the eastern interior plains in contrast to the more even distribution of graben a similar difference is seen between the density of wrinkle ridges on the western and eastern exterior smooth plains with far fewer wrinkle ridges per unit area on the western annular plains superposition relations spectral contrast and the occurrence of volcanic vents and possible pyroclastic deposits all support a volcanic origin for the caloris interior plains crater counts indicate that the caloris exterior plains and hummocky material are younger than the caloris rim and interior plains and are therefore also likely volcanic in origin the contrast in spectral properties between the interior and exterior plains indicates a difference in the composition of the two expanses of volcanic material models for extensional tectonic deformation of the caloris basin interior inferred from the distribution of graben viewed by mariner 10 must be reevaluated to account for the discovery of pantheon fossae

lunar iron and optical maturity mapping results from partial least squares modeling of chang e 1 iim data abstract iron and optical maturity omat are two key geological marks of the moon that closely related to its geochemical evolution and interactions between surface and space environment we apply partial least squares pls regression to chang e 1 imaging interferometer iim 32 bands between 480 and 960 nm in mapping lunar global feo and omat and the feo and omat values are derived based on reasonable spectral parameters absorbance band ratios tio 2 and maturity sensitive parameters etc after been calibrated by the feo map from lunar prospector gamma ray spectrometer lp grs the global feo map derived from pls modeling shows a quantitatively more reasonable result consistent with previous remote sensing results lp as well as lunar feldspathic meteorite studies and chang e 3 landing site based on the new feo map by chang e 1 we discover a compositional inhomogeneity across lunar highland regions which has not been suggested by previous datasets e g clementine uvvis furthermore we suggest that at least part of the feo enrichments in highlands would be caused by mixing of highland and mare materials the iim derived omat map does not suggest a dichotomy of the lunar highlands and mare regions implying the compositional differences between those two terrains have been suppressed we further check the maturity effect for the young mare basalts 2 show a linear decrease with ages 2 units with ultrahigh feo 20 wt and ultrahigh tio 2 10 wt tend to have greater omat values and vary little with ages 3 this may be due to the distinct optical maturity effects of ultramafic minerals i e ultrahigh fe and ti and or the spectral blue shifts of abundant ilmenite

constraining the source regions of lunar meteorites using orbital geochemical data lunar meteorites provide important new samples of the moon remote from regions visited by the apollo and luna sample return missions petrologic and geochemical analysis of these meteorites combined with orbital remote sensing measurements have enabled additional discoveries about the composition and age of the lunar surface on a global scale however the interpretation of these samples is limited by the fact that we do not know the source region of any individual lunar meteorite here we investigate the link between meteorite and source region on the moon using the lunar prospector gamma ray spectrometer remote sensing data set for the elements fe ti and th the approach has been validated using apollo and luna bulk regolith samples and we have applied it to 48 meteorites excluding paired stones our approach is able broadly to differentiate the best compositional matches as potential regions of origin for the various classes of lunar meteorites basaltic and intermediate fe regolith breccia meteorites are found to have the best constrained potential launch sites with some impact breccias and pristine mare basalts also having reasonably well defined potential source regions launch areas for highland feldspathic meteorites are much less well constrained and the addition of another element such as mg will probably be required to identify potential source regions for these

pb pb geochronology petrography and chemistry of zr rich accessory minerals zirconolite tranquillityite and baddeleyite in mare basalt 10047 abstract in situ u pb isotopic measurements were carried out by ion microprobe on the zr rich accessory minerals zirconolite cazrti2o7 tranquillityite fe82 zry 2ti3si3o24 and baddeleyite zro2 in low k high ti mare basalt 10047 collected during the apollo 11 mission the analysed minerals are concentrated in pockets of late stage mesostasis that comprises an intergrowth of silica barian k feldspar and si al k glass from a phaneritic subophitic basalt comprising mainly pyroxene plagioclase ilmenite cristobalite and troilite most zr rich minerals are unaltered however some tranquillityite is replaced by a complex intergrowth of zirconolite baddeleyite ilmenite and fayalite suggesting that the mineral became unstable during crystallization several baddeleyite crystals have also undergone alteration to secondary zircon zirconolite was analysed in thin section 10047 11 and tranquillityite and baddeleyite in 10047 227 using a 6 m primary ion beam both zirconolite and tranquillityite have significant u and low initial pb contents and are highly suitable for pb pb dating fifteen analyses of zirconolite give a 207pb 206pb age of 3708 7 ma 207pb 206pb 204pb 206pb isochron 95 confidence including renormalisation of ratios and twenty five analyses of tranquillityite give 3710 6 ma the 207pb 206pb dates are consistent with each other and refine results from an earlier study baddeleyite data were less precise mainly due to lower secondary ionisation efficiency our results show that zirconolite and tranquillityite can provide precise isotopic dates and given their presence in other samples they represent important u pb chronometers for refining lunar geology

