introduction to the special issue the formation and evolution of ceres occator crater abstract ceres the largest body in the asteroid belt was explored from orbit for the first time by the dawn mission the 92 km diameter occator crater contains bright regions or faculae which are one of the most remarkable discoveries of dawn s exploration of ceres a pit within the center of the crater contains both the cerealia facula and a central dome the vinalia faculae are located in the eastern crater floor occator s faculae are composed mostly of sodium carbonate and their single scattering albedo is the highest of any material on ceres surface the faculae do not occur in other impact craters on ceres and occator s extensive interior lobate materials are unusual understanding the driving forces behind the formation of occator crater and its faculae has the potential to lead us to a new understanding of the processes and conditions in ceres past and to possibly provide constraints about the present day internal state in this special issue we present a variety of investigations which use dawn data theoretical modeling and laboratory experiments to investigate occator crater and its faculae the results of these investigations are summarized and synthesized in the final paper of this collection herein we introduce ceres and the dawn mission and summarize the geophysical geological mineralogical and geochemical properties of ceres as derived from dawn data we also discuss the regional setting of occator crater and introduce occator crater itself

impact melt rocks from the ries structure germany an origin as impact melt flows abstract the production of impact melt rocks and glasses is a characteristic feature of hypervelocity impact events on earth and other planetary bodies this investigation represents the first detailed study of an unusual series of coherent impact melt rocks intermittently exposed around the periphery of the 24 km diameter 14 5 ma ries impact structure germany optical and analytical scanning electron microscopy sem reveals that the groundmass comprises sanidine plagioclase quartz and ilmenite decreasing order of abundance with the interstices filled by either fresh or devitrified glassy mesostasis primary crystallites display skeletal dendritic and or spherulitic textures indicating rapid crystallization from a melt the mesostasis is characterized by extreme chemical heterogeneity e g feo and al 2 o 3 contents from 1 to 62 80 wt this is likely due to a combination of crystal liquid fractionation during rapid cooling and crystallization of an originally incompletely homogenized melt vapor phase crystallization of sanidine and cristobalite occurred in miarolitic cavities during late stage cooling of the impact melts the most likely protolith for the impact melt rocks are granitic rocks present in the crystalline basement target the high volatile content of the mesostasis suggests that a large volatile component was retained from this protolith field observations together with analytical data and micro textures indicate that the ries impact melt rocks were molten at the time of and after deposition field relations with other impactites also suggest that these rocks were emplaced subsequent to the excavation stage of crater formation and that they are not therefore ballistic ejecta thus it is proposed that the ries impact melt rocks were emplaced as ground hugging impact melt flows that emanated from different regions of the evolving transient cavity during the modification stage of crater formation this is consistent with and in fact predicted by field relations which indicate that these rocks overlie unequivocal ejecta this represents the first recognition of impact melt flows near the rim of a terrestrial impact structure and is consistent with observations of such features on the moon and venus

assessment of shock effects on amphibole water contents and hydrogen isotope compositions 2 kaersutitic amphibole experiments to constrain the influence of impact shock on water and hydrogen isotope signatures of martian meteorite kaersutites we conducted shock recovery experiments on three terrestrial kaersutite crystals homogeneous impact shock to 32 gpa commensurate with shock levels experienced by martian meteorite kaersutites led to increases in kaersutite water contents h 2o 0 25 0 89 wt decreases in fe 3 fe 4 20 and enrichments in hydrogen isotope composition d 66 to 87 relative to pre shock values the latter values represent the largest shock induced hydrogen isotope fractionations measured to date these observations are explained most completely by a two step shock process first shock induced devolatilization led to hydrogen isotope enrichment through preferential loss of h relative to d second reaction of the kaersutite with the ambient atmosphere led to increased water contents and reduced fe fe reduction and water addition via the reaction fe 2 oh fe 3 o 2 h 2 explain the fe 3 fe data and some of the water data further water addition mechanisms irreversible adsorption shock implantation are necessary to fully explain the increased water contents addition of water from the terrestrial atmosphere which is isotopically light relative to the experimental kaersutite compositions means the measured hydrogen isotope enrichments are likely minima the measured minimum levels of hydrogen isotope enrichment are relevant to the hydrogen isotope variability within and among martian kaersutites but are minor relative to their absolute d values alternatively addition of water from the enriched martian atmosphere could explain both martian kaersutite hydrogen isotope variability and absolute d values however the low martian kaersutite water contents leave little room for significant water addition the importance of the ambient atmosphere to the outcome of the shock experiments makes it difficult to translate our results to mars given the unknown influence of its more tenuous atmosphere on the processes observed in the experiments our results suggest that shock is a feasible mechanism for influencing martian kaersutite water contents and hydrogen isotope compositions but that its complex signature precludes precise determination of that influence

physical constraints on impact melt properties from lunar reconnaissance orbiter camera images abstract impact melt flows exterior to copernican age craters are observed in high spatial resolution 0 5 m pixel images acquired by the lunar reconnaissance orbiter camera lroc narrow angle camera nac impact melt is mapped in detail around 15 craters ranging in diameter from 2 4 to 32 5 km this survey supports previous observations suggesting melt flows often occur at craters whose shape is influenced by topographic variation at the pre impact site impact melt flows are observed around craters as small as 2 4 km in diameter and preliminary estimates of melt volume suggest melt production at small craters can significantly exceed model predictions digital terrain models produced from targeted nac stereo images are used to examine the three dimensional properties of flow features and emplacement setting enabling physical modeling of flow parameters qualitative and quantitative observations are consistent with low viscosity melts heated above their liquidii superheated with limited amounts of entrained solids

hydrous melting of the martian mantle produced both depleted and enriched shergottites the search for water in our solar system is one of the primary driving forces for planetary science and exploration because water plays an important role in many geologic processes and is required for biologic processes as we currently understand them excluding earth mars is the most promising destination in the inner solar system to find water as it is undoubtedly responsible for shaping many geomorphologic features observed on the present day martian surface however the water content of the martian interior is currently unresolved much of our information about the martian interior comes from studies of the basaltic martian meteorites shergottites in this study we examined the water contents of magmatic apatites from a geochemically enriched shergottite the shergotty meteorite and a geochemically depleted shergottite the queen alexandria range 94201 meteorite from these data we determined that there was little difference in water contents between the geochemically depleted and enriched shergottite magmas the water contents of the apatite imply that shergottite parent magmas contained 730 2870 ppm h 2 o prior to degassing furthermore the martian mantle contains 73 290 ppm h 2 o and underwent hydrous melting as recently as 327 ma in the absence of plate tectonics the presence of water in the interior of mars requires planetary differentiation under hydrous conditions this is the first evidence of significant hydrogen storage in a planetary interior at the time of core formation and this process could support elevated h abundances in the interiors of other terrestrial bodies like the moon mercury venus large differentiated asteroids and earth

hydrogen isotope evidence for loss of water from mars through time 1 the high d h of the martian atmosphere 5 6 terrestrial is considered strong evidence for the loss of martian water to space the timing and magnitude of the loss of water from mars can be constrained by measurements of d h in martian meteorites previous studies of martian meteorites have shown a large range in d h from terrestrial values to as high as the current martian atmosphere here we show that the ancient 4 ga mars meteorite alh84001 has a d h 4 terrestrial and that the young 0 17 ga shergotty meteorite has a d h 5 6 terrestrial we also find that the young los angeles shergottite has zoning in d h that can be correlated to igneous growth zoning strongly suggesting assimilation of d enriched water during igneous crystallization near the martian surface in contrast to previous studies we find higher and less variable d h ratios in these three meteorites our results suggest a two stage evolution for martian water a significant early loss of water to space prior to 3 9 ga followed by only modest loss to space in the last 4 billion years the current martian atmospheric d h has remained essentially unchanged for the last 165 ma

mineralogical analysis of the ac h 6 haulani quadrangle of the dwarf planet ceres abstract ac h 6 haulani is one of five quadrangles that cover the equatorial region of the dwarf planet ceres this quadrangle is notable for the broad spectrally distinct ejecta that originate from the crater haulani which gives the name to the quadrangle these ejecta exhibit one of the most negative bluest visible to near infrared spectral slope observed across the entire body and have distinct color properties as seen in multispectral composite images besides haulani here we investigate a broader area that includes other surface features of interest with an emphasis on mineralogy as inferred from data obtained by dawn s visible infrared mapping spectrometer vir combined with multispectral image products from the dawn framing camera fc so as to enable a clear correlation with specific geologic features our analysis shows that crater haulani stands out compared to other surface features of the quadrangle albedo maps obtained in the near infrared range at 1 2 m and 1 9 m reveal that the floor and ejecta of haulani are indeed a patchwork of bright and dark material units visible to near infrared spectral slopes display negative values in crater haulani s floor and ejecta highlighting bluish younger terrains diagnostic spectral features centered at 2 7 m and 3 1 m respectively indicate a substantial decrease in the abundances of magnesium bearing phyllosilicates and ammoniated phyllosilicates in crater haulani s floor and bright ejecta similar but less prominent spectral behavior is observed in other geologic features of this quadrangle while the general trend in quadrangle ac h 6 for these two mineral species is to increase from the northwest to the southeast however it is worth noting that the correlation between the 2 7 m and 3 1 m spectral parameters is generally strong in the haulani crater s area but much weaker elsewhere which indicates a variable degree of mixing between these two major mineral phases in moving away from the crater finally the region of crater haulani displays a distinct thermal signature and a local enhancement in calcium and possibly sodium carbonate minerals which is hardly found in the rest of the quadrangle and is likely the result of intense hydrothermal processes following the impact event these evidences all together confirm the young age of crater haulani as they have not been erased or made elusive by space weathering processes

mass movement and landform degradation on the icy galilean satellites results of the galileo nominal mission the galileo mission has revealed remarkable evidence of mass movement and landform degradation on the icy galilean satellites of jupiter weakening of surface materials coupled with mass movement reduces the topographic relief of landforms by moving surface materials down slope throughout the galileo orbiter nominal mission we have studied all known forms of mass movement and landform degradation of the icy galilean satellites of which callisto by far displays the most degraded surface callisto exhibits discrete mass movements that are larger and apparently more common than seen elsewhere most degradation on ganymede appears consistent with sliding or slumping impact erosion and regolith evolution sliding or slumping is also observed at very small 100 m scale on europa sputter ablation while probably playing some role in the evolution of ganymede s and callisto s debris layers appears to be less important than other processes sputter ablation might play a significant role on europa only if that satellite s surface is significantly older than 108 years far older than crater statistics indicate impact erosion and regolith formation on europa are probably minimal as implied by the low density of small craters there impact erosion and regolith formation may be important on the dark terrains of ganymede though some surfaces on this satellite may be modified by sublimation degradation while impact erosion and regolith formation are expected to operate with the same vigor on callisto as on ganymede most of the areas examined at high resolution on callisto have an appearance that implies that some additional process is at work most likely sublimation driven landform modification and mass wasting the extent of surface degradation ascribed to sublimation on the outer two galilean satellites implies that an ice more volatile than h2o is probably involved

