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Sample records for impact crater namibia

  1. Centrifuge impact cratering experiment 5

    Science.gov (United States)

    1984-01-01

    Transient crates motions, cratering flow fields, crates dynamics, determining impact conditions from total crater welt, centrifuge quarter-space cratering, and impact cratering mechanics research is documented.

  2. Experimental impact crater morphology

    Science.gov (United States)

    Dufresne, A.; Poelchau, M. H.; Hoerth, T.; Schaefer, F.; Thoma, K.; Deutsch, A.; Kenkmann, T.

    2012-04-01

    The research group MEMIN (Multidisciplinary Experimental and Impact Modelling Research Network) is conducting impact experiments into porous sandstones, examining, among other parameters, the influence of target pore-space saturation with water, and projectile velocity, density and mass, on the cratering process. The high-velocity (2.5-7.8 km/s) impact experiments were carried out at the two-stage light-gas gun facilities of the Fraunhofer Institute EMI (Germany) using steel, iron meteorite (Campo del Cielo IAB), and aluminium projectiles with Seeberg Sandstone as targets. The primary objectives of this study within MEMIN are to provide detailed morphometric data of the experimental craters, and to identify trends and characteristics specific to a given impact parameter. Generally, all craters, regardless of impact conditions, have an inner depression within a highly fragile, white-coloured centre, an outer spallation (i.e. tensile failure) zone, and areas of arrested spallation (i.e. spall fragments that were not completely dislodged from the target) at the crater rim. Within this general morphological framework, distinct trends and differences in crater dimensions and morphological characteristics are identified. With increasing impact velocity, the volume of craters in dry targets increases by a factor of ~4 when doubling velocity. At identical impact conditions (steel projectiles, ~5km/s), craters in dry and wet sandstone targets differ significantly in that "wet" craters are up to 76% larger in volume, have depth-diameter ratios generally below 0.19 (whereas dry craters are almost consistently above this value) at significantly larger diameters, and their spallation zone morphologies show very different characteristics. In dry craters, the spall zone surfaces dip evenly at 10-20° towards the crater centre. In wet craters, on the other hand, they consist of slightly convex slopes of 10-35° adjacent to the inner depression, and of sub-horizontal tensile

  3. Centrifuge Impact Cratering Experiments

    Science.gov (United States)

    Schmidt, R. M.; Housen, K. R.; Bjorkman, M. D.

    1985-01-01

    The kinematics of crater growth, impact induced target flow fields and the generation of impact melt were determined. The feasibility of using scaling relationships for impact melt and crater dimensions to determine impactor size and velocity was studied. It is concluded that a coupling parameter determines both the quantity of melt and the crater dimensions for impact velocities greater than 10km/s. As a result impactor radius, a, or velocity, U cannot be determined individually, but only as a product in the form of a coupling parameter, delta U micron. The melt volume and crater volume scaling relations were applied to Brent crater. The transport of melt and the validity of the melt volume scaling relations are examined.

  4. Hypervelocity impact cratering calculations

    Science.gov (United States)

    Maxwell, D. E.; Moises, H.

    1971-01-01

    A summary is presented of prediction calculations on the mechanisms involved in hypervelocity impact cratering and response of earth media. Considered are: (1) a one-gram lithium-magnesium alloys impacting basalt normally at 6.4 km/sec, and (2) a large terrestrial impact corresponding to that of Sierra Madera.

  5. Impact craters in South America

    CERN Document Server

    Acevedo, Rogelio Daniel; Ponce, Juan Federico; Stinco, Sergio G

    2015-01-01

    A complete and updated catalogue of impact craters and structures in South America from 2014 is presented here. Approximately eighty proven, suspected and disproven structures have been identified by several sources in this continent. All the impact sites of this large continent have been exhaustively reviewed: the proved ones, the possible ones and some very doubtful. Many sites remain without a clear geological ""in situ"" confirmation and some of them could be even rejected. Argentina and Brazil are leading the list containing almost everything detected. In Bolivia, Chile, Colombia, Guyana,

  6. Meteor Crater (Barringer Meteorite Crater), Arizona: Summary of Impact Conditions

    Science.gov (United States)

    Roddy, D. J.; Shoemaker, E. M.

    1995-09-01

    Meteor Crater in northern Arizona represents the most abundant type of impact feature in our Solar System, i.e., the simple bowl-shaped crater. Excellent exposures and preservation of this large crater and its ejecta blanket have made it a critical data set in both terrestrial and planetary cratering research. Recognition of the value of the crater was initiated in the early 1900's by Daniel Moreau Barringer, whose 27 years of exploration championed its impact origin [1]. In 1960, Shoemaker presented information that conclusively demonstrated that Meteor Crater was formed by hypervelocity impact [2]. This led the U.S. Geological Survey to use the crater extensively in the 1960-70's as a prime training site for the Apollo astronauts. Today, Meteor Crater continues to serve as an important research site for the international science community, as well as an educational site for over 300,000 visitors per year. Since the late 1950's, studies of this crater have presented an increasingly clearer view of this impact and its effects and have provided an improved view of impact cratering in general. To expand on this data set, we are preparing an upgraded summary on the Meteor Crater event following the format in [3], including information and interpretations on: 1) Inferred origin and age of the impacting body, 2) Inferred ablation and deceleration history in Earth's atmosphere, 3) Estimated speed, trajectory, angle of impact, and bow shock conditions, 4) Estimated coherence, density, size, and mass of impacting body, 5) Composition of impacting body (Canyon Diablo meteorite), 6) Estimated kinetic energy coupled to target rocks and atmosphere, 7) Terrain conditions at time of impact and age of impact, 8) Estimated impact dynamics, such as pressures in air, meteorite, and rocks, 9) Inferred and estimated material partitioning into vapor, melt, and fragments, 10) Crater and near-field ejecta parameters, 11) Rock unit distributions in ejecta blanket, 12) Estimated far

  7. Aboriginal oral traditions of Australian impact craters

    Science.gov (United States)

    Hamacher, Duane W.; Goldsmith, John

    2013-11-01

    In this paper we explore Aboriginal oral traditions that relate to Australian meteorite craters. Using the literature, first-hand ethnographic records and field trip data, we identify oral traditions and artworks associated with four impact sites: Gosses Bluff, Henbury, Liverpool and Wolfe Creek. Oral traditions describe impact origins for Gosses Bluff, Henbury and Wolfe Creek Craters, and non-impact origins for Liverpool Crater, with Henbury and Wolfe Creek stories having both impact and non-impact origins. Three impact sites that are believed to have been formed during human habitation of Australia -- Dalgaranga, Veevers, and Boxhole -- do not have associated oral traditions that are reported in the literature.

  8. Machine cataloging of impact craters on Mars

    Science.gov (United States)

    Stepinski, Tomasz F.; Mendenhall, Michael P.; Bue, Brian D.

    2009-09-01

    This study presents an automated system for cataloging impact craters using the MOLA 128 pixels/degree digital elevation model of Mars. Craters are detected by a two-step algorithm that first identifies round and symmetric topographic depressions as crater candidates and then selects craters using a machine-learning technique. The system is robust with respect to surface types; craters are identified with similar accuracy from all different types of martian surfaces without adjusting input parameters. By using a large training set in its final selection step, the system produces virtually no false detections. Finally, the system provides a seamless integration of crater detection with its characterization. Of particular interest is the ability of our algorithm to calculate crater depths. The system is described and its application is demonstrated on eight large sites representing all major types of martian surfaces. An evaluation of its performance and prospects for its utilization for global surveys are given by means of detailed comparison of obtained results to the manually-derived Catalog of Large Martian Impact Craters. We use the results from the test sites to construct local depth-diameter relationships based on a large number of craters. In general, obtained relationships are in agreement with what was inferred on the basis of manual measurements. However, we have found that, in Terra Cimmeria, the depth/diameter ratio has an abrupt decrease at ˜38°S regardless of crater size. If shallowing of craters is attributed to presence of sub-surface ice, a sudden change in its spatial distribution is suggested by our findings.

  9. Physics of soft impact and cratering

    CERN Document Server

    Katsuragi, Hiroaki

    2016-01-01

    This book focuses on the impact dynamics and cratering of soft matter to describe its importance, difficulty, and wide applicability to planetary-related problems. A comprehensive introduction to the dimensional analysis and constitutive laws that are necessary to discuss impact mechanics and cratering is first provided. Then, particular coverage is given to the impact of granular matter, which is one of the most crucial constituents for geophysics. While granular matter shows both solid-like and fluid-like behaviors, neither solid nor fluid dynamics is sufficient to fully understand the physics of granular matter. In order to reveal its fundamental properties, extensive impact tests have been carried out recently. The author reveals the findings of these recent studies as well as what remains unsolved in terms of impact dynamics. Impact crater morphology with various soft matter impacts also is discussed intensively. Various experimental and observational results up to the recent Itokawa asteroid’s terrain...

  10. Fresh Impact Crater and Rays in Tharsis

    Science.gov (United States)

    2002-01-01

    The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) Extended Mission has included dozens of opportunities to point the spacecraft directly at features of interest so that pictures of things not seen during the earlier Mapping Mission can be obtained. The example shown here is a small meteorite impact crater in northern Tharsis near 17.2oN, 113.8oW. Viking Orbiter images from the late 1970's showed at this location what appeared to be a dark patch with dark rays emanating from a brighter center. The MOC team surmised that the dark rays may be indicating the location of afresh crater formed by impact sometime in the past few centuries (since dark ray are quickly covered by dust falling out of the martian atmosphere). All through MOC's Mapping Mission in 1999 and 2000, attempts were made to image the crater as predictions indicated that the spacecraft would pass over the site, but the crater was never seen. Finally, in June 2001, Extended Mission operations allowed the MOC team to point the spacecraft (and hence the camera, which is fixed to the spacecraft)directly at the center of the dark rays, where we expected to find the crater.The picture on the left (above, A) is a mosaic of three MOC high resolution images and one much lower-resolution Viking image. From left to right, the images used in the mosaic are: Viking 1 516A55, MOC E05-01904, MOCM21-00272, and MOC M08-03697. Image E05-01904 is the one taken in June 2001 by pointing the spacecraft. It captured the impact crater responsible for the rays. A close-up of the crater, which is only 130 meters (427 ft)across, is shown on the right (above, B). This crater is only one-tenth the size of the famous Meteor Crater in northern Arizona.The June 2001 MOC image reveals many surprises about this feature. For one, the crater is not located at the center of the bright area from which the dark rays radiate. The rays point to the center of this bright area, not the crater. Further, the dark material ejected from the

  11. Some Studies of Terrestrial Impact Cratering Rate

    Directory of Open Access Journals (Sweden)

    Jetsu L.

    2011-06-01

    Full Text Available In 1984, a 28.4 Myr periodicity was detected in the ages of terrestrial impact craters and a 26 Myr periodicity in the epochs of mass extinctions of species. Periodic comet showers from the Oort cloud seemed to cause catastrophic events linked to mass extinctions of species. Our first study revealed that the only significant detected periodicity is the “human signal” caused by the rounding of these data into integer numbers. The second study confirmed that the original 28.4 Myr periodicity detection was not significant. The third study revealed that the quality and the quantity of the currently available data would allow detection of real periodicity only if all impacts have been periodic, which cannot be the case. The detection of a periodic signal, if present, requires that more craters should be discovered and the accuracy of age estimates improved. If we sometimes will be able to find the difference between the craters caused by asteroid and comet impacts, the aperiodic component could be removed. The lunar impact craters may eventually provide the required supplementary data.

  12. The Microstructure of Lunar Micrometeorite Impact Craters

    Science.gov (United States)

    Noble, S. K.; Keller, L. P.; Christoffersen, R.; Rahman, Z.

    2016-01-01

    The peak of the mass flux of impactors striking the lunar surface is made up of objects approximately 200 micrometers in diameter that erode rocks, comminute regolith grains, and produce agglutinates. The effects of these micro-scale impacts are still not fully understood. Much effort has focused on evaluating the physical and optical effects of micrometeorite impacts on lunar and meteoritic material using pulsed lasers to simulate the energy deposited into a substrate in a typical hypervelocity impact. Here we characterize the physical and chemical changes that accompany natural micrometeorite impacts into lunar rocks with long surface exposure to the space environment (12075 and 76015). Transmission electron microscope (TEM) observations were obtained from cross-sections of approximately 10-20 micrometers diameter craters that revealed important micro-structural details of micrometeorite impact processes, including the creation of npFe (sup 0) in the melt, and extensive deformation around the impact site.

  13. Experimental simulation of impact cratering on icy satellites

    Science.gov (United States)

    Greeley, R.; Fink, J. H.; Gault, D. E.; Guest, J. E.

    1982-01-01

    Cratering processes on icy satellites were simulated in a series of 102 laboratory impact experiments involving a wide range of target materials. For impacts into homogeneous clay slurries with impact energies ranging from five million to ten billion ergs, target yield strengths ranged from 100 to 38 Pa, and apparent viscosities ranged from 8 to 200 Pa s. Bowl-shaped craters, flat-floored craters, central peak craters with high or little relief, and craters with no relief were observed. Crater diameters increased steadily as energies were raised. A similar sequence was seen for experiment in which impact energy was held constant but target viscosity and strength progressively decreases. The experiments suggest that the physical properties of the target media relative to the gravitationally induced stresses determined the final crater morphology. Crater palimpsests could form by prompt collapse of large central peak craters formed in low target strength materials. Ages estimated from crater size-frequency distributions that include these large craters may give values that are too high.

  14. Hailar crater - A possible impact structure in Inner Mongolia, China

    Science.gov (United States)

    Xiao, Zhiyong; Chen, Zhaoxu; Pu, Jiang; Xiao, Xiao; Wang, Yichen; Huang, Jun

    2018-04-01

    Hailar crater, a probable impact structure, is a circular depression about 300 m diameter in Inner Mongolia, northeast China. With broad elevated rims, the present rim-to-floor depth is 8-20 m. Regional geological background and geomorphological comparison suggest that this feature is likely not formed by surface processes such as salt diapir, karst, aeolian, glacial, or volcanic activity. Its unique occurrence in this region and well-preserved morphology are most consistent with it being a Cenozoic impact crater. Two field expeditions in 2016 and 2017 investigated the origin of this structure, recognizing that (1) no additional craters were identified around Hailar crater in the centimeter-scale digital topography models that were constructed using a drone imaging system and stereo photogrammetry; (2) no bedrock exposures are visible within or adjacent to the crater because of thick regolith coverage, and only small pieces of angular unconsolidated rocks are present on the crater wall and the gently-sloped crater rim, suggesting recent energetic formation of the crater; (3) most samples collected from the crater have identical lithology and petrographic characteristics with the background terrain, but some crater samples contain more abundant clasts and silicate hydrothermal veins, indicating that rocks from depths have been exposed by the crater; (4) no shock metamorphic features were found in the samples after thin section examinations; and (5) a systematic sample survey and iron detector scan within and outside of the crater found no iron-rich meteorites larger than 2 cm in size in a depth of 30 cm. Although no conclusive evidence for an impact origin is found yet, Hailar crater was most likely formed by an impact based on its unique occurrence and comparative geomorphologic study. We suggest that drilling in the crater center is required to verify the impact origin, where hypothesized melt-bearing impactites may be encountered.

  15. Shallow and deep fresh impact craters in Hesperia Planum, Mars

    Science.gov (United States)

    Mouginis-Mark, Peter J.; Hayashi, Joan N.

    1993-01-01

    The depths of 109 impact craters about 2-16 km in diameter, located on the ridged plains materials of Hesperia Planum, Mars, have been measured from their shadow lengths using digital Viking Orbiter images (orbit numbers 417S-419S) and the PICS computer software. On the basis of their pristine morphology (very fresh lobate ejecta blankets, well preserved rim crests, and lack of superposed impact craters), 57 of these craters have been selected for detailed analysis of their spatial distribution and geometry. We find that south of 30 deg S, craters less than 6.0 km in diameter are markedly shallower than similar-sized craters equatorward of this latitude. No comparable relationship is observed for morphologically fresh craters greater than 6.0 km diameter. We also find that two populations exist for older craters less than 6.0 km diameter. When craters that lack ejecta blankets are grouped on the basis of depth/diameter ratio, the deeper craters also typically lie equatorward of 30 S. We interpret the spatial variation in crater depth/diameter ratios as most likely due to a poleward increase in volatiles within the top 400 m of the surface at the times these craters were formed.

  16. Two-dimensional computer simulation of hypervelocity impact cratering: some preliminary results for Meteor Crater, Arizona

    International Nuclear Information System (INIS)

    Bryan, J.B.; Burton, D.E.; Cunningham, M.E.; Lettis, L.A. Jr.

    1978-04-01

    A computational approach used for subsurface explosion cratering has been extended to hypervelocity impact cratering. Meteor (Barringer) Crater, Arizona, was selected for our first computer simulation because it was the most thoroughly studied. It is also an excellent example of a simple, bowl-shaped crater and is one of the youngest terrestrial impact craters. Shoemaker estimates that the impact occurred about 20,000 to 30,000 years ago [Roddy (1977)]. Initial conditions for this calculation included a meteorite impact velocity of 15 km/s. meteorite mass of 1.57E + 08 kg, with a corresponding kinetic energy of 1.88E + 16 J (4.5 megatons). A two-dimensional Eulerian finite difference code called SOIL was used for this simulation of a cylindrical iron projectile impacting at normal incidence into a limestone target. For this initial calculation a Tillotson equation-of-state description for iron and limestone was used with no shear strength. A color movie based on this calculation was produced using computer-generated graphics. Results obtained for this preliminary calculation of the formation of Meteor Crater, Arizona, are in good agreement with Meteor Crater Measurements

  17. Two-dimensional computer simulation of hypervelocity impact cratering: some preliminary results for Meteor Crater, Arizona

    International Nuclear Information System (INIS)

    Bryan, J.B.; Burton, D.E.; Cunningham, M.E.; Lettis, L.A. Jr.

    1978-06-01

    A computational approach used for subsurface explosion cratering was extended to hypervelocity impact cratering. Meteor (Barringer) Crater, Arizona, was selected for the first computer simulation because it is one of the most thoroughly studied craters. It is also an excellent example of a simple, bowl-shaped crater and is one of the youngest terrestrial impact craters. Initial conditions for this calculation included a meteorite impact velocity of 15 km/s, meteorite mass of 1.67 x 10 8 kg, with a corresponding kinetic energy of 1.88 x 10 16 J (4.5 megatons). A two-dimensional Eulerian finite difference code called SOIL was used for this simulation of a cylindrical iron projectile impacting at normal incidence into a limestone target. For this initial calculation, a Tillotson equation-of-state description for iron and limestone was used with no shear strength. Results obtained for this preliminary calculation of the formation of Meteor Crater are in good agreement with field measurements. A color movie based on this calculation was produced using computer-generated graphics. 19 figures, 5 tables, 63 references

  18. Two-dimensional computer simulation of hypervelocity impact cratering: some preliminary results for Meteor Crater, Arizona

    Energy Technology Data Exchange (ETDEWEB)

    Bryan, J.B.; Burton, D.E.; Cunningham, M.E.; Lettis, L.A. Jr.

    1978-06-01

    A computational approach used for subsurface explosion cratering was extended to hypervelocity impact cratering. Meteor (Barringer) Crater, Arizona, was selected for the first computer simulation because it is one of the most thoroughly studied craters. It is also an excellent example of a simple, bowl-shaped crater and is one of the youngest terrestrial impact craters. Initial conditions for this calculation included a meteorite impact velocity of 15 km/s, meteorite mass of 1.67 x 10/sup 8/ kg, with a corresponding kinetic energy of 1.88 x 10/sup 16/ J (4.5 megatons). A two-dimensional Eulerian finite difference code called SOIL was used for this simulation of a cylindrical iron projectile impacting at normal incidence into a limestone target. For this initial calculation, a Tillotson equation-of-state description for iron and limestone was used with no shear strength. Results obtained for this preliminary calculation of the formation of Meteor Crater are in good agreement with field measurements. A color movie based on this calculation was produced using computer-generated graphics. 19 figures, 5 tables, 63 references.

  19. The Carancas meteorite impact crater, Peru: Geologic surveying and modeling of crater formation and atmospheric passage

    Science.gov (United States)

    Kenkmann, T.; Artemieva, N. A.; Wünnemann, K.; Poelchau, M. H.; Elbeshausen, D.; Núñez Del Prado, H.

    2009-08-01

    The recent Carancas meteorite impact event caused a worldwide sensation. An H4-5 chondrite struck the Earth south of Lake Titicaca in Peru on September 15, 2007, and formed a crater 14.2 m across. It is the smallest, youngest, and one of two eye-witnessed impact crater events on Earth. The impact violated the hitherto existing view that stony meteorites below a size of 100 m undergo major disruption and deceleration during their passage through the atmosphere and are not capable of producing craters. Fragmentation occurs if the strength of the meteoroid is less than the aerodynamic stresses that occur in flight. The small fragments that result from a breakup rain down at terminal velocity and are not capable of producing impact craters. The Carancas cratering event, however, demonstrates that meter-sized stony meteoroids indeed can survive the atmospheric passage under specific circumstances. We present results of a detailed geologic survey of the crater and its ejecta. To constrain the possible range of impact parameters we carried out numerical models of crater formation with the iSALE hydrocode in two and three dimensions. Depending on the strength properties of the target, the impact energies range between approximately 100-1000 MJ (0.024- 0.24 t TNT). By modeling the atmospheric traverse we demonstrate that low cosmic velocities (12- 14 kms-1) and shallow entry angles (<20°) are prerequisites to keep aerodynamic stresses low (<10 MPa) and thus to prevent fragmentation of stony meteoroids with standard strength properties. This scenario results in a strong meteoroid deceleration, a deflection of the trajectory to a steeper impact angle (40-60°), and an impact velocity of 350-600 ms-1, which is insufficient to produce a shock wave and significant shock effects in target minerals. Aerodynamic and crater modeling are consistent with field data and our microscopic inspection. However, these data are in conflict with trajectories inferred from the analysis of

  20. Low-velocity impact cratering experiments in granular slopes

    Science.gov (United States)

    Hayashi, Kosuke; Sumita, Ikuro

    2017-07-01

    Low-velocity impact cratering experiments are conducted in sloped granular targets to study the effect of the slope angle θ on the crater shape and its scales. We use two types of granular matter, sand and glass beads, former of which has a larger friction coefficient μs = tanθr , where θr is the angle of repose. Experiments show that as θ increases, the crater becomes shallower and elongated in the direction of the slope. Furthermore the crater floor steepens in the upslope side and a thick rim forms in the downslope side, thus forming an asymmetric profile. High-speed images show that these features are results of ejecta being dispersed farther towards the downslope side and the subsequent avalanche which buries much of the crater floor. Such asymmetric ejecta dispersal can be explained by combining the Z-model and a ballistic model. Using the topographic maps of the craters, we classify crater shape regimes I-III, which transition with increasing θ : a full-rim crater (I), a broken-rim crater (II), and a depression (III). The critical θ for the regime transitions are larger for sand compared to glass beads, but collapse to close values when we use a normalized slope θ^ = tanθ / tanθr . Similarly we derive θ^-dependences of the scaled crater depth, length, width and their ratios which collapse the results for different targets and impact energies. We compare the crater profiles formed in our experiments with deep craters on asteroid Vesta and find that some of the scaled profiles nearly overlap and many have similar depth / length ratios. This suggests that these Vestan craters may also have formed in the gravity regime and that the formation process can be approximated by a granular flow with a similar effective friction coefficient.

  1. Determining long-term regional erosion rates using impact craters

    Science.gov (United States)

    Hergarten, Stefan; Kenkmann, Thomas

    2015-04-01

    More than 300,000 impact craters have been found on Mars, while the surface of Moon's highlands is even saturated with craters. In contrast, only 184 impact craters have been confirmed on Earth so far with only 125 of them exposed at the surface. The spatial distribution of these impact craters is highly inhomogeneous. Beside the large variation in the age of the crust, consumption of craters by erosion and burial by sediments are the main actors being responsible for the quite small and inhomogeneous crater record. In this study we present a novel approach to infer long-term average erosion rates at regional scales from the terrestrial crater inventory. The basic idea behind this approach is a dynamic equilibrium between the production of new craters and their consumption by erosion. It is assumed that each crater remains detectable until the total erosion after the impact exceeds a characteristic depth depending on the crater's diameter. Combining this model with the terrestrial crater production rate, i.e., the number of craters per unit area and time as a function of their diameter, allows for a prediction of the expected number of craters in a given region as a function of the erosion rate. Using the real crater inventory, this relationship can be inverted to determine the regional long-term erosion rate and its statistical uncertainty. A limitation by the finite age of the crust can also be taken into account. Applying the method to the Colorado Plateau and the Deccan Traps, both being regions with a distinct geological history, yields erosion rates in excellent agreement with those obtained by other, more laborious methods. However, these rates are formally exposed to large statistical uncertainties due to the small number of impact craters. As higher crater densities are related to lower erosion rates, smaller statistical errors can be expected when large regions in old parts of the crust are considered. Very low long-term erosion rates of less than 4

  2. Noachian and more recent phyllosilicates in impact craters on Mars.

    Science.gov (United States)

    Fairén, Alberto G; Chevrier, Vincent; Abramov, Oleg; Marzo, Giuseppe A; Gavin, Patricia; Davila, Alfonso F; Tornabene, Livio L; Bishop, Janice L; Roush, Ted L; Gross, Christoph; Kneissl, Thomas; Uceda, Esther R; Dohm, James M; Schulze-Makuch, Dirk; Rodríguez, J Alexis P; Amils, Ricardo; McKay, Christopher P

    2010-07-06

    Hundreds of impact craters on Mars contain diverse phyllosilicates, interpreted as excavation products of preexisting subsurface deposits following impact and crater formation. This has been used to argue that the conditions conducive to phyllosilicate synthesis, which require the presence of abundant and long-lasting liquid water, were only met early in the history of the planet, during the Noachian period (> 3.6 Gy ago), and that aqueous environments were widespread then. Here we test this hypothesis by examining the excavation process of hydrated minerals by impact events on Mars and analyzing the stability of phyllosilicates against the impact-induced thermal shock. To do so, we first compare the infrared spectra of thermally altered phyllosilicates with those of hydrated minerals known to occur in craters on Mars and then analyze the postshock temperatures reached during impact crater excavation. Our results show that phyllosilicates can resist the postshock temperatures almost everywhere in the crater, except under particular conditions in a central area in and near the point of impact. We conclude that most phyllosilicates detected inside impact craters on Mars are consistent with excavated preexisting sediments, supporting the hypothesis of a primeval and long-lasting global aqueous environment. When our analyses are applied to specific impact craters on Mars, we are able to identify both pre- and postimpact phyllosilicates, therefore extending the time of local phyllosilicate synthesis to post-Noachian times.

  3. Impact cratering experiments in Bingham materials and the morphology of craters on Mars and Ganymede

    Science.gov (United States)

    Fink, J. H.; Greeley, R.; Gault, D. E.

    1982-01-01

    Results from a series of laboratory impacts into clay slurry targets are compared with photographs of impact craters on Mars and Ganymede. The interior and ejecta lobe morphology of rampart-type craters, as well as the progression of crater forms seen with increasing diameter on both Mars and Ganymede, are equalitatively explained by a model for impact into Bingham materials. For increasing impact energies and constant target rheology, laboratory craters exhibit a morphologic progression from bowl-shaped forms that are typical of dry planetary surfaces to craters with ejecta flow lobes and decreasing interior relief, characteristic of more volatile-rich planets. A similar sequence is seen for uniform impact energy in slurries of decreasing yield strength. The planetary progressions are explained by assuming that volatile-rich or icy planetary surfaces behave locally in the same way as Bingham materials and produce ejecta slurries with yield strenghs and viscosities comparable to terrestrial debris flows. Hypothetical impact into Mars and Ganymede are compared, and it is concluded that less ejecta would be produced on Ganymede owing to its lower gravitational acceleration, surface temperature, and density of surface materials.

  4. Impact cratering on porous targets in the strength regime

    Science.gov (United States)

    Nakamura, Akiko M.

    2017-12-01

    Cratering on small bodies is crucial for the collision cascade and also contributes to the ejection of dust particles into interplanetary space. A crater cavity forms against the mechanical strength of the surface, gravitational acceleration, or both. The formation of moderately sized craters that are sufficiently larger than the thickness of the regolith on small bodies, in which mechanical strength plays the dominant role rather than gravitational acceleration, is in the strength regime. The formation of microcraters on blocks on the surface is also within the strength regime. On the other hand, the formation of a crater of a size comparable to the thickness of the regolith is affected by both gravitational acceleration and cohesion between regolith particles. In this short review, we compile data from the literature pertaining to impact cratering experiments on porous targets, and summarize the ratio of spall diameter to pit diameter, the depth, diameter, and volume of the crater cavity, and the ratio of depth to diameter. Among targets with various porosities studied in the laboratory to date, based on conventional scaling laws (Holsapple and Schmidt, J. Geophys. Res., 87, 1849-1870, 1982) the cratering efficiency obtained for porous sedimentary rocks (Suzuki et al., J. Geophys. Res. 117, E08012, 2012) is intermediate. A comparison with microcraters formed on a glass target with impact velocities up to 14 km s-1 indicates a different dependence of cratering efficiency and depth-to-diameter ratio on impact velocity.

  5. Topography of the Martian Impact Crater Tooting

    Science.gov (United States)

    Mouginis-Mark, P. J.; Garbeil, H.; Boyce, J. M.

    2009-01-01

    Tooting crater is approx.29 km in diameter, is located at 23.4degN, 207.5degE, and is classified as a multi-layered ejecta crater [1]. Our mapping last year identified several challenges that can now be addressed with HiRISE and CTX images, but specifically the third dimension of units. To address the distribution of ponded sediments, lobate flows, and volatile-bearing units within the crater cavity, we have focused this year on creating digital elevation models (DEMs) for the crater and ejecta blanket from stereo CTX and HiRISE images. These DEMs have a spatial resolution of approx.50 m for CTX data, and 2 m for HiRISE data. Each DEM is referenced to all of the available individual MOLA data points within an image, which number approx.5,000 and 800 respectively for the two data types

  6. Acoustic fluidization and the scale dependence of impact crater morphology

    Science.gov (United States)

    Melosh, H. J.; Gaffney, E. S.

    1983-01-01

    A phenomenological Bingham plastic model has previously been shown to provide an adequate description of the collapse of impact craters. This paper demonstrates that the Bingham parameters may be derived from a model in which acoustic energy generated during excavation fluidizes the rock debris surrounding the crater. Experimental support for the theoretical flow law is presented. Although the Bingham yield stress cannot be computed without detailed knowledge of the initial acoustic field, the Bingham viscosity is derived from a simple argument which shows that it increases as the 3/2 power of crater diameter, consistent with observation. Crater collapse may occur in material with internal dissipation Q as low as 100, comparable to laboratory observations of dissipation in granular materials. Crater collapse thus does not require that the acoustic field be regenerated during flow.

  7. Simple Impact Crater Shapes From Shadows - The Sequel

    Science.gov (United States)

    Chappelow, J. E.

    2008-12-01

    At the last LPSC meeting I presented the outline of a method for determining simple impact crater shapes from shadows. In theory the shadow cast within a simple crater provides enough information to derive its cross-sectional shape from shadow measurements, at least to the maximum depth to which the shadow extends. Under certain simple assumptions, this can be done analytically. If the crater is conic-section - shaped, then it can be shown that the down-sun bound of any shadow cast within it is elliptical, with one axis along the direction of illumination and the other (perpendicular to it) of semi-length D/2 (where D is diameter). The properties of this shadow-ellipse can be related to the parameters of the crater shape conic-section, thus measurements of the shadow-ellipse yield not only crater depth and diameter but also the approximate crater shape, in terms of conic sections. The method also does not depend upon the shadow crossing near the crater center, which avoids a pitfall of older shadow measurement methods. The technique is also amenable to computer implementation, which has already been largely completed. Once computerized, crater measurements can be made rapidly and repeatably. The program reads in an image, its resolution, and the solar elevation and azimuth. The user then defines the crater rim by 'clicking' on three points, and the shadow ellipse by clicking on two more. The program calculates and outputs the diameter, the depth, and parameters describing the crater's approximating conic-section. It is highly applicable to situations where only single-image photography is available, for example MESSENGER flybys of Mercury. At the meeting I will present the finished math for this method and give some examples of its use.

  8. 100 New Impact Crater Sites Found on Mars

    Science.gov (United States)

    Kennedy, M. R.; Malin, M. C.

    2009-12-01

    Recent observations constrain the formation of 100 new impact sites on Mars over the past decade; 19 of these were found using the Mars Global Surveyor Mars Orbiter Camera (MOC), and the other 81 have been identified since 2006 using the Mars Reconnaissance Orbiter Context Camera (CTX). Every 6 meter/pixel CTX image is examined upon receipt and, where they overlap images of 0.3-240 m/pixel scale acquired by the same or other Mars-orbiting spacecraft, we look for features that may have changed. New impact sites are initially identified by the presence of a new dark spot or cluster of dark spots in a CTX image. Such spots may be new impact craters, or result from the effect of impact blasts on the dusty surface. In some (generally rare) cases, the crater is sufficiently large to be resolved in the CTX image. In most cases, however, the crater(s) cannot be seen. These are tentatively designated as “candidate” new impact sites, and the CTX team then creates an opportunity for the MRO spacecraft to point its cameras off-nadir and requests that the High Resolution Imaging Science Experiment (HiRISE) team obtain an image of ~0.3 m/pixel to confirm whether a crater or crater cluster is present. It is clear even from cursory examination that the CTX observations are areographically biased to dusty, higher albedo areas on Mars. All but 3 of the 100 new impact sites occur on surfaces with Lambert albedo values in excess of 23.5%. Our initial study of MOC images greatly benefited from the initial global observations made in one month in 1999, creating a baseline date from which we could start counting new craters. The global coverage by MRO Mars Color Imager is more than a factor of 4 poorer in resolution than the MOC Wide Angle camera and does not offer the opportunity for global analysis. Instead, we must rely on partial global coverage and global coverage that has taken years to accumulate; thus we can only treat impact rates statistically. We subdivide the total data

  9. The seismic expression and hydrocarbon potential of subsurface impact craters

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, R.; Westbroek, H.H.; Lawton, D. [Calgary Univ., AB (Canada). Dept. of Geology and Geophysics

    1995-12-31

    The seismic characteristics of meteorite impact craters and their potential as oil and gas reservoirs were discussed. Seismic data from James River, Alberta, in the Western Canada Sedimentary Basin show subsurface anomalies to be meteorite impact structures. The White Valley structure in Saskatchewan has similar features and seismic anomalies indicate that it too could be a meteorite impact structure, although other possibilities have been proposed. Other impact structures in western Canada such as the Steen River structure and the Viewfield crater have or are producing hydrocarbons. 5 refs., 2 figs.

  10. A Numerical Investigation into Low-Speed Impact Cratering Events

    Science.gov (United States)

    Schwartz, Stephen; Richardson, D. C.; Michel, P.

    2012-10-01

    Impact craters are the geological features most commonly observed on the surface of solid Solar System bodies. Crater shapes and features are crucial sources of information regarding past and present surface environments, and can provide indirect information about the internal structures of these bodies. In this study, we consider the effects of low-speed impacts into granular material. Studies of low-speed impact events are suitable for understanding the cratering process leading, for instance, to secondary craters. In addition, upcoming asteroid sample return missions will employ surface sampling strategies that use impacts into the surface by a projectile. An understanding of the process can lead to better sampling strategies. We use our implementation of the Soft-Sphere Discrete Element Method (SSDEM) (Schwartz et al. 2012, Granular Matter 14, 363-380) into the parallel N-body code PKDGRAV (cf. Richardson et al. 2011, Icarus 212, 427-437) to model the impact cratering process into granular material. We consider the effects of boundary conditions on the ejecta velocity profile and discuss how results relate to the Maxwell Z-Model during the crater growth phase. Cratering simulations are compared to those of Wada et al. 2006 (Icarus 180, 528-545) and to impact experiments performed in conjunction with Hayabusa 2. This work is supported in part by grants from the National Science Foundation under grant number AST1009579 and from the Office of Space Science of NASA under grant number NNX08AM39G. Part of this study resulted from discussions with the International Team (#202) sponsored by ISSI in Bern (Switzerland). Some simulations were performed on the YORP cluster administered by the Center for Theory and Computation of the Department of Astronomy at the University of Maryland in College Park and on the SIGGAM computer cluster hosted by the Côte d'Azur Observatory in Nice (France).

  11. The impact of fiscal policy on economic growth in Namibia

    Directory of Open Access Journals (Sweden)

    E Kaakunga

    2014-07-01

    Full Text Available The purpose of this study was to shed light on the impact of fiscal policy on growth.  Governments undertake expenditures to pursue a variety of goals, only one of which may be an increase in per capita income.  Using the framework of endogenous growth models which seeks to explain sustained long term growth, we showed how a change in the mix of public spending in favour of productive activities could lead to a steady state growth rate.  The explanatory variables, which affect growth positively, include capital expenditure, tax revenue and the terms of trade.  The share of private consumption in GDP, fiscal deficit, the share of total public debt in GDP and current expenditure relates negatively to the growth rate of output.

  12. A crater and its ejecta: An interpretation of Deep Impact

    Science.gov (United States)

    Holsapple, Keith A.; Housen, Kevin R.

    2007-03-01

    We apply recently updated scaling laws for impact cratering and ejecta to interpret observations of the Deep Impact event. An important question is whether the cratering event was gravity or strength-dominated; the answer gives important clues about the properties of the surface material of Tempel 1. Gravity scaling was assumed in pre-event calculations and has been asserted in initial studies of the mission results. Because the gravity field of Tempel 1 is extremely weak, a gravity-dominated event necessarily implies a surface with essentially zero strength. The conclusion of gravity scaling was based mainly on the interpretation that the impact ejecta plume remained attached to the comet during its evolution. We address that feature here, and conclude that even strength-dominated craters would result in a plume that appeared to remain attached to the surface. We then calculate the plume characteristics from scaling laws for a variety of material types, and for gravity and strength-dominated cases. We find that no model of cratering alone can match the reported observation of plume mass and brightness history. Instead, comet-like acceleration mechanisms such as expanding vapor clouds are required to move the ejected mass to the far field in a few-hour time frame. With such mechanisms, and to within the large uncertainties, either gravity or strength craters can provide the levels of estimated observed mass. Thus, the observations are unlikely to answer the questions about the mechanical nature of the Tempel 1 surface.

  13. Snow-avalanche impact craters in southern Norway: Their morphology and dynamics compared with small terrestrial meteorite craters

    Science.gov (United States)

    Matthews, John A.; Owen, Geraint; McEwen, Lindsey J.; Shakesby, Richard A.; Hill, Jennifer L.; Vater, Amber E.; Ratcliffe, Anna C.

    2017-11-01

    This regional inventory and study of a globally uncommon landform type reveals similarities in form and process between craters produced by snow-avalanche and meteorite impacts. Fifty-two snow-avalanche impact craters (mean diameter 85 m, range 10-185 m) were investigated through field research, aerial photographic interpretation and analysis of topographic maps. The craters are sited on valley bottoms or lake margins at the foot of steep avalanche paths (α = 28-59°), generally with an easterly aspect, where the slope of the final 200 m of the avalanche path (β) typically exceeds 15°. Crater diameter correlates with the area of the avalanche start zone, which points to snow-avalanche volume as the main control on crater size. Proximal erosional scars ('blast zones') up to 40 m high indicate up-range ejection of material from the crater, assisted by air-launch of the avalanches and impulse waves generated by their impact into water-filled craters. Formation of distal mounds up to 12 m high of variable shape is favoured by more dispersed down-range deposition of ejecta. Key to the development of snow-avalanche impact craters is the repeated occurrence of topographically-focused snow avalanches that impact with a steep angle on unconsolidated sediment. Secondary craters or pits, a few metres in diameter, are attributed to the impact of individual boulders or smaller bodies of snow ejected from the main avalanche. The process of crater formation by low-density, low-velocity, large-volume snow flows occurring as multiple events is broadly comparable with cratering by single-event, high-density, high-velocity, small-volume projectiles such as small meteorites. Simple comparative modelling of snow-avalanche events associated with a crater of average size (diameter 85 m) indicates that the kinetic energy of a single snow-avalanche impact event is two orders of magnitude less than that of a single meteorite-impact event capable of producing a crater of similar size

  14. Role of impact cratering for Mars sample return

    International Nuclear Information System (INIS)

    Schultz, P.H.

    1988-01-01

    The preserved cratering record of Mars indicates that impacts play an important role in deciphering Martian geologic history, whether as a mechanism to modify the lithosphere and atmosphere or as a tool to sample the planet. The various roles of impact cratering in adding a broader understanding of Mars through returned samples are examined. Five broad roles include impact craters as: (1) a process in response to a different planetary localizer environment; (2) a probe for excavating crustal/mantle materials; (3) a possible localizer of magmatic and hydrothermal processes; (4) a chronicle of changes in the volcanic, sedimentary, atmospheric, and cosmic flux history; and (5) a chronometer for extending the geologic time scale to unsampled regions. The evidence for Earth-like processes and very nonlunar styles of volcanism and tectonism may shift the emphasis of a sampling strategy away from equally fundamental issues including crustal composition, unit ages, and climate history. Impact cratering not only played an important active role in the early Martian geologic history, it also provides an important tool for addressing such issues

  15. Measuring impact crater depth throughout the solar system

    Science.gov (United States)

    Robbins, Stuart J.; Watters, Wesley A.; Chappelow, John E.; Bray, Veronica J.; Daubar, Ingrid J.; Craddock, Robert A.; Beyer, Ross A.; Landis, Margaret E.; Ostrach, Lillian; Tornabene, Livio L.; Riggs, Jamie D.; Weaver, Brian P.

    2018-01-01

    One important, almost ubiquitous, tool for understanding the surfaces of solid bodies throughout the solar system is the study of impact craters. While measuring a distribution of crater diameters and locations is an important tool for a wide variety of studies, so too is measuring a crater's “depth.” Depth can inform numerous studies including the strength of a surface and modification rates in the local environment. There is, however, no standard data set, definition, or technique to perform this data‐gathering task, and the abundance of different definitions of “depth” and methods for estimating that quantity can lead to misunderstandings in and of the literature. In this review, we describe a wide variety of data sets and methods to analyze those data sets that have been, are currently, or could be used to derive different types of crater depth measurements. We also recommend certain nomenclature in doing so to help standardize practice in the field. We present a review section of all crater depths that have been published on different solar system bodies which shows how the field has evolved through time and how some common assumptions might not be wholly accurate. We conclude with several recommendations for researchers which could help different data sets to be more easily understood and compared.

  16. Geological Mapping of Impact Melt Deposits at Lunar Complex Craters: New Insights into Morphological Diversity, Distribution and the Cratering Process

    Science.gov (United States)

    Dhingra, D.; Head, J. W., III; Pieters, C. M.

    2014-12-01

    We have completed high resolution geological mapping of impact melt deposits at the young lunar complex craters (wall and rim impact melt units and their relation to floor units have also been mapped. Among the distinctive features of these impact melt deposits are: 1) Impact Melt Wave Fronts: These are extensive (sometimes several kilometers in length) and we have documented their occurrence and distribution in different parts of the crater floor at Jackson and Tycho. These features emphasize melt mobility and style of emplacement during the modification stage of the craters. 2) Variations in Floor Elevations: Spatially extensive and coherent sections of crater floors have different elevations at all the three craters. The observed elevation differences could be caused by subsidence due to cooling of melt and/or structural failure, together with a contribution from regional slope. 3) Melt-Covered Megablocks: We also observe large blocks/rock-fragments (megablocks) covered in impact melt, which could be sections of collapsed wall or in some cases, subdued sections of central peaks. 4) Melt-Covered Central Peaks: Impact melt has also been mapped on the central peaks but varies in spatial extent among the craters. The presence of melt on peaks must be taken into account when interpreting peak mineralogy as exposures of deeper crust. 5) Boulder Distribution: Interesting trends are observed in the distribution of boulder units of various sizes; some impact melt units have spatially extensive boulders, while boulder distribution is very scarce in other units on the floor. We interpret these distributions to be influenced by a) the differential collapse of the crater walls during the modification stage, and b) the amount of relative melt volume retained in different parts of the crater floor. These observations provide important documentation of the morphological diversity and better understanding of the emplacement and final distribution of impact melt deposits.

