New materials for high temperature turbines; ONERA's DS composites confronted with blade problems

ONERA's refractory DS composites were cited as materials required for use in advanced aircraft turbines, operating at high temperatures. These materials were found to be reliable in the construction of turbine blades. Requirements for a blade material in aircraft turbines operating at higher temperatures were compared with the actual performance as found in COTAC DS composite testing. The structure and properties of the more fully developed 74 and 741 types were specified. High temperature structural stability, impact of thermal and mechanical fatigue, oxidation resistance and coating capability were thoroughly evaluated. The problem of cooling passages in DS eutectic blades is also outlined

Composition, Morphology, and Stratigraphy of Noachian Crust around the Isidis basin

Definitive exposures of pristine, ancient crust on Mars are rare, and the finding that much of the ancient Noachian terrain on Mars exhibits evidence of phyllosilicate alteration adds further complexity. We have analyzed high-resolution data from the Mars Reconnaissance Orbiter in the well-exposed Noachian crust surrounding the Isidis basin. We focus on data from the Compact Reconnaissance Imaging Spectrometer for Mars as well as imaging data sets from High Resolution Imagine Science Experiment and Context Imager. These data show the lowermost unit of Noachian crust in this region is a complex, brecciated unit of diverse compositions. Breccia blocks consisting of unaltered mafic rocks together with rocks showing signatures of Fe/Mg-phyllosilicates are commonly observed. In regions of good exposure, layered or banded phyllosilicate-bearing breccia rocks are observed suggestive of pre-Isidis sedimentary deposits. In places, the phyllosilicate-bearing material appears as a matrix surrounding mafic blocks, and the mafic rocks show evidence of complex folded relationships possibly formed in the turbulent flow during emplacement of basin-scale ejecta. These materials likely include both pre-Isidis basement rocks as well as the brecciated products of the Isidis basin–forming event at 3.9 Ga. A banded olivine unit capped by a mafic unit covers a large topographic and geographic range from northwest of Nili Fossae to the southern edge of the Isidis basin. This olivine-mafic cap combination superimposes the phyllosilicate-bearing basement rocks and distinctly conforms to the underlying basement topography. This may be due to draping of the topography by a fluid or tectonic deformation of a previously flatter lying morphology. We interpret the draping, superposed olivine-mafic cap combination to be impact melt from the Isidis basin–forming event. While some distinct post-Isidis alteration is evident (carbonate, kaolinite, and serpentine), the persistence of olivine from the time of Isidis basin suggests that large-scale aqueous alteration processes had ceased by the time this unit was emplaced

Testing evidence of recent hydration state change in sulfates on Mars

The East Candor Interior Layered Deposit (ILD) has signatures of mono‐ and polyhydrated sulfate in alternating layers that give insight into the processes which formed these layered deposits and on the environmental conditions acting on them since then. We use orbital data to explore multiple hypotheses for how these deposits formed: (1) sulfate‐bearing ILDs experience hydration changes on seasonal to a few years timescales under current Mars environmental conditions; (2) the deposits experience hydration under recent Mars conditions but require the wetter climate of high obliquity; and (3) the kieserite could be an original or diagenetic part of a complex evaporite mineral assemblage. Modeled climatology shows recent Mars environmental conditions might pass between multiple sulfate fields. However, comparison of Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) and Compact Reconnaissance Imaging Spectrometer (CRISM) observations of the same ILD do not show changes in hydration over 2 Mars years. Low temperatures might slow the kinetics of that transition; it is likely that more clement conditions during periods of high obliquity are needed to overcome mineral metastability and hydrate kieserite‐bearing deposits. We find the alternate model, that the deposit is a cyclic evaporite sequence of mono‐ and polyhydrated sulfates, also plausible but with an unexplained dearth of Fe sulfates

Sequestration of Martian CO2 by mineral carbonation

Carbonation is the water-mediated replacement of silicate minerals, such as olivine, by carbonate, and is commonplace in the Earth’s crust. This reaction can remove significant quantities of CO2 from the atmosphere and store it over geological timescales. Here we present the first direct evidence for CO2 sequestration and storage on Mars by mineral carbonation. Electron beam imaging and analysis show that olivine and a plagioclase feldspar-rich mesostasis in the Lafayette meteorite have been replaced by carbonate. The susceptibility of olivine to replacement was enhanced by the presence of smectite veins along which CO2-rich fluids gained access to grain interiors. Lafayette was partially carbonated during the Amazonian, when liquid water was available intermittently and atmospheric CO2 concentrations were close to their present-day values. Earlier in Mars’ history, when the planet had a much thicker atmosphere and an active hydrosphere, carbonation is likely to have been an effective mechanism for sequestration of CO2

The moon as a recorder of organic evolution in the early solar system: a lunar regolith analog study

