the basaltic shergottite northwest africa 856 petrology and chemistry we report on the discovery of a new shergottite from south morocco this single stone weighing 320 g is referenced as northwest africa nwa 856 with djel ibone as a synonymous name it is a fresh fine grained basaltic rock consisting mainly of two pyroxenes total similar to68 vol 45 pigeonite en 61 16 wo 9 22 fs 26 68 23 augite en 46 26 wo 34 29 fs 21 43 and plagioclase converted to maskelynite similar to23 vol ab 43 57 or 1 5 an 54 36 accessory minerals include merrillite cl apatite pyrrhotite ilmenite ulvospinel silica stishovite and glass amorphous k feldspar and baddeleyite amorphous mixtures of maskelynite and silica occur most commonly as median layers inside maskelynite laths in addition melt pockets similar to2 vol were recognized with relics of maskelynite pyroxene and both dense silica glass and stishovite occurring as both grains and submicrometer needles the compositions of the melt pockets are consistent with mixtures of maskelynite and pyroxenes with an average of similar to50 vol maskelynite the meteorite is highly fractured at all scales

new observations on shatter cones in the vredefort impact structure south africa and evaluation of current hypotheses for shatter cone formation shatter cones have been described from many meteorite impact structures and are widelyregarded as a diagnostic macroscopic recognition feature for impact however the origin of thismeso to macroscopic striated fracture phenomenon has not yet been satisfactorily resolved and thetiming of shatter cone formation in the cratering process still remains enigmatic here previousresults from studies of shatter cones from the vredefort impact structure and other impact structuresare discussed in the light of new field observations made in the vredefort dome contrary to earlier claims vredefort cone fractures do not show uniform apex orientations at any given outcrop nor do small cones show a pattern consistent with the previously postulated master cone concept simple back rotation of impact rotated strata to a horizontal pre impact position also does not lead to a uniform centripetal upward orientation of the cone apices striation patterns on the cone surfaces are variable ranging from the typically diverging pattern branching off the cone apex to subparallel to parallel patterns on almost flat surfaces striation angles on shatter cones do not increase with distance from the center of the dome as alleged in the literature instead a range of striation angles is measured on individual shatter cones from a specific outcrop new observations on small scale structures in the collar around the vredefort dome confirm the relationship of shatter cones with subparallel sets of curviplanar fractures so called multipli striated joint sets msjs pervasive meter scale tensile fractures cross cut shatter cones and appear to have formed after the closely spaced msj type fractures the results of this study indicate that none of the existing hypotheses for the formation of shatter cones are currently able to adequately explain all characteristics of this fracturing phenomenon therefore we favor a combination of aspects of different hypotheses that includes the interaction of elastic waves as supported by numerical modeling results and which reasonably explains the variety of shatter cone shapes the range of striation geometries and angles and the relationship of closely spaced fracture systems with the striated surfaces in the light of the currently available theoretical basis for the formation of shatter cones the results of this investigation lead to the conclusion that shatter cones are tensile fractures and might have formed during shock unloading after the passage of the shock wave through the target rocks

meteorite accumulations on mars abstract we have modeled single body meteoroid atmospheric entry speeds at mars and the effect of drag and ablation and identify a narrow range of small masses 10 50 g that should impact mars at survivable speeds the rate of oxidative weathering is much lower than that on earth so this small flux of meteorites could give rise to significant accumulations ca 5 10 2 to 5 10 5 meteorites greater than 10 g in mass per square kilometer given that extremely large numbers of meteorites may be present on mars future sample return missions should consider the real possibility that they may recover meteoritic material due to the low weathering rate meteorites may survive on the surface of mars for more than 10 9 years preserving a record of the temporal variability of the meteoroid flux and the compositional evolution of the meteoroid complex intact carbonaceous chondrites may also preserve organic compounds from degradation by ultraviolet radiation terrestrial meteorites may be present but would probably be sterile

spirit mars rover mission to the columbia hills gusev crater mission overview and selected results from the cumberland ridge to home plate this paper summarizes the spirit rover operations in the columbia hills of gusev crater from sols 513 to 1476 and provides an overview of selected findings that focus on synergistic use of the athena payload and comparisons to orbital data results include discovery of outcrops voltaire on husband hill that are interpreted to be altered impact melt deposits that incorporated local materials during emplacement evidence for extensive volcanic activity and aqueous alteration in the inner basin is also detailed including discovery and characterization of accretionary lapilli and formation of sulfate silica and hematite rich deposits use of spirit s data to understand the range of spectral signatures observed over the columbia hills by the mars reconnaissance orbiter s compact reconnaissance imaging spectrometer crism hyperspectral imager 0 4 4 m is summarized we show that crism spectra are controlled by the proportion of ferric rich dust to ferrous bearing igneous minerals exposed in ripples and other wind blown deposits the evidence for aqueous alteration derived from spirit s data is associated with outcrops that are too small to be detected from orbital observations or with materials exposed from the shallow subsurface during rover activities although orbital observations show many other locations on mars with evidence for minerals formed or altered in an aqueous environment spirit s data imply that the older crust of mars has been altered even more extensively than evident from orbital data this result greatly increases the potential that the surface or shallow subsurface was once a habitable regime

