geochemistry of diogenites still more diversity in their parental melts we report on the major and trace element abundances of 18 diogenites and o isotopes for 3 of them our analyses extend significantly the diogenite compositional range both in respect of mg rich e g meteorite hills met 00425 mgo 31 5 wt and mg poor varieties e g dhofar 700 mgo 23 wt the wide ranges of siderophile and chalcophile element abundances are well explained by the presence of inhomogeneously distributed sulfide or metal grains within the analyzed chips the behavior of incompatible elements in diogenites is more complex as exemplified by the diversity of their ree patterns apart from a few diogenite samples that contain minute amounts of phosphate and whose incompatible element abundances are unlike the orthopyroxene ones the range of incompatible element abundances and particularly the range of dy yb ratios in diogenites is best explained by the diversity of their parental melts we estimate that the feo mgo ratios of the diogenite parental melts range from about 1 4 to 3 5 and therefore largely overlap the values obtained for non cumulate eucrites our results rule out the often accepted view that all the diogenites formed from parental melts more primitive than eucrites during the crystallization of a magma ocean instead they point to a more complex history and suggest that diogenites were derived from liquids produced by the remelting of cumulates formed from the magma ocean

definitive evidence of hesperian basalt in acidalia and chryse planitiae 1 the surface materials of acidalia and chryse planitiae mars have been variably interpreted morphologically as basalt and compositionally as andesite or altered basalt a thorough survey using the compact reconnaissance imaging spectrometer for mars crism near infrared spectrometer reveals olivine and high calcium pyroxene signatures in the shallow subsurface exposed by impact craters these signatures indicate that the near surface of these regions are primarily basaltic in nature and are similar to other regions of hesperian volcanism across mars e g syrtis major previous spectroscopic studies using coarser resolution data sets have failed to identify these mafic signatures due to obscuration of the underlying material in addition to the relatively small scale exposures in impact craters the nature of the surficial obscuration material is likely multifaceted and includes the deposition of latitude dependent mantling material and the presence of alteration rinds this observation shows that the northern plains of mars are basaltic and must be factored into the thermal and surficial evolution of mars

mineralogical records of early planetary processes on the howardite eucrite diogenite parent body with reference to vesta abstract mineralogical information recovered from the howardite eucrite diogenite hed meteorites was employed to reconstruct the history of the parent body and relate it to 4 vesta these interpreted crustal evolution processes were then compared to the expected geological features on the surface of a likely proto planet 4 vesta the original crustal materials of the hed parent body were preserved as mineral grains and lithic clasts but in many eucrites fe mg ratios in pyroxenes were homogenized by diffusion after crystallization the crystallization trend of the protocrust has been deciphered by 1 examining monomict and crystalline samples and using their mineralogical and chemical information to formulate a sequence of crystallization and cooling trends and by 2 reconstructing the original crust prior to cratering events from lithic clasts and mineral fragments in polymict breccias such as howardites and polymict eucrites mineral components are identical both in the individual hed and in polymict breccias and no remnants of primitive materials were preserved in the polymict breccias a layered crust model reconstructed from such breccias consists of an upper crust with extrusive lava like eucrites that have been brecciated and metamorphosed diogenite mantle and cumulate eucrites of varying thickness between them this model can be used to explain the surface geological features of vesta observed from the hubble space telescope a large crater with diogenitic orthopyroxene at the crater floor is consistent with the deepest diogenitic layer of the layered crust model and an underlying olivine layer is expected from early crystallized olivine in the crystal fractionation model the old terrain of eucritic surface materials of vesta can be howardites polymict eucrites or regolith like eucrites produced from eucrites extruded and impacted on the surface partial melting models of eucrites seem to be favored by the rare earth element ree chemistry and experimental studies unfortunately partial melting models have not demonstrated how the hed parent body is converted to a layered crust without producing any metamorphosed primitive material in the layered crust the origin of cumulate eucrites with systematic variation of textures and chemistries of pyroxene can be explained by the layered crust model with excavation and mixing of trapped liquid discovery of basaltic materials with na rich plagioclase and augite in iron meteorites which are the products of partial melting suggests that eucrites may be unique to a body that underwent large scale differentiation and metamorphism

the geologically recent giant impact basins at vesta s south pole since 17 july 2011 nasa s spacecraft dawn has been orbiting the asteroid vesta the second most massive and the third largest asteroid in the solar system see the cover russell et al p 684 1 use dawn s observations to confirm that vesta is a small differentiated planetary body with an inner core and represents a surviving proto planet from the earliest epoch of solar system formation vesta is also confirmed as the source of the howardite eucrite diogenite hed meteorites jaumann et al p 687 2 report on the asteroid s overall geometry and topography based on global surface mapping vesta s surface is dominated by numerous impact craters and large troughs around the equatorial region marchi et al p 690 3 report on vesta s complex cratering history and constrain the age of some of its major regions based on crater counts schenk et al p 694 4 describe two giant impact basins located at the asteroid s south pole both basins are young and excavated enough amounts of material to form the vestoids a group of asteroids with a composition similar to that of vesta and hed meteorites de sanctis et al p 697 5 present the mineralogical characterization of vesta based on data obtained by dawn s visual and infrared spectrometer revealing that this asteroid underwent a complex magmatic evolution that led to a differentiated crust and mantle the global color variations detailed by reddy et al p 700 6 are unlike those of any other asteroid observed so far and are also indicative of a preserved differentiated proto planet 1 lookup doi 10 1126 science 1219381 2 lookup doi 10 1126 science 1219122 3 lookup doi 10 1126 science 1218757 4 lookup doi 10 1126 science 1223272 5 lookup doi 10 1126 science 1219270 6 lookup doi 10 1126 science 1219088

petrogenetic relationships between diogenites and olivine diogenites implications for magmatism on the hed parent body abstract diogenites are orthopyroxenites and harzburgites that are petrogenetically associated with basaltic magmatism linked to the earliest stages of asteroidal melting on the parent body for the howardite eucrite diogenite hed meteorites there are several models proposed for their origin 1 accumulation of orthopyroxene opx chromite chr olivine ol during the crystallization of a magma ocean during the initial stages of asteroidal differentiation 2 accumulation of opx chr ol during the crystallization of compositionally distinct basaltic magmas emplaced into the crust of the hed parent body and 3 the orthopyroxenites formed by the crystallization of basaltic magmas within the hed parent body crust whereas the harzburgites represent the mantle of the hed parent body although ol and opx experienced varying degrees of subsolidus reequilibration 1100 700 c their minor and trace element characteristics appear to partially preserve magmatic signatures that provide insights into distinguishing among different models for the origin of diogenites the opx exhibits a continuous and very systematic variation in incompatible elements such as al ti zr y and yb polymict diogenites i e roda eet 79002 can contain distinct lithologies with both different incompatible element characteristics and different model abundances of ol there appears to be no relationship between the appearance and abundance of ol and the incompatible element characteristics of the opx the ol exhibits a range in mg and systematic variations ni co ni co and mn for examples low ni co appears to be closely associated with the harzburgites and ni and mn exhibit a negative correlation surprisingly incompatible element concentrations in opx are not negatively correlated to ni concentrations in ol the continuous nature of the minor and trace element characteristics of the opx and ol is consistent with the all the diogenite lithologies forming through a single process such as crystallization within a magma ocean or a series of layered intrusions further the range in incompatible element variability in the opx the ni and co systematics in the ol and the association of distinctly different lithologies within polymict diogenites are most consistent with the diogenites representing lithologies from diverse layered intrusions alternatively they may represent crystallization products of a magma ocean much more complex than has been thus far proposed i e multiple mos there are some distinct differences between diogenites and the ol rich achondrite que 93148 that was also analyzed during this study these differences such as ni co in ol estimated conditions of fo2 suggest that que 93148 is closely related to main group pallasites rather than the parent bodies for the hed meteorites

mega ejecta on asteroid vesta 1 asteroid 4 vesta sometimes called the smallest terrestrial planet will be orbited next july by nasa s dawn mission this will be the first time a small planet is visited by a spacecraft and novel geological structures are expected a key issue regarding vesta mean diameter 530 km is to what extent its geology is dominated by the 460 km diameter impact basin on its southern hemisphere we model the basin s formation using a very high resolution 3d smooth particle hydrodynamics simulation to establish some of the major impact related aspects of vesta s geology the goal is to provide a framework for interpreting anticipated observations of landforms a collision of this magnitude a 50 km diameter impactor at 5 km s exposes many deep strata from within the planet and offsets the center of mass by 10 km from the center of figure vesta spins every 5 3 hr so that a hemispheric scale impact evolves in a non inertial frame and deposits variably shaped multiply folded and abruptly terminated ejecta sequences of regional scale since little of this ejecta would have been molten these massive sequenced deposits could be mistaken in images of vesta for other geologic forms such as thrusts and folds detailed mapping and the piecing together of mega ejecta via impact models will enable an informed understanding of the interior geology of vesta

