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

geochemical diversity of shergottite basalts mixing and fractionation and their relation to mars surface basalts the chemical compositions of shergottite meteorites basaltic rocks from mars provide a broad view of the origins and differentiation of these martian magmas the shergottite basalts are subdivided based on their al contents high al basalts al 5 wt are distinct from low al basalts and olivine phyric basalts both with al 4 5 wt abundance ratios of highly incompatible elements e g th la are comparable in all the shergottites abundances of less incompatible elements e g ti lu hf in olivine phyric and low al basalts correlate well with each other but the element abundance ratios are not constant this suggests mixing between components both depleted and enriched high al shergottites deviate from these trends consistent with silicate mineral fractionation the depleted component is similar to the yamato 980459 magma approximately 67 crystal fractionation of this magma would yield a melt with trace element abundances like que 94201 the enriched component is like the parent magma for nwa 1068 approximately 30 crystal fractionation from it would yield a melt with trace element abundances like the los angeles shergottite this component mixing is consistent with radiogenic isotope and oxygen fugacity data these mixing relations are consistent with the compositions of many of the gusev crater basalts analyzed on mars by the spirit rover although with only a few elements to compare other mars basalts fall off the mixing relations e g wishstone at gusev gale crater rocks their compositions imply that basalt source areas in mars include significant complexities that are not present in the source areas for the shergottite basalts

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

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

river profile controls on channel morphology debris flow disturbance and the spatial extent of salmonids in steep mountain streams received 29 december 2011 revised 5 september 2012 accepted 17 september 2012 published 27 october 2012 1 in the geologically and topographically diverse mountain ranges of the pacific northwest a broad scale means of prioritizing salmonid habitat conservation areas based on geomorphic process domains is examined we propose that steepness and concavity indices derived from the relation between drainage area and channel slope provide a means of identifying basins that express different reach scale morphologies fish habitat capacity and risk of episodic disturbance strongly concave river profiles that develop in mountainous terrain indicate that almost all of the relief in the drainage network occurs in headwater streams in these basins a large proportion of the channel network has low gradient morphologies which provide favorable habitat for many salmonid species the severity of pulse disturbances is also reduced because low gradient main stem channels inhibit debris flow conveyance and in these networks the distribution of fish can expand into tributaries allowing for a spatial spreading of risk in contrast rivers with poorly concave or steeper profiles have a greater abundance of high gradient reaches that limit the distribution of fish to a small portion of the channel network and facilitate debris flow passage the combined influence of a limited spatial distribution of fish and an increased risk of debris flows may cause populations in these basins to be less resilient to pulse disturbances a case example from the klamath mountains an area with broad variation in the steepness and concavity of river profiles was used to develop this approach and aid conservation planning for imperiled populations of anadromous salmonids

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

planetary science a chunk of ancient mars analysis of a meteorite found in northwest africa prosaically named nwa 7533 indicates that it is the first sample of the regolith or soil of mars and is derived from the earliest martian igneous crust yet identified see letter p 513 this paper identifies the nwa 7533 meteorite from northwest africa as the first sample of martian highlands rock in the meteorite collection munir humayun and co authors show that nwa 7533 has a composition indicative of a highlands breccia it also contains zircons more than 4 4 billion years old implying that early crustal differentiation on mars occurred in the first 100 million years of its history coeval with earliest crust formation on the moon and the earth

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 organic matter of interlayered carbonates and clays sediments trias lias sicily abstract in the ragusa basin southeastern sicily the noto late triassic and streppenosa early liassic formations considered as the main source rock of oil are composed of millimetric to metric recurrences of clays marls and carbonates together with a sedimentological and mineralogical description a characterization of the organic matter is performed at the same scale of investigation organic matter is analyzed in immature samples using rock eval technique and isolated kerogens generally in terms of total organic carbon the richest sediments toc 3 are the most clayey but very often in all the encountered lithotypes the hydrogen index reaches very high values hi up to 900 and the h c atomic ratio of kerogens ranges between 1 2 and 1 6 on the other hand the kerogens present a rather large distribution of o c atomic ratios and it is possible to define two poles of composition the kinetic parameters of cracking of representative organic samples of each pole are calculated by the optim method the variations of organic matter quantity and quality are discussed with respect to a typification of the sediments especially the laminites based upon observations performed with optical microscope and sem a tentative paleoenvironmental approach is proposed and the most favourable conditions for organic enrichment are outlined the general context is a local collapse of the triassic carbonate platform the highest petroleum potentials are neither associated to the algal sedimentary laminites of the noto formation nor to the basinal silty facies of the streppenosa formation but to the black shales intercalated within these facies and to the laminites rich in clay

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

forward modeling of the southern apennines forward kinematic modeling has been developed to reconstruct the successive geometries of geological sections the method is tested here on a geological section across the southern apeninnes where syntectonic neogene deposits are of help in determining the timing of the deformation that progressively affected more eastern parts of the apulian margin well known triassic and paleogene decollement levels induced thin skinned tectonics in the mesozoic and cenozoic sedimentary cover but the basement geometry is only poorly revealed by subsurface data two distinct hypotheses have been tested 1 thin skinned tectonics and 2 basement involved tectonics the shortening of the prism is estimated to be between 170 and 210 km whether or not the basement is involved in the imbricated stack of thrust sheets the results are discussed in the light of regional constraints i e regional flexure uplifts etc which favor basement involved structures at depth in addition to the effects of compression other phenomena affected the geometry of the prism and have to be taken into account because of the recent uplift of the belt the inner parts of the apenninic wedge have emerged and undergone erosion part of this eroded material has been simultaneously trapped in piggyback basins which record both the geometric and temporal evolution of the prism normal faulting also affected the western part of the southern apennines reactivating older thrust as detachment surfaces along which block rotation occurred