the new athena alpha particle x ray spectrometer for the mars exploration rovers 1 the new alpha particle x ray spectrometer apxs is part of the athena payload of the two mars exploration rovers mer the apxs sensor head is attached to the turret of the instrument deployment device idd of the rover the apxs is a very light weight instrument for determining the major and minor elemental composition of martian soils rocks and other geological materials at the mer landing sites the sensor head has simply to be docked by the idd on the surface of the selected sample x ray radiation excited by alpha particles and x rays of the radioactive sources is recorded by a high resolution x ray detector the x ray spectra show elements starting from sodium up to yttrium depending on their concentrations the backscattered alpha spectra measured by a ring of detectors provide additional data on carbon and oxygen by means of a proper calibration the elemental concentrations are derived together with data from the two other athena instruments mounted on the idd the samples under investigation can be fully characterized key apxs objectives are the determination of the chemistry of crustal rocks and soils and the examination of water related deposits sediments or evaporates using the rock abrasion tool attached to the idd issues of weathering can be addressed by measuring natural and abraded surfaces of rocks

constraints on martian differentiation processes from rbsr and smnd isotopic analyses of the basaltic shergottite que 94201 isotopic analyses of mineral leachate and whole rock fractions from the martian shergottite meteorite que 94201 yield rb sr and sm nd crystallization ages of 327 12 and 327 19 ma respectively these ages are concordant although the isochrons are defined by different fractions within the meteorite comparison of isotope dilution sm and nd data for the various que 94201 fractions with in situ ion microprobe data for que 94201 minerals from the literature demonstrate the presence of a leachable crustal component in the meteorite this component is likely to have been added to que 94201 by secondary alteration processes on mars and can affect the isochrons by selectively altering the isotopic systematics of the leachates and some of the mineral fractions initial 87sr 86sr of 0 701298 14 nd143 of 47 6 1 7 and whole rock nd142 of 0 92 0 11 indicate that que 94201 was derived from a source that was strongly depleted in 87rb 86sr and enriched in 147sm 144nd early in its history modeling demonstrates that the sm nd isotopic compositions of que 94201 can be produced by either four episodes of melting at 327 ma of cumulates crystallized from a magma ocean at 4 525 ga or five episodes of melting of an initially solid mars at 4 525 ga and 327 ma the neodymium isotopic systematics of que 94201 are not consistent with significant melting between 4 525 ga and 327 ma the estimated timing of these events is based on initial neodymium isotopic ratios and is independent of differentiation of the que 94201 parental magma rb sr based partial melting models are unable to reproduce the composition of que 94201 using the same model parameters employed in the sm nd based models implying a decoupling of rb sr and sm nd isotopic systems the initial decoupling of the two isotopic systems can be attributed to either cumulate or crust formation processes which are able to more efficiently fractionate rb from sr compared to sm from nd the fact that all martian meteorites analyzed so far define a rb sr whole rock isochron age of 4 5 ga suggests that virtually all rb was partitioned out of their mantle source regions and into either fractionated residual liquids trapped in the cumulate pile or into the crust at that time thus the martian mantle cumulates and restites are not expected to evolve past 87sr86sr of 0 700 and could not have been significantly enriched in incompatible elements by crustal recycling processes all martian meteorites have initial 87sr86sr values that are higher than 0 700 and are therefore likely to be produced by mixing between evolved crustal like and depleted mantle reservoirs the absence of crustal recycling processes on mars may preserve the geochemical evidence for decoupling of the rb sr and sm nd isotopic systems underscoring one of the fundamental differences between geologic processes on mars and the earth

oxygen isotope studies of achondrites abstract oxygen isotope abundances provide a powerful tool for recognizing genetic relationships among meteorites among the differentiated achondrites three isotopic groups are recognized l snc mars 2 earth and moon and 3 hed howardites eucrites diogenites the hed group also contains the mesosiderites main group pallasites and silicates from iiiab irons the angrites may be marginally resolvable from the hed group within each of these groups internal geologic processes give rise to isotopic variations along a slope 1 2 fractionation line as is well known for terrestrial materials variations of 17o from one planet to another are inherited from the inhomogeneities in the solar nebula as illustrated by the isotopic compositions of chondrites and their constituents among the undifferentiated achondrites five isotopic groups are found 1 aubrites 2 winonaites and iab iiicd irons 3 brachinites 4 acapulcoites and lodranites and 5 ureilites the isotopic compositions of aubrites coincide with the earth and moon and also with the enstatite chondrites these bodies apparently were derived from a common reservoir the isotopic composition of which was established at the chondrule scale by nebular processes isotopic similarities between chondrites and achondrites are seen only for the following instances 1 enstatite chondrites and aubrites 2 h chondrites and he irons and 3 l or ll chondrites and iva irons the isotopic data also support the following genetic associations 1 winonaites and iab iiicd irons 2 acapulcoites and lodranites and 3 ureilites and dark inclusions of c3 chondrites an attempt to reconcile the whole planet isotopic compositions of earth mars and the eucrite parent body with mixing models of their chemical compositions failed it is not possible to satisfy both the chemical and isotopic compositions of the terrestrial planets using known primitive solar system components