volatiles in the martian crust and mantle clues from the nwa 6162 shergottite abstract martian meteorites of various petrogeneses retain a record of volatiles on mars from the hydrosphere crustal water to the mantle sputtering of the martian atmosphere by solar wind after the loss of mars magnetic field enriched it in deuterium which exchanged with martian crustal water recent studies show that the hydrogen isotopic composition of the martian crustal water reservoir varies from 3000 to 7000 but requires better constraints melt inclusion glasses maskelynite and fusion crust from the depleted olivine phyric shergotite nwa 6162 were analyzed using nanosims providing a unique insight into the hydrogen isotopic and volatile elemental content of both the martian crustal water reservoir and the mantle source the h2o s and cl contents of the melt inclusion glasses are 0 3137 14 239 and 16 967 ppm respectively d values vary from 560 to 6137 the water content positively correlates with the d values in both the melt inclusion glasses and maskelynite in a two end member mixing trend one end member is the magmatic water with a d value of 0 and the other end member is the martian crustal water with d ranging from 5000 to 6000 nwa 6162 a depleted olivine phyric shergottite originated from a different mantle source to the enriched lherzolitic shergottites however both types of shergottites exchanged with martian crustal water with the same d values indicating a homogeneous martian crustal water hydrogen isotopic composition 5000 6000 most melt inclusion glasses from nwa 6162 have low water content 0 234 ppm except for two enriched locations as micron sized bands and dendrites the low water content in most melt inclusion glasses the dendritic shaped water enriched areas in melt inclusions and the martian crustal water diffusion profile recorded in maskelynite collectively suggest short lived water rock interactions in the nwa 6162 parent rock that was probably induced by impact furthermore a great contribution up to 98 of surface cl accompanying d enriched water was recorded in the melt inclusions supported by the positive correlation between cl and h2o the presence of sulfide and s rich hot spots and low d end member of the magmatic water indicate that the degassing during post entrapment crystallization and ascent of the melt inclusion is negligible h2o s and cl contents of the martian mantle reservoir are estimated to be 0 1 3 0 5 15 and 0 5 4 ppm respectively after the correction of fractional crystallization of the melt inclusions and contribution from the martian surface reservoir the martian mantle reservoir estimated from nwa 6162 was water s and cl poorer than the earth s interior

massive ice avalanches on iapetus mobilized by friction reduction during flash heating the great distance travelled by long runout landslides observed previously on the earth and mars requires a mechanism of friction reduction identification and analysis of long runout landslides on saturn s moon iapetus suggests that the iapetian landslides are enabled by flash heating of the icy sliding surface

ceres impact craters relationships between surface composition and geology abstract impact craters of different geological ages sizes and morphologies are not only the most obvious surface features on ceres surface the investigation of their spectral properties in combination with ceres geology and topography reveals not only lateral compositional variations in ceres surface material but also possible stratigraphic differences within ceres crust spectral properties of impact craters with different ages do show distinct trends implying variations with increasing exposure duration of the impact material onto ceres surface local concentrations of h2o ice and carbonates are associated with the youngest either recently emplaced or excavated surface deposits on the contrary regionally higher amounts of ammoniated phyllosilicates originate from deeper regions of ceres crust and strengthen the theory of ammonia being a primordial constituent of ceres the blue spectral slope clearly associated with relatively weak absorptions of oh bearing and or ammoniated phyllosilicates is limited to fresh impact material either the blue spectral slope diminishes slowly with increasing geologic age due to space weathering processes or shortly as a result of gravitation induced slumping forming a fine and loosely consolidated regolith

the geology of the occator quadrangle of dwarf planet ceres floor fractured craters and other geomorphic evidence of cryomagmatism abstract the dawn science team is conducting a geological mapping campaign at ceres during the nominal mission including iterative mapping using data obtained during each orbital phase we are using geological mapping as a method to identify the geologic processes that have modified the surface of dwarf planet ceres we here present the geology of the ac 9 occator quadrangle located between 22 s 22 n and 216 288 e the ac 9 map area is within the topographically high region named hanami planum features of note within the profile include impact craters occator azacca lociyo nepen and kirnis four of these craters have fractured shallow floors morphometrically comparable to floor fractured craters ffcs on the moon similar to models for the formation of the lunar ffcs we suggest that these ceres ffcs are a result of cryomagmatic uplift under the crater floors a set of regional linear structures called the samhain catenae do not have any obvious relationship to impact craters many of the catenae are comprised of smaller structures that have linked together suggestive of en echelon fractures it has been suggested that these fractures formed due to the uplift of hanami planum due to cryromagmatic plumes

high pressure phases in a shock induced melt vein of the tenham l6 chondrite constraints on shock pressure and duration abstract the microtexture and mineralogy of a 580 m wide melt vein in the tenham l6 chondrite were investigated using field emission scanning electron microscopy and transmission electron microscopy to better understand the shock conditions the melt vein consists of a matrix of silicate plus metal sulfide grains that crystallized from immiscible melts and sub rounded fragments of the host chondrite that have been entrained in the melt and transformed to polycrystalline high pressure silicates the melt vein matrix contains two distinct textures and mineral assemblages corresponding to the vein edge and interior the 30 m wide vein edge consists of vitrified silicate perovskite ringwoodite akimotoite majorite with minor metal sulfide the 520 m wide vein interior consists of majorite magnesiowustite with irregular metal sulfide blebs although these mineral assemblages are distinctly different the pressure stabilities of both assemblages are consistent with crystallization from similar pressure conditions the melt vein edge crystallized at about 23 25 gpa and the vein interior crystallized at about 21 25 gpa this relatively narrow pressure range suggests that the melt vein either crystallized at a constant equilibrium shock pressure of 25 gpa or during a relatively slow pressure release using a finite element heat transfer program to model the thermal history of this melt vein during shock we estimate that the time required to quench this 580 m wide vein was 40 ms because the entire vein contains high pressure minerals that crystallized from the melt the shock pressure duration was at least 40 ms using a synthetic hugoniot for tenham and assuming that the sample experienced a peak shock pressure of 25 gpa near the impact site we estimate that the tenham parent body experienced an impact with collision velocity 2 km s based on a one dimensional planar impact model we estimate that the projectile size was 150 m in thickness

resolved spectrophotometric properties of the ceres surface from dawn framing camera images we present a global spectrophotometric characterization of the ceres surface using dawn framing camera fc images we identify the photometric model that yields the best results for photometrically correcting images corrected fc images acquired on approach to ceres were assembled into global maps of albedo and color generally albedo and color variations on ceres are muted the albedo map is dominated by a large circular feature in vendimia planitia known from hst images li et al 2006 and dotted by smaller bright features mostly associated with fresh looking craters the dominant color variation over the surface is represented by the presence of blue material in and around such craters which has a negative spectral slope over the visible wavelength range when compared to average terrain we also mapped variations of the phase curve by employing an exponential photometric model a technique previously applied to asteroid vesta schroder et al 2013b the surface of ceres scatters light differently from vesta in the sense that the ejecta of several fresh looking craters may be physically smooth rather than rough high albedo blue color and physical smoothness all appear to be indicators of youth the blue color may result from the desiccation of ejected material that is similar to the phyllosilicates water ice mixtures in the experiments of poch et al 2016 the physical smoothness of some blue terrains would be consistent with an initially liquid condition perhaps as a consequence of impact melting of subsurface water ice we find red terrain positive spectral slope near ernutet crater where de sanctis et al 2017 detected organic material the spectrophotometric properties of the large vendimia planitia feature suggest it is a palimpsest consistent with the marchi et al 2016 impact basin hypothesis the central bright area in occator crater cerealia facula is the brightest on ceres with an average visual normal albedo of about 0 6 at a resolution of 1 3 km per pixel six times ceres average the albedo of fresh bright material seen inside this area in the highest resolution images 35 m per pixel is probably around unity cerealia facula has an unusually steep phase function which may be due to unresolved topography high surface roughness or large average particle size it has a strongly red spectrum whereas the neighboring less bright vinalia faculae are neutral in color we find no evidence for a diurnal ground fog type haze in occator as described by nathues et al 2015 we can neither reproduce their findings using the same images nor confirm them using higher resolution images fc images have not yet offered direct evidence for present sublimation in occator

mineralogical analysis of quadrangle ac h 10 rongo on the dwarf planet ceres abstract quadrangle ac h 10 rongo lat 22 s to 22 n lon 288 360 e shows a fairly homogeneous topography with the presence of notable elevations such as ahuna mons liberalia mons and part of samhain and uhola catenae the deepest areas correspond to the rongo crater region the areas between samhain and uhola catenae and the region of the quadrangle south of ahuna mons a substantial variability in the 2 7 m band depth distribution is observed across the rongo quadrangle indicating an east west gradient in the abundance of mg phyllosilicates the nh4 phyllosilicates distribution appears quite homogeneous except some localized regions such as crater haulani s ejecta the flanks of ahuna mons and crater begbalel the two band depths at 2 7 and 3 1 m display an overall low correlation suggesting a variable degree of mixing between mg phyllosilicates and nh4 phyllosilicates at the local scale mineralogical phases other than phyllosilicates are observed quadrangle rongo includes sodium carbonate rich regions such as the flanks of ahuna mons the ejecta of xevioso crater located in the southern edge of liberalia mons and crater begbalel which often display a reduction in both the 2 7 and 3 1 m band depths associated with an increased band depth at 4 m related to the presence of na rich carbonate phases this suggests recent hydrothermal activity in this area due to several episodes of cryovolcanism or impacts that unveiled a peculiar composition in the shallow subsurface alternatively the crust in this region might show a variable degree of compactness such that the formation of na carbonates is favored only in specific locations de sanctis et al 2016 ruesch et al 2016 zambon et al 2017 from a geological standpoint quadrangle ac h 10 rongo shows a correlation between its two main geologic units platz et al 2017 and the distribution of mg phyllosilicates suggesting a link between geology and mineralogy in this area

evidence in tissint for recent subsurface water on mars we report unambiguous chemical evidence for subsurface water activity in the martian crust at 600 ma based on the data from tissint a fresh martian meteorite fall with minimal terrestrial weathering the impact melt pockets in tissint contain abundant volatiles h 2o co 2 f and cl and their concentrations are positively correlated with each other higher h 2o concentrations also accompany higher deuterium contents these correlations suggest mixing between two volatile sources the first source is h 2o in the precursor basalt inherited from martian magma magmatic h 2o in the basalt had low deuterium concentration and was likely stored in the nominally anhydrous minerals this source contributed little co 2 or halogens to the impact melts the second source is inferred to be aqueous alteration products introduced to the basalt by water activity after the basalt erupted these alteration materials contributed more volatiles to the impact melts than the magmatic source and had high deuterium abundance reflecting isotope equilibrium with recent martian atmosphere the water activities occurred beneath the martian surface after 600 ma crystallization age but before 1 ma ejection age the chemical and isotopic signatures of the alteration products in tissint resemble previously known martian samples associated with old water activities on mars which can be traced back to 4 2 billion years ago e g the mudstone at gale crater this similarity in chemistry and the wide age span indicate that such water activities were common on mars throughout its history which had the potential to form habitable environment however the rarity of the volatile rich zone in tissint suggests that martian crustal aqueous processes where they have occurred are generally limited in their extent of water rock reaction

ceres occator crater and its faculae explored through geologic mapping abstract occator crater is one of the most recognizable features on ceres because of its interior bright regions which are called the cerealia facula and vinalia faculae here we use high resolution images from dawn 35 m pixel to create a detailed geologic map that focuses on the interior of occator crater and its ejecta occator s asymmetric ejecta indicates that the occator forming impactor originated from the northwest at an angle of 30 45 perhaps closer to 30 some of occator s geologic units are analogous to the units of other complex craters in the region the ejecta crater terrace material hummocky crater floor material and talus material the geologic units that make occator unique are the bright occator pit fracture material this is the unit that corresponds to the cerealia facula and vinalia faculae and the extensive well preserved lobate materials we propose that the lobate materials are a slurry of impact melted and non impact melted target material which flowed around the crater interior before solidifying to form deposits geomorphologically consistent with impact melts elsewhere in the solar system we sub divide the lobate materials on the basis of their surface textures it is likely that knobby or smooth lobate materials form if the lobate material entrains or does not entrain blocks respectively post impact inflation is suggested to form the hummocky lobate material the vinalia faculae formed within the hummocky lobate material we find that the knobby lobate material and the outer edge of the cerealia facula formed prior to the central pit the central dome formed after the formation of the central pit while the majority of the cerealia facula besides the outer edge could have formed continued to form and or have been modified after the formation of the central pit the cerealia facula may have initially been emplaced in a similar process to the vinalia faculae and the surface of the cerealia facula appear to have somewhat darkened over time the insights into occator crater and its faculae derived from our geologic mapping will be synthesized together with inputs from all of the studies in this special issue in scully et al 2018a