quantitative compositional analysis of martian mafic regions using the mex omega reflectance data 2 petrological implications abstract the primary objectives of this paper are to determine the modal mineralogy of selected low albedo terrains of different ages ranging from noachian to amazonian exposed on the surface of mars this analysis is conducted using the spectral modeling of the observatoire pour la mineralogie l eau les glaces et l activite omega reflectance data results from this work are consistent with the major results of previous spectroscopic studies plagioclase 40 60 in volume and high calcium pyroxene 20 40 hcp are the dominant minerals of the most regions low calcium pyroxene 10 15 lcp and minor amounts of olivine are also present the oldest terrains are characterized by the largest amount of lcp and the lowest concentration of plagioclase these overall compositions are consistent with two pyroxene basalts the particle sizes are in the range of a few hundreds of micrometers which is in good agreement with the thermal inertia of the martian low albedo regions in the region around the nili fossae localized concentrations of olivine up to 40 with millimeter particle size similar to picritic basalts observed in situ by the spirit rover in the gusev crater are inferred chemical compositions are calculated for the first time from omega spectra they are quite consistent with gusev rocks and shergottite compositions but they appear to be significantly sio2 poorer than thermal emission spectrometer data a decreasing low calcium pyroxene abundance with the decreasing age of the low albedo regions is reported this may be indicative of decreasing degree of partial melting as thermal flux decreases with time we propose that the ancient noachian aged lcp rich terrains could have been formed from h2o bearing melts then dry basaltic volcanism occurred leading to decreasing lcp abundance with time due to decreasing degree of partial melting the olivine bearing material modeled in nili fossae resembles the composition of alh77005 and chassigny meteorites consistent with prior studies implications on the formation of the basaltic shergottites are discussed

petrologic insights from the spectra of the unbrecciated eucrites implications for vesta and basaltic asteroids we investigate the relationship between the petrology and visible near infrared spectra of the unbrecciated eucrites and synthetic pyroxene plagioclase mixtures to determine how spectra obtained by the dawn mission could distinguish between several models that have been suggested for the petrogenesis of vesta s crust e g partial melting and magma ocean here we study the spectra of petrologically characterized unbrecciated eucrites to establish spectral observables which can be used to yield mineral abundances and compositions consistent with petrologic observations no information about plagioclase could be extracted from the eucrite spectra in contrast pyroxene dominates the spectra of the eucrites and absorption band modeling provides a good estimate of the relative proportions of low and high ca pyroxene present cr is a compatible element in eucrite pyroxene and is enriched in samples from primitive melts an absorption at 0 6 lm resulting from cr 3 in the pyroxene structure can be used to distinguish these primitive eucrites the spectral differences present among the eucrites may allow dawn to distinguish between the two main competing models proposed for the petrogenesis of vesta magma ocean and partial melting these models predict different crustal structures and scales of heterogeneity which can be observed spectrally the formation of eucrite allan hills alh a81001 which is primitive cr rich and relatively unmetamorphosed is hard to explain in the magma ocean model it could only have been formed as a quench crust if the magma ocean model is correct then alha81001 like material should be abundant on the surface of vesta and the vestoids

vesta s shape and morphology vesta s surface is characterized by abundant impact craters some with preserved ejecta blankets large troughs extending around the equatorial region enigmatic dark material and widespread mass wasting but as yet an absence of volcanic features abundant steep slopes indicate that impact generated surface regolith is underlain by bedrock dawn observations confirm the large impact basin rheasilvia at vesta s south pole and reveal evidence for an earlier underlying large basin veneneia vesta s geology displays morphological features characteristic of the moon and terrestrial planets as well as those of other asteroids underscoring vesta s unique role as a transitional solar system body

surface lithologic heterogeneity of asteroid 4 vesta abstract high precision spectrophotometry of 4 vesta the third largest asteroid was used to establish the surface composition of this body and to investigate mineralogical variations across its surface the average surface of vesta is analogous to howardite and or polymict eucrite assemblages regolith derived members of the hed meteorite suite which consist of a eucrite matrix containing differing amounts of a diogenite component color and or spectral changes which exhibit a consistent relationship to rotational phasing are evident in 16 of 18 studies of vesta dating back to 1929 including the present work after elimination of possible sources of spurious spectral or color changes it is concluded that these variations arise from hemispheric variations in surface materials and hence provide a means of spatially resolving subhemispheric compositional units on the surface of vesta the background surface of vesta is a relatively dark howardite or polymict eucrite pyroxene plagioclase assemblage with several compositionally distinct bright regions clustered in one hemisphere viewed around the maximum in vesta s lightcurve these include what appears to be an olivine bearing unit suggested name leslie formation located near vesta s equator which probably represents an impact basin and or its associated ejecta that penetrated through the basaltic crust other high albedo compositional units including an apparently low calcium eucrite region and several diogenite pyroxenite regions at least one located near the southern pole may be smaller shallower impact basins by analogy to the eucrite meteorites which represent surface flows or shallow intrusions and which constitute the major component of the regolith derived howardites and polymict eucrites we conclude that the howardite polymict eucrite units represent a regolith gardened original surface of vesta it is probable that the low albedo of the background surface on vesta is due to an age related darkening effect similar to that inferred from the galileo images of gaspra and ida this mechanism is consistent with the correlation of absorption feature intensity with the lightcurve vesta appears to have an old eucritic surface darkened with age and represented among the meteorites by the regolith derived howardites and polymict eucrites on which several impacts on one hemisphere have exposed fresher brighter diogenite and olivine bearing material based on qualitative analysis of the mineralogical variations as a function of rotation a generalized lithologic map of vesta was produced there is reasonable control on the longitude of lithologic features but little control on their latitudes except where specifically noted in producing this map discrete circular features were used on the plausible assumption that impacts have been the most important geologic process on this surface for most of the age of the solar system the shape of the features has thus been assumed rather than derived and is subject to future revision as data improve

the violent collisional history of asteroid 4 vesta vesta is a large differentiated rocky body in the main asteroid belt that accreted within the first few million years after the formation of the earliest solar system solids the dawn spacecraft extensively imaged vesta s surface revealing a collision dominated history results show that vesta s cratering record has a strong north south dichotomy vesta s northern heavily cratered terrains retain much of their earliest history the southern hemisphere was reset however by two major collisions in more recent times we estimate that the youngest of these impact structures about 500 kilometers across formed about 1 billion years ago in agreement with estimates of vesta asteroid family age based on dynamical and collisional constraints supporting the notion that the vesta asteroid family was formed during this event

dawn completes its mission at 4 vesta the dawn mission was designed to test our hypothesis about the origin and evolution of the early solar system by visiting the largest differentiated basaltic asteroid 4 vesta believed to be a survivor from the earliest times of rocky body formation observations from orbit show that vesta is the parent body of the howardite eucrite diogenite meteorites vesta has an iron core and a eucritic diogenitic crust its surface is characterized by abundant impact craters but with no evident volcanic features it has two ancient impact basins in the southern hemisphere that are associated with circum planetary troughs the northern hemisphere is the more heavily cratered and contains the oldest terrains the surface of vesta is diverse with north south and east west dichotomies in the eucrite to diogenite ratio its surface contains both very bright and very dark material and its color varies strongly from region to region both the mineralogical and the elemental compositions agree with that expected for the hed parent body significant oh or h may be present in the upper crust and the presence of pits in fresh craters is consistent with the devolatilization of the surface after a collision either brought to or tapped a source of water on vesta the presence of dark material on the surface of vesta suggests efficient transport pathways for organic material and the mixing of the dark material with the more pristine pyroxene explains the varying albedo across the surface vesta has proven to be a reliable witness to the formation of the solar system

impact excavation on asteroid 4 vesta hubble space telescope results hubble space telescope images of asteroid 4 vesta obtained during the favorable 1996 apparition show an impact crater 460 kilometers in diameter near the south pole color measurements within the 13 kilometer deep crater are consistent with excavation deep into a high calcium pyroxene rich crust or olivine upper mantle about 1 percent of vesta was excavated by the crater formation event a volume sufficient to account for the family of small vesta like asteroids that extends to dynamical source regions for meteorites this crater may be the site of origin for the howardite eucrite and diogenite classes of basaltic achondrite meteorites