  17. Fertility in Namibia. Changes in fertility levels in North-Central Namibia 1960-2001, including an assessment of the impact of HIV

    Directory of Open Access Journals (Sweden)

    Riikka Shemeikka

    2006-01-01

    Full Text Available The aim of this study was to estimate the development of fertility in North-Central Namibia, former Ovamboland, from 1960 to 2001. Special attention was given to the onset of fertility decline and to the impact of the HIV epidemic on fertility. An additional aim was to introduce parish registers as a source of data for fertility research in Africa.  Data used consisted of parish registers from Evangelical Lutheran congregations, the 1991 and 2001 Population and Housing Censuses, the 1992 and 2000 Namibia Demographic and Health Surveys, and the HIV sentinel surveillances of 1992-2004. Both period and cohort fertility were analysed. The P/F ratio method was used when analysing census data. The impact of HIV infection on fertility was estimated indirectly by comparing the fertility histories of women who died at an age of less than 50 years with the fertility of other women. The impact of the HIV epidemic on fertility was assessed both among infected women and in the general population.  Fertility in the study population began to decline in 1980. The decline was rapid during the 1980s, levelled off in the early 1990s at the end of war of independence and then continued to decline until the end of the study period. According to parish registers, total fertility was 6.4 in the 1960s and 6.5 in the 1970s, and declined to 5.1 in the 1980s and 4.2 in the 1990s. Adjustment of these total fertility rates to correspond to levels of fertility based on data from the 1991 and 2001 censuses resulted in total fertility declining from 7.6 in 1960-79 to 6.0 in 1980-89, and to 4.9 in 1990-99. The decline was associated with increased age at first marriage, declining marital fertility and increasing premarital fertility. Fertility among adolescents increased, whereas the fertility of women in all other age groups declined.  During the 1980s, the war of independence contributed to declining fertility through spousal separation and delayed marriages. Contraception

  18. A global catalogue of Ceres impact craters ≥ 1 km and preliminary analysis

    Science.gov (United States)

    Gou, Sheng; Yue, Zongyu; Di, Kaichang; Liu, Zhaoqin

    2018-03-01

    The orbital data products of Ceres, including global LAMO image mosaic and global HAMO DTM with a resolution of 35 m/pixel and 135 m/pixel respectively, are utilized in this research to create a global catalogue of impact craters with diameter ≥ 1 km, and their morphometric parameters are calculated. Statistics shows: (1) There are 29,219 craters in the catalogue, and the craters have a various morphologies, e.g., polygonal crater, floor fractured crater, complex crater with central peak, etc.; (2) The identifiable smallest crater size is extended to 1 km and the crater numbers have been updated when compared with the crater catalogue (D ≥ 20 km) released by the Dawn Science Team; (3) The d/D ratios for fresh simple craters, obviously degraded simple crater and polygonal simple crater are 0.11 ± 0.04, 0.05 ± 0.04 and 0.14 ± 0.02 respectively. (4) The d/D ratios for non-polygonal complex crater and polygonal complex crater are 0.08 ± 0.04 and 0.09 ± 0.03. The global crater catalogue created in this work can be further applied to many other scientific researches, such as comparing d/D with other bodies, inferring subsurface properties, determining surface age, and estimating average erosion rate.

  19. Martian Cratering 7: The Role of Impact Gardening

    Science.gov (United States)

    Hartmann, William K.; Anguita, Jorge; de la Casa, Miguel A.; Berman, Daniel C.; Ryan, Eileen V.

    2001-01-01

    Viking-era researchers concluded that impact craters of diameter Dduricrust at Viking and Pathfinder sites demonstrates the cementing process. These results affect lander/rover searches for intact ancient deposits. The upper tens of meters of exposed Noachian units cannot survive today in a pristine state. Intact Noachian deposits might best be found in cliffside strata, or in recently exhumed regions. The hematite-rich areas found in Terra Meridiani by the Mars Global Surveyor are probably examples of the latter.

  20. Impact-generated Hydrothermal Activity at the Chicxulub Crater

    Science.gov (United States)

    Kring, D. A.; Zurcher, L.; Abramov, O.

    2007-05-01

    Borehole samples recovered from PEMEX exploration boreholes and an ICDP scientific borehole indicate the Chicxulub impact event generated hydrothermal alteration throughout a large volume of the Maya Block beneath the crater floor and extending across the bulk of the ~180 km diameter crater. The first indications of hydrothermal alteration were observed in the crater discovery samples from the Yucatan-6 borehole and manifest itself in the form of anhydrite and quartz veins. Continuous core from the Yaxcopoil-1 borehole reveal a more complex and temporally extensive alteration sequence: following a brief period at high temperatures, impact- melt-bearing polymict breccias and a thin, underlying unit of impact melt were subjected to metasomatism, producing alkali feldspar, sphene, apatite, and magnetite. As the system continued to cool, smectite-series phyllosilicates appeared. A saline solution was involved. Stable isotopes suggest the fluid was dominated by a basinal brine created mostly from existing groundwater of the Yucatan Peninsula, although contributions from down-welling water also occurred in some parts of the system. Numerical modeling of the hydrothermal system suggests circulation occurred for 1.5 to 2.3 Myr, depending on the permeability of the system. Our understanding of the hydrothermal system, however, is still crude. Additional core recovery projects, particularly into the central melt sheet, are needed to better evaluate the extent and duration of hydrothermal alteration.

  1. Geological remote sensing signatures of terrestrial impact craters

    International Nuclear Information System (INIS)

    Garvin, J.B.; Schnetzler, C.; Grieve, R.A.F.

    1988-01-01

    Geological remote sensing techniques can be used to investigate structural, depositional, and shock metamorphic effects associated with hypervelocity impact structures, some of which may be linked to global Earth system catastrophies. Although detailed laboratory and field investigations are necessary to establish conclusive evidence of an impact origin for suspected crater landforms, the synoptic perspective provided by various remote sensing systems can often serve as a pathfinder to key deposits which can then be targetted for intensive field study. In addition, remote sensing imagery can be used as a tool in the search for impact and other catastrophic explosion landforms on the basis of localized disruption and anomaly patterns. In order to reconstruct original dimensions of large, complex impact features in isolated, inaccessible regions, remote sensing imagery can be used to make preliminary estimates in the absence of field geophysical surveys. The experienced gained from two decades of planetary remote sensing of impact craters on the terrestrial planets, as well as the techniques developed for recognizing stages of degradation and initial crater morphology, can now be applied to the problem of discovering and studying eroded impact landforms on Earth. Preliminary results of remote sensing analyses of a set of terrestrial impact features in various states of degradation, geologic settings, and for a broad range of diameters and hence energies of formation are summarized. The intention is to develop a database of remote sensing signatures for catastrophic impact landforms which can then be used in EOS-era global surveys as the basis for locating the possibly hundreds of missing impact structures

  2. Emotional and cultural impacts of ICT on learners: A case study of Opuwo, Namibia

    Science.gov (United States)

    Hambira, N.; Lim, C. K.; Tan, K. L.

    2017-10-01

    It is believed that the integration of Information and Communication Technologies (ICT) among learners and teachers can tremendously enhance the quality of teaching and learning. Besides, the advancement of the ICT technology is also used to improve the academic performance of the learners in learning and has given space to the teachers to boost their teaching in a more effective manner. However, it is also crucial to identify the impacts on the cultural and emotional among the learners. Nonetheless, it is also difficult to imagine contemporary learning environments that are not supported by ICT since the impacts of these technological developments vary among the various communities. In this paper, the contributions are three folds: (i) to investigate the impacts in the cultural and emotional aspects from the perceptions of the teachers about the learners in disadvantaged and marginalized communities, (ii) to design an assessment instrument to survey and determine the different impacts of ICT use on learners from various communities through a set of questionnaires and (iii) to validate the assessment instrument through Cronbach's Alpha reliability testing. Then, the survey is conducted on learners from disadvantaged and marginalized communities in Opuwo, Namibia that makes it an ideal case study for the context of this research. This study made use of a quantitative approach using survey research design through the application of questionnaires to collect data. The size of the population of these community is approximately 500 teachers (from 16 schools, 2 High schools and 14 Primary) and the sample size that is taken into consideration is 42 (8.4% of approximate population). The research revealed that the use of ICT has emotional benefits as well cultural impacts on learners. Careful planning of ICT curriculum was suggested as it will be beneficial to the disadvantaged and marginalized learners.

  3. Impact cratering on granular beds: From the impact of raindrops to the strike of hailstones

    Science.gov (United States)

    Gordillo, Leonardo; Wang, Junping; Japardi, Fred; Teddy, Warren; Gao, Ming; Cheng, Xiang

    Impact craters generated by the impact of a spherical object onto a granular bed strongly depend on the material properties of impactors. As an example, impact cratering by liquid drops and by solid spheres exhibits qualitatively different power-law scalings for the size of resulting impact craters. While the basic energy conservation and dimensional analysis provide simple guiding rules, the detailed dynamics governing the relation between these power-law scalings is still far from clear. To analyze the transition between liquid-drop and solid-sphere impact cratering, we investigate impact cratering by liquid drops for a wide range of viscosities over 7 decades. Using high-speed photography and laser profilometry, we delineate the liquid-to-solid transition and show the emergence of the two asymptotic behaviors and their respective power laws. We find that granular avalanches triggered by impacts are crucial in understanding the energy partition between impacted surfaces and impactors, which directly determines the observed scaling relations. A simple model is constructed for the initial stage of the impact that explains the energy partition during crater formation. We ackowledge the support of NSF CAREER DMR-1452180. LG acknowledges fundings from CONICYT/BECAS CHILE 74160007.

  4. Namibia - Vocational Training Grant Fund

    Data.gov (United States)

    Millennium Challenge Corporation — The impact evaluation of the Vocational Training Grant Fund (VTGF) subactivity in Namibia used a random assignment design to determine the effects of VTGF-funded...

  5. Large-scale impact cratering on the terrestrial planets

    International Nuclear Information System (INIS)

    Grieve, R.A.F.

    1982-01-01

    The crater densities on the earth and moon form the basis for a standard flux-time curve that can be used in dating unsampled planetary surfaces and constraining the temporal history of endogenic geologic processes. Abundant evidence is seen not only that impact cratering was an important surface process in planetary history but also that large imapact events produced effects that were crucial in scale. By way of example, it is noted that the formation of multiring basins on the early moon was as important in defining the planetary tectonic framework as plate tectonics is on the earth. Evidence from several planets suggests that the effects of very-large-scale impacts go beyond the simple formation of an impact structure and serve to localize increased endogenic activity over an extended period of geologic time. Even though no longer occurring with the frequency and magnitude of early solar system history, it is noted that large scale impact events continue to affect the local geology of the planets. 92 references

  6. Wildfires Caused by Formation of Small Impact Craters: A Kaali Crater Case

    Science.gov (United States)

    Losiak, Anna; Belcher, Claire; Hudspith, Victoria; Zhu, Menghua; Bronikowska, Malgorzata; Jõeleht, Argo; Plado, Juri

    2016-04-01

    Formation of ~200-km Chicxulub 65 Ma ago was associated with release of significant amount of thermal energy [1,2,3] which was sufficient to start wildfires that had either regional [4] or global [5] range. The evidence for wildfires caused by impacts smaller than Chicxulub is inconclusive. On one hand, no signs of fires are associated with the formation of 24-km Ries crater [6]. On the other hand, the Tunguska site was burned after the impact and the numerical models of the bolide-produced thermal radiation suggest that the Tunguska-like event would produce a thermal flux to the surface that is sufficient to ignite pine needles [7]. However, in case of Tunguska the only proof for the bolide starting the fire comes from an eyewitness description collected many years after the event. Some authors [8] suggest that this fire might have been caused "normaly" later during the same year, induced on dead trees killed by the Tunguska fall. More recently it was observed that the Chelyabinsk meteor [9] - smaller than Tunguska event - did not produced a fire. In order to explore this apparent relationship in more detail, we have studied the proximal ejecta from a 100-m in diameter, ~3500 years old [10] Kaali crater (Estonia) within which we find pieces of charred organic material. Those pieces appear to have been produced during the impact, according to their stratigraphic location and following 14C analysis [19] as opposed to pre- or post-impact forest fires. In order to determine the most probable formation mechanism of the charred organic material found within Kaali proximal ejecta blanket, we: 1) Analyzed charcoal under SEM to identify the charred plants and determine properties of the charcoal related to the temperature of its formation [11]. Detected homogenization of cell walls suggests that at least some pieces of charcoal were formed at >300 °C [11]. 2) Analyzed the reflectance properties of the charred particles in order to determine the intensity with which

  7. Scientific Drilling of Impact Craters - Well Logging and Core Analyses Using Magnetic Methods (Invited)

    Science.gov (United States)

    Fucugauchi, J. U.; Perez-Cruz, L. L.; Velasco-Villarreal, M.

    2013-12-01

    Drilling projects of impact structures provide data on the structure and stratigraphy of target, impact and post-impact lithologies, providing insight on the impact dynamics and cratering. Studies have successfully included magnetic well logging and analyses in core and cuttings, directed to characterize the subsurface stratigraphy and structure at depth. There are 170-180 impact craters documented in the terrestrial record, which is a small proportion compared to expectations derived from what is observed on the Moon, Mars and other bodies of the solar system. Knowledge of the internal 3-D deep structure of craters, critical for understanding impacts and crater formation, can best be studied by geophysics and drilling. On Earth, few craters have yet been investigated by drilling. Craters have been drilled as part of industry surveys and/or academic projects, including notably Chicxulub, Sudbury, Ries, Vredefort, Manson and many other craters. As part of the Continental ICDP program, drilling projects have been conducted on the Chicxulub, Bosumtwi, Chesapeake, Ries and El gygytgyn craters. Inclusion of continuous core recovery expanded the range of paleomagnetic and rock magnetic applications, with direct core laboratory measurements, which are part of the tools available in the ocean and continental drilling programs. Drilling studies are here briefly reviewed, with emphasis on the Chicxulub crater formed by an asteroid impact 66 Ma ago at the Cretaceous/Paleogene boundary. Chicxulub crater has no surface expression, covered by a kilometer of Cenozoic sediments, thus making drilling an essential tool. As part of our studies we have drilled eleven wells with continuous core recovery. Magnetic susceptibility logging, magnetostratigraphic, rock magnetic and fabric studies have been carried out and results used for lateral correlation, dating, formation evaluation, azimuthal core orientation and physical property contrasts. Contributions of magnetic studies on impact

  8. Potential for observing and discriminating impact craters and comparable volcanic landforms on Magellan radar images

    International Nuclear Information System (INIS)

    Ford, J.P.

    1989-01-01

    Observations of small terrestrial craters by Seasat synthetic aperture radar (SAR) at high resolution (approx. 25 m) and of comparatively large Venusian craters by Venera 15/16 images at low resolution (1000 to 2000 m) and shorter wavelength show similarities in the radar responses to crater morphology. At low incidence angles, the responses are dominated by large scale slope effects on the order of meters; consequently it is difficult to locate the precise position of crater rims on the images. Abrupt contrasts in radar response to changing slope (hence incidence angle) across a crater produce sharp tonal boundaries normal to the illumination. Crater morphology that is radially symmetrical appears on images to have bilateral symmetry parallel to the illumination vector. Craters are compressed in the distal sector and drawn out in the proximal sector. At higher incidence angles obtained with the viewing geometry of SIR-A, crater morphology appears less compressed on the images. At any radar incidence angle, the distortion of a crater outline is minimal across the medial sector, in a direction normal to the illumination. Radar bright halos surround some craters imaged by SIR-A and Venera 15 and 16. The brightness probably denotes the radar response to small scale surface roughness of the surrounding ejecta blankets. Similarities in the radar responses of small terrestrial impact craters and volcanic craters of comparable dimensions emphasize the difficulties in discriminating an impact origin from a volcanic origin in the images. Similar difficulties will probably apply in discriminating the origin of small Venusian craters, if they exist. Because of orbital considerations, the nominal incidence angel of Magellan radar at the center of the imaging swath will vary from about 45 deg at 10 deg N latitude to about 16 deg at the north pole and at 70 deg S latitude. Impact craters and comparable volcanic landforms will show bilateral symmetry

  9. Characterization of the Morphometry of Impact Craters Hosting Polar Deposits in Mercury's North Polar Region

    Science.gov (United States)

    Talpe Matthieu; Zuber, Maria T.; Yang, Di; Neumann, Gregory A.; Solomon, Sean C.; Mazarico, Erwan; Vilas, Faith

    2012-01-01

    Earth-based radar images of Mercury show radar-bright material inside impact craters near the planet s poles. A previous study indicated that the polar-deposit-hosting craters (PDCs) at Mercury s north pole are shallower than craters that lack such deposits. We use data acquired by the Mercury Laser Altimeter on the MESSENGER spacecraft during 11 months of orbital observations to revisit the depths of craters at high northern latitudes on Mercury. We measured the depth and diameter of 537 craters located poleward of 45 N, evaluated the slopes of the northern and southern walls of 30 PDCs, and assessed the floor roughness of 94 craters, including nine PDCs. We find that the PDCs appear to have a fresher crater morphology than the non-PDCs and that the radar-bright material has no detectable influence on crater depths, wall slopes, or floor roughness. The statistical similarity of crater depth-diameter relations for the PDC and non-PDC populations places an upper limit on the thickness of the radar-bright material (< 170 m for a crater 11 km in diameter) that can be refined by future detailed analysis. Results of the current study are consistent with the view that the radar-bright material constitutes a relatively thin layer emplaced preferentially in comparatively young craters.

  10. Seismic velocity structure of the crust in NW Namibia: Impact of rifting and mantle plume activity

    Science.gov (United States)

    Bauer, K.; Heit, B.; Muksin, U.; Yuan, X.

    2017-12-01

    The continental crust in northwestern Namibiamainly was formed during to the Neoproterozoic assembly of Gondwana. The collision of old African and South American cratonic coressuch as the Congo, Kalahari and Rio de la Plata cratons led tothe development of the Pan-African Damara orogen. The fold systemconsists of an intracratonic branch in northern central Namibia (named Damara Belt), and two coast-parallel branches, the Kaoko Belt in northern Namibia and the Gariep Belt in the border region between Namibia and theRepublic of South Africa. During the Early Cretaceous opening of the South Atlantic ocean, the crust in NW Namibia was prominently affected by the Tristan da Cunha mantle plume, as evidenced by the emplacement of the Etendeka continental flood basalts.A local earthquake tomography was carried out in NW Namibia to investigateif and to what degree the deeper continental crust was modified by the magmaticactivity during rifting and the impingement of the Tristan da Cunhamantle plume. We analyzed data from 28 onshore stations of the temporaryWALPASS seismic network. Stations were covering the continental marginaround the landfall of the Walvis Ridge, parts of the Kaoko Belt and Damara Belt,and marginally the southwestern edges of the Congo craton.First arrivals of P and S waves were identified and travel times werepicked manually. 1D inversion was carried out with VELEST to derivestarting models and the initial seismicity distribution, and SIMUL2000was used for the subsequent 3D tomographic inversion. The resultingseismicity distribution mainly follows the structures of the Pan-Africanorogenic belts. The majority of events was localized in the upper crust,but additional seismicity was also found in the deeper crust.An anomaly of increased P velocities is revealed in the deep crust under the Etendekaflood basalt province. Increased P velocities can be explained by mafic and ultra-maficmaterial which intruded in the lower crust. The anomaly appears to be rather

  11. Enhancing Magnetic Interpretation Towards Meteorite Impact Crater at Bukit Bunuh, Perak, Malaysia

    Science.gov (United States)

    Nur Amalina, M. K. A.; Nordiana, M. M.; Saad, Rosli; Saidin, Mokhtar

    2017-04-01

    Bukit Bunuh is the most popular area of suspected meteorite impact crater. In the history of meteorite impact hitting the earth, Bukit Bunuh has complex crater of a rebound zone of positive magnetic anomaly value. This study area was located at Lenggong, Perak of peninsular Malaysia. The crater rim extended 5 km outwards with a clear subdued zone and immediately surround by a positive magnetic residual crater rim zone. A recent study was done to enhance the magnetic interpretation towards meteorite impact crater on this study area. The result obtained is being correlated with boreholes data to determine the range of local magnetic value. For the magnetic survey, the equipment used is Geometric G-856 Proton Precision magnetometers with the aids of other tools such as compass and GPS. In advance, the using of proton precision magnetometer causes it able in measures the magnetic fields separately within interval of second. Also, 18 boreholes are accumulated at study area to enhance the interpretation. The additional boreholes data had successfully described the structure of the impact crater at Bukit Bunuh in detailed where it is an eroded impact crater. Correlations with borehole records enlighten the results acquired from magnetic methods to be more reliable. A better insight of magnetic interpretation of Bukit Bunuh impact crater was done with the aid of geotechnical methods.

  12. Impact spacecraft imagery and comparative morphology of craters

    International Nuclear Information System (INIS)

    Moutsoulas, M.; Piteri, S.

    1979-01-01

    The use of hard-landing 'simple' missions for wide-scale planetary exploration is considered. As an example of their imagery potentialities, Ranger VII data are used for the study of the morphological characteristics of 16 Mare Cognitum craters. The morphological patterns of lunar craters, expressed in terms of the Depth/Diameter ratios appear to be in most cases independent of the crater location or size. (Auth.)

  13. El'gygytgyn impact crater, Chukotka, Arctic Russia: Impact cratering aspects of the 2009 ICDP drilling project

    Science.gov (United States)

    Koeberl, Christian; Pittarello, Lidia; Reimold, Wolf Uwe; Raschke, Ulli; Brigham-Grette, Julie; Melles, Martin; Minyuk, Pavel; Spray, John

    2013-01-01

    The El'gygytgyn impact structure in Chukutka, Arctic Russia, is the only impact crater currently known on Earth that was formed in mostly acid volcanic rocks (mainly of rhyolitic, with some andesitic and dacitic, compositions). In addition, because of its depth, it has provided an excellent sediment trap that records paleoclimatic information for the 3.6 Myr since its formation. For these two main reasons, because of the importance for impact and paleoclimate research, El'gygytgyn was the subject of an International Continental Scientific Drilling Program (ICDP) drilling project in 2009. During this project, which, due to its logistical and financial challenges, took almost a decade to come to fruition, a total of 642.3 m of drill core was recovered at two sites, from four holes. The obtained material included sedimentary and impactite rocks. In terms of impactites, which were recovered from 316.08 to 517.30 m depth below lake bottom (mblb), three main parts of that core segment were identified: from 316 to 390 mblb polymict lithic impact breccia, mostly suevite, with volcanic and impact melt clasts that locally contain shocked minerals, in a fine-grained clastic matrix; from 385 to 423 mblb, a brecciated sequence of volcanic rocks including both felsic and mafic (basalt) members; and from 423 to 517 mblb, a greenish rhyodacitic ignimbrite (mostly monomict breccia). The uppermost impactite (316–328 mblb) contains lacustrine sediment mixed with impact-affected components. Over the whole length of the impactite core, the abundance of shock features decreases rapidly from the top to the bottom of the studied core section. The distinction between original volcanic melt fragments and those that formed later as the result of the impact event posed major problems in the study of these rocks. The sequence that contains fairly unambiguous evidence of impact melt (which is not very abundant anyway, usually less than a few volume%) is only about 75 m thick. The reason for

  14. The Mechanics of Peak-Ring Impact Crater Formation from the IODP-ICDP Expedition 364

    Science.gov (United States)

    Melosh, H.; Collins, G. S.; Morgan, J. V.; Gulick, S. P. S.

    2017-12-01

    The Chicxulub impact crater is one of very few peak-ring impact craters on Earth. While small (less than 3 km on Earth) impact craters are typically bowl-shaped, larger craters exhibit central peaks, which in still larger (more than about 100 km on Earth) craters expand into mountainous rings with diameters close to half that of the crater rim. The origin of these peak rings has been contentious: Such craters are far too large to create in laboratory experiments and remote sensing of extraterrestrial examples has not clarified the mechanics of their formation. Two principal models of peak ring formation are currently in vogue, the "nested crater" model, in which the peak ring originates at shallow depths in the target, and the "dynamic collapse" model in which the peak ring is uplifted at the base of a collapsing, over-steepened central peak and its rocks originate at mid-crustal depths. IODP-ICDP Expedition 364 sought to elucidate, among other important goals, the mechanics of peak ring formation in the young (66 Myr), fresh, but completely buried Chicxulub impact crater. The cores from this borehole now show unambiguously that the rocks in the Chicxulub peak ring originated at mid-crustal depths, apparently ruling out the nested crater model. These rocks were shocked to pressures on the order of 10-35 GPa and were so shattered that their densities and seismic velocities now resemble those of sedimentary rocks. The morphology of the final crater, its structure as revealed in previous seismic imaging, and the results from the cores are completely consistent with modern numerical models of impact crater excavation and collapse that incorporate a model for post-impact weakening. Subsequent to the opening of a ca. 100 km diameter and 30 km deep transient crater, this enormous hole in the crust collapsed over a period of about 10 minutes. Collapse was enabled by movement of the underlying rocks, which briefly behaved in the manner of a high-viscosity fluid, a brittle

  15. Fluid outflows from Venus impact craters - Analysis from Magellan data

    Science.gov (United States)

    Asimow, Paul D.; Wood, John A.

    1992-01-01

    Many impact craters on Venus have unusual outflow features originating in or under the continuous ejecta blankets and continuing downhill into the surrounding terrain. These features clearly resulted from flow of low-viscosity fluids, but the identity of those fluids is not clear. In particular, it should not be assumed a priori that the fluid is an impact melt. A number of candidate processes by which impact events might generate the observed features are considered, and predictions are made concerning the rheological character of flows produce by each mechanism. A sample of outflows was analyzed using Magellan images and a model of unconstrained Bingham plastic flow on inclined planes, leading to estimates of viscosity and yield strength for the flow materials. It is argued that at least two different mechanisms have produced outflows on Venus: an erosive, channel-forming process and a depositional process. The erosive fluid is probably an impact melt, but the depositional fluid may consist of fluidized solid debris, vaporized material, and/or melt.

  16. Model-based Impact Assessment of an Integrated Water Management Strategy on Ecosystem Services relevant to Food Security in Namibia

    Science.gov (United States)

    Luetkemeier, R.; Liehr, S.

    2012-04-01

    North-central Namibia is characterized by seasonal alterations of drought and heavy rainfall, mostly saline groundwater resources and a lack of perennial rivers. Water scarcity poses a great challenge for freshwater supply, harvest and food security against the background of high population growth and climate change. CuveWaters project aims at poverty reduction and livelihood improvement on a long term basis by introducing a multi-resource-mix as part of an integrated water resources management (IWRM) approach. Herein, creating water buffers by rainwater harvesting (RWH) and subsurface water storage as well as reuse of treated wastewater facilitates micro-scale gardening activities. This link constitutes a major component of a sustainable adaptation strategy by contributing to the conservation and improvement of basic food and freshwater resources in order to reduce drought vulnerability. This paper presents main findings of an impact assessment carried out on the effect of integrated water resources management on ecosystem services (ESS) relevant to food security within the framework of CuveWaters project. North-central Namibia is perceived as a social-ecological system characterized by a strong mutual dependence between natural environment and anthropogenic system. This fundamental reliance on natural resources highlights the key role of ESS in semi-arid environments to sustain human livelihoods. Among other services, food provision was chosen for quantification as one of the most fundamental ESS in north-central Namibia. Different nutritional values were utilized as indicators to adopt a demand-supply approach (Ecosystem Service Profile) to illustrate the ability of the ecosystem to meet people's nutritional requirements. Calculations have been conducted using both Bayesian networks to incorporate uncertainty introduced by the variability of monthly precipitation and the application of plant specific water production functions. Results show that improving the

  17. Depressive symptoms among older caregivers raising children impacted by HIV/AIDS in the Omusati Region of Namibia.

    Science.gov (United States)

    Kalomo, Eveline; Lee, Kyoung Hag; Besthorn, Fred

    2017-12-01

    The study of depressive symptoms among caregivers raising HIV/AIDS-orphans is emerging as an important area of research. However, it has not been explored at length in generational and cultural contexts. In this study, the authors explore the role of financial strain, raising a HIV-infected and/or impacted child, and caregiver knowledge on the depressive symptoms of 89-older caregivers raising HIV/AIDS-orphans in Namibia, Africa. In this study, we found elevated levels of depressive symptoms among this population. Using hierarchical regression, a significant positive association between financial strain and depressive symptoms was found. A significant negative association between caring for an HIV-infected orphan and depression was shown. Our work suggests the need for economic assistance programs and psychosocial interventions for older caregivers.

  18. Usability of small impact craters on small surface areas in crater count dating: Analysing examples from the Harmakhis Vallis outflow channel, Mars

    Science.gov (United States)

    Kukkonen, S.; Kostama, V.-P.

    2018-05-01

    The availability of very high-resolution images has made it possible to extend crater size-frequency distribution studies to small, deca/hectometer-scale craters. This has enabled the dating of small and young surface units, as well as recent, short-time and small-scale geologic processes that have occurred on the units. Usually, however, the higher the spatial resolution of space images is, the smaller area is covered by the images. Thus the use of single, very high-resolution images in crater count age determination may be debatable if the images do not cover the studied region entirely. Here we compare the crater count results for the floor of the Harmakhis Vallis outflow channel obtained from the images of the ConTeXt camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) aboard the Mars Reconnaissance Orbiter (MRO). The CTX images enable crater counts for entire units on the Harmakhis Vallis main valley, whereas the coverage of the higher-resolution HiRISE images is limited and thus the images can only be used to date small parts of the units. Our case study shows that the crater count data based on small impact craters and small surface areas mainly correspond with the crater count data based on larger craters and more extensive counting areas on the same unit. If differences between the results were founded, they could usually be explained by the regional geology. Usually, these differences appeared when at least one cratering model age is missing from either of the crater datasets. On the other hand, we found only a few cases in which the cratering model ages were completely different. We conclude that the crater counts using small impact craters on small counting areas provide useful information about the geological processes which have modified the surface. However, it is important to remember that all the crater counts results obtained from a specific counting area always primarily represent the results from the counting area-not the whole

  19. Periodic Impact Cratering and Extinction Events Over the Last 260 Million Years

    Science.gov (United States)

    Rampino, Michael R.; Caldeira, Ken

    2015-01-01

    The claims of periodicity in impact cratering and biological extinction events are controversial. Anewly revised record of dated impact craters has been analyzed for periodicity, and compared with the record of extinctions over the past 260 Myr. A digital circular spectral analysis of 37 crater ages (ranging in age from 15 to 254 Myr ago) yielded evidence for a significant 25.8 +/- 0.6 Myr cycle. Using the same method, we found a significant 27.0 +/- 0.7 Myr cycle in the dates of the eight recognized marine extinction events over the same period. The cycles detected in impacts and extinctions have a similar phase. The impact crater dataset shows 11 apparent peaks in the last 260 Myr, at least 5 of which correlate closely with significant extinction peaks. These results suggest that the hypothesis of periodic impacts and extinction events is still viable.

  20. Mars Climate History: Insights From Impact Crater Wall Slope Statistics

    Science.gov (United States)

    Kreslavsky, Mikhail A.; Head, James W.

    2018-02-01

    We use the global distribution of the steepest slopes on crater walls derived from Mars Orbiter Laser Altimeter profile data to assess the magnitudes of degradational processes with latitude, altitude, and time. We independently confirm that Amazonian polar/high-latitude crater slope modification is substantial, but that craters in the low latitudes have essentially escaped significant slope modification since the Early Hesperian. We find that the total amount of crater wall degradation in the Late Noachian is very small in comparison to the circumpolar regions in the Late Amazonian, an observation that we interpret to mean that the Late Noachian climate was not characterized by persistent and continuous warm and wet conditions. A confirmed elevational zonality in degradation in the Early Hesperian is interpreted to mean that the atmosphere was denser than today.

  1. Fake Statistically Valid Isotopic Ages in Impact Crater Geochronology

    Science.gov (United States)

    Jourdan, F.; Schmieder, M.; McWilliams, M. M.; Buchner, E.

    2009-05-01

    Precise dating of impact structures is crucial in several fundamental aspects, such as correlating effects on the bio- and geosphere caused by these catastrophic processes. Among the 176 listed impact structures [1], only 25 have a stated age precision better than ± 2%. Statistical investigation of these 25 ages showed that 11 ages are accurate, 12 are at best ambiguous, and 2 are not well characterized [2]. In this study, we show that even with statistically valid isotope ages, the age of an impact can be "missed" by several hundred millions of years. We present a new 40Ar/39Ar plateau age of 444 ± 4 Ma for the Acraman structure (real age ˜590 Ma [3]) and four plateau ages ranging from 81.07 ± 0.76 Ma to 74.6 ± 1.5 Ma for the Brent structure (estimated real age ˜453 Ma [4]). In addition, we discuss a 40Ar/39Ar plateau age of 994 ± 11, recently obtained by [5] on the Dhala structure (real age ˜2.0 Ga [5]). Despite careful sample preparations (single grain handpicking and HF leaching, in order to remove alteration phases), these results are much younger than the impact ages. Petrographic observations show that Acraman and Dhala grain separates all have an orange color and show evidence of alteration. This suggests that these ages are the results of hydrothermal events that triggered intensive 40Ar* loss and crystallization of secondary phases. More intriguing are the Brent samples (glassy melt rocks obtained from a drill core) that appeared very fresh under the microscope. The Brent glass might be a Cretaceous pseudotachylite generated by a late adjustment of the structure and/or by a local earthquake. Because we know the approximate age of the craters with stratigraphic evidences, these outliers are easy to identify. However, this is a red flag for any uncritical interpretation of isotopic ages (including e.g., 40Ar/39Ar, U/Pb, or U-Th/He [6]). In this paper, we encourage a multi-technique approach (i.e., isotopic, stratigraphic, paleogeographic [7,8]) and

  2. Characteristics of small young lunar impact craters focusing on current production and degradation on the Moon

    Science.gov (United States)

    Kereszturi, Akos; Steinmann, Vilmos

    2017-11-01

    Analysing the size-frequency distribution of very small lunar craters (sized below 100 m including ones below 10 m) using LROC images, spatial density and related age estimations were calculated for mare and terra terrains. Altogether 1.55 km2 area was surveyed composed of 0.1-0.2 km2 units, counting 2784 craters. The maximal areal density was present at the 4-8 m diameter range at every analysed terrain suggesting the bombardment is areally relatively homogeneous. Analysing the similarities and differences between various areas, the mare terrains look about two times older than the terra terrains using ages ranged between 13 and 20 Ma for mare, 4-6 Ma for terra terrains. Substantial fluctuation (min: 936 craters/km2, max: 2495 craters/km2) was observed without obvious source of nearby secondaries or fresh ejecta blanket produced fresh crater. Randomness analysis and visual inspection also suggested no secondary craters or ejecta blanket from fresh impact could contribute substantially in the observed heterogeneity of the areal distribution of small craters - thus distant secondaries or even other, poorly known resurfacing processes should be considered in the future. The difference between the terra/mare ages might come only partly from the easier identification of small craters on smooth mare terrains, as the differences were observed for larger (30-60 m diameter) craters too. Difference in the target hardness could more contribute in this effect. It was possible to separate two groups of small craters based on their appearance: a rimmed thus less eroded, and a rimless thus more eroded one. As the separate usage of different morphology groups of craters for age estimation at the same area is not justifiable, this was used only for comparison. The SFD curves of these two groups showed characteristic differences: the steepness of the fresh craters' SFD curves are similar to each other and were larger than the isochrones. The eroded craters' SFD curves also resemble

  3. Impact ejecta and carbonate sequence in the eastern sector of the Chicxulub crater

    Science.gov (United States)

    Urrutia-Fucugauchi, Jaime; Chavez-Aguirre, Jose Maria; Pérez-Cruz, Ligia; De la Rosa, Jose Luis

    2008-12-01

    The Chicxulub 200 km diameter crater located in the Yucatan platform of the Gulf of Mexico formed 65 Myr ago and has since been covered by Tertiary post-impact carbonates. The sediment cover and absence of significant volcanic and tectonic activity in the carbonate platform have protected the crater from erosion and deformation, making Chicxulub the only large multi-ring crater in which ejecta is well preserved. Ejecta deposits have been studied by drilling/coring in the southern crater sector and at outcrops in Belize, Quintana Roo and Campeche; little information is available from other sectors. Here, we report on the drilling/coring of a section of ˜34 m of carbonate breccias at 250 m depth in the Valladolid area (120 km away from crater center), which are interpreted as Chicxulub proximal ejecta deposits. The Valladolid breccias correlate with the carbonate breccias cored in the Peto and Tekax boreholes to the south and at similar radial distance. This constitutes the first report of breccias in the eastern sector close to the crater rim. Thickness of the Valladolid breccias is less than that at the other sites, which may indicate erosion of the ejecta deposits before reestablishment of carbonate deposition. The region east of the crater rim appears different from regions to the south and west, characterized by high density and scattered distribution of sinkholes.

  4. Seismic structure of the lithosphere beneath NW Namibia: Impact of the Tristan da Cunha mantle plume

    Science.gov (United States)

    Yuan, Xiaohui; Heit, Benjamin; Brune, Sascha; Steinberger, Bernhard; Geissler, Wolfram H.; Jokat, Wilfried; Weber, Michael

    2017-01-01

    Northwestern Namibia, at the landfall of the Walvis Ridge, was affected by the Tristan da Cunha mantle plume during continental rupture between Africa and South America, as evidenced by the presence of the Etendeka continental flood basalts. Here we use data from a passive-source seismological network to investigate the upper mantle structure and to elucidate the Cretaceous mantle plume-lithosphere interaction. Receiver functions reveal an interface associated with a negative velocity contrast within the lithosphere at an average depth of 80 km. We interpret this interface as the relic of the lithosphere-asthenosphere boundary (LAB) formed during the Mesozoic by interaction of the Tristan da Cunha plume head with the pre-existing lithosphere. The velocity contrast might be explained by stagnated and "frozen" melts beneath an intensively depleted and dehydrated peridotitic mantle. The present-day LAB is poorly visible with converted waves, indicating a gradual impedance contrast. Beneath much of the study area, converted phases of the 410 and 660 km mantle transition zone discontinuities arrive 1.5 s earlier than in the landward plume-unaffected continental interior, suggesting high velocities in the upper mantle caused by a thick lithosphere. This indicates that after lithospheric thinning during continental breakup, the lithosphere has increased in thickness during the last 132 Myr. Thermal cooling of the continental lithosphere alone cannot produce the lithospheric thickness required here. We propose that the remnant plume material, which has a higher seismic velocity than the ambient mantle due to melt depletion and dehydration, significantly contributed to the thickening of the mantle lithosphere.

  5. Calculation of craters resulting from impact rupture of rock mass using pulse hydrodynamic problem formulation

    Science.gov (United States)

    Gorodilov, LV; Rasputina, TB

    2018-03-01

    A liquid–solid hydrodynamic model is used to determine shapes and sizes of craters generated by impact rupture of rocks. Near the impact location, rock is modeled by an ideal incompressible liquid, in the distance—by an absolute solid. The calculated data are compared with the experimental results obtained under impact treatment of marble by a wedge-shaped tool.

  6. Experience of modeling relief of impact lunar crater Aitken based on high-resolution orbital images

    Science.gov (United States)

    Mukhametshin, Ch R.; Semenov, A. A.; Shpekin, M. I.

    2018-05-01

    The paper presents the author’s results of modeling the relief of lunar Aitken crater on the basis of high-resolution orbital images. The images were taken in the frame of the “Apollo” program in 1971-1972 and delivered to the Earth by crews of “Apollo-15” and “Apollo-17”. The authors used the images obtained by metric and panoramic cameras. The main result is the careful study of the unusual features of Aitken crater on models created by the authors with the computer program, developed by “Agisoft Photoscan”. The paper shows what possibilities are opened with 3D models in the study of the structure of impact craters on the Moon. In particular, for the first time, the authors managed to show the structure of the glacier-like tongue in Aitken crater, which is regarded as one of the promising areas of the Moon for the forthcoming expeditions.

  7. Effect of impact angles on ejecta and crater shape of aluminum alloy 6061-T6 targets in hypervelocity impacts

    Directory of Open Access Journals (Sweden)

    Hayashi K.

    2012-08-01

    Full Text Available The effect of the impact angle of projectiles on the crater shape and ejecta in thick aluminum alloy targets was investigated in hypervelocity impacts. When polycarbonate projectiles and aluminum alloy 6061-T6 target were used, the impact angle of the projectiles clearly affected the crater shape, as expected. The impact angle also affected the ejecta mass, ejecta size and scatter angle. However, the effect at 15∘ and 22.5∘ was not great. When the impact angles were 30∘ and 45∘, the effect was clearly confirmed. The impact angle clearly affected the axial ratio of ejecta fragments, c/a.

  8. Zhamanshin and Aouelloul - Craters produced by impact of tektite-like glasses?

    Science.gov (United States)

    O'Keefe, John A.

    1987-01-01

    It is shown that the enhanced abundance of siderophile elements and chromium in tektite-like glasses from the two impact craters of Zhamanshin and Aouelloul cannot be explained as a result of contamination of the country rock by meteorites nor, probably, comets. The pattern is, however, like that found in certain Australasian tektites, and in Ivory Coast tektites. It is concluded, in agreement with earlier suggestions by Campbell-Smith and Hey, that these craters were formed by the impact of large masses of tektite-like glass, of which the glasses which were studied are fragments. It follows that it is necessary, in considering an impact crater, to bear in mind that the projectile may have been a glass.

  9. Preliminary results of soil radon gas survey of the Lake Bosomtwi impact crater

    International Nuclear Information System (INIS)

    Preko, S.; Danuor, S.K.; Menyeh, A.

    2004-01-01

    Soil radon gas survey was carried out in the Lake Bosomtwi impact crater area on eight profiles, which ran rapidly toward the end of the crater. One thousand soil samples, each weighing about 100g were acquired at a depth of 20 cm and at regular intervals of 10 m. The radon gas decay rate of the soil samples was then determined in the laboratory using the RDA-200 Radon detector and RDU-200 Degassing unit. It was found that generally areas south and east of the crater, which are severally sheared, faulted and fractured recorded high radon gas decay rates of the order of 800 counts/min whilst relatively undisturbed zones west of the crater recorded lower rates of the order of 20 counts/min. the cause of fracturing, shearing and faulting have been attributed to the effect of the meteorite impact in the Bosomtwi area, and therefore the results indicate that the soil radon gas survey could serve as a useful tool in mapping the impact-related structural characteristics of the crater. (author)

  10. Impacts into Coarse-Grained Spheres at Moderate Impact Velocities: Implications for Cratering on Asteroids and Planets

    Science.gov (United States)

    Barnouin, Olivier S.; Daly, R. Terik; Cintala, Mark J.; Crawford, David A.