the role of undercooling in producing igneous zoning trends in pyroxenes and maskelynites among basaltic martian meteorites abstract pyroxene and maskelynite are major minerals in basaltic martian meteorites shergotty zagami eeta79001 and que94201 they are chemically zoned in both major and minor elements offering useful information on their crystallization history pigeonite and augite show two distinct textural occurrences of zoning patterns in shergotty and zagami pigeonite and augite are usually present as separate grains that are zoned from mg rich core to fe rich rim respectively both pigeonite and augite usually have homogeneous cores considered to be cumulus phases zagami pyroxenes are not zoned as extensively as those in shergotty but their mineralogy is quite similar on the other hand pigeonite and augite in eeta79001 and que94201 are both present in individual composite grains these pyroxenes are complexly zoned and typically the cores are mg rich pigeonites mantled by mg rich augite and the rims are fe rich pigeonite pyroxenes in lithology a of eeta79001 are small and show irregular zoning patterns but most of them show similar zoning patterns to lithology b of eeta79001 and que94201 maskelynite compositions also correspond to differences in pyroxene zoning maskelynites in shergotty and zagami are more alkali rich than those in eeta79001 and que94201 shergotty and zagami maskelynites apparently nucleated on pyroxene crystals and grew outward to lower an content into interstitial melts whereas eeta79001 and que94201 maskelynites have the most an rich portions in the centers of grains showing normal core to rim zoning feo in the maskelynite cores is different between shergotty and zagami 0 5 0 6 wt and eeta79001 and que94201 0 3 0 4 wt the lower fe content of eeta79001 and que94201 maskelynite cores reflects earlier crystallization of plagioclase al zoning in pyroxenes also marks the beginning of plagioclase crystallization decrease of the al ti ratios observed in al ti plots of pyroxenes further suggests plagioclase crystallization and the al ti distribution shows a clear difference between shergotty and zagami on one hand and eeta79001 and que94201 on the other such mineralogical differences of eeta79001 and que94201 from shergotty and zagami can be understood by undercooling of the magmas from which they have crystallized we believe that shergotty and zagami experienced only slight undercooling resulting initially in cotectic growth of pigeonite and augite later joined by plagioclase on the other hand eeta79001 and que94201 experienced significant undercooling of their melts and their crystallization sequence was pigeonite augite plagioclase and then fe rich pigeonite with each phase crystallizing metastably alone because the melt compositions did not follow the equilibrium phase boundaries lithology a of eeta79001 also experienced undercooling effects but they are not so extensive as in lithology b inasmuch as lithology a shows some features similar to shergotty and zagami all of these inferences concerning supercooling are consistent with field emission gun scanning electron microscopy feg sem observation of pyroxene microstructures if we consider that magmatic cooling rates are related to subsolidus cooling rates that is the pyroxene cores of shergotty and zagami have fine exsolution lamellae a few tens to a few hundreds nm whereas those of eeta79001 and que94201 do not contain such exsolution lamellae indicating faster cooling rate even at subsolidus

martian gases in an antarctic meteorite significant abundances of trapped argon krypton and xenon have been measured in shock altered phases of the achondritic meteorite elephant moraine 79001 from antarctica the relative elemental abundances the high ratios of argon 40 to argon 36 2000 and the high ratios of xenon 129 to xenon 132 2 0 of the trapped gas more closely resemble viking data for the martian atmosphere than data for noble gas components typically found in meteorites these findings support earlier suggestions made on the basis of geochemical evidence that shergottites and related rare meteorites may have originated from the planet mars

refined data of alpha proton x ray spectrometer analyses of soils and rocks at the mars pathfinder site implications for surface chemistry 1 an extensive recalibration of the alpha proton x ray spectrometer apxs was performed to improve the data evaluation of the mars pathfinder mpf rock and soil in situ measurements many samples and geostandards were measured with an mpf identical spare apxs under simulated martian atmospheric pressure and low night temperature conditions precise calibration curves for major and minor elements were obtained using an improved spectral evaluation method for the original mpf spectra refined and new elemental compositions of the mpf rocks and soils were derived however all initial conclusions about soils and rocks remained valid the mpf soil composition revealed the mafic nature of the surface as inferred from the results of viking 1 and 2 data however the mpf rocks reflect a felsic composition for all samples linear correlations of sulphur with all other elements were noticed reflecting the fact that the rocks were covered with varying degrees of soil which compared to the rocks is rich in sulphur extrapolating to low sulphur abundance 0 3 the composition of a soil free rock was calculated the mpf rock composition is high in si and k and low in mg and fe compared to the soil using elemental data from mpf and martian meteorites a global estimation of the martian crust composition was derived the crust is of basaltic nature with a high abundance of incompatible elements k rb nd u th and volatile elements s cl while carbonates are lower or absent