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

introduction the geologic mapping of vesta the purpose of this paper is to introduce the geologic mapping of vesta special issue section of icarus which includes several papers containing geologic maps of the surface of vesta made to support data analysis conducted by the dawn science team during the vesta encounter july 2011 september 2012 in this paper we briefly discuss pre dawn knowledge of vesta provide the goals of our geologic mapping campaign discuss the methodologies and materials used for geologic mapping review the global geologic context of vesta discuss the challenges of mapping the geology of vesta as a small airless body and describe the content of the papers in this special issue section we conclude with a discussion of lessons learned from our quadrangle based mapping effort and provide recommendations for conducting mapping campaigns as part of planetary spacecraft nominal missions

the genesis of diogenites and hed parent body petrogenesis abstract samples of clasts and whole rocks from eighteen of the twenty four known diogenites orthopyroxenite breccia meteorites have been studied by combined inaa empa in order to elucidate their petrogenetic history the incompatible elements a12o3 and tio2 are positively correlated in diogenite orthopyroxenes these elements determined by empa are also positively correlated with incompatible trace elements such as yb determined by inaa on bulk samples these correlations indicate that most diogenites may form a single igneous fractionation sequence the incompatible minor and trace elements are decoupled from the major elements for essentially constant mg tio2 varies by about 4 times and yb by about 8 times hence there is no strong evidence for igneous fractionation preserved in the major element composition of orthopyroxenes geothermometry calculations using two pyroxene and spinelorthopyroxene thermometers show that these phases in diogenites maintained equilibrium to temperatures in the range 650 880 c far below likely magmatic temperatures in some diogenites orthopyroxenes of differing composition are in breccia contact therefore the low equilibration temperatures were achieved in the diogenites prior to brecciation decoupling of major and trace elements was most likely caused by slow subsolidus cooling in the diogenite pluton which allowed ca fe and mg to reach diffusive equilibration incompatible trace elements likely have much lower diffusivities in orthopyroxene and therefore may have largely preserved their magmatic distributions the extensive variation in incompatible trace elements indicates that either the diogenites were formed through an extensive crystallization interval or that partition coefficients greatly increased during crystallization if the former were true one would expect to find substantial amounts of plagioclase in the diogenites if they are comagmatic with eucrites this is contrary to observations a model in which diogenites crystallized from one or more melts of approximately orthopyroxenitic composition can satisfy both the mineralogie and trace element constraints

petrology of the unbrecciated eucrites abstract twenty nine unbrecciated eucrites have been thoroughly characterized in terms of the petrologic factors that affect their spectra such as mineral chemistry modal adundances grain sizes and textures we have conducted a combined petrologic and spectral study designed to provide insight into the petrogenesis of the basaltic crust of vesta and the variety of rock types that exist within it as well as aid in the petrologic interpretation of spectra to be collected by the dawn orbiting spacecraft this paper details the petrology part of the study unbrecciated eucrite samples were selected to avoid the complications of lithologic mixing in the accompanying spectral study a wide variety of textural types are seen within the basaltic eucrites encompassing quenched coarse grained and granoblastic samples zoned pyroxenes in eucrites and those that preserve a history of initial rapid cooling are rare nearly all eucrite samples have been thermally metamorphosed and would commonly be classified as equilibrated however this term reflects only the quadrilateral mg fe and ca compositions of pyroxenes and considerable variations are seen within the minor elements al ti and cr in pyroxenes as well as plagioclase compositions determination of both pyroxene and plagioclase compositions together with pyroxene geothermometry provides a better estimate for the relative degree of thermal metamorphism a eucrite has experienced the petrologic differences observed here might allow different eucrites to be distinguished spectrally this is especially true for the varying pyroxene compositions as the spectra of eucrites are dominated by absorption features attributed to pyroxene

compositional diversity and geologic insights of the aristarchus crater from moon mineralogy mapper data 1 the moon mineralogy mapper m3 acquired high spatial and spectral resolution data of the aristarchus plateau with 140 m pixel in 85 spectral bands from 0 43 to 3 0 m the data were collected as radiance and converted to reflectance using the observational constraints and a solar spectrum scaled to the moon sun distance summary spectral parameters for the area of mafic silicate 1 and 2 m bands were calculated from the m3 data and used to map the distribution of key units that were then analyzed in detail with the spectral data this analysis focuses on five key compositional units in the region 1 the central peaks are shown to be strongly enriched in feldspar and are likely from the upper plagioclase rich crust of the moon 2 the impact melt is compositionally diverse with clear signatures of feldspathic crust olivine and glass 3 the crater walls and ejecta show a high degree of spatial heterogeneity and evidence for massive breccia blocks 4 olivine strongly concentrated on the rim wall and exterior of the southeastern quadrant of the crater is commonly associated the impact melt 5 there are at least two types of glass deposits observed pyroclastic glass and impact glass

characterization of the 1 2 μm m1 pyroxene band extracting cooling history from near ir spectra of pyroxenes and pyroxene dominated rocks the 1 2 m band in near infrared spectra of pyroxenes results from fe2 in the m1 crystallographic site the distribution of fe and mg between the m1 and m2 sites is in part a function of the cooling rate and thermal history of a pyroxene combining near infrared and mssbauer spectra for a series of compositionally controlled synthetic mg fe ca pyroxenes we quantify the strength of the 1 2 m band as a function of fe2 in the m1 site near infrared spectra are deconvolved into component absorptions that can be assigned to the m1 and m2 sites using the modified gaussian model the relative strength of the 1 2 m band is shown to be directly related to the amount of fe2 in the m1 site measured by mossbauer spectroscopy the strength of the 1 2 m band relative to the combined strengths of the 1 2 and 2 m bands or the m1 intensity ratio is calculated for 51 howardite eucrite and diogenite hed meteorites diogenites and cumulate eucrites exhibit the lowest m1 intensity ratios consistent with their formation as slowly cooled cumulates basaltic eucrites exhibit a large range of m1 intensity ratios all of which are consistently higher than the diogenites and cumulate eucrites this example illustrates how the m1 intensity ratio can be a used as a tool for characterizing the cooling history of remotely detected pyroxene dominated rocks

spectroscopic characterization of mineralogy and its diversity across vesta the mineralogy of vesta based on data obtained by the dawn spacecraft s visible and infrared spectrometer is consistent with howardite eucrite diogenite meteorites there are considerable regional and local variations across the asteroid spectrally distinct regions include the south polar rheasilvia basin which displays a higher diogenitic component and equatorial regions which show a higher eucritic component the lithologic distribution indicates a deeper diogenitic crust exposed after excavation by the impact that formed rheasilvia and an upper eucritic crust evidence for mineralogical stratigraphic layering is observed on crater walls and in ejecta this is broadly consistent with magma ocean models but spectral variability highlights local variations which suggests that the crust can be a complex assemblage of eucritic basalts and pyroxene cumulates overall vesta mineralogy indicates a complex magmatic evolution that led to a differentiated crust and mantle

olivine in an unexpected location on vesta s surface although olivine was expected to occur within the deep south pole basins of asteroid vesta which are thought to be excavated mantle rocks spectral data from nasa s dawn spacecraft show that it instead occurs as near surface materials in vesta s northern hemisphere between july 2011 and september 2012 nasa s dawn spacecraft was in orbit around the asteroid vesta in this paper dawn s visible and infrared mapping spectrometer vir team presents a surprising finding the signature of olivine on the asteroid s surface olivine is a major component of the mantle of differentiated bodies including earth vesta is a large asteroid large enough to have differentiated into an earth like layered structure and the expectation was that olivine would be found within vesta s deep south pole basins thought to be excavated mantle rocks yet the spectroscopic data reveal olivine rich material close to the surface in the northern hemisphere an understanding of the differentiation processes that have occurred on vesta will be invaluable as a window on the primordial solar system but these latest findings show that vesta s evolutionary history is more complicated than was thought olivine is a major component of the mantle of differentiated bodies including earth howardite eucrite and diogenite hed meteorites represent regolith basaltic crust lower crust and possibly ultramafic mantle samples of asteroid vesta which is the lone surviving large differentiated basaltic rocky protoplanet in the solar system1 only a few of these meteorites the orthopyroxene rich diogenites contain olivine typically with a concentration of less than 25 per cent by volume2 olivine was tentatively identified on vesta3 4 on the basis of spectral and colour data but other observations did not confirm its presence5 here we report that olivine is indeed present locally on vesta s surface but that unexpectedly it has not been found within the deep south pole basins which are thought to be excavated mantle rocks6 7 8 instead it occurs as near surface materials in the northern hemisphere unlike the meteorites the olivine rich more than 50 per cent by volume material is not associated with diogenite but seems to be mixed with howardite the most common7 9 surface material olivine is exposed in crater walls and in ejecta scattered diffusely over a broad area the size of the olivine exposures and the absence of associated diogenite favour a mantle source but the exposures are located far from the deep impact basins the amount and distribution of observed olivine rich material suggest a complex evolutionary history for vesta

olivine or impact melt nature of the orange material on vesta from dawn abstract nasa s dawn mission observed a great variety of colored terrains on asteroid 4 vesta during its survey with the framing camera fc here we present a detailed study of the orange material on vesta which was first observed in color ratio images obtained by the fc and presents a red spectral slope the orange material deposits can be classified into three types a diffuse ejecta deposited by recent medium size impact craters such as oppia b lobate patches with well defined edges nicknamed pumpkin patches and c ejecta rays from fresh looking impact craters the location of the orange diffuse ejecta from oppia corresponds to the olivine spot nicknamed leslie feature first identified by gaffey gaffey m j 1997 icarus 127 130 157 from ground based spectral observations the distribution of the orange material in the fc mosaic is concentrated on the equatorial region and almost exclusively outside the rheasilvia basin our in depth analysis of the composition of this material uses complementary observations from fc the visible and infrared spectrometer vir and the gamma ray and neutron detector grand several possible options for the composition of the orange material are investigated including cumulate eucrite layer exposed during impact metal delivered by impactor olivine orthopyroxene mixture and impact melt based on our analysis the orange material on vesta is unlikely to be metal or olivine originally proposed by gaffey gaffey m j 1997 icarus 127 130 157 analysis of the elemental composition of oppia ejecta blanket with grand suggests that its orange material has 25 cumulate eucrite component in a howarditic mixture whereas two other craters with orange material in their ejecta octavia and arruntia show no sign of cumulate eucrites morphology and topography of the orange material in oppia and octavia ejecta and orange patches suggests an impact melt origin a majority of the orange patches appear to be related to the formation of the rheasilvia basin combining the interpretations from the topography geomorphology color and spectral parameters and elemental abundances the most probable analog for the orange material on vesta is impact melt