    2018-01-01

    The surfaces of many planets and asteroids contain coarsely fragmental material generated by impacts or other geologic processes. The presence of such pre-existing structures may affect subsequent impacts, particularly when the width of the shock is comparable to or smaller than the size of pre-existing structures. Reasonable theoretical predictions and low speed (<300m/s) impact experiments suggest that in such targets the cratering process should be highly dissipative, which would reduce cratering efficiencies and cause a rapid decay in ejection velocity as a function of distance from the impact point. In this study, we assess whether these results apply at higher impact speeds between 0.5 and 2.5 km s-1. This study shows little change in cratering efficiency when 3.18 mm diameter glass beads are launched into targets composed of these same beads. These impacts are very efficient, and ejection velocity decays slowly as function of distance from the impact point. This slow decay in ejection velocity probably indicates a correspondingly slow decay of the shock stresses. However, these experiments reveal that initial interactions between projectile and target strongly influence the cratering process and lead to asymmetries in crater shape and ejection angles, as well as significant variations in ejection velocity at a given launch position. Such effects of asymmetric coupling could be further enhanced by heterogeneity in the initial distribution of grains in the target and by mechanical collisions between grains. These experiments help to explain why so few craters are seen on the rubble-pile asteroid Itokawa: impacts into its coarsely fragmental surface by projectiles comparable to or smaller than the size of these fragments likely yield craters that are not easily recognizable.

  11. Eastern rim of the Chesapeake Bay impact crater: Morphology, stratigraphy, and structure

    Science.gov (United States)

    Poag, C.W.

    2005-01-01

    This study reexamines seven reprocessed (increased vertical exaggeration) seismic reflection profiles that cross the eastern rim of the Chesapeake Bay impact crater. The eastern rim is expressed as an arcuate ridge that borders the crater in a fashion typical of the "raised" rim documented in many well preserved complex impact craters. The inner boundary of the eastern rim (rim wall) is formed by a series of raterfacing, steep scarps, 15-60 m high. In combination, these rim-wall scarps represent the footwalls of a system of crater-encircling normal faults, which are downthrown toward the crater. Outboard of the rim wall are several additional normal-fault blocks, whose bounding faults trend approximately parallel to the rim wall. The tops of the outboard fault blocks form two distinct, parallel, flat or gently sloping, terraces. The innermost terrace (Terrace 1) can be identified on each profile, but Terrace 2 is only sporadically present. The terraced fault blocks are composed mainly of nonmarine, poorly to moderately consolidated, siliciclastic sediments, belonging to the Lower Cretaceous Potomac Formation. Though the ridge-forming geometry of the eastern rim gives the appearance of a raised compressional feature, no compelling evidence of compressive forces is evident in the profiles studied. The structural mode, instead, is that of extension, with the clear dominance of normal faulting as the extensional mechanism. 

  12. A meteorite crater on Earth formed on September 15, 2007: The Carancas hypervelocity impact

    Science.gov (United States)

    Tancredi, G.; Ishitsuka, J.; Schultz, P. H.; Harris, R. S.; Brown, P.; Revelle, D. O.; Antier, K.; Le Pichon, A.; Rosales, D.; Vidal, E.; Varela, M. E.; Sánchez, L.; Benavente, S.; Bojorquez, J.; Cabezas, D.; Dalmau, A.

    2009-01-01

    On September 15, 2007, a bright fireball was observed and a big explosion was heard by many inhabitants near the southern shore of Lake Titicaca. In the community of Carancas (Peru), a 13.5 m crater and several fragments of a stony meteorite were found close to the site of the impact. The Carancas event is the first impact crater whose formation was directly observed by several witnesses as well as the first unambiguous seismic recording of a crater-forming meteorite impact on Earth. We present several lines of evidence that suggest that the Carancas crater was a hypervelocity impact. An event like this should have not occurred according to the accepted picture of stony meteoroids ablating in the Earth’s atmosphere, therefore it challenges our present models of entry dynamics. We discuss alternatives to explain this particular event. This emphasizes the weakness in the pervasive use of “average” parameters (such as tensile strength, fragmentation behavior and ablation behavior) in current modeling efforts. This underscores the need to examine a full range of possible values for these parameters when drawing general conclusions from models about impact processes.

  13. Meteorite impact craters and possibly impact-related structures in Estonia

    Science.gov (United States)

    Plado, Jüri

    2012-10-01

    Three structures (Neugrund, Kärdla, and Kaali) of proven impact origin make Estonia the most cratered country in the world by area. In addition, several candidate impact structures exist, waiting for future studies to determine their origin. This article is an overview of these proven and possible impact structures, including some breccia layers. It summarizes the information and descriptions of the morphology; geological characteristics; and mineralogical, chemical, and geophysical data available in the literature. The overview was prepared to make information in many earlier publications in local journals (many of which had been published in Estonian or Russian) accessible to the international community. This review summarizes the facts and observations in a historical fashion, summarizing the current state of knowledge with some additional comments, and providing the references.

  14. What Do We Know About the "Carancas-Desaguadero" Fireball, Meteorite and Impact Crater?

    Science.gov (United States)

    Tancredi, G.; Ishitsuka, J.; Rosales, D.; Vidal, E.; Dalmau, A.; Pavel, D.; Benavente, S.; Miranda, P.; Pereira, G.; Vallejos, V.; Varela, M. E.; Brandstätter, F.; Schultz, P. H.; Harris, R. S.; Sánchez, L.

    2008-03-01

    On September 15, 2007, at noon local time, a fireball was observed and heard in the southern shore of the Lake Titicaca, close to the border between Peru and Bolivia. A crater was formed due to the impact of a chondrite meteorite weighing more than 2 tons.

  15. Lunar Impact Basins: Stratigraphy, Sequence and Ages from Superposed Impact Crater Populations Measured from Lunar Orbiter Laser Altimeter (LOLA) Data

    Science.gov (United States)

    Fassett, C. I.; Head, J. W.; Kadish, S. J.; Mazarico, E.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.

    2012-01-01

    Impact basin formation is a fundamental process in the evolution of the Moon and records the history of impactors in the early solar system. In order to assess the stratigraphy, sequence, and ages of impact basins and the impactor population as a function of time, we have used topography from the Lunar Orbiter Laser Altimeter (LOLA) on the Lunar Reconnaissance Orbiter (LRO) to measure the superposed impact crater size-frequency distributions for 30 lunar basins (D = 300 km). These data generally support the widely used Wilhelms sequence of lunar basins, although we find significantly higher densities of superposed craters on many lunar basins than derived by Wilhelms (50% higher densities). Our data also provide new insight into the timing of the transition between distinct crater populations characteristic of ancient and young lunar terrains. The transition from a lunar impact flux dominated by Population 1 to Population 2 occurred before the mid-Nectarian. This is before the end of the period of rapid cratering, and potentially before the end of the hypothesized Late Heavy Bombardment. LOLA-derived crater densities also suggest that many Pre-Nectarian basins, such as South Pole-Aitken, have been cratered to saturation equilibrium. Finally, both crater counts and stratigraphic observations based on LOLA data are applicable to specific basin stratigraphic problems of interest; for example, using these data, we suggest that Serenitatis is older than Nectaris, and Humboldtianum is younger than Crisium. Sample return missions to specific basins can anchor these measurements to a Pre-Imbrian absolute chronology.

  16. LU60645GT and MA132843GT Catalogues of Lunar and Martian Impact Craters Developed Using a Crater Shape-based Interpolation Crater Detection Algorithm for Topography Data

    Science.gov (United States)

    Salamuniccar, Goran; Loncaric, Sven; Mazarico, Erwan Matias

    2012-01-01

    For Mars, 57,633 craters from the manually assembled catalogues and 72,668 additional craters identified using several crater detection algorithms (CDAs) have been merged into the MA130301GT catalogue. By contrast, for the Moon the most complete previous catalogue contains only 14,923 craters. Two recent missions provided higher-quality digital elevation maps (DEMs): SELENE (in 1/16° resolution) and Lunar Reconnaissance Orbiter (we used up to 1/512°). This was the main motivation for work on the new Crater Shape-based interpolation module, which improves previous CDA as follows: (1) it decreases the number of false-detections for the required number of true detections; (2) it improves detection capabilities for very small craters; and (3) it provides more accurate automated measurements of craters' properties. The results are: (1) LU60645GT, which is currently the most complete (up to D>=8 km) catalogue of Lunar craters; and (2) MA132843GT catalogue of Martian craters complete up to D>=2 km, which is the extension of the previous MA130301GT catalogue. As previously achieved for Mars, LU60645GT provides all properties that were provided by the previous Lunar catalogues, plus: (1) correlation between morphological descriptors from used catalogues; (2) correlation between manually assigned attributes and automated measurements; (3) average errors and their standard deviations for manually and automatically assigned attributes such as position coordinates, diameter, depth/diameter ratio, etc; and (4) a review of positional accuracy of used datasets. Additionally, surface dating could potentially be improved with the exhaustiveness of this new catalogue. The accompanying results are: (1) the possibility of comparing a large number of Lunar and Martian craters, of e.g. depth/diameter ratio and 2D profiles; (2) utilisation of a method for re-projection of datasets and catalogues, which is very useful for craters that are very close to poles; and (3) the extension of the

  17. Hypervelocity dust impact craters on photovoltaic devices imaged by ion beam induced charge

    International Nuclear Information System (INIS)

    Yang, Changyi; Wu, Yiyong; Lv, Gang; Rubanov, Sergey; Jamieson, David N.

    2015-01-01

    Hypervelocity dust has a speed of greater than 5 km/s and is a significant problem for equipment deployed in space such as satellites because of impacts that damage vulnerable components. Photovoltaic (PV) arrays are especially vulnerable because of their large surface area and the performance can be degraded owing to the disruption of the structure of the junction in the cells making up the array. Satellite PV arrays returned to Earth after service in orbit reveal a large number of craters larger than 5 μm in diameter arising from hypervelocity dust impacts. Extensive prior work has been done on the analysis of the morphology of craters in PV cells to understand the origin of the micrometeoroid that caused the crater and to study the corresponding mechanical damage to the structure of the cell. Generally, about half the craters arise from natural micrometeoroids, about one third from artificial Al-rich debris, probably from solid rocket exhausts, and the remainder from miscellaneous sources both known and unknown. However to date there has not been a microscopic study of the degradation of the electrical characteristics of PV cells exposed to hypervelocity dust impacts. Here we present an ion beam induced charge (IBIC) pilot study by a 2 MeV He microbeam of craters induced on a Hamamatsu PIN diode exposed to artificial hypervelocity Al dust from a dust accelerator. Numerous 5–30 μm diameter craters were identified and the charge collection efficiency of the crater and surrounds mapped with IBIC with bias voltages between 0 and 20 V. At highest bias, it was found the efficiency of the crater had been degraded by about 20% compared to the surrounding material. The speed distribution achieved in the Al dust accelerator was peaked at about 4 km/s compared to 11–68 km/s for dust encountered in low Earth orbit. We are able to extrapolate the charge collection efficiency degradation rate of unbiased cells in space based on our current measurements and the

  18. Hypervelocity dust impact craters on photovoltaic devices imaged by ion beam induced charge

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Changyi [School of Physics, University of Melbourne, Parkville, VIC 3010 (Australia); Wu, Yiyong; Lv, Gang [National Key Laboratory of Materials Behavior and Evaluation Technology in Space Environments, Harbin Institute of Technology, Harbin (China); Rubanov, Sergey [Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, VIC 3010 (Australia); Jamieson, David N., E-mail: d.jamieson@unimelb.edu.au [School of Physics, University of Melbourne, Parkville, VIC 3010 (Australia)

    2015-04-01

    Hypervelocity dust has a speed of greater than 5 km/s and is a significant problem for equipment deployed in space such as satellites because of impacts that damage vulnerable components. Photovoltaic (PV) arrays are especially vulnerable because of their large surface area and the performance can be degraded owing to the disruption of the structure of the junction in the cells making up the array. Satellite PV arrays returned to Earth after service in orbit reveal a large number of craters larger than 5 μm in diameter arising from hypervelocity dust impacts. Extensive prior work has been done on the analysis of the morphology of craters in PV cells to understand the origin of the micrometeoroid that caused the crater and to study the corresponding mechanical damage to the structure of the cell. Generally, about half the craters arise from natural micrometeoroids, about one third from artificial Al-rich debris, probably from solid rocket exhausts, and the remainder from miscellaneous sources both known and unknown. However to date there has not been a microscopic study of the degradation of the electrical characteristics of PV cells exposed to hypervelocity dust impacts. Here we present an ion beam induced charge (IBIC) pilot study by a 2 MeV He microbeam of craters induced on a Hamamatsu PIN diode exposed to artificial hypervelocity Al dust from a dust accelerator. Numerous 5–30 μm diameter craters were identified and the charge collection efficiency of the crater and surrounds mapped with IBIC with bias voltages between 0 and 20 V. At highest bias, it was found the efficiency of the crater had been degraded by about 20% compared to the surrounding material. The speed distribution achieved in the Al dust accelerator was peaked at about 4 km/s compared to 11–68 km/s for dust encountered in low Earth orbit. We are able to extrapolate the charge collection efficiency degradation rate of unbiased cells in space based on our current measurements and the

  19. Women, Human-Wildlife Conflict, and CBNRM: Hidden Impacts and Vulnerabilities in Kwandu Conservancy, Namibia

    OpenAIRE

    Kathryn Elizabeth Khumalo; Laurie Ann Yung

    2015-01-01

    Community-based natural resource management (CBNRM) programmes are designed to ensure that rural residents benefit from conservation initiatives. But where human-wildlife conflict threatens life and livelihood, wildlife impacts can undermine the goals of CBNRM. Based on research on women′s experiences in Namibia′s Kwandu Conservancy, we examine both the visible and hidden impacts of human-wildlife conflict. In Kwandu Conservancy, the effects of human-wildlife conflict are ongoing, reaching be...

  20. Generating Impact Maps from Automatically Detected Bomb Craters in Aerial Wartime Images Using Marked Point Processes

    Science.gov (United States)

    Kruse, Christian; Rottensteiner, Franz; Hoberg, Thorsten; Ziems, Marcel; Rebke, Julia; Heipke, Christian

    2018-04-01

    The aftermath of wartime attacks is often felt long after the war ended, as numerous unexploded bombs may still exist in the ground. Typically, such areas are documented in so-called impact maps which are based on the detection of bomb craters. This paper proposes a method for the automatic detection of bomb craters in aerial wartime images that were taken during the Second World War. The object model for the bomb craters is represented by ellipses. A probabilistic approach based on marked point processes determines the most likely configuration of objects within the scene. Adding and removing new objects to and from the current configuration, respectively, changing their positions and modifying the ellipse parameters randomly creates new object configurations. Each configuration is evaluated using an energy function. High gradient magnitudes along the border of the ellipse are favored and overlapping ellipses are penalized. Reversible Jump Markov Chain Monte Carlo sampling in combination with simulated annealing provides the global energy optimum, which describes the conformance with a predefined model. For generating the impact map a probability map is defined which is created from the automatic detections via kernel density estimation. By setting a threshold, areas around the detections are classified as contaminated or uncontaminated sites, respectively. Our results show the general potential of the method for the automatic detection of bomb craters and its automated generation of an impact map in a heterogeneous image stock.

  1. The impact of flooding on people living with HIV: a case study from the Ohangwena Region, Namibia

    Directory of Open Access Journals (Sweden)

    Carmen Anthonj

    2015-03-01

    Full Text Available Background: Floods are a disaster situation for all affected populations and especially for vulnerable groups within communities such as children, orphans, women, and people with chronic diseases such as HIV and AIDS. They need functioning health care, sanitation and hygiene, safe water, and healthy food supply, and are critically dependent on their social care and support networks. A study carried out in the Ohangwena region, Namibia, where HIV prevalence is high and extensive flooding frequently occurs, aims to provide a deeper understanding of the impact that flooding has on people living with HIV (PLWHIV as well as on HIV service providers in the region. Design: The qualitative research applying grounded theory included semi-structured interviews with PLWHIV, focus group discussions with HIV service providers, and a national feedback meeting. The findings were interpreted using the sustainable livelihoods framework, the natural hazard research approach, and health behaviour theories. Results: The study reveals that flooding poses major problems to PLWHIV in terms of their everyday lives, affecting livelihoods, work, income, and living conditions. The factors threatening them under normal conditions – poverty, malnutrition, unsafe water, sanitation and hygiene, limited access to health facilities, a weak health status, and stigma – are intensified by flood-related breakdown of infrastructure, insecurity, malnutrition, and diseases evolving over the course of a flood. A potential dual risk exists for their health: the increased risk both of infection and disease due to the inaccessibility of health services and antiretroviral treatment. A HIV and Flooding Framework was developed to display the results. Conclusions: This study demonstrates that vulnerabilities and health risks of PLWHIV will increase in a disaster situation like flooding if access to HIV prevention, treatment, care and support are not addressed and ensured. The findings and

  2. The impact of flooding on people living with HIV: a case study from the Ohangwena Region, Namibia.

    Science.gov (United States)

    Anthonj, Carmen; Nkongolo, Odon T; Schmitz, Peter; Hango, Johannes N; Kistemann, Thomas

    2015-01-01

    Floods are a disaster situation for all affected populations and especially for vulnerable groups within communities such as children, orphans, women, and people with chronic diseases such as HIV and AIDS. They need functioning health care, sanitation and hygiene, safe water, and healthy food supply, and are critically dependent on their social care and support networks. A study carried out in the Ohangwena region, Namibia, where HIV prevalence is high and extensive flooding frequently occurs, aims to provide a deeper understanding of the impact that flooding has on people living with HIV (PLWHIV) as well as on HIV service providers in the region. The qualitative research applying grounded theory included semi-structured interviews with PLWHIV, focus group discussions with HIV service providers, and a national feedback meeting. The findings were interpreted using the sustainable livelihoods framework, the natural hazard research approach, and health behaviour theories. The study reveals that flooding poses major problems to PLWHIV in terms of their everyday lives, affecting livelihoods, work, income, and living conditions. The factors threatening them under normal conditions - poverty, malnutrition, unsafe water, sanitation and hygiene, limited access to health facilities, a weak health status, and stigma - are intensified by flood-related breakdown of infrastructure, insecurity, malnutrition, and diseases evolving over the course of a flood. A potential dual risk exists for their health: the increased risk both of infection and disease due to the inaccessibility of health services and antiretroviral treatment. A HIV and Flooding Framework was developed to display the results. This study demonstrates that vulnerabilities and health risks of PLWHIV will increase in a disaster situation like flooding if access to HIV prevention, treatment, care and support are not addressed and ensured. The findings and the HIV and Flooding Framework are not specific to Ohangwena and

  3. UNAM Scientific Drilling Program of Chicxulub Impact Structure-Evidence for a 300 kilometer crater diameter

    Science.gov (United States)

    Urrutia-Fucugauchi, J.; Marin, L.; Trejo-Garcia, A.

    As part of the UNAM drilling program at the Chicxulub structure, two 700 m deep continuously cored boreholes were completed between April and July, 1995. The Peto UNAM-6 and Tekax UNAM-7 drilling sites are ˜150 km and 125 km, respectively, SSE of Chicxulub Puerto, near the crater's center. Core samples from both sites show a sequence of post-crater carbonates on top of a thick impact breccia pile covering the disturbed Mesozoic platform rocks. At UNAM-7, two impact breccia units were encountered: (1) an upper breccia, mean magnetic susceptibility is high (˜55 × 10-6 SI units), indicating a large component of silicate basement has been incorporated into this breccia, and (2) an evaporite-rich, low susceptibility impact breccia similar in character to the evaporite-rich breccias observed at the PEMEX drill sites further out. The upper breccia was encountered at ˜226 m below the surface and is ˜125 m thick; the lower breccia is immediately subjacent and is >240 m thick. This two-breccia sequence is typical of the suevite-Bunte breccia sequence found within other well preserved impact craters. The suevitic upper unit is not present at UNAM-6. Instead, a >240 m thick evaporite-rich breccia unit, similar to the lower breccia at UNAM-7, was encountered at a depth of ˜280 m. The absence of an upper breccia equivalent at UNAM-6 suggests some portion of the breccia sequence has been removed by erosion. This is consistent with interpretations that place the high-standing crater rim at 130-150 km from the center. Consequently, the stratigraphic observations and magnetic susceptibiity records on the upper and lower breccias (depth and thickness) support a ˜300 km diameter crater model.

  4. Women, Human-Wildlife Conflict, and CBNRM: Hidden Impacts and Vulnerabilities in Kwandu Conservancy, Namibia

    Directory of Open Access Journals (Sweden)

    Kathryn Elizabeth Khumalo

    2015-01-01

    Full Text Available Community-based natural resource management (CBNRM programmes are designed to ensure that rural residents benefit from conservation initiatives. But where human-wildlife conflict threatens life and livelihood, wildlife impacts can undermine the goals of CBNRM. Based on research on women′s experiences in Namibia′s Kwandu Conservancy, we examine both the visible and hidden impacts of human-wildlife conflict. In Kwandu Conservancy, the effects of human-wildlife conflict are ongoing, reaching beyond direct material losses to include hidden impacts such as persistent worries about food insecurity, fears for physical safety, and lost investments. Existing vulnerabilities related to poverty and marital statuses make some women more susceptible to wildlife impacts, and less able to recover from losses or to access compensation. This process may actually deepen the vulnerability of women whose economic status is already marginal. Because the benefits of wildlife conservation accrue at multiple scales, we recommend that the cost of human-wildlife conflict be better distributed, with additional resources for prevention and compensation made available for conservancy residents.

  5. Detection of Earth impact craters aided by the detailed global gravitational model EGM2008

    Czech Academy of Sciences Publication Activity Database

    Klokočník, Jaroslav; Kostelecký, J.; Novák, P.; Wagner, C. A.

    2010-01-01

    Roč. 7, č. 1 (2010), s. 71-97 ISSN 1214-9705 R&D Projects: GA MŠk(CZ) LC506 Grant - others:ESA(XE) ESA- PECS project No.98056 Institutional research plan: CEZ:AV0Z10030501 Keywords : global gravitational model * gravity anomaly * impact craters on the Earth Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.452, year: 2010

  6. Evidence from Impact Crater Observations for Few Large Impacts on the Moon 0.8-1.7 Ga

    Science.gov (United States)

    Kirchoff, M. R.; Bottke, W. F.; Marchi, S.; Chapman, C. R.; Enke, B.

    2012-12-01

    Our Moon is a keystone for understanding the inner solar system impact flux through time, because it is the only body for which we have crater size-frequency distributions (SFDs) through most of bombardment history and radiometric ages of probable associated terrains. Even so, the bombardment rate over the last 3.5 Gyr is poorly understood. According to the spatial density of sub-km craters on dated lunar terrains, the lunar impact flux has been roughly constant over this interval [e.g., 1 and references therein]. If so, one may expect that craters with diameter (D) > 50 km should also be equally dispersed in time over the last 3.5 Gyr. Surprisingly, our new work indicates this may not be so. We have compiled SFDs for small, superposed craters with D~0.6-15 km on the original floors of several previously designated Copernican and Eratothenian craters (USGS Geological Atlas of the Moon and [2]) with D > 50 km using JMARS. Using these data we compute the large craters' formation model ages with the Model Production Function chronology developed by Marchi et al. [3]. Many of these craters, especially on the farside (e.g., Sharnov, Birkeland), can now be suitably examined only because of the excellent LROC imaging (we use the Wide Angle Camera mosaic). As a test of our methods, we calculated the model age of the 55 km crater Aristillus (34°N, 1°E), a relatively young crater thought to have showered the Apollo 15 landing site with ejecta. Interestingly, our model age of 2.2 ± 0.6 Ga is surprisingly consistent with a 2.1 Ga-old impact-derived clast (radiometric age) returned by the Apollo 15 astronauts [4]. We find that nearly all of our computed ages for the large craters are older than indicated by previous work, with very few having ages younger than 3 Ga. Reasons for these discrepancies include (i) use of poor resolution Lunar Orbiter images (especially away from the near side) and (ii) application of the unreliable "DL" method, which involves simplified

  7. The size distributions of fragments ejected at a given velocity from impact craters

    Science.gov (United States)

    O'Keefe, John D.; Ahrens, Thomas J.

    1987-01-01

    The mass distribution of fragments that are ejected at a given velocity for impact craters is modeled to allow extrapolation of laboratory, field, and numerical results to large scale planetary events. The model is semi-empirical in nature and is derived from: (1) numerical calculations of cratering and the resultant mass versus ejection velocity, (2) observed ejecta blanket particle size distributions, (3) an empirical relationship between maximum ejecta fragment size and crater diameter, (4) measurements and theory of maximum ejecta size versus ejecta velocity, and (5) an assumption on the functional form for the distribution of fragments ejected at a given velocity. This model implies that for planetary impacts into competent rock, the distribution of fragments ejected at a given velocity is broad, e.g., 68 percent of the mass of the ejecta at a given velocity contains fragments having a mass less than 0.1 times a mass of the largest fragment moving at that velocity. The broad distribution suggests that in impact processes, additional comminution of ejecta occurs after the upward initial shock has passed in the process of the ejecta velocity vector rotating from an initially downward orientation. This additional comminution produces the broader size distribution in impact ejecta as compared to that obtained in simple brittle failure experiments.

  8. AMS radiocarbon dating of lacustrine sediment from an impact crater in northeastern China

    Energy Technology Data Exchange (ETDEWEB)

    Liu, K.X. [State Key Laboratory of Nuclear Physics and Technology and Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing 100871 (China); Chen, M., E-mail: mchen@gig.ac.cn [Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Guangzhou (China); Ding, X.F.; Fu, D.P. [State Key Laboratory of Nuclear Physics and Technology and Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing 100871 (China); Ding, P. [State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Guangzhou (China); Shen, C.D., E-mail: cdshen@gig.ac.cn [State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Guangzhou (China); Xiao, W.S. [Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Guangzhou (China)

    2013-01-15

    In order to investigate the origin and age of a bowl-shaped crater with 1.8 km diameter in northeastern China, a core drilling about 110 m in total was carried out in 2009 at the center of the crater. A 106-m-thick unit of lacustrine sediment is revealed under a surface layer of about 1 m of yellow soil. The impact origin has been confirmed based on geological analysis. In this paper, we report the AMS {sup 14}C dating results of lacustrine sediment. The data suggest that the meteorite impact in Xiuyan happened more than 50,000 years ago and a two-section linear relationship of {sup 14}C ages with the depth shows a stable sediment environment through the two time stages.

  9. Monturaqui meteorite impact crater, Chile: A field test of the utility of satellite-based mapping of ejecta at small craters

    Science.gov (United States)

    Rathbun, K.; Ukstins, I.; Drop, S.

    2017-12-01

    Monturaqui Crater is a small ( 350 m diameter), simple meteorite impact crater located in the Atacama Desert of northern Chile that was emplaced in Ordovician granite overlain by discontinuous Pliocene ignimbrite. Ejecta deposits are granite and ignimbrite, with lesser amounts of dark impact melt and rare tektites and iron shale. The impact restructured existing drainage systems in the area that have subsequently eroded through the ejecta. Satellite-based mapping and modeling, including a synthesis of photographic satellite imagery and ASTER thermal infrared imagery in ArcGIS, were used to construct a basic geological interpretation of the site with special emphasis on understanding ejecta distribution patterns. This was combined with field-based mapping to construct a high-resolution geologic map of the crater and its ejecta blanket and field check the satellite-based geologic interpretation. The satellite- and modeling-based interpretation suggests a well-preserved crater with an intact, heterogeneous ejecta blanket that has been subjected to moderate erosion. In contrast, field mapping shows that the crater has a heavily-eroded rim and ejecta blanket, and the ejecta is more heterogeneous than previously thought. In addition, the erosion rate at Monturaqui is much higher than erosion rates reported elsewhere in the Atacama Desert. The bulk compositions of the target rocks at Monturaqui are similar and the ejecta deposits are highly heterogeneous, so distinguishing between them with remote sensing is less effective than with direct field observations. In particular, the resolution of available imagery for the site is too low to resolve critical details that are readily apparent in the field on the scale of 10s of cm, and which significantly alter the geologic interpretation. The limiting factors for effective remote interpretation at Monturaqui are its target composition and crater size relative to the resolution of the remote sensing methods employed. This

  10. Delineating Bukit Bunuh impact crater boundary by geophysical and geotechnical investigation

    Energy Technology Data Exchange (ETDEWEB)

    Azwin, I. N., E-mail: nurazwinismail@yahoo.com; Rosli, S.; Nordiana, M. M.; Ragu, R. R.; Mark, J. [Geophysics Section, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Mokhtar, S. [Centre for Global Archaeological Research Malaysia, 11800 USM, Penang (Malaysia)

    2015-03-30

    Evidences of crater morphology and shock metamorphism in Bukit Bunuh, Lenggong, Malaysia were found during the archaeological research conducted by the Centre for Global Archaeological Research Malaysia, Universiti Sains Malaysia. In order to register Bukit Bunuh as one of the world meteorite impact site, detailed studies are needed to verify the boundary of the crater accordingly. Geophysical study was conducted utilising the seismic refraction and 2-D electrical resistivity method. Seismic refraction survey was done using ABEM MK8 24 channel seismograph with 14Hz geophones and 40kg weight drop while 2-D electrical resistivity survey was performed using ABEM SAS4000 Terrameter and ES10-64C electrode selector with pole-dipole array. Bedrock depths were digitized from the sections obtained. The produced bedrock topography map shows that there is low bedrock level circulated by high elevated bedrock and interpreted as crater and rim respectively with diameter approximately 8km. There are also few spots of high elevated bedrock appear at the centre of the crater which interpreted as rebounds zone. Generally, the research area is divided into two layers where the first layer with velocity 400-1100 m/s and resistivity value of 10-800 Om predominantly consists of alluvium mix with gravel and boulders. Second layer represents granitic bedrock with depth of 5-50m having velocity >2100 m/s and resistivity value of >1500 Om. This research is strengthen by good correlation between geophysical data and geotechnical borehole records executed inside and outside of the crater, on the rim, as well as at the rebound area.

  11. Impact and cratering processes on asteroids, satellites, and planets

    International Nuclear Information System (INIS)

    Chapman, C.R.; Davis, D.R.; Weidenschilling, S.J.

    1987-01-01

    A new model for scaling the outcome of catastrophic collisions from laboratory scale experiments was developed and applied to large bodies where gravitational binding is dominant. This algorithm includes a pressure dependent impact strength which predicts that large asteroids behave as intrinsically strong objects due to compressive loading of overburden throughout their interiors. For small bodies, where the gravitational loading is negligible, this model assumes that the impact strength is independent of size. There was considerable discussion of scaling laws for disruption when these results were presented to one authors colleagues. The pressure strengthening impact strength model was viewed as physically quite plausible; however, it was argued that the impact strength should decrease with increasing size in the size range where gravitational compression is negligible

  12. Mossbauer studies on impactites from Lonar impact crater

    Digital Repository Service at National Institute of Oceanography (India)

    Verma, H.C.; Misra, S.; ShyamPrasad, M.; Bijlani, N.; Tripathi, A.; Newsom, H.

    particles on the surfaces of melt impact bombs. These contain a good amount of magnetically ordered phase, most likely nanosize hematite. Interestingly, part of it is strongly attracted by amagnet and part of it is not. But both parts show a significantly...

  13. The Chicxulub crater - impact metamorphism of sulfate and carbonate lithologies

    Science.gov (United States)

    Deutsch, A.; Langenhorst, F.; Hornemann, U.; Ivanov, B. A.

    2003-04-01

    It is discussed whether in the aftermath of the Chicxulub event, impact-released CO_2 and SO_x have changed the Earth's climate, acting also as lethal thread for life. Undoubtedly, vaporization of carbonates and sulfates, which are major target lithologies at the Chicxulub impact site, occurred in the footprint of the projectile. What happened to these lithologies outside this very restricted zone was so far unconstrained. Petrologic observations on PEMEX and UNAM as well as on the CSDP cores allow to set up a general classification for shock-related pro-grade effects on sulfate and carbonate sedimentary rocks. Shock effects in lithic breccias are restricted to brecciation and formation of twins in calcite. Suevites mostly lack melted carbonate clasts; annealing effects in anhydrite fragments are absent. The underlying melt breccias contain anhydrite fragments still displaying a sedimentary texture, and limestone clasts, whose texture reflect crystallization from melt. Impact melt breccias from deeper levels frequently contain partially resorbed anhydrite clasts and a melt matrix with the Ca-rich mineral assemblage quartz + plagioclase + clinopyroxene; this mineral assemblage provides evidence for partial dissociation of CaSO_4. Large clasts of anhydrite consist of equant crystals with 120^o triple junctions, a feature indicative for re-crystallization in the solid state. Tagamites (impact melt rocks) are virtually free of clasts from sedimentary lithologies. These rocks have an extremely high formation temperature, which caused total dissociation of CaSO_4 and CaCO_3. Finally, up to 100 μm wide veins of anhydrite + calcite + quartz cut the matrix of all lithologies except the tagamites. They probably represent "degassing vents". The given scheme is in qualitative accordance with data of shock recovery and annealing experiments as well as with modeling results. In addition, it substantiates that annealing plays a fundamental role in the impact metamorphism of

  14. IMPACT CRATERING ON MERCURY: CONSEQUENCES FOR THE SPIN EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Correia, Alexandre C. M. [Department of Physics, I3N, University of Aveiro, Campus de Santiago, 3810-193 Aveiro (Portugal); Laskar, Jacques, E-mail: correia@ua.pt [ASD, IMCCE-CNRS UMR8028, Observatoire de Paris, UPMC, 77 Av. Denfert-Rochereau, 75014 Paris (France)

    2012-06-01

    Impact basins identified by Mariner 10 and Messenger flyby images provide us with a fossilized record of the impactor flux of asteroids on Mercury during the last stages of the early solar system. The distribution of these basins is not uniform across the surface and is consistent with a primordial synchronous rotation. By analyzing the size of the impacts, we derive a simple collisional model coherent with the observations. When combining it with the secular evolution of the spin of Mercury, we are able to reproduce the present 3/2 spin-orbit resonance ({approx}50% of chances), as well as a primordial synchronous rotation. This result is robust with respect to variations in the dissipation and collisional models, or in the initial spin state of the planet.

  15. IMPACT CRATERING ON MERCURY: CONSEQUENCES FOR THE SPIN EVOLUTION

    International Nuclear Information System (INIS)

    Correia, Alexandre C. M.; Laskar, Jacques

    2012-01-01

    Impact basins identified by Mariner 10 and Messenger flyby images provide us with a fossilized record of the impactor flux of asteroids on Mercury during the last stages of the early solar system. The distribution of these basins is not uniform across the surface and is consistent with a primordial synchronous rotation. By analyzing the size of the impacts, we derive a simple collisional model coherent with the observations. When combining it with the secular evolution of the spin of Mercury, we are able to reproduce the present 3/2 spin-orbit resonance (∼50% of chances), as well as a primordial synchronous rotation. This result is robust with respect to variations in the dissipation and collisional models, or in the initial spin state of the planet.

  16. Dome craters on Ganymede

    International Nuclear Information System (INIS)

    Moore, J.M.; Malin, M.C.

    1987-01-01

    Voyager observations reveal impact craters on Ganymede that are characterized by the presence of broad, high albedo, topographic domes situated within a central pit. Fifty-seven craters with central domes were identified in images covering approx. 50% of the surface. Owing to limitations in resolution, and viewing and illumination angles, the features identified are most likely a subset of dome craters. The sample appears to be sufficiently large to infer statistically meaningful trends. Dome craters appear to fall into two distinct populations on plots of the ratio of dome diameter to crater rim diameter, large-dome craters and small-dome craters. The two classes are morphologically distinct from one another. In general, large dome craters show little relief and their constituent landforms appear subdued with respect to fresh craters. The physical attributes of small-dome craters are more sharply defined, a characteristic they share with young impact craters of comparable size observed elsewhere in the solar system. Both types of dome craters exhibit central pits in which the dome is located. As it is difficult to produce domes by impact and/or erosional processes, an endogenic origin for the domes is reasonably inferred. Several hypotheses for their origin are proposed. These hypotheses are briefly reviewed

  17. Country programming mission. Namibia

    International Nuclear Information System (INIS)

    1991-01-01

    In response to a request from the Government of Namibia conveyed in a letter dated 29 November 1990 IAEA provided a multi-disciplinary Programming Mission which visited Namibia from 15 - 19 July 1991. The terms of reference of the Mission were: 1. To assess the possibilities and benefits of nuclear energy applications in Namibia's development; 2. To advise on the infrastructure required for nuclear energy projects; 3. To assist in the formulation of project proposals which could be submitted for Agency assistance. This report is based on the findings of the Mission and falls into 3 sections with 8 appendices. The first section is a country profile providing background information, the second section deals with sectorial needs and institutional review of the sectors of agriculture including animal production, life sciences (nuclear medicine and radiotherapy) and radiation protection. The third section includes possible future technical co-operation activities

  18. The effects of vehicle congestion on the environment – an EIA in the Ngorongoro crater. The Environmental Impact Statement

    OpenAIRE

    Nyahongo, Julius; Lowassa, Asanterabi; Malugu, Lucas; Nkya, Hassan; Mwakalebe, Grayson; Thomassen, Jørn; Kaltenborn, Bjørn Petter; Lyamuya, Richard; Marealle, Wilfred; Keyyu, Julius; Stokke, Sigbjørn; Røskaft, Eivin

    2007-01-01

    Nyahongo, J., Lowassa, A., Malugu, L., Nkya, H., Mwakalebe, G., Thomassen, J., Kaltenborn, B. P., Lyamuya, R., Marealle, W., Keyyu, J., Stokke, S. & Røskaft, E. 2007. The effects of vehicle congestion on the environment – an EIA in the Ngorongoro crater. The Environmental Impact Statement – NINA Report 258. 83 pp. The Ngorongoro Conservation Area Authority (NCAA) faces a great challenge in managing the vehicle congestion in the Ngorongoro crater. They are in need for an assessment of the pres...

  19. Global and local re-impact and velocity regime of ballistic ejecta of boulder craters on Ceres

    Science.gov (United States)

    Schulzeck, F.; Schröder, S. E.; Schmedemann, N.; Stephan, K.; Jaumann, R.; Raymond, C. A.; Russell, C. T.

    2018-04-01

    Imaging by the Dawn-spacecraft reveals that fresh craters on Ceres below 40 km often exhibit numerous boulders. We investigate how the fast rotating, low-gravity regime on Ceres influences their deposition. We analyze size-frequency distributions of ejecta blocks of twelve boulder craters. Global and local landing sites of boulder crater ejecta and boulder velocities are determined by the analytical calculation of elliptic particle trajectories on a rotating body. The cumulative distributions of boulder diameters follow steep-sloped power-laws. We do not find a correlation between boulder size and the distance of a boulder to its primary crater. Due to Ceres' low gravitational acceleration and fast rotation, ejecta of analyzed boulder craters (8-31 km) can be deposited across the entire surface of the dwarf planet. The particle trajectories are strongly influenced by the Coriolis effect as well as the impact geometry. Fast ejecta of high-latitude craters accumulate close to the pole of the opposite hemisphere. Fast ejecta of low-latitude craters wraps around the equator. Rotational effects are also relevant for the low-velocity regime. Boulders are ejected at velocities up to 71 m/s.

  20. Namibia Dashboard Enhancements

    Science.gov (United States)

    Mandl, Daniel; Handy, Matthew

    2014-01-01

    The purpose of this presentation is for a Technical Interchange Meeting with the Namibia Hydrological Services (NHS) in Namibia. The meeting serves as a capacity building exercise. This presentation goes over existing software functionality developed in collaboration with NHS over the past five years called the Namibia Flood Dashboard. Furthermore, it outlines new functionality developed over the past year and future functionality that will be developed. The main purpose of the Dashboard is to assist in decision support for flood warning. The Namibia Flood Dashboard already exists online in a cloud environment and has been used in prototype mode for the past few years.Functionality in the Dashboard includes river gauge hydrographs, TRMM estimate rainfall, EO-1 flood maps, infrastructure maps and other related functions. Future functionality includes attempting to integrate interoperability standards and crowd-sourcing capability. To this end, we are adding OpenStreetMap compatibility and an Applications Program Interface (API) called a GeoSocial API to enable discovery and sharing of data products useful for decision support via social media.

  1. Indigenous Storytelling in Namibia

    DEFF Research Database (Denmark)

    Rodil, Kasper; Winschiers-Theophilus, Heike

    2016-01-01

    to understand indigenous youths’ own conception of storytelling the paper presents empirical data from a study with indigenous Khoisan children in Namibia. This is followed by a discussion of an effort of digitizing indigenous intangible cultural heritage in relation to technologies’ embodied bias...

  2. Microparticle accelerator of unique design. [for micrometeoroid impact and cratering simulation

    Science.gov (United States)

    Vedder, J. F.

    1978-01-01

    A microparticle accelerator has been devised for micrometeoroid impact and cratering simulation; the device produces high-velocity (0.5-15 km/sec), micrometer-sized projectiles of any cohesive material. In the source, an electrodynamic levitator, single particles are charged by ion bombardment in high vacuum. The vertical accelerator has four drift tubes, each initially at a high negative voltage. After injection of the projectile, each tube is grounded in turn at a time determined by the voltage and charge/mass ratio to give four acceleration stages with a total voltage equivalent to about 1.7 MV.

  3. Degraded Crater Rim

    Science.gov (United States)

    2002-01-01

    (Released 3 May 2002) The Science The eastern rim of this unnamed crater in Southern Arabia Terra is very degraded (beaten up). This indicates that this crater is very ancient and has been subjected to erosion and subsequent bombardment from other impactors such as asteroids and comets. One of these later (younger) craters is seen in the upper right of this image superimposed upon the older crater rim material. Note that this smaller younger crater rim is sharper and more intact than the older crater rim. This region is also mantled with a blanket of dust. This dust mantle causes the underlying topography to take on a more subdued appearance. The Story When you think of Arabia, you probably think of hot deserts and a lot of profitable oil reserves. On Mars, however, Southern Arabia Terra is a cold place of cratered terrain. This almost frothy-looking image is the badly battered edge of an ancient crater, which has suffered both erosion and bombardment from asteroids, comets, or other impacting bodies over the long course of its existence. A blanket of dust has also settled over the region, which gives the otherwise rugged landscape a soft and more subdued appearance. The small, round crater (upper left) seems almost gemlike in its setting against the larger crater ring. But this companionship is no easy romance. Whatever formed the small crater clearly whammed into the larger crater rim at some point, obliterating part of its edge. You can tell the small crater was formed after the first and more devastating impact, because it is laid over the other larger crater. How much younger is the small one? Well, its rim is also much sharper and more intact, which gives a sense that it is probably far more youthful than the very degraded, ancient crater.

  4. Computer simulations of large asteroid impacts into oceanic and continental sites--preliminary results on atmospheric, cratering and ejecta dynamics

    Science.gov (United States)

    Roddy, D.J.; Schuster, S.H.; Rosenblatt, M.; Grant, L.B.; Hassig, P.J.; Kreyenhagen, K.N.

    1987-01-01

    Computer simulations have been completed that describe passage of a 10-km-diameter asteroid through the Earth's atmosphere and the subsequent cratering and ejecta dynamics caused by impact of the asteroid into both oceanic and continental sites. The asteroid was modeled as a spherical body moving vertically at 20 km/s with a kinetic energy of 2.6 ?? 1030 ergs (6.2 ?? 107 Mt ). Detailed material modeling of the asteroid, ocean, crustal units, sedimentary unit, and mantle included effects of strength and fracturing, generic asteroid and rock properties, porosity, saturation, lithostatic stresses, and geothermal contributions, each selected to simulate impact and geologic conditions that were as realistic as possible. Calculation of the passage of the asteroid through a U.S. Standard Atmosphere showed development of a strong bow shock wave followed by a highly shock compressed and heated air mass. Rapid expansion of this shocked air created a large low-density region that also expanded away from the impact area. Shock temperatures in air reached ???20,000 K near the surface of the uplifting crater rim and were as high as ???2000 K at more than 30 km range and 10 km altitude. Calculations to 30 s showed that the shock fronts in the air and in most of the expanding shocked air mass preceded the formation of the crater, ejecta, and rim uplift and did not interact with them. As cratering developed, uplifted rim and target material were ejected into the very low density, shock-heated air immediately above the forming crater, and complex interactions could be expected. Calculations of the impact events showed equally dramatic effects on the oceanic and continental targets through an interval of 120 s. Despite geologic differences in the targets, both cratering events developed comparable dynamic flow fields and by ???29 s had formed similar-sized transient craters ???39 km deep and ???62 km across. Transient-rim uplift of ocean and crust reached a maximum altitude of nearly

  5. Laser Raman Spectroscopic Characterization of Shocked Plagioclase from the Lonar Impact Crater, India.

    Science.gov (United States)

    Chakrabarti, R.; Basu, A. R.; Peterson, J.; Misra, S.