The organic record of Earth older than ∼3.8 Ga has been effectively erased. Some insight is provided to us by meteorites as well as remote and direct observations of asteroids and comets left over from the formation of the Solar System. These primitive objects provide a record of early chemical evolution and a sample of material that has been delivered to Earth's surface throughout the past 4.5 billion years. Yet an effective chronicle of organic evolution on all Solar System objects, including that on planetary surfaces, is more difficult to find. Fortunately, early Earth would not have been the only recipient of organic matter–containing objects in the early Solar System. For example, a recently proposed model suggests the possibility that volatiles, including organic material, remain archived in buried paleoregolith deposits intercalated with lava flows on the Moon. Where asteroids and comets allow the study of processes before planet formation, the lunar record could extend that chronicle to early biological evolution on the planets. In this study, we use selected free and polymeric organic materials to assess the hypothesis that organic matter can survive the effects of heating in the lunar regolith by overlying lava flows. Results indicate that the presence of lunar regolith simulant appears to promote polymerization and, therefore, preservation of organic matter. Once polymerized, the mineral-hosted newly formed organic network is relatively protected from further thermal degradation. Our findings reveal the thermal conditions under which preservation of organic matter on the Moon is viable

Hypotheses for the Origin of the Hypanis Fan-Shaped Deposit at the Edge of the Chryse Escarpment, Mars: Is it a Delta?

We investigated the origin of the fan-shaped deposit at the end of Hypanis Valles that has previously been proposed as an ExoMars, Mars 2020, and human mission candidate landing site, and found evidence that the landform is an ancient delta. Previous work suggests that the deposit originated from a time of fluvial activity both distinct from and prior to catastrophic outflow, and crater counting placed the deposit’s age at  ≥ 3.6 Ga. We found over 30 thin sedimentary strata in the proposed delta wall, and from our slope analysis conclude that the fluvial sequence is consistent with a lowering/retreating shoreline. We measured nearly horizontal bedding dip angles ranging from 0° to 2° over long stretches of cliff and bench exposures seen in HiRISE images and HiRISE stereo DTMs. From THEMIS night IR images we determined that the fan-shaped deposit has a low thermal inertia (150-240 Jm-2 K-1 s-1/2) and the surrounding darker-toned units correspond to thermal inertia values as high as 270-390 Jm-2 K-1 s-1/2. We interpret these findings to indicate that the fan-shaped deposit consists mostly of silt-sized and possibly finer grains, and that the extremely low grade and large lateral extent of these beds implies that the depositional environment was calm and relatively long-lived. We interpret the geomorphology and composition as incompatible with an alluvial fan or mudflow hypothesis. From our stratigraphic mapping we interpret the order of events which shaped the region. After the Chryse impact, sediment filled the basin, a confined lake or sea formed allowing a large delta to be deposited near its shoreline, the water level receded to the north, darker sedimentary/volcanic units covered the region and capped the light-toned deposit as hydro-volcanic eruptions shaped the interior of Lederberg crater, freeze/thaw cycles and desiccation induced local fracturing, and finally wrinkle ridges associated with rounded cones warped the landscape following trends in degraded crater rims and existing tectonic features. The ancient deltaic deposit we observe today was largely untouched by subsequent catastrophic outflows, and its surface has been only moderately reshaped by over 3 billion years of aeolian erosion

Influence of spacecraft outgassing on the exploration of tenuous atmospheres with in situ mass spectrometry

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94765/1/jgra20796.pd

The Main Belt Comets and ice in the Solar System

We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies

Origin of acidic surface waters and the evolution of atmospheric chemistry on early Mars

Observations from in situ experiments and planetary orbiters have shown that the sedimentary rocks found at Meridiani Planum, Mars were formed in the presence of acidic surface waters. The water was thought to be brought to the surface by groundwater upwelling, and may represent the last vestiges of the widespread occurrence of liquid water on Mars. However, it is unclear why the surface waters were acidic. Here we use geochemical calculations, constrained by chemical and mineralogical data from the Mars Exploration Rover Opportunity, to show that Fe oxidation and the precipitation of oxidized iron (Fe^(3+)) minerals generate excess acid with respect to the amount of base anions available in the rocks present in outcrop. We suggest that subsurface waters of near-neutral pH and rich in Fe^(2+) were rapidly acidified as iron was oxidized on exposure to O_2 or photo-oxidized by ultraviolet radiation at the martian surface. Temporal variation in surface acidity would have been controlled by the availability of liquid water, and as such, low-pH fluids could be a natural consequence of the aridification of the martian surface. Finally, because iron oxidation at Meridiani would have generated large amounts of gaseous H_2, ultimately derived from the reduction of H_2O, we conclude that surface geochemical processes would have affected the redox state of the early martian atmosphere

An Application of the Concept of the Therapeutic Alliance To Sadomasochistic Pathology

This paper traces the history of the therapeutic alliance concept, examining how it has been used and misused, at times elevated to a central position and at others rejected altogether. The loss of this concept created a vacuum in classical psychoanalysis that has been filled by rival theories. The continuing usefulness of looking at the treatment process through the lens of the therapeutic alliance, particularly in relation to the manifold difficulties of working with sadomasochistic pathology, is suggested. To this end, revisions of the theory of the therapeutic alliance are suggested to address some of the difficulties that have arisen in conceptualizing this aspect of the therapeutic relationship, and to provide an integrated dynamic model for working with patients at each phase of treatment. This revised model acknowledges the complexity of the domain and encompasses the multiple tasks, functions, partners, and treatment phases involved. The utility of the revised theory is illustrated in application to understanding the sadomasochistic, omnipotent resistances of a female patient through the phases of her analysis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66889/2/10.1177_00030651980460031301.pd