changes in crack density and wave velocity in association with crack growth in triaxial tests of inada granite 1 a nondimensional second rank tensor fij called the crack tensor has successfully been introduced to deal with geometrical aspects of microcracks fabric such as anisotropy and crack density unfortunately however its usage for practical purposes is rather limited because its determination involves tedious and time consuming laboratory work we seek the possibility of using the directional change of longitudinal wave velocities to conquer the difficulty associated with the determination of crack tensors a new second rank tensor vij is introduced such that the directional change in the longitudinal wave velocities is represented in terms of the tensor and the crack tensor fij is then given as a function of vij on the basis of the analyses of the crack tensors for one intact and several damaged samples of inada granite we then discuss how microcracks grow through the whole inelastic process terminating at brittle failure the conclusions are summarized as follows the second rank symmetrical tensor vij or its inversion tensor vij 1 can be determined experimentally with sufficient accuracy from the directional change in the squared longitudinal wave velocity it is found that the tensor changes markedly so as to reflect the fabric of the damaged inada granite formed by open microcracks the principal axes of vij 1 are coaxial with the principal axes of fij so that both tensors are correlated in terms of their principal values fi and vi 1 four successive stages can be distinguished in regard to the crack growth as follows in stage 1 the rock behaves like an elastic solid in stage 2 microcracks start to grow so that inelastic volumetric strain is slowly accumulated along with microcracking however crack growth does not occur globally but rather is limited within some local zones probably in each grain in stage 3 microcracking is considerably accelerated suggesting that the micromechanism leading to crack growth changes substantially at the boundary stress between stages 2 and 3 in stage 4 the crack density as well as the dilatancy increases explosively in association with a drop of a few percent in the differential stress after the peak stress is reached interestingly this explosive increase is always associated with the development of a few fault zones experimental evidence seems to support the postulate that inada granite starts to collapse once the crack density f0 f the first invariant of fij attains a threshold value of 7 8 regardless of the applied confining pressure this can be a failure criterion in terms of the crack density and be an extended expression for the so called critical dilatancy for creep failure suggested by kranz and scholz 1977

midinfrared spectral features of rocks and their powders 1 we examined the thermal ir spectra of 35 rock samples and their fine powder equivalents to better understand the relationship between spectral features particle size and composition the christiansen features of solid crystalline rocks differ from those of their powdered samples and the magnitude of this difference changes systematically with rock type both the christiansen feature cf and the transparency feature tf in spectra of particulate igneous rocks are useful in rock type determination they correlate better with the scfm chemical index of rock type than with other numerical rock type indices that we considered major rock type divisions acidic intermediate basic and ultrabasic could be distinguished using both cf and tf but some overlap occurred if one or the other spectral feature was used alone spectral contrast decreases as rocks become more basic probably because of increasing opaque mineral content likewise metallic iron formed as a result of space weathering in an airless environment appears to be the most likely cause of reduced spectral contrast in mature lunar soils thus reststrahlen features should be difficult to detect in remote sensing measurements of such bodies as the moon and mercury moreover the vacuum environment of an airless planetary surface appears to enhance the cf but it may eliminate the tf depending critically on particle size the martian pressure and radiative environment on the other hand appears to enhance the tf which should be sought in spectra of finely particulate surface areas on mars additional environmental simulation spectral experiments are needed to more accurately define the roles of pressure particle size opacity and insolation angle on apparent emissivity

radiative transfer modeling of near infrared reflectance of lunar highland and mare soils 1 with near infrared hyperspectral data sets returned from kaguya selene and chandrayaan 1 s moon mineralogic mapper m3 accurate evaluation and interpretation of lunar data sets with higher spectral resolution has never been more critical here we test a new radiative transfer spectral modeling algorithm to determine composition from hyperspectral reflectance spectra of lunar soils data for 19 lunar mare and highland soil samples previously characterized by the lunar soil characterization consortium are used for validation spectral fits are made using a goodness of fit metric considering spectral shape spectral contrast spectral slope and iron abundance high precision fits are achieved for nearly every soil with this algorithm using a plot of spectral shape relative to the ratio mg i e molar mg mg fe 100 determines the winning model and composition mg is determined with an average difference of 11 15 and 3 8 units before and after a correction is applied respectively mineralogy is determined with an average difference of 5 15 vol depending upon the mineral constituent

reflectance spectroscopy of chromium bearing spinel with application to recent orbital data from the moon visible to near infrared v nir remote sensing observations have identified spinel in various locations and lithologies on the moon experimental studies have quantified the feo content of these spinels jackson et al 2014 however the chromite component is not well constrained here we present compositional and spectral analyses of spinel synthesized with varying chromium contents at lunar like oxygen fugacity f o2 reflectance spectra of the chromium bearing synthetic spinels cr 1 29 have a narrow 130 nm wide absorption feature centered at 550 nm the 550 nm feature attributed to octahedral cr3 is present over a wide range in iron content fe 8 30 and its strength positively correlates with spinel chromium content ln reflectancemin 0 0295 cr 0 3708 our results provide laboratory characterization for the v nir and mid infrared mid ir spectral properties of spinel synthesized at lunar like f o2 the experimentally determined calibration constrains the cr of spinels in the lunar pink spinel anorthosites to low values potentially cr 1 furthermore the results suggest the absence of a 550 nm feature in remote spectra of the dark mantle deposits at sinus aestuum precludes the presence of a significant chromite component combined the observation of low chromium spinels across the lunar surface argues for large contributions of anorthositic materials in both plutonic and volcanic rocks on the moon

venus crater related radar dark parabolas and neighboring terrains a comparison of 1 μm emissivity and microwave properties abstract this work presents a comparative study of microwave properties and 1 m emissivity for five venus crater associated radar dark parabolas along with neighboring plains and some other geologic units craters of interest are adivar bassi bathsheba sitwell and du chatelet with nearby crater caccini having non parabolic radar dark halo microwave properties under study include emissivity fresnel reflectivity decameter scale surface roughness and radar cross section from the magellan mission 1 m emissivity was derived using venus monitoring camera vmc measurements on board of venus express vex results of our analysis show that 1 m emissivity which characterizes the uppermost hundreds microns thick layer of parabola mantles usually relates to microwave properties as following the lower 1 m emissivity the lower fresnel reflectivity the higher microwave emissivity for loose mantles having the same composition lower 1 m emissivity indicates smaller particles differences in bulk properties of parabola units showing the same 1 m emissivity appear to reflect differences in a packing style of mantles consisting of particles having similar sizes properties of radar bright inner parabola parts observed within the three of five studied parabolas possibly indicate more turbulent comparing to radar dark parts deposition environment thinner parabola mantles and or partial coverage of the underlying surface the non parabolic halo of the crater caccini exhibits characteristics close to dark parabolas suggesting that in a process of shrinking of a parabolic like deposit into non parabolic one parabola mantle properties remain mainly unchanged observed differences in microwave emissivity and fresnel reflectivity between parabolas and adjacent plains may indicate highly weathered loose parabola material with oxidation of their iron into hematite that is more easily accessible for atmospheric gases studied properties of tessera terrains confirmed suggestions of earlier works for a possible non basaltic composition of tesserae material the distinctive from plains composition of tesserae also could indicates an effective down slope movement of these material uncovering new portions of pristine tessera material otherwise considered in this work horizontal transportation of the very thin layer of surface material would equalize the observed properties

stereology based fabric analysis of microcracks in damaged granite abstract crack related fabric analyses were carried out in terms of crack tensors using inada granite deformed inelastically in a triaxial vessel up to post failure focusing on the fabric changes during brittle failure complementarily numerical simulation tests were conducted to determine the representative volume element rve required for crack surveying numerical simulation tests show that the window size for crack surveying should be at least six times the mean trace length in order to obtain a statistically meaningful crack tensor a larger window is needed to estimate the distribution of crack radii in quartz cracks grow preferentially parallel to the major loading axis crack tensors in quartz can provide a measure of damage reflecting inelastic deformation under differential stress in past geological events during the first stage of inelastic deformation the number density of cracks decreases with a rather sharp increase in crack diameters this happens because pre existing cracks in intact rock join together to make longer cracks however the density remains almost constant during the second stage of loading from 90 to 100 of the peak stress the crack diameter gradually increases due to the stable propagation of cracks when granite is further deformed beyond the peak stress the number density decreases again while sharp increases in crack diameters appear as a result of the forking and coalescence of cracks it is also suggested that load normal grain boundary cracks are generated as a result of the rolling and sliding of disintegrated blocks in the post failure stage

