Identification of the Bloody Creek structure,a possible impact crater in southwestern Nova Scotia,Canada

Abstract— An approximately 0.4 km diameter elliptical structure formed in Devonian granite in southwestern Nova Scotia, herein named the Bloody Creek structure (BCS), is identified as a possible impact crater. Evidence for an impact origin is based on integrated geomorphic, geophysical, and petrographic data. A near‐continuous geomorphic rim and a 10 m deep crater that is infilled with lacustrine sediments and peat define the BCS. Ground penetrating radar shows that the crater has a depressed inner floor that is sharply ringed by a 1 m high buried scarp. Heterogeneous material under the floor, interpreted as deposits from collapse of the transient cavity walls, is overlain by stratified and faulted lacustrine and wetland sediments. Alteration features found only in rim rocks include common grain comminution, polymict lithic microbreccias, kink‐banded feldspar and biotite, single and multiple sets of closely spaced planar microstructures (PMs) in quartz and feldspar, and quartz mosaicism, rare reduced mineral birefringence, and chlorite showing plastic deformation and flow microtextures. Based on their form and crystallographic orientations, the quartz PMs consist of planar deformation features that document shock‐metamorphic pressures ≤25 GPa. The age of the BCS is not determined. The low depth to diameter ratio of the crater, coupled with anomalously high shock‐metamorphic pressures recorded at its exposed rim, may be a result of significant post‐impact erosion. Alternatively, impact onto glacier ice during the waning stages of Wisconsinian deglaciation (about 12 ka BP) may have resulted in dissipation of much impact energy into the ice, resulting in the present morphology of the BCS.     

Evidence from IRAS for a very young, partially formed dust band

The relative proportions of asteroidal and cometary materials in the zodiacal cloud is an ongoing debate. The determination of the asteroidal component is constrained through the study of the Solar System dust bands (the fine-structure component superimposed on the broad background cloud), since they have been confidently linked to specific, young, asteroid families in the main belt. The disruptions that produce these families also result in the injection of dust into the cloud and thus hold the key to determining at least a minimum value for the asteroidal contribution to the zodiacal cloud. There are currently known to be at least three dust band pairs, one at approximately 9.35° associated with the Veritas family and two central band pairs near the ecliptic, one of which is associated with the Karin subcluster of the Koronis family. Through careful co-adding of almost all the pole-to-pole intensity scans in the mid-infrared wavebands of the Infrared Astronomical Satellite (IRAS) data set, we find strong evidence for a partial Solar System dust band, that is, a very young dust band in the process of formation, at approximately 17° latitude. We think this is a confirmation of the M/N partial band pair first suggested by Sykes [1988. IRAS observations of extended zodiacal structures. Astrophys. J. 334, L55-L58]. The new dust band appears at some but not all ecliptic longitudes, as expected for a young, partially formed dust band. We present preliminary modeling of the new, partial dust band which allows us to put constraints on the age of the disruption event, the inclination and node of the parent body at the time of disruption, and the quantity of dust injected into the zodiacal cloud.     

Ultraviolet spectral reflectance properties of common planetary minerals

Ultraviolet spectral reflectance properties (200-400 nm) of a large number of minerals known or presumed to exist on the surfaces of Mars, the Moon, and asteroids, and in many meteorites, were investigated. Ultraviolet reflectance spectra (200-400 nm) of these minerals range from slightly blue-sloped (reflectance decreasing toward longer wavelengths) to strongly red-sloped (reflectance increasing toward longer wavelengths). Most exhibit one or two absorption features that are attributable to FeO charge transfers involving Fe³⁺ or Fe²⁺. The UV region is a very sensitive indicator of the presence of even trace amounts (<0.01 wt%) of Fe³⁺ and Fe²⁺. The major Fe³⁺O absorption band occurs at shorter wavelengths (∼210-230 nm), and is more intense than the major Fe²⁺O absorption band (∼250-270 nm). Ti-bearing minerals, such as ilmenite, rutile and anatase exhibit UV absorption bands attributable to Ti⁴⁺O charge transfers. While the positions of metal-O charge transfer bands sometimes differ for different minerals, the variation is often not diagnostic enough to permit unique mineral identification. However, iron oxides and oxyhydroxides can generally be distinguished from Fe-bearing silicates in the 200-400 nm region on the basis of absorption band positions. Within a given mineral group (e.g., low-calcium pyroxene, olivine, plagioclase feldspar), changes in Fe²⁺ or Fe³⁺ abundance do not appear to result in a measurable change in absorption band minima positions. Absorption band positions can vary as a function of grain size, however, and this variation is likely due to band saturation effects. The intensity of metal-O charge transfers means that some minerals will exhibit saturated UV absorption bands even for fine-grained (<45 μm) powders. In cases where absorption bands are not saturated (e.g., Fe²⁺O bands in some plagioclase feldspars and pyroxenes), changes in Fe²⁺ content do not appear to cause variations in band position. In other minerals (e.g., olivine), changes in band positions are correlated with compositional and/or grain size variations, but this is likely due to increasing band saturation rather than compositional variations. Overall, we find that the UV spectral region is sensitive to different mineral properties than longer wavelength regions, and thus offers the potential to provide complementary capabilities and unique opportunities for planetary remote sensing.     