elemental mapping by dawn reveals exogenic h in vesta s regolith using dawn s gamma ray and neutron detector we tested models of vesta s evolution based on studies of howardite eucrite and diogenite hed meteorites global fe o and fe si ratios are consistent with hed compositions neutron measurements confirm that a thick diogenitic lower crust is exposed in the rheasilvia basin which is consistent with global magmatic differentiation vesta s regolith contains substantial amounts of hydrogen the highest hydrogen concentrations coincide with older low albedo regions near the equator where water ice is unstable the young rheasilvia basin contains the lowest concentrations these observations are consistent with gradual accumulation of hydrogen by infall of carbonaceous chondrites observed as clasts in some howardites and subsequent removal or burial of this material by large impacts

possible mantle origin of olivine around lunar impact basins detected by selene the composition structure and evolution of the moon s mantle is poorly constrained a global survey of the moon s surface using the spectral profiler onboard the lunar explorer selene kaguya identifies a number of exposures of olivine in concentric regions around lunar craters with a possible mantle origin

petrology and geochemistry of the elephant moraine a79002 diogenite a genomict breccia containing a magnesian harzburgite component the elephant moraine a79002 eeta79002 diogenite is a fragmental breccia with a subtle lightdark structure it is composed of orthopyroxene with minor olivine chromite and ubiquitous inhomogeneously distributed approximately 5 500 m sized troilite and metal grains these latter are present in the matrix and as inclusions in and as symplectic intergrowths with orthopyroxene and olivine trace amounts of silica and diopside are also present most orthopyroxene compositions typical orthopyroxenes are in the narrow range wo2 1 2 7en74 1 75 6fs22 2 23 8 like those of most diogenites a few magnesian orthopyroxenes are present with compositions of wo1 7 2 5en77 5 80 2 fs18 2 20 3 these are among the most magnesian orthopyroxenes known from diogenites a few ferroan orthopyroxenes have compositions of wo2 1 2 9en71 7 73 7fs24 2 25 5 differences in al2o3 tio2 and cr2o3 between the different orthopyroxene groups are inconsistent with a simple igneous fractionation relationship between them olivine compositions are fo75 0 76 9 the olivines could be in equilibrium with the magnesian orthopyroxenes but not with the typical or ferroan orthopyroxenes that form the bulk of eeta79002 metal grains exhibit a range of ni and co contents and ni co ratios their compositions indicate that they are primary igneous metal metal and troilite grains are more prevalent in the dark samples the trace incompatible lithophile element contents of 16 samples are remarkably uniform their yb concentrations are all within their 2s analytical uncertainties of the mean the uniformity and low content of light rare earth elements in eeta79002 indicate that negligible amounts of a trapped liquid component or foreign material mixed in the breccia could be present the siderophile and chalcophile element data show that the light dark structure is due to the distribution of metal and troilite grains dark samples contain higher ni co and se compared to light samples meteorite eeta79002 appears to contain material from three or more related plutons a magnesian harzburgite and two orthopyroxenites and is a genomict breccia

a systematic mapping procedure based on the modified gaussian model to characterize magmatic units from olivine pyroxenes mixtures application to the syrtis major volcanic shield on mars clenet et al 2011 have developed an adapted version of the modified gaussian model mgm the improvements allow the characterization of spectra of olivine pyroxene s mixtures addressing both modal composition and individual minerals chemical composition this version of mgm is fully automated and operational with large amounts of hyperspectral imaging data two natural cases are considered the first one is the sumail massif in the oman ophiolite earth based on our approach applied to hymap data two contrasted lithologic units are mapped the mantle which is harzburgite dominated and the crust made of gabbros and clinopyroxene rich cumulates with spectral variations interpreted in terms of pyroxenes chemical compositions once this new mgm mapping approach has been validated on a controlled natural situation we map the distribution of mafic assemblages across the syrtis major volcano on mars using a visible and near infrared vnir short wave infrared swir observatoire pour la mineralogie l eau les glaces et l activite omega mars express mex mosaic our results are in agreement with previous work but olivine appears to be more abundant than previously estimated in the central part of the volcanic edifice especially in ternary mafic assemblages augite olivine enstatite based on these results we propose a possible scenario for the igneous and thus thermal evolution of the syrtis major region surrounding terrains have formed first and local heterogeneity can be observed between northern and southern areas of the noachian crust we also observe variations in the mineral assemblages within syrtis major lavas which can be interpreted in terms of differentiation from a common parent melt and or of a progressive evolution of the mantle source composition and temperature key points mgm systematic mapping on syrtis major to characterize mafic minerals mixtures olivine and pyroxenes mixture is detected in the central lavas of the volcano pyroxenes have chemical compositions spanning the enstatite augite range

detections and geologic context of local enrichments in olivine on vesta with vir dawn data the magmatism characterizing the early history of the asteroid vesta has long been investigated with the mafic and ultramafic meteorites howardite eucrite and diogenite hed the lack of geologic context for the meteorites however has limited its understanding here we use the visible to near ir vir orbital observations of vesta s surface to detect relative enrichments in olivine and to study the associated geologic features because the near ir signature of olivine on vesta s surface is subtle relative to the widespread pyroxene absorption bands a method was developed to distinguish olivine enrichments from admixture of pyroxenes with high fe2 m1 dark material and potential fe bearing glass relative enrichment of olivine 50 60 vol is found in 2 5 km wide morphologically fresh areas our global survey reveals a dozen of these areas clustering in the eastern hemisphere of vesta the hemispherical coincidence with a widespread low enrichment in diogenite like pyroxene suggests the presence of a distinct compositional terrain on the central mound of the rheasilvia impact basin no olivine enrichment was found suggesting the absence of an olivine dominated mantle above the basin s excavation depth or alternatively a low amount of olivine homogeneously mixed with diogenite like pyroxenes rare olivine enriched areas in close proximity to diogenite like pyroxene are found as part of material ejected by the rheasilvia impact such cooccurrence is reminiscent of local ultramafic lithologies within the crust the possible formation of such lithologies on vesta is supported by some hed meteorites dominated by olivine and orthopyroxene

vesta as the howardite eucrite and diogenite parent body implications for the size of a core and for large scale differentiation if vesta is the parent body of the howardite eucrite and diogenite hed meteorites then geo chemical and petrologic constraints for the meteorites may be used in conjunction with astronomical constraints for the size and mass of vesta to 1 determine the size of a possible metal core in vesta and 2 model the igneous differentiation and internal structure of vesta the density of vesta and petrologic models for hed meteorites together suggest that the amount of metal in the parent body is 25 mass with a best estimate of 5 assuming no porosity for a porosity of up to 5 in the silicate fraction of the asteroid the permissible metal content is 30 these results suggest that any metal core in the hed parent body and vesta is not unusually large a variety of geochemical and other data for hed meteorites are consistent with the idea that they originated in a magma ocean it appears that diogenites formed by crystal accumulation in a magma ocean cumulate pile and that most noncumulate eucrites excepting such eucrites as bouvante and statinem formed by subsequent crystallization of the residual melts modelling results suggest that the hed parent body is enriched in rare earth elements by a factor of 2 5 3 5 relative to ci chondrites and that it has approximately chondritic mg si and al sc ratios stokes settling calculations for a vesta wide nonturbulent magma ocean suggest that early crystallizing magnesian olivine orthopyroxene and pigeonite would have settled relatively quickly permitting fractional crystallization to occur but that later crystallizing phases would have settled or floated an order of magnitude more slowly allowing instead a closer approach to equilibrium crystallization for the more evolved eucritic melts this would have inhibited the formation of a plagioclase flotation crust on vesta plausible models for the interior of vesta which are consistent with the data for hed meteorites and vesta include a metal core 130 km radius an olivine rich mantle 65 220 km thick a lower crustal unit 12 43 km thick composed of pyroxenite from which diogenites were derived and an upper crustal unit 23 42 km thick from which eucrites originated the present shape of vesta with 60 km difference in the maximum and minimum radius suggests that all of the crustal materials and possibly some of the underlying olivine from the mantle could have been locally excavated or exposed by impact cratering

a spectrum of alluvial deposits in the lower carboniferous bonaventure formation of western chaleur bay area gaspe and new brunswick canada the lower carboniferous bonaventure formation of western chaleur bay gaspe and new brunswick is a terrestrial redbed succession with abundant calcretes deposited in a semi arid paleoclimate facies can be grouped into three associations conglomeratic sandstone and mud dominated within two 100 150 m upward fining megasequences the megasequences are attributed to alluvial fan progradation due to tectonic rejuvenation vertical facies relationships and internal structures indicate that varied alluvial environments are represented alluvial fans formed on steep slopes adjacent to fault scarps and are dominated by deposits of the conglomeratic association lateral and downslope coalescence of fans into a braid plain is represented by transition from the conglomeratic to the sandstone facies association distally the braid plain is transitional into deposits of the mud dominated association paleocurrents and clast compositions show that sediment in the gaspe outcrops was derived from the northwest and

