SPICES: spectro-polarimetric imaging and characterization of exoplanetary systems

SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) is a five-year M-class mission proposed to ESA Cosmic Vision. Its purpose is to image and characterize long-period extrasolar planets and circumstellar disks in the visible (450?C900 nm) at a spectral resolution of about 40 using both spectroscopy and polarimetry. By 2020/2022, present and near-term instruments will have found several tens of planets that SPICES will be able to observe and study in detail. Equipped with a 1.5 m telescope, SPICES can preferentially access exoplanets located at several AUs (0.5?C10?AU) from nearby stars (<25 pc) with masses ranging from a few Jupiter masses to Super Earths (??2 Earth radii, ??10 M_??) as well as circumstellar disks as faint as a few times the zodiacal light in the Solar System.     

A compromise aspect-adaptive cylindrical projection for world maps

There are two problems with current cylindrical projections for world maps. First, existing cylindrical map projections have a static height-to-width aspect ratio and do not automatically adjust their aspect ratio in order to optimally use available canvas space. Second, many of the commonly used cylindrical compromise projections show areas and shapes at higher latitudes with considerable distortion. This article introduces a new compromise cylindrical map projection that adjusts the distribution of parallels to the aspect ratio of a canvas. The goal of designing this projection was to show land masses at central latitudes with a visually balanced appearance similar to how they appear on a globe. The projection was constructed using a visual design procedure where a series of graphically optimized projections was defined for a select number of aspect ratios. The visually designed projections were approximated by polynomial expressions that define a cylindrical projection for any height-to-width ratio between 0.3:1 and 1:1. The resulting equations for converting spherical to Cartesian coordinates require a small number of coefficients and are fast to execute. The presented aspect-adaptive cylindrical projection is well suited for digital maps embedded in web pages with responsive web design, as well as GIS applications where the size of the map canvas is unknown a priori. We highlight the projection with a height-to-width ratio of 0.6:1, which we call the Compact Miller projection because it is inspired by the Miller Cylindrical projection. Unlike the Miller Cylindrical projection, the Compact Miller projection has a smaller height-to-width ratio and shows the world with less areal distortion at higher latitudes. A user study with 448 participants verified that the Compact Miller – together with the Plate Carrée projection – is the most preferred cylindrical compromise projection.     

The 3640–3510 BC rhyodacite eruption of Chachimbiro compound volcano,Ecuador: a violent directed blast produced by a satellite dome

Based on geochronological, petrological, stratigraphical, and sedimentological data, this paper describes the deposits left by the most powerful Holocene eruption of Chachimbiro compound volcano, in the northern part of Ecuador. The eruption, dated between 3640 and 3510 years BC, extruded a ～650-m-wide and ～225-m-high rhyodacite dome, located 6.3 km east of the central vent, that exploded and produced a large pyroclastic density current (PDC) directed to the southeast followed by a sub-Plinian eruptive column drifted by the wind to the west. The PDC deposit comprises two main layers. The lower layer (L1) is massive, typically coarse-grained and fines-depleted, with abundant dense juvenile fragments from the outgassed dome crust. The upper layer (L2) consists of stratified coarse ash and lapilli laminae, with juvenile clasts showing a wide density range (0.7–2.6 g cm^?3). The thickness of the whole deposit ranges from few decimeters on the hills to several meters in the valleys. Deposits extending across six valleys perpendicular to the flow direction allowed us to determine a minimum velocity of 120 m s^?1. These characteristics show striking similarities with deposits of high-energy turbulent stratified currents and in particular directed blasts. The explosion destroyed most of the dome built during the eruption. Subsequently, the sub-Plinian phase left a decimeter-thick accidental-fragment-rich pumice layer in the Chachimbiro highlands. Juvenile clasts, rhyodacitic in composition (SiO₂?=?68.3 wt%), represent the most differentiated magma of Chachimbiro volcano. Magma processes occurred at two different depths (～14.4 and 8.0 km). The hot (～936 °C) deep reservoir fed the central vent while the shallow reservoir (～858 °C) had an independent evolution, probably controlled by El Angel regional fault system. Such destructive eruptions, related to peripheral domes, are of critical importance for hazard assessment in large silicic volcanic complexes such as those forming the Frontal Volcanic Arc of Ecuador and Colombia.     