the various ages of occator crater ceres results of a comprehensive synthesis approach abstract the 90 5 km occator crater with its peculiar and unique bright spots is one of the most prominent and renowned feature on ceres occator attracted broad public attention in scientific media as it is proposed to exhibit signs of post impact cryovolcanic activity in order to understand the time sequence of deposition several attempts were made during dawn s primary mission by different research groups to date geomorphologic key units using superposed crater densities resulting absolute model formation ages for occator s ejecta and its interior lobate deposits range from 200 ma to 78 ma and about 100 ma to 6 9 ma but were based on different cratering chronology models measurements on image data at varying resolution and different statistical and methodological approaches here we present the results of a comprehensive approach of determining absolute model formation ages for occator this is achieved by using the best resolved framing camera image data by careful treatment of secondary crater admixture and the natural variability of crater detection and sizes by different crater analysts and by applying appropriate objective criteria for count area selection in this context we evaluate previously published model ages and explain why our results are likely to yield more consistent and robust information about the formation age of occator we also show that in contrast to previous publications csfds measured on occator s less competent ejecta blanket and its more competent cryovolcanic or impact melt related interior lobate deposits ilds are so similar to each other that the slight differences might rather be explained by different scaling parameters in different target materials or that the ilds have formed almost contemporaneously or only shortly after the occator forming impact

bright carbonate surfaces on ceres as remnants of salt rich water fountains abstract vinalia and cerealia faculae are bright and salt rich localized areas in occator crater on ceres the predominance of the near infrared signature of sodium carbonate on these surfaces suggests their original material was a brine here we analyze dawn framing camera s images and characterize the surfaces as composed of a central structure either a possible depression vinalia or a central dome cerealia and a discontinuous mantling we consider three materials enabling the ascent and formation of the faculae ice ascent with sublimation and carbonate particle lofting pure gas emission entraining carbonate particles and brine extrusion we find that a mechanism explaining the entire range of morphologies topographies as well as the common composition of the deposits is brine fountaining this process consists of briny liquid extrusion followed by flash freezing of carbonate and ice particles particle fallback and sublimation subsequent increase in briny liquid viscosity leads to doming dawn observations did not detect currently active water plumes indicating the frequency of such extrusions is longer than years

space weathering on airless bodies space weathering refers to alteration that occurs in the space environment with time lunar samples and to some extent meteorites have provided a benchmark for understanding the processes and products of space weathering lunar soils are derived principally from local materials but have accumulated a range of optically active opaque particles oaopq that include nanophase metallic iron on in rims formed on individual grains imparting a red slope to visible and near infrared reflectance and larger iron particles which darken across all wavelengths such as are often found within the interior of recycled grains space weathering of other anhydrous silicate bodies such as mercury and some asteroids produce different forms and relative abundance of oaopq particles depending on the particular environment if the development of oaopq particles is minimized such as at vesta contamination by exogenic material and regolith mixing become the dominant space weathering processes volatile rich bodies and those composed of abundant hydrous minerals dwarf planet ceres many dark asteroids outer solar system satellites are affected by space weathering processes differently than the silicate bodies of the inner solar system however the space weathering products of these bodies are currently poorly understood and the physics and chemistry of space weathering processes in different environments are areas of active research

shock induced devolatilization and isotopic fractionation of h and c from murchison meteorite some implications for planetary accretion incipient shock induced devolatilization of murchison meteorite occurs upon subjecting samples to a minimum shock stress or pressure of about 5 gpa this pressure is similar to that required to initiate devolatilization of 20 porous serpentine upon low velocity impact 61 5 km s the solid shocked products were combusted and isotopic analysis of the resulting h 2o and co 2 was performed h and 13 c are partitioned preferentially over d and 12 c respectively into the released gas suggesting that the inorganic mineral portion of murchison is devolatilized preferentially over the organic kerogen fraction which is relatively enriched in d and 12 c at the shock pressures studied these results are combined with previous results on serpentine devolatilization to derive an empirical h fractionation versus devolatilization relation that is used to evaluate the extent of impact induced isotopic fractionation during planetary accretion during accretion of the earth impact induced devolatilization and formation of the early primitive atmosphere would have begun at a point where the growing earth achieved a radius in the 480 800 km range the present experimental results suggest that the earth s early atmosphere would have been enriched in hydrogen relative to d compared to the residual solid with a fractionation factor of 18 to 23 assuming that current planetary atmospheres have resulted from degassing of planetary interiors after loss of the earliest h enriched atmosphere the above degree of isotopic fractionation is not sufficient by itself to explain the large positive d values of the present martian and venusian atmospheres however this mechanism in conjunction with tectonic recycling over geologic time could contribute to preferential h loss for earth and mars

net effect of rainfall activity on salt marsh sediment distribution it has been established that increased suspended sediment concentrations in tidal waters adjacent to salt marshes occur during periods following heavy rainfall events in this work we present experimental data for concentration and sediment flux measurements during periods of natural moderate rainfall events from a microtidal alochthonous salt marsh system north inlet south carolina usa the results indicate that rainfall events although responsible for increasing sediment concentration levels do not alter the sediment flux of the system in our results the sediment mobilized by the rain was re introduced to the system further using the geochemical signatures of suspended particles from the same location we found that the sediment mobilized by rainfall events is the same as the sediment present in the tidal creeks suggesting that rainfall mobilizes only recently deposited non consolidated sediment and does not erode the substrate of the marsh surface

formation of iddingsite veins in the martian crust by centripetal replacement of olivine evidence from the nakhlite meteorite lafayette abstract the lafayette meteorite is an olivine clinopyroxenite that crystallized on mars 1300 million years ago within a lava flow or shallow sill liquid water entered this igneous rock 700 million years later to produce a suite of secondary minerals collectively called iddingsite that occur as veins within grains of augite and olivine the deuterium hydrogen ratio of water within these secondary minerals shows that the aqueous solutions were sourced from one or more near surface reservoirs several petrographically distinct types of veins can be recognised by differences in their width shape and crystallographic orientation augite and olivine both contain veins of a very fine grained hydrous fe and mg rich silicate that are 1 2 m in width and lack any preferred crystallographic orientation these narrow veins formed by cementation of pore spaces that had been opened by fracturing and probably in response to shock the subset of olivine hosted veins whose axes lie parallel to 0 0 1 have serrated walls and formed by widening of the narrow veins by interface coupled dissolution precipitation widening started by replacement of the walls of the narrow precursor veins by fe mg silicate and a crystallographic control on the trajectory of the dissolution precipitation front created micrometre scale 1 1 1 serrations the walls of many of the finely serrated veins were subsequently replaced by siderite and the solutions responsible for carbonation of olivine also partially recrystallized the fe mg silicate smectite was the last mineral to form and grew by replacement of siderite this mineralization sequence shows that lafayette was exposed to two discrete pulses of aqueous solutions the first of which formed the fe mg silicate and the second mediated replacement of vein walls by siderite and smectite the similarity in size shape and crystallographic orientation of iddingsite veins in the lafayette meteorite and in terrestrial basalts demonstrates a common microstructural control on water mineral interaction between mars and earth and indicates that prior shock deformation was not a prerequisite for aqueous alteration of the martian crust

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

evolution of water reservoirs on mars from d h ratios in the atmosphere and crust ancient fluvial networks on the surface of mars suggest that it was warm and wet over three billion years ago surface features resembling massive outflow channels provide evidence that even more recently the martian crust contained the equivalent of a planet wide reservoir of water several hundred metres deep but arguments based on the isotopic fraction and present day escape rate of hydrogen in the martian atmosphere require only 0 5 metres of crustal water today and about six metres in the past an additional constraint on the evolution of the isotopic composition of martian water has recently been obtained from measurements of the deuterium to hydrogen ratio of hydrous minerals in the snc meteorites meteorites that almost certainly originated on mars here i show that these new data require that the modern crustal reservoirs of martian water must be quite large at least several metres in global equivalent depth the deuterium enrichment of the present martian atmosphere then implies that the reservoir of crustal water on ancient mars was several hundred metres deep consistent with the geological evidence

the sources of water in martian meteorites clues from hydrogen isotopes abstract h isotope measurements of carbonate phosphate feldspathic and mafic glasses and post stishovite silica phase in the shergottites zagami shergotty sau 005 dag 476 alha 77005 and eeta 79001 as well as in chassigny and alh 84001 show that all these phases contain deuterium enriched water of extraterrestrial origin the minerals and glasses analyzed may contain an initial primary hydrogen component but their isotopic composition was modified to varying degrees by three different processes interaction with a fractionated exchangeable water reservoir on mars hydrogen devolatilization by impact melting and terrestrial contamination positive correlations between d and water abundance in feldspathic glass and post stishovite silica in zagami shergotty and sau 005 is indicative of mixing of a high d component 3000 4000 and a less abundant low d component 0 the high d component is primarily derived from the martian exchangable reservoir but may also have been influenced by isotopic fractionation associated with shock induced hydrogen loss the low d component is either a terrestrial contaminant or a primary magmatic component the negative correlation between d and water abundances in mafic and feldspathic glasses in alh 84001 alha 77005 and eeta 79001 is consistent with the addition of a low d terrestrial contaminant to a less abundant high deuterium martian component the low d of magmatic glass in melt inclusions suggests that the d of martian parent magma was low and that the initial h isotope signature of mars may be similar to that of earth

ejection of martian meteorites we investigated the transfer of meteorites from mars to earth with a combined mineralogical and numerical approach we used quantitative shock pressure barometry and thermodynamic calculations of post shock temperatures to constrain the pressure temperature conditions for the ejection of martian meteorites the results show that shock pressures allowing the ejection of martian meteorites range from 5 to 55 gpa with corresponding post shock temperature elevations of 10 to about 1000 c with respect to shock pressures and post shock temperatures an ejection of potentially viable organisms in martian surface rocks seems possible a calculation of the cooling time in space for the most highly shocked martian meteorite allan hills alh 77005 was performed and yielded a best fit for a post shock temperature of 1000 c and a meteoroid size of 0 4 to 0 6 m the final burial depths of the sub volcanic to volcanic martian rocks as indicated by textures and mineral compositions of meteorites are in good agreement with the postulated size of the potential source region for martian meteorites during the impact of a small projectile 200 m as defined by numerical modeling artemieva and ivanov 2004 a comparison of shock pressures and ejection and terrestrial ages indicates that on average highly shocked fragments reach earth crossing orbits faster than weakly shocked fragments if climatic changes on mars have a significant influence on the atmospheric pressure they could account for the increase of recorded ejection events of martian meteorites in the last 5 ma

magmatic water in the martian meteorite nakhla abstract mars does not recycle crustal materials via plate tectonics for this reason the magmatic water reservoir of the martian mantle has not been affected by surface processes and the deuterium hydrogen d h ratio of this water should represent the original primordial martian value following this logic hydrous primary igneous minerals on the martian surface should also carry this primordial d h ratio assuming no assimilation of martian atmospheric water during crystallization and no major hydrogen fractionation during melt degassing hydrous primary igneous minerals such as apatite and amphibole are present in martian meteorites here on earth providing these minerals have not been affected by terrestrial weathering martian atmospheric water or shock processes after crystallization they should contain a good approximation of the primordial martian d h ratio as nakhla was seen to fall in the egyptian desert in 1911 terrestrial contamination is minimized in this meteorite the nakhlites are also among the least shocked of the martian meteorites therefore apatite within nakhla could contain primordial martian hydrogen isotope ratios we produced in situ measurements of the d h ratios in nakhla apatite grains using a cameca ims 1280 ion microprobe our measurements produced d h values in nakhla apatite similar to terrestrial values despite strong evidence that our samples were not significantly contaminated by terrestrial hydrogen these results suggest that water trapped in the martian mantle has a similar d h to that of the earth therefore the water of these two planets may have originated from the same source material the d h ratios of the carbonaceous chondrite meteorites and the jupiter family comet 103p hartley 2 are similar to the d h of the two planets making both these primitive inner solar system materials strong candidates for the source of the terrestrial planets water these results support recent dynamical models of the formation of the solar system which suggest material in the inner solar system was homogenized by the migration of jupiter