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

mineralogy of the lunar crust results from clementine received 1997 december 5 accepted in revised form 1998 september 15 abstract the central peaks of 109 impact craters across the moon are examined with clementine ultraviolet visible uvvis camera multispectral data the craters range in diameter from 40 to 180 km and are believed to have exhumed material from 5 30 km beneath the surface to form the peaks including both upper and lower crustal rocks depending on whether craters have impacted into highlands or basins representative five color spectra from spectrally and spatially distinct areas within the peaks are classified using spectral parameters including key ratio which is related to mafic mineral abundance and spectral curvature linked to absorption band shape which distinguishes between low and high ca pyroxene and olivine the spectral parameters are correlated to mineralogical abundances related in turn to highland plutonic rock compositions the derived rock compositions for the various central peaks are presented in a global map from these results it is evident that the lunar crust is compositionally diverse both globally and at local 100 m scales found within individual sets of central peaks although the central peaks compositions imply a crust that is generally consistent with previous models of crustal structure they also indicate a more anorthositic crust than generally assumed with a bulk plagioclase content of 8 1 evolving from pure anorthosite near the surface towards more mafic low ca pyroxene rich compositions with depth comparable to anorthositic norite evidence for mafic plutons occurs in both highlands and basins and represent all mafic highland rock types however the lower crust is more compositionally diverse than the highlands with both a greater range of rock types and more diversity within individual sets of central peaks

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

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

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

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

lunar rare earth element distribution and ramifications for feo and tio2 lunar prospector neutron spectrometer observations lunar prospector neutron spectrometer data have been used to map the global surface distribution of the incompatible rare earth elements gadolinium and samarium from the low altitude 30 15 km mapping orbit these results afford improved surface resolution and detailed views of the potassium rare earth elements and phosphorus kreep distribution within and around mare imbrium and elsewhere the gd and sm results serve as a complementary and independent check of the distribution of kreep on the moon in contrast with the lunar prospector gamma ray spectrometer results for thorium the neutron spectrometer observations reflect the presence of fe and ti as well as gd and sm the contributions of fe and ti are removed using high spatial resolution clementine spectral reflectance determinations of feo and tio2 abundances overall the resulting gd and sm abundance map agrees with the th abundance map determined using the lunar prospector gamma ray spectrometer in general the detailed features of the procellarum imbrium kreep terrane are found in both for example distinct highs in gd sm and th abundances are resolved over the craters mairan aristarchus kepler reinhold lalande and aristillus over the apennine bench and fra mauro regions and over the montes jura and montes carpatus indicating an enhanced abundance of kreep in these locations the neutron observations also provide constraints on feo and tio2 abundances for some high ti locales there is a significant disagreement with tio2 abundances inferred from clementine spectral reflectance

rugged lava flows on the moon revealed by earth based radar 1 basaltic volcanism is widespread on the lunar nearside and returned samples suggest that the mare forming magmas had low viscosity that led to primarily sheet like deposits new 70 cm wavelength radar observations that probe several meters beneath the lunar surface reveal differences in mare backscatter properties not explained by age or compositional variations we interpret areas of high backscatter and high circular polarization ratio in maria serenitatis imbrium and crisium as having an enhanced abundance of decimeter scale subsurface rocks relative to typical mare forming flows the 3 5 b y survival of these differences implies an initial platy blocky or ridged lava flow surface layer with thickness of at least 3 5 m such rugged morphology might arise from episodic changes in magma effusion rate as observed for disrupted flood basalt surfaces on the earth and mars very high flow velocities or increased viscosity due to a number of factors significant information on lunar mare eruption conditions may thus be obtained from long wavelength radar probing of the shallow subsurface