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

petrogenesis of a vitrophyre in the martian meteorite breccia nwa 7034 abstract northwest africa nwa 7034 and its paired meteorites nwa 7533 and nwa 7475 are the first recognized martian polymict breccia samples an unusual large subrounded clast in nwa 7034 shows a vitrophyric texture consisting of skeletal pyroxene and olivine with mesostasis this lithology has not been observed in the paired meteorites it crystallized under disequilibrium conditions as indicated by its olivine and pyroxene kdfe mg partitioning values as well as reversed order of crystallization and mineral compositions relative to those predicted by melts we report the highest bulk ni value 1020 ppm measured in any known martian meteorite or martian igneous rock suggesting an impact melt origin for the vitrophyre addition of 5 3 7 7 chondritic material to the target rock would account for the ni enrichment the bulk major and trace element abundances of the vitrophyre indicate that the protolith was not the host breccia nor any other martian meteorites however the clast is compositionally similar to humphrey rock in gusev crater analyzed by the spirit rover and to a texturally distinct group of clasts in the paired meteorite nwa 7533 thus we propose that the target rock was an igneous lithology similar to gusev basalts which was subsequently contaminated by a chondritic impactor

some sedimentological and geochemical characters of the late triassic noto formation source rock in the ragusa basin sicily in the ragusa basin southeastern sicily the late triassic noto formation is considered as the main oil source rock we provide a detailed description of the sedimentary facies determined from core samples and discuss geochemical results obtained for both kerogens and chloroform extractable hydrocarbons from samples where sedimentary organic matter is immature two main sedimentary sequences were encountered i layers of limestones and of marls or shales alternating at a metric scale and ii laminites having various types and carbonate contents the high petroleum potentials s2 up to 100 kg hc t rock are related to sedimentary lithologies that contain a minimum of clay two types of algal organic matter are probably mixed in the sediments studied these two types can be distinguished by the oxygen content they also do not have the same kinetic behavior in thermal evolution special attention has been paid to the possible use of bitumens and of pyrolysates obtained from kerogens for understanding organic facies bulk properties together with several biomarker distributions were examined through different facies but most of the parameters measured or computed are more clearly related to the maturity of the sequences analyzed rather than to the intrinsic nature of the in situ organic matter a modeling approach is proposed taking into account geological and geochemical data different situations of the noto source rock lead to different timings of oil formation the importance of source rock heterogeneities at different scales in basin evaluation is underlined

constraints on the depth and thermal vigor of melting in the martian mantle studies of rocks in gale crater and clasts within the martian meteorite breccia northwest africa nwa 7034 and paired stones have expanded our knowledge of the diversity of igneous rocks that make up the martian crust beyond those compositions exhibited in the meteorite collection or analyzed at any other landing site therefore the magmas that gave rise to these rocks may have been generated at significantly different conditions in the martian mantle than those derived from previously studied rocks here we build upon our previous models of basalt formation based on rocks analyzed in gusev crater and meridiani planum to the new models of basalt formation for compositions from gale crater and a clast in meteorite nwa 7034 estimates for the mantle potential temperature tp based on noachian age rock analyses in gale crater gusev crater and bounce rock in meridiani planum and a vitrophyre clast in nwa 7034 are within error which suggests that the calculated average tp of 1450 70 c may represent an average global mantle temperature during the noachian the tp estimates for the hesperian and amazonian based on orbital analyses of the chemistry of the crust are lower in temperature than our estimates for the noachian which is consistent with simple convective cooling of the interior of mars however the tp estimates from the young meteorites are significantly higher than the estimates based on surface chemistry and are consistent with localized hot spot melting and not heating up of the interior

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

petrological constraints on the density of the martian crust new insights into the chemistry of the martian crust have been made available since the derivation of crustal thickness maps from mars global surveyor gravity and topography data that used a conservative range of density values 2700 3100 kg m3 a new range of crustal density values is calculated from the major element chemistry of martian meteorites 3100 3700 kg m3 igneous rocks at gusev crater 3100 3600 kg m3 and from the surface concentration of fe al ca si and k measured by the gamma ray spectrometer on board mars odyssey 3250 3450 kg m3 in addition the density of mineral assemblages resulting from low pressure crystallization of primary melts of the primitive mantle are estimated for plausible conditions of partial melting corresponding to the noachian to amazonian periods 3100 3300 kg m3 despite the differences between these approaches the results are all consistent with an average density above 3100 kg m3 for those materials that are close to the surface the density may be compatible with the measured mass of mars and the moment of inertia factor but only if the average crustal thickness is thicker than previously thought approaching 100 km a thicker crust implies that crustal delamination and recycling could be possible and may even control its thickness globally or locally alternatively and considering that geoid to topography ratios argue against such a thick crust for the highlands our results suggest the existence of a buried felsic or anorthositic component in the southern hemisphere of mars