    2004-12-01

    We report Raman spectra of shocked plagioclase grains from the Lonar impact Crater of India. The Lonar Crater, located in the Buldana district of Maharashtra, India (19° 58'N, 76° 31'E), is an almost circular depression in the 65Ma old basalt flows of the Deccan Traps. Age estimates of this impact crater range from 10-50ka. Tektite and basalt samples were collected for this study from the rim of the crater, which is raised about 20 meters above the surrounding plains. For comparison, a Manicouagan maskelynite and an unaltered mid-oceanic ridge basalt with plagioclase laths were also analyzed. Polished thin sections of all these samples were first petrographically studied. The MORB plagioglase as well as the plagioclase from Lonar host-basalts show first order interference colors and distinct multiple lamellar twinning. The Manicouagan maskelynite is isotropic under crossed-polars. The Lonar tektite samples characteristically demonstrate spherules which are identified by their perfectly circular cross-section and isotropic nature. The spherules also contain fragments of the host basalt with plagioclase laths showing lamellar twinning. The groundmass within the spherules shows lath shaped plagioclase grains, most of which show varying degrees of isotropism due to maskelynitization. Raman scattering measurements were performed using the 514.5 nm line of an argon ion laser at an intensity of 40 kW/cm2. An inverted microscope (Nikon TE3000) with 50x objective (NA 0.55) was used for confocal imaging. A holographic notch filter removed residual laser scatter and the Raman scattering was detected by a silicon CCD at -90° C (Princeton Instruments Spec10-400R). Raman spectra were collected from ~250 cm-1 through 2000 cm-1. Raman spectra of crystalline unshocked plagioclase feldspars from the MORB and the Lonar host basalt show strongest peaks at 265 cm-1, 410 cm-1, 510 cm-1 and 1110 cm-1. The results remain the same for different points in a single grain but vary slightly

  6. Ultra-high velocity impacts: Cratering studies of microscopic impacts from 3 km/s to 30 km/s

    International Nuclear Information System (INIS)

    Stradling, G.L.; Idzorek, G.C.; Shafer, B.P.; Curling, H.L. Jr.; Collopy, M.T.; Hopkins Blossom, A.A.; Fuerstenau, S.

    1992-01-01

    Cratering experiments performed under carefully controlled conditions at impact velocities ranging from 3 km/s to 30 km/s into a wide variety of target materials are presented. These impact experiments use the 6 MV vertical Van de Graaff accelerator of the Ion Beam Facility at the Los Alamos National Laboratory to electrostatically accelerate highly charged iron microspheres. The sub-micron spheres, from a random size distribution, are shocklessly accelerated along an 8 m flight path. Ultra-sensitive charge detectors monitor the passage of the projectiles at a rate of up to 100 projectiles/second. An online computer records and displays in real time the charge, velocity and mass of the projectiles and provides cross correlation between the events observed by the several in-flight charge detectors and impact detectors. Real-time logic controls an electrostatic kicker which deflects projectiles of selected charge and velocity onto the target. Thus each experiment consists of an ensemble of 10 to 40 impacts onto a single target within a narrow window of the projectile parameter space, providing excellent statistical resolution of each data point. The target materials used include single crystal copper and single crystal aluminum, gold, and quartz as well as pyrolytic graphic and epoxy used in composite materials of interest to space applications. We also conducted impact experiments onto thin Mylar and nickel foils. This paper presents these experiments and summarizes the cratering characterization performed to date. Emphasis is placed on cratering results in several materials over a range of impact velocities

  7. Morphology and chemistry of projectile residue in small experimental impact craters

    Science.gov (United States)

    Horz, F.; Fechtig, H.; Janicke, J.; Schneider, E.

    1983-01-01

    Small-scale impact craters (5-7 mm in diameter) were produced with a light gas gun in high purity Au and Cu targets using soda lime glass (SL) and man-made basalt glass (BG) as projectiles. Maximum impact velocity was 6.4 km/s resulting in peak pressures of approximately 120-150 GPa. Copious amounts of projectile melts are preserved as thin glass liners draping the entire crater cavity; some of this liner may be lost by spallation, however. SEM investigations reveal complex surface textures including multistage flow phenomena and distinct temporal deposition sequences of small droplets. Inasmuch as some of the melts were generated at peak pressures greater than 120 GPa, these glasses represent the most severely shocked silicates recovered from laboratory experiments to date. Major element analyses reveal partial loss of alkalis; Na2O loss of 10-15 percent is observed, while K2O loss may be as high as 30-50 percent. Although the observed volatile loss in these projectile melts is significant, it still remains uncertain whether target melts produced on planetary surfaces are severely fractionated by selective volatilization processes.

  8. Development and Execution of an Impact Cratering Application on a Computational Grid

    Directory of Open Access Journals (Sweden)

    E. Huedo

    2005-01-01

    Full Text Available Impact cratering is an important geological process of special interest in Astrobiology. Its numerical simulation comprises the execution of a high number of tasks, since the search space of input parameter values includes the projectile diameter, the water depth and the impactor velocity. Furthermore, the execution time of each task is not uniform because of the different numerical properties of each experimental configuration. Grid technology is a promising platform to execute this kind of applications, since it provides the end user with a performance much higher than that achievable on any single organization. However, the scheduling of each task on a Grid involves challenging issues due to the unpredictable and heterogeneous behavior of both the Grid and the numerical code. This paper evaluates the performance of a Grid infrastructure based on the Globus toolkit and the GridWay framework, which provides the adaptive and fault tolerance functionality required to harness Grid resources, in the simulation of the impact cratering process. The experiments have been performed on a testbed composed of resources shared by five sites interconnected by RedIRIS, the Spanish Research and Education Network.

  9. Geochemical characterization of impact glasses from the Zhamanshin crater by various modes of activation analysis. Remarks on genesis of irghizites

    Czech Academy of Sciences Publication Activity Database

    Mizera, Jiří; Řanda, Zdeněk; Tomandl, Ivo

    2012-01-01

    Roč. 293, č. 1 (2012), s. 359-376 ISSN 0236-5731 R&D Projects: GA ČR GA205/09/0991 Institutional support: RVO:67985891 ; RVO:61389005 Keywords : Zhamanshin crater * impact glass * irghizite Subject RIV: DD - Geochemistry Impact factor: 1.467, year: 2012

  10. 3d morphometric analysis of lunar impact craters: a tool for degradation estimates and interpretation of maria stratigraphy

    Science.gov (United States)

    Vivaldi, Valerio; Massironi, Matteo; Ninfo, Andrea; Cremonese, Gabriele

    2015-04-01

    In this study we have applied 3D morphometric analysis of impact craters on the Moon by means of high resolution DTMs derived from LROC (Lunar Reconnaissance Orbiter Camera) NAC (Narrow Angle Camera) (0.5 to 1.5 m/pixel). The objective is twofold: i) evaluating crater degradation and ii) exploring the potential of this approach for Maria stratigraphic interpretation. In relation to the first objective we have considered several craters with different diameters representative of the four classes of degradation being C1 the freshest and C4 the most degraded ones (Arthur et al., 1963; Wilhelms, 1987). DTMs of these craters were elaborated according to a multiscalar approach (Wood, 1996) by testing different ranges of kernel sizes (e.g. 15-35-50-75-100), in order to retrieve morphometric variables such as slope, curvatures and openness. In particular, curvatures were calculated along different planes (e.g. profile curvature and plan curvature) and used to characterize the different sectors of a crater (rim crest, floor, internal slope and related boundaries) enabling us to evaluate its degradation. The gradient of the internal slope of different craters representative of the four classes shows a decrease of the slope mean value from C1 to C4 in relation to crater age and diameter. Indeed degradation is influenced by gravitational processes (landslides, dry flows), as well as space weathering that induces both smoothing effects on the morphologies and infilling processes within the crater, with the main results of lowering and enlarging the rim crest, and shallowing the crater depth. As far as the stratigraphic application is concerned, morphometric analysis was applied to recognize morphologic features within some simple craters, in order to understand the stratigraphic relationships among different lava layers within Mare Serenitatis. A clear-cut rheological boundary at a depth of 200 m within the small fresh Linnè crater (diameter: 2.22 km), firstly hypothesized

  11. Multivariate analyses of crater parameters and the classification of craters

    Science.gov (United States)

    Siegal, B. S.; Griffiths, J. C.

    1974-01-01

    Multivariate analyses were performed on certain linear dimensions of six genetic types of craters. A total of 320 craters, consisting of laboratory fluidization craters, craters formed by chemical and nuclear explosives, terrestrial maars and other volcanic craters, and terrestrial meteorite impact craters, authenticated and probable, were analyzed in the first data set in terms of their mean rim crest diameter, mean interior relief, rim height, and mean exterior rim width. The second data set contained an additional 91 terrestrial craters of which 19 were of experimental percussive impact and 28 of volcanic collapse origin, and which was analyzed in terms of mean rim crest diameter, mean interior relief, and rim height. Principal component analyses were performed on the six genetic types of craters. Ninety per cent of the variation in the variables can be accounted for by two components. Ninety-nine per cent of the variation in the craters formed by chemical and nuclear explosives is explained by the first component alone.

  12. Mid-IR Reflectance (DRIFT) Spectral Variations in Basaltic Mineralogy with Direction of Impact at Lonar Crater, India

    Science.gov (United States)

    Basavaiah, N.; Chavan, R. S.; Arif, M.

    2012-12-01

    Identification of spectral changes with the direction of impact has important implications for understanding the impact cratering phenomenon occurring on both terrestrial and extraterrestrial planets and also for geology of the crater. Fortuitously, Lonar Impact Crater (India) is the only well-preserved terrestrial simple crater excavated on Deccan basalts and serves as an excellent analogue to craters on Mars and Moon. An ~570 ka old Lonar crater was suggested to be formed by an oblique impact of a chondritic impactor that struck the pre-impact target from the east into a sequence of six basaltic Deccan flows and created a 1.88 km diameter crater with two layers of ejecta blanket. Here we report preliminary laboratory studies of spectral results on fine-grained rock powers (IR (4000-400 cm-1) Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy. The basalts were collected from two profiles in the east and south sections of the crater wall and the upper most crater rim, which later subdivided into sector-wise samples to carry out a systematic study of spectral properties of Lonar basalts, together with impact related samples of breccias and impact melts. For the first time, data of the shock metamorphism of Lonar basalt is examined using DRIFT spectroscopy. Infrared spectra of rock powders of relatively unshocked and shocked basalts are obtained to document the mineralogical variations and the distribution of primary (e.g. Plagioclase Feldspar, Pyroxene), and secondary Phyllosilicate minerals (e.g. Illite, Smectite, Montmorillonite, Saponite, Serpentine) with direction of impact. The spectral data between pre-impact unshocked and post-impact shocked basalts are interpreted to reflect the effect of shock pressure and alteration that rock have undergone. On western crater rim sector, typical silicate spectral features in 900-1200 cm-1 which attributed to Si-O stretching, are observed to change slightly in the width and shift in position as a result of

  13. Chicxulub Impact Crater and Yucatan Carbonate Platform - Stratigraphy and Petrography of PEMEX Borehole Cores

    Science.gov (United States)

    Gutierrez-Cirlos, A. G.; Perez-Drago, G.; Perez-Cruz, L.; Urrutia-Fucugauchi, J.

    2008-12-01

    Chicxulub impact crater is the best preserved of the three large multi-ring structures documented in the terrestrial record. Chicxulub, formed 65 Ma ago, is associated with the Cretaceous/Tertiary (K/T) boundary layer and the impact related to the organism extinctions and events marking the boundary. The crater is buried under Tertiary sediments in the Yucatan carbonate platform in the southern Gulf of Mexico. The structure was initially recognized from gravity and magnetic anomalies in the PEMEX exploration surveys of the northwestern Yucatan peninsula. The exploration program included eight deep boreholes completed from 1952 through the 1970s. The investigations showing Chicxulub as a large complex impact crater formed at the K/T boundary have relayed on the PEMEX decades-long exploration program. However, despite frequent use of PEMEX information and core samples, significant parts of the database and cores remain to be evaluated, analyzed and incorporated with results from recent efforts. Access to PEMEX Core Repository has permitted to study the cores and collect new samples from some of the boreholes. We analyzed cores from Yucatan-6, Chicxulub-1, Sacapuc-1, Ticul-1, Yucatan-1 and Yucatan-4 boreholes to make new detailed stratigraphic correlations and petrographic characterization, using information from PEMEX database and the recent studies. In C-1 cores, breccias show 4-8 cm clasts of fine grained altered melt dispersed in a medium to coarse grained matrix composed of pyroxene and feldspar with little macroscopic alteration. Clasts contain 0.2 to 0.1 cm fragments of silicate material (basement) that show variable degrees of digestion. Melt samples from C-1 N10 comes from interval 1,393-1,394 m, and show a fine-to-medium grained coherent microcrystalline groundmass. Melt and breccias in Y-6 extend from about 1,100 m to more than 1,400 m. Sequence is well sorted, with an apparent gradation in both the lithic and melt clasts. In this presentation we report on

  14. Evidence of the impacting body of the Ries crater - the discovery of Fe-Cr-Ni veinlets below the crater bottom

    Science.gov (United States)

    El, Goresy A.; Chao, E.C.T.

    1976-01-01

    Fe-Cr-Ni particles and veinlets have been discovered in the top 15 m of the compressed zone with abundant shatter cones below the bottom of the Ries crater. The metallic particles are less than a few microns across. They occur in various minerals along healed intergranular and locally in intragranular microfractures in quartz diorite, amphibolite and chloritized granite of the basement crystalline rocks. The particles consist of major Fe, Cr, and Ni with minor Si and Ca. Origin due to contamination is absolutely ruled out. We believe that these Fe-Cr-Ni particles are probably condensed from the vaporized impacting body which produced the Ries crater. These particles were injected with high velocity into microfractures near the top of the compressed zone, implanted in and across various minerals before these microfractures were resealed. The presence of Si and Ca as well as the fact that the Cr content is nearly twice that of Ni, led us to conclude that the Ries impacting body is very likely not an iron meteorite but a stony meteorite. ?? 1976.

  15. The fourth Arab Impact Cratering and Astrogeology Conference (AICAC IV), April 9-12, 2017, Algiers (Algeria)

    Science.gov (United States)

    Belhaï, D.; Chennaoui-Aoudjehane, H.; Baratoux, D.; Ferrière, L.; Lamali, A.; Sahoui, R.; Lambert, P.; Ayadi, A.

    2017-09-01

    We present a report about the fourth Arab Impact Cratering and Astrogeology Conference (AICAC IV) that took place in Algiers at the USTHB (Université des Sciences et Technologie Houari Boumedienne, Algiers, Algeria) in the presence of the presidents of the USTHB and Boumerdès Universities, the Director of CRAAG (Centre de Recherche en Astronomie, Astrophysique et Géophysique), and the General Director of the National Administration for Scientific Research (NASR/DGRSDT). This series of conferences aims to promote research interest for impact cratering in the Arab world and beyond, including for instance in African countries. In spite of persistently restraining travel measures to Algeria, the fourth edition held in Algiers was marked by continuous international participation, with participants from seven different countries. This conference focused on presentations of scientific results in the research fields related to planetology, meteorites, and impact craters. In particular, the Algerian impact structures were under the spotlights during both oral and poster sessions. During this conference, the presence of freshly graduated Ph.D. students and new Ph.D. projects related to impact cratering or meteoritic science was a positive sign for the consolidation of research groups in this domain in the Arab world and Africa. Therefore, international cooperation or external support and funding are still needed to ensure the development of this scientific discipline in this part of the world.

  16. Chicxulub Impact Crater and Yucatan Carbonate Platform - PEMEX Oil Exploratory Wells Revisited

    Science.gov (United States)

    Pérez-Drago, G.; Gutierrez-Cirlos, A. G.; Pérez-Cruz, L.; Urrutia-Fucugauchi, J.

    2008-12-01

    Geophysical oil exploration surveys carried out by PEMEX in the 1940's revealed occurrence of an anomalous pattern of semi-circular concentric gravity anomalies. The Bouguer gravity anomalies covered an extensive area over the flat carbonate platform in the northwestern Yucatan Peninsula; strong density contrasts were suggestive of a buried igneous complex or basement uplift beneath the carbonates, which was referred as the Chicxulub structure. The exploration program carried out afterwards included a drilling program, starting with Chicxulub-1 well in 1952 and comprising eight deep boreholes through the 1970s. An aeromagnetic survey in late 1970's showed high amplitude anomalies in the gravity anomaly central sector. Thus, research showing Chicxulub as a large complex impact crater formed at the K/T boundary was built on the PEMEX decades-long exploration program. Despite frequent reference to PEMEX information and samples, original data and cores have not been openly available for detailed evaluation and integration with results from recent investigations. Core samples largely remain to be analyzed and interpreted in the context of recent marine, aerial and terrestrial geophysical surveys and the drilling/coring projects of UNAM and ICDP. In this presentation we report on the stratigraphy and paleontological data for PEMEX wells: Chicxulub- 1 (1582m), Sacapuc-1 (1530m), Yucatan-6 (1631m), Ticul-1 (3575m) Yucatan-4 (2398m), Yucatan-2 (3474m), Yucatan-5A (3003m) and Yucatan-1 (3221m). These wells remain the deepest drilled in Chicxulub, providing samples of impact lithologies, carbonate sequences and basement, which give information on post- and pre-impact stratigraphy and crystalline basement. We concentrate on stratigraphic columns, lateral correlations and integration with UNAM and ICDP borehole data. Current plans for deep drilling in Chicxulub crater target the peak ring and central sector, with offshore and onshore boreholes proposed to the IODP and ICDP

  17. Monte Carlo prediction of crater formation by single ion impact on solid surface

    International Nuclear Information System (INIS)

    Perez-Martin, A.M.C.; Dominguez-Vazquez, J.; Jimenez-Rodriguez, J.J.; Collins, R.; Gras-Marti, A.

    1994-01-01

    A method is presented for predicting the topography changes following the impact of one energetic ion on the plane surface of a monatomic amorphous solid. This is done in two stages. The first is a Monte Carlo calculation of the sputter yield and interior distribution relocated atoms, with no compensation for local departures from equilibrium density. In the second stage there is a systematic relaxation of the solid, in which the density returns to its previous constant value and a crater develops in the surface. Two alternative methods of carrying out stage two are compared. In the first the solid is subdivided into cells within which relaxation is carried out normal to the surface, as in previous one-dimensional studies. The second method treats the solid as a 3-dimensional incompressible medium. Both seem to reproduce quite well the main features found experimentally. (orig.)

  18. Candidates for multiple impact craters?: Popigai and Chicxulub as seen by the global high resolution gravitational field model EGM2008

    Czech Academy of Sciences Publication Activity Database

    Klokočník, Jaroslav; Kostelecký, J.; Pešek, I.; Novák, P.; Wagner, C. A.; Sebera, Josef

    2010-01-01

    Roč. 1, č. 1 (2010), s. 71-83 ISSN 1869-9510 Grant - others:ESA(XE) ESA- PECS project no. 98056 Institutional research plan: CEZ:AV0Z10030501 Keywords : impact craters * gravity field model EGM2008 * second radial derivatives Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  19. Municipal water reuse for urban agriculture in Namibia: Modeling nutrient and salt flows as impacted by sanitation user behavior.

    Science.gov (United States)

    Woltersdorf, L; Scheidegger, R; Liehr, S; Döll, P

    2016-03-15

    Adequate sanitation, wastewater treatment and irrigation infrastructure often lacks in urban areas of developing countries. While treated, nutrient-rich reuse water is a precious resource for crop production in dry regions, excessive salinity might harm the crops. The aim of this study was to quantify, from a system perspective, the nutrient and salt flows a new infrastructure connecting water supply, sanitation, wastewater treatment and nutrient-rich water reuse for the irrigation of agriculture, from a system perspective. For this, we developed and applied a quantitative assessment method to understand the benefits and to support the management of the new water infrastructure in an urban area in semi-arid Namibia. The nutrient and salt flows, as affected by sanitation user behavior, were quantified by mathematical material flow analysis that accounts for the low availability of suitable and certain data in developing countries, by including data ranges and by assessing the effects of different assumptions in cases. Also the nutrient and leaching requirements of a crop scheme were calculated. We found that, with ideal sanitation use, 100% of nutrients and salts are reclaimed and the slightly saline reuse water is sufficient to fertigate 10 m(2)/cap/yr (90% uncertainty interval 7-12 m(2)/cap/yr). However, only 50% of the P contained in human excreta could be finally used for crop nutrition. During the pilot phase fewer sanitation users than expected used slightly more water per capita, used the toilets less frequently and practiced open defecation more frequently. Therefore, it was only possible to reclaim about 85% of nutrients from human excreta, the reuse water was non-saline and contained less nutrient so that the P was the limiting factor for crop fertigation. To reclaim all nutrients from human excreta and fertigate a larger agricultural area, sanitation user behavior needs to be improved. The results and the methodology of this study can be generalized and

  20. Terrestrial Analogs for Surface Properties Associated with Impact Cratering on the Moon - Self-secondary Impact Features at Kings Bowl, Idaho

    Science.gov (United States)

    Matiella Novak, M. A.; Zanetti, M.; Neish, C.; Kukko, A.; Fan, K.; Heldmann, J.; Hughes, S. S.

    2017-12-01

    The Kings Bowl (KB) eruptive fissure and lava field, located in the southern end of Craters of the Moon National Monument, Idaho, is an ideal location for planetary analogue field studies of surface properties related to volcanic and impact processes. Here we look at possible impact features present in the KB lava field near the main vent that resulted in squeeze-ups of molten lava from beneath a semi-solid lava lake crust. These may have been caused by the ejection of blocks during the phreatic eruption that formed the Kings Bowl pit, and their subsequent impact into a partially solidified lava pond. We compare and contrast these features with analogous self-secondary impact features, such as irregular, rimless secondary craters ("splash craters") observed in lunar impact melt deposits, to better understand how self-secondary impacts determine the surface properties of volcanic and impact crater terrains. We do this by analyzing field measurements of these features, as well as high-resolution DEM data collected through the Kinematic LiDAR System (KLS), both of which give us feature dimensions and distributions. We then compare these data with self-secondary impact features on the Moon and related surface roughness constrained through Lunar Reconnaissance Orbiter observations (Mini-RF and LROC NACs). Possible self-secondary impact features can be found in association with many lunar impact craters. These are formed when ballistic ejecta from the crater falls onto the ejecta blanket and melt surrounding the newly formed crater. Self-secondary impact features involving impact melt deposits are particularly useful to study because the visibly smooth melt texture serves to highlight the impact points in spacecraft imagery. The unusual morphology of some of these features imply that they formed when the melt had not yet completely solidified, strongly suggesting a source of impactors from the primary crater itself. We will also discuss ongoing efforts to integrate field

  1. Brandburg Prominance, Namibia, Africa

    Science.gov (United States)

    1993-01-01

    The Brandburg Prominance, Namibia (21.0S, 14.5E) is a round basaltic plug and is the highest feature (over 8,000 ft) in the country. Wind streaks on the surface of the coastal desert, aligned northeast to southwest, are the result of frequent sand storms. Coastal stratus clouds provide most of the life supporting moisture as fog droplets in this arid land where annual rainfall may be less than a quarter of an inch for decades at a time.

  2. Mid-Latitude versus Polar-Latitude Transitional Impact Craters: Geometric Properties from Mars Orbiter Laser Altimeter (MOLA) Observations and Viking Images

    Science.gov (United States)

    Matias, A.; Garvin, J. B.; Sakimoto, S. E. H.

    1998-01-01

    One intriguing aspect of martian impact crater morphology is the change of crater cavity and ejecta characteristics from the mid-latitudes to the polar regions. This is thought to reflect differences in target properties such as an increasing presence of ice in the polar regions. Previous image-based efforts concerning martian crater morphology has documented some aspects of this, but has been hampered by the lack of adequate topography data. Recent Mars Orbiter Laser Altimeter (MOLA) topographic profiles provide a quantitative perspective for interpreting the detailed morphologies of martian crater cavities and ejecta morphology. This study is a preliminary effort to quantify the latitude-dependent differences in morphology with the goal of identifying target-dependent and crater modification effects from the combined of images and MOLA topography. We combine the available MOLA profiles and the corresponding Viking Mars Digital Image Mosaics (MDIMS), and high resolution Viking Orbiter images to focus on two transitional craters; one on the mid-latitudes, and one in the North Polar region. One MOLA pass (MGS Orbit 34) traverses the center of a 15.9 km diameter fresh complex crater located at 12.8degN 83.8degE on the Hesperian ridge plains unit (Hvr). Viking images, as well as MOLA data, show that this crater has well developed wall terraces and a central peak with 429 m of relative relief. Three MOLA passes have been acquired for a second impact crater, which is located at 69.5degN 41degE on the Vastitas Borealis Formation. This fresh rampart crater lacks terraces and central peak structures and it has a depth af 579 m. Correlation between images and MOLA topographic profiles allows us to construct basic facies maps of the craters. Eight main units were identified, four of which are common on both craters.

  3. University students and HIV in Namibia: an HIV prevalence survey and a knowledge and attitude survey

    NARCIS (Netherlands)

    de Beer, Ingrid H.; Gelderblom, Huub C.; Schellekens, Onno; Gaeb, Esegiel; van Rooy, Gert; McNally, Alta; Wit, Ferdinand W.; Rinke de Wit, Tobias F.

    2012-01-01

    Background: With an overall adult HIV prevalence of 15.3%, Namibia is facing one of the largest HIV epidemics in Africa. Young people aged 20 to 34 years constitute one of the groups at highest risk of HIV infection in Namibia. However, little is known about the impact of HIV on this group and its

  4. An investigation of Crater Diameter on Plain Slab Foamed Concrete Rice Husk Ash (FCRHA Exposed to Low Impact Loading

    Directory of Open Access Journals (Sweden)

    Hadipramana Josef

    2017-01-01

    Full Text Available As sustainable material building and construction, the foamed concrete (FC in this investigation was modified by adding the Rice Husk Ash (RHA as sand replacement to increase its strength. Furthermore, this modification material (is called FCRHA treated on impact loading. This investigation was motivated when the plain slab of FCRHA subjected to small impactor, then the nose impactor over all would penetrate into slab target due to porosity of FCRHA. The experimental produced plain slabs FCRHA and FC (as a control with 1400 kg/m3 and 1600 Kg/m3 of densities. In impact test all plain slabs exposed by 40 mm steel blunt nose impactor with various impact velocities. The result showed the crater which produced by impact loading was not found spalling, scabbing, radial crack and widely cratering. This local damage occurred when porosity of FCRHA took over the impact loading. The nose impactor over all considered have been successful penetrated into slab of FCRHA and FC. Therefore, the diameter of crater equals to diameter of impactor. With this certainty, the prediction penetration depth on plain slab FCRHA (also FC can be determined in future investigation. In addition, the penetration of impactor on FCRHA with low impact velocity give the same impression on penetration impactor with high impact velocity on FC.

  5. Deep Drilling Into the Chicxulub Impact Crater: Pemex Oil Exploration Boreholes Revisited

    Science.gov (United States)

    Fucugauchi, J. U.; Perez-Cruz, L.

    2007-05-01

    The Chicxulub structure was recognized in the 1940´s from gravity anomalies in oil exploration surveys by Pemex. Geophysical anomalies occur over the carbonate platform in NW Yucatan, where density and magnetic susceptibility contrasts with the carbonates suggested a buried igneous complex or basement uplift. The exploration program developed afterwards included several boreholes, starting with the Chicxulub-1 in 1952 and eventually comprising eight deep boreholes completed through the 1970s. The investigations showing Chicxulub as a large impact crater formed at the K/T boundary have relayed on the Pemex decades-long exploration program. Despite frequent reference to Pemex information, original data have not been openly available for detailed evaluation and incorporation with results from recent efforts. Logging data and core samples remain to be analyzed, reevaluated and integrated in the context of recent marine, aerial and terrestrial geophysical surveys and the drilling/coring projects of UNAM and ICDP. In this presentation we discuss the paleontological data, stratigraphic columns and geophysical logs for the Chicxulub-1 (1582m), Sacapuc-1 (1530m), Yucatan-6 (1631m) and Ticul-1 (3575m) boreholes. These boreholes remain the deepest ones drilled in Chicxulub and the only ones providing samples of the melt-rich breccias and melt sheet. Other boreholes include the Y1 (3221m), Y2 (3474m), Y4 (2398m) and Y5A (3003m), which give information on pre-impact stratigraphy and crystalline basement. We concentrate on log and microfossil data, stratigraphic columns, lateral correlation, integration with UNAM and ICDP borehole data, and analyses of sections of melt, impact breccias and basal Paleocene carbonates. Current plans for deep drilling in Chicxulub crater focus in the peak ring zone and central sector, with proposed marine and on-land boreholes to the IODP and ICDP programs. Future ICDP borehole will be located close to Chicxulub-1 and Sacapuc-1, which intersected

  6. Shock pressure estimation in basement rocks of the Chicxulub impact crater using cathodoluminescence spectroscopy of quartz

    Science.gov (United States)

    Tomioka, N.; Tani, R.; Kayama, M.; Chang, Y.; Nishido, H.; Kaushik, D.; Rae, A.; Ferrière, L.; Gulick, S. P. S.; Morgan, J. V.

    2017-12-01

    The Chicxulub impact structure, located in the northern Yucatan Peninsula, Mexico, was drilled by the joint IODP-ICDP Expedition 364 in April-May 2016. This expedition is the first attempt to obtain materials from the topographic peak ring within the crater previously identified by seismic imaging. A continuous core was successfully recovered from the peak ring at depths between 505.7 and 1334.7 mbsf. Uplifted, fractured, and shocked granitic basement rocks forming the peak ring were found below, in the impact breccia and impact melt rock unit (747.0-1334.7 mbsf; Morgan et al. 2016). In order to constrain impact crater formation, we investigated shock pressure distribution in the peak-ring basement rocks. Thin sections of the granitic rocks were prepared at intervals of 60 m. All the samples contains shocked minerals, with quartz grains frequently showing planar deformation features (PDFs). We determined shock pressures based on the cathodoluminescence (CL) spectroscopy of quartz. The strong advantage of the CL method is its applicability to shock pressure estimation for individual grains for both quartz and diaplectic SiO2 glass with high-spatial resolution ( 1 μm) (Chang et al. 2016). CL spectra of quartz shows a blue emission band caused by shock-induced defect centers, where its intensity increases with shock pressure. A total of 108 quartz grains in ten thin sections were analyzed using a scanning electron microscope with a CL spectrometer attached (an acceleration voltage of 15 kV and a beam current of 2 nA were used). Natural quartz single crystals, which were experimentally shocked at 0-30 GPa, were used for pressure calibration. CL spectra of all the quartz grains in the basement rocks showed broad blue emission band at the wavelength range of 300-500 nm and estimated shock pressures were in the range of 15-20 GPa. The result is consistent with values obtained from PDFs analysis in quartz using the universal stage (Ferrière et al. 2017; Rae et al. 2017

  7. Relaxed impact craters on Ganymede: Regional variation and high heat flows

    Science.gov (United States)

    Singer, Kelsi N.; Bland, Michael T.; Schenk, Paul M.; McKinnon, William B.

    2018-01-01

    Viscously relaxed craters provide a window into the thermal history of Ganymede, a satellite with copious geologic signs of past high heat flows. Here we present measurements of relaxed craters in four regions for which suitable imaging exists: near Anshar Sulcus, Tiamat Sulcus, northern Marius Regio, and Ganymede's south pole. We describe a technique to measure apparent depth, or depth of the crater with respect to the surrounding terrain elevation. Measured relaxation states are compared with results from finite element modeling to constrain heat flow scenarios [see companion paper: Bland et al. (2017)]. The presence of numerous, substantially relaxed craters indicates high heat flows—in excess of 30–40 mW m−2 over 2 Gyr, with many small (heat flows. Crater relaxation states are bimodal for some equatorial regions but not in the region studied near the south pole, which suggests regional variations in Ganymede's thermal history.

  8. Relaxed impact craters on Ganymede: Regional variation and high heat flows

    Science.gov (United States)

    Singer, Kelsi N.; Bland, Michael T.; Schenk, Paul M.; McKinnon, William B.

    2018-05-01

    Viscously relaxed craters provide a window into the thermal history of Ganymede, a satellite with copious geologic signs of past high heat flows. Here we present measurements of relaxed craters in four regions for which suitable imaging exists: near Anshar Sulcus, Tiamat Sulcus, northern Marius Regio, and Ganymede's south pole. We describe a technique to measure apparent depth, or depth of the crater with respect to the surrounding terrain elevation. Measured relaxation states are compared with results from finite element modeling to constrain heat flow scenarios [see companion paper: Bland et al. (2017)]. The presence of numerous, substantially relaxed craters indicates high heat flows-in excess of 30-40 mW m-2 over 2 Gyr, with many small (heat flows. Crater relaxation states are bimodal for some equatorial regions but not in the region studied near the south pole, which suggests regional variations in Ganymede's thermal history.

  9. Regolith thickness over Sinus Iridum: Results from morphology and size-frequency distribution of small impact craters

    Science.gov (United States)

    Fa, Wenzhe; Liu, Tiantian; Zhu, Meng-Hua; Haruyama, Junichi

    2014-08-01

    High-resolution optical images returned from recent lunar missions provide a new chance for estimation of lunar regolith thickness using morphology and the size-frequency distribution of small impact craters. In this study, regolith thickness over the Sinus Iridum region is estimated using Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Cameras (NACs) images. A revised relationship between crater geometry and regolith thickness is proposed based on old experimental data that takes into considering the effect of the illumination angle of the images. In total, 227 high-resolution LROC NAC images are used, and 378,556 impact craters with diameters from 4.2 to 249.8 m are counted, and their morphologies are identified. Our results show that 50% of the Sinus Iridum region has a regolith thickness between 5.1 and 10.7 m, and the mean and median regolith thicknesses are 8.5 and 8.0 m, respectively. There are substantial regional variations in the regolith thickness, with its median value varying from 2.6 to 12.0 m for most regions. Local variations of regolith thickness are found to be correlated with the lunar surface age: the older the surface, the greater the thickness. In addition, sporadically distributed impact ejecta and crater rays are associated with relatively larger regolith thickness, which might result from excavation and transport of materials during the formation of the secondaries of Copernican-aged craters. Our estimated regolith thickness can help with future analysis of Chang'E-3 lunar penetrating radar echoes and studies of the subsurface stratigraphic structure of the Moon.

  10. Ponds, Flows, and Ejecta of Impact Cratering and Volcanism: A Remote Sensing Perspective of a Dynamic Moon

    Science.gov (United States)

    Stopar, Julie D.

    Both volcanism and impact cratering produce ejecta and associated deposits incorporating a molten rock component. While the heat sources are different (exogenous vs. endogenous), the end results are landforms with similar morphologies including ponds and flows of impact melt and lava around the central crater. Ejecta from both impact and volcanic craters can also include a high percentage of melted rock. Using Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC) images, crucial details of these landforms are finally revealed, suggesting a much more dynamic Moon than is generally appreciated. Impact melt ponds and flows at craters as small as several hundred meters in diameter provide empirical evidence of abundant melting during the impact cratering process (much more than was previously thought), and this melt is mobile on the lunar surface for a significant time before solidifying. Enhanced melt deposit occurrences in the lunar highlands (compared to the mare) suggest that porosity, target composition, and pre-existing topography influence melt production and distribution. Comparatively deep impact craters formed in young melt deposits connote a relatively rapid evolution of materials on the lunar surface. On the other end of the spectrum, volcanic eruptions have produced the vast, plains-style mare basalts. However, little was previously known about the details of small-area eruptions and proximal volcanic deposits due to a lack of resolution. High-resolution images reveal key insights into small volcanic cones (0.5-3 km in diameter) that resemble terrestrial cinder cones. The cones comprise inter-layered materials, spatter deposits, and lava flow breaches. The widespread occurrence of the cones in most nearside mare suggests that basaltic eruptions occur from multiple sources in each basin and/or that rootless eruptions are relatively common. Morphologies of small-area volcanic deposits indicate diversity in eruption behavior of lunar basaltic

  11. The Submarine 4-km diameter Corossol Crater, Eastern Canada: Evidence for an impact origin

    Science.gov (United States)

    Higgins, Michael D.; Lajeunesse, Patrick; St-Onge, Guillaume; Locat, Jacques; Sanfacon, Richard; Duchesne, Mathieu J.

    2014-05-01

    The newly-discovered Corossol Crater lies in the northwestern Gulf of St. Lawrence (Eastern Canada; 50°3'N, 66°23'W) and was found in 40-185 metres of water using high-resolution multibeam sonar. It is a 4 km in diameter complex circular structure with a central uplift and concentric rings. Glacial resurfacing indicates that it predates the last phase of glaciation in this area. Dredging on the central uplift recovered many angular clasts of hard grey limestone, which forms the bedrock in much of this area. One 4 cm clast of limestone breccia is somewhat different from the other blocks and has characteristics that suggest that it is an impact breccia. The block comprises fragments of calcite limestone up to 2 mm long. In many parts of the block these fragments have thin black rims. At the edges of the block these rims are brown, presumably reflecting aqueous alteration. Mineral grains in the rims are too small to characterize, but the fact that the ensemble can be oxidized suggests that it contains sulfides. In places the block is cut by veins of fine-grained calcite with euhedral dolomite crystals. The most unusual component is rare droplets up to 2 mm long, commonly fragmented. The droplets comprise a glassy matrix with a composition very close to fluorapatite and opaque crystals that have a composition close to pyrite. A few droplets have up to 5% vesicles. Fluorapatite requires fusion temperatures of about 1600 C, which cannot be achieved at the surface of the Earth by endogenous processes. A single fragmented quartz crystal with planar features was found close to one droplet. Universal stage measurements of the orientation of the planar features give an angle of 42 degrees which is close to that of {10-13} planes. This is the most common set of deformation planes produced during shock metamorphism of quartz. Unfortunately no other grains were found with similar planes. The glassy droplets and shocked quartz together suggest that the clast was produced by an

  12. Buried Craters of Utopia

    Science.gov (United States)

    2003-01-01

    MGS MOC Release No. MOC2-365, 19 May 2003Beneath the northern plains of Mars are numerous buried meteor impact craters. One of the most heavily-cratered areas, although buried, occurs in Utopia Planitia, as shown in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image. The history of Mars is complex; impact craters provide a tool by which to understand some of that history. In this case, a very ancient, cratered surface was thinly-buried by younger material that is not cratered at all. This area is near 48.1oN, 228.2oW; less than 180 km (112 mi) west of the Viking 2 lander site. Sunlight illuminates the scene from the lower left.

  13. IODP-ICDP Expedition 364: Drilling the Chicxulub impact crater to understand planetary evolution and mass extinction

    Science.gov (United States)

    Gulick, S. P. S.; Morgan, J. V.

    2017-12-01

    The most recent of Earth's five largest mass extinction events occurred 66 Ma, coeval with the impact of a 12 km asteroid, striking at 60 degrees into what is today the Yucatán Peninsula, México, producing the 200 km-wide Chicxulub crater. This impact, by some estimations, drove the extinction of 75% of life on Earth at the genus level. The mass extinction event marks the boundary between the Cretaceous and Paleogene. Proposed kill mechanisms include thermal effects caused by the reentry of fast ejecta into Earth's atmosphere, dust and sulfate aerosols reducing Earth's solar insolation, ocean acidification, and metal toxicity due to the chemical make-up of the impactor. The magnitude and duration of these processes is still debated, and further evaluation of the proposed kill mechanisms requires an understanding of the mechanics of the Chicxulub impact as well as the resulting global environmental perturbations. In April and May 2016, the International Ocean Discovery Program, with co-funding from the International Continental Scientific Drilling Program, successfully cored into the Chicxulub impact crater with nearly 100% recovery. These cores include the first-ever samples of the transition from an intact peak ring through post-impact sediments. A peak ring is a discontinuous ring of mountains observed within the central basin of all large impact craters on rocky planets. Newly drilled cores include the uplifted target rocks, melt-rich impactites, hydrothermal deposits, a possible settling layer, and the resumption of carbonate sedimentation. The discovery that Chicxulub's peak ring consists of largely granitic crust uplifted by 10 km calibrates impact models and allows for observation of impact processes. At the top of the peak ring, the K-Pg boundary deposit includes a impactite sequence 130 m thick deposited by processes that range from minutes to likely years post-impact. This sequence is then overprinted by hydrothermal processes that lasted at least 100s

  14. Natural occurrence of pure nano-polycrystalline diamond from impact crater

    Science.gov (United States)

    Ohfuji, Hiroaki; Irifune, Tetsuo; Litasov, Konstantin D.; Yamashita, Tomoharu; Isobe, Futoshi; Afanasiev, Valentin P.; Pokhilenko, Nikolai P.

    2015-10-01

    Consolidated bodies of polycrystalline diamond with grain sizes less than 100 nm, nano-polycrystalline diamond (NPD), has been experimentally produced by direct conversion of graphite at high pressure and high temperature. NPD has superior hardness, toughness and wear resistance to single-crystalline diamonds because of its peculiar nano-textures, and has been successfully used for industrial and scientific applications. Such sintered nanodiamonds have, however, not been found in natural mantle diamonds. Here we identified natural pure NPD, which was produced by a large meteoritic impact about 35 Ma ago in Russia. The impact diamonds consist of well-sintered equigranular nanocrystals (5-50 nm), similar to synthetic NPD, but with distinct [111] preferred orientation. They formed through the martensitic transformation from single-crystal graphite. Stress-induced local fragmentation of the source graphite and subsequent rapid transformation to diamond in the limited time scale result in multiple diamond nucleation and suppression of the overall grain growth, producing the unique nanocrystalline texture of natural NPD. A huge amount of natural NPD is expected to be present in the Popigai crater, which is potentially important for applications as novel ultra-hard material.

  15. Probing the Hidden Geology of Isidis Planitia (Mars with Impact Craters

    Directory of Open Access Journals (Sweden)

    Graziella Caprarelli

    2015-02-01

    Full Text Available In this study we investigated Isidis Planitia, a 1325 km diameter multi-ring impact basin intersecting the Martian hemispheric dichotomy, located in the eastern hemisphere, between Syrtis Major and Utopia Planitia. From Mars Orbiter Laser Altimeter gridded data we observed that in the center of Isidis the −3700 m and −3800 m isolines strike NW-SE, being quasi-parallel to the diameter of the basin. We interpreted this as evidence that the basement of Isidis Planitia was faulted prior to being completely covered by layers of sediments and volcanic rocks. Plotting the morphometric data of impact craters located on the floor of the basin in a measured depths vs. predicted depths diagram (MPD, we concluded that the fault planes should dip SW, which is consistent with the location of the most topographically depressed sector of Isidis Planitia. We also estimated a minimum vertical displacement of ~1–2 km. Considering that the crust under Isidis Planitia is only a few km thick, our estimate implies brittle behavior of the lithosphere under the basin, suggesting that a low geothermal gradient and rheologically strong material characterize this Martian location.

  16. Determinants of fertility in Namibia

    African Journals Online (AJOL)

    AJRH Managing Editor

    This examines the fertility trends in Namibia over the past 2 decades .... contraceptive use was small because of the late age at first ..... limited flexibility in terms of maternity leave conditions ... Longer periods in education have increased the.