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

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

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

northwest africa 2526 a partial melt residue of enstatite chondrite parentage nwa 2526 is a coarse grained achondritic rock dominated by equigranular grains of polysynthetically twinned enstatite 85 vol with frequent 120 triple junctions and 10 15 vol of kamacite terrestrial weathering products all other phases including troilite daubreelite schreibersite and silica normative melt areas make up 1 vol of the rock oxygen isotopic analyses are well within the range of those for enstatite chondrites and aubrites we show that the enstatite achondrite russell et al 2005 northwest africa nwa 2526 is actually a partial melt residue of an enstatite chondrite like lithology that experienced 20 vol partial melting we suggest that the heat source was internal to the parent body the fes fe ni and plagioclase enstatite partial melts were removed from the parent lithology leaving nwa 2526 as a residue highly depleted in troilite and lacking plagioclase sub solidus slow cooling and annealing is responsible for the coarsegrained recrystallized texture of the rock we also suggest that the parent lithology of nwa 2526 prior to partial melting experienced a shock event which formed the curvilinear trails of blebs of minor troilite and rare metal that are enclosed in enstatite crystals thus these represent relicts after partial melting and annealing nwa 2526 experienced a second relatively mild impact event 20 gpa that caused formation of the polysynthetic twinning in the enstatite we suggest that the meteorite zaklodzie which has been referred to as a primitive enstatite achondrite przylibski et al 2005 did not form from a magma of internal origin but that it is an impact melt breccia of enstatite chondrite like parentage as previously discussed by burbine et al 2000 and keil 2007 finally the metal rich enstatite meteorite with achondritic texture itqiy patzer et al 2001 formed by processes very similar to those responsible for formation of nwa 2526 and is also the residue of 20 vol partial melting of an enstatite chondrite like parent lithology with the fes fe ni and plagioclase enstatite partial melts having been removed from the residue it also experienced an impact event after partial melting that was responsible for the formation of the mixed mg mn fesulfides and the shock stage s3 features of the enstatite these similarities indicate that nwa 2526 and itqiy may have formed on the same parent body this body was different from the eh el shallowater and aubrite parent bodies and nwa 2526 and itqiy may represent samples from yet another fifth enstatite meteorite parent body

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

thorium abundances on the lunar surface measurements of absolute thorium abundances on the lunar surface are presented using both the high and low altitude data taken with the lunar prospector gamma ray spectrometer an analysis of the uncertainties shows that the measured uncertainties are 7 g g are likely small area regions 150 km 2 using lunar topographic data we have shown that the thorium abundances in the lunar high lands and portions of south pole aitken spa basin are larger for lower elevations we have also studied a number of regions with anomalously high thorium abundances such as the northwestern region of spa basin the crater arago in western tranquillitatis and the compton belkovich region in the northeastern highlands the compton belkovich region appears to be enriched with evolved rocks such as alkali anorthosite and currently represents the only such extended region on the moon that has been identified in contrast tycho crater has very low thorium abundances which suggests that kreep was not assimilated at depth in this portion of the moon

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

ultramafic blocks from the ocean floor southwest of australia abstract samples dredged from the ocean floor near the junction of the naturaliste fracture zone and the diamantina zone 300 km southwest of cape leeuwin western australia contain 3 to 10 cm blocks of cr spinel lherzolites and al spinel olivine clinopyroxenites both assemblages show textural evidence for deformation and recrystallization with extensive development of kaersutite in one clinopyroxenite the blocks are enclosed by clay and fe mn oxide rich fragmental material which also contains a diverse detrital mineral suite and microfossils diopsides in the lherzolites are na and cr rich with marked similarities to those of lherzolite nodules in alkaline basaltic suites the al and ti rich diopsides of the clinopyroxenites are more magnesium than those of common pyroxene rich nodules the lherzolites are interpreted as upper mantle residues while the clinopyroxenites probably represent partly recrystallized cumulates from high temperature basaltic magmas traversing the lherzolite mantle both are thought to have been derived from an ultramafic body emplaced into the shallow crust near the cretaceous early tertiary continent ocean boundary off australia