searching for the source regions of martian meteorites using mgs tes integrating martian meteorites into the global distribution of igneous materials on mars the objective of this study was to identify and map possible source regions for all 5 known martian meteorite lithologies basalt lherzolite clinopyroxenite orthopyroxenite and dunite using data from the mars global surveyor thermal emission spectrometer mgs tes we deconvolved the tes data set using laboratory spectra of 6 martian meteorites los angeles zagami alh a77005 nakhla alh 84001 and chassigny as end members along with atmospheric and surface spectra previously derived from tes data global maps 16 pixels degree of the distribution of each meteorite end member show that meteorite like compositions are not present at or above tes detectability limits over most of the planet s dust free regions however we have confidently identified local scale 100s1000s km2 concentrations of olivine and orthopyroxene bearing materials similar to alh a77005 chassigny and alh 84001 in nili fossae in and near ganges chasma in the argyre and hellas basin rims and in eos chasma nakhla like materials are identified near the detection limit throughout the eastern valles marineris region and portions of syrtis major basaltic shergottites were not detected in any spatially coherent areas at the scale of this study martian meteorite like lithologies represent only a minor portion of the dust free surface and thus are not representative of the bulk composition of the ancient crust meteorite like spectral signatures identified above tes detectability limits in more spatially restricted areas tens of km are targets of ongoing analysis

mossbauer mineralogy of rock soil and dust at gusev crater mars spirit s journey through weakly altered olivine basalt on the plains and pervasively altered basalt in the columbia hills 1 the mossbauer spectrometer on spirit measured the oxidation state of fe identified fe bearing phases and measured relative abundances of fe among those phases for surface materials on the plains and in the columbia hills of gusev crater eight fe bearing phases were identified olivine pyroxene ilmenite magnetite nanophase ferric oxide npox hematite goethite and a fe3 sulfate adirondack basaltic rocks on the plains are nearly unaltered fe3 fet px and minor npox and magnetite columbia hills basaltic rocks are nearly unaltered peace and backstay moderately altered woolypatch wishstone and keystone and pervasively altered e g clovis uchben watchtower keel and paros with fe3 fet 0 6 0 9 fe from pyroxene is greater than fe from olivine ol sometimes absent and fe2 from ol px is 40 49 and 9 24 for moderately and pervasively altered materials respectively ilmenite fe from ilm 3 6 is present in backstay wishstone keystone and related rocks along with magnetite fe from mt 10 15 remaining fe is present as npox hematite and goethite in variable proportions clovis has the highest goethite content fe from gt 40 goethite feooh is mineralogical evidence for aqueous processes because it has structural hydroxide and is formed under aqueous conditions relatively unaltered basaltic soils fe3 fet 0 3 occur throughout gusev crater 60 80 fe from ol px 10 30 from npox and 10 from mt pasorobles soil in the columbia hills has a unique occurrence of high concentrations of fe3 sulfate 65 of fe magnetite is identified as a strongly magnetic phase in martian soil and dust

athena microscopic imager investigation 1 the athena science payload on the mars exploration rovers mer includes the microscopic imager mi the mi is a fixed focus camera mounted on the end of an extendable instrument arm the instrument deployment device idd the mi was designed to acquire images at a spatial resolution of 30 microns pixel over a broad spectral range 400 700 nm the mi uses the same electronics design as the other mer cameras but has optics that yield a field of view of 31 31 mm across a 1024 1024 pixel ccd image the mi acquires images using only solar or skylight illumination of the target surface a contact sensor is used to place the mi slightly closer to the target surface than its best focus distance about 66 mm allowing concave surfaces to be imaged in good focus coarse focusing 2 mm precision is achieved by moving the idd away from a rock target after the contact sensor has been activated the mi optics are protected from the martian environment by a retractable dust cover the dust cover includes a kapton window that is tinted orange to restrict the spectral bandpass to 500 700 nm allowing color information to be obtained by taking images with the dust cover open and closed mi data will be used to place other mer instrument data in context and to aid in petrologic and geologic interpretations of rocks and soils on mars

alpha particle x ray spectrometer apxs results from gusev crater and calibration report 1 the chemical composition of rocks and soils on mars analyzed during the mars exploration rover spirit mission was determined by x ray analyses with the alpha particle x ray spectrometer apxs details of the data analysis method and the instrument calibration are presented measurements performed on mars to address geometry effects and background contributions are shown cross calibration measurements among several instrument sensors and sources are discussed an unintentional swap of the two flight instruments is evaluated new concentration data acquired during the first 470 sols of rover spirit in gusev crater are presented there are two geological regions the gusev plains and the columbia hills the plains contain soils that are very similar to previous landing sites on mars a meteoritic component in the soil is identified rocks in the plains revealed thin weathering rinds the underlying abraded rock was classified as primitive basalt one of these rocks contained significant br that is probably associated with vein filling material of different composition one of the trenches showed large subsurface enrichments of mg s and br disturbed soils and rocks in the columbia hills revealed different elemental compositions these rocks are significantly weathered and enriched in mobile elements such as p s cl or br even abraded rock surfaces have high br concentrations thus in contrast to the rocks and soils in the gusev plains the columbia hills material shows more significant evidence of ancient aqueous alteration