  17. Cutting Craters

    Science.gov (United States)

    2003-01-01

    [figure removed for brevity, see original site] Released 12 November 2003The rims of two old and degraded impact craters are intersected by a graben in this THEMIS image taken near Mangala Fossa. Yardangs and low-albedo wind streaks are observed at the top of the image as well as interesting small grooves on the crater floor. The origin of these enigmatic grooves may be the result of mud or lava and volatile interactions. Variable surface textures observed in the bottom crater floor are the result of different aged lava flows.Image information: VIS instrument. Latitude -15.2, Longitude 219.2 East (140.8 West). 19 meter/pixel resolution.Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  18. Mud volcanism and morphology of impact craters in Utopia Planitia on Mars: Evidence for the ancient ocean

    Science.gov (United States)

    Ivanov, Mikhail A.; Hiesinger, H.; Erkeling, G.; Reiss, D.

    2014-01-01

    Results of our detailed geological mapping and interpretation of the nature and relative and absolute model ages of units and structures in the SW portion of Utopia Planitia (20-45°N, 100-120°E) suggest the following. (1) The size-frequency distribution (SFD) of craters that both are buried by materials of the Vastitas Borealis units (VB) and superpose its surface indicate that the absolute model ages of terrain predating the emplacement of the VB is ˜3.7 Ga. (2) Lack of craters that are partly embayed by materials of the VB in the SW portion of Utopia Planitia implies that the emplacement of the VB was faster than the rate of accumulation of impact craters and is consistent with the geologically short time of emplacement of the VB due to catastrophic release of water from outflow channels (e.g., Carr, M.H. [1996]. Water on Mars. Oxford University Press, New York, p. 229). (3) The SFD of craters that superpose the surface of the VB indicates an absolute model age of ˜3.6-3.5 Ga. The absolute model ages of etched flows, which represent the upper stratigraphic limit of the VB, are estimated to be ˜3.5 Ga. (4) The majority of the larger (i.e., >1 km) impact craters show ejecta morphologies (rampart and pancake-like ejecta) that are indicative of the presence of ice/water in the target materials. The distal portions of the pancake-like ejecta are heavily degraded (not due to embayment). This suggests that these craters formed in targets that contained higher abundances of volatiles. (5) The diameter ranges of the craters with either rampart- or pancake-like ejecta are overlapping (from ˜2 to ˜60 km). Craters with pancake-like ejecta are concentrated within the central portion of the Utopia basin (less than ˜1000 km from the basin center) and rampart craters occur at the periphery of the basin. This pattern of the crater spatial distribution suggests that materials within the center of Utopia Planitia contained more ice/water. (6) Etched flows around the central

  19. Shock-induced kelyphite formation in the core of a complex impact crater

    Science.gov (United States)

    Deseta, Natalie; Boonsue, Suporn; Gibson, Roger L.; Spray, John G.

    2017-10-01

    We present a compositional and textural analysis of shock-induced microtextures in garnet porphyroblasts in migmatitic garnet-cordierite-biotite paragneisses from the centre of the Vredefort impact structure, South Africa. Detailed imaging and major element analysis of deformation features in, and adjacent to, the garnet porphyroblasts record a complex, heterogeneous distribution of shock effects at the microscale. As the most competent silicate mineral in the assemblage, with the highest Hugoniot Elastic Limit and a wide pressure-temperature stability field, the porphyroblastic garnet preserves a more diverse shock deformation response compared to minerals such as quartz and feldspar, which underwent more comprehensive shock metamorphism and subsequent annealing. The garnet porphyroblasts display pre-impact fractures that are overprinted by later intra-granular Hertzian and distinctive planar fractures associated with the impact event. Shock-induced strain localization occurred along internal slip planes and defects, including pre-existing fractures and inclusion boundaries in the garnet. Symplectitic (kelyphitic) coronas commonly enclose the garnet porphyroblasts, and inhabit intra-granular fractures. The kelyphite assemblage in fractures with open communication beyond garnet grain boundaries is characterized by orthopyroxene—cordierite—sapphirine. Conversely, the kelyphite assemblage in closed-off intra-granular fractures is highly variable, comprising spatially restricted combinations of a secondary garnet phase with a majoritic component, Al-rich orthopyroxene, sapphirine and cordierite. The impedance contrast between garnet porphyroblasts and their inclusions further facilitated the formation of shock-induced features (Al-rich orthopyroxene coronas). Together, the textural and mineralogical data suggest that these features provide a record of oscillatory shock perturbations initiated under confining pressure beneath the transient crater floor. This

  20. Investigation of Secondary Craters in the Saturnian System

    Science.gov (United States)

    Hoogenboom, T.; Schenk, P.; White, O. L.

    2012-03-01

    To derive accurate ages using impact craters, the impact source must be determined. We investigate secondary crater size, frequency, distribution, formation, and crater chain formation on icy satellites throughout the Jupiter and Saturn systems.

  1. Polygons on Crater Floor

    Science.gov (United States)

    2003-01-01

    MGS MOC Release No. MOC2-357, 11 May 2003This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows a pattern of polygons on the floor of a northern plains impact crater. These landforms are common on crater floors at high latitudes on Mars. Similar polygons occur in the arctic and antarctic regions of Earth, where they indicate the presence and freeze-thaw cycling of ground ice. Whether the polygons on Mars also indicate water ice in the ground is uncertain. The image is located in a crater at 64.8oN, 292.7oW. Sunlight illuminates the scene from the lower left.

  2. Surface Composition Near the Trailing Hemisphere Apex on Europa: The Manannán Impact Crater and Neighboring Terrain

    Science.gov (United States)

    Dalton, J. B.; Prockter, L. M.; Shirley, J. H.; Kamp, L.; Phillips, C. B.; Valenti, M.

    2012-12-01

    The Manannán impact crater and surrounding areas were imaged by Galileo's Near Infrared Mapping Spectrometer (NIMS) during the C3 orbital encounter. We have applied a linear mixture model based on cryogenic infrared reflectance spectroscopy to a "despiked" version of this NIMS observation (C3ENLINEA01A) to estimate abundances of sulfuric acid hydrate, hydrated sulfate salts, water ice and brines in surface exposures. Here we supplement our previously reported abundance estimates (Dalton et al., 2011) with additional results from our ongoing investigation. New geologic mapping precisely registered to the NIMS observation allows the extraction of high-quality near-infrared spectra specific to individual geologic units and morphological features. Detailed high resolution geologic mapping indicates the likely presence of extensive deposits of impact melt materials largely filling the crater floor (Moore et al. 2001), together with surrounding continuous ejecta deposits that may have been excavated from Europa's interior. We find that the crater floor and nearby ejecta exhibit low sulfuric acid abundance relative to the surroundings, with the abundance increasing with radial distance. Where the ejecta begins to thin and break up, the spectral mixture resembles a combination of pre-existing, high-acid-content materials and cleaner, excavated water ice. Several geologic units exhibit significantly lower sulfuric acid hydrate than expected for this region near the trailing hemisphere apex, varying from 53-64 wt% over the observation. This suggests that these surface units have received a reduced cumulative radiation dose (electrons and ions) compared to nearby terrain; this in turn implies geologic youth. We will present model compositions for several of Manannán's key stratigraphic units, including the crater floor deposits and the adjacent chaos and linea. We will interpret these results in the context of ongoing investigations of the interplay of exogenic and

  3. Characterization of impact materials around Barringer Meteor Crater by micro-PIXE and micro-SRXRF techniques

    Energy Technology Data Exchange (ETDEWEB)

    Uzonyi, I. E-mail: uzonyi@atomki.hu; Szoeor, Gy.; Rozsa, P.; Vekemans, B.; Vincze, L.; Adams, F.; Drakopoulos, M.; Somogyi, A.; Kiss, A.Z

    2004-06-01

    A combined micro-PIXE and micro-SRXRF method has been tested successfully for the characterization of impact materials collected at the well-known Barringer Meteor Crater. The micro-PIXE technique proved to be sensitive in the Z{<=}28 atomic number region while the micro-SRXRF above Fe especially for the siderophile elements. Quantitative analysis has become available for about 40 elements by these complementary methods providing new perspectives for the interpretation of the formation mechanism of impact metamorphosed objects.

  4. The impact of stigma, experience, and group referent on HIV risk assessments and HIV testing intentions in Namibia.

    Science.gov (United States)

    Smith, Rachel A; Morrison, Daniel

    2006-11-01

    People often perceive risks for others and themselves differently. This study examines whether personal beliefs about HIV and experience with those living with HIV influence personal risk assessments of contracting HIV in an interview sample of northern Namibians (N=400), but not others' assessments as explained by singular-distribution theory [Klar, Medding, & Sarel (1996). Nonunique invulnerability: Singular versus distributional probabilities and unrealistic optimism in comparative risk judgments. Organizational Behavior and Human Decision Processes, 67, 229-245]. Findings indicate that personal risk perceptions decrease with more HIV stigmatizing beliefs and increase with greater experience, but that those characteristics had no impact on assessments for others' risk. The study also examines whether the size and characteristics of the referent group, peers and the general Namibian population, influence others' risk assessments. Optimistic biases for personal risk versus others' risk appear with the highest discrepancy emerging between personal and general population risk assessments. Further, we found that personal risk perceptions did not mediate the relationship between personal characteristics, beliefs and experiences, and intentions to seek HIV testing.

  5. Is There any Relationship Between the Santa Elena Depression and Chicxulub Impact Crater, Northwestern Yucatan Peninsula, Mexico?

    Science.gov (United States)

    Lefticariu, L.

    2005-05-01

    The Terminal Cretaceous Chicxulub Impact Crater had a strong control on the depositional and diagenetic history of the northern Yucatan Platform during most of the Cenozoic Era. The Chicxulub Sedimentary Basin (henceforth Basin), which approximately coincides with the impact crater, is circumscribed by a concentration of karstic sinkholes known as the Ring of Cenotes. Santa Elena Depression (henceforth Depression) is the name proposed for the bowl-shaped buried feature, first contoured by geophysical studies, immediately south of the Basin, in the area where the Ticul 1 and UNAM 5 wells were drilled. Lithologic, petrographic, and biostratigraphic data on PEMEX, UNAM, and ICDP cores show that: 1) Cenozoic deposits are much thicker inside the Basin than inside the Depression, 2) in general, the Cenozoic formations from inside the Depression are the thickest among those outside the Basin, 3) variably dolomitized pelagic or outer-platform wackestone or mudstone occur both inside the Basin and Depression, 4) the age of the deeper-water sedimentary carbonate rocks is Paleocene-Eocene inside the Basin and Paleocene?-Early Eocene inside the Depression, 5) the oldest formations that crop out are of Middle Eocene age at the edge of the Basin and Early-Middle Eocene age inside the Depression, 6) saline lake deposits, that consist chiefly of anhydrite, gypsum, and fine carbonate, and also contain quartz, chert, clay, zeolite, potassium feldspar, pyrite, and fragments of wood, are present in the Cenozoic section of the UNAM 5 core between 282 and 198 m below the present land surface, 7) the dolomite, subaerial exposure features (subaerial crusts, vugs, karst, dedolomite), and vug-filling cement from the Eocene formations are more abundant inside the Depression than inside the Basin. The depositional environments that are proposed for explaining the Cenozoic facies succession within the Santa Elena Depression are: 1) deeper marine water (Paleocene?-Early Eocene), 2) relatively

  6. The Wells Creek Meteorite Impact Site and Changing Views on Impact Cratering

    Science.gov (United States)

    Ford, J. R. H.; Orchiston, Wayne; Clendening, Ron

    2012-11-01

    Wells Creek is a confirmed meteorite impact site in Tennessee, USA. The Wells Creek structure was first noticed by railroad surveyors around 1855 and brought to the attention of J.M. Safford, Tennessee's State Geologist. He included an insert in the 1869 Geologic Map of Tennessee, which is the first known map to include the structure. The origin of the Wells Creek structure was controversial, and was interpreted as being either the result of volcanic steam explosion or meteorite impact. It was only in the 1960s that Wilson and Stearns were able to state that the impact hypothesis was preferred. Evidence for a Wells Creek meteorite impact includes drill core results, extreme brecciation and shatter cones, while a local lack of volcanic material is telling. Just to the north of the Wells Creek Basin are three small basins that Wilson concluded were associated with the Wells Creek impact event, but evidence regarding the origin of the Austin, Indian Mound and Cave Spring Hollow sites is not conclusive.

  7. Craters on comets

    Science.gov (United States)

    Vincent, J.; Oklay, N.; Marchi, S.; Höfner, S.; Sierks, H.

    2014-07-01

    This paper reviews the observations of crater-like features on cometary nuclei. ''Pits'' have been observed on almost all cometary nuclei but their origin is not fully understood [1,2,3,4]. It is currently assumed that they are created mainly by the cometary activity with a pocket of volatiles erupting under a dust crust, leaving a hole behind. There are, however, other features which cannot be explained in this way and are interpreted alternatively as remnants of impact craters. This work focusses on the second type of pit features: impact craters. We present an in-depth review of what has been observed previously and conclude that two main types of crater morphologies can be observed: ''pit-halo'' and ''sharp pit''. We extend this review by a series of analysis of impact craters on cometary nuclei through different approaches [5]: (1) Probability of impact: We discuss the chances that a Jupiter Family Comet like 9P/Tempel 1 or the target of Rosetta 67P/Churyumov-Gerasimenko can experience an impact, taking into account the most recent work on the size distribution of small objects in the asteroid Main Belt [6]. (2) Crater morphology from scaling laws: We present the status of scaling laws for impact craters on cometary nuclei [7] and discuss their strengths and limitations when modeling what happens when a rocky projectile hits a very porous material. (3) Numerical experiments: We extend the work on scaling laws by a series of hydrocode impact simulations, using the iSALE shock physics code [8,9,10] for varying surface porosity and impactor velocity (see Figure). (4) Surface processes and evolution: We discuss finally the fate of the projectile and the effects of the impact-induced surface compaction on the activity of the nucleus. To summarize, we find that comets do undergo impacts although the rapid evolution of the surface erases most of the features and make craters difficult to detect. In the case of a collision between a rocky body and a highly porous

  8. The origin of Phobos grooves from ejecta launched from impact craters on Mars: Tests of the hypothesis

    Science.gov (United States)

    Ramsley, Kenneth R.; Head, James W.

    2013-01-01

    The surface of the martian moon Phobos is characterized by parallel and intersecting grooves that bear resemblance to secondary crater chains observed on planetary surfaces. Murray (2011) has hypothesized that the main groove-forming process on Phobos is the intersection of Phobos with ejecta from primary impact events on Mars to produce chains of secondary craters. The hypothesis infers a pattern of parallel jets of ejecta, either fluidized or solidified, that break into equally-spaced fragments and disperse uniformly along-trajectory during the flight from Mars to Phobos. At the moment of impact with Phobos the dispersed fragments emplace secondary craters that are aligned along strike corresponding to the flight pattern of ejecta along trajectory. The aspects of the characteristics of grooves on Phobos cited by this hypothesis that might be explained by secondary ejecta include: their observed linearity, parallelism, planar alignment, pitted nature, change in character along strike, and a "zone of avoidance" where ejecta from Mars is predicted not to impact (Murray, 2011). To test the hypothesis we plot precise Keplerian orbits for ejecta from Mars (elliptical and hyperbolic with periapsis located below the surface of Mars). From these trajectories we: (1) set the fragment dispersion limits of ejecta patterns required to emplace the more typically well-organized parallel grooves observed in returned images from Phobos; (2) plot ranges of the ejecta flight durations from Mars to Phobos and map regions of exposure; (3) utilize the same exposure map to observe trajectory-defined ejecta exposure shadows; (4) observe hemispheric exposure in response to shorter and longer durations of ejecta flight; (5) assess the viability of ejecta emplacing the large family of grooves covering most of the northern hemisphere of Phobos; and (6) plot the arrival of parallel lines of ejecta emplacing chains of craters at oblique incident angles. We also assess the bulk volume of

  9. The Chicxulub Multiring Impact Crater and the Cretaceous/Paleogene Boundary: Results From Geophysical Surveys and Drilling

    Science.gov (United States)

    Urrutia-Fucugauchi, J.; Perez-Cruz, Ligia

    2010-03-01

    The Chicxulub crater has attracted considerable attention as one of the three largest terrestrial impact structures and its association with the Cretaceous/Paleogene boundary (K/Pg). Chicxulub is a 200 km-diameter multi-ring structure formed 65.5 Ma ago in the Yucatan carbonate platform in the southern Gulf of Mexico and which has since been buried by Paleogene and Neogene carbonates. Chicxulub is one of few large craters with preserved ejecta deposits, which include the world-wide K/Pg boundary clay layer. The impact has been related to the global major environmental and climatic effects and the organism mass extinction that mark the K/Pg boundary, which affected more than 70 % of organisms, including the dinosaurs, marine and flying reptiles, ammonites and a large part of the marine microorganisms. The impact and crater formation occur instantaneously, with excavation of the crust down to 25 km depths in fractions of second and lower crust uplift and crater formation in a few hundreds of seconds. Energy released by impact and crustal deformation generates seismic waves traveling the whole Earth, and resulting in intense fracturing and deformation at the target site. Understanding of the physics of impacts on planetary surfaces and modeling of processes of crustal deformation, rheological behavior of materials at high temperatures and pressures remain a major challenge in geosciences. Study of the Chicxulub crater and the global effects and mass extinction requires inter- and multidisciplinary approaches, with researchers from many diverse fields beyond the geosciences. With no surface exposures, geophysical surveys and drilling are required to study the crater. Differential compaction between the impact breccias and the surrounding carbonate rocks has produced a ring-fracture structure that at the surface reflects in a small topographic depression and the karstic cenote ring. The crater structure, located half offshore and half on-land, has been imaged by

  10. Power-Law Scaling of the Impact Crater Size-Frequency Distribution on Pluto: A Preliminary Analysis Based on First Images from New Horizons' Flyby

    Directory of Open Access Journals (Sweden)

    Scholkmann F.

    2016-01-01

    Full Text Available The recent (14 th July 2015 flyby of NASA’s New Horizons spacecraft of the dwarf planet Pluto resulted in the first high-resolution images of the geological surface- features of Pluto. Since previous studies showed that the impact crater size-frequency distribution (SFD of different celestial objects of our solar system follows power-laws, the aim of the present analysis was to determine, for the first time, the power-law scaling behavior for Pluto’s crater SFD based on the first images available in mid-September 2015. The analysis was based on a high-resolution image covering parts of Pluto’s re- gions Sputnik Planum , Al-Idrisi Montes and Voyager Terra . 83 impact craters could be identified in these regions and their diameter ( D was determined. The analysis re- vealed that the crater diameter SFD shows a statistically significant power-law scaling ( α = 2.4926±0.3309 in the interval of D values ranging from 3.75±1.14 km to the largest determined D value in this data set of 37.77 km. The value obtained for the scaling coefficient α is similar to the coefficient determined for the power-law scaling of the crater SFDs from the other celestial objects in our solar system. Further analysis of Pluto’s crater SFD is warranted as soon as new images are received from the spacecraft.

  11. Study of crater formation and its characteristics due to impact of a cluster projectile on a metal surface by molecular dynamics approach

    Energy Technology Data Exchange (ETDEWEB)

    Naspoori, Srujan Kumar; Kammara, Kishore K.; Kumar, Rakesh, E-mail: rkm@iitk.ac.in

    2017-04-01

    Impingement of energetic particles/ions on material surfaces is of great interest as these impacts give rise to various interesting phenomena, such as sputtering, back-scattering, crater formation, emission of electrons and photons from material surfaces etc. Surface erosion occurring in the plasma-facing material of nuclear fusion reactors reduce their performance and this motivated the course of the current work in understanding the underlying physics of solid–particle interactions. In the present work, we have studied sputtering, crater formation and its characteristics on the surface of a plasma-facing material due to the impact of a low to high energy dust particle (a conglomerate of a few to a thousand atoms) using the molecular dynamics method. Sputtering yield, excavated atoms from the crater, crater depth, height of crater rim, radius and aspect ratio of the crater are calculated for a range of incident energies (10 eV to 10 keV), and the variation of these parameters with varying size (formed of 14, 32, 64 atoms) of dust particle at different temperatures of the target material are computed.

  12. Is the Linné impact crater morphology influenced by the rheological layering on the Moon's surface? Insights from numerical modeling

    Science.gov (United States)

    Martellato, Elena; Vivaldi, Valerio; Massironi, Matteo; Cremonese, Gabriele; Marzari, Francesco; Ninfo, Andrea; Haruyama, Junichi

    2017-07-01

    Linné is a simple crater, with a diameter of 2.23 km and a depth of 0.52 km, located in northwestern Mare Serenitatis. Recent high-resolution data acquired by the Lunar Reconnaissance Orbiter Camera revealed that the shape of this impact structure is best described by an inverted truncated-cone. We perform morphometric measurements, including slope and profile curvature, on the Digital Terrain Model of Linné, finding the possible presence of three subtle topographic steps, at the elevation of +20, -100, and -200 m relative to the target surface. The kink at -100 m might be related to the interface between two different rheological layers. Using the iSALE shock physics code, we numerically model the formation of Linné crater to derive hints on the possible impact conditions and target physical properties. In the initial setup, we adopt a basaltic projectile impacting the Moon with a speed of 18 km s-1. For the local surface, we consider either one or two layers, in order to test the influence of material properties or composite rheologies on the final crater morphology. The one-layer model shows that the largest variations in the crater shape take place when either the cohesion or the friction coefficient is varied. In particular, a cohesion of 10 kPa marks the threshold between conical- and parabolic-shaped craters. The two-layer model shows that the interface between the two layers would be exposed at the observed depth of 100 m when an intermediate value ( 200 m) for the upper fractured layer is set. We have also found that the truncated-cone morphology of Linné might originate from an incomplete collapse of the crater wall, as the breccia lens remains clustered along the crater walls, while the high-albedo deposit on the crater floor can be interpreted as a very shallow lens of fallout breccia. The modeling analysis allows us to derive important clues on the impactor size (under the assumption of a vertical impact and collision velocity equal to the mean

  13. Mapping Landslides in Lunar Impact Craters Using Chebyshev Polynomials and Dem's

    Science.gov (United States)

    Yordanov, V.; Scaioni, M.; Brunetti, M. T.; Melis, M. T.; Zinzi, A.; Giommi, P.

    2016-06-01

    Geological slope failure processes have been observed on the Moon surface for decades, nevertheless a detailed and exhaustive lunar landslide inventory has not been produced yet. For a preliminary survey, WAC images and DEM maps from LROC at 100 m/pixels have been exploited in combination with the criteria applied by Brunetti et al. (2015) to detect the landslides. These criteria are based on the visual analysis of optical images to recognize mass wasting features. In the literature, Chebyshev polynomials have been applied to interpolate crater cross-sections in order to obtain a parametric characterization useful for classification into different morphological shapes. Here a new implementation of Chebyshev polynomial approximation is proposed, taking into account some statistical testing of the results obtained during Least-squares estimation. The presence of landslides in lunar craters is then investigated by analyzing the absolute values off odd coefficients of estimated Chebyshev polynomials. A case study on the Cassini A crater has demonstrated the key-points of the proposed methodology and outlined the required future development to carry out.

  14. High-Resolution Aeromagnetic Survey over the Yucatan Peninsula - Implications for Chicxulub Impact, Secondary Craters and Regional Crustal Structures

    Science.gov (United States)

    Fucugauchi, J. U.; Lopez-Loera, H.; Rebolledo-Vieyra, M.

    2011-12-01

    followed by a low outside, which extend to the north and northwest. The regional broad anomalies crossing the peninsula and shelf are interpreted as crustal structures on the Yucatan block related to pre- and rifting deformation, which include basement uplift. The southward elongated magnetic anomaly and gravity low may correspond to a pre-impact structure. From analysis of residual anomalies, we found no clear indication of secondary craters or multiple impacts.

  15. The preservation of the Agoudal impact crater, Morocco, under a landslide: Indication of a genetic link between shatter cones and meteorite fragments

    Science.gov (United States)

    Nachit, Hassane; Abia, El Hassan; Bonadiman, Costanza; Di Martino, Mario; Vaccaro, Carmela

    2017-10-01

    Geological studies and tomographic profiles of a locality nearby the Agoudal village (Morocco) showed the presence of a single impact crater, 500-600 m diameter, largely hidden by a limestone block, 220 m long and 40 m deep. The site was interpreted as a landslide that followed the fall of a cosmic body. The Agoudal impact crater was not affected by intense erosion. The lack of an evident impact structure, as well as the sporadic distribution of impactites and their limited occurrence, can be explained by a complex geological framework and by recent tectonics. The latter is the result of the sliding of limestone block, which hides almost two-thirds of the crater's depression, and the oblique fall of the meteoroid on sloping ground. In addition, some impact breccia dikes sharply cut the host rock in the Agoudal impact structure. They do not show any genetic relationship with tectonics or hydrothermal activity, nor are they related to any karst or calcrete formations. Altogether, the overlapping of the meteorite strewn field (11 km long and 3 km wide) with the area of occurrence of shatter cones and impact breccias, together with the presence of meteorite fragments (shrapnel) ejected from the crater, the presence of shatter cones contaminated by products of iron meteorites and the presence of impact breccias that contain meteorite fragments of the same chemical composition of the Agoudal meteorite indicate that the fall of this meteorite can be responsible for the formation of the impact structure.

  16. Geology and mineralogy of the Auki Crater, Tyrrhena Terra, Mars: A possible post impact-induced hydrothermal system

    Science.gov (United States)

    Carrozzo, F. G.; Di Achille, G.; Salese, F.; Altieri, F.; Bellucci, G.

    2017-01-01

    A variety of hydrothermal environments have been documented in terrestrial impact structures. Due to both past water interactions and meteoritic bombardment on the surface of Mars, several authors have predicted various scenarios that include the formation of hydrothermal systems. Geological and mineralogical evidence of past hydrothermal activity have only recently been found on Mars. Here, we present a geological and mineralogical study of the Auki Crater using the spectral and visible imagery data acquired by the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars), CTX (Context Camera) and HiRISE (High Resolution Imaging Science Experiment) instruments on board the NASA MRO mission. The Auki Crater is a complex crater that is ∼38 km in diameter located in Tyrrhena Terra (96.8°E and 15.7°S) and shows a correlation between its mineralogy and morphology. The presence of minerals, such as smectite, silica, zeolite, serpentine, carbonate and chlorite, associated with morphological structures, such as mounds, polygonal terrains, fractures and veins, suggests that the Auki Crater may have hosted a post impact-induced hydrothermal system. Although the distribution of hydrated minerals in and around the central uplift and the stratigraphic relationships of some morphological units could also be explained by the excavation and exhumation of carbonate-rich bedrock units as a consequence of crater formation, we favor the hypothesis of impact-induced hydrothermal circulation within fractures and subsequent mineral deposition. The hydrothermal system could have been active for a relatively long period of time after the impact, thus producing a potential transient habitable environment. It must be a spectrally neutral component to emphasize the spectral features; It is an average of spectra taken in the same column of the numerator spectra to correct the residual instrument artifacts and reduce detector noise that changes from column to column; It must be taken in

  17. Nature of the Yucatan Block Basement as Derived From Study of Granitic Clasts in the Impact Breccias of Chicxulub Crater

    Science.gov (United States)

    Vera-Sanchez, P.; Rebolledo-Vieyra, M.; Perez-Cruz, L.; Urrutia-Fucugauchi, J.

    2008-05-01

    The tectonic and petrologic nature of the basement of the Yucatan Block is studied from analyses of basement clasts present in the impact suevitic breccias of Chicxulub crater. The impact breccias have been sampled as part of the drilling projects conducted in the Yucatan peninsula by Petroleos Mexicanos, the National University of Mexico and the Chicxulub Scientific Drilling Project. Samples analyzed come mainly from the Yaxcopoil-1, Tekax, and Santa Elena boreholes, and partly from Pemex boreholes. In this study we concentrate on clasts of the granites, granodiorites and quartzmonzonites in the impact breccias. We report major and trace element geochemical and petrological data, which are compared with data from the granitic and volcanic rocks from the Maya Mountains in Belize and from the Swannee terrane in Florida. Basement granitic clasts analyzed present intermediate to acidic sub-alkaline compositions. Plots of major oxides (e.g., Al2O3, Fe2O3, TiO2 and CaO) and trace elements (e.g., Th, Y, Hf, Nb and Zr) versus silica allow separation of samples into two major groups, which can be compared to units in the Maya Mountains and in Florida basement. The impact suevitic breccia samples have been affected by alteration likely related to the hydrothermal processes associated with the crater melt sheet. Cloritization, seritization and fenitization alterations are recognized, due to the long term hydrothermalism. Krogh et al. (1993) reported U-Pb dates on zircons from the suevitic breccias, which gave dates of 545 +/- 5 Ma and 418 +/- 6 Ma, which were interpreted in terms of the deep granitic metamorphic Yucatan basement. The younger date correlates with the age for the Osceola Granite and the St. Lucie metamorphic complex of the Swannee terrane in the Florida peninsula. The intrusive rocks in the Yucatan basement may be related to approx. 418 Ma ago collisional event in the Late Silurian.

  18. The Effects of Topography on Time Domain Controlled-Source Electromagnetic Data as it Applies to Impact Crater Sites

    Science.gov (United States)

    Hickey, M. S.

    2008-05-01

    Controlled-source electromagnetic geophysical methods provide a noninvasive means of characterizing subsurface structure. In order to properly model the geologic subsurface with a controlled-source time domain electromagnetic (TDEM) system in an extreme topographic environment we must first see the effects of topography on the forward model data. I run simulations using the Texas A&M University (TAMU) finite element (FEM) code in which I include true 3D topography. From these models we see the limits of how much topography we can include before our forward model can no longer give us accurate data output. The simulations are based on a model of a geologic half space with no cultural noise and focus on topography changes associated with impact crater sites, such as crater rims and central uplift. Several topographical variations of the model are run but the main constant is that there is only a small conductivity change on the range of 10-1 s/m between the host medium and the geologic body within. Asking the following questions will guide us through determining the limits of our code: What is the maximum step we can have before we see fringe effects in our data? At what location relative to the body does the topography cause the most effect? After we know the limits of the code we can develop new methods to increase the limits that will allow us to better image the subsurface using TDEM in extreme topography.

  19. Mitigating Climate Change in the Arid Lands of Namibia

    Science.gov (United States)

    Schneider, Martin B.; Sorensen, Marten

    2014-05-01

    model approach within a value chain analysis process to evaluate program effectiveness and impacts at both formative and summative levels. 7. Disseminate lessons learned, and results achieved to the international community through all recognized knowledge sharing outlets. Goal and objectives - accomplished by implementation of a variety of integrated action steps each linked to specific performance impact measures that assess short, medium, and long-term impacts (modified logic model). Impact measures to be monitored using formative and summative techniques within a value chain analysis process. Improved teaching and training practices, research outputs and incorporation of value chain approaches will be tracked to capture trend data in these areas. New means of ongoing and interactive communication to be established with local communities incl. use of modern media. Management strategies need to include: 1) reduced bush encroachment and biomass conversion into electricity; 2) managing costs of water catchments; 3) improving rangeland management efficiencies; 4) improved provisions of water to off-farm economic needs; 5) contribute to provision of energy supply; 6) restore and protect biodiversity and; 7) providing employment. IFAD (2013) Rural poverty Portal - Rural poverty in Namibia [http://www.ruralpovertyportal.org/country/home/tags/namibia#] Pamaccafrica (2013) Namibia commits to fight desertification [http://pamaccafrica.blogspot.dk/2013/06/namibia-commits-to-fight-desertification.html

  20. Moon - 'Ghost' craters formed during Mare filling.

    Science.gov (United States)

    Cruikshank, D. P.; Hartmann, W. K.; Wood, C. A.

    1973-01-01

    This paper discusses formation of 'pathological' cases of crater morphology due to interaction of craters with molten lavas. Terrestrial observations of such a process are discussed. In lunar maria, a number of small impact craters (D less than 10 km) may have been covered by thin layers of fluid lavas, or formed in molten lava. Some specific lunar examples are discussed, including unusual shallow rings resembling experimental craters deformed by isostatic filling.

  1. Gully formation in terrestrial simple craters: Meteor Crater, USA and Lonar Crater, India

    Science.gov (United States)

    Kumar, P.; Head, J. W.; Kring, D. A.

    2007-12-01

    Geomorphic features such as gullies, valley networks, and channels on Mars have been used as a proxy to understand the climate and landscape evolution of Mars. Terrestrial analogues provide significant insight as to how the various exogenic and endogenic processes might contribute to the evolution of these martian landscapes. We describe here a terrestrial example from Meteor Crater, which shows a spectacular development of gullies throughout the inner wall in response to rainwater precipitation, snow melting and groundwater discharge. As liquid water has been envisaged as one of the important agents of landscape sculpturing, Meteor Crater remains a useful landmark, where planetary geologists can learn some lessons. We also show here how the lithology and structural framework of this crater controls the gully distribution. Like many martian impact craters, it was emplaced in layered sedimentary rocks with an exceptionally well-developed centripetal drainage pattern consisting of individual alcoves, channels and fans. Some of the gullies originate from the rim crest and others from the middle crater wall, where a lithologic transition occurs. Deeply incised alcoves are well-developed on the soft sandstones of the Coconino Formation exposed on the middle crater wall, beneath overlying dolomite. In general, the gully locations are along crater wall radial fractures and faults, which are favorable locales of groundwater flow and discharge; these structural discontinuities are also the locales where the surface runoff from rain precipitation and snow melting can preferentially flow, causing degradation. Like martian craters, channels are well developed on the talus deposits and alluvial fans on the periphery of the crater floor. In addition, lake sediments on the crater floor provide significant evidence of a past pluvial climate, when groundwater seeped from springs on the crater wall. Caves exposed on the lower crater level may point to percolation of surface runoff

  2. Geologic Mapping of Impact Craters and the Mahuea Tholus Construct: A Year Three Progress Report for the Mahuea Tholus (V-49) Quadrangle, Venus

    Science.gov (United States)

    Lang, N. P.; Covley, M. T.; Beltran, J.; Rogers, K.; Thomson, B. J.

    2018-06-01

    We are reporting on our year three status of mapping the V-49 quadrangle (Mahuea Tholus). Our mapping efforts over this past year emphasized the 13 impact craters in the quadrangle as well as larger-scale mapping of the Mahuea Tholus construct.

  3. Stratigraphy, Sequence, and Crater Populations of Lunar Impact Basins from Lunar Orbiter Laser Altimeter (LOLA) Data: Implications for the Late Heavy Bombardment

    Science.gov (United States)

    Fassett, C. I.; Head, J. W.; Kadish, S. J.; Mazarico, E.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.

    2012-01-01

    New measurements of the topography of the Moon from the Lunar Orbiter Laser Altimeter (LOLA)[1] provide an excellent base-map for analyzing the large crater population (D.20 km)of the lunar surface [2, 3]. We have recently used this data to calculate crater size-frequency distributions (CSFD) for 30 lunar impact basins, which have implications for their stratigraphy and sequence. These data provide an avenue for assessing the timing of the transitions between distinct crater populations characteristic of ancient and young lunar terrains, which has been linked to the late heavy bombardment (LHB). We also use LOLA data to re-examine relative stratigraphic relationships between key lunar basins.

  4. An experimental investigation of the effect of impact generated micro-deformations in Moenkopi and Coconino Sandstone from Meteor Crater, Arizona on subsequent weathering

    Science.gov (United States)

    Verma, A.; Bourke, M. C.; Osinski, G.; Viles, H. A.; Blanco, J. D. R.

    2017-12-01

    Impact cratering is an important geological process that affects all planetary bodies in our solar system. As rock breakdown plays an important role in the evolution of landforms and sediments, it is important to assess the role of inheritance in the subsequent breakdown of impacted rocks.The shock pressure of several gigapascals generated during the impact can exceed the effective strength of target lithology by three to four orders of magnitude and is responsible for melting, vaporisation, shock metamorphism, fracturing and fragmentation of rocks. Environmental conditions and heterogeneities in rock properties exert an important control in rock breakdown. Similar to other subaerial rocks, impacted rocks are affected by a range of rock breakdown processes. In order to better understand the role of inheritance of the impact on rock breakdown, a rock breakdown experiment was conducted in a simulated environmental cabinet under conditions similar to the arid conditions found at the Meteor Crater site. We sampled Moenkopi and Coconino Sandstone from the Meteor Crater impact site in Arizona. For comparison, samples were also collected at control sites close by that have similar rock formations but did not undergo impact. Several established techniques (X-ray CT, SEM, Equotip, SfM) were used to characterise the rock samples before the environmental cabinet experiments. Our laboratory analysis (XRD, SEM, optical microscopy, X-ray CT) on impacted rock samples from Meteor Crater, show that rock porosity and permeability changes due to compaction and fracturing during impact. There were no high-pressure polymorphs of quartz or glass detected in XRD analysis. We ran the experiments on a total of 28 petrophysically characterised 5x5x5 cm sample blocks of Coconino and Moenkopi Sandstone (24 impacted rocks and 4 non-impacted). The results will be presented at the AGU Fall meeting 2017.

  5. Counting the cost of climate change in Namibia

    Energy Technology Data Exchange (ETDEWEB)

    Sahlen, Linda [Umea University (Sweden); Stage, Jesper [Goeteborg University (Sweden); Reid, Hannah; MacGregor, James

    2007-12-15

    When most of a country's wealth is in the wild, shifts in natural systems can wreak havoc with its economy. Namibia is a case in point. Its natural legacy underpins much of the national bank balance — and also leaves it highly vulnerable to the impacts of climate change. In fact, research suggests the impacts on natural resources alone could reduce the country's GDP by 1 to 6 per cent. The need to mainstream climate change into national policies and planning is clear, not least because the poor will be most affected. Employment opportunities could shrink and wages fall, with incomes for unskilled labour dropping by 24 per cent in a worst-case scenario. So along with 'climate-proofed' policies and activities, Namibia needs a strategy to deal with displaced farmers and farmworkers. But it is up to industrialised nations — the most responsible for climate change — to help Namibia and other vulnerable countries cope with the impacts and plan for a climate-constrained future.

  6. Geochemical characterization of impact glasses from the Zhamanshin crater by various modes of activation analysis. Remarks on genesis of irghizites

    International Nuclear Information System (INIS)

    Mizera, J.; Academy of Sciences of the Czech Republic, Prague; Randa, Z.; Tomandl, I.

    2012-01-01

    A large set of impact glasses from the Zhamanshin crater in Kazakhstan was analyzed by various modes of instrumental neutron activation analysis, supplemented by instrumental photon activation analysis and prompt gamma-ray activation analysis. Results of the determination of more than forty major and trace elements have shown that the analyzed set of homogeneous, tektite-like impact glasses with size of several centimeters and of various forms could be divided into two geochemically different groups. The lustrous, silica rich (acidic) glasses with high Ni content have been classified conventionally as irghizites. The dull, silica poor (basic) glasses with very low Ni content should not be confused with the large, heterogeneous impactite forms-zhamanshinites, but considered as a separate type of impact glass. Within both primary groups, further division has been suggested based on lower contents of Ni in an irghizite subgroup, and evidence of mixing of source materials for both primary groups in a part of the basic glasses. Based on the contents of Ni, Cr, Mn, Fe and Co, an ordinary chondrite impactor has been suggested with its contribution to the irghizite matter ranging between 4 and 21%. Possible source materials and impact processes leading to irghizite formation have been outlined. (author)

  7. Geology of Lofn Crater, Callisto

    Science.gov (United States)

    Greeley, Ronald; Heiner, Sarah; Klemaszewski, James E.

    2001-01-01

    Lofn crater is a 180-km-diameter impact structure in the southern cratered plains of Callisto and is among the youngest features seen on the surface. The Lofn area was imaged by the Galileo spacecraft at regional-scale resolutions (875 m/pixel), which enable the general geology to be investigated. The morphology of Lofn crater suggests that (1) it is a class of impact structure intermediate between complex craters and palimpsests or (2) it formed by the impact of a projectile which fragmented before reaching the surface, resulting in a shallow crater (even for Callisto). The asymmetric pattern of the rim and ejecta deposits suggests that the impactor entered at a low angle from the northwest. The albedo and other characteristics of the ejecta deposits from Lofn also provide insight into the properties of the icy lithosphere and subsurface configuration at the time of impact. The "target" for the Lofn impact is inferred to have included layered materials associated with the Adlinda multiring structure northwest of Loh and ejecta deposits from the Heimdall crater area to the southeast. The Lofn impact might have penetrated through these materials into a viscous substrate of ductile ice or possibly liquid water. This interpretation is consistent with models of the current interior of Callisto based on geophysical information obtained from the Galileo spacecraft.

  8. Yucatan Subsurface Stratigraphy from Geophysical Data, Well Logs and Core Analyses in the Chicxulub Impact Crater and Implications for Target Heterogeneities

    Science.gov (United States)

    Canales, I.; Fucugauchi, J. U.; Perez-Cruz, L. L.; Camargo, A. Z.; Perez-Cruz, G.

    2011-12-01

    Asymmetries in the geophysical signature of Chicxulub crater are being evaluated to investigate on effects of impact angle and trajectory and pre-existing target structural controls for final crater form. Early studies interpreted asymmetries in the gravity anomaly in the offshore sector to propose oblique either northwest- and northeast-directed trajectories. An oblique impact was correlated to the global ejecta distribution and enhanced environmental disturbance. In contrast, recent studies using marine seismic data and computer modeling have shown that crater asymmetries correlate with pre-existing undulations of the Cretaceous continental shelf, suggesting a structural control of target heterogeneities. Documentation of Yucatan subsurface stratigraphy has been limited by lack of outcrops of pre-Paleogene rocks. The extensive cover of platform carbonate rocks has not been affected by faulting or deformation and with no rivers cutting the carbonates, information comes mainly from the drilling programs and geophysical surveys. Here we revisit the subsurface stratigraphy in the crater area from the well log data and cores retrieved in the drilling projects and marine seismic reflection profiles. Other source of information being exploited comes from the impact breccias, which contain a sampling of disrupted target sequences, including crystalline basement and Mesozoic sediments. We analyze gravity and seismic data from the various exploration surveys, including multiple Pemex profiles in the platform and the Chicxulub experiments. Analyses of well log data and seismic profiles identify contacts for Lower Cretaceous, Cretaceous/Jurassic and K/Pg boundaries. Results show that the Cretaceous continental shelf was shallower on the south and southwest than on the east, with emerged areas in Quintana Roo and Belize. Mesozoic and upper Paleozoic sediments show variable thickness, possibly reflecting the crystalline basement regional structure. Paleozoic and Precambrian

  9. Land scarcity in Northern Namibia

    Science.gov (United States)

    Bloemertz, Lena; Dobler, Gregor; Graefe, Olivier; Kuhn, Nikolaus J.; Nghitevelekwa, Romie; Prudat, Brice; Weidmann, Laura

    2015-04-01

    Land access is a major topic in the Namibian population, which can also be seen in political discourses. In North-Central Namibia, the ongoing Communal Land Reform aims at improving tenure security and thereby also hopes to promote sustainable investment in land. Within this context, it is often argued that population growth is leading to an increased scarcity of land. However, this argument falls short of actual issues determining land scarcity in Namibia. In a context, where a large part of the population is still seen as depending on agricultural production, land scarcity has to be measured by different means to assess physical scarcity (population density, farm density, proportion of cultivated areas, or yield per person) as well as the perception of these different scarcities. This paper aims to discuss the different notions of land scarcity and argues that by focusing only on the physical realities of increasing pressure on land because of population growth, important other aspects are neglected. In order to scrutinize those measures, the study will further look at the distribution of different land uses, changing land use practices as connected to changing labour availability and mobility. Special attention will thereby be given to the difference between land scarcity and fertile soil scarcity and their relation to labour availability.

  10. Lunar Bouguer gravity anomalies - Imbrian age craters

    Science.gov (United States)

    Dvorak, J.; Phillips, R. J.