a possible brine reservoir beneath occator crater thermal and compositional evolution and formation of the cerealia dome and vinalia faculae abstract the dawn spacecraft has imaged several putative cryovolcanic features on ceres and several lines of evidence point to past cryovolcanic activity at occator crater it is therefore possible that cryovolcanism played a key role in delivering sodium carbonate and chloride enriched brines to ceres surface in recent geological times the detection of a 200 km 200 km negative bouguer anomaly beneath occator suggests the presence of a low density region beneath the crater if this region is a residual partially crystallized cryomagma chamber excess pressures caused by its gradual freezing or stresses produced by the occator forming impact could have facilitated the delivery of cryolavas to the surface in the geologically recent past here the progressive solidification of a cryomagma chamber beneath occator and implications for the delivery of cryolavas to the surface has been explored models for the behavior of cryolavas at ceres surface and for the formation of the cerealia dome and vinalia faculae are also presented minimal crystallization of a subsurface fluid reservoir located at the crust mantle boundary could have driven cryolavas enriched in chloride salts and nh3 to ceres surface however cryolavas enriched in sodium carbonates would have had to have existed at shallower levels in the crust in order to be delivered to the surface via pressure driven ascent depending on the size of the reservoir cryolavas could have been driven to ceres surface for tens to hundreds of millions of years after cooling of the cryomagma chamber commenced the mineralogy at occator is suggestive of subsurface cryomagma reservoirs enriched in sodium carbonate and chloride salts aqueous solutions enriched in chloride salts and or ammonia would have arrived at the surface at warm enough temperatures to erupt if transported in propagating fractures that traveled at least 10 5 m s additionally if the cerealia dome was formed from viscous cryolava extrusions bulk kinematic lava viscosities may have been between 106 108 m2 s at the onset of relaxation plausible relaxation times to form the dome which are linked to bulk cryolava rheology are found to have ranged from 2 5 to 273 days moreover the low volatile content necessary to drive explosive eruptions on ceres supports the possibility that cerealia and vinalia faculae were emplaced as a consequence of ballistic eruptions the enigmatic geology of occator crater is consistent with a diversity of exchange processes operating on ceres in the geologically recent past further the processes that have occurred at occator could shed light on the changing geology associated with a relic ocean world future studies of occator and ceres should be undertaken with these results in mind

ceres ezinu quadrangle a heavily cratered region with evidence for localized subsurface water ice and the context of occator crater abstract dawn is the first spacecraft to visit and orbit ceres the largest object in the asteroid belt and the only dwarf planet in the inner solar system the dawn science team undertook a systematic geologic mapping campaign of ceres entire surface here we present our contribution to this mapping campaign a geologic map and geologic history of the ezinu quadrangle located in the northern mid latitudes from 21 66 n and 180 270 e from our map we reconstruct the geologic history of ezinu quadrangle which is dominated by impact cratering large impact craters that formed a few hundreds to tens of millions of years ago such as datan messor ninsar and occator are surrounded by ejecta and contain the products of mass wasting hummocky crater floor material and talus material and crater wall collapse terrace material two of these large impact craters are the sources of lobate flows which we interpret as melt flows emplaced after the ballistically deposited ejecta morphological evidence suggests these lobate flows are rich in water ice bearing material that was excavated during the formation of the impact craters there are only a few localized occurrences of lobate flows suggesting that the water ice bearing source materials have restricted extents and or are deeply buried within ceres subsurface the quadrangle also contains a variety of linear features secondary crater chains are formed by the impact of locally and globally sourced material and pit chains and grooves are formed by the collapse of surficial materials into sub surface fractures the ezinu quadrangle contains the northern portion of occator crater which is the host crater of prominent bright regions called faculae our geologic analysis therefore also provides context for the future investigation of occator and its intriguing faculae

shock metamorphism and petrography of the shergotty achondrite the shergotty subsamples 1 and 12 consist of augite and pigeonite 67 5 maskelynite 24 ilmenite and titanomagnetite 2 pyrrhotite 0 4 whitlockite 1 8 apatite 0 1 quartz 0 5 baddeleyite trace fayalite 0 4 mesostasis 3 and shock induced local polymineralic melt products 0 6 the overall modal composition is similar to other shergotty samples except for the rather high whitlockite content the shock effects observed in the mineral constituents include mosaicism deformation bands planar fractures and mechanical twin lamellae in clinopyroxene isotropization of plagioclase with very rare remnants of birefringence planar deformation structures mosaicism and strongly reduced birefringence in quartz mechanical twinning of ilmenite localized in situ melting of neighbouring minerals at the contact of low and high density phases based on the refractive index of maskelynite average 1 5467 with average an content of 49 and the degree of isotropization of the plagioclase an equilibrium shock pressure of 29 1 gpa is derived the inferred post shock temperature is 200 20 c no heating event could have exceeded 400 c duke 1968 local stress and temperature concentrations reach 60 80 gpa and 1600 2000 c the observed shock effects can be explained by a single shock event a second weaker shock event as found by others appears to be highly improbable equilibrium shock pressures and post shock temperatures for the other known shergottites are 31 2 gpa and 220 50 c zagami 43 2 gpa and 400 800 c alha 77005 the pressure estimate for eeta 79001 by lambert 1985 is confirmed 34 1 gpa the post shock temperature is 250 50 c the abundance and textural setting of localized melt products in these meteorites confirm increasing shock pressures in the sequence shergotty zagami eeta 79001 alha 77005 undoubtedly the melts could have been formed by the same single shock which produced the equilibrium shock effects e g maskelynitization in these meteorites the shock induced particle velocities inferred from hugoniot data of basalts are in the 1 5 2 0 km s range for the parental rocks of the shergottites ejection velocities are therefore in the order of 3 4 km s special ejection mechanisms are required in order to exceed the escape velocity of a planet like mars without producing higher degrees of shock e g melting than those observed in the shergottites

preservation of primordial signatures of water in highly shocked ancient lunar rocks abstract spurred by the discovery of water in lunar volcanic glasses about a decade ago the accessory mineral apatite became the primary target to investigate the abundance and source of lunar water this is due to its ability to contain significant amounts of oh in its structure along with the widespread presence of apatite in lunar rocks there is a general understanding that crustal cumulate rocks of the lunar magnesian mg suite are better candidates for recording the original isotopic compositions of volatile elements in their parental melts compared to eruptive rocks such as mare basalts consequently water bearing minerals in mg suite rocks are thought to be ideal candidates for discerning the primary hydrogen isotopic composition of water in the lunar interior mg suite rocks and most other apollo samples that were collected at the lunar surface display variable degrees of shock deformation in this study we have investigated seven apollo 17 mg suite samples that include troctolite gabbro and norite lithologies in order to understand if shock processes affected the water abundances and or h isotopic composition of apatite the measured water contents in apatite grains range from 31 to 964 ppm with associated d values varying between 535 134 and 147 194 2 considering the full dataset there appears to be no correlation between h2o and d of apatite and the level of shock each apatite grain has experienced however the lowest d was recorded by individual water poor 100 ppm h2o regardless of the complexity of the shock induced nanostructures there appears to be no evidence of water loss or alteration in their d the weighted average d value of 24 such water rich apatites is 192 71 and of all 36 analyzed spots is 209 47 indistinguishable from that of other kreepy lunar lithologies or the earth s deep mantle despite experiencing variable degrees of shock deformation at a later stage in lunar history water rich apatite in some of the earliest formed lunar crustal material appears to retain the original isotopic signature of h in the moon

impact induced devolatilization and hydrogen isotopic fractionation of serpentine implications for planetary accretion the degree of impact induced devolatilization of nonporous serpentine porous serpentine and deuterium enriched serpentine was investigated using two independent experimental methods the gas recovery method and the solid recovery method yielding consistent results the gas recovery method enables determination of the chemical and hydrogen isotopic composition of the recovered gases experiments on deuterium enriched serpentine unambiguously identify the samples as the source of the recovered gases as opposed to other possible contaminants for shock pressures near incipient devolatilization p initial 5 0 gpa the hydrogen isotopic composition of the evolved gas is similar to that of the starting material for higher shock pressures the bulk evolved gas is significantly lower in deuterium than the starting material there is also significant reduction of h 2o to h 2 in gases recovered at higher shock pressures probably caused by reaction of evolved h 2o with the metal gas recovery fixture the hydrogen isotopic fractionation between the evolved gas and the residual solid indicates nonequilibrium kinetic control of gas solid isotopic ratios in contrast gaseous h 2o h 2 isotopic fractionation suggests high temperature 800 1300 k isotopic equilibrium between the gaseous species indicating initiation of devolatilization at sites of greater than average energy deposition i e shear bands impact induced hydrogen isotopic fractionation of hydrous silicates during accretion can affect the distribution of hydrogen isotopes of planetary bodies during accretion leaving the interiors enriched in deuterium the significance of this process for planetary development depends on the models used for extrapolation of the observed isotopic fractionation to devolatilizations greater than those investigated experimentally and assumptions about timing and rates of protoatmosphere loss frequency of multiple impacts and rates of gas solid or gas melt isotopic re equilibration a simple model indicates that substantial planetary interior enrichments of d h relative to that of the incident material can result from impact induced hydrogen fractionation during accretion

geological mapping of the ac 10 rongo quadrangle of ceres abstract the dawn spacecraft arrived at dwarf planet ceres in spring 2015 and imaged its surface from four successively lower polar orbits at ground sampling dimensions between 1 3 km px and 35 m px to understand the geological history of ceres a mapping campaign was initiated to produce a set of 15 quadrangle based geological maps using the highest resolution framing camera imagery here we present the geological map of the ac 10 rongo quadrangle which is located at the equator encompassing the region from 22 n to 22 s and 288 to 360 e the total relief within the quadrangle is 11 1 km with altitudes ranging from about 7 3 km to 3 8 km we identified nine geological units based on surface morphology and surface textural characteristics the dominant and most widespread unit is the cratered terrain crt representing ancient reworked crustal material its consistent formation age across the quadrangle is 1 8 ga two edifices unit th ahuna mons and an unnamed tholus within begbalel crater are interpreted to be of cryo volcanic origin the southwest portion of the quadrangle is dominated by ejecta material ye emplaced during the formation of the 260 km diameter yalode impact basin at about 580 ma rayed crater ejecta material cr is dominant in the eastern part of the quadrangle but also occurs in isolated patches up to a distance of 455 km from the 34 km diameter source crater haulani the remaining five geological units also represent impact crater materials degraded rim crdeg bright crater cb hummocky floor cfh talus ta and crater c materials widespread yalode and haulani ejecta materials can potentially be utilised as stratigraphic markers therefore it is essential to consistently map their full areal extent and to date their formations using impact crater statistics