petrology on mars petrologic investigations of martian rocks have been accomplished by mineralogical geochemical and textural analyses from mars rovers with geologic context provided by orbiters and by laboratory analyses of martian meteorites igneous rocks are primarily lavas and volcaniclastic rocks of basaltic composition and ultramafic cumulates alkaline rocks are common in ancient terranes and tholeiitic rocks occur in younger terranes suggesting global magmatic evolution relatively uncommon feldspathic rocks represent the ultimate fractionation products and granitic rocks are unknown sedimentary rocks are of both clastic mudstone sandstone conglomerate all containing significant igneous detritus and chemical evaporitic sulfate and less common carbonate origin high silica sediments formed by hydrothermal activity sediments on mars formed from different protoliths and were weathered under different environmental conditions from terrestrial sediments metamorphic rocks have only been inferred from orbital remote sensing measurements metabasalt and serpentinite have mineral assemblages consistent with those predicted from low pressure phase equilibria and likely formed in geothermal systems shock effects are common in martian meteorites and impact breccias are probably widespread in the planet s crustal rocks the martian rock cycle during early periods was similar in many respects to that of earth however without plate tectonics mars did not experience the thermal metamorphism and flux melting associated with subduction nor deposition in subsided basins and rapid erosion resulting from tectonic uplift the rock cycle during more recent time has been truncated by desiccation of the planet s surface and a lower geothermal gradient in its interior the petrology of mars is intriguingly different from earth but the tried and true methods of petrography and geochemistry are clearly translatable to another world

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

pancam multispectral imaging results from the opportunity rover at meridiani planum panoramic camera pancam images from meridiani planum reveal a low albedo generally flat and relatively rock free surface within and around impact craters and fractures laminated outcrop rocks with higher albedo are observed fine grained materials include dark sand bright ferric iron rich dust angular rock clasts and millimeter size spheroidal granules that are eroding out of the laminated rocks spectra of sand clasts and one dark plains rock are consistent with mafic silicates such as pyroxene and olivine spectra of both the spherules and the laminated outcrop materials indicate the presence of crystalline ferric oxides or oxyhydroxides atmospheric observations show a steady decline in dust opacity during the mission astronomical observations captured solar transits by phobos and deimos and time lapse observations of sunsets

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

diverse lithologies and alteration events on the rim of noachian aged endeavour crater meridiani planum mars in situ compositional evidence we report the results of geological studies by the opportunity mars rover on the endeavour crater rim four major units occur in the region oldest to youngest the matijevic shoemaker grasberg and burns formations the matijevic formation consisting of fine grained clastic sediments is the only pre endeavour impact unit and might be part of the noachian etched units of meridiani planum the shoemaker formation is a heterogeneous polymict impact breccia its lowermost member incorporates material eroded from the underlying matijevic formation the shoemaker formation is a close analog to the bunte breccia of the ries crater although the average clast sizes are substantially larger in the latter the grasberg formation is a thin fine grained homogeneous sediment unconformably overlying the shoemaker formation and likely formed as an airfall deposit of unknown areal extent the burns formation sandstone overlies the grasberg but compositions of the two units are distinct there is no evidence that the grasberg formation is a fine grained subfacies of the burns formation the rocks along the endeavour crater rim were affected by at least four episodes of alteration in the noachian and early hesperian i vein formation and alteration of preimpact matijevic formation rocks ii low water rock alteration along the disconformity between the matijevic and shoemaker formations iii alteration of the shoemaker formation along fracture zones and iv differential mobilization of fe and mn and caso 4 vein formation in the grasberg and shoemaker formations episodes ii and iii possibly occurred together but i and iv are distinct from either of these

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

visible and near infrared multispectral analysis of geochemically measured rock fragments at the opportunity landing site in meridiani planum 1 we have used visible and near infrared panoramic camera pancam spectral data acquired by the opportunity rover to analyze 15 rock fragments at the meridiani planum landing site these spectral results were then compared to geochemistry measurements made by the in situ instruments mossbauer mb and alpha particle x ray spectrometer apxs to determine the feasibility of mineralogic characterization from pancam data our results suggest that dust and alteration rinds coat many rock fragments which limits our ability to adequately measure the mineralogy of some rocks from pancam spectra relative to the different field of view and penetration depths of mb and apxs viewing and lighting geometry along with sampling size also complicate the spectral characterization of the rocks rock fragments with the same geochemistry of sulfate rich outcrops have similar spectra although the sulfate rich composition cannot be ascertained based upon pancam spectra alone feni meteorites have spectral characteristics particularly ferric oxide coatings that generally differentiate them from other rocks at the landing site stony meteorites and impact fragments with unknown compositions have a diverse range of spectral properties and are not well constrained nor diagnostic in pancam data bounce rock with its unique basalt composition is easily differentiated in the pancam data from all other rock types at meridiani planum our pancam analyses of small pebbles adjacent to these 15 rock fragments suggests that other rock types may exist at the landing site but have not yet been geochemically measured

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

thermal history of sedimentary basins maturation indices and kinetics of oil and gas generation temperature is the most sensitive parameter in hydrocarbon generation thus reconstruction of temperature history is essential when evaluating petroleum prospects no measurable parameter can be directly converted to paleotemperature maturation indices such as vitrinite reflectance tmax from rock eval pyrolysis spore coloration thermal alteration index tai or concentration of biological markers offer an indirect approach all these indices are a function of the thermal history through rather complex kinetics frequently influenced by the type of organic matter their significance and validity are reviewed besides the problems of identification e g vitrinite and interlaboratory calibration it is important to simultaneously interpret kerogen type and maturation and to avoid difficult conversions from one index to another geodynamic models where structural and thermal histories are connected are another approach to temper ture reconstruction which could be calibrated against the present distribution of temperature and the present value of maturation indices kinetics of kerogen decomposition controls the amount and composition of hydrocarbons generated an empirical time temperature index tti originally introduced by lopatin does not allow such a quantitative evaluation due to several limitations no provision for different types of kerogen and different rates of reactions poor calibration on vitrinite reflectance it is of limited interest unless one has no access to a desk top computer kinetic models based on a specific calibration made on actual source rock samples can simulate the evolution of all types of organic matter and can provide a quantitative evaluation of oil and gas generated examples from the jurassic source rocks of the paris basin monterey formation of california green river shales of utah paleozoic source eds of the algerian sahara and miocene rocks of the mahakam delta indonesia illustrate various aspects of the discussion geological geochemical models are the most efficient way to integrate geological seismic and geochemical data and they should greatly help to reduce the risk in exploration