    1978-01-01

    The Bouguer gravity of mass anomalies associated with four Imbrian age craters, analyzed in the present paper, are found to differ considerably from the values of the mass anomalies associated with some young lunar craters. Of the Imbrian age craters, only Piccolomini exhibits a negative gravity anomaly (i.e., a low density region) which is characteristic of the young craters studied. The Bouguer gravity anomalies are zero for each of the remaining Imbrian age craters. Since, Piccolomini is younger, or at least less modified, than the other Imbrian age craters, it is suggested that the processes responsible for the post-impact modification of the Imbrian age craters may also be responsible for removing the negative mass anomalies initially associated with these features.

  11. CTBT PrepCom work in Namibia

    International Nuclear Information System (INIS)

    Hutchins, D.

    2002-01-01

    The history, location and facilities of Namibia's Tsumeb Geophysical Research Station are briefly described. The station's seismic and infrasound activities together with its IMS and CTBTO membership are mentioned. Manpower, training and budgetary constriants are noted

  12. Crater Degradation on Mercury: A Global Perspective

    Science.gov (United States)

    Kinczyk, M. J.; Byrne, P. K.; Prockter, L. M.; Susorney, H. C. M.; Chapman, C. R.; Barnouin, O. S.

    2017-12-01

    On geologic timescales, initially fresh craters are subjected to many weathering mechanisms. Whereas water and wind are, or were, effective erosive mechanisms such as on Earth and Mars, micrometeorite bombardment and modification due to subsequent impacts are the dominant processes that degrade craters and crater rays on airless bodies like the Moon and Mercury. Classifying craters based on their state of degradation can help determine the relative ages of landforms proximal to, and crosscut by, these craters. However, this method is most effective when used together with statistical analysis of crater distributions. Pre-MESSENGER degradation classification schemes lacked sufficient detail to be consistently applied to craters of various sizes and morphological types—despite evidence suggesting that the ejecta deposits of large basins persist much longer than those of smaller craters, for instance—yet broad assumptions have been made regarding the correlation of crater class to the planet's time-stratigraphic sequence. Moreover, previous efforts to categorize craters by degradation state have either been restricted to regional study sites or applied only to a subset of crater age or size. As a result, numerous interpretations of crater degradation state persist for Mercury, challenging a complete understanding of this process on the innermost planet. We report on the first global survey of crater degradation on Mercury. By modifying an established 5-class scheme, we have systematically applied a rigorous set of criteria to all craters ≥40 km in diameter on the planet. These criteria include the state and morphology of crater deposits separately (e.g., rim, floor, wall, ejecta) and degradation classes were assigned as the collection of these individual attributes. This approach yields a consistent classification of craters of different sizes. Our results provide the first comprehensive assessment of how craters of various states of degradation are distributed

  13. Electron microscope observations of impact crater debris amongst contaminating particulates on materials surfaces exposed in space in low-Earth orbit

    Science.gov (United States)

    Murr, L. E.; Rivas, J. M.; Quinones, S.; Niou, C.-S.; Advani, A. H.; Marquez, B.

    1993-01-01

    Debris particles extracted from a small sampling region on the leading edge of the Long Duration Exposure Facility (LDEF) spacecraft have been examined by analytical transmission electron microscopy and the elemental frequency observed by energy-dispersive X-ray spectrometry and compared with upper atmosphere (Earth) particle elemental frequency and the average elemental compositions of interplanetary dust particles. A much broader elemental distribution was observed for the exposed spacecraft surface debris milieu. Numerous metal microfragment analyses, particularly aluminum and stainless steel, were compared with scanning electron microscope observations-of impact crater features, and the corresponding elemental spectra on selected LDEF aluminium tray clamps and stainless steel bolts. The compositions and melt features for these impact craters and ejecta have been shown to be consistent with microcrystalline debris fragments in the case of aluminum, and these observations suggest an ever changing debris milieu on exposed surfaces for space craft and space system materials.

  14. Return to the Strangelove Ocean?: Preliminary results of carbon and oxygenisotope compositions of post-impact sediments, IODP Expedition 364 "Chicxulub Impact Crater"

    Science.gov (United States)

    Yamaguchi, K. E.; Ikehara, M.; Hayama, H.; Takiguchi, S.; Masuda, S.; Ogura, C.; Fujita, S.; Kurihara, E.; Matsumoto, T.; Oshio, S.; Ishihata, K.; Fuchizawa, Y.; Noda, H.; Sakurai, U.; Yamane, T.; Morgan, J. V.; Gulick, S. P. S.

    2017-12-01

    The Chicxulub crater in the northern Yucatan Peninsula, Mexico was formed by the asteroid impact at the Cretaceous-Paleogene boundary (66.0 Ma). In early 2016 the IODP Exp. 364 successfully drilled the materials from the topographic peak ring within the crater that was previously identified by seismological observations. A continuous core was recovered. The 112m-thick uppermost part of the continuous core (505.7-1334.7 mbsf) is post-impact sediments, including the PETM, that are mainly composed of carbonate with intercalation of siliciclastics and variable contents of organic carbon. More than 300 samples from the post-impact section were finely powdered for a variety of geochemical analysis. Here we report their carbon and oxygen isotope compositions of the carbonate fraction (mostly in the lower part of the analyzed section) and carbon and nitrogen isotope compositions of organic matter (mostly in the middle-upper part of the analyzed section). Isotope mass spectrometer Isoprime was used for the former analysis, and EA-irMS (elemental analyzer - isotope ratio mass spectrometer) was used for the latter analysis, both at CMCR, Kochi Univ. Depth profile of oxygen isotope compositions of carbonate fraction is variable and somewhat similar to those of Zachos et al. (2001; Science). Carbon isotope compositions of carbonate and organic carbon in the lower part of the analyzed section exhibit some excursions that could correspond to the hyperthemals in the early Paleogene. Their variable nitrogen isotope compositions reflect temporal changes in the style of biogeochemical cycles involving denitrification and nitrogen fixation. Coupled temporal changes in the carbon isotope compositions of organic and carbonate carbon immediately after the K-Pg boundary might support a Strangelove ocean (Kump, 1991; Geology), however high export production (Ba/Ti, nannoplankton and calcisphere blooms, high planktic foram richness, and diverse and abundant micro- and macrobenthic organisms

  15. Regulatory authority infrastructure for Namibia

    International Nuclear Information System (INIS)

    Shangula, K.

    2001-01-01

    The Republic of Namibia is participating in the International Atomic Energy Agency's Model Project for the Improvement of National Regulatory Authority Infrastructures in Member States. The paper illustrates our experience in solving problems and difficulties confronted in establishing an effective regulatory authority operating within the existing national infrastructure that should be supported by the Government. An effective regulatory authority is seen as part of the wider administrative scope of our Government through ministerial mandates given by the State from time to time, guaranteeing its independence when implementing legal provisions under statutes. Sections of the report illustrate our experience in the following areas: 1. National radiation protection policy 2. Structure of our national regulatory authority 3. Laws and regulations 4. Provisions for notification, authorization and registration 5. In-depth security measures for radiation sources and radioactive material 6. Systems for the inspection of radiation sources, radioactive materials, enforcement of legal provisions 7. Extent of the applications of radiation sources and radioactive materials in the country. The paper provides information regarding existing Government policy on radiation protection; structure and legal aspects of the national regulatory, including statutes and regulations; the extent of application and uses of radiation sources and security of radioactive materials; human resources: strengths and constraints; management practices and financing of regulatory authority; and plans for emergency recovery of orphan sources. National plans for management of disused sources, recovery of orphan sources, abnormal emergencies, communication of information to affected persons on exposure effects, and the safety training of persons using these applications are discussed. the paper provides a summary and some suggestions of the way forward for Namibia. (author)

  16. Vegetation history of central Chukotka deduced from permafrost paleoenvironmental records of the El'gygytgyn Impact Crater

    Directory of Open Access Journals (Sweden)

    A. A. Andreev

    2012-08-01

    Full Text Available Frozen sediments from three cores bored in the permafrost surrounding the El'gygytgyn Impact Crater Lake have been studied for pollen, non-pollen palynomorphs, plant macrofossils and rhizopods. The palynological study of these cores contributes to a higher resolution of time intervals presented in a poor temporal resolution in the lacustrine sediments; namely the Allerød and succeeding periods. Moreover, the permafrost records better reflect local environmental changes, allowing a more reliable reconstruction of the local paleoenvironments. The new data confirm that shrub tundra with dwarf birch, shrub alder and willow dominated the lake surroundings during the Allerød warming. Younger Dryas pollen assemblages reflect abrupt changes to grass-sedge-herb dominated environments reflecting significantly drier and cooler climate. Low shrub tundra with dwarf birch and willow dominate the lake vicinity at the onset of the Holocene. The find of larch seeds indicate its local presence around 11 000 cal yr BP and, thus a northward shift of treeline by about 100 km during the early Holocene thermal optimum. Forest tundra with larch and shrub alder stands grew in the area during the early Holocene. After ca. 3500 cal yr BP similar-to-modern plant communities became common in the lake vicinity.

  17. Blocky craters: implications about the lunar megaregolith

    International Nuclear Information System (INIS)

    Thompson, T.W.; Roberts, W.J.; Hartmann, W.K.; Shorthill, R.W.; Zisk, S.H.

    1979-01-01

    Radar, infrared, and photogeologic properties of lunar craters have been studied to determine whether there is a systematic difference in blocky craters between the maria and terrae and whether this difference may be due to a deep megaregolith of pulverized material forming the terra surface, as opposed to a layer of semi-coherent basalt flows forming the mare surface. Some 1310 craters from about 4 to 100 km diameter have been catalogued as radar and/or infrared anomalies. In addition, a study of Apollo Orbital Photography confirmed that the radar and infrared anomalies are correlated with blocky rubble around the crater. Analysis of the radar and infrared data indicated systematic terra-mare differences. Fresh terra craters smaller than 12 km were less likely to be infrared and radar anomalies than comparable mare craters: but terra and mare craters larger than 12 km had similar infrared and radar signatures. Also, there are many terra craters which are radar bright but not infrared anomalies. The authors interpretation of these data is that while the maria are rock layers (basaltic flow units) where craters eject boulder fields, the terrae are covered by relatively pulverized megaregolith at least 2 km deep, where craters eject less rocky rubble. Blocky rubble, either in the form of actual rocks or partly consolidated blocks, contributes to the radar and infrared signatures of the crater. However, aging by impacts rapidly destroys these effects, possibly through burial by secondary debris or by disintegration of the blocks themselves, especially in terra regions. (Auth.)

  18. Detection of lunar floor-fractured craters using machine learning methods

    Science.gov (United States)

    Thorey, C.

    2015-10-01

    About 200 Floor Fractured Craters (FFCs) have been identified by Schultz (1976) on the Moon, mainly around the lunar maria. These craters are a class of impact craters that are distinguished by having radi-ally and concentric floor-fractured networks and ab-normally shallow floors. In some cases, the uplift of the crater floor can be as large as 50% of the initial crater depth. These impact craters are interpreted to have undergone endogenous deformations after their formation.

  19. Heterogeneity effects in thermal borehole measurements in the Chicxulub impact crater

    Czech Academy of Sciences Publication Activity Database

    Wilhelm, H.; Popov, Y.; Burkhardt, H.; Šafanda, Jan; Čermák, Vladimír; Heidinger, P.; Korobkov, D.; Romushkevich, R.; Mayr, S.

    2005-01-01

    Roč. 2, č. 4 (2005), s. 357-363 ISSN 1742-2132 R&D Projects: GA ČR GA205/03/0997 Grant - others:Deutsche Forschungsgemeinschaft(DE) WI 687/12-1,2,3; Deutsche Forschungsgemeinschaft(DE) BU 298/16-1,2,3 Institutional research plan: CEZ:AV0Z30120515 Keywords : temperature logging * thermal conductivity * heat flow Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.860, year: 2005

  20. Internal Architecture of Meteorite Impact Crater at Bukit Bunuh, Lenggong – Perak, Malaysia Inferred from Upward Continuation of Magnetic Field Intensity Data

    Science.gov (United States)

    Muhammad, S. B.; Saad, R.; Saidin, M.; Yusoh, R.; Sabrian, T. A.; Samuel, Y. M.

    2018-04-01

    2–D upward continuation of magnetic field data acquired at Bukit Bunuh, Lenggong – Perak, Malaysia, with the objective to ascertain the impact crater and possible rebounds, has be carried out and interpreted in this study. Ground magnetic survey was conducted first as regional study in the entire area followed by a detailed study at the suspected crater region. Data from both studies were compiled, corrected and separated (regional – residual). The residual magnetic data ranged between -272 and +134.2 nT. 2–D upward continuation at various planes of observation was carried out on the gridded residual magnetic field data after coordinates were converted (from degrees to meters) to understate anomalies due to shallow features. The planes were at 250 m, 500 m and 750 m above the ground level. The continuation at 500 m revealed a low magnetic region, believed to be an impact crater, which is now filled with sediments, surrounded by a high magnetic shallow bedrock. Other high magnetic key features interpreted as rebounds (R) also remained after filtering out the ambiguous anomalies.

  1. Biomarkers and their stable isotopes in Cenozoic sediments above the Chicxulub impact crater

    Science.gov (United States)

    Grice, K.; Schaefer, B.; Coolen, M.; Greenwood, P. F.; Scarlett, A. G.; Freeman, K.; Lyons, S. L.

    2017-12-01

    The most widely accepted hypothesis for the cause of the End-Cretaceous mass extinction (K/Pg event) 66 Ma ago is the impact of an extra-terrestrial body, which produced the 200 km wide Chicxulub impact structure. This event led to an extinction of 75% of all species on Earth. The massive extinction in the terrestrial realm is partly attributed to the intense heat pulse, the widespread wild fires caused by the impact and the ensuing darkness, as dust and sulfate aerosols blocked out the sun leading to photosynthesis shut off and productivity collapse in both the terrestrial and marine realms. The marine realm may additionally have experienced ocean acidification resulting in mass extinction of plankton (foraminifera and coccolithophorids) and marine reptiles. Samples from the Cenozoic marine sediments including the Paleocene-Eocene Thermal Maximum (PETM) have been extracted for hydrocarbons and analysed to investigate the molecular and isotopic organic record of biotic and environmental change after the K/Pg boundary event. Specific biomarker-precursor relationship has been established by the direct correlation of sedimentary biomarkers with the biochemicals (e.g. lipids) of extant biological systems. The structural characterisation of biomarkers as well as their stable isotopic compositions (C, H and N) are used to evaluate the source(s) of organic matter (OM) and to reconstruct paleoenvironmental depositional conditions. Throughout the Cenozoic sediments (including the PETM) the biomarker distribution suggests a variation in the source of organic matter from terrestrial to marine. Furthermore, the presence of sulfurised biomarkers indicates euxinic environmental conditions at the time of deposition. Biomarker distributions indicative of green sulfur bacteria reveal persistent photic zone euxinic conditions at several intervals in the Cenozoic. Further compound specific isotope analyses will provide insights into the long-term biogeochemical cycling of C, H and S

  2. Determinants of fertility in Namibia | Indongo | African Journal of ...

    African Journals Online (AJOL)

    In-depth studies on fertility in Namibia have been lacking so far. This examines the fertility trends in Namibia over the past 2 decades and examines fertility differentials across the various sub-groups of Namibia population, and factors affecting such differentials using NDHS data. Estimates of the amount of variance in the ...

  3. Access to Archives at the National Archives of Namibia ...

    African Journals Online (AJOL)

    This article is based on findings of a study of the National Archives of Namibia conducted in 2015. The study investigated the terms and conditions that guide access at the National Archives of Namibia. The study also investigated how the National Archives of Namibia has conformed to the ICA Code of Ethics and The ...

  4. Crater Mound Formation by Wind Erosion on Mars

    Science.gov (United States)

    Steele, L. J.; Kite, E. S.; Michaels, T. I.

    2018-01-01

    Most of Mars' ancient sedimentary rocks by volume are in wind-eroded sedimentary mounds within impact craters and canyons, but the connections between mound form and wind erosion are unclear. We perform mesoscale simulations of different crater and mound morphologies to understand the formation of sedimentary mounds. As crater depth increases, slope winds produce increased erosion near the base of the crater wall, forming mounds. Peak erosion rates occur when the crater depth is ˜2 km. Mound evolution depends on the size of the host crater. In smaller craters mounds preferentially erode at the top, becoming more squat, while in larger craters mounds become steeper sided. This agrees with observations where smaller craters tend to have proportionally shorter mounds and larger craters have mounds encircled by moats. If a large-scale sedimentary layer blankets a crater, then as the layer recedes across the crater it will erode more toward the edges of the crater, resulting in a crescent-shaped moat. When a 160 km diameter mound-hosting crater is subject to a prevailing wind, the surface wind stress is stronger on the leeward side than on the windward side. This results in the center of the mound appearing to "march upwind" over time and forming a "bat-wing" shape, as is observed for Mount Sharp in Gale crater.

  5. Vulnerability and Inequality in an Increasingly Wetter World: A Namibia Case Study

    Science.gov (United States)

    Kelly, M.; Silva, J.; Mandl, D.; Sohlberg, R. A.

    2016-12-01

    Over the past two decades, Namibia has experienced increased instances of flooding that have grown in intensity and duration. Major flooding events in 2008 and 2009 displaced hundreds of thousands of people, causing thousands to remain in flood relocation camps for months at a time. Due to lack of topographic relief in the region, water tends to sit until it evaporates. Both inter-annual variability and changes in climate may lead to even greater rainfall and flooding in the future. In 2009, 29% of Namibians lived below the national poverty line (World Bank) and many make their living off of subsistence farming, as well as trading livestock. Using socio-economic data collected from the Namibia Household Income & Expenditure Survey (NHIES) reports by the Namibia Statistics Agency for the years 1993-1994, 2003-2004, and 2009-2010, and Landsat imagery for the corresponding years, we aim to characterize flood impact and flood vulnerability. Water coverage maps of Namibia were created for each time period using Landsat imagery overlain with socio-economic data to see how flooding impacts socio-variables such as income, inequality, access to livestock and grazing lands, and consumption over time. Because Namibia is not a data-rich environment, it is difficult to obtain the fine granularity of socio-data needed to put a dollar value on loss and vulnerability in flood prone areas. We hope the findings of this study will draw attention to these problems and allow us to access the data needed to more accurately characterize flood vulnerability in Namibia.

  6. Logistics in Namibia: Issues and challenges

    Directory of Open Access Journals (Sweden)

    Christopher J. Savage

    2013-08-01

    Full Text Available Logistics is perceived to be important for Namibia’s growth and development, but this may be a matter of conjecture as there is a dearth of documented information about the industry in Namibia. Furthermore, it is uncertain what the understanding of logistics is for key stakeholders in the country. This article reports on a project; the objectives were to address some of these issues and to lay the foundation for a more thorough investigation in the future. The findings of the initial project were disseminated in 2012 by: a conference paper showing the challenges and opportunities facing logistics in Namibia in 2012; a report; and through a Logistics and Transport Workshop held in Walvis Bay, Namibia in September 2012. These reports, additional interviews and subsequent discussions highlighted some potential opportunities and problems. This article summarises the project to date, showing the methodology and findings as updated by subsequent feedback and further interviews. The findings from key stakeholders of the logistics industry in Namibia include: universal agreement on the importance of logistics to Namibia; the variety in the understanding of the term logistics; the strength of the continuing influence of South Africa as the dominant economic power in southern Africa; and contrasting views on the main factors limiting logistics development, including infrastructure, attitude, government, customs, training, railways, corruption and driver shortage.

  7. Scientific Objectives of Small Carry-on Impactor (SCI) and Deployable Camera 3 Digital (DCAM3-D): Observation of an Ejecta Curtain and a Crater Formed on the Surface of Ryugu by an Artificial High-Velocity Impact

    Science.gov (United States)

    Arakawa, M.; Wada, K.; Saiki, T.; Kadono, T.; Takagi, Y.; Shirai, K.; Okamoto, C.; Yano, H.; Hayakawa, M.; Nakazawa, S.; Hirata, N.; Kobayashi, M.; Michel, P.; Jutzi, M.; Imamura, H.; Ogawa, K.; Sakatani, N.; Iijima, Y.; Honda, R.; Ishibashi, K.; Hayakawa, H.; Sawada, H.

    2017-07-01

    The Small Carry-on Impactor (SCI) equipped on Hayabusa2 was developed to produce an artificial impact crater on the primitive Near-Earth Asteroid (NEA) 162173 Ryugu (Ryugu) in order to explore the asteroid subsurface material unaffected by space weathering and thermal alteration by solar radiation. An exposed fresh surface by the impactor and/or the ejecta deposit excavated from the crater will be observed by remote sensing instruments, and a subsurface fresh sample of the asteroid will be collected there. The SCI impact experiment will be observed by a Deployable CAMera 3-D (DCAM3-D) at a distance of ˜1 km from the impact point, and the time evolution of the ejecta curtain will be observed by this camera to confirm the impact point on the asteroid surface. As a result of the observation of the ejecta curtain by DCAM3-D and the crater morphology by onboard cameras, the subsurface structure and the physical properties of the constituting materials will be derived from crater scaling laws. Moreover, the SCI experiment on Ryugu gives us a precious opportunity to clarify effects of microgravity on the cratering process and to validate numerical simulations and models of the cratering process.

  8. Martian Low-Aspect-Ratio Layered Ejecta (LARLE) craters: Distribution, characteristics, and relationship to pedestal craters

    Science.gov (United States)

    Barlow, Nadine G.; Boyce, Joseph M.; Cornwall, Carin

    2014-09-01

    Low-Aspect-Ratio Layered Ejecta (LARLE) craters are a unique landform found on Mars. LARLE craters are characterized by a crater and normal layered ejecta pattern surrounded by an extensive but thin outer deposit which terminates in a sinuous, almost flame-like morphology. We have conducted a survey to identify all LARLE craters ⩾1-km-diameter within the ±75° latitude zone and to determine their morphologic and morphometric characteristics. The survey reveals 140 LARLE craters, with the majority (91%) located poleward of 40°S and 35°N and all occurring within thick mantles of fine-grained deposits which are likely ice-rich. LARLE craters range in diameter from the cut-off limit of 1 km up to 12.2 km, with 83% being smaller than 5 km. The radius of the outer LARLE deposit displays a linear trend with the crater radius and is greatest at higher polar latitudes. The LARLE deposit ranges in length between 2.56 and 14.81 crater radii in average extent, with maximum length extending up to 21.4 crater radii. The LARLE layer is very sinuous, with lobateness values ranging between 1.45 and 4.35. LARLE craters display a number of characteristics in common with pedestal craters and we propose that pedestal craters are eroded versions of LARLE craters. The distribution and characteristics of the LARLE craters lead us to propose that impact excavation into ice-rich fine-grained deposits produces a dusty base surge cloud (like those produced by explosion craters) that deposits dust and ice particles to create the LARLE layers. Salts emplaced by upward migration of water through the LARLE deposit produce a surficial duricrust layer which protects the deposit from immediate removal by eolian processes.

  9. A high-precision 40Ar/39Ar age for the Nördlinger Ries impact crater, Germany, and implications for the accurate dating of terrestrial impact events

    Science.gov (United States)

    Schmieder, Martin; Kennedy, Trudi; Jourdan, Fred; Buchner, Elmar; Reimold, Wolf Uwe

    2018-01-01

    40Ar/39Ar dating of specimens of moldavite, the formation of which is linked to the Ries impact in southern Germany, with a latest-generation ARGUS VI multi-collector mass spectrometer yielded three fully concordant plateau ages with a weighted mean age of 14.808 ± 0.021 Ma (± 0.038 Ma including all external uncertainties; 2σ; MSWD = 0.40, P = 0.67). This new best-estimate age for the Nördlinger Ries is in general agreement with previous 40Ar/39Ar results for moldavites, but constitutes a significantly improved precision with respect to the formation age of the distal Ries-produced tektites. Separates of impact glass from proximal Ries ejecta (suevite glass from three different surface outcrops) and partially melted feldspar particles from impact melt rock of the SUBO 18 Enkingen drill core failed to produce meaningful ages. These glasses show evidence for excess 40Ar introduction, which may have been incurred during interaction with hydrothermal fluids. Only partially reset 40Ar/39Ar ages could be determined for the feldspathic melt separates from the Enkingen core. The new 40Ar/39Ar results for the Ries impact structure constrain the duration of crater cooling, during the prevailing hydrothermal activity, to locally at least ∼60 kyr. With respect to the dating of terrestrial impact events, this paper briefly discusses a number of potential issues and effects that may be the cause for seemingly precise, but on a kyr-scale inaccurate, impact ages.

  10. GRAIL Gravity Observations of the Transition from Complex Crater to Peak-Ring Basin on the Moon: Implications for Crustal Structure and Impact Basin Formation

    Science.gov (United States)

    Baker, David M. H.; Head, James W.; Phillips, Roger J.; Neumann, Gregory A.; Bierson, Carver J.; Smith, David E.; Zuber, Maria T.

    2017-01-01

    High-resolution gravity data from the Gravity Recovery and Interior Laboratory (GRAIL) mission provide the opportunity to analyze the detailed gravity and crustal structure of impact features in the morphological transition from complex craters to peak-ring basins on the Moon. We calculate average radial profiles for free-air anomalies and Bouguer anomalies for peak-ring basins, proto-basins, and the largest complex craters. Complex craters and proto-basins have free-air anomalies that are positively correlated with surface topography, unlike the prominent lunar mascons (positive free-air anomalies in areas of low elevation) associated with large basins. The Bouguer gravity anomaly profiles of complex craters are highly irregular, with central positive anomalies that are generally absent or not clearly tied to interior morphology. In contrast, gravity profiles for peak-ring basins (approx. 200 km to 580 km) are much more regular and are highly correlated with surface morphology. A central positive Bouguer anomaly is confined within the peak ring and a negative Bouguer anomaly annulus extends from the edge of the positive anomaly outward to about the rim crest. A number of degraded basins lacking interior peak rings have diameters and gravity patterns similar to those of well-preserved peak-ring basins. If these structures represent degraded peak-ring basins, the number of peak-ring basins on the Moon would increase by more than a factor of two to 34. The gravity anomalies within basins are interpreted to be due to uplift of the mantle confined within the peak ring and an annulus of thickened crust between the peak ring and rim crest. We hypothesize that mantle uplift is influenced by interaction between the transient cavity and the mantle. Further, mascon formation is generally disconnected from the number of basin rings formed and occurs over a wide range of basin sizes. These observations have important implications for models of basin and mascon formation on the

  11. GRAIL gravity observations of the transition from complex crater to peak-ring basin on the Moon: Implications for crustal structure and impact basin formation

    Science.gov (United States)

    Baker, David M. H.; Head, James W.; Phillips, Roger J.; Neumann, Gregory A.; Bierson, Carver J.; Smith, David E.; Zuber, Maria T.

    2017-08-01

    High-resolution gravity data from the Gravity Recovery and Interior Laboratory (GRAIL) mission provide the opportunity to analyze the detailed gravity and crustal structure of impact features in the morphological transition from complex craters to peak-ring basins on the Moon. We calculate average radial profiles of free-air anomalies and Bouguer anomalies for peak-ring basins, protobasins, and the largest complex craters. Complex craters and protobasins have free-air anomalies that are positively correlated with surface topography, unlike the prominent lunar mascons (positive free-air anomalies in areas of low elevation) associated with large basins. The Bouguer gravity anomaly profiles of complex craters are highly irregular, with central positive anomalies that are generally absent or not clearly tied to interior morphology. In contrast, gravity profiles for peak-ring basins (∼200 km to 580 km) are much more regular and are highly correlated with surface morphology. A central positive Bouguer anomaly is confined within the peak ring and a negative Bouguer anomaly annulus extends from the edge of the positive anomaly outward to about the rim crest. A number of degraded basins lacking interior peak rings have diameters and gravity patterns similar to those of well-preserved peak-ring basins. If these structures represent degraded peak-ring basins, the number of peak-ring basins on the Moon would increase by more than a factor of two to 34. The gravity anomalies within basins are interpreted to be due to uplift of the mantle confined within the peak ring and an annulus of thickened crust between the peak ring and rim crest. We hypothesize that mantle uplift is influenced by interaction between the transient cavity and the mantle. Further, mascon formation is generally disconnected from the number of basin rings formed and occurs over a wide range of basin sizes. These observations have important implications for models of basin and mascon formation on the Moon

  12. Drainage systems of Lonar Crater, India: Contributions to Lonar Lake hydrology and crater degradation

    Science.gov (United States)

    Komatsu, Goro; Senthil Kumar, P.; Goto, Kazuhisa; Sekine, Yasuhito; Giri, Chaitanya; Matsui, Takafumi

    2014-05-01

    Lonar, a 1.8-km-diameter impact crater in India, is a rare example of terrestrial impact craters formed in basaltic bedrock. The estimated age of the crater ranges widely from less than 12 ka to over 600 ka, but the crater preserves a relatively pristine morphology. We conducted a study of various drainage systems of Lonar Crater. The crater floor hosts a shallow 5-m-deep lake, which fluctuates seasonally. Our investigation reveals that the lake level is influenced by surface runoff that is active during the monsoon and groundwater input effective during both the rainy and the dry seasons. The groundwater discharge is observed as springs on the inner rim walls corresponding to weathered vesicular basalt and/or proximal ejecta, which are underlain by thick massive basalt layers. This observation indicates that groundwater movement is lithologically controlled: it passes preferentially through permeable vesicular basalt or proximal ejecta but is hindered in less permeable massive basalt. It is hypothesized that groundwater is also structurally controlled by dipping of basalt layers, interconnectivity of the permeable lithologic units through fractures, and preferential pathways such as fractures within the permeable lithologic units. Investigation on hydrological processes at Lonar Crater and its lake could provide useful insights into purported paleo-crater lakes presumably formed in the basaltic crust of Mars. The Lonar Crater interior shows signs of degradation in the forms of gullies and debris flows, and the Dhar valley incising in the rim leading to form a fan delta. The ejecta surface is characterized by the presence of channels, originating from the rim area and extending radially away from the crater center. The channels probably resulted from surface runoff, and its erosion contributes to the removal of the ejecta. Lonar Crater is a valuable analog site for studying degradation processes with potential application to impact craters occurring on

  13. Promotion and Development of Tourism in Namibia

    OpenAIRE

    Yömaa, Manga

    2014-01-01

    This Bachelor’s thesis will review the current state of tourism in Namibia, what needs to be done to improve it and how promotional activities can, at the same time, help develop tourism. There is no doubt that the country has enormous potential to attract tourist but to achieve this requires a strategy that includes significant government and private investment. This paper will also consider what type of tourism could be attracting visitors to Namibia and whether the focus should be on Safar...

  14. The Global Contribution of Secondary Craters on the Icy Satellites

    Science.gov (United States)

    Hoogenboom, T.; Johnson, K. E.; Schenk, P.

    2014-12-01

    At present, surface ages of bodies in the Outer Solar System are determined only from crater size-frequency distributions (a method dependent on an understanding of the projectile populations responsible for impact craters in these planetary systems). To derive accurate ages using impact craters, the impactor population must be understood. Impact craters in the Outer Solar System can be primary, secondary or sesquinary. The contribution of secondary craters to the overall population has recently become a "topic of interest." Our objective is to better understand the contribution of dispersed secondary craters to the small crater populations, and ultimately that of small comets to the projectile flux on icy satellites in general. We measure the diameters of obvious secondary craters (determined by e.g. irregular crater shape, small size, clustering) formed by all primary craters on Ganymede for which we have sufficiently high resolution data to map secondary craters. Primary craters mapped range from approximately 40 km to 210 km. Image resolution ranges from 45 to 440 m/pixel. Bright terrain on Ganymede is our primary focus. These resurfaced terrains have relatively low crater densities and serve as a basis for characterizing secondary populations as a function of primary size on an icy body for the first time. Although focusing on Ganymede, we also investigate secondary crater size, frequency, distribution, and formation, as well as secondary crater chain formation on icy satellites throughout the Saturnian and Jovian systems principally Rhea. We compare our results to similar studies of secondary cratering on the Moon and Mercury. Using Galileo and Voyager data, we have identified approximately 3,400 secondary craters on Ganymede. In some cases, we measured crater density as a function of distance from a primary crater. Because of the limitations of the Galileo data, it is necessary to extrapolate from small data sets to the global population of secondary craters

  15. Evidence for rapid topographic evolution and crater degradation on Mercury from simple crater morphometry

    Science.gov (United States)

    Fassett, Caleb I.; Crowley, Malinda C.; Leight, Clarissa; Dyar, M. Darby; Minton, David A.; Hirabayashi, Masatoshi; Thomson, Bradley J.; Watters, Wesley A.

    2017-06-01

    Examining the topography of impact craters and their evolution with time is useful for assessing how fast planetary surfaces evolve. Here, new measurements of depth/diameter (d/D) ratios for 204 craters of 2.5 to 5 km in diameter superposed on Mercury's smooth plains are reported. The median d/D is 0.13, much lower than expected for newly formed simple craters ( 0.21). In comparison, lunar craters that postdate the maria are much less modified, and the median crater in the same size range has a d/D ratio that is nearly indistinguishable from the fresh value. This difference in crater degradation is remarkable given that Mercury's smooth plains and the lunar maria likely have ages that are comparable, if not identical. Applying a topographic diffusion model, these results imply that crater degradation is faster by a factor of approximately two on Mercury than on the Moon, suggesting more rapid landform evolution on Mercury at all scales.Plain Language SummaryMercury and the Moon are both airless bodies that have experienced numerous impact events over billions of years. These impacts form craters in a geologic instant. The question examined in this manuscript is how fast these craters erode after their formation. To simplify the problem, we examined craters of a particular size (2.5 to 5 km in diameter) on a particular geologic terrain type (volcanic smooth plains) on both the Moon and Mercury. We then measured the topography of hundreds of craters on both bodies that met these criteria. Our results suggest that craters on Mercury become shallower much more quickly than craters on the Moon. We estimate that Mercury's topography erodes at a rate at least a factor of two faster than the Moon's.

  16. Polygons and Craters

    Science.gov (United States)

    2005-01-01

    3 September 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows polygons enhanced by subliming seasonal frost in the martian south polar region. Polygons similar to these occur in frozen ground at high latitudes on Earth, suggesting that perhaps their presence on Mars is also a sign that there is or once was ice in the shallow subsurface. The circular features are degraded meteor impact craters. Location near: 72.2oS, 310.3oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  17. A Tale of 3 Craters

    Science.gov (United States)

    2004-01-01

    11 November 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image captures some of the complexity of the martian upper crust. Mars does not simply have an impact-cratered surface, it's upper crust is a cratered volume. Over time, older craters on Mars have been eroded, filled, buried, and in some cases exhumed and re-exposed at the martian surface. The crust of Mars is layered to depths of 10 or more kilometers, and mixed in with the layered bedrock are a variety of ancient craters with diameters ranging from a few tens of meters (a few tens of yards) to several hundred kilometers (more than one or two hundred miles). The picture shown here captures some of the essence of the layered, cratered volume of the upper crust of Mars in a very simple form. The image shows three distinct circular features. The smallest, in the lower right quarter of the image, is a meteor crater surrounded by a mound of material. This small crater formed within a layer of bedrock that once covered the entire scene, but today is found only in this small remnant adjacent to the crater. The intermediate-sized crater, west (left) of the small one, formed either in the next layer down--that is, below the layer in which the small crater formed--or it formed in some layers that are now removed, but was big enough to penetrate deeply into the rock that is near the surface today. The largest circular feature in the image, in the upper right quarter of the image, is still largely buried. It formed in layers of rock that are below the present surface. Erosion has brought traces of its rim back to the surface of Mars. This picture is located near 50.0oS, 77.8oW, and covers an area approximately 3 km (1.9 mi) across. Sunlight illuminates this October 2004 image from the upper left.

  18. In search of conservation impact. A comment on Schusser 2012: Who determines biodiversity? An analysis of actors' power and interests in community forestry in Namibia

    DEFF Research Database (Denmark)

    Bluwstein, Jevgeniy; Lund, Jens Friis; Balooni, Kulbhushan

    2014-01-01

    The paper 'Who determines biodiversity?' concludes that community forestry contributes to improvement of biodiversity and that this outcome is shaped by certain powerful actors. We do not find that these conclusions are adequately supported by the evidence presented and argue that the study appro...... approach overlooks key principles of impact evaluation studies....

  19. What Really Happened to Earth's Older Craters?

    Science.gov (United States)

    Bottke, William; Mazrouei, Sara; Ghent, Rebecca; Parker, Alex

    2017-10-01

    Most assume the Earth’s crater record is heavily biased, with erosion/tectonics destroying older craters. This matches expectations, but is it actually true? To test this idea, we compared Earth’s crater record, where nearly all D ≥ 20 km craters are pick out from older craters with eroded fragments. Moreover, an inverse relationship between rock abundance (RA) and crater age exists. Using measured RA values, we computed ages for 111 rocky craters with D ≥ 10 km that formed between 80°N and 80°S over the last 1 Gyr.We found several surprising results. First, the production rate of D ≥ 10 km lunar craters increased by a factor of 2.2 [-0.9, +4.4; 95% confidence limits] over the past 250 Myr compared to the previous 750 Myr. Thus, the NEO population is higher now than it has been for the last billion years. Second, the size and age distributions of lunar and terrestrial craters for D ≥ 20 km over the last 650 Myr have similar shapes. This implies that crater erasure must be limited on stable terrestrial terrains; in an average sense, for a given region, the Earth either keeps all or loses all of its D ≥ 20 craters at the same rate, independent of size. It also implies the observed deficit of large terrestrial craters between 250-650 Myr is not preservation bias but rather reflects a distinctly lower impact flux. We predict 355 ± 86 D ≥ 20 km craters formed on Earth over the last 650 Myr. Only 38 ± 6 are known, so the ratio, 10.7 ± 3.1%, is a measure of the Earth’s surface that is reasonably stable to large crater formation over 650 Myr. If erosion had dominated, the age distribution of terrestrial craters would be strongly skewed toward younger ages, which is not observed. We predict Chicxulub-type impacts were rare over the last Gyr, with the event 66 Ma a probable byproduct of the current high terrestrial impact flux.

  20. Field Trip - Conservation of Carnivores in Namibia

    Science.gov (United States)

    Gibson, Amanda

    2017-04-01

    Field trips are a key component of our curriculum at ISWB. Classroom teaching is invaluable but field trips provide pupils with a tangible connection to pertinent issues of conservation. ISWB realises the importance of out of the classroom learning in field trips and to this end our students have an opportunity to partake in a number of 3-5 day field trips per academic year. In 2016, several Year 8, 9, 10, 11 and 12 students visited the AfriCat Foundation on Okonjima in central Namibia for 4 days to learn about the conservation of the predator population in Namibia. The trips were very successful and another trip this year to AfriCat North close to Etosha National Park, where the students will work closely with the local farming communities, is planned. AfriCat provides Environmental Education programmes for the youth of Namibia giving them a greater understanding of the importance of wildlife conservation. Their main objective is promoting predator and environmental awareness amongst the youth of Namibia. AfriCat Environmental Education Programme is based on 1997 UNESCO-UNEP Environmental Education objectives. "Attitudes: To raise concern about problems, values, personal responsibility and willingness to participate/act. In the end, we conserve only what we love. We will love only what we understand. We will understand only what we are taught."

  1. Regolith thickness at the Chang'E-3 landing site from the Lunar Penetrating Radar and impact craters

    Science.gov (United States)

    Fa, W.; Zhu, M.-H.; Liu, T.

    2015-10-01

    The Chang'E-3 lunar penetrating radar (LPR) observations reveal a newly formed regolith layer (<1 m), an ejecta layer (~2-6 m), and a palaeoregolith layer (~4-9 m) from the surface to a depth of ~ 20 m. The thicknesses of the newly formed regolith layer and the palaeoregolith layer are consistent with the estimations based on the excavation depth and morphology of small fresh craters.

  2. The impact of external donor support through the U.S. President's Emergency Plan for AIDS Relief on the cost of red cell concentrate in Namibia, 2004-2011.

    Science.gov (United States)

    Pitman, John P; Bocking, Adele; Wilkinson, Robert; Postma, Maarten J; Basavaraju, Sridhar V; von Finckenstein, Bjorn; Mataranyika, Mary; Marfin, Anthony A; Lowrance, David W; Sibinga, Cees Th Smit

    2015-04-01

    External assistance can rapidly strengthen health programmes in developing countries, but such funding can also create sustainability challenges. From 2004-2011, the U.S. President's Emergency Plan for AIDS Relief (PEPFAR) provided more than $ 8 million to the Blood Transfusion Service of Namibia (NAMBTS) for supplies, equipment, and staff salaries. This analysis describes the impact that support had on actual production costs and the unit prices charged for red cell concentrate (RCC) units issued to public sector hospitals. A costing system developed by NAMBTS to set public sector RCC unit prices was used to describe production costs and unit prices during the period of PEPFAR scale-up (2004-2009) and the 2 years in which PEPFAR support began to decline (2010-2011). Hypothetical production costs were estimated to illustrate differences had PEPFAR support not been available. Between 2004-2006, NAMBTS sold 22,575 RCC units to public sector facilities. During this time, RCC unit prices exceeded per unit cost-recovery targets by between 40.3% (US$ 16.75 or N$ 109.86) and 168.3% (US$ 48.72 or N$ 333.28) per year. However, revenue surpluses dwindled between 2007 and 2011, the final year of the study period, when NAMBTS sold 20,382 RCC units to public facilities but lost US$23.31 (N$ 170.43) on each unit. PEPFAR support allowed NAMBTS to leverage domestic cost-recovery revenue to rapidly increase blood collections and the distribution of RCC. However, external support kept production costs lower than they would have been without PEPFAR. If PEPFAR funds had not been available, RCC prices would have needed to increase by 20% per year to have met annual cost-recovery targets and funded the same level of investments as were made with PEPFAR support. Tracking the subsidising influence of external support can help blood services make strategic investments and plan for unit price increases as external funds are withdrawn.

  3. Coping with new regulations - Republic of Namibia

    International Nuclear Information System (INIS)

    Nujoma, J.N.

    2001-01-01

    In this paper we shall delineate the current regulatory set-up in Namibia, i.e. legal framework, administrative arrangements for the management of uranium exploration, mining, milling and waste management. Uranium, mining plays a big role on the economy of Namibia. With changing policy worldwide on supply of materials and its assurance, with consequences of worldwide on supply of materials and its assurance and with consequences of the concepts of sustainable development which coupled environmental and economic consideration, industry, people, communities, and governments will realign their future perception and concepts. Environmental considerations in Namibia require that for any major development, such as uranium exploration, environmental safety analysis reports are made which should incorporate community, industrial and government regulatory concerns. Namibia, being a developing country, knows that any new regulations that will consider environmental safety and regard for safe management of uranium wastes will add more pressure on present human resource needs (regulatory enhancement) and financial burden to the existing limited infrastructure. The new regulations should address; the environmental effect on mill tailings which are a result of processing the uranium ore in a mill; heap leaching residues which result from treatment of ore; tailing impoundment; tailing pile and tailing stabilization chemically or physically. From the radiation protection concepts, consideration will be made of the relationship of the new regulations and the current practice of the (ALI) recommended by the ICRP 60 of 1990 released in 1991, vis a vis SS-115 of IAEA for uranium intakes, considering the absence of either Nal or Germanium detector or scintillation/whole body counter in Namibia; implementation of the new regulations will require material and human resources if viable advise and training on regulatory implementation of statutory promulgation are to be enforced. (author)

  4. University students and HIV in Namibia: an HIV prevalence survey and a knowledge and attitude survey.

    Science.gov (United States)

    de Beer, Ingrid H; Gelderblom, Huub C; Schellekens, Onno; Gaeb, Esegiel; van Rooy, Gert; McNally, Alta; Wit, Ferdinand W; Tobias, Rinke de Wit F

    2012-02-22

    With an overall adult HIV prevalence of 15.3%, Namibia is facing one of the largest HIV epidemics in Africa. Young people aged 20 to 34 years constitute one of the groups at highest risk of HIV infection in Namibia. However, little is known about the impact of HIV on this group and its access to healthcare. The purpose of this study was to estimate HIV prevalence, to assess the knowledge of and attitudes towards HIV/AIDS, and to assess access to healthcare among university students in Namibia. We assessed HIV/AIDS knowledge and attitudes, HIV prevalence and access to healthcare among students at the Polytechnic of Namibia and the University of Namibia. HIV prevalence was tested through anonymous oral fluid-based tests. Half (n = 2790/5568) of the university students and 45% (n = 2807/6302) of the Polytechnic students participated in the knowledge and attitudes surveys. HIV/AIDS knowledge was reasonable, except for misperceptions about transmission. Awareness of one's own HIV status and risks was low. In all, 55% (n = 3055/5568) of university students and 58% (n = 3680/6302) of Polytechnic students participated in the HIV prevalence survey; 54 (1.8%) university students and 103 (2.8%) Polytechnic students tested HIV positive. Campus clinics were not the major providers of healthcare to the students. Meaningful strategies addressing the gap between knowledge, attitude and young people's perception of risk of HIV acquisition should be implemented. HIV prevalence among Namibian university students appears relatively low. Voluntary counselling and testing should be stimulated. Efforts should be made to increase access to healthcare through the campus clinics.