surface processes recorded by rocks and soils on meridiani planum mars microscopic imager observations during opportunity s first three extended missions the microscopic imager mi on the mars exploration rover opportunity has returned images of mars with higher resolution than any previous camera system allowing detailed petrographic and sedimentological studies of the rocks and soils at the meridiani planum landing site designed to simulate a geologist s hand lens the mi is mounted on opportunity s instrument arm and can resolve objects 0 1 mm across or larger this paper provides an overview of mi operations data calibration and analysis of mi data returned during the first 900 sols mars days of the opportunity landed mission analyses of opportunity mi data have helped to resolve major questions about the origin of observed textures and features these studies support eolian sediment transport rather than impact surge processes as the dominant depositional mechanism for burns formation strata mi stereo observations of a rock outcrop near the rim of erebus crater support the previous interpretation of similar sedimentary structures in eagle crater as being formed by surficial flow of liquid water well sorted spherules dominate ripple surfaces on the meridiani plains and the size of spherules between ripples decreases by about 1 mm from north to south along opportunity s traverse between endurance and erebus craters

overview of the spirit mars exploration rover mission to gusev crater landing site to backstay rock in the columbia hills spirit landed on the floor of gusev crater and conducted initial operations on soil covered rock strewn cratered plains underlain by olivine bearing basalts plains surface rocks are covered by wind blown dust and show evidence for surface enrichment of soluble species as vein and void filling materials and coatings the surface enrichment is the result of a minor amount of transport and deposition by aqueous processes layered granular deposits were discovered in the columbia hills with outcrops that tend to dip conformably with the topography the granular rocks are interpreted to be volcanic ash and or impact ejecta deposits that have been modified by aqueous fluids during and or after emplacement soils consist of basaltic deposits that are weakly cohesive relatively poorly sorted and covered by a veneer of wind blown dust the soils have been homogenized by wind transport over at least the several kilometer length scale traversed by the rover mobilization of soluble species has occurred within at least two soil deposits examined the presence of monolayers of coarse sand on wind blown bedforms together with even spacing of granule sized surface clasts suggests that some of the soil surfaces encountered by spirit have not been modified by wind for some time on the other hand dust deposits on the surface and rover deck have changed during the course of the mission detection of dust devils monitoring of the dust opacity and lower boundary layer and coordinated experiments with orbiters provided new insights into atmosphere surface dynamics

bounce rock a shergottite like basalt encountered at meridiani planum mars additional co authors thanasis economou steven p gorevan brian c hahn gostar klingelhofer timothy j mccoy harry y mcsween jr douglas w ming richard v morris daniel s rodionov steven w squyres heinrich wanke shawn p wright michael b wyatt albert s yen

in flight calibration and performance of the mars exploration rover panoramic camera pancam instruments 1 the mars exploration rover panoramic camera mer pancam instruments have acquired more than 60 000 high resolution multispectral stereoscopic images of soil rocks and sky at the gusev crater and meridiani planum landing sites since january 2004 these images combined with other mer data sets have enabled new discoveries about the composition mineralogy and geologic geochemical evolution of both sites one key to the success of pancam in contributing to the overall success of mer has been the development of a calibration pipeline that can quickly remove instrumental artifacts and generate both absolute radiance and relative reflectance images with high accuracy and precision in order to influence tactical rover driving and in situ sampling decisions this paper describes in detail the methods assumptions and models algorithms in the calibration pipeline developed for pancam images based on new measurements and refinements performed primarily from flight data acquired on mars major calibration steps include modeling and removal of detector bias signal active and readout region dark current electronic shutter smear and pixel to pixel responsivity flatfield variations pancam images are calibrated to radiance w m2 nm sr using refined preflight derived calibration coefficients or radiance factor i f using near in time measurements of the pancam calibration target and a model of aeolian dust deposition on the target as a function of time we are able to verify that the absolute radiance calibration of most pancam images is accurate to within about 10 or less and that the filter to filter and pixel to pixel precision of the calibrated relative reflectance data both based on measurements of the pancam calibration target are typically about 3 and 1 or less respectively examples are also presented of scientific applications made possible by the high fidelity of the calibrated pancam data these include 11 color visible to near ir spectral analysis calculation of true color and chromaticity values and generation of super resolution image data products this work represents a follow on and enhancement to the pancam preflight calibration process described by bell et al 2003

shock induced melting and vaporization of shatter cone surfaces evidence from the sudbury impact structure analytical scanning electron microscopy has been used to investigate the surface textures and compositions of newly exposed shatter cones from the 1 85 ga sudbury impact structure canada unusual surface microstructures are observed at the micron scale including silicate melt smears melt fibres and melt splats silicate and ni rich spherules up to 5 m in diameter adorn earlier formed surface features and we interpret these to be condensates formed due to shock induced vaporization of the shatter cone surfaces the development of striations on the shatter cones is attributed to shock related fracture and slip formation of melts and spherules indicates that the highest ranks of shock metamorphism stages iv and v were realized but only on a very localized scale shatter cone surfaces are therefore likely sites for the development of high pressure polymorphs and if the chemistry is appropriate fullerenes as such they may be equivalent to type a pseudotachylytes and shock veins in meteorites