Dynamical Effects of Mars on Asteroidal Dust Particles

Asteroidal dust particles resulting from family-forming events migrate from their source locations in the asteroid belt inwards towards the Sun under the effect of Poynting-Robertson (PR) drag. Understanding the distribution of these dust particle orbits in the inner solar system is of great importance to determining the asteroidal contribution to the zodiacal cloud, the accretion rate by the Earth, and the threat that these particles pose to spacecraft and satellites in near-Earth space. In order to correctly describe this distribution of orbits in the inner solar system, we must track the dynamical perturbations that the dust particle orbits experience as they migrate inwards. In a seminal paper Öpik (1951) determines that very few of the μm-cm sized dust particles suffer a collision with the planet face as they decay inwards past Mars. Here we re-analyze this problem, considering additionally the likelihood that the dust particle orbits pass through the Hill sphere of Mars (to various depths) and experience potentially significant perturbations to their orbits. We find that a considerable fraction of dust particle orbits will enter the Hill sphere of Mars. Furthermore, we find that there is a bias with inclination, particle size, and eccentricity of the particle orbits that enter the Martian Hill sphere. In particular the bias with inclination may create a bias towards higher-inclination sources in the proportions of asteroid family particles that reach near-Earth space.     

Variations of bromide in potable ground water in the United States

Concentrations of bromide in potable ground water that has <10 mg/L chloride range from 0.0032 to 0.058 mg/L with a median value of 0.016 mg/L. The chloride/bromide mass ratio for the same water ranges from 43 to 285 with a median value of 101. The ratios, which resulted from screening approximately 165 analyses of water from 32 locations in 24 states in the United States, show a distinct geographic variation with highest values near the coast and trending toward a value of approximately 50 in the continental interior.     

Assessing the spatial distribution of crop areas using a cross-entropy method

While crop production statistics are reported on a geopolitical – often national – basis, we often need to know, for example, the status of production or productivity within specific sub-regions, watersheds, or agro-ecological zones. Such re-aggregations are typically made using expert judgments or simple area-weighting rules. We describe a new, entropy-based approach to the plausible estimates of the spatial distribution of crop areas. Using this approach tabular crop production statistics are blended judiciously with an array of other secondary data to assess the areas of specific crops within individual ‘pixels’—typically 25–100 km² in size. The information utilized includes crop production statistics, farming system characterization, satellite-based interpretation of land cover, biophysical crop suitability assessments, and population density. An application is presented in which Brazilian state level production statistics are used to generate pixel level crop area data for eight crops. To validate the spatial allocation we aggregated the pixel estimates to obtain synthetic estimates of municipality level areas in Brazil, and compared those estimates with actual municipality statistics. The approach produced extremely promising results. We then examined the robustness of these results compared to simplified approaches to spatializing crop production statistics and showed that, while computationally intensive, the cross-entropy method does provide more reliable spatial allocations.     

New risk assessment products for dealing with financial exposure to weather hazards

A market place designed to provide a variety of weather-sensitive institutions with products for dealing with their risks from weather-climate hazards has been developing in recent years. Shifts in demographics, growing population, and greater wealth across the U.S., coupled with de-regulation of utilities and expansion of global economics, have increased corporate vulnerability to weather/climate extremes. Availability of long-term quality climate data and new technologies have allowed development of weather-risk products. One widely used by electric-gas utilities is weather derivatives. These allow a utility to select a financially critical seasonal weather threshold and for a price paid to a provider, to get financial payments if this threshold is exceeded. Another new product primarily used by the insurance industry is weather risk models. These define the potential risks of severe weather losses across a region where little historical insured loss data exists. Firms develop weather-risk models based on historical storm information combined with a target region’s societal, economic, and physical conditions. Examples of the derivatives and weather-risk models and their uses are presented. These various endeavors of the new weather market exhibit the potential for dealing with shifts in weather risks due to a change in climate.     

Correlations among the parameters of the spherical model for eclipsing binaries

Correlation coefficients have been computed to investigate the parameters used to describe the spherical model of an eclipsing binary system. Regions in parameter hyperspace have been identified where strong correlations exist and, by implication, the solution determinacy is low. The results are presented in tabular form for a large number of system configurations.Originally presented at the IAU Colloquium No. 16, held at the University of Pennsylvania, Philadeiphia, Pa, U.S.A., September 8–11, 1971.