  5. Crater ejecta scaling laws: fundamental forms based on dimensional analysis

    International Nuclear Information System (INIS)

    Housen, K.R.; Schmidt, R.M.; Holsapple, K.A.

    1983-01-01

    A model of crater ejecta is constructed using dimensional analysis and a recently developed theory of energy and momentum coupling in cratering events. General relations are derived that provide a rationale for scaling laboratory measurements of ejecta to larger events. Specific expressions are presented for ejection velocities and ejecta blanket profiles in two limiting regimes of crater formation: the so-called gravity and strength regimes. In the gravity regime, ejectra velocities at geometrically similar launch points within craters vary as the square root of the product of crater radius and gravity. This relation implies geometric similarity of ejecta blankets. That is, the thickness of an ejecta blanket as a function of distance from the crater center is the same for all sizes of craters if the thickness and range are expressed in terms of crater radii. In the strength regime, ejecta velocities are independent of crater size. Consequently, ejecta blankets are not geometrically similar in this regime. For points away from the crater rim the expressions for ejecta velocities and thickness take the form of power laws. The exponents in these power laws are functions of an exponent, α, that appears in crater radius scaling relations. Thus experimental studies of the dependence of crater radius on impact conditions determine scaling relations for ejecta. Predicted ejection velocities and ejecta-blanket profiles, based on measured values of α, are compared to existing measurements of velocities and debris profiles

  6. Asteroid families from cratering: Detection and models

    Science.gov (United States)

    Milani, A.; Cellino, A.; Knežević, Z.; Novaković, B.; Spoto, F.; Paolicchi, P.

    2014-07-01

    A new asteroid families classification, more efficient in the inclusion of smaller family members, shows how relevant the cratering impacts are on large asteroids. These do not disrupt the target, but just form families with the ejecta from large craters. Of the 12 largest asteroids, 8 have cratering families: number (2), (4), (5), (10), (87), (15), (3), and (31). At least another 7 cratering families can be identified. Of the cratering families identified so far, 7 have >1000 members. This imposes a remarkable change from the focus on fragmentation families of previous classifications. Such a large dataset of asteroids believed to be crater ejecta opens a new challenge: to model the crater and family forming event(s) generating them. The first problem is to identify which cratering families, found by the similarity of proper elements, can be formed at once, with a single collision. We have identified as a likely outcome of multiple collisions the families of (4), (10), (15), and (20). Of the ejecta generated by cratering, only a fraction reaches the escape velocity from the surviving parent body. The distribution of velocities at infinity, giving to the resulting family an initial position and shape in the proper elements space, is highly asymmetric with respect to the parent body. This shape is deformed by the Yarkovsky effect and by the interaction with resonances. All the largest asteroids have been subjected to large cratering events, thus the lack of a family needs to be interpreted. The most interesting case is (1) Ceres, which is not the parent body of the nearby family of (93). Two possible interpretations of the low family forming efficiency are based on either the composition of Ceres with a significant fraction of ice, protected by a thin crust, or with the larger escape velocity of ~500 m/s.

  7. Geoscience communication in Namibia: YES Network Namibia spreading the message to young scientists

    Science.gov (United States)

    Mhopjeni, Kombada

    2015-04-01

    The Young Earth Scientists (YES) Network is an international association for early-career geoscientists under the age of 35 years that was formed as a result of the International Year of Planet Earth (IYPE) in 2007. YES Network aims to establish an interdisciplinary global network of early-career geoscientists to solve societal issues/challenges using geosciences, promote scientific research and interdisciplinary networking, and support professional development of early-career geoscientists. The Network has several National Chapters including one in Namibia. YES Network Namibia (YNN) was formed in 2009, at the closing ceremony of IYPE in Portugal and YNN was consolidated in 2013 with the current set-up. YNN supports the activities and goals of the main YES Network at national level providing a platform for young Namibian scientists with a passion to network, information on geoscience opportunities and promoting earth sciences. Currently most of the members are geoscientists from the Geological Survey of Namibia (GSN) and University of Namibia. In 2015, YNN plans to carry out two workshops on career guidance, establish a mentorship program involving alumni and experienced industry experts, and increase involvement in outreach activities, mainly targeting high school pupils. Network members will participate in a range of educational activities such as school career and science fairs communicating geoscience to the general public, learners and students. The community outreach programmes are carried out to increase awareness of the role geosciences play in society. In addition, YNN will continue to promote interactive collaboration between the University of Namibia, Geological Survey of Namibia (GSN) and Geological Society of Namibia. Despite the numerous potential opportunities YNN offers young scientists in Namibia and its presence on all major social media platforms, the Network faces several challenges. One notable challenge the Network faces is indifference among

  8. Polygons near Lyot Crater

    Science.gov (United States)

    2003-01-01

    MGS MOC Release No. MOC2-564, 4 December 2003This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows patterned ground, arranged in the form of polygons, on the undulating plains associated with ejecta from the Lyot impact crater on the martian northern plains. This picture was acquired in October 2003 and shows that the polygon margins are ridges with large boulders--shown here as dark dots--on them. On Earth, polygon patterns like this are created in arctic and antarctic regions where there is ice in the ground. The seasonal and longer-term cycles of freezing and thawing of the ice-rich ground cause these features to form over time. Whether the same is true for Mars is unknown. The polygons are located near 54.6oN, 326.6oW. The image covers an area 3 km (1.9 mi) wide and is illuminated from the lower left.

  9. Remote Sensing of Mars: Detection of Impact Craters on the Mars Global Surveyor DTM by Integrating Edge- and Region-Based Algorithms

    Science.gov (United States)

    Athanassas, C. D.; Vaiopoulos, A.; Kolokoussis, P.; Argialas, D.

    2018-03-01

    This study integrates two different computer vision approaches, namely the circular Hough transform (CHT) and the determinant of Hessian (DoH), to detect automatically the largest number possible of craters of any size on the digital terrain model (DTM) generated by the Mars Global Surveyor mission. Specifically, application of the standard version of CHT to the DTM captured a great number of craters with diameter smaller than 50 km only, failing to capture larger craters. On the other hand, DoH was successful in detecting craters that were undetected by CHT, but its performance was deterred by the irregularity of the topographic surface encompassed: strongly undulated and inclined (trended) topographies hindered crater detection. When run on a de-trended DTM (and keeping the topology unaltered) DoH scored higher. Current results, although not optimal, encourage combined use of CHT and DoH for routine crater detection undertakings.

  10. Engaging the private sector in public health challenges in Namibia

    NARCIS (Netherlands)

    de Beer, I.H.

    2017-01-01

    Engaging the private sector in healthcare is a central theme in the work of PharmAccess Foundation, a Dutch not-for-profit organization, based in Amsterdam, with offices in several African countries, including Namibia. This thesis describes interventions developed and applied in Namibia to engage

  11. Reflecting User-Created Persona in Indigenous Namibia

    DEFF Research Database (Denmark)

    Gonzalez-Cabrero, Daniel; Koch Kapuire, Gereon; Winschiers-Theophilus, Heike

    2015-01-01

    This paper presents the initial experiences and reflective accounts on the arrival of a European research colleague who recently joined our team of researchers working with Indigenous communities in Namibia. He aims to explore how communities across Namibia take on, understand and create persona...

  12. SMALL CRATERS AND THEIR DIAGNOSTIC POTENTIAL

    Directory of Open Access Journals (Sweden)

    R. Bugiolacchi

    2017-07-01

    Full Text Available I analysed and compared the size-frequency distributions of craters in the Apollo 17 landing region, comprising of six mare terrains with varying morphologies and cratering characteristics, along with three other regions allegedly affected by the same secondary event (Tycho secondary surge. I propose that for the smaller crater sizes (in this work 9–30 m, a] an exponential curve of power −0.18D can approximate Nkm−2 crater densities in a regime of equilibrium, while b] a power function D−3 closely describes the factorised representation of craters by size (1 m. The saturation level within the Central Area suggests that c] either the modelled rates of crater erosion on the Moon should be revised, or that the Tycho event occurred much earlier in time than the current estimate. We propose that d] the size-frequency distribution of small secondary craters may bear the signature (in terms of size-frequency distribution of debris/surge of the source impact and that this observation should be tested further.

  13. Investigations of Ceres's Craters with Straightened Rim

    Science.gov (United States)

    Frigeri, A.; De Sanctis, M. C.; Ammannito, E.; Raponi, A.; Formisano, M.; Ciarniello, M.; Magni, G.; Combe, J. P.; Marchi, S.; Raymond, C. A.; Schwartz, S. J.

    2017-12-01

    Dwarf planet Ceres hosts some geological features that are unique in the solar system because its composition, rich in aqueously-altered silicates, is usually found on full-size planets, whereas its mean radius is smaller than most natural satellites in the solar system. For example, the local high-albedo, carbonate-rich areas or faculaeare specific to Ceres; also, the absence of big impact crater structures is key to understand the overall mechanical behaviour of the Cerean crust. After the first findings of water ice occurring in the shadowed areas of craters on Ceres by the NASA/Dawn mission (1, 2), we analyzed the morphology of craters looking for features similar to the ones where the water ice composition has been detected analyzing the data from the VIR spectrometer (3). These craters fall outside of the family of polygonal craters which are mainly related to regional or global scale tectonics (4). We analyzed the morphology on the base of the global mosaic, the digital terrain model derived by using the stereo photogrammetry method and the single data frames of the Framing Camera. Our investigation started from crater Juling, which is characterized by a portion of the rim which forms a straight segment instead of a portion of a circle. This linear crater wall is also steep enough that it forms a cliff that is in the shadowed area in all images acquired by Dawn. Very smooth and bright deposits lay at the foot of this crater-wall cliff. Then, we identified several other craters, relatively fresh, with radius of 2 to 10 kilometers, showing one or two sectors of the crater-rim being truncated by a mass-wasting process, probably a rockfall. Our first analysis show that in the selected craters, the truncated sectors are always in the north-eastern sector of the rim for the craters in the southern hemisphere. Conversely, the craters on the northern hemisphere exhibit a truncated rim in their south-eastern sector. Although a more detailed analysis is mandatory

  14. Morphological Indicators of a Mascon Beneath Ceres's Largest Crater, Kerwan

    Science.gov (United States)

    Bland, M. T.; Ermakov, A. I.; Raymond, C. A.; Williams, D. A.; Bowling, T. J.; Preusker, F.; Park, R. S.; Marchi, S.; Castillo-Rogez, J. C.; Fu, R. R.; Russell, C. T.

    2018-02-01

    Gravity data of Ceres returned by the National Aeronautics and Space Administration's Dawn spacecraft is consistent with a lower density crust of variable thickness overlying a higher density mantle. Crustal thickness variations can affect the long-term, postimpact modification of impact craters on Ceres. Here we show that the unusual morphology of the 280 km diameter crater Kerwan may result from viscous relaxation in an outer layer that thins substantially beneath the crater floor. We propose that such a structure is consistent with either impact-induced uplift of the high-density mantle beneath the crater or from volatile loss during the impact event. In either case, the subsurface structure inferred from the crater morphology is superisostatic, and the mass excess would result in a positive Bouguer anomaly beneath the crater, consistent with the highest-degree gravity data from Dawn. Ceres joins the Moon, Mars, and Mercury in having basin-associated gravity anomalies, although their origin may differ substantially.

  15. The role of impact cratering in planetary environmental change and implications for the search for life in the solar system (Invited)

    Science.gov (United States)

    Osinski, G. R.

    2013-12-01

    Beginning in the late 18th century with the work of James Hutton, uniformitarianism emerged as a central tenet of the natural sciences and remained so well into the 20th century. Central to the idea of uniformitarianism is the concept of gradualism whereby processes throughout time occur at the same, or similar rates. In the 20th century, the idea that asteroids and comets have struck, and continue to strike, planetary bodies throughout geological time, has revolutionized our understanding of Solar System history and evolution. Indeed, it is now widely recognized that impact cratering is one of the most important and fundamental geological process in the Solar System. It is also now apparent that impact events have profoundly affected the origin and evolution of Earth, its environment, and the habitability of our planet. The extreme physical conditions (e.g., 10's of thousands of K and 100's of GPa), the concentrated nature of the energy release at a single point on a planetary surface, and the virtually instantaneous nature of the impact process sets apart impact events from all other geological processes. It should not be surprising then that such a rapid geological process can cause rapid environmental change. The destructive geological, environmental, and biological effects of meteorite impact events are well studied and well known. This is largely due to the discovery of the ~180 km diameter Chicxulub impact structure, Mexico, and its link to the mass extinction event that marks the end of the Cretaceous Period 65 Myr. ago. While the main driver for this mass extinction event remains debated, a long list of possible causes of environmental change have been proposed, including: heat from the impact explosion, tsunamis, earthquakes, global forest fires, dust injection in the upper atmosphere, production of vast quantities of N2O, and release of CO2 and sulfur species from the target rocks. Any one of these effects could potentially cause the annihilation of a

  16. Nuclear oncology in a developing country: Namibia

    International Nuclear Information System (INIS)

    Wenzel, K.S. von; Rubow, S.M.; Ellmann, A.

    2004-01-01

    Full text: Namibia is a country with 1.8 million inhabitants of whom the majority have limited access to world-class medical facilities. On an average, 25% people in Namibia get cancer in their lifetime. Most cancers can be cured if detected early and treated more effectively when metastatic disease is localized or even excluded. Nuclear medicine techniques play an important role in the detection, staging and management of malignant disease. In Namibia, due to sun exposure, skin cancer (31%) tops the list of prevailing cancers. The next most common cancer is breast cancer (9%), followed by head and neck cancers (8%), prostate (7%), Kaposi sarcoma (7%) and cervical cancer (6%). AIDS is an ever growing problem in Namibia, and related cancers e.g. Kaposi sarcoma and lymphoma are on the rise. A Nuclear Medicine Department was established at Windhoek Central Hospital in 1982. A nuclear physician, two nuclear medicine radiographers and a nursing sister staff the department. Equipment includes a Siemens Orbiter and an Elscint Apex SPX Helix gamma camera. Radiopharmaceuticals are obtained from suppliers in South Africa. There is a good working relationship between the Nuclear Medicine department and the clinicians, including the oncologists and surgeons. Therefore oncology patients are regularly referred for Nuclear Medicine procedures. Approximately 50% of all studies performed in the department are referred from oncologists. Investigations performed for breast cancer patients include scintimammography, sentinel node mapping with gamma probe. Bone scans and liver scans are used for the detection of metastases in patients with breast carcinoma and other cancers. In thyroid cancer patients, whole body radioiodine scans are done post-thyroidectomy to confirm the presence of a thyroid remnant and to detect local or distant metastases. Thallium and Sestamibi scans are performed to localize metastatic disease in thyroid cancer patients with a rising thyroglobulin level but a

  17. The changing climate and human vulnerability in north-central Namibia

    Directory of Open Access Journals (Sweden)

    Margaret N. Angula

    2016-01-01

    Full Text Available North-central Namibia is more vulnerable to effects of climate change and variability. Combined effects of environmental degradation, social vulnerability to poverty and a changing climate will compromise subsistence farming in north-central Namibia (NCN. This will make subsistence and small-scale farmers in the region more vulnerable to projected changes in the climate system. Thus, the aim of this article was to examine factors contributing to subsistence farmers’ vulnerability to impacts of climate change. The article further discusses different aspects of human vulnerability and existing adaptation strategies in response to impacts of climate related disasters experienced over the past three to four decades in NCN. Qualitative and quantitative research approaches and methodology were employed to obtain information from subsistence farmers in north-central Namibia. The sociodemographic characteristics of Ohangwena, Oshana and Omusati Region reveals high levels of unemployment, high adult and elderly population and high dependency on agricultural livelihood system. These indicators help understand levels of household vulnerability. The study concludes that households interviewed revealed low levels of adaptive capacity due to exposure to climate risks and combined effects of social, political and cultural factors. This article provided an understanding that is required to inform the adaptation pathways relevant for NCN.

  18. Cratering record in the inner solar system: Implications for earth

    International Nuclear Information System (INIS)

    Barlow, N.G.

    1988-01-01

    Internal and external processes have reworked the Earth's surface throughout its history. In particular, the effect of meteorite impacts on the early history of the earth is lost due to fluvial, aeolian, volcanic and plate tectonic action. The cratering record on other inner solar system bodies often provides the only clue to the relative cratering rates and intensities that the earth has experienced throughout its history. Of the five major bodies within the inner solar system, Mercury, Mars, and the Moon retain scars of an early episode of high impact rates. The heavily cratered regions on Mercury, Mars, and the Moon show crater size-frequency distribution curves similar in shape and crater density, whereas the lightly cratered plains on the Moon and Mars show distribution curves which, although similar to each other, are statistically different in shape and density from the more heavily cratered units. The similarities among crater size-frequency distribution curves for the Moon, Mercury, and Mars suggest that the entire inner solar system was subjected to the two populations of impacting objects but Earth and Venus have lost their record of heavy bombardment impactors. Thus, based on the cratering record on the Moon, Mercury, and Mars, it can be inferred that the Earth experienced a period of high crater rates and basin formation prior to about 3.8 BY ago. Recent studies have linked mass extinctions to large terrestrial impacts, so life forms were unable to establish themselves until impact rates decreased substantially and terrestrial conditions became more benign. The possible periodicity of mass extinctions has led to the theory of fluctuating impact rates due to comet showers in the post heavy bombardment period. The active erosional environment on the Earth complicates attempts to verify these showers by erasing geological evidence of older impact craters

  19. Crater in Utopia

    Science.gov (United States)

    2004-01-01

    23 March 2004 Craters of the martian northern plains tend to be somewhat shallow because material has filled them in. Their ejecta blankets, too, are often covered by younger materials. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example--a crater in Utopia Planitia near 43.7oN, 227.3oW. Erosion has roughened some of the surfaces of the material that filled the crater and covered its ejecta deposit. The picture covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

  20. Experimental investigation of crater growth dynamics

    Science.gov (United States)

    Schmidt, R. M.; Housen, K. R.; Bjorkman, M. D.; Holsapple, K. A.

    1985-01-01

    This work is a continuation of an ongoing program whose objective is to perform experiments and to develop scaling relationships for large-body impacts onto planetary surfaces. The centrifuge technique is used to provide experimental data for actual target materials of interest. With both power and gas guns mounted on the rotor arm, it is possible to match various dimensionless similarity parameters, which have been shown to govern the behavior of large-scale impacts. The development of the centrifuge technique has been poineered by the present investigators and is documented by numerous publications, the most recent of which are listed below. Understanding the dependence of crater size upon gravity has been shown to be key to the complete determination of the dynamic and kinematic behavior of crater formation as well as ejecta phenomena. Three unique time regimes in the formation of an impact crater have been identified.

  1. Magnetostratigraphy of the impact breccias and post-impact carbonates from borehole Yaxcopoil-1, Chicxulub impact crater, Yucatán, Mexico

    Science.gov (United States)

    Rebolledo-Vieyra, Mario; Urrutia-Fucugauchi, Jaime

    2004-06-01

    We report the magnetostratigraphy of the sedimentary sequence between the impact breccias and the post-impact carbonate sequence conducted on samples recovered by Yaxcopoil-1 (Yax-1). Samples of impact breccias show reverse polarities that span up to ~56 cm into the postimpact carbonate lithologies. We correlate these breccias to those of PEMEX boreholes Yucatán-6 and Chicxulub-1, from which we tied our magnetostratigraphy to the radiometric age from a melt sample from the Yucatán-6 borehole. Thin section analyses of the carbonate samples showed a significant amount of dark minerals and glass shards that we identified as the magnetic carriers; therefore, we propose that the mechanism of magnetic acquisition within the carbonate rocks for the interval studied is detrital remanent magnetism (DRM). With these samples, we constructed the scale of geomagnetic polarities where we find two polarities within the sequence, a reverse polarity event within the impact breccias and the base of the post-impact carbonate sequence (up to 794.07 m), and a normal polarity event in the last ~20 cm of the interval studied. The polarities recorded in the sequence analyzed are interpreted to span from chron 29r to 29n, and we propose that the reverse polarity event lies within the 29r chron. The magnetostratigraphy of the sequence studied shows that the horizon at 794.11 m deep, interpreted as the K/T boundary, lies within the geomagnetic chron 29r, which contains the K/T boundary.

  2. A schematic model of crater modification by gravity

    Science.gov (United States)

    Melosh, H. J.

    1982-01-01

    The morphology of craters found on planets and moons of the solar system is examined and a development model which can account for the observed crater characteristics is discussed. The prompt collapse of craters to form flat floors, terraced walls, and central peak structures is considered to be the result of an approximate Bingham plastic rheology of the material surrounding the crater. This rheology is induced dynamically by the strong incoherent acoustic 'noise' accompanying excavation of the crater. Central pits, peak rings, and other multiple symmetric-profile rings originate by oscillation of this fluid. Large craters with transient depths comparable to the lithosphere thickness are subject to collapse by fragmentation of the lithosphere as well as fluidization. The considered concepts are developed mathematically. A model emerges which appears capable of explaining most of the qualitative features of large impact structures.

  3. Cratering Equations for Zinc Orthotitanate Coated Aluminum

    Science.gov (United States)

    Hyde, James; Christiansen, Eric; Liou, Jer-Chyi; Ryan, Shannon

    2009-01-01

    The final STS-125 servicing mission (SM4) to the Hubble Space Telescope (HST) in May of 2009 saw the return of the 2nd Wide Field Planetary Camera (WFPC2) aboard the shuttle Discovery. This hardware had been in service on HST since it was installed during the SM1 mission in December of 1993 yielding one of the longest low Earth orbit exposure times (15.4 years) of any returned space hardware. The WFPC2 is equipped with a 0.8 x 2.2 m radiator for thermal control of the camera electronics (Figure 1). The space facing surface of the 4.1 mm thick aluminum radiator is coated with Z93 zinc orthotitanate thermal control paint with a nominal thickness of 0.1 0.2 mm. Post flight inspections of the radiator panel revealed hundreds of micrometeoroid/orbital debris (MMOD) impact craters ranging in size from less than 300 to nearly 1000 microns in diameter. The Z93 paint exhibited large spall areas around the larger impact sites (Figure 2) and the craters observed in the 6061-T651 aluminum had a different shape than those observed in uncoated aluminum. Typical hypervelocity impact craters in aluminum have raised lips around the impact site. The craters in the HST radiator panel had suppressed crater lips, and in some cases multiple craters were present instead of a single individual crater. Humes and Kinard observed similar behavior after the WFPC1 post flight inspection and assumed the Z93 coating was acting like a bumper in a Whipple shield. Similar paint behavior (spall) was also observed by Bland2 during post flight inspection of the International Space Station (ISS) S-Band Antenna Structural Assembly (SASA) in 2008. The SASA, with similar Z93 coated aluminum, was inspected after nearly 4 years of exposure on the ISS. The multi-crater phenomena could be a function of the density, composition, or impact obliquity angle of the impacting particle. For instance, a micrometeoroid particle consisting of loosely bound grains of material could be responsible for creating the

  4. Ready or Not: Namibia As a Potentially Successful Oil Producer

    Directory of Open Access Journals (Sweden)

    Andrzej Polus

    2015-01-01

    Full Text Available The primary objective of this paper is to assess whether Namibia is ready to become an oil producer. The geological estimates suggest that the country may possess the equivalent of as many as 11 billion barrels of crude oil. If the numbers are correct, Namibia would be sitting on the second-largest oil reserves in sub-Saharan Africa, and exploitation could start as soon as 2017. This clearly raises the question of whether Namibia is next in line to become a victim of the notorious “resource curse.” On the basis of critical discourse analysis and findings from field research, the authors have selected six dimensions of the resource curse and contextualised them within the spheres of Namibian politics and economy. While Namibia still faces a number of important challenges, our findings offer little evidence that the oil will have particularly disruptive effects.

  5. Factors affecting the performance of professional nurses in Namibia

    Directory of Open Access Journals (Sweden)

    Magdalene H. Awases

    2013-04-01

    Objectives: The aim of the present study was to identify factors affecting the performance of professional nurses in Namibia. Method: A quantitative, descriptive survey was used to collect data by means of a questionnaire. A random sample of 180 professional nurses was selected from six hospitals in three regions of Namibia. Results: Factors affecting the performance of nurses negatively were identified such as: lack of recognition of employees who are performing well, quality performance outcomes and an absence of a formal performance appraisal system and poor working conditions. Various factors contribute to both the positive and negative performance of professional nurses in Namibia. Strategies were developed for addressing the negative factors that could positively affect the performance of professional nurses in Namibia. Conclusions: This study emphasises the importance of developing strategies to promote the performance of nurses; build knowledge and expertise; develop mechanisms for improving the performance of nurses; expand leadership and management capacity; and generate information and knowledge through research.

  6. Public and Private Investment and Economic Growth in Namibia ...

    African Journals Online (AJOL)

    development strategy that started in the early 1970's, Namibia public enterprises ...... Estimating the Contribution of Urban Public Infrastructure to ... Ramirez, M. D. (1996), ―Public and Private Investment in Mexico and Chile: An Empirical Test.

  7. Floor-Fractured Craters through Machine Learning Methods

    Science.gov (United States)

    Thorey, C.

    2015-12-01

    Floor-fractured craters are impact craters that have undergone post impact deformations. They are characterized by shallow floors with a plate-like or convex appearance, wide floor moats, and radial, concentric, and polygonal floor-fractures. While the origin of these deformations has long been debated, it is now generally accepted that they are the result of the emplacement of shallow magmatic intrusions below their floor. These craters thus constitute an efficient tool to probe the importance of intrusive magmatism from the lunar surface. The most recent catalog of lunar-floor fractured craters references about 200 of them, mainly located around the lunar maria Herein, we will discuss the possibility of using machine learning algorithms to try to detect new floor-fractured craters on the Moon among the 60000 craters referenced in the most recent catalogs. In particular, we will use the gravity field provided by the Gravity Recovery and Interior Laboratory (GRAIL) mission, and the topographic dataset obtained from the Lunar Orbiter Laser Altimeter (LOLA) instrument to design a set of representative features for each crater. We will then discuss the possibility to design a binary supervised classifier, based on these features, to discriminate between the presence or absence of crater-centered intrusion below a specific crater. First predictions from different classifier in terms of their accuracy and uncertainty will be presented.

  8. Geologic map of Tooting crater, Amazonis Planitia region of Mars

    Science.gov (United States)

    Mouginis-Mark, Peter J.

    2015-01-01

    Tooting crater has a diameter of 27.2 km, and formed on virtually flat lava flows within Amazonis Planitia ~1,300 km west of the summit of Olympus Mons volcano, where there appear to have been no other major topographic features prior to the impact. The crater formed in an area ~185 x 135 km that is at an elevation between −3,870 m and −3,874 m relative to the Mars Orbiter Laser Altimeter (MOLA) Mars datum. This fortuitous situation (for example, a bland, horizontal target) allows the geometry of the crater and the thickness of the ejecta blanket to be accurately determined by subtracting the appropriate elevation of the surrounding landscape (−3,872 m) from the individual MOLA measurements across the crater. Thus, for the first time, it is possible to determine the radial decrease of ejecta thickness as a function of distance away from the rim crest. On the basis of the four discrete ejecta layers surrounding the crater cavity, Tooting crater is classified as a Multiple-Layered Ejecta (MLE) crater. By virtue of the asymmetric distribution of secondary craters and the greater thickness of ejecta to the northeast, Morris and others (2010) proposed that Tooting crater formed by an oblique impact from the southwest. The maximum range of blocks that produced identifiable secondary craters is ~500 km (~36.0 crater radii) from the northeast rim crest. In contrast, secondary craters are only identifiable ~215 km (15.8 radii) to the southeast and 225 km (16.5 radii) to the west.

  9. Integration of Electrical Resistivity and Seismic Refraction using Combine Inversion for Detecting Material Deposits of Impact Crater at Bukit Bunuh, Lenggong, Perak

    Science.gov (United States)

    Yusoh, R.; Saad, R.; Saidin, M.; Muhammad, S. B.; Anda, S. T.

    2018-04-01

    Both electrical resistivity and seismic refraction profiling has become a common method in pre-investigations for visualizing subsurface structure. The encouragement to use these methods is that combined of both methods can decrease the obscure inherent to the distinctive use of these methods. Both method have their individual software packages for data inversion, but potential to combine certain geophysical methods are restricted; however, the research algorithms that have this functionality was exists and are evaluated personally. The interpretation of subsurface were improve by combining inversion data from both method by influence each other models using closure coupling; thus, by implementing both methods to support each other which could improve the subsurface interpretation. These methods were applied on a field dataset from a pre-investigation for archeology in finding the material deposits of impact crater. There were no major changes in the inverted model by combining data inversion for this archetype which probably due to complex geology. The combine data analysis shows the deposit material start from ground surface to 20 meter depth which the class separation clearly separate the deposit material.

  10. Mercury's Densely Cratered Surface

    Science.gov (United States)

    1974-01-01

    Mariner 10 took this picture (FDS 27465) of the densely cratered surface of Mercury when the spacecraft was 18,200 kilometers (8085 miles) from the planet on March 29. The dark line across top of picture is a 'dropout' of a few TV lines of data. At lower left, a portion of a 61 kilometer (38 mile) crater shows a flow front extending across the crater floor and filling more than half of the crater. The smaller, fresh crater at center is about 25 kilometers (15 miles) in diameter. Craters as small as one kilometer (about one-half mile) across are visible in the picture.The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.Image Credit: NASA/JPL/Northwestern University

  11. Development of a Soil Organic Carbon Baseline for Otjozondjupa, Namibia

    OpenAIRE

    Nijbroek, R.; Kempen, B.; Mutua, J.; Soderstrom, M.; Piikki, K.; Hengari, S.; Andreas, A.

    2017-01-01

    Land Degradation Neutrality (LDN) has been piloted in 14 countries and will be scaled up to over 120 countries. As a LDN pilot country, Namibia developed sub-national LDN baselines in Otjozondjupa Region. In addition to the three LDN indicators (soil organic carbon, land productivity and land cover change), Namibia also regards bush encroachment as an important form of land degradation. We collected 219 soil profiles and used Random Forest modelling to develop the soil organic carbon stock ba...

  12. Mass movement on Vesta at steep scarps and crater rims

    Science.gov (United States)

    Krohn, K.; Jaumann, R.; Otto, K.; Hoogenboom, T.; Wagner, R.; Buczkowski, D. L.; Garry, B.; Williams, D. A.; Yingst, R. A.; Scully, J.; De Sanctis, M. C.; Kneissl, T.; Schmedemann, N.; Kersten, E.; Stephan, K.; Matz, K.-D.; Pieters, C. M.; Preusker, F.; Roatsch, T.; Schenk, P.; Russell, C. T.; Raymond, C. A.

    2014-12-01

    The Quadrangles Av-11 and Av-12 on Vesta are located at the northern rim of the giant Rheasilvia south polar impact basin. The primary geologic units in Av-11 and Av-12 include material from the Rheasilvia impact basin formation, smooth material and different types of impact crater structures (such as bimodal craters, dark and bright crater ray material and dark ejecta material). Av-11 and Av-12 exhibit almost the full range of mass wasting features observed on Vesta, such as slump blocks, spur-and-gully morphologies and landslides within craters. Processes of collapse, slope instability and seismically triggered events force material to slump down crater walls or scarps and produce landslides or rotational slump blocks. The spur-and-gully morphology that is known to form on Mars is also observed on Vesta; however, on Vesta this morphology formed under dry conditions.

  13. Mass Movement on Vesta at Steep Scarps and Crater Rims

    Science.gov (United States)

    Krohn, K.; Jaumann, R.; Otto, K.; Hoogenboom, T.; Wagner, R.; Buczkowski, D. L.; Garry, B.; Williams, D. A.; Yingst, R. A.; Scully, J.; hide

    2014-01-01

    The Quadrangles Av-11 and Av-12 on Vesta are located at the northern rim of the giant Rheasilvia south polar impact basin. The primary geologic units in Av-11 and Av-12 include material from the Rheasilvia impact basin formation, smooth material and different types of impact crater structures (such as bimodal craters, dark and bright crater ray material and dark ejecta material). Av-11 and Av-12 exhibit almost the full range of mass wasting features observed on Vesta, such as slump blocks, spur-and-gully morphologies and landslides within craters. Processes of collapse, slope instability and seismically triggered events force material to slump down crater walls or scarps and produce landslides or rotational slump blocks. The spur-and-gully morphology that is known to form on Mars is also observed on Vesta; however, on Vesta this morphology formed under dry conditions.

  14. Areva Resources Namibia. Report to Stakeholders 2014

    International Nuclear Information System (INIS)

    2015-01-01

    This document is Areva Namibia's stakeholder report for 2013-2014. The focus of this edition is on Areva Namibia's involvement in the community. The Trekkopje project went into a 'Care and Maintenance' phase from 1 July 2013. The mine is merely in a holding phase with every intention to start up as soon as the economic conditions become more favourable. Since then, the Care and Maintenance team has been protecting the assets and kept the mine's infrastructure in working condition so that it can be commissioned without delay. However, Areva is still present and actively engaged with its stakeholders at the local, regional and national level. Neighbouring communities are benefiting from social projects in Arandis, Swakopmund and the wider Erongo region. Areva is actively supporting economic development through the Erongo Development Foundation's SME micro-finance scheme and education projects. At the regional level, Areva's desalination plant has enabled NamWater to meet the water demand of Swakop Uranium's new Husab mine. Furthermore, water supply to the Roessing and Langer Heinrich mines could be sustained when pumping water from the Omaruru Delta (Omdel) aquifer at Henties Bay had to be reduced due to over-exploitation. Areva has recently started negotiations with the Government of the Republic of Namibia about the sale of the Erongo desalination plant. Areva is also involved in the mining industry as members of the Namibian Chamber of Mines and the Namibian Uranium Association (NUA). The NUA plays an important role in setting standards to ensure that local mining practices comply with global standards on sustainable development, environmental protection and radiological safety. One of Areva's major achievements in 2014 was the completion of the second phase of metallurgical test work with very promising results. The Care and Maintenance phase is the opportunity to thoroughly research the alkaline heap leach process and

  15. The uranium resources and production of Namibia

    International Nuclear Information System (INIS)

    Palfi, A.G.

    1997-01-01

    The promulgation of the Minerals (Prospecting and Mining) Act, 1992, on 1 April 1994 and the simultaneous repeal of restrictive South African legislation on reporting uranium exploration and production results, allowed the Namibian Government for the first time to present information for publication of the report ''Uranium 1995 - Resource, Production and Demand'', by the OECD Nuclear Energy Agency and the IAEA. Namibia, one of the youngest independent nations in Africa, has a large number of uranium occurrences and deposits in several geological environments. The total estimated uranium resource amounts to about 299 thousand tonnes recoverable uranium at a cost of less than US$ 130/kg U, within the known conventional resources category. The most prominent geological type of these is the unique, granite-related uranium occurrences located in the central part of the Namib Desert. Permo-Triassic age Karoo sandstone-hosted uranium deposits were subject to only limited exploration due to the down-turn of uranium prices in the latter part of 1980s, despite they very encouraging exploration results. As only limited Karoo sandstone-covered areas were tested there is still great potential for further discoveries. The planned output of Roessing Uranium Mine at 40,000 tonnes of ore per day which results in an annual production of 4536 tonnes of uranium oxide, was achieved in 1979. In case of improved uranium market conditions, Namibia is in a strong position to increase uranium production and open up new production centres to strengthen the country's position as an important uranium producer in the world. 6 figs, 2 tabs

  16. Areva Resources Namibia. Report to Stakeholders 2015

    International Nuclear Information System (INIS)

    2016-01-01

    This document is Areva Namibia's stakeholder report for 2015. After some turbulent years, the company has now settled into the routine of care and maintenance and expect it to continue until the over-supply of uranium on the world market is depleted and the market conditions improve sustainably. Until then the Care and Maintenance team will continue protecting the mine's infrastructure so that it can be commissioned without delay as soon as the economic conditions become more favourable. The company also maintains its focus on process development and optimisation, on safety, occupational health and protection of the environment. The care and maintenance phase is giving an opportunity to thoroughly research the alkaline heap leach process and make improvements to the uranium recovery methods. The third phase of metallurgical test work will explore some new options to further reduce the cost of production and enhance the economic viability of Trekkopje mine. Preliminary bench testing carried out in mid-2015 at the Process Development Laboratory in France delivered promising results. The on-site testing program started in October 2015 and will continue into 2016. Areva Namibia has been very active in the community. Thanks to the desalination plant NamWater has been able to meet the water demand of the other uranium mines when pumping from the Omaruru Delta (Omdel) aquifer had to be reduced. Negotiations about the sale of the plant are at an advanced stage. The company is supporting social projects in the areas of economic development, education, culture and sport in its neighbouring communities of Arandis and Swakopmund and in the wider Erongo region. This report presents some of the highlights of this active engagement with stakeholders at the local, regional and national level. Content: Health and Safety; People; Environment; Community; Care and Maintenance; Process Development; Sustainability Indicators

  17. Surface age of venus: use of the terrestrial cratering record

    International Nuclear Information System (INIS)

    Schaber, G.G.; Shoemaker, E.M.; Kozak, R.C.

    1987-01-01

    The average crater age of Venus' northern hemisphere may be less than 250 m.y. assuming equivalence between the recent terrestrial cratering rate and that on Venus for craters ≥ 20 km in diameter. For craters larger than this threshold size, below which crater production is significantly affected by the Venusian atmosphere, there are fairly strong observational grounds for concluding that such an equivalence in cratering rates on Venus and Earth may exist. However, given the uncertainties in the role of both active and inactive comet nuclei in the cratering history of Earth, we conclude that the age of the observed surface in the northern hemisphere of Venus could be as great as the 450-m.y. mean age of the Earth's crust. The observed surface of Venus might be even older, but no evidence from the crater observations supports an age as great as 1 b.y. If the age of the observed Venusian surface were 1 b.y., it probably should bear the impact scars of a half dozen or more large comet nuclei that penetrated the atmosphere and formed craters well over 100 km in diameter. Venera 15/16 mapped only about 25% of Venus; the remaining 75% may tell us a completely different story

  18. Namibia specific climate smart agricultural land use practices: Challenges and opportunities for enhancing ecosystem services

    Science.gov (United States)

    Kuhn, Nikolaus J.; Talamondjila Naanda, Martha; Bloemertz, Lena

    2015-04-01

    , from the initial steps of designing PES, could be one of the crucial ingredients for success. Community self-organisation and mobilisation supported by NGOs, as practiced in the Namibia's Community Based Natural Resource Management (CBNRM) offer useful lessons of how CSA-PES initiatives can be pursued. CBNRM enables farmers to make LUP decisions, impacting value attached to ecosystem services, which can be prioritised now, for what purposes, and which practices can be adopted to enhance the attainment of multiple benefits. Key words: small scale farmers, land degradation, ecosystem services, Namibia

  19. A model for the dynamics of crater-centered intrusion: Application to lunar floor-fractured craters

    Science.gov (United States)

    Thorey, Clément; Michaut, Chloé

    2014-01-01

    Lunar floor-fractured craters are a class of craters modified by post-impact mechanisms. They are defined by distinctive shallow floors that are convex or plate-like, sometimes with a wide floor moat bordering the wall region. Radial, concentric, and polygonal floor fractures suggest an endogenous process of modification. Two mechanisms have been proposed to account for such deformations: viscous relaxation and spreading of a magma intrusion at depth below the crater. To test the second assumption and bring more constraints on the intrusion process, we develop a model for the dynamics of magma spreading below an elastic overlying layer with a crater-like topography. As predicted in earlier more qualitative studies, the increase in lithostatic pressure at the crater wall zone prevents the intrusion from spreading laterally, leading to the thickening of the intrusion. Additionally, our model shows that the final crater floor appearance after the uplift, which can be convex or flat, with or without a circular moat bordering the wall zone, depends on the elastic thickness of the layer overlying the intrusion and on the crater size. Our model provides a simple formula to derive the elastic thickness of the overlying layer hence a minimum estimate for the intrusion depth. Finally, our model suggests that crust redistribution by cratering must have controlled magma ascent below most of these craters.

  20. Estimation of hydraulic permeability considering the micro morphology of rocks of the borehole YAXCOPOIL-1 (Impact crater Chicxulub, Mexico)

    Science.gov (United States)

    Mayr, S. I.; Burkhardt, H.; Popov, Yu.; Wittmann, A.

    2008-04-01

    Internal surface, formation factor, Nuclear Magnetic Resonance (NMR)-T2 relaxation times and pore radius distributions were measured on representative core samples for the estimation of hydraulic permeability. Permeability is estimated using various versions of the classic Kozeny-Carman-equation (K-C) and a further development of K-C, the fractal PaRiS-model, taking into account the internal surface. In addition to grain and pore size distribution, directly connected to permeability, internal surface reflects the internal structure (“micro morphology”). Lithologies could be grouped with respect to differences in internal surface. Most melt rich impact breccia lithologies exhibit large internal surfaces, while Tertiary post-impact sediments and Cretaceous lithologies in displaced megablocks display smaller internal surfaces. Investigations with scanning electron microscopy confirm the correlation between internal surface and micro morphology. In addition to different versions of K-C, estimations by means of NMR, pore radius distributions and some gas permeability measurements serve for cross-checking and calibration. In general, the different estimations from the independent methods and the measurements are in satisfactory accordance. For Tertiary limestones and Suevites bulk with very high porosities (up to 35%) permeabilites between 10-14 and 10-16 m2 are found, whereas in lower Suevite, Cretaceous anhydrites and dolomites, bulk permeabilites are between 10-15 and 10-23 m2.

  1. Description of Tessaracoccus profundi sp.nov., a deep-subsurface actinobacterium isolated from a Chesapeake impact crater drill core (940 m depth)

    Science.gov (United States)

    Finster, K.W.; Cockell, C.S.; Voytek, M.A.; Gronstal, A.L.; Kjeldsen, K.U.