hydrocarbon generation in southern sicily a three dimensional computer aided basin modeling study abstract a three dimensional computer aided basin modeling study was performed in order to determine timing and spatial distribution of hydrocarbon hc generation in southern sicily the entire information concerning the geologic evoulution such as age thickness lithology and porosity of individual sedimentary layers estimates on paleobathymetry and sediment water interface temperatures initial physical and thermal properties of various lithologies heat flow and particularly type and amount of organic matter was used to construct a conceptual model and to determine the necessary input parameters the simulation of basin evolution resulted in a very detailed and comprehensive definition of the thermal history of the study area subsequently the thermal history of the noto source rock throughout the entire study area was used to define the hc generation potential the latter was not elaborated with the help of maturity data but utilizing a kinetic model the simulation results showed that the main phase of oil generation was during the last 5 ma when a foredeep basin was created in front of the overthrust sheets here very thick pliocene pleistocene sediments were deposited the rapid burial caused a quick temperature increase i e high heating rates which initiated the onset of oil generation at relatively low maturity levels furthermore it also caused an early expulsion of immature heavy oil from the noto source rock

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

two years at meridiani planum results from the opportunity rover the mars exploration rover opportunity has spent more than 2 years exploring meridiani planum traveling 8 kilometers and detecting features that reveal ancient environmental conditions these include well developed festoon trough cross lamination formed in flowing liquid water strata with smaller and more abundant hematite rich concretions than those seen previously possible relict hopper crystals that might reflect the formation of halite thick weathering rinds on rock surfaces resistant fracture fills and networks of polygonal fractures likely caused by dehydration of sulfate salts chemical variations with depth show that the siliciclastic fraction of outcrop rock has undergone substantial chemical alteration from a precursor basaltic composition observations from microscopic to orbital scales indicate that ancient meridiani once had abundant acidic groundwater arid and oxidizing surface conditions and occasional liquid flow on the surface

sedimentation distribution and diagenesis of organic matter in a recent carbonate environment abu dhabi u a e abstract in the modern hypersaline carbonate lagoon and sabkha sedimentary environments of abu dhabi united arab emirates three types of organic matter originate respectively from microbial mat avicennia mangrove and halodule lagoonal seagrass the study of recent sedimentary processes and cross sections through the sabkha sediments lead to the definition of organo sedimentary facies based on geochemical and sedimentological criteria this permits the construction of an organo sedimentary sequence which expresses the holocene sedimentary record involving a transgressive and a regressive sequence the various organic facies occur in both sequences heterogeneity within the individual organic facies reflects several factors including sedimentation dynamics mineral matrix oxidation and reduction and selective organic and mineral diagenesis these parameters are discussed in terms of depositional environment and location within the organo sedimentary sequence changes in distribution quantity and preservation potential of the buried organic matter are discussed in terms of sea level changes and sedimentary accretion rates

santorini volcano as a potential martian analogue the balos cove basalts the interpretation of geologic processes on mars from sparse meteorite remote sensing and rover data is influenced by knowledge gained from well characterized terrestrial analogues this calls for detailed study of candidate terrestrial analogues and comparison of their observable features to those encountered on the surface of mars we evaluated the mineralogical geochemical and physical properties of the balos cove basalts bcb from the island of santorini and compared them to martian meteorites mars rover surface measurements and other verified martian analogues obtained from the international space analogue rockstore isar twenty rock samples were collected from the balos cove area based on their freshness integrity and basaltic appearance in the field optical microscopy of bcb revealed a pilotaxitic to trachytic texture with olivine and clinopyroxenephenocrysts in a fine groundmass of olivine clinopyroxene plagioclase magnetite and devitrified glass all major minerals show normal zoning including calcic plagioclase an 78 85 at the core and an 60 76 at the rim augite en 36 48 wo 41 44 fs 11 21 and olivine fo 74 88 the dominant bands in the infrared attenuated total reflectance ir atr spectra from bcb can be assigned to olivine 875 cm 1 calcic plagioclase 1130 cm 1 and augite 970 cm 1 the whole rock chemical compositions and mineralogy of the bcb are similar to published analyses of typical olivine phyric shergottites and basalts and basaltic materials analyzed in gusev and gale craters on mars bcb porosity is in the range of 7 15 and is similar to the porosities of the isar samples although no terrestrial rock is ever a perfect match to martian compositions the differences in mineralogy and geochemistry between bcb and some classes of martian samples are relatively subtle and the basalts of santorini are as close a match as other accepted mars basalt analogues the santorini site offers excellent field logistics that together with the petrology of the outcrop makes it a valuable locality for testing and calibration deployments field training and other activities related to current and future mars exploration