deuterium and 37 chlorine rich fluids on the surface of mars evidence from the enriched basaltic shergottite northwest africa 8657 abstract apatite a major hydrous mineral in martian meteorites has the potential to reveal history of volatiles on mars here we report the h and cl isotopic systematics of apatite from the enriched basaltic shergottite nwa 8657 to better understand the processes influencing volatiles at or near the martian sub surface the apatite in nwa 8657 has the highest reported d value up to 6509 of any phosphates in martian meteorites the positive correlation between the h2o contents 72 2251 ppm and d values 3965 6509 as well as between the cl contents 1 28 6 17 wt and 37cl values 1 7 4 0 in nwa 8657 apatite are consistent with mixing between volatiles derived from the martian mantle and meteoric water fluid the d and 37cl enrichment of apatite in nwa 8657 implies isotopic exchange with sub surficial fluids during post crystallization hydrothermal event s plain language summary mars was probably a wet and warm world during its earliest geological history supported by many lines of evidence present day mars is cold and arid although recent remote sensing data support the existence of subsurface glaciers and seasonal fluid activities at some locations in this study our aim was to use ground truth about the potential water rock interaction on or near surface environments on recent mars via measuring the h and cl isotopic compositions of apatite from a geologically young meteorite from mars the enriched basaltic shergottite nwa 8657 the petrography and mineral chemistry of apatite and other associated phases e g merrillite maskelynite mesostasis and pyroxene were documented prior to in situ h and cl isotopes analysis the water contents of apatite merrillite maskelynite mesostasis and pyroxene are positively correlated with the d values all of the datasets can be reconciled in terms of mixing between two endmembers a d poor 0 mantle reservoir and a d rich 5920 500 near surface underground water reservoir moreover apatite in nwa 8657 displays 37cl enriched 1 1 in average characteristics these signatures are consistent with d and 37cl rich fluid assisted isotopic exchange in recent near surface environment on mars

various aspects of the petrogenesis of the martian shergottite meteorites several controversies are associated with the age and origin of the shergottite meteorites a suite of basaltic samples from mars here it will be argued that 1 the shergottites have a young igneous age 600 myr 2 their parent magmas were relatively dry 3 the range of initial isotopic compositions in shergottites is most likely due to assimilation of crustal materials by mantle derived basaltic magmas and 4 the intercumulus liquid compositions of shergottites such as shergotty and zagami are relatively well constrained

the origin of alteration orangettes in dhofar 019 implications for the age and aqueous history of the shergottites the shergottites are the largest group of martian meteorites and the only group that has not been found to contain definitive evidence of martian aqueous alteration given recent reports of current liquid water at the surface of mars this study aimed to investigate in detail the possibility of martian phyllosilicate within shergottite dhofar 019 optical and scanning electron microscopy followed by transmission electron microscopy confirmed the presence of alteration orangettes with a layered structure consisting of poorly ordered mg phyllosilicate and calcite these investigations identified maskelynite dissolution followed by mg phyllosilicate and calcite deposition within the dissolution pits as the method of orangette production the presence of celestine within the orangette layers the absence of shock dislocation features within calcite and the mg rich nature of the phyllosilicate all indicate a terrestrial origin for these features on dhofar 019

assessment of shock effects on amphibole water contents and hydrogen isotope compositions 1 amphibolite experiments abstract kaersutitic amphiboles found within a subset of the martian meteorites have low water contents and variably heavy hydrogen isotope compositions in order to assess if impact shock induced devolatilization and hydrogen isotope fractionation were determining factors in these water and isotopic characteristics of the martian kaersutites we conducted impact shock experiments on samples of gore mountain amphibolite in the ames vertical gun range avgr a parallel shock experiment conducted on an anorthosite sample indicated that contamination of shocked samples by the avgr hydrogen propellant was unlikely petrographic study of the experimental amphibolite shock products indicates that only 10 of the shock products experienced levels of damage equivalent to those found in the most highly shocked kaersutite bearing martian meteorites 30 35 gpa ion microprobe studies of highly shocked hornblende from the amphibolite exhibited elevated water contents h 2 o 0 1 wt and enriched hydrogen isotope compositions d 10 relative to unshocked hornblende water and hydrogen isotope analyses of tens of milligrams of unshocked moderately shocked and highly shocked hornblende samples by vacuum extraction uranium reduction and isotope ratio mass spectrometry irms respectively are largely consistent with analyses of single grains from the ion microprobe the mechanisms thought to have produced the excess water in most of the shocked hornblendes are shock induced reduction of hornblende fe and or irreversible adsorption of hydrogen addition of the isotopically enriched martian atmosphere to the martian meteorite kaersutites via these mechanisms could explain their enriched and variable isotopic compositions alternatively regrouping the water extraction and irms analyses on the basis of isotopic composition reveals a small but consistent degree of impact induced devolatilization 0 1 wt h 2 o and h isotope enrichment d 10 extrapolating the shock signature of the regrouped data to grains that experienced martian meteorite like shock pressures suggests that shock induced water losses and hydrogen isotope enrichments could approach 1 wt h 2 o and d 100 respectively if these values are valid then impact shock effects could explain a substantial fraction of the low water contents and variable hydrogen isotope compositions of the martian meteorite kaersutites

analysis of fluvial suspended sediment load contribution through anthropocene history to the south atlantic bight coastal zone u s a abstract discerning the effects of anthropogenic activities i e reservoir construction land use change as opposed to those of natural processes i e climate variability on suspended sediment flux has become an increasingly difficult challenge this contribution presents water and suspended sediment flux from five major watersheds that discharge into the southeastern u s atlantic a region that is currently considered sediment starved three periods of anthropocene time were defined and evaluated 1 pre european conditions 1680 1700 2 pre dam conditions 1905 1925 and 3 post dam conditions 1985 2005 physical and hydrologic watershed data were used to run a climate driven hydrological transport numerical model hydrotrend to estimate suspended sediment flux for each period results indicate that the suspended sediment contribution to the south atlantic bight coastal zone increased by up to 145 as a result of accelerated soil erosion conditions caused by the arrival of europe

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

resurfacing of titan by ammonia water cryomagma the cassini titan radar mapper observed on titan several large features interpreted as cryovolcanic during the october 26 2004 pass at high northern latitudes lopes r m c and 43 colleagues 2007 icarus 186 395 412 to date models of ammonia water resurfacing have not been tied to specific events or evolutionary stages of titan we propose a model of cryovolcanism that involves cracking at the base of the ice shell and formation of ammonia water pockets in the ice as these ammonia water pockets undergo partial freezing in the cold ice shell the ammonia concentration in the pockets increases decreasing the negative buoyancy of the ammonia water mixture if the ice shell is contaminated by silicates delivered in impacts the liquid solid density difference would be even less while the liquid cannot easily become buoyant relative to the surrounding ice these concentrated ammonia water pockets are sufficiently close to the neutral buoyancy point that large scale tectonic stress patterns tides non synchronous rotation satellite volume changes solid state convection or subsurface pressure gradients associated with topography would enable the ammonia to erupt effusively onto the surface rather than suggesting steady state volcanism over the history of the solar system we favor a scenario where the cryovolcanic features could have been associated with episodic potentially late geological activity

timing of optical maturation of recently exposed material on ceres on ceres multispectral imaging data from the dawn spacecraft show a distinct bluish characteristic for recently exposed material from the subsurface in for example crater ejecta ejecta blankets of presumably old craters show a more reddish spectrum we selected areas in which fresh material from the cerean subsurface was exposed at a specific time in the past and no later geologic process is expected to have changed its surface composition or its cratering record for each area we determined two color ratios and the crater retention age the measured color ratios show an exponential diminishment of the bluish characteristic over time although the cause of the color change remains uncertain the time dependent change in spectral properties is evident which could help identify the process

meteoritic evidence for a previously unrecognized hydrogen reservoir on mars abstract fluvial landforms on mars suggest that it was once warm enough to maintain persistent liquid water on its surface the transition to the present cold and dry mars is closely linked to the history of surface water yet the evolution of surficial water is poorly constrained based on in situ hydrogen isotope d h analyses of quenched and impact glasses in martian meteorites we provide evidence for the existence of a distinct but ubiquitous water ice reservoir d h 2 3 times earth s ocean water that lasted from at least the time when the meteorites crystallized 173 472 million years ago to the time they were ejected by impacts 0 7 3 3 million years ago but possibly much longer the origin of this reservoir appears to predate the current martian atmospheric water d h 5 6 times earth s ocean water and is unlikely to be a simple mixture of atmospheric and primordial water retained in the martian mantle d h earth s ocean water this reservoir could represent hydrated crust and or ground ice interbedded within sediments our results corroborate the hypothesis that a buried cryosphere accounts for a large part of the initial water budget of mars

new insight into lunar impact melt mobility from the lro camera 1 the lunar reconnaissance orbiter camera lroc is systematically imaging impact melt deposits in and around lunar craters at meter and sub meter scales these images reveal that lunar impact melts although morphologically similar to terrestrial lava flows of similar size exhibit distinctive features e g erosional channels although generated in a single rapid event the post impact mobility and morphology of lunar impact melts is surprisingly complex we present evidence for multi stage influx of impact melt into flow lobes and crater floor ponds our volume and cooling time estimates for the post emplacement melt movements noted in lroc images suggest that new flows can emerge from melt ponds an extended time period after the impact event

degassing at the soufriere hills volcano montserrat recorded in matrix glass compositions compositions of matrix glasses from the current eruption of soufriere hills volcano indicate that decompression driven crystallization results in 20 70 wt groundmass crystallization during eruption and variable degassing variations in crystallinity and volatile contents water and chlorine of matrix glasses are attributed to variations in extrusion rates and residence times in the lava dome residual water contents in pumice clasts 0 2 0 6 wt indicate minimum pressures of 1 1 3 7 mpa in 1997 vulcanian explosions residual water contents of 1 6 wt in a ballistic block ejected in sub plinian explosive activity on 17 september 1996 imply larger pressure drops similar to20 mpa variable residual water contents in dome samples are consistent with pressure variations of up to 9 mpa in the lava dome interior large variation in chlorine contents between lava blocks compared with explosion pumice clasts indicates that shallow level processes dominate degassing low melt chlorine contents of dome samples cannot be explained by open or closed system degassing especially when crystallization is taken into account instead heterogeneous chlorine leaching by circulation of groundwater vapour in the dome is proposed variable and elevated matrix glass deltad values can also be attributed to interaction with isotopically heavy surface waters hcl emission during the current eruption can be accounted for by cl loss from the melt consistent with the melt being undersaturated in chlorine

opaque minerals magnetic properties and paleomagnetism of the tissint martian meteorite we present a description of opaque minerals opaque mineral compositions magnetic properties and paleomagnetic record of the tissint heavily shocked olivine phyric shergottite that fell to earth in 2011 the magnetic mineralogy of tissint consists of about 0 6 wt of pyrrhotite and 0 1 wt of low ti titanomagnetite in the range ulvospinel 3 15 magnetite 85 97 the titanomagnetite formed on mars by oxidation exsolution of ulvospinel grains during deuteric alteration pyrrhotite is unusual with respect to other shergottites for its higher ni content and lower fe content iron deficiency is attributed by an input of regolith derived sulfur this pyrrhotite has probably preserved a metastable hexagonal monosulfide solution structure blocked at temperature above 300 c the paleomagnetic data indicate that tissint was magnetized following the major impact suffered by this rock while cooling at the surface of mars from a post impact equilibrium temperature of approximately 310 c in a stable magnetic field of about 2 t of crustal origin tissint is too weakly magnetic to account for the observed magnetic anomalies at the martian surface

carbonaceous chondrites as analogs for the composition and alteration of ceres the mineralogy and geochemistry of ceres as constrained by dawn s instruments are broadly consistent with a carbonaceous chondrite cm ci bulk composition differences explainable by ceres s more advanced alteration include the formation of mg rich serpentine and ammoniated clay a greater proportion of carbonate and lesser organic matter amounts of magnetite sulfide and carbon that could act as spectral darkening agents and partial fractionation of water ice and silicates in the interior and regolith ceres is not spectrally unique but is similar to a few other c class asteroids which may also have suffered extensive alteration all these bodies are among the largest carbonaceous chondrite asteroids and they orbit in the same part of the main belt thus the degree of alteration is apparently related to the size of the body although the ammonia now incorporated into clay likely condensed in the outer nebula we cannot presently determine whether ceres itself formed in the outer solar system and migrated inward or was assembled within the main belt along with other carbonaceous chondrite bodies