The Zambales complex: gravity anomalies and a very strange ophiolite

In common with most of the larger ophiolite bodies that were emplaced during the Cenozoic and late Mesozoic and which have experienced relatively little post-emplacement disruption or metamorphism, the Zambales Ophiolite Complex (ZOC) of western Luzon (northern Philippines) is associated with very large gravity anomalies. Worldwide and in the ZOC, peak to trough amplitudes of more than 100 mGal are common and amplitudes in excess of 200 mGal are not unknown     

Zur Geschichte des alpinen Faltungsraumes

Ohne Zusammenfassung     

Illuminated and shadowed contour lines: improving algorithms and evaluating effectiveness

Shadowed contour lines vary line width. Illuminated contour lines additionally vary color based on an angle of illumination. Illuminated and shadowed contour lines date back to the mid-nineteenth century, but their effectiveness compared to conventional contour lines has not been fully examined. Currently, illuminated and shadowed contour lines are not widely used in computer-based cartography because they are not included in most GIS apmaking software. This article introduces improvements to existing algorithms for creating illuminated and shadowed contour lines from digital elevation data. A software package is made available to allow mapmakers to more easily make customized illuminated and shadowed contour maps. A user study comparing illuminated and shadowed contour lines to conventional contour lines and shaded relief with approximately 400 participants was conducted. Results indicate that map-readers can interpret relative height differences between points better and quicker with illuminated contour lines than regular contour lines or shaded relief. Study participants were able to select absolute maxima on an unlabeled illuminated contour map and a labeled regular contour map with equal accuracy and speed. These findings suggest that illuminated contour lines could be used more frequently for improved visualization of terrain and other surface data on maps.     

Finite volume–based modeling of flow‐induced shear failure along fracture manifolds

In this paper, a numerical model to predict flow‐induced shear failure along pre‐existing fractures is presented. The framework is based on a discrete fracture representation embedded in a continuum describing the damaged matrix. A finite volume method is used to compute both flow and mechanical equilibrium, whereas specifically tailored basis functions are used to account for the physics at discontinuities. The failure criterion is based on a maximum shear strength limit, which changes with varying compressive stress on the fracture manifold. The displacements along fracture manifolds are obtained such that force balance is achieved under conditions, where shear stress of the failing fracture segment is constrained to the maximum shear strength at the segment. Simultaneously, the fluid pressure is computed independently of the shear slip. A relaxation model approach is used to obtain the maximum shear limit on the fracture manifold, which leads to grid convergence.     

Vulnerability of water resources under a changing climate and human activity in the lower Great Lakes region

Globally, the number of people experiencing water stress is expected to increase by millions by the end of the century. The Great Lakes region, representing 20% of the world's surface freshwater, is not immune to stresses on water supply due to uncertainties on the impacts of climate and land use change. It is imperative for researchers and policy makers to assess the changing state of water resources, even if the region is water rich. This research developed the integrated surface water-groundwater GSFLOW model and investigated the effects of climate change and anthropogenic activities on water resources in the lower Great Lakes region of Western New York. To capture a range of scenarios, two climate emission pathways and three land development projections were used, specifically RCP 4.5, RCP 8.5, increased urbanization by 50%, decreased urbanization by 50%, and current land cover, respectively. Model outputs of surface water and groundwater discharge into the Great Lakes and groundwater storage for mid- and late century were compared to historical to determine the direction and amplitude of changes. Both surface water and groundwater systems show no statistically significant changes under RCP 4.5 but substantial and worrisome losses with RCP 8.5 by mid-century and end of century. Under RCP 8.5, streamflow decreased by 22% for mid-century and 42% for late century. Adjusting impervious surfaces revealed complex land use effects, resulting in spatially varying groundwater head fluctuations. For instance, increasing impervious surfaces lowered groundwater levels from 0.5 to 3.8 m under Buffalo, the largest city in the model domain, due to reduced recharge in surrounding suburban areas. Ultimately, results of this study highlight the necessity of integrated modelling in assessing temporal changes to water resources. This research has implications for other water-rich areas, which may not be immune to effects of climate change and human activities.