experimental determination of elastic constants of oshima granite barre granite and chelmsford granite employing polyhedral specimens longitudinal and shear wave velocities were measured in various directions of propagation and polarization sound velocities showed orthorhombic elasticity in all of the rocks with the assumption of orthorhombic elasticity the nine stiffness constants of all samples were determined by the sound velocities under atmospheric pressure and kelvin christoffel s equation twenty one stiffness constants of oshima granite determined without assuming any symmetry also showed orthorhombic features directions of the symmetry axes agreed well with the orientation of the preexisting cracks akaike s information criterion showed that the orthorhombic model with nine nonzero elastic stiffnesses was better than the model having 21 nonzero elastic stiffnesses for oshima granite the polyhedrons of two granitic rocks were loaded under hydrostatic pressure all components of the stiffness constants increased with pressure under pressure of more than 120 mpa two granitic rocks were approximately isotropic the results show that oriented microcracks are mainly responsible for the orthorhombic elasticity of the granitic rocks and also indicate that dry oriented cracks can not be a cause for the anisotropic elasticity of granites at depths of more than 6 8 km

lunar central peak mineralogy and iron content using the kaguya multiband imager reassessment of the compositional structure of the lunar crust ryder and wood 1977 suggested that the lunar crust becomes more mafic with depth because the impact melts associated with the large imbrium and serenitatis basins are more mafic than the surface composition of the moon in this study we reexamine the hypothesis that the crust becomes more mafic with depth we analyze the composition of crater central peaks by using recent remote sensing data and combining the best practices of previous studies we compute the mineralogy for 34 central peaks using 1 nine band visible and near infrared data from the kaguya multiband imager 2 an improved version of hapke s radiative transfer model validated with spectra of lunar soils with well known modal mineralogy and 3 new crustal thickness models from the gravity recovery and interior laboratory data to examine the variation in composition with depth we find that there is no increase in mafic mineral abundances with proximity to the crust mantle boundary or with depth from the current lunar surface and therefore that the crust does not become more mafic with depth we find that anorthosite with very low mafic abundance purest anorthosite or pan is a minority constituent in these peaks and there is no clear evidence of a distinct pan rich layer in the middle crust as previously proposed the composition of most of the central peaks we analyze is more mafic than classically defined anorthosites with an average noritic anorthosite composition similar to that of the lunar surface

local and regional lunar regolith characteristics at reiner gamma formation optical and spectroscopic properties from clementine and earth based data a detailed remote sensing survey of the reiner gamma formation rgf region by means of earth based telescopic and clementine multispectral imaging has been made in the uv visible near infrared domain the spectral mixture analysis reveals the existence of three basic end members relevant for modeling the observed spectral variations in the rgf vicinity these are mb mare background sws southwest swirl and rgs reiner gamma soil the first two components exhibit spectral characteristics consistent with a prevailing contribution of mature mare soils for the surroundings mb and of immature mare crater like soils rgs at rgf the third intermediate albedo component sws has general characteristics of a mature mare soil but with a redder continuum slope the reported observation can be modeled by a mechanism which would remove the finest fraction in the soil particle diameter 45 m at rgf and redistribute it in the vicinity with a laterally variable proportion and local accumulations such as at sws site according to the available set of in situ data documenting variations in the chemical composition in the distribution of particle sizes and in the degree of maturity with depth in the mare regolith the characteristics depicted at rgf are those of a subsurface soil layer from a depth of the order of 0 3 0 8 m in our view the simplest way to account for the whole body of information available from the present work lies in the proposition that in the area of rgf the uppermost layer of the regolith has been optically and mechanically modified by a process involving the fall of fragments of a low density cometary nucleus previously disrupted by tidal interaction in the earth moon system we recognize however that in the present state of knowledge one cannot rule out the hypothesized existence of a zone of seismically modified terrain peripheral to the imbrium or orientale basins just beneath the mare surface that would be the actual source of the rgf magnetic anomaly

the lunar regolith chemistry mineralogy and petrology the lunar regolith a several meter thick layer of unconsolidated debris forms the interface between the moon and its space environment the regolith forms from lithic sources by the destructional processes of comminution and the constructional processes of agglutinate formation in this manner a steady state soil can develop and will remain in a type of dynamic equilibrium until the system is disturbed by burial or mixing with new soil mixing takes place mainly on a local scale vertically through meters and horizontally over several kilometers lateral transport is a relatively inefficient process and therefore most of the lunar soil components were derived locally there is no evidence for preferential transport of the finer soil fractions relative to the coarser fractions the truly exotic derived at distances of tens of kilometers component is generally in low abundance 1 therefore remotely sensed data should provide a reasonably accurate picture of bedrock geology the chemical composition of the regolith varies with grain size the 10 m fraction is chemically fractionated from the bulk soil in most cases the 10 m fraction is enriched in al2o3 cao na2o k2o light rare earth elements and th and depleted in mgo feo mno and sc these systematics are largely a result of simple comminution with feldspar and friable mesostasis from local source rocks concentrating in the finest fraction there is evidence that agglutinate glass forms preferentially by fusion of the finest soil fractions therefore agglutinate glass like the 10 m soil fraction appears to be fractionated from bulk soil compositions highland soils are distinct from mare soils both chemically and petrologically soil samples collected near mare highland contacts are mixtures of the two lithologies mineral chemical systematics of monomineralic fragments in the lunar soil provide important clues to soil provenance they can in some cases sort out the highland mare contributions and in special cases can even further pinpoint a lithic source in theory lunar regolith cores can serve as solar probes recording the sun s activity over billions of years in practice this has generally not been the case the formation and evolution of most cores is still poorly understood for most we have not established how they formed for example how many depositional and erosional events were involved what the time span involved in the accretion of the sampled soil column was and how long that soil column has remained in situ without this information it is difficult if not impossible to read the sun s record more interdisciplinary studies on cores must be carried out before they can be used as solar probes

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

surface features of uniaxial tensile fractures and their relation to rock anisotropy in inada granite abstract uniaxial tensile fractures parallel to the rift grain and hardway planes were formed in inada granite most of the fractures split the rock forming mineral grains as transgranular paths under microscopic observations the surface topography of the fractures was measured by the stereo photogrammetric technique and is different in different orientations the rift parallel uniaxial fracture has the smoothest surface and the grain parallel fractures are smoother than hardway parallel fractures the mineral compositions are also different on the failed surfaces of different directions the rift parallel fractures have almost the same constituent mineral ratio as the parent rock however the grain parallel fractures pass preferentially through feldspar grains and contain less quartz grains as compared to the bulk composition of the parent rock in addition it is remarkable on hardway parallel fractures it is considered that the differences of surface topography and mineral compositions are caused by preferred orientations and spatial distributions of pre existing microcracks in inada granite

mapping iron in the lunar mare an improved approach 1 previous methods for mapping iron lucey et al 1995 1998 2000a give inconsistent results in terms of suppressing the effects of maturity making it difficult to distinguish true units of contrasting iron from regions that simply show the residual effects of incomplete separation of maturity these methods rely on an assumption that materials of similar iron content but varying maturity form radial trends on a plot of vis reflectance versus nir vis ratio recently the assumption of radial behavior of maturity trends in mare regions has been called into question by staid and pieters 2000 they observed trends in the mare that appeared more parallel in nature in this work we study nearly 10 000 craters in six mare regions and model the effects of maturity with radiative transfer theory to quantify and better understand the spectral behavior of maturity variations in the mare we confirm that the maturity trends in mare regions are more parallel than radial and we exploit this fact to develop a new algorithm for determination of iron content in mare regions this new mare iron algorithm better compensates for maturity than previous methods and uncertainties due to maturity variations are less than 0 5 wt feo absolute uncertainties are similar to previous algorithms 1 5 wt feo results from this work provide the ability to detect iron anomalies in the ejecta of craters and as a result more confidently map vertical stratigraphy in the lunar mare in terms of iron composition