considerations for effusive cryovolcanism on europa the post galileo perspective 1 cryovolcanic resurfacing is a popular mechanism to explain relatively young surface units on icy satellites of jupiter saturn uranus and neptune prior to the galileo data acquired between 1996 and 2001 europa was thought to have undergone significant cryovolcanic resurfacing facilitated by a global ocean beneath the icy surface however close examination of galileo data at resolutions much better than those of voyager images show that many of the features previously thought to be cryovolcanic are commonly best explained by other formative mechanisms including tectonism and diapirism in this study i present an examination of the characteristics of a variety of europan surface features for which effusive cryovolcanism is a possible origin including apparently lobate flows certain elliptical to circular lenticulae and low lying smooth low albedo surfaces a review of cryovolcanic eruption theory together with galileo data analysis of europan surface geology and composition indicates that cryovolcanism is a viable though not unequivocal explanation for some of these features some constraints on cryomagma properties and lithospheric structure are offered for these cases the presence of small volume low viscosity effusions is supported by observations and modeling some positive relief lenticulae could represent more viscous effusions although diapirism may be a preferable explanation however strong evidence is lacking for cryovolcanic resurfacing on a large scale on the basis of our experience with galileo images of europa and ganymede voyager era inferences for widespread cryovolcanism on icy satellites may be overstated and will need to be carefully reexamined in the light of new data from upcoming spacecraft missions

olivine hydration in the deep upper mantle effects of temperature and silica activity 1 although water controls the biology and geology of the surface hydrogen is perhaps the most poorly constrained compositional variable in the bulk earth its concentration in the upper mantle appears to be controlled by its solubility as hydroxyl in the nominally anhydrous silicate phases olivine pyroxene garnet wadsleyite and ringwoodite here we describe a series of experiments showing that the solubility of h2o in olivine at 12 gpa increases with temperature to 8900 ppm by weight at 1250 c and decreases at higher temperature with the onset of melting sample characterization by infrared spectroscopy indicates that the primary hydration mechanism is the substitution of 2h for mg2 similar results obtained from samples coexisting with clinohumite low silica and with clinoenstatite high silica indicate that silica activity has minimal effect on hydration under these conditions single crystal x ray diffraction measurements constrain the volume of hydration and indicate significant m site vacancies hydrogen thus appears to become a geochemically compatible element as depths approach 400 km

an investigation of the bluish material on ceres the dwarf planet ceres shows spatially well defined regions which exhibit a negative blue spectral slope between 0 5 and 2 5 m comparisons with planetary bodies known to exhibit a blue slope and spectral properties of materials identified on ceres surface based on infrared wavelength signatures indicate the spectral changes could be related to physical properties of the surface material rather than variations in its composition the close association of bluish surface regions to fresh impact craters implies a possible relationship to an impact triggered alteration and or space weathering processes the bluish regions could be linked with blankets of ultra fine grains and partly amorphous phyllosilicates which form larger agglomerates due to the sticky behavior of impact induced phyllosilicate dust and or the amorphization of the ejecta material during the impact process space weathering processes micro meteoritic impacts temperature changes cause a reversal of the agglutination process and a re crystallization of the surface material with time resulting in a reddening of the spectral slope

laboratory shock emplacement of noble gases nitrogen and carbon dioxide into basalt and implications for trapped gases in shergottite eeta 79001 abstract basalt samples have been analyzed mass spectrometrically for shock implanted noble gases n2 and co2 after exposure to 20 60 gpa 200 600 kbar shock in the presence of 0045 3 0 atm of ambient gas isotopically labelled gases were used in some samples to distinguish implanted atmospheric gases from contaminant or indigenous gases abundances of emplaced gases varied linearly with ambient gas pressure for constant shock pressure and gas emplacement was most efficient in the range of 35 50 gpa shock pressure uncrushed samples shocked in this range gave emplacement efficiencies number densities of gases in shocked samples number densities in ambient gas of 2 0 6 7 for heavy noble gases and nitrogen while powdered samples with higher effective porosity yielded 40 50 efficiencies indicating that 50 of noble gases and nitrogen available in porespaces was emplaced no elemental or isotopic fractionation was detected with ar kr xe or n2 helium and in some samples ne were lost by diffusion subsequent to shock emplacement efficiencies for co2 averaged a factor of 1 8 0 2 greater than those of n2 and noble gases in 4 samples with 20 50 gpa shock and yielded 3 2 times greater efficiency in a sample shocked to 60 gpa enhanced co2 emplacement is thought to be due to reaction with silicate materials data from shergottite eeta 79001 glass may be consistent with co2 efficiencies a factor of 2 3 greater than noble gas efficiencies trapped gases in eeta 79001 glass were probably emplaced by shock however apparent emplacement efficiencies are somewhat higher than even shocked powder samples possible explanations for the difference include atmospheric overpressure at the time of shock trapping of gas already in vugs by intruding melt material or collapse of gas filled vugs to form gas laden glass inclusions not enough is yet known about the behavior of vugs under shock to discount the latter possibility

tectonic analysis of fracturing associated with occator crater abstract occator crater a ceres crater that hosts multiple bright spots on its floor has several sets of fractures associated with it a tectonic analysis of each of these fracture sets suggests that the concentric and radial fractures around the central pit and the concentric fractures high on the crater wall near the rim most likely formed due to well known impact cratering processes uplift of the crater floor due to magmatic injection is suggested to have resulted in the concentric floor fractures at the base of the crater wall as well as the cross cutting fractures in the lower part of the southwestern wall a mathematical analysis shows that a cryomagmatic plume diapir could have both reached the height necessary to cause fracturing within occator and that the stresses required are reasonable expansion a lobate flow from beneath is proposed to have formed those linear fractures associated with the vinalia faculae circumferential fractures surrounding occator appear to have formed due to the volumetric compaction of the ejecta blanket over the buried pre existing topography

effects of shock and martian alteration on tissint hydrogen isotope ratios and water content abstract the tissint meteorite a picritic shergottite fell to earth in morocco on the 18th of july 2011 and is only the fifth martian meteorite witnessed to fall hydrogen isotope ratios and water contents are variable within different minerals in tissint ringwoodite and shock melt pockets contain elevated d h ratios relative to terrestrial values d 761 4224 these high ratios in recrystallized phases indicate significant implantation of hydrogen from the d rich martian atmosphere during shock in contrast although olivine has detectable water abundances 230 485 ppm it exhibits much lower d h ratios d 88 to 150 suggesting this water was not implanted from the martian atmosphere the minimal terrestrial weathering experienced by tissint gives confidence that the olivine hosted water has a martian origin but its high concentration indicates direct inheritance from the parental melt is improbable especially given the low pressure of olivine crystallisation incorporation of a low d crustal fluid or deuteric alteration during crystallisation could explain the relatively high water contents and low d h ratios in tissint olivine

insights into the martian mantle the age and isotopics of the meteorite fall tissint the recent witnessed fall of the meteorite tissint represents the delivery of a pristine new sample from the surface of mars this meteorite provides an unprecedented opportunity to study a variety of aspects about the planet s evolution using the rb sr and sm nd isotopic systems we determined that tissint a depleted shergottite has a crystallization age of 574 20 ma an initial e 143 nd 42 2 0 5 and an initial 87 sr 86 sr 0 700760 11 these initial nd and sr isotopic compositions suggest that tissint originated from a mantle source on mars that is distinct from the source reservoirs of the other martian meteorites the known crystallization ages geochemical characteristics ejection ages and ejection dynamics of tissint and other similarly grouped martian meteorites suggest that they are likely derived from a source crater up to approximately 90 km in diameter with an age of approximately 1 ma that is located on terrain that is approximately 600 million years old

water in the martian interior evidence for terrestrial morb mantle like volatile contents from hydroxyl rich apatite in olivine phyric shergottite nwa 6234 abstract understanding the distribution and behavior of volatiles in martian magmas and the corresponding mantle provides crucial constraints on planetary properties such as mantle melting temperatures and melt production as well as the availability of magmatic fluids for any potential occurrences of life current evaluations of the pre eruptive volatile concentrations of martian magmas are based on analyses of hydrous minerals in martian meteorites such as apatite because they record the volatile content oh f cl and the halogen and water fugacities of their parental magmas estimates for the pre eruptive volatile contents of martian basaltic magmas range from nearly anhydrous to 2 wt h2o however these magmas may have potentially degassed upon eruption and or emplacement losing their magmatic water while retaining some halogens here we report apatite compositional data from the martian meteorite nwa 6234 an intermediate olivine phyric shergottite and calculate f2 cl2 h2o fugacity ratios for its parental magma apatites in nwa 6234 contain the highest observed oh f content among martian meteorites and importantly have volatile fugacity ratios similar to terrestrial basalts this suggests that the actual content of fluorine chlorine and water of the martian mantle parental to snc meteorites are higher than previously thought and are similar to the volatile content of the terrestrial mid ocean ridge basalt source region

mineralogy and temperature of crater haulani on ceres we investigate the region of crater haulani on ceres with an emphasis on mineralogy as inferred from data obtained by dawn s visible infrared mapping spectrometer vir combined with multispectral image products from the dawn framing camera fc so as to enable a clear correlation with specific geologic features haulani which is one of the youngest craters on ceres exhibits a peculiar blue visible to near infrared spectral slope and has distinct color properties as seen in multispectral composite images in this paper we investigate a number of spectral indices reflectance spectral slopes abundance of mg bearing and nh4 bearing phyllosilicates nature and abundance of carbonates which are diagnostic of the overall crater mineralogy plus a temperature map that highlights the major thermal anomaly found on ceres in addition for the first time we quantify the abundances of several spectral endmembers by using vir data obtained at the highest pixel resolution 0 1 km the overall picture we get from all these evidences in particular the abundance of na and hydrous na carbonates at specific locations confirms the young age of haulani from a mineralogical viewpoint and suggests that the dehydration of na carbonates in the anhydrous form na2co3 may be still ongoing

cryogenic flow features on ceres implications for crater related cryovolcanism craters on ceres such as haulani kupalo ikapati and occator show postimpact modification by the deposition of extended plains material with pits multiple lobate flows and widely dispersed deposits that form a diffuse veneer on the preexisting surface bright material units in these features have a negative spectral slope in the visible range making it appear bluish with respect to the grey toned overall surface of ceres we calculate the drop height to runout length ratio of several flow features and obtain a coefficient of friction of 0 1 the results imply higher flow efficiency for flow features on ceres than for similar features on other planetary bodies with similar gravity suggesting low viscosity material the special association of flow features with impact craters could either point to an impact melt origin or to an exogenic triggering of cryovolcanic processes

tissint martian meteorite a fresh look at the interior surface and atmosphere of mars tissint morocco is the fifth martian meteorite collected after it was witnessed falling to earth our integrated mineralogical petrological and geochemical study shows that it is a depleted picritic shergottite similar to eeta79001a highly magnesian olivine and abundant glass containing martian atmosphere are present in tissint refractory trace element sulfur and fluorine data for the matrix and glass veins in the meteorite indicate the presence of a martian surface component thus the influence of in situ martian weathering can be unambiguously distinguished from terrestrial contamination in this meteorite martian weathering features in tissint are compatible with the results of spacecraft observations of mars tissint has a cosmic ray exposure age of 0 7 0 3 million years consistent with those of many other shergottites notably eeta79001 suggesting that they were ejected from mars during the same event