the temporal and spatial quantification of holocene sediment dynamics in a meso scale catchment in northern bavaria germany the aufsess river catchment 97 km2 in northern bavaria germany is studied to establish a holocene sediment budget and to investigate the sediment dynamics since the early times of farming in the third millennium bce the temporal characterization of the sediment dynamics is based on an intensive dating program with 73 osl and 14 14c ages to estimate soil erosion and deposition colluvial and alluvial archives are investigated in the field by piling and trenching supported by laboratory analyses the sediment budget shows that 58 of these sediments are stored as colluvium in on and foot slope positions 9 are stored as alluvium in the floodplains and 33 are exported from the aufsess river catchment colluviation starts in the end neolithic c 3100 bce while first indicators of soil erosion derived alluviation is recorded c 2 3 ka later the pattern of sedimentation rates also displays differences between the colluvial and alluvial system with a distinct increase in the middle ages c 1000 c

vredefort shatter cones revisited shatter cones have been described from a number of circular and polygonal structures worldwide the origin of which has been alternatively ascribed to the impacts of large extraterrestrial projectiles or to catastrophic endogenic processes despite their association with enigmatic catastrophic processes the nature of shatter cones and the physics involved in their formation have not been comprehensively researched results of detailed field and laboratory studies of shatter cones from three areas in the collar of the vredefort dome in south africa are presented vredefort shatter cones are directly related to a widely displayed fracture phenomenon termed multiply striated joint sets msjs msjs are planar to curviplanar fractures occuring at spacings of 1 to several millimeters the joint sets have a fractal character when a new measurement protocol is used in the field involving study of all joint surfaces and all steps and striae exposed on these surfaces new information is gained on the genesis and significance of the msjs and on their relationship to striated conical fractures the internal constitution of a rock specimen with msjs was examined in detail by documenting the precise geometry of many fractures in a suite of parallel thin sections transecting the specimen the steps and striae on shatter cone surfaces have the characteristics of displacement fractures microfaults along which evidence of melting is observed shatter cone and msjs surfaces are often covered with glassy films we evaluate whether these fracture phenomena are linked to the formation of pseudotachylitic friction melt our field and petrographic observations can be interpreted as consistent with the generation of shatter cones msjs relatively late in the formation of the vredefort structure this scenario contrasts sharply with the widely held view that shatter cones are formed during the early compression phase of a shock event that affected horizontal strata

the rocks of gusev crater as viewed by the mini tes instrument 1 the miniature thermal emission spectrometer mini tes on board the mars exploration rover spirit is part of a payload designed to investigate whether a lake once existed in gusev crater mini tes has observed hundreds of rocks along the rover s traverse into the columbia hills yielding information on their distribution bulk mineralogy and the potential role of water at the site although dust in various forms produces contributions to the spectra we have established techniques for dealing with it all of the rocks encountered on the plains traverse from the lander to the base of the columbia hills share common spectral features consistent with an olivine rich basaltic rock known as adirondack class beginning at the base of the west spur of the columbia hills and across its length the rocks are spectrally distinct from the plains but can be grouped into a common type called clovis class these rocks some of which appear as in place outcrop are dominated by a component whose spectral character is consistent with unaltered basaltic glass despite evidence from other rover instruments for significant alteration the northwest flank of husband hill is covered in float rocks known as wishstone class with spectral features that can be attributed uniquely to plagioclase feldspar a phase that represents more than half of the bulk mineralogy rare exceptions are three classes of basaltic exotics found scattered across husband hill that may represent impact ejecta and or float derived from local intrusions within the hills the rare outcrops observed on husband hill display distinctive spectral characteristics the outcrop called peace shows a feature attributable to molecular bound water and the outcrop that hosts the rock called watchtower displays a dominant basaltic glass component despite evidence from the rover s payload for significant alteration of some of the rocks no unambiguous detection of crystalline phyllosilicates or other secondary silicates has been observed by mini tes the mineralogical results supplied by mini tes provide no clear evidence that a lake once existed in gusev crater

petrography and mineralogy of two basalts and olivine pyroxene spinel fragments in achondrite eeta79001 three lithologies occur in shocked achondrite eeta79001 a1 exotic irregular crystals and clusters of coarse grained olivine fo81 55 cao 0 2 cr2o3 0 06 nio 0 5 wt low ca pyroxene en82wo2 en58wo12 and low ti chromite cr2o3 59 feo 27 tio2 0 7 wt a2 basaltic host to a1 containing pyroxene mainly pigeonite en67wo12 en52wo13 maskelynite an61 55or0 7 high ti chromite some rimming low ti chromite whitlockite minor cl apatite ilmenite pyrrhotite and mesostasis and b a homogeneous basalt containing augite laths en40 50wo25 35 in a matrix of pigeohite augite maskelynite an62 56 or1 2 ulvospinelilmenite intergrowth whitlockite cl apatite and mesostasis mineral compositions indicate an oxidation state similar to that of shergottites lithology a1 represents an unmetamorphosed cumulate that was disrupted and partly resorbed by a basaltic magma incorporation of low ca magnesian pyroxenes and olivine increased the mg fe ratio of the basaltic magma responsible for a2 and resulted in abundant crystallization of pigeonite lithology b was generated from a distinct magma lacking fragments of a1 the parental spinel harzburgite of a1 was not annealed and is probably a near surface igneous cumulate from a shergottite type basalt ringwood and majorite were found in shock veins