ti distribution in grain size fractions of apollo soils 10084 and 71501 abstract much work has been devoted to the correlation between the remotely sensed uv vis slope and the tio2 concentration of the lunar surface and this correlation has been used to map the lunar surface tio2 distributions using data obtained from various missions however additional work is needed to fully evaluate the uv vis tio2 correlation such work would help ongoing efforts to improve tio2 mapping e g as currently underway with lroc wide angle camera wac data to evaluate the uv vis tio2 correlation we are investigating soil petrographic factors e g modal abundances of ti bearing minerals lithic and glass hosts ilmenite morphology grain size and maturity that may influence the spectra this ground truth approach will be useful in comparing between sample information and laboratory spectra to investigate the influence of petrographic factors on the spectra in this work we report the quantitative results of a systematic laboratory investigation of three size fractions 210 100 m 100 48 m 48 20 m of two high ti lunar soils 10084 and 71501 using a combined digital imaging backscattered electron image and x ray maps method for each size fraction the results include 1 the modal abundances for single phase minerals and lithologic components 2 the ti distributions among ti host components and 3 the shape of ilmenite grains we compile and compare the data together for the three size fractions of the two high ti soils with different maturities as well as data from previous studies future work will include the investigation of finer size fractions

morphology and formation ages of mid sized post rheasilvia craters geology of quadrangle tuccia vesta abstract a variety of geologic landforms and features are observed within quadrangle av 13 tuccia in the southern hemisphere of vesta the quadrangle covers parts of the highland vestalia terra as well as the floors of the large rheasilvia and veneneia impact basins which results in a substantial elevation difference of more than 40 km between the northern and the southern portions of the quadrangle measurements of crater size frequency distributions within and surrounding the rheasilvia basin indicate that gravity driven mass wasting in the interior of the basin has been important and that the basin has a more ancient formation age than would be expected from the crater density on the basin floor alone subsequent to its formation rheasilvia was superimposed by several mid sized impact craters the most prominent craters are tuccia eusebia vibidia galeria and antonia whose geology and formation ages are investigated in detail in this work these impact structures provide a variety of morphologies indicating different sorts of subsequent impact related or gravity driven mass wasting processes understanding the geologic history of the relatively young craters in the rheasilvia basin is important in order to understand the even more degraded craters in other regions of vesta

microcrack induced elastic wave anisotropy of brittle rocks the failure of brittle rocks during compression is preceded by the formation growth and coalescence of microcracks elastic wave velocities are reduced in the presence of open microcracks and fractures and may therefore be used to monitor the progressive damage of the rock in general these microcracks are not randomly oriented and the rock displays an elastic anisotropy the elastic anisotropy due to cracks can be expressed in terms of a second rank and fourth rank crack density tensor for open cracks the contribution of the fourth rank crack density tensor to the elastic wave velocities is small these results are compared with recent measurements of the ultrasonic compressional and shear wave velocities for propagation parallel and perpendicular to an increasing axial stress applied at constant confining stress to berea sandstone inversion of the velocity measurements indicates that the microcracks propagate parallel to the maximum compressive stress in agreement with current rock mechanics theory a reasonable fit to the data is obtained using only the second rank crack density tensor even though at high confining stress the cracks are expected to be in partial contact along their length this is consistent with the model of elastic wave propagation in a medium containing partially contacting fractures published by white however measurements of off axis wave velocities are required to fully quantify the contribution of the fourth rank crack density tensor

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

oxygen and asteroids hundreds of thousands of asteroids have been discovered in the asteroid belt and in near earth space oxygen is an abundant element in meteorites and presumably in most asteroids spectral reflectance measurements of asteroids in the visible and near infrared can identify oxygen bearing minerals such as those found in the olivine pyroxene and serpentine groups due to their distinctive absorption features interpretation of the mineralogy of asteroids is complicated by the effects of space weathering which tends to redden and darken the surfaces of asteroids asteroids are primarily classified into a number of taxonomic classes and subclasses according to their spectral properties in the visible wavelength region however asteroids with similar spectral properties in the visible may have different spectral properties in the near infrared and therefore different interpreted mineralogies definite trends in the abundances of different taxonomic classes versus heliocentric distance are apparent these trends appear to be a function of both composition differences and degree of heating however dynamical processes have significantly affected these trends close observation of asteroids by spacecraft such as near shoemaker to 433 eros and hayabusa to 25143 itokawa are currently the best way to discern the mineralogies of individual asteroids

grain size evolution and fractionation trends in an experimental regolith the comminution of blocky planetary surfaces into fine grained regoliths was simulated by impacting a fragmental gabbro target 200 times with stainless steel projectiles diameter 6 35 mm mass 1 2g vi 1 35 km s initially the target fragments were 2 32 mm in size with a mean diameter of 15 2 mm which was reduced to 0 4 mm after 200 shots for the first 60 shots comminution was linear with cumulative kinetic energy and thus essentially linear with time the comminution efficiency however decreased at later stages this could be due to a change in fracture mechanism from predominantly intergranular to predominantly intragranular and or due to a change in partitioning of the projectile s kinetic energy from collisional fragmentation or large fragments at early times to cratering in a progressively finer grained medium at later stages mineral specific preferential comminution is abundantly observed in the modal make up of various grain size fractions plagioclase comminutes more readily than pyroxenes plagioclase initially present at 54 vol comprises typically 65 70 of the 125 250 m fraction pyroxenes initially at 33 are depleted to 20 25 this fractionation occurs in the earliest samples analyzed and is not a time dependent phenomenon bulk chemical analyses reveal a corresponding increase in al2o3 cao and na2o and a decrease in feo and mgo the finest grain sizes are generally the most severely affected by differential comminution similar if not exactly identical trends are abundantly documented for lunar soil samples these experimental findings illustrate that differential comminution is capable of producing fractionation in the finest grain sizes they diminish the need for prominent lateral and vertical transport of components otherwise foreign to a lunar soil sampling site as postulated by some workers on the basis of multivariate chemical mixing models

using the modified gaussian model to extract quantitative data from lunar soils 1 the lunar soil characterization consortium lscc has examined and characterized a suite of lunar soils with a wide range of compositions and maturities the purpose of this study is to compare the vis nir spectral properties of these lunar soils with their petrologic and chemical compositions using the modified gaussian model mgm to obtain quantitative data about the character of relatively weak near infrared absorption bands useful compositional information can be extracted from high quality soil spectra using the mgm the model had some difficulty fitting absorption bands in the 2 mm region of the lunar spectrum but bands in the 1 and 1 2 mm regions provided physically realistic results the model was able to distinguish high ca and low ca pyroxenes in the lscc suite of lunar soils in the appropriate relative abundance in addition unexpected insights into the nature and causes of absorption bands in lunar soils were identified for example at least two distinct absorption bands are required in the 1 2 mm region of the spectrum and neither of these bands can be attributed to plagioclase or agglutinates but are found instead to be largely due to pyroxene

the production curve for agglutinates in planetary regoliths models for the production of agglutinates are developed that can be applied to the lunar surface or to any planetary or asteroidal body lacking an atmosphere models are developed using rate equations for progressively more complex situations and range from model 1 which is a simple linear increase of agglutinate content with time to model 4 which includes provision for recycling of existing agglutinates and replenishment and burial of exposed soil model 4 has some aspects of a steady state because depending on the rate constants agglutinate content may be limited to an intermediate value even for long exposure times in an extreme case agglutinate content may be limited to a value near zero these models predict that agglutinates should be low in abundance in areas of thin regolith such as the lunokhod 2 site on the moon and on asteroids the models may also help explain the apparent low agglutinate abundances of lunar regolith breccias and meteorite regolith breccias