tissintite ca na alsi2o6 a highly defective shock induced high pressure clinopyroxene in the tissint martian meteorite tissintite is a new vacancy rich high pressure clinopyroxene with a composition essentially equivalent to plagioclase it was discovered in maskelynite shocked plagioclase and is commonly observed included within or in contact with shock melt pockets in the tissint meteorite a depleted olivine phyric shergottite fall from mars the simple composition of tissintite an58 69 and its precursor plagioclase an59 69 together with the limited occurrence both spatially only in maskelynite less than 25 m of a shock melt pocket and in terms of bulk composition make tissintite a goldilocks phase it formed during a shock event severe enough to allow nucleation and growth of vacancy rich clinopyroxene from a melt of not too calcic and not too sodic plagioclase composition that was neither too hot nor too cold with experimental calibration these limitations on occurrence can be used to place strong constraints on the thermal history of a shock event the kinetics for nucleation and growth of tissintite are probably slower for more sodic plagioclase precursors so tissintite is most likely to occur in depleted olivine phyric shergottites like tissint and other highly shocked meteorites and lunar and terrestrial rocks that consistently contained calcic plagioclase precursors in the appropriate compositional range for a shock of given intensity tissintite ca 0 45 na 0 31 0 24 al 0 97 fe 0 03 mg 0 01 si 1 80 al 0 20 o6 is a c2 c clinopyroxene containing 42 60 mol of the ca eskola component by far the highest known the cell parameters are 9 21 17 a b 9 09 4 a c 5 20 2 a 109 6 9 v 410 8 a 3 z 4z 4 the density is 3 32 g cm 3 and we estimate a cell volume for the ca eskola end member pyroxene of 411 13 a 3 which is consistent with a previous estimate and therefore supports the importance of this component in clinopyroxenes from ultra high pressure metamorphic rocks from the earth s upper mantle at least in c2 c clinopyroxenes as sodic as tissintite the a and b cell parameters as a function of vacancy concentration intersect at 0 3 vacancies pfu much lower than the ca eskola end member 0 5 an inversion of anisotropy suggesting an elastic instability that drives clinopyroxene toward a disordered trigonal structure closely related to that of wadeite it may mark the boundary beyond which the breakdown of vacancy rich clinopyroxene to a wadeite structured phase stishovite becomes stable although this was not observed in tissint

hydrogen isotopic composition of the martian mantle inferred from the newest martian meteorite fall tissint the hydrogen isotopic composition of planetary reservoirs can provide key constraints on the origin and history of water on planets the sources of water and the hydrological evolution of mars may be inferred from the hydrogen isotopic compositions of mineral phases in martian meteorites which are currently the only samples of mars available for earth based laboratory investigations previous studies have shown that d values in minerals in the martian meteorites span a large range of 250 to 6000 the highest hydrogen isotope ratios likely represent a martian atmospheric component either interaction with a reservoir in equilibrium with the martian atmosphere such as crustal water or direct incorporation of the martian atmosphere due to shock processes the lowest d values may represent those of the martian mantle but it has also been suggested that these values may represent terrestrial contamination in martian meteorites here we report the hydrogen isotopic compositions and water contents of a variety of phases merrillites maskelynites olivines and an olivine hosted melt inclusion in tissint the latest martian meteorite fall that was minimally exposed to the terrestrial environment we compared traditional sample preparation techniques with anhydrous sample preparation methods to evaluate their effects on hydrogen isotopes and find that for severely shocked meteorites like tissint the traditional sample preparation techniques increase water content and alter the d h ratios toward more terrestrial like values in the anhydrously prepared tissint sample we see a large range of d values most likely resulting from a combination of processes including magmatic degassing secondary alteration by crustal fluids shock related fractionation and implantation of martian atmosphere based on these data our best estimate of the d value for the martian depleted mantle is 116 94 which is the lowest value measured in a phase in the anhydrously prepared section of tissint this value is similar to that of the terrestrial upper mantle suggesting that water on mars and earth was derived from similar sources the water contents of phases in tissint are highly variable and have been affected by secondary processes considering the h2o abundances reported here in the driest phases most likely representing primary igneous compositions and appropriate partition coefficients we estimate the h2o content of the tissint parent magma to be 0 2 wt

petrology and trace element geochemistry of tissint the newest shergottite fall the fall and recovery of the tissint meteorite in 2011 created a rare opportunity to examine a martian sample with a known short residence time on earth tissint is an olivine phyric shergottite that accumulated olivine antecrysts within a single magmatic system coarse olivine grains with nearly homogeneous cores of mg 80 suggest slow re equilibration many macroscopic features of this sample resemble those of lar 06319 including the olivine crystal size distribution and the presence of evolved oxide and olivine compositions unlike lar 06319 however no magmatic hydrous phases were found in the analyzed samples of tissint minor and trace element compositions indicate that the meteorite is the product of closed system crystallization from a parent melt derived from a depleted source with no obvious addition of a lree rich crustal component prior to or during crystallization the whole rock ree pattern is similar to that of intermediate olivine phyric shergottite eeta 79001 lithology a and could also be approximated by a more olivine rich version of depleted basaltic shergottite que 94201 magmatic oxygen fugacities are at the low end of the shergottite range with log fo2 of qfm 3 5 to 4 0 estimated based on early crystallized minerals and qfm 2 4 estimated based on the eu in pyroxene oxybarometer these values are similarly comparable to other depleted shergottites including sau 005 and que 94201 tissint occupies a previously unsampled niche in shergottite chemistry containing olivines with mg 80 resembling the enriched olivine phyric shergottite lar 06319 in its crystallization path and comparable to intermediate olivine phyric shergottite eeta 79001a depleted olivine phyric shergottite dag 476 and depleted basaltic shergottite que 94201 in its trace element abundances and oxygen fugacity the apparent absence of evidence for terrestrial alteration in tissint particularly in trace element abundances in the whole rock and individual minerals confirms that exposure to the arid desert environment results in only minimal weathering of samples provided the exposure times are brief

ceres evolution and current state 1 we modeled several thermal evolution scenarios for ceres to explore the nature of large wet protoplanets and to predict current day evidence that might be found by close inspection such as by the dawn mission the density for ceres is near 2 1 suggesting a water content between 17 and 27 by mass short and long lived radioactive nuclide heating is considered even if only long lived radionuclide heating is assumed the water ice in ceres melts quickly and a water mantle forms but an approximately 10 km crust does not melt the circulating warm water would alter the silicates as heat is lost by conduction through the frozen crust water begins to freeze out at the base of the crust solid state convection begins and transports more heat as well as perhaps material dissolved or entrained in the water to or near the surface ceres water layer eventually but perhaps not entirely freezes forming a layered density structure with perhaps some liquid water remaining today our differentiated models are in agreement with the recently measured difference between the equatorial and polar radii we find that ceres existence and evolution depend critically on it containing water at formation and this depends strongly on the combination of when it accreted and the amount of 26al present in the pre ceres 1 km sized objects slightly more 26al or earlier accretion produces a dry vesta like object melting and freezing plus mineralization would lead to several dimensional changes over time creating topographic features zones of weakness and perhaps disruptions in the crust

origin of small pits in martian impact craters we propose a numerical model for the formation of the closely spaced pits found in the thin ejecta related deposits superposed on the floors interior terrace blocks and near rim ejecta blankets of well preserved martian impact craters our model predicts the explosive degassing of water from this pitted material which is assumed to originally be water bearing impact melt rich breccia at the time of deposition this process is analogous to what occurred in the fall out suevite deposits at the ries impact structure in germany at ries impact heating of water bearing target material resulted in the rapid degassing of its water and other volatiles the martian environment plays an important role in enhancing the effects of this degassing by increasing the flow speed of the escaping gas the high flow rate of gas through particulate materials such as suevite tends to quickly form segregation channels or vent pipes similar to those found in the ries deposits these pipes act as conduits for the efficient high speed escape of the gas and small clasts that it entrains escaping gas and entrained clasts abraded and eroded the conduit walls flaring them to form pits above a network of pipes

petrology and shock metamorphism of the olivine phyric shergottite yamato 980459 evidence for a two stage cooling and a single stage ejection history abstract the basaltic martian meteorite yamato 980459 consists of large olivine phenocrysts and often prismatic pyroxenes set into a fine grained groundmass of smaller more fe rich olivine chromite and an interstitial residual material displaying quenching textures of dendritic olivine chain like augite and sulfide droplets in a glassy matrix yamato 980459 is thus the only martian meteorite without plagioclase maskelynite olivine is compositionally zoned from a mg rich core to a fe rich rim with the outer few micrometers being especially rich in iron with fo84 the cores are the most magnesian olivines found in martian meteorites so far pyroxenes are also mostly composite crystals of large orthopyroxene cores and thin ca rich overgrowths separate pigeonite and augites are rare on basis of the mineral compositions the cooling rates determined from crystal morphologies and crystal grain size distributions it is deduced that the parent magma of yamato 980459 initially cooled under near equilibrium conditions e g in a magma chamber allowing chromite and the mg rich silicates to form as cumulus phases fractional crystallization at higher cooling rates and a low degree of undercooling let to the formation of the ca al and fe rich overgrowths on olivine and orthopyroxene while the magma was ascending towards the martian surface finally and before plagioclase and also phosphates could precipitate the magma was very quickly erupted quenching the remaining melt to glass dendritic silicates and sulfide droplets the shape preferred orientation of olivine and pyroxene suggests a quick thin outflow of lava according to the shock effects found in the minerals of yamato 980459 the meteorite experienced an equilibration shock pressure of about 20 25 gpa its near surface position allowed the ejection from the planet s surface already by a single impact event and at relatively low shock pressures

igneous and shock processes affecting chassignite amphibole evaluated using chlorine water partitioning and hydrogen isotopes amphibole in chassignite melt inclusions provides valuable information about the volatile content of the original interstitial magma but also shock and postshock processes we have analyzed amphibole and other phases from nwa 2737 melt inclusions and we evaluate these data along with published values to constrain the crystallization cl and h2o content of phases in chassignite melt inclusions and the effects of shock on these amphibole grains using a model for the cl oh exchange between amphibole and melt we estimate primary crystallization oh contents of chassignite amphiboles sims analysis shows that amphibole from nwa 2737 currently has 0 15 wt h2o it has lost 0 6 wt h2o from an initial 0 7 0 8 wt h2o due to intense shock chassigny amphibole had on average 0 3 0 4 wt h2o and suffered little net loss of h2o due to shock nwa 2737 amphibole has d 3700 it absorbed martian atmosphere derived heavy h in the aftermath of shock chassigny amphibole with d 1900 incorporated less heavy h low h2o cl ratios are inferred for the primitive chassignite magma which had significant effects on melting and crystallization volatiles released by the degassing of martian magma were more cl rich than on earth resulting in the high cl content of martian surface materials

mobility of large rock avalanches evidence from valles marineris mars measurements of h l height of drop length of runout vs volume for landslides in valles marineris on mars show a trend of decreasing h l with increasing volume this trend which is linear on a log log plot is parallel to but lies above the trend for terrestrial dry rock avalanches this result and estimates of 10 4 to 10 5 pa yield strength suggest that the landslides were not water saturated as suggested by previous workers the offset between the h l vs volume trends shows that a typical martian avalanche must be nearly two orders of magnitude more voluminous than a typical terrestrial avalanche in order to achieve the same mobility this offset might be explained by the effects of gravity on flows with high yield strengths these results should prove useful to future efforts to resolve the controversy over the mechan ics of long runout avalanches

on the resurfacing of ganymede by liquid water volcanism abstract a long popular model for producing ganymede s bright terrain involves flooding of low lying graben with liquid water slush or warm soft ice the model suffers from major problems however including the absence of obvious near surface heat sources the negative buoyancy of liquid water and the lack of a mechanism for confining the flows to graben floors we present new models for cryovolcanic resurfacing to overcome these difficulties tidal heating within an ancient laplace like orbital resonance showman and malhotra 1997 icarus 127 93 showman et al 1997 icarus 129 367 provides a plausible heat source and could allow partial melting to occur as shallow as 5 10 km depth our favored mechanism for delivering this water to the surface invokes the fact that topography such as a global set of graben causes subsurface pressure gradients that can pump water or slush upward onto the floors of topographic lows graben despite the negative buoyancy of the liquid these eruptions can occur only within the topographic lows furthermore as the low areas become full the pressure gradients disappear and the resurfacing ceases this provides an explanation for the observed straight dark bright terrain boundaries water cannot overflow the graben so resurfacing rarely embays craters or other rough topography pure liquid water can be pumped to the surface from only 5 10 km depth but macroscopic bodies of slush ascending within fractures can reach the surface from much greater depths due to the smaller negative buoyancy of slush a challenge for these models is the short predicted gravitational relaxation timescale of topographic features at high heat flows the resurfacing must occur before the graben topography disappears we also evaluate alternate resurfacing mechanisms such as pumping of liquid water to the surface by thermal expansion stresses and buoyant rise of water through a silicate contaminated crust that is denser than liquid water and conclude that they are unlikely to explain ganymede s bright terrain