petrology and chemistry of the basaltic shergottite north west africa 480 north west africa nwa 480 is a new martian meteorite of 28 g found in the moroccan sahara in november 2000 it consists mainly of large gray pyroxene crystals the largest grains are up to 5 mm in length and plagioclase converted to maskelynite excluding the melt pocket areas modal analyses indicate the following mineral proportions 72 vol pyroxenes extensively zoned 25 maskelynite 1 phosphates merrillite and chlorapatite 1 opaque oxides ilmenite ulvospinel and chromite and sulfides and 1 others such as silica and fayalite the compositional trend of nwa 480 pyroxenes is similar to that of queen alexandra range que 94201 but in nwa 480 the pyroxene cores are more mg rich en 77 en 65 maskelynites display a limited zoning an 42 50 ab 54 48 or 2 4 our observations suggest that nwa 480 formed from a melt with a low nuclei density at a slow cooling rate the texture was achieved via a single stage cooling where pyroxenes grew continuously a similar model was previously proposed for que 94201 by mcsween et al 1996 nwa 480 is an al poor ferroan basaltic rock and resembles zagami or shergotty for major elements and compatible trace element abundances the bulk rock analysis for oxygen isotopes yields delta 17 o 0 42parts per thousand a value in agreement at the high margin with those measured on other shergottites clayton and mayeda 1996 romanek et al 1998 franchi et al 1999 its ci normalized rare earth element pattern is similar to those of peridotitic shergottites such as allan hills alh a77005 suggesting that these shergottites shared a similar parent liquid or at least the same mantle source

mineralogy at meridiani planum from the mini tes experiment on the opportunity rover the miniature thermal emission spectrometer mini tes on opportunity investigated the mineral abundances and compositions of outcrops rocks and soils at meridiani planum coarse crystalline hematite and olivine rich basaltic sands were observed as predicted from orbital tes spectroscopy outcrops of aqueous origin are composed of 15 to 35 by volume magnesium and calcium sulfates a high silica component modeled as a combination of glass feldspar and sheet silicates 20 to 30 and hematite only minor jarosite is identified in mini tes spectra mini tes spectra show only a hematite signature in the millimeter sized spherules basaltic materials have more plagioclase than pyroxene contain olivine and are similar in inferred mineral composition to basalt mapped from orbit bounce rock is dominated by clinopyroxene and is close in inferred mineral composition to the basaltic martian meteorites bright wind streak material matches global dust waterlain rocks covered by unaltered basaltic sands suggest a change from an aqueous environment to one dominated by physical weathering

overview of the opportunity mars exploration rover mission to meridiani planum eagle crater to purgatory ripple the mars exploration rover opportunity touched down at meridiani planum in january 2004 and since then has been conducting observations with the athena science payload the rover has traversed more than 5 km carrying out the first outcrop scale investigation of sedimentary rocks on mars the rocks of meridiani planum are sandstones formed by eolian and aqueous reworking of sand grains that are composed of mixed fine grained siliciclastics and sulfates the siliciclastic fraction was produced by chemical alteration of a precursor basalt the sulfates are dominantly mg sulfates and also include ca sulfates and jarosite the stratigraphic section observed to date is dominated by eolian bedforms with subaqueous current ripples exposed near the top of the section after deposition interaction with groundwater produced a range of diagenetic features notably the hematite rich concretions known as blueberries the bedrock at meridiani is highly friable and has undergone substantial erosion by wind transported basaltic sand this sand along with concretions and concretion fragments eroded from the rock makes up a soil cover that thinly and discontinuously buries the bedrock the soil surface exhibits both ancient and active wind ripples that record past and present wind directions loose rocks on the soil surface are rare and include both impact ejecta and meteorites while opportunity s results show that liquid water was once present at meridiani planum below and occasionally at the surface the environmental conditions recorded were dominantly arid acidic and oxidizing and would have posed some significant challenges to the origin of life copyright 2006 by the american geophysical union

final chemical results from the mars pathfinder alpha proton x ray spectrometer 1 the calibrated pathfinder alpha proton x ray spectrometer apxs instrument is capable of measuring concentrations of all major and minor rock forming elements ranging from carbon through zirconium in atomic number therefore it is capable of constraining the petrology of the measured samples in particular the pathfinder data are the first in situ measurements of martian rocks and may be compared with previous remote sensing measurements as well as with the compositions of snc meteorites pathfinder soil and rock sample abundances from the alpha proton and x ray modes have been quantified the abundances suggest that 1 the rocks are covered with various amounts of soil 2 the soil free rocks on a volatile free basis have some element ratios similar to mars meteorites yet have different bulk chemistry indicative of more evolved rocks with higher silica abundances 3 the carbon and nitrogen contents are below detection limits and 4 the alpha mode oxygen reveals excess amounts of oxygen in some samples which is indicative of sample bound water contained within minerals or glasses in samples