mineralogy and crystallization history of the ilafegh 009 el chondritic impact melt rock an atem investigation abstract the ilafegh 009 meteorite is an impact melt rock from an el chondritic parent body its min eralogic assemblage is the result of rapid crystallization after shock induced melting we report here an analytical transmission electron microscopy atem study of the major minerals of this meteorite enstatite plagioclase fe ni metal and sulfides based on this study we discuss the crystallization sequence and the mer evolution of the rock in the solid state microstructure and microanalyses confm that the mineralogy of ilafegh 009 results from the crystalliza tion of an el chondritic melt the high compositional variability of plagioclases and the presence of silica rich glass pockets indicate fast cooling during crystallization the large enstatite grains trapped a large number of phases plagioclase silica rich glass and enstatite nuclei sulfides troilite alabandite and daubreelite form finely polycrystalline areas and reveal a complex crystallization sequence although fe ni metal grains formed during rapid cooling their microstructures show that some postsolidification process occurred in ilafegh 009 a large number of tiny ni p si rich precipitates were detected that formed as a result of exsolution of elements that become insoluble in kamacite at low temperature finally the microstructure dislocation arrangements and phase transformations observed in enstatite and fe ni metal attests that ilafegh 009 also experienced a moderate postsolidification shock event

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

3 1 ga crystallization age for magnesian and ferroan gabbro lithologies in the northwest africa 773 clan of lunar meteorites abstract the northwest africa nwa 773 clan of meteorites is a group of paired and or petrogenetically related stones that contain at least six different lithologies magnesian gabbro ferroan gabbro anorthositic gabbro olivine phyric basalt regolith breccia and polymict breccia uranium lead dates of baddeleyite in the magnesian gabbro ferroan gabbro and components within breccia lithologies of paired lunar meteorites nwa 773 nwa 3170 nwa 6950 and nwa 7007 indicate a chronologic link among the meteorites and their components a total of 50 baddeleyite grains were analyzed and yielded weighted average 207pb 206pb dates of 3119 4 9 4 n 27 3108 20 n 13 and 3113 15 n 10 ma for the magnesian gabbro ferroan gabbro and polymict breccia lithologies respectively a weighted average date of 3115 6 6 8 ma n 47 50 was calculated from the baddeleyite dates for all lithologies a single large zircon grain found in a lithic clast in the polymict breccia of nwa 773 yielded a u pb concordia date of 3953 18 ma indicating a much more ancient source for some of the components within the breccia a u pb concordia date of apatite and merrillite grains from the magnesian gabbro and polymict breccia lithologies in nwa 773 is 3112 33 ma identical to the baddeleyite dates magnesian and ferroan gabbros as well as the dated baddeleyite and ca phosphate bearing detritus in the breccia lithologies formed during the same igneous event at about 3115 ma these data also strengthen proposed petrogenetic connections between magnesian and ferroan gabbro lithologies which represent some of the youngest igneous rocks known from the moon

uranium lead systematics of low ti basaltic meteorite dhofar 287a affinity to apollo 15 green glasses article i nfo dhofar 287 is a lunar meteorite found in oman in 2001 which consists of a major portion 95 of low ti mare basalt dho 287a and a minor attached part 5 of regolith breccia dho 287b here we report the u pb systematics of dho 287a using data collected with a sensitive high resolution ion microprobe shrimp in situ analyses of five merrillite and three apatite grains which are resistant to secondary petrologic events resulted in a total pb u isochron age of 3 34 0 20 ga in 238 u 206 pb 207 pb 206 pb 204 pb 206 pb 3 d space 95 confidence level the observed pb pb isochron of these eight phosphates coupled with four plagioclase grains alsoyieldeda 207 pb 206 pbageof3 35 0 13ga thisformationage whenconsideredasthecrystallizationageof