mineralogical and chemical characterization of lunar highland soils insights into the space weathering of soils on airless bodies 1 with reflectance spectroscopy one is measuring only properties of the fine grained regolith most affected by space weathering the lunar soil characterization consortium has undertaken the task of coordinated characterization of lunar soils with respect to their mineralogical and chemical makeup it is these lunar soils that are being used as ground truth for all airless bodies modal abundances and chemistries of minerals and glasses in the finest size fractions 20 45 10 20 and 10 m of four apollo 14 and six apollo 16 highland soils have been determined as well as their bulk chemistry and is feo values bidirectional reflectance measurements 0 3 2 6 m of all samples were performed in the reflectance experiment laboratory a significant fraction of nanophase fe0 np fe0 appears to reside in agglutinitic glasses however as grain size of a soil decreases the percentage of total iron present as np fe0 increases significantly whereas the agglutinitic glass content rises only slightly this is evidence for a large contribution to the is feo values from the surface correlated nanophase fe0 particularly in the 10 m size fraction the compositions of the agglutinitic glasses in these fine fractions of the highland soils are different from the bulk chemistry of that size however compositional trends of the glasses are not the same as those observed for mare soils it is apparent that the glasses in the highland soils contain chemical components from outside their terrains it is proposed that the apollo 16 soils have been adulterated by the addition of impact transported soil components from surrounding maria

initial mapping and interpretation of lunar crustal magnetic anomalies using lunar prospector magnetometer data maps of relatively strong crustal magnetic field anomalies detected at low altitudes with the magnetometer instrument on lunar prospector are presented on the lunar nearside relatively strong anomalies are mapped over the reiner gamma formation on western oceanus procellarum and over the rima sirsalis rille on the southwestern border of oceanus procellarum the main rima sirsalis anomaly does not correlate well with the rille itself but is centered over an imbrian aged smooth plains unit interpreted as primary or secondary basin ejecta the stronger reiner gamma anomalies correlate with the locations of both the main reiner gamma albedo marking and its northeastward extension both the rima sirsalis and the reiner gamma anomalies are extended in directions approximately radial to the center of the imbrium basin this alignment suggests that imbrium basin ejecta materials lying in many cases beneath the visible mare surface are the sources of the nearside anomalies if so then the albedo markings associated with the stronger refiner gamma anomalies may be consistent with a model involving magnetic shielding of freshly exposed mare materials from the solar wind ion bombardment two regions of extensive magnetic anomalies are mapped in regions centered on the ingenii basin on the south central farside and near the crater gerasimovic on the southeastern farside these regions are approximately antipodal to the imbrium and crisium basins respectively the imbrium antipode anomaly group is the most areally extensive on the moon while the largest anomaly in the crisium antipode group is the strongest detected by the lunar prospector magnetometer a consideration of the expected antipodal effects of basin forming impacts as well as a combination of sample data and orbital measurements on the nearside leads to the conclusion that the most probable sources of magnetic anomalies in these two regions are ejecta materials from the respective impacts in both regions the strongest individual anomalies correlate with swirl like albedo markings of the reiner gamma class visible on available orbital photography

development of the mars microbeam raman spectrometer mmrs 1 raman spectroscopy is a powerful tool for mineral characterization and for detection of water and organic and inorganic forms of carbon the mars microbeam raman spectrometer mmrs is designed for close up analysis of rocks and soils in planetary surface exploration the mmrs consists of a probe in a flight unit to be deployed by a robotic arm and a spectrograph laser source and electronics in a flight unit to reside on a rover or lander the raman probe has a scanning optical bench that enables a 1 cm linear traverse across a target rock or soil both on target materials as encountered and on fresh surfaces of rocks exposed by abrasion or coring from these spectra one can identify major minor and trace minerals obtain their approximate relative proportions and determine chemical features e g mg fe ratio and rock textural features e g mineral clusters amygdular fill and veins one can also detect and identify organic species graphitic carbon and water bearing phases extensive performance tests have been done on a brassboard model of the mmrs using a variety of geological materials minerals rocks martian meteorites etc these tests show that a raman spectrometer can be built that is suitably miniaturized sufficiently robust and low enough in power usage to serve as an on surface planetary instrument yet the spectrometer can retain high detection sensitivity and yield near laboratory quality spectra over a broad wavelength range these features are essential to provide definitive mineralogy in a planetary exploration

crack tensor based evaluation of inada granite behavior due to damage under true triaxial testing condition abstract in the present work wave velocity measurements were implemented to assess the state of damage in specimens of inada granite the specimens were first loaded under true triaxial testing conditions for which different levels of major principal stress with respect to ultimate strength were applied christoffel s stiffness equation was used to derive elastic properties of the domain via p wave velocity measurements the compliance matrix arrays in the strain stress relationship were then calculated in the most heterogeneous case which involved 21 constants furthermore determination of second and fourth rank crack tensors enabled convenient judgment for the degree of anisotropy expected during permeability and dispersivity studies which are very important in environmental studies it was found that while more attempt to model granitic rocks in their real form is useful the orthorhombic symmetry assumption for the rock under study would eventually render best outcome for realistic simulation purposes of mechanical properties finally areas of application for the proposed development are discussed and prospects of future work by the researchers are outlined

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

a spectral analysis of ordinary chondrites s type asteroids and their component minerals genetic implications three salient features of visible and infrared reflectance spectra of ordinary chondrites ocs and s type asteroids are 1 albedo at 0 56 m 2 continuum slope and 3 depth of the electronic absorption band due to octahedrally coordinated fe2 in olivine and pyroxene these quantities were numerically extracted from the spectra of 23 ocs representing all metamorphic grades and 39 s type asteroids to be plotted in a three dimensional coordinate system the spectral characteristics of three ocs which were comminuted melted recrystallized and recomminuted are also presented in the same format the results show that although laboratory simulation of melt alteration in an asteroidal regolith does alter oc spectra the spectral parameters of these altered meteorites do not change enough to leave the parametric region defined by unaltered oc spectra when the region containing the 39 s asteroid spectra is compared with that of the altered and unaltered ocs it is found that not one of the ocs falls within the s asteroid region the differences may be largely attributed to spectral differences between the respective metallic components the range of s asteroid parameters is then compared with potential pure end member components most likely to result from magmatic differentiation of a chondritic protoasteroid olivine orthopyroxene clinopyroxene and fe ni meteorite metal alternatively represented by the m asteroids it is found that the s asteroid array is consistent with random mixtures of the differentiated components except for a notable dominance of the spectral characteristics of the opaque metallic component these results suggest that the m asteroids may form a composition continuum with the s asteroids we discuss a scenario consistent with this analysis and with the bell et al theory of the geological structure of the asteroid belt ordinary chondritic protoasteroids of all sizes were probably the dominant primary condensates in the inner portion of the main asteroid belt these were later heated by electromagnetic induction or by 26al nuclide decay as a result the smaller ones were subjected to various degrees of metamorphism while the larger ones were subjected to large scale magmatic differentiation petrological domains of the s asteroids beneath a mixed regolith may be large and supply achondrites irons and stony irons to earth rather than well mixed breccias of these components the smaller oc protoasteroids may still be abundant in the asteroid belt but if small enough to escape differentiation may also be small enough to escape earth based identification

mineralogical petrological characterization of near earth asteroids studies of near earth asteroids are aimed at determining their dynamical and structural history the mineralogy and petrology of 17 near earth asteroids are characterized using reflectance spectroscopy with ground based telescopes as one method to address their major issues implications for the origin and evolution are discussed in a separate paper assuming the surfaces are composed of cosmically abundant materials the presence of certain mineralogical species can be determined from diagnostic absorption features and spectral characteristics which have been studied under known laboratory conditions and understood in terms of crystal field theory with one possible exception the surface composition of near earth asteroids consists of common rock forming minerals such as olivine pyroxene and phyllosilicates opaque components are present but cannot be mineralogically identified with existing experimental data the spectrum of 2201 oljato cannot be interpreted in terms of common rock forming minerals this spectrum was examined for cometary features because its high orbital eccentricity suggests a possible relation to comets no common cometary features are identified in its spectrum the predominance of mafic silicate absorption features in spectra of near earth asteroids compared to the majority of main belt asteroids may be a primary compositional feature or may be the signature of relatively fresher asteroid material