jarosite and hematite at meridiani planum from opportunity s mossbauer spectrometer mossbauer spectra measured by the opportunity rover revealed four mineralogical components in meridiani planum at eagle crater jarosite and hematite rich outcrop hematite rich soil olivine bearing basaltic soil and a pyroxene bearing basaltic rock bounce rock spherules interpreted to be concretions are hematite rich and dispersed throughout the outcrop hematitic soils both within and outside eagle crater are dominated by spherules and their fragments olivine bearing basaltic soil is present throughout the region bounce rock is probably an impact erratic because jarosite is a hydroxide sulfate mineral its presence at meridiani planum is mineralogical evidence for aqueous processes on mars probably under acid sulfate conditions

thermal and compositional evolution of the martian mantle effects of phase transitions and melting abstract we present new numerical models for the thermochemical evolution of the mantle of mars over the past 4 gy specifically we have developed a parameterized model of composition and thermoelastic properties of mantle material and combined it with a two dimensional anelastic compressible convection and melting algorithm in a spherical annulus geometry these models include a detailed treatment of the effects of solid solid phase transitions and of compositional changes that accompany generation and removal of mantle partial melt during magmatism among other questions we examine if a perovskite ferropericlase layer pv fp exists at the base of the martian mantle if long lived plumes can explain the volcanic provinces under which circumstances mars may still be volcanically active and how iron and radionuclide rich mars is results of the models are compared with geophysical and chemical observations from spacecraft and information from martian meteorites most models yield crustal thicknesses between 75 and 90 km ancient depths for the curie temperatures of possible magnetic carriers that include the entire crust and mechanical lithosphere thicknesses that increased from less than 100 km in the noachian to 200 250 km now generally models with a large core mg 0 75 and radionuclide contents derived from those suggested by wanke and dreibus chemistry and accretion history of mars philos trans r soc lond a 349 285 293 1994 tend to explain observations best but none of the models reproduces the full range of concentrations found in martian meteorites thus implicitly supporting the idea that ancient chemical heterogeneities survive in the mantle only a subset of the models develops a pattern of mantle convection that evolves towards two or three large long lived plumes and it takes at least 2 gy before this stage is reached whereas models with a larger number of plumes or with plumes that are less stationary are more common as tharsis and probably elysium are older than 2 5 3 gy either model assumptions more complex than those made in this study or a dynamical mode different from low degree convection with long lived large plumes is required to explain these major volcanic provinces the effect of the mid mantle phase transitions on mantle dynamics is rather weak so that whole mantle convection prevails however a basal pv fp layer would form a dynamically separate unit and decouple the mantle and core to some extent

combining meteorites and missions to explore mars laboratory studies of meteorites and robotic exploration of mars reveal scant atmosphere no evidence of plate tectonics past evidence for abundant water and a protracted igneous evolution despite indirect hints direct evidence of a martian origin came with the discovery of trapped atmospheric gases in one meteorite since then the study of martian meteorites and findings from missions have been linked although the meteorite source locations are unknown impact ejection modeling and spectral mapping of mars suggest derivation from small craters in terrains of amazonian to hesperian age whereas most martian meteorites are young 4 5 ga and formation of enriched and depleted reservoirs however the history inferred from martian meteorites conflicts with results from recent mars missions calling into doubt whether the igneous histor y inferred from the meteorites is applicable to mars as a whole allan hills 84001 dates to 4 09 ga and contains fluid deposited carbonates accompanying debate about the mechanism and temperature of origin of the carbonates came several features suggestive of past microbial life in the carbonates although highly disputed the suggestion spurred interest in habitable extreme environments on earth and throughout the solar system a flotilla of subsequent spacecraft has redefined mars from a volcanic planet to a hydrologically active planet that may have harbored life understanding the history and habitability of mars depends on understanding the coupling of the atmosphere surface and subsurface sample return that brings back direct evidence from these diverse reservoirs is essential

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 viscosity of planetary tholeiitic melts a configurational entropy model abstract the viscosity of silicate melts is a fundamental physical property controlling mass transfer in magmatic systems viscosity can span many orders of magnitude strongly depending on temperature and composition several models are available that describe this dependency for terrestrial melts quite well planetary basaltic lavas however are distinctly different in composition being dominantly alkali poor iron rich and or highly magnesian we measured the viscosity of 20 anhydrous tholeiitic melts of which 15 represent known or estimated surface compositions of mars mercury the moon io and vesta by concentric cylinder and parallel plate viscometry the planetary basalts span a viscosity range of 2 orders of magnitude at liquidus temperatures and 4 orders of magnitude near the glass transition and can be more or less viscous than terrestrial lavas we find that current models under and overestimate superliquidus viscosities by up to 2 orders of magnitude for these compositions and deviate even more strongly from measured viscosities toward the glass transition we used the adam gibbs theory a g to relate viscosity to absolute temperature t and the configurational entropy of the system at that temperature sconf which is in the form of log a e b e ts conf heat capacities cp for glasses and liquids of our investigated compositions were calculated via available literature models we show that the a g theory is applicable to model the viscosity of individual complex tholeiitic melts containing 10 or more major oxides as well or better than the commonly used empirical equations we successfully modeled the global viscosity data set using a constant ae of 3 34 0 22 log units and 12 adjustable sub parameters which capture the compositional and temperature dependence on melt viscosity seven sub parameters account for the compositional dependence of be and 5 for sconf our model reproduces the 496 measured viscosity data points with a 1 root mean square deviation rmsd of 0 12 log units across 13 orders of measured melt viscosity the model performed well in predicting the viscosity of lunar and martian melts not used in calibration and should be used to calculate lava flow velocities and fluxes for anhydrous basaltic volcanism on other moons and planets