global investigation of olivine on mars insights into crust and mantle compositions 1 we present the distribution of olivine on mars derived from spectral parameters based on the 1 m olivine absorption band the olivine can be defined with respect to two spectral end members type 1 corresponds to olivine with low iron content and or small grain size and or small abundance and type 2 which corresponds to olivine with higher iron content and or larger grain size and or larger abundance the spatial and statistical analysis of the global olivine distribution points out five major geological settings where olivine is detected 1 early hesperian olivine bearing smooth crater floors and flat intercrater plains throughout the southern highlands 2 olivine deposits around the three main basins argyre hellas and isidis 3 olivine in intercrater dunes crater ejecta or extended deposits in the northern plains 4 olivine associated with outcrops and sand in the floor of valles marineris and 5 olivine bearing butte outcrops in the vicinity of hellas the geological context the age and the composition of the olivine detections associated with these five major geological settings are detailed their origin and the implication of their occurrence on the composition of the martian mantle and crust as well as on the evolution of mars volcanism are discussed

extracting accurate and precise topography from lroc narrow angle camera stereo observations abstract the lunar reconnaissance orbiter camera lroc includes two identical narrow angle cameras nac that each provide 0 5 to 2 0 m scale images of the lunar surface although not designed as a stereo system lroc can acquire nac stereo observations over two or more orbits using at least one off nadir slew digital terrain models dtms are generated from sets of stereo images and registered to profiles from the lunar orbiter laser altimeter lola to improve absolute accuracy with current processing methods dtms have absolute accuracies better than the uncertainties of the lola profiles and relative vertical and horizontal precisions less than the pixel scale of the dtms 2 5 m we computed slope statistics from 81 highland and 31 mare dtms across a range of baselines for a baseline of 15 m the highland mean slope parameters are median 9 1 mean 11 0 standard deviation 7 0 for the mare the mean slope parameters are median 3 5 mean 4 9 standard deviation 4 5 the slope values for the highland terrain are steeper than previously reported likely due to a bias in targeting of the nac dtms toward higher relief features in the highland terrain overlapping dtms of single stereo sets were also combined to form larger area dtm mosaics that enable detailed characterization of large geomorphic features from one dtm mosaic we mapped a large viscous flow related to the orientale basin ejecta and estimated its thickness and volume to exceed 300 m and 500 km 3 respectively despite its 3 8 billion year age the flow still exhibits unconfined margin slopes above 30 in some cases exceeding the angle of repose consistent with deposition of material rich in impact melt we show that the nac stereo pairs and derived dtms represent an invaluable tool for science and exploration purposes at this date about 2 of the lunar surface is imaged in high resolution stereo and continued acquisition of stereo observations will serve to strengthen our knowledge of the moon and geologic processes that occur across all of the terrestrial planets

excavation of the lunar mantle by basin forming impact events on the moon abstract global maps of crustal thickness on the moon derived from gravity measurements obtained by nasa s gravity recovery and interior laboratory grail mission have shown that the lunar crust is thinner than previously thought hyperspectral data obtained by the kaguya mission have also documented areas rich in olivine that have been interpreted as material excavated from the mantle by some of the largest lunar impact events numerical simulations were performed with the isale 2d hydrocode to investigate the conditions under which mantle material may have been excavated during large impact events and where such material should be found the results show that excavation of the mantle could have occurred during formation of the several largest impact basins on the nearside hemisphere as well as the moscoviense basin on the farside hemisphere even though large areas in the central portions of these basins were later covered by mare basaltic lava flows surficial lunar mantle deposits are predicted in areas external to these maria our results support the interpretation that the high olivine abundances detected by the kaguya spacecraft could indeed be derived from the lunar mantle