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

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

radiative transfer modeling of lunar highlands spectral classes and relationship to lunar samples 1 tompkins and pieters 1999 identified eleven spectral classes present on the surface of the moon here we model these spectral classes to determine the compositions that define them we do this by mathematically matching spectral classes to radiative transfer computed spectra using spectral shape contrast and excursion parameters as defining characteristics model spectra are based upon known mineralogies mafic mineral mg s molar mg mg fe 100 and maturities we compare these compositional results to a compilation of 100 apollo samples to determine plausible representative samples for these spectra results indicate that unique mineralogic solutions for several spectral classes can be determined unambiguously however classes previously interpreted to be pyroxene rich are compositionally ambiguous results suggest these ambiguous mineral assemblages are not random but correlate with variations in absolute reflectance these data further suggest absolute reflectance is a compositionally diagnostic spectral parameter that should be used in conjunction with relative reflectance analysis to constrain mineralogy although absolute reflectance for the eleven spectral classes is not available to constrain their composition we detail mineral chemical i e mg and absolute reflectance variations of matching model relative reflectance spectra to narrow the possibilities this information is used in a pilot study of bullialdus crater for which clementine absolute reflectance is known results indicate bullialdus s central peak consists of tompkins and pieters spectral classes an agn and n bullialdus s spectra that match class n are roughly consistent with previous compositional interpretations however matches to classes an and agn indicate more mafic assemblages typical of mg suite norite gabbronorite rocks

in situ optical measurements of chang e 3 landing site in mare imbrium 1 mineral abundances inferred from spectral reflectance the visible and near infrared imaging spectrometer on board the yutu rover of chinese chang e 3 mission measured the lunar surface reflectance at a close distance similar to 1m and collected four spectra at four different sites these in situ lunar spectra have revealed less mature features than that measured remotely by spaceborne sensors such as the moon mineralogy mapper instrument on board the chandrayaan 1 mission and the spectral profiler on board the kaguya over the same region mineral composition analysis using a spectral lookup table populated with a radiative transfer mixing model has shown that the regolith at the landing site contains high abundance of olivine themineral abundance results are consistent with that inferred from the compound measurement made by the on board alpha particle x ray spectrometer

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

late miocene and early pliocene environments in the southwestern black sea region from high resolution palynology of dsdp site 380a leg 42b a high resolution palynological study has been performed on late miocene messinian and early pliocene zanclean sediments cored at dsdp site 380a leg 42b a late miocene coastal vegetation has been identified in association with a delta environment the pliocene is characterised by competition between the two most important vegetation components namely humid thermophilous forests and dry steppes with changes driven by large amplitude climatic variations these variations are linked to other european reference pollen records and to the global temperature evolution for the early pliocene and result in climatostratigraphic relationships at large geographic scale an orbital tuning is proposed with respect to new data clarifying time control on the section the black sea appears to have dried up in response to the messinian salinity crisis in the mediterranean with which it might have been connected during periods of high sea level

the evolution of elastic moduli with increasing crack damage during cyclic stressing of a basalt from mt etna volcano article i nfo volcanic edifices such as mt etna italy are commonly subject to repeated cycles of stress over time due to the combination of magma emplacement from deep reservoirs to shallow depths and superimposed tectonic stresses such repeated stress cycles lead to anisotropic deformation and an increase in the level of crack damage within the rocks of the edifice and hence changes to their elastic moduli which are a key parameter for reliable modelling of deformation sources we therefore report results of changes in elastic moduli measured during increasing amplitude cyclic stressing experiments on dry and water saturated samples of etna basalt in all experiments the young s modulus decreased by approximately 30 over the total sequence of loading cycles and the poisson s ratio increased by a factor of approximately 3 0 5 microseismicity in terms of acoustic emission ae output was also recorded throughout each experiment our results demonstrate that ae output only re commences during any loading cycle when the level of stress where ae ceased during the unloading portion of the previous cycle is exceeded a manifestation of the kaiser stress memory effect in cycles where no ae output was generated we also observed no change in elastic moduli this result holds for both mechanical and thermal stressing our results are interpreted in relation to measurements of volcano tectonic seismicity and deformation at mt etna volcano

microstructural based time dependent failure mechanism and its relation to geological background abstract the time dependent hydro mechanical behavior of rocks is important in assessing the long term stability of deep underground excavation sites meant for long term storage of radioactive waste while evaluating the manner in which damage growth progresses at an excavation site it is important to represent the failure criteria and microcrack evolution from the viewpoint of factors pertaining to microcrack geometry such as the crack density we performed creep tests on inada granite samples to examine the effects of water confining pressure and weathering on time dependent failure the crack density of the samples which was damaged at three characteristic stages of creep behavior i e primary secondary and tertiary creep was measured by means of a longitudinal wave velocity test the microcrack evolution and failure criteria are discussed on the basis of the crack tensor determined in the test the following conclusions were reached from the test results 1 the onset of tertiary creep corresponds to the peak stress under static loading conditions and the tertiary creep stage corresponds to the post failure region 2 at the onset of tertiary creep the crack density can be the failure criterion for time dependent failure and crack density can be estimated using the longitudinal wave velocity 3 the time to failure for weathered granitic rock is approximately ten times faster than that for intact granitic rock 4 the ratio of the mica group mineral in the granite may affect the time to failure a fact that offers insight into the time dependent stability of a rock mass on the field scale

systematic global mixing and melting in lunar soil evolution 1 we present a revised model of soil evolution constrained by the recent lscc data for lunar soils in addition to an observed universal increase in feldspathic components in the finer fractions of soils taylor et al 2001 2003a 2003b both differential melting and lateral mixing processes appear to be required during the evolution of lunar soils we propose mare highland mixing of a significant glass component along with a preferential melting sequence for agglutinitic glass formation of glass plagioclase pyroxene ilmenite

the compositional and physical properties of localized lunar pyroclastic deposits abstract lunar localized pyroclastic deposits are low albedo deposits with areas 2 these deposits were difficult to study before the turn of the millennium because of the lack of available high spatial resolution data with the launch of the lunar reconnaissance orbiter kaguya and chaandrayan 1 new sets of diverse high spatial resolution data are now available using several of these data sets we conducted a study of 34 localized pyroclastic deposits globally for each localized pyroclastic deposit we examined topography to estimate pyroclastic volume and juvenile proportions s band radar backscatter thermal infrared derived measures of surficial rock abundance and regolith density and mineral abundances our goals are to 1 quantitatively characterize the physical and mineralogical properties of each localized pyroclastic deposit 2 investigate the physical and mineralogical variations among localized pyroclastic deposits 3 compare these properties of localized 2 to regional pyroclastic deposits 2500 km 2 and 4 provide useful parameters for future volcanological modeling from this study we find that 1 localized pyroclastic deposits exhibit low relief structures 2 the surface rock abundance and circular polarization ratio of localized pyroclastic deposits display a wide range of values 0 2 0 5 and 0 3 0 6 respectively 3 the glass abundance of localized pyroclastic deposits vary between 0 and 80 wt 4 there are four types of localized pyroclastic deposits based upon the surface rock abundance and glass abundance parameters 5 pyroclastic deposits within the same floor fractured crater tend to have similar properties and 6 localized pyroclastic deposits are diverse with respect to regional pyroclastic deposits but a subset of localized pyroclastic deposits have similar physical and mineralogical properties to regional pyroclastic deposits