heterogeneous mineral assemblages in martian meteorite tissint as a result of a recent small impact event on mars the microtexture and mineralogy of shock melts in the tissint martian meteorite were investigated using scanning electron microscopy raman spectroscopy transmission electron microscopy and synchrotron micro x ray diffraction to understand shock conditions and duration distinct mineral assemblages occur within and adjacent to the shock melts as a function of the thickness and hence cooling history the matrix of thin veins and pockets of shock melt consists of clinopyroxene ringwoo dite stishovite embedded in glass with minor fe sulfide the margins of host rock olivine in contact with the melt as well as entrained olivine fragments are now amorphosed silicate perovskite magnesiowustite or clinopyroxene magnesiowustite the pressure stabilities of these mineral assemblages are 15 gpa and 19 gpa respectively the 200 lm wide margin of a thicker mm size up to 1 4 mm shock melt vein contains clinopyroxene olivine with central regions comprising glass vesicles fe sulfide spheres fragments of host rock within the melt are polycrystalline olivine after olivine and tis sintite glass after plagioclase from these mineral assemblages the crystallization pressure at the vein edge was as high as 14 gpa the interior crystallized at ambient pressure the shock melts in tissint quench crystallized during and after release from the peak shock pressure crystallization pressures and those determined from olivine dissociation therefore represent the minimum shock loading shock deformation in host rock minerals and complete transformation of plagioclase to maskelynite suggest the peak shock pressure experienced by tissint p 29 30 gpa these pressure estimates support our assessment that the peak shock pressure in tissint was significantly higher than the minimum 19 gpa required to transform olivine to silicate perovskite plus magnesiowustite small volumes of shock melt 100 lm quench rapidly 0 01 s whereas thermal equilibration will occur within 1 2 s in larger volumes of melt 1 mm 2 the apparent variation in shock pressure recorded by variable mineral assemblages within and around shock melts in tissint is consistent with a shock pulse on the order of 10 20 ms combined with a longer duration of post shock cooling and complex thermal history this implies that the impact on mars that shocked and ejected tissint at 1 ma was not exceptionally large

the vanishing cryovolcanoes of ceres ahuna mons is a 4 km tall mountain on ceres interpreted as a geologically young cryovolcanic dome other possible cryovolcanic features are more ambiguous implying that cryovolcanism is only a recent phenomenon or that other cryovolcanic structures have been modified beyond easy identification we test the hypothesis that cerean cryovolcanic domes viscously relax precluding ancient domes from recognition we use numerical models to predict flow velocities of ahuna mons to be 10 500 m myr depending upon assumptions about ice content rheology grain size and thermal parameters slower flow rates in this range are sufficiently fast to induce extensive relaxation of cryovolcanic structures over 108 109 years but gradual enough for ahuna mons to remain identifiable today positive topographic features including a tholus underlying ahuna mons may represent relaxed cryovolcanic structures a composition for ahuna mons of 40 ice explains the observed distribution of cryovolcanic structures because viscous relaxation renders old cryovolcanoes unrecognizable

hydrogen isotope analyses of alteration phases in the nakhlite martian meteorites abstract secondary alteration phases such as carbonates smectite clays and fe oxides are found within the martian meteorites if these meteorites were seen to fall the assumption can be reasonably made that the secondary phases have a martian origin however for martian meteorite finds this is not the case deuterium hydrogen d h ratio analysis can be used to distinguish between terrestrial and martian secondary alteration phases the martian atmosphere is currently five times enriched in deuterium compared to terrestrial seawater producing a deuterium enrichment in the martian alteration phases large enough to be detected with modern ion microprobe techniques we aimed to measure the d h ratio of the iddingsite like alteration veins in the nakhlite martian meteorites nakhla mil 03346 mil 090030 and y 000593 to help confirm the martian origin of this material and determine the relative amounts of terrestrial contamination in each meteorite as an observed fall nakhla is nominally uncontaminated by terrestrial alteration and shows elevated d values in its alteration veins however even the highest of these values is much below that of the martian atmosphere indicating that terrestrial contamination probably combined with fractionation effects between the martian atmosphere and the alteration material have reduced the d values of these veins the speed of hydrogen isotope exchange in the nakhlite iddingsite like alteration veins is demonstrated by the purely terrestrial d values in the veins of nakhla 110 a thin section exposed to the terrestrial atmosphere since its preparation in 1998 mineralogical heterogeneity also affects the hydrogen isotope exchange rate in these veins the wide variation in d within the veins of nakhla and y 000593 appears to be due to the heterogeneous nature of the vein material where some phases exchange hydrogen with the atmosphere at a faster rate than others

the unique geomorphology and structural geology of the haulani crater of dwarf planet ceres as revealed by geological mapping of equatorial quadrangle ac 6 haulani abstract the dwarf planet ceres has been explored by nasa s dawn spacecraft with the goal of characterizing its geology mineralogy topography shape and internal structure one outcome of this exploration is the production of geologic maps meant to unveil the geologic history of ceres in this paper we present the geologic map of the ac 6 haulani quadrangle lat 22 s 22 n long 0 72 e based on low altitude mapping orbit lamo 35 m pixel data supplemented with color and spectral data as well as a digital terrain model from the high altitude mapping orbit hamo 135 m pixel vertical accuracy of about 10 m the 34 km diameter haulani crater is one of the youngest features on ceres and the most prominent one in the quadrangle haulani was formed on a topographical transition in north south direction and shows a complex morphology with a variety of lobate flows and tectonic features multiple cracks and depressions around the crater indicate the failure of subsurface material these were likely formed by the subsidence of material due to the instability of the subsurface the mapping of ac 6 haulani suggests that ceres is built up of layers with different material properties we propose that ceres has a solid crust and a variable ice rich subsurface consistent with previous and recent models of ceres interior

heterogeneous distribution of h2o in the martian interior implications for the abundance of h2o in depleted and enriched mantle sources we conducted a petrologic study of apatite within 12 martian meteorites including 11 shergottites and one basaltic regolith breccia these data were combined with previously published data to gain a better understanding of the abundance and distribution of volatiles in the martian interior apatites in individual martian meteorites span a wide range of compositions indicating they did not form by equilibrium crystallization in fact the intrasample variation in apatite is best described by either fractional crystallization or crustal contamination with a cl rich crustal component we determined that most martian meteorites investigated here have been affected by crustal contamination and hence cannot be used to estimate volatile abundances of the martian mantle using the subset of samples that did not exhibit crustal contamination we determined that the enriched shergottite source has 36 73 ppm h2o and the depleted source has 14 23 ppm h2o this result is consistent with other observed geochemical differences between enriched and depleted shergottites and supports the idea that there are at least two geochemically distinct reservoirs in the martian mantle we also estimated the h2o cl and f content of the martian crust using known crust mantle distributions for incompatible lithophile elements we determined that the bulk martian crust has 1410 ppm h2o 450 ppm cl and 106 ppm f and cl and h2o are preferentially distributed toward the martian surface the estimate of crustal h2o results in a global equivalent surface layer gel of 229 m which can account for at least some of the surface features on mars attributed to flowing water and may be sufficient to support the past presence of a shallow sea on mars surface

nanosims analyses of apatite and melt inclusions in the grv 020090 martian meteorite hydrogen isotope evidence for recent past underground hydrothermal activity on mars abstract we measured the hydrogen isotopes and water contents of melt inclusions and apatite that locate far from shock induced melt veins in the martian meteorite grv 020090 using nano scale secondary ion mass spectrometry nanosims the melt inclusions in olivine show hydration profiles with both the water contents and the d values increasing from the cores 2 170 7 ppm and 3386 126 to the rims 5337 200 ppm and 5519 65 the extremely high d values of the melt inclusions relative to a maximum of 4239 81 of apatite that crystallized from the last residual melt convincingly argue that the observed hydration postdated emplacement of the parent magma of grv 020090 this is also a robust line of evidence for past presence of liquid water on mars diffusion simulation of the hydration profiles of both water contents and d values constrains the duration of liquid water up to 130 000 250 000 years at 0 c or 700 1 500 years at 40 c all analyses of the melt inclusions including the hydration profiles show a logarithmic correlation between the water contents and the d values plotting within a two endmember mixing area the extremely d enriched endmember represents martian underground water with a d value of 6034 72 2 this is the highest d value reported in martian meteorites and it is consistent with the recent analyses of martian soils by the curiosity rover leshin et al 2013 suggestive of more water escaped from mars than previous estimates the analyses of apatite show a distinct positive correlation between the water contents 0 10 0 58 wt and the d values 737 4239 which can be explained by assimilation of d rich martian crustal materials and enhancement of water via fractional crystallization the observed correlation suggests that the water contents of martian mantle reservoirs might have been overestimated from d enriched apatite in previous studies our estimation based on the least contaminated apatite grains from grv 020090 turned out a low water content of the primordial parent magma 380 750 ppm which was likely derived from a relatively dry martian mantle reservoir of grv 020090 38 75 ppm h2o

apatite as a probe of halogen and water fugacities in the terrestrial planets abstract apatite preserves a record of the halogen and water fugacities that existed during the waning stages of crystallization of planetary magmas when they became saturated in phosphates we develop a thermodynamic formalism based on apatite merrillite equilibria that makes it possible to compare the relative values of halogen and water fugacities in martian lunar and terrestrial basalts accounting for possible differences in pressure temperature and oxygen fugacities among the planets we show that each of these planetary bodies has distinctive ratios among volatile fugacities at apatite saturation and that these fugacities are in some cases related in a consistent way to volatile fugacities in the mantle magma sources our analysis shows that the martian mantle parental to basaltic snc meteorites was dry and poor in both fluorine and chlorine compared to the terrestrial mantle the limited data available from mars show no secular variation in mantle halogen and water fugacities from 4 ga to 180 ma the water and halogens found in present day martian surface rocks have thus resided in the planet s surficial systems since at least 4 ga and may have been degassed from the planet s interior during a primordial crust forming event in comparison to the earth and mars the moon and possibly the eucrite parent body too appear to be strongly depleted not only in h 2 o but also in cl 2 relative to h 2 o chlorine depletion is strongest in mare basalts perhaps reflecting an eruptive process characteristic of large scale lunar magmatism

influence of varying tidal prism on hydrodynamics and sedimentary processes in a hypertidal salt marsh creek recent initiatives directing tidal power development in the bay of fundy have raised questions about far field environmental impacts related to energy extraction it is understood that commercial scale tidal power installations in the minas passage will result in an overall decrease in tidal amplitude in the minas basin corresponding changes in sedimentation patterns may or may not be within the natural range of variability and it is hypothesized that intertidal sedimentation rates will demonstrate a non linear response to modification of the tidal energy regime this research considers acoustic doppler velocimeter adv and optical backscatter sensor obs data from a sheltered tidal creek in the minas basin for analysis of tidal characteristics in a hypertidal creek environment over spring and neap tidal cycles sediment deposition in the creek was also measured results show a first order control of topography on flow magnitude in the tidal creek which impacts net sediment deposition through resuspension and removal of newly introduced material this study demonstrates that tides which peak around the bankfull level show reduced early ebb stage turbulence and flow velocity and encourage an extended depositional period the dynamics of marshfull tides may be responsible for the maximum sediment deposition in tidal creeks providing large amounts of material that is eventually distributed to and deposited on marsh surfaces copyright 2012 john wiley sons ltd