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

rock abrasion tool mars exploration rover mission 1 the rock abrasion tool rat is an integral part of the athena science payload serving primarily as the geologist s rock hammer the rat will expose fresh surfaces of martian rocks to other instruments on the payload the rat also brushes dust and debris from an excavated hole or unaltered rocks to accomplish these tasks autonomously the rat a sophisticated 3 axis precision controlled device was designed data products derived from rat telemetry enable the rat to also act as an important rock physical properties science instrument the returned rat grinding and penetration rate data will be inverted and compared to a rock library on the earth the design is also very compact and lightweight the rat is contained within a cylinder 128 mm long and 85 mm in diameter and has a mass of 687 g

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

basaltic rocks analyzed by the spirit rover in gusev crater the spirit landing site in gusev crater on mars contains dark fine grained vesicular rocks interpreted as lavas pancam and mini thermal emission spectrometer mini tes spectra suggest that all of these rocks are similar but have variable coatings and dust mantles magnified images of brushed and abraded rock surfaces show alteration rinds and veins rock interiors contain 25 megacrysts chemical analyses of rocks by the alpha particle x ray spectrometer are consistent with picritic basalts containing normative olivine pyroxenes plagioclase and accessory feti oxides mossbauer pancam and mini tes spectra confirm the presence of olivine magnetite and probably pyroxene these basalts extend the known range of rock compositions composing the martian crust

unique meteorite from early amazonian mars water rich basaltic breccia northwest africa 7034 we report data on the martian meteorite northwest africa nwa 7034 which shares some petrologic and geochemical characteristics with known martian meteorites of the snc i e shergottite nakhlite and chassignite group but also has some unique characteristics that would exclude it from that group nwa 7034 is a geochemically enriched crustal rock compositionally similar to basalts and average martian crust measured by recent rover and orbiter missions it formed 2 089 0 081 billion years ago during the early amazonian epoch in mars9 geologic history nwa 7034 has an order of magnitude more indigenous water than most snc meteorites with up to 6000 parts per million extraterrestrial h2o released during stepped heating it also has bulk oxygen isotope values of 17o 0 58 0 05 per mil and a heat released water oxygen isotope average value of 17o 0 330 0 011 per mil suggesting the existence of multiple oxygen reservoirs on mars

the opportunity rover s athena science investigation at meridiani planum mars the mars exploration rover opportunity has investigated the landing site in eagle crater and the nearby plains within meridiani planum the soils consist of fine grained basaltic sand and a surface lag of hematite rich spherules spherule fragments and other granules wind ripples are common underlying the thin soil layer and exposed within small impact craters and troughs are flat lying sedimentary rocks these rocks are finely laminated are rich in sulfur and contain abundant sulfate salts small scale cross lamination in some locations provides evidence for deposition in flowing liquid water we interpret the rocks to be a mixture of chemical and siliciclastic sediments formed by episodic inundation by shallow surface water followed by evaporation exposure and desiccation hematite rich spherules are embedded in the rock and eroding from them we interpret these spherules to be concretions formed by postdepositional diagenesis again involving liquid water

mossbauer mineralogy of rock soil and dust at meridiani planum mars opportunity s journey across sulfate rich outcrop basaltic sand and dust and hematite lag deposits additonal co authors p gutlich e kankeleit t mccoy dw mittlefehldt f renz me schmidt b zubkov sw squyres re arvidson

geochemistry of martian basalts with constraints on magma genesis abstract over the past decade our knowledge of the geochemical and mineralogical diversity of martian rocks has greatly increased rocks on the surface of mars are older than most martian meteorites and have a wider range in bulk chemistry higher sio 2 higher total alkalis and lower mgo contents recent martian meteorite discoveries nwa 7034 nwa 7635 and nwa 8159 are also significantly older than the shergottites and nwa 7034 contains clasts which have a similar range in chemistry of the surface basalts in this invited review i summarize what is known about the bulk chemistry major elements of martian igneous rocks and use the chemistry to constrain the formation conditions in the interior and how these conditions have changed through time the basalts at gale crater are consistent with forming from a metasomatized mantle source which affected not only the chemistry of the basalts but also the formation conditions basalts at gusev crater bounce rock at meridiani planum and those basalts not affected by metasomatism like those at gale crater have a mantle potential temperature of 1450 c for the noachian conversely martian shergottites have a much higher mantle potential temperature 1745 c which has always been problematic to explain for such young rocks new formation conditions calculations are consistent with previous models of formation by a hot mantle plume but solve the pressure of formation paradox from the previous model combining the calculations for mantle potential temperature with previous estimates for grs measurements of surface volcanics from the hesperian and amazonian i calculate a baseline cooling curve and mantle melting conditions for the martian interior through time

the spirit rover s athena science investigation at gusev crater mars the mars exploration rover spirit and its athena science payload have been used to investigate a landing site in gusev crater gusev is hypothesized to be the site of a former lake but no clear evidence for lacustrine sedimentation has been found to date instead the dominant lithology is basalt and the dominant geologic processes are impact events and eolian transport many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration any lacustrine sediments that may exist at this location within gusev apparently have been buried by lavas that have undergone subsequent impact disruption