origin of olivine at copernicus the central peaks of copernicus are among the few lunar areas where near infrared telescopic reflectance spectra indicate extensive exposures of olivine other parts of copernicus crater and ejecta which were derived from highland units in the upper parts of the target site contain only low ca pyroxene as a mafic mineral the exposure of compositionally distinct layers including the presence of extensive olivine may result from penetration to an anomalously deep layer of the crust or to the lunar mantle we suggest that the procellarum basin and the younger superposed insularum basin have provided access to these normally deep seated crustal or mantle materials by thinning the upper crustal material early in lunar history the occurrences of olivine in portions of the compositionally heterogeneous aristarchus region in a related geologic setting may be due to the same sequence of early events

geologic map of the northern hemisphere of vesta based on dawn framing camera fc images abstract the dawn framing camera fc has imaged the northern hemisphere of the asteroid 4 vesta at high spatial resolution and coverage this study represents the first investigation of the overall geology of the northern hemisphere 22 90 n quadrangles av 1 2 3 4 and 5 using these unique dawn mission observations we have compiled a morphologic map and performed crater size frequency distribution csfd measurements to date the geologic units the hemisphere is characterized by a heavily cratered surface with a few highly subdued basins up to 200 km in diameter the most widespread unit is a plateau cratered highland unit similar to although of lower elevation than the equatorial vestalia terra plateau large scale troughs and ridges have regionally affected the surface between 180 e and 270 e these tectonic features are well developed and related to the south pole veneneia impact saturnalia fossae trough unit elsewhere on the hemisphere they are rare and subdued saturnalia fossae cratered unit in these pre rheasilvia units we observed an unexpectedly high frequency of impact craters up to 10 km in diameter whose formation could in part be related to the rheasilvia basin forming event the rheasilvia impact has potentially affected the northern hemisphere also with s n small scale lineations but without covering it with an ejecta blanket post rheasilvia impact craters are small

a deep crust mantle boundary in the asteroid 4 vesta the asteroid 4 vesta was recently found to have two large impact craters near its south pole exposing subsurface material modelling suggested that surface material in the northern hemisphere of vesta came from a depth of about 20 kilometres whereas the exposed southern material comes from a depth of 60 to 100 kilometres large amounts of olivine from the mantle were not seen suggesting that the outer 100 kilometres or so is mainly igneous crust here we analyse the data on vesta and conclude that the crust mantle boundary or moho is deeper than 80 kilometres

vestan lithologies mapped by the visual and infrared spectrometer on dawn we present global lithological maps of the vestan surface based on dawn mission s visible infrared vir spectrometer acquisitions with a spatial sampling of 200 m the maps confirm the results obtained with the data set acquired by vir with a spatial sampling of 700 m that the reflectance spectra of vesta s surface are dominated by pyroxene absorptions that can be interpreted within the context of the distribution of howardites eucrites and diogenites heds the maps also partially agree with the ground and hubble space telescope observations they confirm the background surface being an assemblage of howardite or polymict eucrite as well as the location of a diogenitic rich spot however there is no evidence of extended olivine rich regions in the equatorial latitudes diogenite is revealed on the rheasilvia basin floor indicating that material of the lower crust mantle was exposed vir also detected diogenites along the scarp of matronalia rupes and the rims of severina and a nearby unnamed crater and as ejecta of antonia crater the diogenite distribution is fully consistent with petrological constraints although the mapped distribution does not provide unambiguous constraints it favors the hypothesis of a magma ocean

the distribution of olivine in the crater aristarchus inferred from clementine nir data clementine imaged the moon entirely at eleven wavelengths this paper presents new results obtained on the crater aristarchus using a heuristic method for the calibration of the near infrared nir data set we computed band ratios and we extracted spectra using a telescopic spectrum as reference a new 4 10 km olivine rich area has been identified on the southeastern rim of the crater in addition to a smaller olivine rich area previously reported the olivine to pyroxene ratio exceeds 6 in this new zone this demonstrates the uniqueness of the clementine nir data set in discriminating olivine from pyroxene on the lunar surface with implications for magmatic processes in the lunar mantle and crust

challenges in detecting olivine on the surface of 4 vesta identifying and mapping olivine on asteroid 4 vesta are important components to understanding differentiation on that body which is one of the objectives of the dawn mission harzburgitic diogenites are the main olivine bearing lithology in the howardite eucrite diogenite hed meteorites a group of samples thought to originate from vesta here we examine all the antarctic harzburgites and estimate that on scales resolvable by dawn olivine abundances in putative harzburgite exposures on the surface of vesta are likely at best in the 10 30 range but probably lower due to impact mixing we examine the visible near infrared spectra of two harzburgitic diogenites representative of the 10 30 olivine range and demonstrate that they are spectrally indistinguishable from orthopyroxenitic diogenites the dominant diogenitic lithology in the hed group this suggests that the visible near infrared spectrometer onboard dawn vir will be unable to resolve harzburgites from orthopyroxenites on the surface of vesta which may explain the current lack of identification of harzburgitic diogenite on vesta

mass wasting features and processes in vesta s south polar basin rheasilvia 1 the rheasilvia crater is vesta s largest impact basin it is a 500 km diameter complex crater centered near the south pole and overlying the 400 km diameter impact basin veneneia using framing camera fc data from the dawn spacecraft s low altitude mapping orbit 20 m pixel and a digital terrain model derived from high altitude mapping orbit stereo data we identified various mass wasting features within the south polar region these features include intra crater mass movements flow like and creep like structures slumping areas landslides and curved radial and concentric ridges intra crater mass wasting features are represented by lobate slides talus material dark patches on the crater wall spurs along the crater rim and boulders slumping areas develop in compact material whereas landslides form in relatively loose material both may be triggered by seismic shaking induced by impacts intra crater mass wasting and slid and slumped materials are homogeneously distributed throughout the basin slumping and sliding processes have contributed most efficiently to basin degradation flow like and creep like features originate from granular material and cluster between 0 e and 90 e an area exposing shocked and fractured material from the rheasilvia impact event the radial curved ridges are likely to be remnants of the early rheasilvia collapse process when radially moving masses were deflected by the coriolis effect the concentric ridges are artifacts from the crater rim collapse curved ridges at the intersection of rheasilvia and veneneia and on rheasilvia s central peak may also have been influenced by the rheasilvia basin relaxation process and an oblique impact respectively

two dimensional numerical modeling of the rheasilvia impact formation 1 we numerically modeled the formation of rheasilvia crater an enormous impact basin centered on asteroid 4 vesta s south pole using a trial and error method our models were adjusted to produce the best possible fit to rheasilvia s size and shape as observed during the vesta orbital stage of the dawn mission the final model yields estimates of the shock wave decay escaped material volume depth of excavation and other relevant characteristics to the extent allowed by the two dimensional axially symmetric approximation of the simplified arbitrary lagrangian eulerian hydrocode our model results permit interpretation of the dawn data on vesta s shape topographic crater profiles and the origin of the vestoid asteroid family as escaped ejecta from the rheasilvia crater

near infrared spectral reflectance of mineral mixtures systematic combinations of pyroxenes olivine and iron oxides near infrared spectral reflectance data are presented for systematic variations in weight percent of two component mixtures of ferromagnesian and iron oxide minerals mixtures were chosen for application to the study of the dark materials on mars but the results are equally applicable to mafic and ultramafic assemblages elsewhere in the solar system olivine spectral features are greatly reduced in contrast by admixture of other phases but remain distinctive even for low olivine contents clinopyroxene and orthopyroxene mixtures show resolved pyroxene absorptions near 2 m the addition of limonite greatly modifies pyroxene and olivine reflectance but does not fully eliminate distinctive spectral characteristics using only spectral data in the 1 m region it is difficult to differentiate orthopyroxene and limonite goethite in a mixture additional spectral coverage or other evidence may be required for a unique interpretation all composite mineral absorptions observed in this study are either weaker than or intermediate in strength to the end member absorptions and have bandwidths greater than or equal to those for the end members in general spectral properties in an intimate mixture combine in a complex nonadditive manner with features demonstrating a regular but usually nonlinear variation as a function of end member phase proportions

composition and mineralogy of dark material units on vesta vesta is the asteroid with the largest albedo variation among the known rocky solar system objects and shows a widespread occurrence of dark material dm and bright material bm units in the first observation phases by the dawn spacecraft two main extensions of low albedo areas were identified on vesta and found to be closely correlated with carbonaceous oh rich material in this work we use the hyperspectral data provided by the vir dawn imaging spectrometer onboard dawn to detect and analyze individual well defined dark material units we define dm units assuming a relative criterion i e reflectance lower than the surroundings by coupling visible and infrared images of the same area we are able to select real dark material units discarding false detections created by shadowing effects a detailed final catalogue of 123 dark units is presented containing the geographical parameters and the main spectral characteristics for each unit independently of the geological context of the dark units all dms show similar spectral properties dominated by the pyroxene absorption features as is the average spectrum of vesta this finding suggests a similar composition with the presence of darkening agents that also weaken pyroxene band depths the majority 90 of the dm units shows a positive correlation between low albedo and an oh band centered at 2 8 lm confirming the hypothesis that the darkening agents are carbonaceous chondrites probably delivered by low velocity impacts of primitive asteroids a comparison with laboratory spectra allows us to better constrain the size and the composition of the darkening agents these dm areas seem to be made of eucritic material the regolith grain size seems to be nearly constant around an average value of 25 lm and is quite homogenous at least in the first hundreds of meters beneath the vesta surface suggesting similar processing mechanisms for both dm and bm