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

young mare volcanism in the orientale region contemporary with the procellarum kreep terrane pkt volcanism peak period 2 billion years ago 1 the crater retention ages of the mare deposits within the orientale multi ring impact basin are investigated using 10 m resolution images obtained by the selene kaguya spacecraft in order to constrain the volcanic history of the moon around the nearside farside boundary precise crater counting analyses reveal that mare deposits in the orientale region are much younger than previously estimated 2 9 ga mare basalt in the eastern part of mare orientale and 1 8 2 2 ga mare deposits in lacus veris and lacus autumni maria along the northeastern rings of the basin the latter age estimates indicate that the orientale region experienced volcanic activities 2 billion years after the basin formation impact the dominance of a uniform surface age across the mare deposits in the peripheral regions strongly suggests that these volcanic eruptions are contemporary with the elevated volcanic activity episode proposed for the procellarum kreep terrane on the lunar nearside at 2 ga and that this activity peak is much more widespread than previously estimated the longevity of mare volcanism in the orientale region further suggests high initial temperatures and or high content of heat producing elements in the underlying mantle of this region

timing and characteristics of the latest mare eruption on the moon unraveling the timing and duration of mare volcanism on the moon is essential for understanding its thermal evolution the end of mare volcanism is poorly constrained because mare basalts are incompletely sampled in this study employing selene kaguya high resolution images we performed new crater size frequency measurements for 49 young mare units 3 0 ga in the procellarum kreep terrane pkt in which the latest magma eruption of the moon occurred mare volcanism in this region continued until 1 5 ga suggesting that volcanic activity in this region ceased 1 0 ga after the magma eruption had globally ceased 2 5 3 0 ga volcanic activity may have peaked 1 8 2 2 ga ago the youngest basalts occur around the aristarchus plateau and the kepler crater which are located in the central region of the pkt it is likely that heating in the crust due to the concentration of heat producing elements in the pkt delayed cooling of a partial melting zone in the underlying mantle in contrast with previous basalt dating in this region our results indicate a higher correlation between ages and spectral types of mare basalts the young mare units in the pkt tend to have spectral types corresponding to high titanium contents while low titanium basalts occur mainly in the early stage the titanium variation in mare basalts may reflect vertical heterogeneity in tio2 content in the upper mantle beneath the pkt

improved discrimination of volcanic complexes tectonic features and regolith properties in mare serenitatis from earth based radar mapping radar images at 70 cm wavelength show 4 5 db variations in backscatter strength within regions of relatively uniform spectral reflectance properties in central and northern mare serenitatis delineating features suggesting lava flow margins channels and superposition relationships these backscatter differences are much less pronounced at 12 6 cm wavelength consistent with a large component of the 70 cm echo arising from the rough or blocky transition zone between the mare regolith and the intact bedrock such deep probing is possible because the ilmenite content which modulates microwave losses of central mare serenitatis is generally low 2 3 by weight modeling of the radar returns from a buried interface shows that an average regolith thickness of 10 m could lead to the observed shifts in 70 cm echo power with a change in tio2 content from 2 to 3 this thickness is consistent with estimates of regolith depth 10 15 m based on the smallest diameter for which fresh craters have obvious blocky ejecta the 70 cm backscatter differences provide a view of mare flow unit boundaries channels and lobes unseen by other remote sensing methods a localized pyroclastic deposit associated with rima calippus is identified based on its low radar echo strength radar mapping also improves delineation of units for crater age dating and highlights a 250 km long east west trending feature in northern mare serenitatis that we suggest is a large graben flooded by late stage mare flows

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

a catalogue of impact craters larger than 200 m and surface age analysis in the chang e 5 landing area abstract chang e 5 ce 5 is the first sample return mission of china s lunar exploration and will be launched in 2020 the planned landing area is near mons rumker in oceanus procellarum it is important to have a detailed geological analysis of the landing area prior to the lunar sample collection the crater size frequency distribution curve combined with radioisotope dating of components of the returned sample by ce 5 may allow a refinement of the lunar chronology function based on a digital orthophoto map with a pixel size of 1 5 m generated from more than 700 lunar reconnaissance orbiter camera narrow angle camera images of the ce 5 landing area all impact craters larger than 200 m in diameter were extracted using the resultant crater catalogue of 32 277 craters a systematic analysis of the landing area including the crater distribution morphology characteristics and geologic model ages is conducted the results show that craters smaller than 1 000 m are denser in the east and the west parts of the region while those larger than 1 000 m tend to be more concentrated in the central part particularly within the range of 61 5 w 64 5 w within nine geologic units divided using the spectral characteristics the geologic unit of em1 eratosthenian aged mare em near the mons rumker is the youngest with a model age of 2 02 0 16 0 16 ga the three rumker plateau ir units are the oldest parts of the landing area with the largest model age of 3 49 0 12 0 073 ga the crater catalogue and the surface model age analysis results can contribute to the ce 5 mission as well as further scientific research

