Numbers,types, and compositions of an unbiased collection of cosmic spherules

Abstract— Micrometeorites collected from the bottom of the South Pole water well (SPWW) may represent a complete, well‐preserved sample of the cosmic dust that accreted on Earth from 1100–1500 A.D. We classified 1588 cosmic spherules in the size range 50–800 μm. The collection has 41% barred olivine spherules, 17% glass spheres, 12% cryptocrystalline spherules, 11% porphyritic olivine spherules, 12% relicgrain‐bearing spherules, 3% scoriaceous spherules, 2% I‐type spherules, 1% Ca‐AI‐Ti‐rich (CAT) spherules, and 1% G‐type spherules. We also found bubbly glass spherules, spherules with glass caps, and ones with sulfide coatings—particles that are absent from other collections. A classification sequence of the stony spherules (scoriaceous, relic‐grain‐bearing, porphyritic, barred olivine, cryptocrystalline, glass, and CAT) is consistent with progressive heating and evaporation of Fe from chondritic materials. The modern‐day accretion rate and size distribution measured at the SPWW can account for the stony spherules present in deep‐sea collection through preferential dissolution of glass and small stony spherules. However, weathering alone cannot account for the high accretion rate of I‐type spherules determined for two deep‐sea collections. The SPWW collection provides data to constrain models of atmospheric‐entry heating and to assess the effects of terrestrial weathering.     

Developing the Commons: The Contradictions of Growth in Exurban Montana

Property development in exurban areas has the capacity to undermine the amenity values that undergird that development. Predicated on that contradiction, this research seeks to explain the emergence of local, informal, planning-based regulations in the traditionally antiregulatory context of rural Montana. Adopting both the insights of institutional common property theory and those of critical materialist analysis of economic growth, the work reconciles accounts of development as inherently ecologically self-destructive with those stressing creative development and adoption of rules for collective self-governance. Using a detailed case analysis of a Montana county undergoing rapid growth, it examines what drives localized land use regulation, what controls are enacted, and whether such controls are resisted or facilitated by development capital. Findings suggest that informal regulations seek to control externalities of development on valuable amenity commons and that they are adopted with the acceptance, if not encouragement, of the development community. These fragile instruments are vulnerable to opposition, however, highlighting problems of more general relevance: Growth depends on a deregulated development regime, which produces externalities that undermine the valorization of property. Localized regulatory planning regimes are therefore both a solution to contradictions inherent in growth and a potential source of future planning problems.     

Classification and detection of dominant factors in geospatial patterns of traditional settlements in China

Journal of Geographical Sciences - The geospatial distribution pattern in traditional Chinese settlements (TCSs) reflects the traditional harmony between humans and nature, which has been learned...     

Characterisation of riparian woodlands and their potential water loss in the distal Okavango Delta, Botswana

An analysis is undertaken to develop techniques to remotely sense relative evapotranspiration outputs in the distal Okavango Delta using enhanced thematic mapper and ground based techniques to help quantify water loss. Much of this work focuses on riparian woodlands which, especially in the distal portion of the Delta, are regarded as being significant in terms of groundwater removal by transpiration. This was confirmed as vegetation cover mapping led to the identification of two riparian classes which, by association with high resistivity aeromagnetic data, were found to be rooted in near surface fresh groundwater. This paper indicates that riparian trees which remain green year long, partly sustain their growth as a result of groundwater uptake. A comparison of frequently flooded and dry floodplains with distinct riparian zones was undertaken using spectral techniques (pixel radiance values and leaf water content indices) to determine whether flooding and lateral groundwater flow stimulated growth (and therefore transpiration rate) following dormancy. Results indicate a basic similarity between the two systems with mixed evidence of assumed leaf growth. Related phenological observations in the riparian zone of the dry floodplain show that renewal of leaf growth is primarily related to rainfall, not flood events in the distal Delta. The results of this work should help effect both surface and groundwater management in the vicinity of population centres in the distal Delta.     