spectral properties of near earth asteroids evidence for sources of ordinary chondrite meteorites although ordinary chondrite oc meteorites dominate observed falls the identification of near earth and main belt asteroid sources has remained elusive telescopic measurements of 35 near earth asteroids 3 kilometers in diameter revealed six that have visible wavelength spectra similar to laboratory spectra of oc meteorites near earth asteroids were found to have spectral properties that span the range between the previously separated domains of oc meteorites and the most common s class asteroids suggesting a link this range of spectral properties could arise through a diversity of mineralogies and regolith particle sizes as well as through a time dependent surface weathering process

discrimination between maturity and composition of lunar soils from integrated clementine uv visible near infrared data application to the aristarchus plateau the reflectance spectrum of a lunar soil is mainly dominated by the composition and the degree of exposure to space weathering processes such as micrometeorite bombardment and solar wind implantation the spectral alteration effects of space weathering should be removed for accurately investigating the composition of the lunar surface using remote sensing data in this paper we show that the integration of the clementine uv visible uvvis and near infrared nir channels provides an improved evaluation of the spectral alteration the depth of the mafic absorption feature at 0 95 m is also better defined by combining the uvvis and nir data laboratory spectra of lunar soil samples indicate that the continuum slope derived from the 1500 750 nm ratio is closely related to the concentration of fine grained submicroscopic iron is the continuum slope therefore provides an evaluation of the spectral alteration of the surface which can be subtracted from the 1 or 2 m absorption band depths to retrieve compositional information this method has been applied to the aristarchus plateau which exhibits a broad range of mineralogical composition and maturity a nine channel multispectral mosaic of 680 clementine images of the aristarchus plateau has been processed eight telescopic spectra have been used to check the validity of the reduction process for the near infrared bands the 1 m absorption band once corrected for spectral alteration provides an evaluation of the initial feo content in mafic silicates mafic iron lunar soil samples show that it is possible to quantitatively map mafic iron with this technique our results are in good agreement with those obtained using the algorithm of lucey et al 1995 1998a which is based on uvvis bands alone the mafic iron content and total iron content which can be derived from the combined uvvis and nir data sets are less sensitive to local slopes than that derived from lucey et al s method this new method could therefore be useful for investigating areas at middle to high latitudes removing spectral alteration from the 2000 1500 nm ratio also makes possible a better discrimination between olivine and pyroxene within identified mare basalts on the aristarchus plateau

galileo encounter with 951 gaspra first pictures of an asteroid galileo images of gaspra reveal it to be an irregularly shaped object 19 by 12 by 11 kilometers that appears to have been created by a catastrophic collisional disruption of a precursor parent body the cratering age of the surface is about 200 million years subtle albedo and color variations appear to correlate with morphological features brighter materials are associated with craters especially along the crests of ridges have a stronger 1 micrometer absorption and may represent freshly excavated mafic materials darker materials exhibiting a significantly weaker 1 micrometer absorption appear concentrated in interridge areas one explanation of these patterns is that gaspra is covered with a thin regolith and that some of this material has migrated downslope in some areas

surface modification of olivine by h and he bombardment laboratory simulations of solar wind irradiation of olivine a constituent of ordinary chondritic meteorites and s type asteroids show a dramatic chemical reduction of surface iron and to a lesser extent silicon earth s atmosphere oxidizes any reduced iron instantaneously whereas irradiated material on the surface of an asteroid would remain reduced changes in optical reflectance due to metallization of the surface provide a possible explanation for differences in the near infrared spectra of ordinary chondrite meteorites and their likely parent bodies the s iv asteroids

radiative transfer modeling of compositions of lunar pyroclastic deposits 1 while over 100 lunar pyroclastic deposits have been identified remotely their compositions remain poorly constrained in this work we determine the compositions of three lunar regional pyroclastic deposits which are likely to contain large amounts of glass and for which we have high quality ground based spectra the aristarchus plateau mare humorum and sulpicius gallus we use radiative transfer theory and employ measured optical constants of glasses to predict the bidirectional reflectance of a particulate glass surface as a function of fe and ti concentration particle size and maturity in order to find the best spectral match to the remotely observed deposits tools are not available to model the optical effects of the unusual geometries of the ilmenite laths in the black beads so we address their effects on spectra of the regional pyroclastic deposits using computational mixing we find that model spectra of pure glass as opposed to devitrified black beads provide good matches to all three regions radiative transfer modeling predicts iron contents of 21 20 and 17 wt feo for aristarchus humorum and sulpicius gallus respectively and suggests that all three regions are low in titanium a result supported by lunar prospector neutron spectrometer data however we find that a moderate ti glass mixed with a small fraction of black beads cannot be ruled out for the sulpicius gallus region

olivine bearing lithologies on the moon constraints on origins and transport mechanisms from m 3 spectroscopy radiative transfer modeling and grail crustal thickness abstract high resolution hyperspectral data from chandrayaan 1 s moon mineralogy mapper m 3 allow detection of olivine on the lunar surface olivine exposed at the surface may originate as mantle material or igneous products intrusive or extrusive potential transport mechanisms include excavation of the mantle or lower crustal material by impacts that form basins and complex craters differentiation of impact melt sheets or magmatic emplacement of lavas cumulates or xenoliths a sample of the lunar mantle which has not been conclusively identified in the lunar sample collection would yield fundamental new insights into the composition structure and evolution of the lunar interior olivine identified in remote spectral data is generally accepted to originate from the primary mantle because abundant olivine is expected to exist in the mantle and lower crust yet have sparse occurrences in the upper crust in this study we identified 111 m 3 single pixel spectra with characteristic absorption features consistent with olivine at crisium nectaris and humorum basins and near the craters roche and tsiolkovsky in an effort to determine the origins and transport mechanisms that led to these individual exposures we estimated mineral abundances using radiative transfer modeling and examined crustal thickness estimates topography and slope maps and images from the lunar reconnaissance orbiter camera lroc at crisium basin where crustal thickness is near 0 km wieczorek et al 2013 mantle olivine may have been exposed by basin forming impact and deposited on the rim picard crater which is superposed on the floor of crisium also exhibits potential mantle olivine in its ejecta within nectaris basin olivine exposures are confined to the rims of small craters on the mare which are inferred to excavate a layer of olivine rich mare basalt olivine occurrences on the rim of humorum basin including those located on a graben are likely to be cumulates of shallow intrusions that were transported magmatically to the surface near roche crater olivine may have originated in shallow dikes that reached the subsurface and were exposed by impacts in addition to verifying both known and previously unidentified olivine exposures our combined geophysical spectral and radiative transfer modeling investigation has allowed identification of both igneous and mantle derived olivine

optical effects of space weathering the role of the finest fraction the optical properties of lunar softs are different than those of rocks from which they are derived as a consequence of lunar space weathering soils are darker and exhibit a distinctive red sloped continuum and weaker mineral absorption bands the accumulation of dark glass welded aggregates agglutinates has been thought to account for these optical effects of space weathering on lunar soils spectroscopic analyses of agglutinate separates and size fractions for a suite of lunar softs presented here indicate that the agglutinate paradigm is insufficient to fully account for lunar optical alteration it is the finest fraction of lunar soils 25 gm which constitute 25 wt that dominates the optical properties of the bulk soil unlike size fractions of most silicates for which the finest fraction is the brightest the lunar soil size fractions all have comparable albedos in the short wavelength visible in the near infrared however it is the finest fraction that exhibits the steep red continuum and weak absorption bands the properties of the finest fraction cannot be duplicated by preparing a fine fraction by grinding larger agglutinate rich soil particles these results suggest space weathering on airless bodies is dominated by surface correlated processes perhaps associated with the development of fine grained fe o on or near the surface of grains and the accumulation of the larger agglutinates is not necessarily required to account for lunar optical alteration