timing and warmth of the last interglacial period new u series evidence from hawaii and bermuda and a new fossil compilation for north america abstract the timing and duration of the last interglacial period have been controversial with some studies suggesting a relatively short duration that is orbitally forced and others suggesting a long duration that is at most only partly related to orbital forcing new high precison thermal ionization mass spectrometric tims u series ages of last interglacial corals from hawaii and bermuda test these competing hypotheses waimanalo formation corals from slowly uplifting oahu hawaii range in age from 134 to 113 ka with most ages between 125 and 115 ka combined with published u series ages from nearby lanai the data suggest a long last interglacial period that may have occurred from 136 to at least 115 ka the results indicate that orbital forcing may not have been the only control on ice sheet growth and decay because sea level would have been high at times of relatively low northern hemisphere summer insolation on tectonically stable bermuda deposits from the 200 ka penultimate interglacial period 120 ka peak last interglacial period and 80 ka late last interglacial period high sea stands have been newly dated fossil corals on bermuda are derived from patch reefs that likely were catch up responses to sea level rise it is expected that u series ages of last interglacial corals on bermuda should overlap with but not be as old as the range of corals on oahu last interglacial corals on bermuda give a range of 125 113 ka which supports this hypothesis a large number of emergent marine deposits on hawaii bermuda and along coastal north america have now been dated to the last interglacial period both oahu and bermuda have marine invertebrate faunas with a number of extralimital southern species of mollusks suggesting warmer than present waters during the last interglacial period warmer waters are also suggested for last interglacial localities around most of north america from florida to canada and greenland and baja california to alaska these observations are consistent with similar warm water faunas of last interglacial age reported from japan the mediterranean basin and western australia it is likely that significant changes in ocean currents took place during the last interglacial period with a movement of relatively warm waters to higher latitudes than is the case today

athena mimos ii mossbauer spectrometer investigation 1 mossbauer spectroscopy is a powerful tool for quantitative mineralogical analysis of fe bearing materials the miniature mossbauer spectrometer mimos ii is a component of the athena science payload launched to mars in 2003 on both mars exploration rover missions the instrument has two major components 1 a rover based electronics board that contains power supplies a dedicated central processing unit memory and associated support electronics and 2 a sensor head that is mounted at the end of the instrument deployment device idd for placement of the instrument in physical contact with soil and rock the velocity transducer operates at a nominal frequency of 25 hz and is equipped with two 57co rh mossbauer sources the reference source 5 mci landed intensity reference target fe2o3 plus fe0 and pin diode detector are configured in transmission geometry and are internal to the instrument and used for its calibration the analysis mossbauer source 150 mci landed intensity irradiates martian surface materials with a beam diameter of 1 4 cm the backscatter radiation is measured by four pin diode detectors physical contact with surface materials is sensed with a switch activated contact plate the contact plate and reference target are instrumented with temperature sensors assuming 18 fe for martian surface materials experiment time is 6 12 hours during the night for quality spectra i e good counting statistics 1 2 hours is sufficient to identify and quantify the most abundant fe bearing phases data stored internal to the instrument for selectable return to earth include mossbauer and pulse height analysis spectra 512 and 256 channels respectively for each of the five detectors in up to 13 temperature intervals 65 mossbauer spectra engineering data for the velocity transducer and temperature measurements the total data volume is 150 kb the mass and power consumption are 500 g 400 g for the sensor head and 2 w respectively the scientific measurement objectives of the mossbauer investigation are to obtain for rock soil and dust 1 the mineralogical identification of iron bearing phases e g oxides silicates sulfides sulfates and carbonates 2 the quantitative measurement of the distribution of iron among these iron bearing phases e g the relative proportions of iron in olivine pyroxenes ilmenite and magnetite in a basalt 3 the quantitative measurement of the distribution of iron among its oxidation states e g fe2 fe3 and fe6 and 4 the characterization of the size distribution of magnetic particles special geologic targets of the mossbauer investigation are dust collected by the athena magnets and interior rock and soil surfaces exposed by the athena rock abrasion tool and by trenching with rover wheels

mineralogy of volcanic rocks in gusev crater mars reconciling mossbauer alpha particle x ray spectrometer and miniature thermal emission spectrometer spectra 1 complete sets of mineral abundances for relatively unaltered volcanic or volcaniclastic rocks in gusev crater have been determined by modeling mossbauer subspectral areas as mineral weight percentages and combining those percentages with the proportions of iron free minerals not detected by mossbauer normative plagioclase apatite and chromite as calculated from alpha particle x ray spectrometer apxs chemical analyses comparisons of synthetic thermal emission spectra calculated for these mineral modes with measured miniature thermal emission spectrometer mini tes spectra for the same rock classes show either good agreements or discrepancies that we attribute to sodic plagioclase compositions or unmodeled sulfate glass or pigeonite the normative compositions of olivine pyroxene and feldspar calculated from apxs data are consistent with spectroscopic constraints on mineral compositions systematic variations between olivine abundances in apxs norms which sample tens of micrometers depth and olivine proportions measured by mossbauer which sample hundreds of micrometers depth support the hypothesis that dissolution of olivine by acidic fluids has occurred on weathered rock surfaces