a magma ocean on vesta core formation and petrogenesis of eucrites and diogenites abstract available evidence strongly suggests that the hed howardite eucrite diogenite meteorites are samples of asteroid 4 vesta abundances of the moderately siderophile elements ni co mo w and p in the hed mantle indicate that the parent body may have been completely molten during its early history during cooling of a chondritic composition magma ocean equilibrium crystallization is fostered by the suspension of crystals in a convecting magma ocean until the crystal fraction reaches a critical value near 0 80 when the convective system freezes and melts segregate from crystals by gravitational forces the extruded liquids are similar in composition to main group and stannern trend eucrites and the last pyroxenes to precipitate out of this ocean before convective lockup span the compositional range of the diogenites subsequent fractional crystallization of a main group eucrite liquid which has been isolated as a body of magma produces the nuevo laredo trend and the cumulate eucrites the predicted cumulate mineral compositions are in close agreement with phase compositions analyzed in the cumulate eucrites thus eucrites and diogenites are shown to have formed as part of a simple and continuous crystallization sequence starting with a magma ocean environment on an asteroidal size parent body that is consistent with vesta

the origin of eucrites diogenites and olivine diogenites magma ocean crystallization and shallow magma chamber processes on vesta the asteroid 4 vesta is one of the very few heavenly bodies to have been linked to samples on earth the howardite eucrite diogenite hed meteorite suite this large and diverse suite of meteorites provides a detailed picture of vesta s igneous and postigneous history we have used the range of igneous rock types and compositions in the hed suite to test a series of chemical models for solidification processes following peak melting magma ocean conditions on vesta fractional crystallization cannot have been a dominant early process in the magma ocean because it leads to excessive fe enrichment in the melt models that are dominated by equilibrium crystallization cannot produce orthopyroxene cumulates diogenites our best models invoke 60 70 equilibrium crystallization of a magma ocean followed by continuous extraction of the residual melt into shallow magma chambers fractional crystallization in these magma chambers combined with continuous or periodic addition of more melt from the slowly compacting crystal mush magmatic recharge can produce all of the igneous hed lithologies noncumulate and cumulate eucrites diogenites dunites harzburgites and olivine diogenites magmatic recharge can also explain the narrow range in eucrite compositions and the variability of incompatible trace element concentrations in diogenites we predict an internal structure for vesta that permits excavation of the heds during the formation of the rheasilvia basin while remaining consistent with observations from the dawn mission and most impact models

martian surface mineralogy from observatoire pour la mineralogie l eau les glaces et l activite on board the mars express spacecraft omega mex global mineral maps 1 after 2 years of operation the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer on board mars express has acquired data coverage of the martian surface with spatial resolution varying between 300 m and 4 8 km depending on the pericenter altitude of the spacecraft s elliptical orbit we report the global surface distributions of some minerals using the omega observations in the visible and near infrared vnir wavelength domains 0 35 2 5 m global maps of ferric phases mafic minerals pyroxenes and olivines and hydrated minerals have been derived from spectral parameters the limits of detection in terms of abundance for some minerals of different grain size distributions are given the distribution of pyroxenes is in general agreement with the mineral maps of previous telescopic and space observations the fe3 absorption feature in the visible wavelength region is present everywhere on the surface the spectra of the bright regions compare with anhydrous nanophase ferric oxides terrains with water bearing minerals cover a very small fraction of the martian surface olivine mg rich compositions is detected in more extensive regions of the pyroxene rich zones than previously reported olivine with higher iron content and or larger grain size 100 m is only detected in isolated areas the mineralogy of the northern low albedo regions is discussed in the light of these mineral maps chemical alteration or oxidation during extrusion producing a coating or varnish of anhydrous ferric phases over a dark basaltic surface best accounts for the vnir spectral properties of these regions although a glassy composition resulting from impact is also considered

spectral characteristics of lunar impact melts and inferred mineralogy abstract two suites of lunar impact melt samples have been measured in nasa s reflectance experiment laboratory relab at brown university suite 1 comprises seven apollo 17 crystalline impact melt breccias and seven quenched glass equivalents suite 2 is made up of 15 additional impact melt samples from apollo 12 15 16 and 17 which exhibit a range of textures and compositions related to cooling conditions and glass abundance a few of these samples have cooled slowly and fully crystallized and thus have the same spectral properties as igneous rocks of similar texture and composition they cannot be uniquely distinguished without geologic context however most of the impact melts and melt breccias contain either quantities of quenched glass and or have developed microcrystalline nonequilibrium textures with well defined diagnostic spectral properties the microcrystalline textures are associated with a distinctive 600 nm absorption feature apparently due to submicroscopic ilmenite inclusions in a transparent host typically fine grained plagioclase the reflectance properties of these lunar sample suites contribute to and constrain the identification and characterization of impact melts in remote sensing data

vesta s mineralogical composition as revealed by the visible and infrared spectrometer on dawn the dawn spacecraft mission has provided extensive new and detailed data on vesta that confirm and strengthen the vesta howardite eucrite diogenite hed meteorite link and the concept that vesta is differentiated as derived from earlier telescopic observations here we present results derived by newly calibrated spectra of vesta the comparison between data from the dawn imaging spectrometer vir and the different class of hed meteorites shows that average spectrum of vesta resembles howardite spectra nevertheless the vesta spectra at high spatial resolution reveal variations in the distribution of hed like mineralogies on the asteroid the data have been used to derive hed distribution on vesta reported in ammannito et al 2013 and to compute the average vestan spectra of the different hed lithologies reported here the spectra indicate that not only are all the different hed lithologies present on vesta but also carbonaceous chondritic material which constitutes the most abundant inclusion type found in howardites is widespread however the hydration feature used to identify carbonaceous chondrite material varies significantly on vesta revealing different band shapes the characteristic of these hydration features cannot be explained solely by infalling of carbonaceous chondrite meteorites and other possible origins must be considered the relative proportion of heds on vesta s surface is computed and results show that most of the vestan surface is compatible with eucrite rich howardites and or cumulate or polymict eucrites a very small percentage of surface is covered by diogenite and basaltic eucrite terrains are relatively few compared with the abundance of basaltic eucrites in the hed suite the largest abundance of diogenitic material is found in the rheasilvia region a deep basin where it clearly occurs below a basaltic upper crust however diogenite is also found elsewhere although the depth to diogenite is consistent with one magma ocean model its lateral extent is not well constrained

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

diogenites as polymict breccias composed of orthopyroxenite and harzburgite abstract a few relatively unbrecciated olivine rich diogenites consist of an equilibrium assemblage of olivine and magnesian orthopyroxene harzburgite more common diogenites with smaller amounts of olivine are breccias containing two distinct orthopyroxenes one magnesian and one ferroan these diogenites are mixtures of a harzburgite lithology that is more magnesian with the normal orthopyroxenite lithology that is ferroan and may contain small amounts of plagioclase both lithologies likely formed by fractional crystallization in multiple plutons emplaced within the crust of asteroid 4 vesta minor element trends in orthopyroxenes indicate that these plutons exhibited a range of compositions we propose a revised taxonomy for the hed howardites eucrites and diogenites suite where all ultramafic samples are referred to as diogenites within this group the prefixes dunitic harzburgitic and orthopyroxenitic are used to distinguish diogenites consisting of more than or equal to 90 olivine olivine orthopyroxene and more than or equal to 90 orthopyroxene respectively the prefix polymict is used to describe brecciated mixtures of any of these rock types the recognition that olivine is a significant phase in some diogenites is consistent with spectral interpretations of olivine in a deeply excavated crater on vesta and has important implications for the bulk composition and petrogenesis of that body

magnesium oxide iron oxide mass balance constraints and a more detailed model for the relationship between eucrites and diogenites according to a currently popular model for petrogenesis on the howardite eucrite and diogenite hed parent asteroid the diogenites are not comagmatic with most eucrites but instead formed in separate orthopyroxenite dominated plutons this model can be tested for consistency with mass balance for mgo and feo assuming the overall diogenite diogenite eucrite ratio d of the parent asteroid is at least comparable to the average d for the eucrite diogenite dominated howardite regolith breccias average mg mgo mgo feo is much lower for eucrites especially noncumulate eucrites than for diogenites unless the diogenite parent magmas eventually produced a large proportion of low mg residual basalt and gabbro rbg the implied initial magma s mg is vastly higher than that of any noncumulate eucrite starting from a source previously depleted by putative primary eucrite genesis melt mg can be estimated as a function of the exchange reaction kd and degree of melting using several very conservative assumptions e g assuming that the total mgo feo concentration is nearly the same in the nascent melt as in the residual solids the degree of melting required to yield a melt with mg high enough to satisfy mass balance without implying an rbg component that accounts for 50 of all eucrites is an implausibly high 60 80 wt the separate orthopyroxenitic plutons sop model also seems inconsistent with the uniform density of melts across the diogenite eucrite compositional spectrum 2 77 2 82 g cm3 which implies that diogenitic magmas should have been as capable as eucrites of extruding to form lavas this difficulty cannot be reduced by simply assuming that later formed magmas were systematically both more plutonic and more mgo rich than earlier ones because the plutonic cumulate eucrites equilibrated with melts systematically lower in mg than noncumulate eucrites conceivably the bulk mg of the asteroid s silicate system was increased between primary melt eucrite genesis and sop diogenite genesis by graphite fueled reduction of feo however the graphite oxidation process generates a huge proportion of gas which would have enhanced the buoyancy of the nascent diogenite parent magmas thus exacerbating the difficulty of achieving the implied high degrees of partial melting to avoid these difficulties but still form most eucrites as rapidly cooled extrusives i propose the nerd noncumulate eucrites as extruded residua of diogenites model in this model the diogenites form as early cumulates from a large magma system probably a global magma ocean that yields a large proportion of eucritic melt as residuum this residual melt zone undergoes relatively little crystallization during a period when it is episodically tapped to produce extrusions dikes and sills of rapidly cooled noncumulate eucrites slight 5 10 porosity in the nascent eucritic crust keeps it marginally buoyant over the residual melt zone the common thermal metamorphism of noncumulate eucrites results from baking by superjacent flows during the episodic venting of the melt zone the nerd model s greatest advantage is that it does not require implausibly high degrees of localized melting in the mature stages of igneous evolution of the hed asteroid