rotational spectral variations of asteroid 8 flora implications for the nature of the s type asteroids and for the parent bodies of the ordinary chondrites abstract the new interpretive calibrations olivine pyroxene abundance spectral signature of chondritic metal grains have been applied to visible and near infrared spectral reflectance data for the typical s type asteroid 8 flora chondritic metal grains do not exhibit the steeply reddened spectral signature previously associated with a nickel iron nife metal phase the conditions required to produce a s type spectral curve from a chondritic material are much more restrictive and improbable than previously supposed five mineralogic and patrologic parameters have been derived for the surface material of flora from the analysis of the spectral reflectance and rotational spectral variations of this object these include bulk mineralogy nife metal olivine pyroxene mafic mineral abundance ol py 2 8 metal nature abundant 50 and coarse grained in the substrate pyroxene composition orthopyroxene f s 50 and or abundant clinopyroxene and spatial mineralogic variations olivine pyroxene ratio and pyroxene composition do not covary in a chondritic manner all of the diagnostic mineralogic properties of the flora surface material indicate that this is a differentiated body none of the derived surface properties unambiguously support a chondritic type material and several contradict any type of undifferentiated assemblage flora is most probably the residual core of an intensely heated thermally evolved and magmatically differentiated planetesimal which was subsequently disrupted the present surface samples layers formed at and near the core mantle boundary in the parent body several lines of evidence suggest that the s type asteroids as a class are predominantly the core fragments of disrupted differentiated planetesimals a main belt source of the ordinary chondrites remains elusive

a preliminary global map of the vector lunar crustal magnetic field based on lunar prospector magnetometer data processing and mapping of the lunar prospector magnetometer data is supported by the nasa discovery data analysis program

analysis of lunar pyroclastic deposit feo abundances by lro diviner 1 thermal infrared reflectance spectra of rock forming minerals include a prominent minimum near 8 m known as the christiansen feature cf the inflection point wavelength is sensitive to the degree of polymerization of silicates which is strongly influenced by major cations notably iron in the minerals laboratory spectra of lunar soils demonstrate that the cf location is closely correlated to the sample s bulk feo abundance across the full range of apollo soil samples including pyroclastic glass this correlation is the basis for estimating lunar surface feo abundances using orbital thermal infrared measurements the diviner lunar radiometer experiment on the lunar reconnaissance orbiter includes three thermal infrared channels selected to determine the cf positions for sites across the lunar surface diviner measurements are used to derive feo abundances in the aristarchus sulpicius gallus and rima fresnel pyroclastic deposits the calculated feo abundances for aristarchus and sulpicius gallus lie within the compositional range of feo rich pyroclastic glasses but outside the range of most mare soils supporting the interpretations of these deposits as glass rich the calculated feo abundance for the rima fresnel deposit is close to that of mare soils supporting a contention that this deposit is dominated by basaltic fragments rather than glass the diviner measurements hold the potential to determine feo abundances in many lunar pyroclastic deposits a better understanding of these compositions will provide insight into the magmatic history and composition of the lunar interior as well as an enhanced inventory of potential resources for future human exploration

characterization of lunar swirls at mare ingenii a model for space weathering at magnetic anomalies 1 analysis of spectra from the clementine ultraviolet visible and near infrared cameras of small immature craters and surface soils both on and adjacent to the lunar swirls at mare ingenii has yielded the following conclusions about space weathering at a magnetic anomaly 1 despite having spectral characteristics of immaturity the lunar swirls are not freshly exposed surfaces 2 the swirl surfaces are regions of retarded weathering while immediately adjacent regions experience accelerated weathering 3 weathering in the off swirl regions darkens and flattens the spectrum with little to no reddening which suggests that the production of larger 40 nm nanophase iron dominates in these locations as a result of charged particle sorting by the magnetic field preliminary analysis of two other lunar swirl regions reiner gamma and mare marginis is consistent with our observations at mare ingenii our results indicate that sputtering vapor deposition implanted solar wind hydrogen and agglutination share responsibility for creating the range in npfe0 particle sizes responsible for the spectral effects of space weathering

remote sensing of potential lunar resources 2 high spatial resolution mapping of spectral reflectance ratios and implications for nearside mare tio2 content high spatial resolution maps illustrating variations in spectral reflectance 400 560 nm ratio values have been generated for the following mare regions 1 the border between southern mare serenitatis and northern mare tranquillitatis including the ms 2 standard area and apollo 17 landing site 2 central mare tranquillitatis 3 oceanus procellarum near seleucus and 4 southern oceanus procellarum around flamsteed we have also obtained 320 1000 nm reflectance spectra of several sites relative to ms 2 to facilitate scaling of the images and provide additional information on surface composition inferred tio2 abundances for these mare regions have been determined using an empirical calibration which relates the weight percent tio2 in mature mare regolith to the observed 400 560 nm ratio mare areas with high tio2 abundances are probably rich in ilmenite fetio3 a potential lunar resource the highest potential tio2 concentrations we have identified in the nearside maria occur in central mare tranquillitatis inferred tio2 contents for these areas are 9 wt and are spatially consistent with the highest tio2 regions mapped previously at lower spatial resolution we note that the morphology of surface units with high 400 560 nm ratio values increases in complexity at higher spatial resolutions new telescopic spectra of landing sites successfully reproduce the charette relation although we find that the 400 560 nm value is strongly a fimction of the sample area size the increased spectral contrast of the 400 730 nm ratio over the 400 560 nm ratio demonstrates the potential increased precision with which the 400 730 nm ratio might be used to estimate tio2 abundances comparisons have been made with previously published geologic maps lunar orbiter iv and ground based images and some possible morphologic correlations have been found between our mapped 400 560 nm ratio values and volcanic landforms such as lava flows mare domes and collapse pits

ilmenite mapping of the lunar regolith over mare australe and mare ingenii regions an optimized multisource approach based on hapke radiative transfer theory 1 we model lunar ilmenite abundances over mare australe and mare ingenii regions using a new approach we integrate lunar reconnaissance orbiter wide angle camera wac and clementine uv visible near infrared uvvis nir data to obtain a 14 band mosaic 320 2000 nm we use hapke s radiative transfer equations to compute spectra for various mixtures of orthopyroxene clinopyroxene plagioclase olivine and ilmenite with varying grain size chemistry and degree of maturity and find the closest match between the modeled spectra and the spectra of the less mature pixels optical maturity 0 2 in the 14 band mosaic we calculate a maximum stoichiometrically possible ilmenite content using clementine derived tio2 abundances and the amount of tio2 in stoichiometric ilmenite and use it as a constraint in our model we validate our methodology with lunar soil spectra of known composition our results show that the integrated wac uvvis nir data and the uvvis nir data overestimate ilmenite abundances by 8 80 wt and 7 97 wt respectively when a fixed maximum of 20 wt ilmenite is used when the maximum stoichiometrically possible ilmenite content is used as a constraint the integrated wac uvvis nir data give slightly more accurate ilmenite abundance estimation 2 87 wt than when using only uvvis nir data 3 04 wt we find ilmenite concentrations of 0 11 wt in mare australe and 0 6 wt in mare ingenii region ilmenite abundances between 4 and 7 wt are exposed in mare australe whereas ilmenite abundances between 7 and 11 wt are found on the walls of 0 6 11 8 km diameter craters within mare australe

an experimental investigation of agglutinate melting mechanisms shocked mixtures of apollo 11 and 16 soils mixtures of chemically contrasting lunar soils from a 11 and a 16 have been shocked at pressures ranging from 18 2 62 0 gpa 182 620 kb other than the generation of impact melts modal and textural changes caused by shock include destruction of pore space and fused soil clasts and conversion of plagioclase to maskelynite the loss of the fused soil component in these runs indicates that low agglutinate contents in shocked and or compacted regolith breccias cannot be considered by themselves to be evidence of formation from immature regolith from the petrographic and chemical data it appears that the impact glass formed mainly from the fine fraction and the fused soil component in the target with relatively minor contributions from the other coarse clasts the impact glasses exhibit the same chemical enrichments and depletions as their corresponding fine fractions and plot on or near a mixing line between the bulk and fine fraction of the soil in which they were formed from this as well as several other studies it appears that the fusion of the finest fraction f3 model is valid and that it accurately predicts the chemical systematics of impact glass formed from lunar soil in addition fusion of agglutinates present in the target soil is an important process