mars exploration rover engineering cameras 1 nasa s mars exploration rover mer mission will place a total of 20 cameras 10 per rover onto the surface of mars in early 2004 fourteen of the 20 cameras are designated as engineering cameras and will support the operation of the vehicles on the martian surface images returned from the engineering cameras will also be of significant importance to the scientific community for investigative studies of rock and soil morphology the navigation cameras navcams two per rover are a mast mounted stereo pair each with a 45 square field of view fov and an angular resolution of 0 82 milliradians per pixel mrad pixel the hazard avoidance cameras hazcams four per rover are a body mounted front and rear facing set of stereo pairs each with a 124 square fov and an angular resolution of 2 1 mrad pixel the descent camera one per rover mounted to the lander has a 45 square fov and will return images with spatial resolutions of 4 m pixel all of the engineering cameras utilize broadband visible filters and 1024 1024 pixel detectors

re os dating of maltenes and asphaltenes within single samples of crude oil abstract re os geochronology of oil may constrain the timing of oil formation and improve oil source and oil oil correlations typically asphaltene asph the heaviest and most re os rich oil fraction from multiple oils within an oil field or a larger petroleum system are analyzed to obtain sufficient spread in re os isotopic ratios a mathematical necessity for precise re os isochrons here we offer a new approach for re os geochronology of oil based on isotopic analyses of different fractions within a single sample of crude oil we studied three oils from the gela oil field southern sicily italy recovered from triassic jurassic stratigraphic intervals streppenosa noto and sciacca formations within the gela 1 well asph insoluble in n alkane and maltene malt soluble in n alkane fractions of oil were separated using n pentane n hexane n heptane and n decane solvents the asph contents of the sciacca and noto oils 26 33 wt are notably higher compared to the streppenosa oil 7 12 wt asph we present an optimized re os procedure with sample digestion in a high pressure asher followed by isotopic measurements using negative thermal ionization mass spectrometry very high metal contents of gela oils allowed acquisition of precise re os data systematic variations between the type of solvent used for asph precipitation and the asph content of the oil also known from the literature and the re os contents of the asph and malt fractions first observed in this study provide important practical applications for re os analyses of oil most re and os 96 98 in the noto oil are hosted in the asph fraction in contrast a significant portion of re and os 33 34 is stored in the malt fraction of the lighter but heavily biodegraded streppenosa oil collectively our new data on alkane distribution hopane and sterane biomarkers major and trace element contents and re os concentrations and isotopic ratios of the oils and their fractions support the presence of two oil families streppenosa oil a heavily biodegraded oil generated at an early stage of thermal maturation from a shaly source rock is clearly distinct from the noto and sciacca oils both generated at peak maturation from a carbonate source rock with no subsequent biodegradation two re os ages were obtained crude oil and asph from noto and sciacca oil yield a model 1 isochron age of 27 5 4 6 ma with an initial 187 os 188 os of 3 89 0 43 mswd 1 6 n 19 we interpret this oligocene age as the time of initial oil generation that was probably related to the onset of regional collisional tectonics in southern sicily asph and crude oil from the streppenosa oil yield scattered data perhaps related to effects of biodegradation streppenosa malt yield a model 1 age of 200 0 5 2 ma and initial 187 os 188 os of 1 39 0 11 mswd 0 52 n 4 this age and initial os isotopic composition are consistent with rapid oil generation shortly after late triassic source rock formation perhaps driven by magmatic related heating here we document a potentially powerful geochronological tool that can be applied to single samples of crude oil within each oil the 187 os 188 os and most of the 187 re 188 os ratios in the malt fractions are lower than in the corresponding asph fractions crude oils being physical mixtures of asph and malt have intermediate re os isotopic ratios hence the needed spread in data points for a re os isochron is obtained by analyzing components of a single crude oil this approach eliminates pitfalls in interpretation of re os data from multiple oils with possibly different generation migration or reservoir modification history

localization and physical property experiments conducted by opportunity at meridiani planum the location of the opportunity landing site was determined to better than 10 m absolute accuracy from analyses of radio tracking data we determined rover locations during traverses with an error as small as several centimeters using engineering telemetry and overlapping images topographic profiles generated from rover data show that the plains are very smooth from meter to centimeter length scales consistent with analyses of orbital observations solar cell output decreased because of the deposition of airborne dust on the panels the lack of dust covered surfaces on meridiani planum indicates that high velocity winds must remove this material on a continuing basis the low mechanical strength of the evaporitic rocks as determined from grinding experiments and the abundance of coarse grained surface particles argue for differential erosion of meridiani planum

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

mars exploration rover athena panoramic camera pancam investigation 1 the panoramic camera pancam investigation is part of the athena science payload launched to mars in 2003 on nasa s twin mars exploration rover mer missions the scientific goals of the pancam investigation are to assess the high resolution morphology topography and geologic context of each mer landing site to obtain color images to constrain the mineralogic photometric and physical properties of surface materials and to determine dust and aerosol opacity and physical properties from direct imaging of the sun and sky pancam also provides mission support measurements for the rovers including sun finding for rover navigation hazard identification and digital terrain modeling to help guide long term rover traverse decisions high resolution imaging to help guide the selection of in situ sampling targets and acquisition of education and public outreach products the pancam optical mechanical and electronics design were optimized to achieve these science and mission support goals pancam is a multispectral stereoscopic panoramic imaging system consisting of two digital cameras mounted on a mast 1 5 m above the martian surface the mast allows pancam to image the full 360 in azimuth and 90 in elevation each pancam camera utilizes a 1024 1024 active imaging area frame transfer ccd detector array the pancam optics have an effective focal length of 43 mm and a focal ratio of f 20 yielding an instantaneous field of view of 0 27 mrad pixel and a field of view of 16 16 each rover s two pancam eyes are separated by 30 cm and have a 1 toe in to provide adequate stereo parallax each eye also includes a small eight position filter wheel to allow surface mineralogic studies multispectral sky imaging and direct sun imaging in the 400 1100 nm wavelength region pancam was designed and calibrated to operate within specifications on mars at temperatures from 55 to 5 c an onboard calibration target and fiducial marks provide the capability to validate the radiometric and geometric calibration on mars