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

intensive parameters of enstatite chondrite metamorphism abstract the enstatite oldhamite geothermometer eog developed by larimer and buseck 1974 makes use of the five phase assemblage kamacite quartz enstatite oldhamite troilite to determine metamorphic temperatures in enstatite chondrites a re evaluation of the thermodynamic foundation of the eog shows that several of the assumptions and approximations can be significantly improved with new thermodynamic data the geothermometer has been modified to reflect among other things the solution behavior of si in kamacite the solution behavior of a calcium silicate component in enstatite and metal sulfide fusion as a function of temperature and composition an analysis of the eog shows that the activity coefficient of si in kamacite and the ca rich component of enstatite are the model s most important parameters for si the activity coefficient data of sakao and elliot 1975 have been used the activity coefficient of a ca rich component of enstatite presents a unique problem since data on this parameter do not exist for one pyroxene systems and two pyroxene solution models do not provide unique activity coefficients in the absence of diopside the model therefore has been formulated using camgsi 2 o 6 as the ca rich component of enstatite and assumes that it behaves as a symmetric regular margules solution the margules interaction parameter w g is then used as an adjustable constant and is varied such that the resulting temperatures fall between minimum and maximum temperatures determined independently temperature minima were determined from the enstatite diopside solvus of carlson 1986 and indicate that the el6 chondrites have been metamorphosed to temperatures exceeding 900 1000 c the temperature of the enstatite plagioclase quartz eutectic 1090 c appropriate for el6 plagioclase compositions was used as the metamorphic maxima with these constraints a w g value of 52 kj mole was estimated as appropriate within the context of the model for el6 metamorphic conditions el6 temperatures determined via this method range from 981 c for yilmia to 1068 c for blithfield temperature estimates of greater than 1000 c for the highly equilibrated el6 chondrites require the formation of a metal sulfide liquid during metamorphism liquid fractionation of this predominantly fe fes liquid could explain the siderophile chalcophile and volatile element depletion in the el6 class relative to ci and eh chondrites liquid fractionation however is not required by the model and is consistent with a moderate cooling rate which is fast enough to lock in high cao contents in enstatite but slow enough to re equilibrate troilite and alabandite to low temperatures the oxygen fugacity determined in this study shows the enstatite chondrites to have equilibrated at extremely low f o 2 this as well as the activity of si that can be extracted from the eog indicates that the enstatite chondrites that contain sinoite si 2 n 2 o equilibrated under high nitrogen fugacities high f n 2 values imply that sinoite bearing e chondrites either formed in a nebula of high pressure f n 2 10 1 at 1050 c or more likely are products of planetary metamorphism

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

distribution of the subsurface reflectors of the western nearside maria observed from kaguya with lunar radar sounder 1 the lunar radar sounder lrs performed global soundings and detected possible subsurface echoes at the nearside maria this paper examines the relationship between the distribution of the detected subsurface echoes and the surface ages in the western nearside maria continuous subsurface reflectors are clearly detected only in a few areas consisting of about 10 of the western nearside maria at apparent depths from hundreds to more than a thousand meters these reflectors are not generally the basements of the mare but are the interface between different basaltic rock facies comparison between the distribution of the detected subsurface boundaries and the surface ages suggests that most of the detected subsurface reflectors were formed more than 3 4 billion years ago based on the strong connection between the accumulation rate of regolith and the absolute age the detected subsurface boundaries appear to be relatively thick regolith layers accumulated during the depositional hiatuses of basaltic lavas