almahata sitta asteroid 2008 tc3 and the search for the ureilite parent body abstract this article explores what the recovery of 2008 tc3 in the form of the almahata sitta meteorites may tell us about the source region of ureilites in the main asteroid belt an investigation is made into what is known about asteroids with roughly the same spectroscopic signature as 2008 tc3 a population of low inclination near earth asteroids is identified with spectra similar to 2008 tc3 five asteroid families in the main belt as well as a population of ungrouped asteroids scattered in the inner and central belts are identified as possible source regions for this near earth population and 2008 tc3 three of the families are ruled out on dynamical and spectroscopic grounds new near infrared spectra of 142 polana and 1726 hoffmeister lead objects in the two other families also show a poor match to almahata sitta thus there are no main belt spectral analogs to almahata sitta currently known space weathering effects on ureilitic materials have not been investigated so that it is unclear how the spectrum of the main belt progenitor may look different from the spectra of 2008 tc3 and the almahata sitta meteorites dynamical arguments are discussed as well as ureilite petrogenesis and parent body evolution models but these considerations do not conclusively point to a source region either other than that 2008 tc3 probably originated in the inner asteroid belt

composition of the lunar highland crust from near infrared spectroscopy near infrared reflectance spectra of the lunar highlands are synthesized to obtain global information about the composition of the lunar near side crust immature exposed surfaces from small fresh craters mountains and massifs and large craters with central peaks are included in a survey of rock types across the lunar near side compositions recognized in these data include anorthosite noritic gabbric and troctolitic mineral assemblages three quarters of the areas studied that represent samples from the upper 1 2 km of lunar crust exhibit noritic compositions with different amounts of pyroxene and or brecciation alteration norites are ubiquitous across the near side and show no spatial clustering associated with any of the major basins in contrast to this noritic megaregolith of the upper crust material representing stratigraphically deeper zones 5 15 km of the lunar crust is dominated by gabbros anorthosites and troctolites with less than a quarter of the areas studied exhibiting a noritic composition the origin of the noritic megaregolith and its relation to deeper crustal material is thus somewhat of an enigma the current limited statistics for areas identified as anorthosites and troctolites are insufficient to derive global spatial distributions gabbroic areas however are notably concentrated in the western hemisphere although incomplete for a global assessment of crustal materials these data demonstrate that the lunar near side crust is clearly mineralogically heterogeneous both laterally and vertically and not well mixed below 1 2 km

a large spectral survey of small lunar craters implications for the composition of the lunar mantle a global spectral survey of 4506 immature craters with diameters 1 km was carried out using near ir data from the kaguya spectral profiler to characterize the composition of the lunar megaregolith on the basis of band minima and radiative transfer mixing models small crater spectra fall into three groups 1 mare basalts with strong absorptions at relatively long wavelengths indicating high ratios of high to low ca pyroxene 2 norites containing about 50 plagioclase and with pyroxene assemblages dominated by low ca pyroxene that occur within the south pole aitken basin spa near apollo 14 and other locations near imbrium basin and three major cryptomaria deposits and 3 noritic anorthosites occurring within the feldspathic highlands terrane containing about 20 wt pyroxene with a pyroxene assemblage containing exclusively very low ca pyroxene very few pure anorthosites are present in this survey and there are no occurrences of pyroxene poor olivine rich assemblages models of the composition of basin ejecta incorporate large amounts of mantle material and the spectral results require that that the sampled mantle is orthopyroxenite basin depth diameter ratios used in the models required to match the measured composition are consistent with prior estimates for the largest basins the composition found in the spa and imbrium regions are consistent with mafic impact melt breccias or basaltic impact melts of basin origin for spa we model this composition and find it requires an extremely low impact angle while this is consistent with prior work on an oblique impact for the spa event a more robust solution invokes the production of norite in impact melt seas

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

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

microcracks in rocks a review abstract in the past decade the number of studies about microcracks in rocks has rapidly increased this review of recent work concentrates on microcracks in rock as separate entities emphasizing microcrack morphogenesis kinematics dynamics population statistics and observational techniques cracks are produced when the local stress exceeds the local strength the local stress may be augmented by twin lamellae interactions kink bands and deformation lamellae stress concentrations at grain boundary contacts and around intracrystalline cavities local strength may be reduced along cleavage planes along grain boundaries and along any internal surface as a result of corrosion by chemically active fluids dislocations appear not to be a significant factor for crack nucleation below about 500 c in silicates spatial and temporal changes in temperature can also induce microcracking as a result of differential thermal expansion between grains with different thermoelastic moduli and thermal conductivities the amount of quartz in the rock has a significant effect on thermally induced microcracks because of its large and variable thermal expansivity the application of hydrostatic pressure between 100 and 200 mpa effectively closes most cracks but the closure may not be uniform if crack wall asperities exist hydrostatic pressure appears to stabilize cracks and make crack growth more difficult the number and average size of mechanically induced microcracks is greater in rock deformed at higher pressures the application of a deviatoric stress field on the boundaries of a rock mass results on a microscopic scale in a very complex stress system which greatly affects nucleation and propagation paths the relative amount of intragranular and intergranular cracking appears to depend upon mineralogy rock type and stress state the vast majority of stress induced microcracks in rocks appear to be extensional statistically they are predominantly oriented within 30 of the macroscopic maximum stress direction crack densities increase as macroscopic deviatoric stress increases above a threshold level crack size distributions may be either lognormal or exponential fracture in rock under compressive boundary loads is a result of the coalescence of many microcracks not the growth of a single crack some crack configurations are more favorable for coalescence than others as deviatoric stress increases and rock failure is approached the microcrack population changes spatially from random to locally intense zones of cracking away from the fault the crack density dies off rapidly to the background level a few grains away under lesser deviatoric stresses slow subcritical microcrack growth can occur as a result of stress aided corrosion at the crack tip the rate governing mechanism may be either the chemical reaction rate or the rate at which water can get to the crack tip important details still remain to be worked out

iron abundances on the lunar surface as measured by the lunar prospector gamma ray and neutron spectrometers i global measurements of iron abundances on the lunar surface are presented using data from the lunar prospector lp gamma ray spectrometer grs and neutron spectrometer ns in this study we derive relative iron abundances from the low altitude high spatial resolution 45 km 2 lp data using the 7 6 mev neutron capture gamma ray doublet as part of the lp grs analysis we demonstrate the importance of accounting for variations in neutron number density across the lunar surface by measuring neutron fluxes using lp ns data in a first step of comparing the lp grs data with previously published iron abundances inferred from clementine spectral reflectance csr data we show that the existing csr feo data are nonlinear with respect to the lp relative iron abundances we use the lp data to linearize the relationship between the csr and the relative iron values then recalibrate the csr data to iron abundance using returned soil abundances we then correlate the csr data except for major anomalies with the lp relative iron measurements to convert the lp data to absolute iron abundances when we compare the lp grs and revised csr data sets we find a very good correspondence there are two locations mare tranquillitatis and south pole aitken spa basin that show major discrepancies suggesting that the csr data are locally overestimating iron abundances in both these regions the discrepancies identified by the lp grs csr comparison are possibly explained by mineralogical differences that are not accounted for in the csr to feo calibration in regards to our understanding of the moon the lp data have found the following i there exist large expanses of mare basalt in the western mare regions that have very high iron abundances 22 23 wt feo that are underrepresented but not absent from the returned sample collection and are highly unusual for mare soils which typically contain a significant amount of highlands contamination 2 the low iron abundances in the lunar highlands 5 feo wt are consistent with a previous analysis using thermal and epithermal neutrons and with the idea that the lunar crust formed by a relatively simple magma ocean process 3 the comparison of lp and csr derived iron abundances suggests that the material within spa basin is similar to a norite type rock without an enriched mantle feo signature 4 a comparison of lp and csr data at tycho crater shows a large discrepancy such that the csr data show moderate iron abundances of 8 9 wt feo while the lp data show very low iron abundances of 3 4 wt feo this discrepancy cannot yet be easily explained by any known process