geochemical diversity in first rocks examined by the curiosity rover in gale crater evidence for and significance of an alkali and volatile rich igneous source the first four rocks examined by the mars science laboratory alpha particle x ray spectrometer indicate that curiosity landed in a lithologically diverse region of mars these rocks collectively dubbed the bradbury assemblage were studied along an eastward traverse sols 46 102 compositions range from na and al rich mugearite jake matijevic to fe mg and zn rich alkali rich basalt hawaiite bathurst inlet and span nearly the entire range in feo and mno of the data sets from previous martian missions and martian meteorites the bradbury assemblage is also enriched in k and moderately volatile metals zn and ge these elements do not correlate with cl or s suggesting that they are associated with the rocks themselves and not with salt rich coatings three out of the four bradbury rocks plot along a line in elemental variation diagrams suggesting mixing between al rich and fe rich components chemcam analyses give insight to their degree of chemical heterogeneity and grain size variations in trace elements detected by chemcam suggest chemical weathering li and concentration in mineral phases e g rb and sr in feldspars we interpret the bradbury assemblage to be broadly volcanic and or volcaniclastic derived either from near the gale crater rim and transported by the peace vallis fan network or from a local volcanic source within gale crater high fe and fe mn in et then likely reflect secondary precipitation of fe 3 oxides as a cement or rind the k rich signature of the bradbury assemblage if igneous in origin may have formed by small degrees of partial melting of metasomatized mantle

tracking the weathering of basalts on mars using lithium isotope fractionation models lithium li the lightest of the alkali elements has geochemical properties that include high aqueous solubility li is the most fluid mobile element and high relative abundance in basalt forming minerals values ranking between 0 2 and 12 ppm li isotopes are particularly subject to fractionation because the two stable isotopes of lithium 7li and 6li have a large relative mass difference 15 that results in significant fractionation between water and solid phases the extent of li isotope fractionation during aqueous alteration of basalt depends on the dissolution rate of primary minerals the source of li and on the precipitation kinetics leading to formation of secondary phases consequently a detailed analysis of li isotopic ratios in both solution and secondary mineral lattices could provide clues about past martian weathering conditions including weathering extent temperature ph supersaturation and evaporation rate of the initial solutions in contact with basalt rocks in this paper we discuss ways in which martian aqueous processes could have lead to li isotope fractionation we show that li isotopic data obtained by future exploration of mars could be relevant to highlighting different processes of li isotopic fractionation in the past and therefore to understanding basalt weathering and environmental conditions early in the planet s history

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

late cenozoic subduction complex of sicily abstract besides remnants of hercynian deformations in the peloritani nappe and of pre oligocene alpine structures in the troiani nappe most compressive structures observed in the sicilian accretionary wedge result from the late cenozoic tortonian to present continental subduction of the apulia iblei block and are thus synchronous with distensive structures related to the opening of the tyrrhenian sea syntectonic deposits fill southward migrating foredeeps in a sequential fashion and the dating of these deposits helps to constrain the timing of deformation similarly plio quaternary sediments eroded from the accreted units rest on top of the allochthon in either compressive piggy back depressions or extensional basins the age and configuration of these overlap deposits constrain our reconstructions of the subsurface geometry of the underlying peri tyrrhenian detachment faults or s verging thrust faults post depositional erosion normal faulting and syntectonic filling of basins contribute to maintaining the critical taper of the prism whose geometry is continuously altered owing to frontal accretion underplating and isostatic uplift

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

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

evidence from opportunity s microscopic imager for water on meridiani planum the microscopic imager on the opportunity rover analyzed textures of soils and rocks at meridiani planum at a scale of 31 micrometers per pixel the uppermost millimeter of some soils is weakly cemented whereas other soils show little evidence of cohesion rock outcrops are laminated on a millimeter scale image mosaics of cross stratification suggest that some sediments were deposited by flowing water vugs in some outcrop faces are probably molds formed by dissolution of relatively soluble minerals during diagenesis microscopic images support the hypothesis that hematite rich spherules observed in outcrops and soils also formed diagenetically as concretions

metamorphism in the martian crust compositions of basaltic and ultramafic rocks analyzed by mars rovers and occurring as martian meteorites allow predictions of metamorphic mineral assemblages that would form under various thermophysical conditions key minerals identified by remote sensing roughly constrain temperatures and pressures in the martian crust we use a traditional metamorphic approach phase diagrams to assess low grade hydrothermal equilibrium assemblages basaltic rocks should produce chlorite actinolite albite silica accompanied by laumontite pumpellyite prehnite or serpentine talc only prehnite bearing assemblages have been spectrally identified on mars although laumontite and pumpellyite have spectra similar to other uncharacterized zeolites and phyllosilicates ultramafic rocks are predicted to produce serpentine talc and magnesite all of which have been detected spectrally on mars mineral assemblages in both basaltic and ultramafic rocks constrain fluid compositions to be h2o rich and co2 poor we confirm the hypothesis that low grade hydrothermal metamorphism affected the noachian crust on mars which has been excavated in large craters we estimate the geothermal gradient 20 c km 1 required to produce the observed assemblages this gradient is higher than that estimated from radiogenic heat producing elements in the crust suggesting extra heating by regional hydrothermal activity