relative chronology of crust formation on asteroid vesta insights from the geochemistry of diogenites abstract the eucrites and diogenites are meteorites that probably originate from asteroid 4 vesta the upper part of the crust of this body is certainly composed of eucrites which are basaltic or gabbroic rocks diogenites are ultramafic cumulates whose relationships with eucritic lithologies are unknown here we show that the orthopyroxenes of some diogenites display very deep negative eu anomalies eu eu close to 0 1 or lower the contamination of the parental magmas of diogenites by melts derived by partial melting of the eucritic crust can satisfactorily explain the range of the eu anomalies displayed by diogenites thus these anomalies are the first firm indication that parental melts of diogenites have intruded the eucritic crust and consequently are younger than eucrites

distinctive space weathering on vesta from regolith mixing processes whereas space weathering of some airless bodies such as the moon occurs through the accumulation on regolith of nanophase metallic particles spectroscopic data show that space weathering of the asteroid vesta occurs through the small scale mixing of diverse surface components which gradually generates locally homogenized upper regolith between 16 july 2011 and 5 september 2012 nasa s space probe dawn was orbiting vesta a protoplanet thought to have survived virtually intact since an early phase of solar system formation in this issue of nature two groups report on the encounter carle pieters and co workers find that space weathering on vesta has followed a different course from that observed on the moon and on itokawa the asteroid sampled in an earth return mission on vesta weathering involved fine scale regolith soil mixing that has removed clear traces of recent impact deposits there are no signs of the nanophase metallic particle deposits seen on the moon and itokawa thomas mccord and co authors describe two main types of material on vesta s surface bright and dark the bright material may be uncontaminated indigenous vesta basaltic soil with the darker material derived from low albedo impactors dawn has now moved on and is due to rendezvous with the protoplanet ceres in february 2015 the surface of the asteroid vesta has prominent near infrared absorption bands characteristic of a range of pyroxenes confirming a direct link to the basaltic howardite eucrite diogenite class of meteorites1 2 3 processes active in the space environment produce space weathering products that substantially weaken or mask such diagnostic absorption on airless bodies observed elsewhere4 5 and it has long been a mystery why vesta s absorption bands are so strong analyses of soil samples from both the moon6 and the asteroid itokawa7 determined that nanophase metallic particles commonly nanophase iron accumulate on the rims of regolith grains with time accounting for an observed optical degradation these nanophase particles believed to be related to solar wind and micrometeoroid bombardment processes leave unique spectroscopic signatures that can be measured remotely8 9 10 but require sufficient spatial resolution to discern the geologic context and history of the surface which has not been achieved for vesta until now here we report that vesta shows its own form of space weathering which is quite different from that of other airless bodies visited no evidence is detected on vesta for accumulation of lunar like nanophase iron on regolith particles even though distinct material exposed at several fresh craters becomes gradually masked and fades into the background as the craters age instead spectroscopic data reveal that on vesta a locally homogenized upper regolith is generated with time through small scale mixing of diverse surface components

large scale troughs on vesta a signature of planetary tectonics abstract images of vesta taken by the dawn spacecraft reveal large scale linear structural features on the surface of the asteroid we evaluate the morphology of the vesta structures to determine what processes caused them to form and what implications this has for the history of vesta as a planetary body the dimensions and shape of these features suggest that they are graben similar to those observed on terrestrial planets not fractures or grooves such as are found on smaller asteroids as graben their vertical displacement versus length relationship could be evaluated to describe and interpret the evolution of the component faults linear structures are commonly observed on smaller asteroids and their formation has been tied to impact events while the orientation of the large scale vesta structures does imply that their formation is related to the impact events that formed the rheasilvia and veneneia basins their size and morphology is greatly different from impact formed fractures on the smaller bodies this is consistent with new analyses that suggest that vesta is fully differentiated with a mantle and core we suggest that impact into a differentiated asteroid such as vesta could result in graben while grooves and fractures would form on undifferentiated asteroids

composition of the rheasilvia basin a window into vesta s interior 1 the estimated excavation depth of the huge rheasilvia impact basin is nearly twice the likely thickness of the vestan basaltic crust so the mantle should be exposed spectral mapping by the dawn spacecraft reveals orthopyroxene rich materials similar to diogenite meteorites in the deepest parts of the basin and within its walls significant amounts of olivine are predicted for the mantles of bulk chondritic bodies like vesta and its occurrence is demonstrated by some diogenites that are harzburgite and dunite however olivine has so far escaped detection by dawn s instruments spectral detection of olivine in the presence of orthopyroxene is difficult in samples with 25 olivine and olivine in rheasilvia might have been diluted during impact mixing or covered by the collapse of basin walls the distribution of diogenite inferred from its exposures in and around rheasilvia provides a geologic context for the formation of these meteorites but does not clearly distinguish between a magmatic cumulate versus partial melting restite origin for diogenites the former is favored by geochemical arguments and crystallization in either a magma ocean or multiple plutons emplaced near the crust mantle boundary is permitted by dawn observations

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

color and albedo heterogeneity of vesta from dawn multispectral images 0 44 to 0 98 m of asteroid 4 vesta obtained by the dawn framing cameras reveal global color variations that uncover and help understand the north south hemispherical dichotomy the signature of deep lithologies excavated during the formation of the rheasilvia basin on the south pole has been preserved on the surface color variations band depth spectral slope and eucrite diogenite abundance clearly correlate with distinct compositional units vesta displays the greatest variation of geometric albedo 0 10 to 0 67 of any asteroid yet observed four distinct color units are recognized that chronicle processes including impact excavation mass wasting and space weathering that shaped the asteroid s surface vesta s color and photometric diversity are indicative of its status as a preserved differentiated protoplanet

new insights into lunar petrology distribution and composition of prominent low ca pyroxene exposures as observed by the moon mineralogy mapper m3 1 lunar geochemical groups such as mg suite ferroan anorthosite and alkali suite rocks are difficult to distinguish from orbit because they are defined by both modal mineralogy and elemental composition of their constituent minerals while modal mineralogy can be modeled only specific minerals or elements can be directly detected at near infrared nir wavelengths pyroxenes are among the most spectrally distinctive minerals and their absorption bands are sensitive to structure and composition pyroxenes thus provide important clues to distinguish these geochemical groups and to understand lunar crustal evolution using moon mineralogy mapper data we search for lithologies dominated by strong low calcium pyroxene lcp signatures we compare the nir absorptions of 20 lcps to a suite of synthetic pyroxenes to determine which lunar pyroxenes appear magnesian enough to be candidate mg suite norites we detail three prominent regions of lcp 1 in south pole aitken basin spa 2 south of mare frigoris and 3 north of mare frigoris the absorption band positions suggest that the lcps north of mare frigoris and those in spa are compositionally similar to one another and of mg50 75 implying that the mafic material excavated by the spa impact was relatively iron rich modified gaussian modeling results suggest that the apollo basin may have tapped different composition material than is exposed in much of spa the lcps located in the highlands south of mare frigoris exhibit absorption bands at short wavelengths consistent with mg 80 the coincidence of these mg rich lcps with the thorium measured by lunar prospector make them good candidates for kreep related mg suite pyroxenes