Interpretation of the 6818.9-Å methane feature observed on Jupiter,Saturn, and Uranus

High-resolution (0.1-Å) spectra of the 6818.9-Å methane feature obtained for Jupiter, Saturn, and Uranus by K. H. Baines, W. V. Schempp, and W. H. Smith ((1983). Icarus56, 534–542) are modeled using a doubling and adding code after J. H. Hansen ((1969). Astrophys. J.155, 565–573). The feature's rotational quantum number is estimated using the relatively homogeneous atmosphere of Saturn, with only J = 0 and J = 1 fitting the observational constraints. The aerosol content within Saturn's northern temperate region is shown to be substantially less than at the equator, indicating a haze only half as optically thick. Models of Jupiter's atmosphere are consistent with the rotational quantum-number assignment. Synthetic line profiles of the 6818.9-Å feature observed on Uranus reveal that a substantial haze exists at or above the methane condensation region with an optical depth eight times greater than previously reported. Seasonal effects are indicated. The methane column abundance is 5 ± 1 km-am. The mixing ratio of methane to hydrogen within the deep unsaturated region of the planet is 0.045 ± 0.025, based on an H₂ column abundance of 240 ± 60 km-am (W. H. Smith, W. Macy, and C. B. Pilcher (1980). Icarus43, 153–160), thus indicating that the methane comprises between one-sixth and one-half of the planet's mass. However, proper reevaluation of H₂ quadrupole features accounting for the haze reported here may significantly reduce the relative methane abundance.     

Search for and limits on plume activity on Mimas, Tethys, and Dione with the Cassini Visual Infrared Mapping Spectrometer (VIMS)

Cassini Visual Infrared Mapping Spectrometer (VIMS) observations of Mimas, Tethys, and Dione obtained during the nominal and extended missions at large solar phase angles were analyzed to search for plume activity. No forward scattered peaks in the solar phase curves of these satellites were detected. The upper limit on water vapor production for Mimas and Tethys is one order of magnitude less than the production for Enceladus. For Dione, the upper limit is two orders of magnitude less, suggesting this world is as inert as Rhea (Pitman, K.M., Buratti, B.J., Mosher, J.A., Bauer, J.M., Momary, T., Brown, R.H., Nicholson, P.D., Hedman, M.M. [2008]. Astrophys. J. Lett. 680, L65-L68). Although the plumes are best seen at ∼2.0 μm, Imaging Science Subsystem (ISS) Narrow Angle Camera images obtained at the same time as the VIMS data were also inspected for these features. None of the Cassini ISS images shows evidence for plumes. The absence of evidence for any Enceladus-like plumes on the medium-sized saturnian satellites cannot absolutely rule out current geologic activity. The activity may below our threshold of detection, or it may be occurring but not captured on the handful of observations at large solar phase angles obtained for each moon. Many VIMS and ISS images of Enceladus at large solar phase angles, for example, do not contain plumes, as the active “tiger stripes” in the south pole region are pointed away from the spacecraft at these times. The 7-year Cassini Solstice Mission is scheduled to gather additional measurements at large solar phase angles that are capable of revealing activity on the saturnian moons.     

Early Detection of Terrorism Outbreaks Using Prospective Space–Time Scan Statistics

Terrorism is a complex phenomenon with high uncertainty involving a myriad of dynamic known and unknown factors. It is and will remain a challenge to predict or detect terrorism outbreaks at an early stage. This research presents an alternative approach for modeling terrorism activity, one that monitors and detects space–time clusters of terrorist incidents using prospective space–time scan statistics. Such clusters provide indicators of potential outbreaks of terrorist incidents. To evaluate the effectiveness of the approach, we analyze the terrorist incidents in the Consortium for the Study of Terrorism and Responses to Terrorism's (START) Global Terrorism Database (GTD) from 1998 to 2004. Clusters of terrorist events are detected at each time stamp and life trajectories of these clusters are constructed based on their space–time relationship to each other. Through the life trajectories and trends of clusters, we demonstrate how space–time scan statistics detect terrorism outbreaks at an early stage.