the aristarchus plateau on the moon mineralogical and structural study from integrated clementine uv vis nir spectral data abstract combining uvvis and nir clementine spectral data we characterize the mineralogy of the different volcanic and crustal materials occurring on the aristarchus plateau and its close vicinity in order to investigate their stratigraphic relationships and understand the nature of the crust in this region of the moon from an iterative linear mixture modeling we provide a comprehensive description of the distribution and amount of surface mixture of the units and document the stratigraphic relationships in the region of study the determination of clear relationships and origin of the different units forming the structure of the plateau is not obvious as the surface materials to a depth less than 1 km represent complex materials from the imbrium impact event in the aristarchus region we show that the imbrium ejecta has a norite and anorthosite rich composition with the presence of a clinopyroxene component in the uppermost layer aer and ne units in the text alternatively aer may form a rather thick horizon emplaced on an ne rich unit or aer and ne form a single thick horizon showing a gradational compositional change from aer to ne from the south to the north of the plateau due to its size the aristarchus crater must have penetrated through the imbrium ejecta and exposed underlying layers formed by pre imbrian ejecta and or the original crust the regional crustal unit ap for aristarchus peak in the text i e the deepest horizon exposed by the aristarchus crater likely originates from a pluri kilometer depth and is represented by feldspar rich materials with clinopyroxene and olivine as mafic components other deep crustal units at a stratigraphic level close to the deepest horizon ap or intermediate between ap and the uppermost horizon aer and locally distributed in the aristarchus crater and its vicinity aristarchus a crater and the scarp forming the southern edge of the plateau are represented by pyroxene bearing anorthosite sc unit and olivine rich ol unit composition although in low abundance olivine rich materials are found to be widespread in this region of the moon volcanic pyroclastic deposits dmd are widely exposed on the plateau with high abundances and a fairly homogeneous composition we suggest their emplacement could have possibly lasted up to the eratosthenian thus leading to a more important pyroclastic activity in time than previously thought and a rather voluminous and stable reservoir for their source based on their uvvis and nir spectral characteristics sw type materials characterizing the mare basalts west of the plateau are not detected as a major component across the plateau however sw type material is significantly present in the complex ejecta of the aristarchus crater probably due to the particular morphology of the target straddling the edge of the plateau which rises about 2 km above oceanus procellarum the present study based on the integrated visible near infrared clementine dataset paves the way for high spatial resolution surveys based on recent photometric observations e g amie smart 1 and or upcoming detailed spectroscopic observations lism kaguya selene m3 moon mineralogy mapper chandraayan 1

olivine rich exposures in the south pole aitken basin abstract the distribution and the geological context of the olivine rich exposures in the south pole aitken spa basin on the moon were investigated based on the spectral data obtained from the spectral profiler sp and multiband imager mi onboard the japanese lunar explorer kaguya selene the olivine rich exposures are found only in the peak rings or central peaks of the schrodinger basin and zeeman crater which are located in the outer region of the spa basin and not in the center region on a localized scale the olivine rich materials are exposed on landslide features on the crater walls or sloped wall of the central peaks or the peak rings another observational finding is the co existence of olivine rich and plagioclase rich materials on a kilometer scale spanning most of the olivine rich sites in the schrodinger basin pyroxene rich materials are found in fresh craters outside the peak rings or the central peaks with olivine rich materials based on these results the following scenario are proposed 1 the impact to form the spa basin melted a large amount of the lunar upper mantle and crust and distributed the melted materials to the outer region 2 local differentiation of melted materials hid the olivine rich materials in the center region of the spa basin 3 later impacts that formed the schrodinger and zeeman craters excavated and exposed the olivine rich materials to the surface again and 4 space weathering and regolith gardening obscured the olivine rich spectra at the exposure sites but recent small scale impacts or landslides on the sloped wall exposed fresh olivine rich materials allowing the identification of the olivine rich exposures by spectral remote sensing this suggests that several different scale events play an important role in forming the surface distributions of originally deep seated materials on the moon as well as on other planetary bodies

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

temporal behavior of a ventilated claystone at the tournemire url cross spectral analyses focused on daily harmonics abstract the main topic of this communication is the presentation of study auscultation and supervision procedures of deep geological radioactive waste storage repositories using natural harmonic forcings in this paper the effects of natural ventilation on the macroscopic behavior of a clayrock are investigated by means of time series recorded underground over a period of two years in the eastern part of gallery 1996 at the tournemire underground research laboratory url this study is based on time series acquired in the atmosphere at the gallery wall surface and inside the rock mass it includes measured signals from 6 thermo hygrometers 5 crack meters measuring the displacement of 2 shrinkage cracks and 3 tectonic fractures and a 1 meter fdr frequency domain reflectometry profile probe equipped with 6 sensors for measuring the volumetric pore water content into the rock mass auto spectral and cross spectral analyses using the concept of singular spectrum harmonics sshs and cross sshs are developed our analyses and interpretations focus here mainly on the solar diurnal atmospheric tide denoted s1 this tide corresponds to the insolation cycle of the earth atmosphere during a mean solar day 24 h 00 min this component is tracked throughout the various measured signals spectral tracking of tide fluctuations across signals this is equivalent in a way to analyzing the temporal behavior of the url during a mean solar day on earth results indicate that the daily natural forcing caused mainly by a combination of barometric and temperature related fluctuations is the most important effect overall on our various signals the daily harmonic induces the fluctuations of gallery air temperature relative and absolute air humidity and it leads to desaturation of the claystone which in turn leads to the claystone deformation and damage the effects of the annual harmonic sa may also be significant it was fully analyzed in the more complete version of this work however the sa results are not presented here because the spectral resolution on the annual harmonic is insufficient at this stage with only 2 years and 2 months of clean recorded data focusing the present study on daily fluctuations the cross spectral time shifts were obtained from the phase spectrum for the daily component s1 for various pairs of pore water content sensors located at different distances from the gallery wall these time shifts were then used to quantify a spectral velocity which is found to be on the same order than the hydraulic conductivities deduced previously from pneumatic tests performed in the excavation damaged zone of gallery 1996

the structure of the asteroid 4 vesta as revealed by models of planet scale collisions three dimensional simulations of the global evolution of asteroid 4 vesta under two overlapping planet scale collisions closely reproduce its observed shape but expected large areas of olivine rich rocks and pure diogenites are not observed on the surface possibly implying that the outer 100 km is composed mainly of a basaltic crust eucrites with ultramafic intrusions diogenites nasa s dawn mission to the asteroid 4 vesta revealed some unexpected surface features including a huge crater named veneneia underlying the even larger crater rheasilvia that was formed about a billion years ago the juxtaposition of these two impact basins provides an opportunity to develop an accurate model of vesta s topography martin jutzi et al report three dimensional simulations of vesta s global evolution through two successive planet scale collisions their model closely reproduces vesta s observed shape and provides a firm basis for the interpretation of the surface mineralogy and geology of vesta and by extension other small solar system bodies asteroid 4 vesta seems to be a major intact protoplanet with a surface composition similar to that of the hed howardite eucrite diogenite meteorites1 2 3 4 the southern hemisphere is dominated by a giant impact scar5 but previous impact models6 7 8 have failed to reproduce the observed topography the recent discovery that vesta s southern hemisphere is dominated by two overlapping basins9 provides an opportunity to model vesta s topography more accurately here we report three dimensional simulations of vesta s global evolution under two overlapping planet scale collisions we closely reproduce its observed shape and provide maps of impact excavation and ejecta deposition spiral patterns observed in the younger basin rheasilvia9 about one billion years old10 are attributed to coriolis forces during crater collapse surface materials exposed in the north come from a depth of about 20 kilometres according to our models whereas materials exposed inside the southern double excavation come from depths of about 60 100 kilometres if vesta began as a layered completely differentiated protoplanet then our model predicts large areas of pure diogenites and olivine rich rocks these are not seen11 12 13 possibly implying that the outer 100 kilometres or so of vesta is composed mainly of a basaltic crust eucrites with ultramafic intrusions diogenites

mantle material in the main belt battered to bits the complete or near complete differentiation of a chondritic parent body is believed to result in an object with an fe ni core a thick olivine dominated mantle and a thin plagioclase pyroxene crust compositional groupings of iron meteorites give direct evidence that at least 60 chondritic parent bodies have been differentiated and subsequently destroyed a long standing problem has been that our meteorite collections and apparently our asteroid observations as well show a great absence of olivine dominated metal free mantle material while the basaltic achondrites hed meteorites represent metal free pyroxene dominated crustal samples the isotopic and geochemical evidence implies that this class is derived from only one parent body perhaps vesta thus the meteoritic and perhaps astronomical evidence also suggests a great absence of crustal material resulting from the collisional disruption of numerous parent bodies

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

small fresh impact craters on asteroid 4 vesta a compositional and geological fingerprint small morphologically fresh impact craters 10 km in diameter on vesta s surface with a photometrically distinct ejecta blanket are expected to represent fresh surface material and thus provide the opportunity to study the composition of the unweathered surface dawn framing camera and visual and infrared spectrometer vir data reveal impact craters with bright dark and mixed i e partly bright and dark ejecta existing on vesta s surface which not only differ in the visible albedo from their surroundings but also in their composition differences in the composition are related to the visible albedo and or the geographic location of the impact craters bright ejecta only seen in the southern vestan hemisphere are dominated by howardite eucrite like material as expected for vesta s upper crust dark ejecta associated with dark impact craters are dominated by a strongly absorbing spectrally neutral compound supporting an origin from carbon rich impactors few impact craters of intermediate albedo in vesta s southern hemisphere contain material resembling diogenites which are expected to exist in the deeper parts of vesta s interior the geological settings suggest that the diogenite like material represents a part of a layer of diogenitic material surrounding the rheasilvia basin or local concentrations of diogenitic material as part of the ejecta excavated during the latter stage of the rheasilvia impact event the spectral differences between eucrite and diogenite dominated materials also could be verified due to spin forbidden absorptions in the visible spectral range which are known from laboratory spectra of pyroxenes but which have been identified in the vir spectra of vesta for the first time