    2009-01-01

    A novel actinobacterium, designated CB31T, was isolated from a 940 m depth sample of a drilling core obtained from the Chesapeake meteor impact crater. The strain was isolated aerobically on R2A medium agar plates supplemented with NaCl (20 g l-1) and MgCl2???6H 2O (3 g l-1). The colonies were circular, convex, smooth and orange. Cells were slightly curved, rod-shaped in young cultures and often appeared in pairs. In older cultures cells were coccoid. Cells stained Gram-positive, were non-motile and did not form endospores. The diagnostic diamino acid of the peptidoglycan was ll-diaminopimelic acid. The polar lipids included phosphatidylglycerol, diphosphatidglycerol, four different glycolipids, two further phospholipids and one unidentified lipid. The dominant menaquinone was MK-9(H4) (70%). The major cellular fatty acid was anteiso C15:0 (83%). The DNA G + C content was 68 mol%. The strain grew anaerobically by reducing nitrate to nitrite or by fermenting glucose. It was catalase positive and oxidase negative. It grew between 10 and 45??C, with an optimum between 35 and 40??C. The pH range for growth was 5.7-9.3, with an optimum at pH 7.5. The closest phylogenetic neighbors based on 16S rRNA gene sequence identity were members of the genus Tessaracoccus (95-96% identity). On the basis of phenotypic and phylogenetic distinctiveness, strain CB31T is considered to represent a novel species of the genus Tessaracoccus, for which we propose the name Tessaracoccus profundi sp. nov.. It is the first member of this genus that has been isolated from a deep subsurface environment. The type strain is CB31T (=NCIMB 14440T = DSM 21240T). ?? 2009 Springer Science+Business Media B.V.

  2. Description of Tessaracoccus profundi sp.nov., a deep-subsurface actinobacterium isolated from a Chesapeake impact crater drill core (940 m depth).

    Science.gov (United States)

    Finster, K W; Cockell, C S; Voytek, M A; Gronstal, A L; Kjeldsen, K U

    2009-11-01

    A novel actinobacterium, designated CB31(T), was isolated from a 940 m depth sample of a drilling core obtained from the Chesapeake meteor impact crater. The strain was isolated aerobically on R2A medium agar plates supplemented with NaCl (20 g l(-1)) and MgCl2 x 6 H2O (3 g l(-1)). The colonies were circular, convex, smooth and orange. Cells were slightly curved, rod-shaped in young cultures and often appeared in pairs. In older cultures cells were coccoid. Cells stained Gram-positive, were non-motile and did not form endospores. The diagnostic diamino acid of the peptidoglycan was LL: -diaminopimelic acid. The polar lipids included phosphatidylglycerol, diphosphatidglycerol, four different glycolipids, two further phospholipids and one unidentified lipid. The dominant menaquinone was MK-9(H(4)) (70%). The major cellular fatty acid was anteiso C15:0 (83%). The DNA G + C content was 68 mol%. The strain grew anaerobically by reducing nitrate to nitrite or by fermenting glucose. It was catalase positive and oxidase negative. It grew between 10 and 45 degrees C, with an optimum between 35 and 40 degrees C. The pH range for growth was 5.7-9.3, with an optimum at pH 7.5. The closest phylogenetic neighbors based on 16S rRNA gene sequence identity were members of the genus Tessaracoccus (95-96% identity). On the basis of phenotypic and phylogenetic distinctiveness, strain CB31(T) is considered to represent a novel species of the genus Tessaracoccus, for which we propose the name Tessaracoccus profundi sp. nov.. It is the first member of this genus that has been isolated from a deep subsurface environment. The type strain is CB31(T) (=NCIMB 14440(T) = DSM 21240(T)).

  3. Goat paddock cryptoexplosion crater, Western Australia

    Science.gov (United States)

    Harms, J.E.; Milton, D.J.; Ferguson, J.; Gilbert, D.J.; Harris, W.K.; Goleby, B.

    1980-01-01

    Goat Paddock, a crater slightly over 5 km in diameter (18??20??? S, 126??40???E), lies at the north edge of the King Leopold Range/Mueller Range junction in the Kimberley district, Western Australia (Fig. 1). It was noted as a geological anomaly in 1964 during regional mapping by the Bureau of Mineral Resources, Geology and Geophysics and the Geological Survey of Western Australia. The possibility of its being a meteorite impact crater has been discussed1, although this suggestion was subsequently ignored2. Two holes were drilled by a mining corporation in 1972 to test whether kimberlite underlay the structure. Here we report the findings of five days of reconnaissance in August 1979 which established that Goat Paddock is a cryptoexplosion crater containing shocked rocks and an unusually well exposed set of structural features. ?? 1980 Nature Publishing Group.

  4. Application of combined micro-proton-induced X-ray emission and micro-synchrotron radiation X-ray fluorescence techniques for the characterization of impact materials around Barringer Meteor Crater

    Energy Technology Data Exchange (ETDEWEB)

    Uzonyi, I. [Institute of Nuclear Research of the Hungarian Academy of Sciences, Department of Electrostatic Accelerators, H-4026 Debrecen, Bem ter 18/C (Hungary)]. E-mail: uzonyi@atomki.hu; Szoeor, Gy. [Department of Mineralogy and Geology, University of Debrecen, H-4010 Debrecen, Egyetem ter 1 (Hungary); Vekemans, B. [Department of Chemistry, University of Antwerpen (UIA) Universiteitsplein 1, B-2610 Wilrijk (Belgium); Vincze, L. [Department of Chemistry, University of Antwerpen (UIA) Universiteitsplein 1, B-2610 Wilrijk (Belgium); Rozsa, P. [Department of Mineralogy and Geology, University of Debrecen, H-4010 Debrecen, Egyetem ter 1 (Hungary); Szabo, Gy. [Institute of Nuclear Research of the Hungarian Academy of Sciences, Department of Electrostatic Accelerators, H-4026 Debrecen, Bem ter 18/C (Hungary); Somogyi, A. [ID22, ESRF, 6 rue Jules Horowitz, BP 220, F-38043 Grenoble Cedex (France); Adams, F. [Department of Chemistry, University of Antwerpen (UIA) Universiteitsplein 1, B-2610 Wilrijk (Belgium); Kiss, A.Z. [Institute of Nuclear Research of the Hungarian Academy of Sciences, Department of Electrostatic Accelerators, H-4026 Debrecen, Bem ter 18/C (Hungary)

    2004-10-08

    A combined micro-PIXE and micro-SRXRF method has been used for the characterization of impact materials collected at the well-known Barringer Meteor Crater. Elemental maps were recorded and concentrations were determined by micro-PIXE method for the major constituents of samples. Micro-SRXRF technique was used for the complementary measurement of medium and high atomic number elements, especially the siderophilic ones. Altogether, approximately 40 elements were analyzed. These results elucidate many steps of the formation mechanism of the various impact-metamorphosed objects.

  5. The Mining of Uranium–Cases from Namibia, Niger, Brazil, and Bulgaria

    Directory of Open Access Journals (Sweden)

    Tomislav Tkalec

    2015-12-01

    Full Text Available The text is a dossier focusing on the problems of uranium mining. The first part deals with some general issues and dilemmas associated with nuclear energy production and its environmental impacts; the second deals with case studies of uranium mining in Namibia, Niger, Brazil, and Bulgaria. The dossier is based entirely on the reports and documents of the EJOLT international project. Most of the research and studies mentioned in the article was carried out by CRIIRAD, a French organization, which participated in the EJOLT project.

  6. Creation of High Resolution Terrain Models of Barringer Meteorite Crater (Meteor Crater) Using Photogrammetry and Terrestrial Laser Scanning Methods

    Science.gov (United States)

    Brown, Richard B.; Navard, Andrew R.; Holland, Donald E.; McKellip, Rodney D.; Brannon, David P.

    2010-01-01

    Barringer Meteorite Crater or Meteor Crater, AZ, has been a site of high interest for lunar and Mars analog crater and terrain studies since the early days of the Apollo-Saturn program. It continues to be a site of exceptional interest to lunar, Mars, and other planetary crater and impact analog studies because of its relatively young age (est. 50 thousand years) and well-preserved structure. High resolution (2 meter to 1 decimeter) digital terrain models of Meteor Crater in whole or in part were created at NASA Stennis Space Center to support several lunar surface analog modeling activities using photogrammetric and ground based laser scanning techniques. The dataset created by this activity provides new and highly accurate 3D models of the inside slope of the crater as well as the downslope rock distribution of the western ejecta field. The data are presented to the science community for possible use in furthering studies of Meteor Crater and impact craters in general as well as its current near term lunar exploration use in providing a beneficial test model for lunar surface analog modeling and surface operation studies.

  7. Serodetection of Ehrlichia canis amongst dogs in central Namibia

    Directory of Open Access Journals (Sweden)

    Rutendo Manyarara

    2015-06-01

    Full Text Available Ehrlichia canis is a major pathogen in dogs throughout Africa, yet it has not been reported in Namibia. The aim of this study was to determine the seroprevalence of canine ehrlichiosis in central Namibia using the ImmunoComb assay (Biogal, Galed Laboratories. The study included 76 dogs that presented to the Rhino Park Veterinary Clinic in the north-western suburb of Khomasdal, Windhoek, Namibia, as well as 30 stray dogs from the Windhoek branch of the Society for the Prevention of Cruelty to Animals. Of the 106 dogs tested, 53.8% were seropositive at titres > 1:80. Dogs that presented with symptoms of E. canis infection had a significantly higher seroprevalence (86.6% compared with apparently healthy dogs (41.6% (P = 0.00. Location of habitation was significant (P < 0.017, with a high percentage of dogs exposed to E. canis living in the northern or north-western part of Windhoek. As the first study to serologically establish E. canis as a major pathogen in dogs in central Namibia, it is notable that the highest proportion of seropositive dogs came from low-income areas. Further investigation is necessary to describe the ecology of this important tick-borne pathogen of companion animals in Namibia.

  8. Cratering on Small Bodies: Lessons from Eros

    Science.gov (United States)

    Chapman, C. R.

    2003-01-01

    Cratering and regolith processes on small bodies happen continuously as interplanetary debris rains down on asteroids, comets, and planetary satellites. Butthey are very poorly observed and not well understood. On the one hand, we have laboratory experimentation at small scales and we have examination of large impact craters (e.g. Meteor Crater on Earth and imaging of abundant craters on terrestrial planets and outer planet moons). Understanding cratering on bodies of intermediate scales, tens of meters to hundreds of km in size, involves either extrapolation from our understanding of cratering phenomena at very different scales or reliance on very preliminary, incomplete examination of the observational data we now have for a few small bodies. I review the latter information here. It has been generally understood that the role of gravity is greatly diminished for smaller bodies, so a lot of cratering phenomena studied for larger bodies is less applicable. But it would be a mistake to imagine that laboratory experiments on gravitationless rocks (usually at 1 g) are directly applicable, except perhaps to those monolithic Near Earth Asteroids (NEAs) some tens of meters in size that spin very rapidly and can be assumed to be "large bare rocks" with "negative gravity". Whereas it had once been assumed that asteroids smaller than some tens of km diameter would retain little regolith, it is increasingly apparent that regolith and megoregolith processes extend down to bodies only hundreds of meters in size, perhaps smaller. Yet these processes are very different from those that pertain to the Moon, which is our chief prototype of regolith processes. The NEAR Shoemaker spacecraft's studies of Eros provide the best evidence to date about small-body cratering processes, as well as a warning that our theoretical understanding requires anchoring by direct observations. Eros: "Ponds", Paucity of Small Craters, and Other Mysteries. Although Eros is currently largely detached

  9. Peste equina: descrizione di focolai di malattia in Namibia

    Directory of Open Access Journals (Sweden)

    Massimo Scacchia

    2009-06-01

    Full Text Available La peste equina è una malattia virale degli equidi trasmessa da vettori. Scopo di questo lavoro è di riferire su casi di malattia verificatisi in Namibia nel corso degli anni 2006-2008, osservati dal personale dell'Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise “G. Caporale” e del Central Veterinary Laboratory di Windhoek, Namibia e confermati dagli esami di laboratorio. Il lavoro è stato possibile anche grazie alla fattiva collaborazione stabilitasi con i veterinari pubblici, privati e allevatori Namibiani.

  10. The Contribution of Wildlife to Sustainable Natural Resource Utilization in Namibia: A Review

    Directory of Open Access Journals (Sweden)

    Diana L. van Schalkwyk

    2010-11-01

    Full Text Available Namibia is the driest country in sub-Saharan Africa, but well known for its richness in species and sustainable natural resource utilization. The Namibian farming sector consists mainly of extensive farming systems. Cattle production contributes 54% of the livestock sector’s production output, followed by sheep and goats (25%, hides and skins (9%, and other forms of agricultural production (12%. Namibia’s freehold farmers have obtained ownership rights over land and livestock since the early 1900s; commercial rights over wildlife and plants were given to freehold farmers in 1967 and to communal farmers in 1996. Natural resource-based production systems then overtook agricultural production systems and exceeded it by a factor of at least two. The shift from practicing conservation to sustainable utilization of natural resources contributed to the rapid growth of wildlife utilization. The wildlife industry in Namibia is currently the only animal production system that is expanding. There are in total at least two million head of different wildlife species. The broader impact of the utilization of wildlife on the economy is estimated to be around N$ 1.3 billion. Tourism, live sales and trophy hunting, cannot sustain further growth. Wildlife farming could offer better opportunities for ensuring long-term sustainability. As the game meat trade in Namibia is not formalized, harvesting wildlife to satisfy the demand for game meat in export markets is still in its infancy. Sustainable harvesting of wildlife for meat production, however, has the potential to increase earnings to the beneficiaries in the wildlife sector.

  11. The Morphology of Craters on Mercury: Results from MESSENGER Flybys

    Science.gov (United States)

    Barnouin, Oliver S.; Zuber, Maria T.; Smith, David E.; Neumann, Gregory A.; Herrick, Robert R.; Chappelow, John E.; Murchie, Scott L.; Prockter, Louise M.

    2012-01-01

    Topographic data measured from the Mercury Laser Altimeter (MLA) and the Mercury Dual Imaging System (MDIS) aboard the MESSENGER spacecraft were used for investigations of the relationship between depth and diameter for impact craters on Mercury. Results using data from the MESSENGER flybys of the innermost planet indicate that most of the craters measured with MLA are shallower than those previously measured by using Mariner 10 images. MDIS images of these same MLA-measured craters show that they have been modified. The use of shadow measurement techniques, which were found to be accurate relative to the MLA results, indicate that both small bowl-shaped and large complex craters that are fresh possess depth-to-diameter ratios that are in good agreement with those measured from Mariner 10 images. The preliminary data also show that the depths of modified craters are shallower relative to fresh ones, and might provide quantitative estimates of crater in-filling by subsequent volcanic or impact processes. The diameter that defines the transition from simple to complex craters on Mercury based on MESSENGER data is consistent with that reported from Mariner 10 data.

  12. Distribution of hepatitis B virus infection in Namibia | Mhata | South ...

    African Journals Online (AJOL)

    Background. Namibia regards hepatitis B virus (HBV) infection as a public health problem and introduced hepatitis B vaccinations for infants during 2009. However, information on HBV infection in the country remains limited, and effective public health interventions may be compromised in the absence of adequate ...

  13. Development of a Soil Organic Carbon Baseline for Otjozondjupa, Namibia

    NARCIS (Netherlands)

    Nijbroek, R.; Kempen, B.; Mutua, J.; Soderstrom, M.; Piikki, K.; Hengari, S.; Andreas, A.

    2017-01-01

    Land Degradation Neutrality (LDN) has been piloted in 14 countries and will be scaled up to over 120 countries. As a LDN pilot country, Namibia developed sub-national LDN baselines in Otjozondjupa Region. In addition to the three LDN indicators (soil organic carbon, land productivity and land cover

  14. The Khwe of Namibia, foragers between game, tourism and politics

    NARCIS (Netherlands)

    Koot, S.P.; W. van Beek (Walter); J. Diemer (Jeroen)

    2014-01-01

    markdownabstract__Abstract__ In this paper we examine the plight of the Khwe Bushmen, a group of (former) hunter-gatherers in the Bwabwata National Park in Northern Namibia. The Khwe have lived for a long time in the area of Bwabwata, so are highly affected by the park’s conservation activities

  15. World and experiences of AIDS orphans in north central Namibia

    NARCIS (Netherlands)

    Brug, van der M.

    2007-01-01

    How do young AIDS orphans deal with the loss of their parents and their changed circumstances? This thesis discusses the social environment, experiences and perceptions of fourteen orphans in north central Namibia. The author followed the children for five months from September 2003 until March

  16. A new grass frog from Namibia | Channing | African Zoology

    African Journals Online (AJOL)

    A new species of grass frog of lhe genus Ptychadena is described from northern Namibia. Although superficially similar to Ptychadena schillukorum and Ptychadena mossambica, the new species differs In advertisement call, and external characters. An examination of a series of published sonagrams indicates that ...

  17. Revision of regional maximum flood (RMF) estimation in Namibia ...

    African Journals Online (AJOL)

    Extreme flood hydrology in Namibia for the past 30 years has largely been based on the South African Department of Water Affairs Technical Report 137 (TR 137) of 1988. This report proposes an empirically established upper limit of flood peaks for regions called the regional maximum flood (RMF), which could be ...

  18. Health care options for commercial farm workers in Namibia

    NARCIS (Netherlands)

    de Beer, I.; Coutinho, H.M.; Guariguata, L.; Fortsch, H.T.; Hough, R.; Rinke de Wit, T.F.

    2011-01-01

    Introduction: Limited access to health care in rural areas is a challenge in Namibia. In 2007 a survey was conducted among employers of commercial farms to assess the feasibility of introducing private, affordable health insurance that including HIV/AIDS coverage for commercial farm workers in

  19. Anatomy Education in Namibia: Balancing Facility Design and Curriculum Development

    Science.gov (United States)

    Wessels, Quenton; Vorster, Willie; Jacobson, Christian

    2012-01-01

    The anatomy curriculum at Namibia's first, and currently only, medical school is clinically oriented, outcome-based, and includes all of the components of modern anatomical sciences i.e., histology, embryology, neuroanatomy, gross, and clinical anatomy. The design of the facilities and the equipment incorporated into these facilities were directed…

  20. Identifying and representing elements of local contexts in Namibia

    DEFF Research Database (Denmark)

    Rodil, Kasper; Jensen, Kasper Løvborg; Rehm, Matthias

    2013-01-01

    In an attempt to represent local context in a 3D visualisa- tionfor rural elders in Namibia we have foundmajor dierences in thecon- ceptualizationof this context between external and local partners in the co-creation process. Through the evaluation of a mobile context capture tool we found a clea...

  1. Sands at Gusev Crater, Mars

    Science.gov (United States)

    Cabrol, Nathalie A.; Herkenhoff, Kenneth E.; Knoll, Andrew H.; Farmer, Jack D.; Arvidson, Raymond E.; Grin, E.A.; Li, Ron; Fenton, Lori; Cohen, B.; Bell, J.F.; Yingst, R. Aileen

    2014-01-01

    Processes, environments, and the energy associated with the transport and deposition of sand at Gusev Crater are characterized at the microscopic scale through the comparison of statistical moments for particle size and shape distributions. Bivariate and factor analyses define distinct textural groups at 51 sites along the traverse completed by the Spirit rover as it crossed the plains and went into the Columbia Hills. Fine-to-medium sand is ubiquitous in ripples and wind drifts. Most distributions show excess fine material, consistent with a predominance of wind erosion over the last 3.8 billion years. Negative skewness at West Valley is explained by the removal of fine sand during active erosion, or alternatively, by excess accumulation of coarse sand from a local source. The coarse to very coarse sand particles of ripple armors in the basaltic plains have a unique combination of size and shape. Their distribution display significant changes in their statistical moments within the ~400 m that separate the Columbia Memorial Station from Bonneville Crater. Results are consistent with aeolian and/or impact deposition, while the elongated and rounded shape of the grains forming the ripples, as well as their direction of origin, could point to Ma'adim Vallis as a possible source. For smaller particles on the traverse, our findings confirm that aeolian processes have dominated over impact and other processes to produce sands with the observed size and shape patterns across a spectrum of geologic (e.g., ripples and plains soils) and aerographic settings (e.g., wind shadows).

  2. The central uplift of Ritchey crater, Mars

    Science.gov (United States)

    Ding, Ning; Bray, Veronica J.; McEwen, Alfred S.; Mattson, Sarah S.; Okubo, Chris H.; Chojnacki, Matthew; Tornabene, Livio L.

    2015-01-01

    Ritchey crater is a ∼79 km diameter complex crater near the boundary between Hesperian ridged plains and Noachian highland terrain on Mars (28.8°S, 309.0°E) that formed after the Noachian. High Resolution Imaging Science Experiment (HiRISE) images of the central peak reveal fractured massive bedrock and megabreccia with large clasts. Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectral analysis reveals low calcium pyroxene (LCP), olivine (OL), hydrated silicates (phyllosilicates) and a possible identification of plagioclase bedrock. We mapped the Ritchey crater central uplift into ten units, with 4 main groups from oldest and originally deepest to youngest: (1) megabreccia with large clasts rich in LCP and OL, and with alteration to phyllosilicates; (2) massive bedrock with bright and dark regions rich in LCP or OL, respectively; (3) LCP and OL-rich impactites draped over the central uplift; and (4) aeolian deposits. We interpret the primitive martian crust as igneous rocks rich in LCP, OL, and probably plagioclase, as previously observed in eastern Valles Marineris. We do not observe high-calcium pyroxene (HCP) rich bedrock as seen in Argyre or western Valles Marineris. The association of phyllosilicates with deep megabreccia could be from impact-induced alteration, either as a result of the Richey impact, or alteration of pre-existing impactites from Argyre basin and other large impacts that preceded the Ritchey impact, or both.

  3. The central uplift of Ritchey crater, Mars

    Science.gov (United States)

    Ding, Ning; Bray, Veronica J.; McEwen, Alfred S.; Mattson, Sarah S.; Okubo, Chris H.; Chojnacki, Matthew; Tornabene, Livio L.

    2015-05-01

    Ritchey crater is a ∼79 km diameter complex crater near the boundary between Hesperian ridged plains and Noachian highland terrain on Mars (28.8°S, 309.0°E) that formed after the Noachian. High Resolution Imaging Science Experiment (HiRISE) images of the central peak reveal fractured massive bedrock and megabreccia with large clasts. Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectral analysis reveals low calcium pyroxene (LCP), olivine (OL), hydrated silicates (phyllosilicates) and a possible identification of plagioclase bedrock. We mapped the Ritchey crater central uplift into ten units, with 4 main groups from oldest and originally deepest to youngest: (1) megabreccia with large clasts rich in LCP and OL, and with alteration to phyllosilicates; (2) massive bedrock with bright and dark regions rich in LCP or OL, respectively; (3) LCP and OL-rich impactites draped over the central uplift; and (4) aeolian deposits. We interpret the primitive martian crust as igneous rocks rich in LCP, OL, and probably plagioclase, as previously observed in eastern Valles Marineris. We do not observe high-calcium pyroxene (HCP) rich bedrock as seen in Argyre or western Valles Marineris. The association of phyllosilicates with deep megabreccia could be from impact-induced alteration, either as a result of the Richey impact, or alteration of pre-existing impactites from Argyre basin and other large impacts that preceded the Ritchey impact, or both.

  4. High Resolution Digital Elevation Models of Pristine Explosion Craters

    Science.gov (United States)

    Farr, T. G.; Krabill, W.; Garvin, J. B.

    2004-01-01

    In order to effectively capture a realistic terrain applicable to studies of cratering processes and landing hazards on Mars, we have obtained high resolution digital elevation models of several pristine explosion craters at the Nevada Test Site. We used the Airborne Terrain Mapper (ATM), operated by NASA's Wallops Flight Facility to obtain DEMs with 1 m spacing and 10 cm vertical errors of 4 main craters and many other craters and collapse pits. The main craters that were mapped are Sedan, Scooter, Schooner, and Danny Boy. The 370 m diameter Sedan crater, located on Yucca Flat, is the largest and freshest explosion crater on Earth that was formed under conditions similar to hypervelocity impact cratering. As such, it is effectively pristine, having been formed in 1962 as a result of a controlled detonation of a 100 kiloton thermonuclear device, buried at the appropriate equivalent depth of burst required to make a simple crater. Sedan was formed in alluvium of mixed lithology and subsequently studied using a variety of field-based methods. Nearby secondary craters were also formed at the time and were also mapped by ATM. Adjacent to Sedan and also in alluvium is Scooter, about 90 m in diameter and formed by a high-explosive event. Schooner (240 m) and Danny Boy (80 m) craters were also important targets for ATM as they were excavated in hard basalt and therefore have much rougher ejecta. This will allow study of ejecta patterns in hard rock as well as engineering tests of crater and rock avoidance and rover trafficability. In addition to the high resolution DEMs, crater geometric characteristics, RMS roughness maps, and other higher-order derived data products will be generated using these data. These will provide constraints for models of landing hazards on Mars and for rover trafficability. Other planned studies will include ejecta size-frequency distribution at the resolution of the DEM and at finer resolution through air photography and field measurements

  5. Morphometry and Morphology of Fresh Craters on Titan

    Science.gov (United States)

    Kirk, R. L.; Wood, C. A.; Neish, C.; Lucas, A.; Hayes, A. G.; Cassini Radar Team

    2011-12-01

    Cassini RADAR imagery obtained on Titan flyby T77 revealed a 40-km diameter fresh impact crater at 11.6° N 44.6° W. This is only the 8th crater identified with high confidence (Wood et al., 2010, Icarus 206, 334), and the 3rd (after Sinlap D=79 km and Ksa D=30 km) for which the depth can be estimated by comparing the foreshortening of the near and far walls. This "autostereo" technique yields an estimated depth of 680 m. The T77 image forms a stereo pair with the T17 discovery image of Ksa from which we estimate the depth of Ksa at 750-800 m, in close agreement with SARTopo data. The depth of Sinlap is 760 m based on SARTopo. Depth-diameter ratios for these craters thus range from 0.01 to 0.025 and the depths are comparable to but 200-400 m shallower than fresh craters of the same size on Ganymede (Bray et al., 2008, Met. Planet Sci. 43, 1979). The depth differences could be explained by initial crater morphometry, by relaxation in a different thermal environment, or (perhaps most plausibly given the bland floors of even the freshest Titan craters) to sedimentary infill. In contrast, the 18x36 km elliptical depression at Sotra Facula is much deeper than Ganymede craters of similar size (d=1500 m from stereo), supporting the conclusion that it is not an impact crater. All three craters exhibit a relatively radar-bright annulus around the outer edge of the floor, possibly as the result of mass wasting of blocky materials from the crater walls. The central part of each crater is darker. The central darker floor of the new crater is symmetrical and featureless, whereas Ksa has a bright central ring 7 km in diameter. Stereo spot heights indicate the ring is 350±100 m above the outer floor. This height is in close agreement with the scaling for Ganymede crater central peaks from Bray et al. (2008). The darker floor area of Sinlap is substantially asymmetrical with a small bright central spot whose elevation is unknown. The new crater has continuous, radar

  6. Crater Highlands, Tanzania

    Science.gov (United States)

    2006-01-01

    The Shuttle Radar Topography Mission (SRTM), flown aboard Space Shuttle Endeavour in February 2000, acquired elevation measurements for nearly all of Earth's landmass between 60oN and 56oS latitudes. For many areas of the world SRTM data provide the first detailed three-dimensional observation of landforms at regional scales. SRTM data were used to generate this view of the Crater Highlands along the East African Rift in Tanzania. Landforms are depicted with colored height and shaded relief, using a vertical exaggeration of 2X and a southwestwardly look direction. Lake Eyasi is depicted in blue at the top of the image, and a smaller lake occurs in Ngorongoro Crater. Near the image center, elevations peak at 3648 meters (11,968 feet) at Mount Loolmalasin, which is south of Ela Naibori Crater. Kitumbeine (left) and Gelai (right) are the two broad mountains rising from the rift lowlands. Mount Longido is seen in the lower left, and the Meto Hills are in the right foreground. Tectonics, volcanism, landslides, erosion and deposition -- and their interactions -- are all very evident in this view. The East African Rift is a zone of spreading between the African (on the west) and Somali (on the east) crustal plates. Two branches of the rift intersect here in Tanzania, resulting in distinctive and prominent landforms. One branch trends nearly parallel the view and includes Lake Eyasi and the very wide Ngorongoro Crater. The other branch is well defined by the lowlands that trend left-right across the image (below center, in green). Volcanoes are often associated with spreading zones where magma, rising to fill the gaps, reaches the surface and builds cones. Craters form if a volcano explodes or collapses. Later spreading can fracture the volcanoes, which is especially evident on Kitumbeine and Gelai Mountains (left and right, respectively, lower center). The Crater Highlands rise far above the adjacent savannas, capture moisture from passing air masses, and host rain

  7. Geological mapping of lunar highland crater Lalande: Topographic configuration, morphology and cratering process

    Science.gov (United States)

    Li, Bo; Ling, Zongcheng; Zhang, Jiang; Chen, Jian; Liu, ChangQing; Bi, Xiangyu

    2018-02-01

    Highland crater Lalande (4.45°S, 8.63°W; D = 23.4 km) is located on the PKT area of the lunar near side, southeast of the Mare Insularum. It is a complex crater in Copernican era and has three distinguishing features: high silicic anomaly, the highest Th abundance and special landforms on its floor. There are some low-relief bulges on the left of Lalande's floor with regular circle or ellipse shapes. They are ∼250-680 m wide and ∼30-91 m high with maximum flank slopes >20°. There are two possible scenarios for the formation of these low-relief bulges which are impact melt products or young silicic volcanic eruptions. We estimated the absolute model ages of the ejecta deposits, several melt ponds and the hummocky floor and determined the ratio of diameter and depth of the crater Lalande. In addition, we found some similar bugle features within other Copernican-aged craters and there were no volcanic source vents on Lalande's floor. Thus, we hypothesized that these low-relief bulges were most consistent with an origin of impact melts during the crater formation instead of small and young volcanic activities occurring on the floor. Based on Kaguya Terrain Camera (TC) ortho-mosaic and Digital Terrain Model (DTM) data produced by TC imagery in stereo, geological units and some linear features on the floor and wall of Lalande have been mapped. Eight geological units are organized by crater floor units: hummocky floor, central peak and low-relief bulges; and crater wall units: terraced walls, channeled and veneered walls, interior walls, mass wasting areas, blocky areas, and melt ponds. These geological units and linear features provided us a chance to understand some details of the cratering process and elevation differences on the floor. We proposed that subsidence due to melt cooling, late-stage wall collapse and rocks uplifted from beneath the surface could be the possible causes of the observed elevation differences on Lalande's floor.

  8. Meteor Crater, AZ

    Science.gov (United States)

    2002-01-01

    The Barringer Meteorite Crater (also known as 'Meteor Crater') is a gigantic hole in the middle of the arid sandstone of the Arizona desert. A rim of smashed and jumbled boulders, some of them the size of small houses, rises 50 m above the level of the surrounding plain. The crater itself is nearly a 1500 m wide, and 180 m deep. When Europeans first discovered the crater, the plain around it was covered with chunks of meteoritic iron - over 30 tons of it, scattered over an area 12 to 15 km in diameter. Scientists now believe that the crater was created approximately 50,000 years ago. The meteorite which made it was composed almost entirely of nickel-iron, suggesting that it may have originated in the interior of a small planet. It was 50 m across, weighed roughly 300,000 tons, and was traveling at a speed of 65,000 km per hour. This ASTER 3-D perspective view was created by draping an ASTER bands 3-2-1image over a digital elevation model from the US Geological Survey National Elevation Dataset.This image was acquired on May 17, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet.ASTER is one of five Earth-observing instruments launched December 18,1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Bjorn Eng of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The Terra mission is part of NASA's Earth Science Enterprise, along

  9. Morphological indicators of a mascon beneath Ceres' largest crater, Kerwan

    Science.gov (United States)

    Bland, Michael T.; Ermakov, Anton; Raymond, Carol A.; Williams, David A.; Bowling, Tim J.; Preusker, F.; Park, Ryan S.; Marchi, Simone; Castillo-Rogez, Julie C.; Fu, R.R.; Russell, Christopher T.

    2018-01-01

    Gravity data of Ceres returned by the National Aeronautics and Space Administration's Dawn spacecraft is consistent with a lower density crust of variable thickness overlying a higher density mantle. Crustal thickness variations can affect the long‐term, postimpact modification of impact craters on Ceres. Here we show that the unusual morphology of the 280 km diameter crater Kerwan may result from viscous relaxation in an outer layer that thins substantially beneath the crater floor. We propose that such a structure is consistent with either impact‐induced uplift of the high‐density mantle beneath the crater or from volatile loss during the impact event. In either case, the subsurface structure inferred from the crater morphology is superisostatic, and the mass excess would result in a positive Bouguer anomaly beneath the crater, consistent with the highest‐degree gravity data from Dawn. Ceres joins the Moon, Mars, and Mercury in having basin‐associated gravity anomalies, although their origin may differ substantially.

  10. Geomorphology and Geology of the Southwestern Margaritifer Sinus and Argyre Regions of Mars. Part 4: Flow Ejecta Crater Distribution

    Science.gov (United States)

    Parker, T. J.; Pieri, D. C.

    1985-01-01

    Flow ejecta craters - craters surrounded by lobate ejecta blankets - are found throughout the study area. The ratio of the crater's diameter to that of the flow ejecta in this region is approximately 40 to 45%. Flow ejecta craters are dominantly sharply defined craters, with slightly degraded craters being somewhat less common. This is probably indicative of the ejecta's relatively low resistence to weathering and susceptibility to burial. Flow ejecta craters here seem to occur within a narrow range of crater sizes - the smallest being about 4km in diameter and the largest being about 27km in diameter. Ejecta blankets of craters at 4km are easily seen and those of smaller craters are simply not seen even in images with better than average resolution for the region. This may be due to the depth of excavation of small impacting bodies being insufficient to reach volatile-rich material. Flow ejecta craters above 24km are rare, and those craters above 27km do not display flow ejecta blankets. This may be a result of an excavation depth so great that the volatile content of the ejecta is insufficient to form a fluid ejecta blanket. The geomorphic/geologic unit appears also to play an important role in the formation of flow ejecta craters. Given the typical size range for the occurrence of flow ejecta craters for most units, it can be seen that the percentage of flow ejecta craters to the total number of craters within this size range varies significantly from one unit to the next. The wide variance in flow ejecta crater density over this relatively small geographical area argues strongly for a lithologic control of their distribution.

  11. Aqueous alteration detection in Tikhonravov crater, Mars

    Science.gov (United States)

    Mancarella, F.; Fonti, S.; Alemanno, G.; Orofino, V.; Blanco, A.

    2018-03-01

    The existence of a wet period lasting long enough to allow the development of elementary forms of life on Mars has always been a very interesting issue. Given this perspective, the research for geological markers of such occurrences has been continually pursued. Once a favorable site is detected, effort should be spent to get as much information as possible aimed at a precise assessment of the genesis and evolution of the areas showing the selected markers. In this work, we discuss the recent finding of possible deposits pointing to the past existence of liquid water in Tikhonravov crater located in Arabia Terra. Comparison of CRISM spectra and those of laboratory minerals formed by aqueous alteration has led us to the conclusion that the studied areas within the impact crater host phyllosilicates deposits. In addition, analysis of the CRISM spectra has resulted in the tentative identification of carbonates mixed with phyllosilicates.

  12. Temporary Employment Services (Labour Brokers in South Africa and Namibia

    Directory of Open Access Journals (Sweden)

    s van Eck

    2010-08-01

    Full Text Available South Africa currently allows labour broking although this area of commerce is problematic. The trade union movement, government and organised business are presently debating the future regulation of this industry. Namibia has experimented with, and failed, to place a legislative ban on labour broking. The Supreme Court of Appeal of Namibia considered International Labour Organisation conventions and provisions of their Constitution before concluding that labour broking should be regulated but not prohibited. In this article it is argued that South African policy makers can gain valuable insights from the Namibian experience. It is submitted that it would be appropriate for Parliament to take cognisance of international and foreign principles and to accept amendments that would provide for stricter regulation for labour broking, rather than placing an outright ban on this economic activity.

  13. The Dakar conference on Namibia and human rights

    Directory of Open Access Journals (Sweden)

    J. D. van der Vyver

    1976-03-01

    Full Text Available The international conference on "Namibia and Human Rights" that took place in Dakar, Senegal on 5 to 8 January 1976 was, to the best of my knowledge, the idea of dr Karel Vasak in his capacity as president of the International Institute of Human Rights of Strasbourg, France, who planned the conference - again to the best of my knowledge - in close collaboration with mr Seán MacBride, the United Nations Commissioner for Namibia. The Government of the Republic of Senegal acted as host for the conference, the conference was formally sponsored by mr Seán MacBride, and it was officially organized by the International Institute of Human Rights. The International Commission of Jurists and the International Association of Democratic Lawyers also lent their support to the organizers of the conference.

  14. The development of national standards for adult educators in Namibia

    Science.gov (United States)

    Ellis, Justin; Richardson, Brent H.

    2012-06-01

    Since gaining independence from South Africa in 1990, Namibia has placed considerable emphasis on education, including adult learning. As a means of improving the quality of adult learning, the Namibian Ministry of Education commissioned the development of national standards in 2010 to express competency requirements for adult educators. Particular attention was paid to the views of adult learners who participated through thirty focus groups. The participatory process revealed that the work of an adult educator is more complex and demanding than had previously been appreciated. The required competencies were categorised under four headings: (1) Knowledge as an adult educator, (2) Practice as an adult educator, (3) Relationships as an adult educator and (4) Ethics and professionalism as an adult educator. The Namibia Qualifications Authority, acting under its legislative mandate of setting occupational standards for occupations, jobs, posts and positions, approved the national standards in 2011.

  15. The development and evolution of Etosha Pan, Namibia

    OpenAIRE

    Hipondoka, Martin H.T.

    2005-01-01

    This study explores and examines the geomorphology of a large endorheic basin, approximately twice the size of Luxemburg, situated in the Etosha National Park, Namibia. The main focus is directed on how and when this depression, known as Etosha Pan, came into being. Geomorphological investigation was complemented and guided primarily by the application and interpretation of satellite-derived information. Etosha Pan has attracted scientific investigations for nearly a century. Unfortunately, t...

  16. Local Governance, Urban Poverty and Service Delivery in Namibia

    OpenAIRE

    Fjeldstad, Odd-Helge; Geisler, Gisela; Nangulah, Selma; Nygaard, Knut; Pomuti, Akiser; Shifotoka, Albertina; Van Rooy, Gert

    2005-01-01

    The urbanisation of poverty is one of the most dramatic developments on the African continent, yielding contrasting images of affluent residential and business districts and utter misery in sprawling shantytowns or slums. Namibia has one of Africa’s highest urban growth rates, taking thousands of women, men and children to towns in search of a better life. The large majority of these end up in poverty-stricken informal settlements in urban areas. The current service delivery approach of the g...

  17. Cratering Studies in Thin Plastic Films

    Science.gov (United States)

    Shu, A. J.; Bugiel, S.; Gruen, E.; Hillier, J.; Horanyi, M.; Munsat, T. L.; Srama, R.

    2013-12-01

    Thin plastic films, such as Polyvinylidene Fluoride (PVDF), have been used as protective coatings or dust detectors on a number of missions including the Dust Counter and Mass Analyzer (DUCMA) instrument on Vega 1 and 2, the High Rate Detector (HRD) on the Cassini Mission, and the Student Dust Counter (SDC) on New Horizons. These types of detectors can be used on the lunar surface or in lunar orbit to detect dust grain size distributions and velocities. Due to their low power requirements and light weight, large surface area detectors can be built for observing low dust fluxes. The SDC dust detector is made up of a permanently polarized layer of PVDF coated on both sides with a thin layer (≈ 1000 Å) of aluminum nickel. The operation principle is that a micrometeorite impact removes a portion of the metal surface layer exposing the permanently polarized PVDF underneath. This causes a local potential near the crater changing the surface charge of the metal layer. The dimensions and shape of the crater determine the strength of the potential and thus the signal generated by the PVDF. The theoretical basis for signal interpretation uses a crater diameter scaling law which was not intended for use with PVDF. In this work, a crater size scaling law has been experimentally determined, and further simulation work is being done to enhance our understanding of the mechanisms of crater formation. LS-Dyna, a smoothed particle hydrodynamics (SPH) code from the Livermore Software Technology Corp. was chosen to simulate micrometeorite impacts. SPH is known to be well suited to the large deformities found in hypervelocity impacts. It is capable of incorporating key physics phenomena, including fracture, heat transfer, melting, etc. Furthermore, unlike Eulerian methods, SPH is gridless allowing large deformities without the inclusion of unphysical erosion algorithms. Material properties are accounted for using the Grüneisen Equation of State. The results of the SPH model can

  18. The Geology of the Marcia Quadrangle of Asteroid Vesta: Assessing the Effects of Large, Young Craters

    Science.gov (United States)

    Williams, David A.; Denevi, Brett W.; Mittlefehldt, David W.; Mest, Scott C.; Schenk, Paul M.; Yingst, R. Aileen; Buczowski, Debra L.; Scully, Jennifer E. C.; Garry, W. Brent; McCord, Thomas B.; hide

    2014-01-01

    We used Dawn spacecraft data to identify and delineate geological units and landforms in the Marcia quadrangle of Vesta as a means to assess the role of the large, relatively young impact craters Marcia (approximately 63 kilometers diameter) and Calpurnia (approximately 53 kilometers diameter) and their surrounding ejecta field on the local geology. We also investigated a local topographic high with a dark-rayed crater named Aricia Tholus, and the impact crater Octavia that is surrounded by a distinctive diffuse mantle. Crater counts and stratigraphic relations suggest that Marcia is the youngest large crater on Vesta, in which a putative impact melt on the crater floor ranges in age between approximately 40 and 60 million years (depending upon choice of chronology system), and Marcia's ejecta blanket ranges in age between approximately 120 and 390 million years (depending upon choice of chronology system). We interpret the geologic units in and around Marcia crater to mark a major Vestan time-stratigraphic event, and that the Marcia Formation is one of the geologically youngest formations on Vesta. Marcia crater reveals pristine bright and dark material in its walls and smooth and pitted terrains on its floor. The smooth unit we interpret as evidence of flow of impact melts and (for the pitted terrain) release of volatiles during or after the impact process. The distinctive dark ejecta surrounding craters Marcia and Calpurnia is enriched in OH- or H-bearing phases and has a variable morphology, suggestive of a complex mixture of impact ejecta and impact melts including dark materials possibly derived from carbonaceous chondrite-rich material. Aricia Tholus, which was originally interpreted as a putative Vestan volcanic edifice based on lower resolution observations, appears to be a fragment of an ancient impact basin rim topped by a dark-rayed impact crater. Octavia crater has a cratering model formation age of approximately 280-990 million years based on counts

  19. Geology of McLaughlin Crater, Mars: A Unique Lacustrine Setting with Implications for Astrobiology

    Science.gov (United States)

    Michalski, J. R.; Niles, P. B.; Rogers, A. D.; Johnson, S. S.; Ashley, J. W.; Golombek, M. P.

    2016-01-01

    McLaughlin crater is a 92-kmdiameter Martian impact crater that contained an ancient carbonate- and clay mineral-bearing lake in the Late Noachian. Detailed analysis of the geology within this crater reveals a complex history with important implications for astrobiology [1]. The basin contains evidence for, among other deposits, hydrothermally altered rocks, delta deposits, deep water (>400 m) sediments, and potentially turbidites. The geology of this basin stands in stark contrast to that of some ancient basins that contain evidence for transient aqueous processes and airfall sediments (e.g. Gale Crater [2-3]).

  20. Crater topography on Titan: Implications for landscape evolution

    Science.gov (United States)

    Neish, C.; Kirk, R.; Lorenz, R.; Bray, V.; Schenk, P.; Stiles, B.; Turtle, E.; Cassini Radar Team

    2012-04-01

    craters on Titan (gray diamonds) compared to similarly sized, fresh craters on Ganymede (central peaks, +; central pits, *) and a handful of relaxed craters (black squares) from Bray et al. (2012). References: Bray, V., et al.: "Ganymede crater dimensions - implications for central peak and central pit formation and development". Icarus, Vol. 217, pp. 115-129, 2012. Neish, C.D., Lorenz, R.D.: "Titan’s global crater population: A new assessment". Planetary and Space Science, Vol. 60, pp. 26-33, 2012. Schenk, P.M., et al.: "Ages and interiors: the cratering record of the Galilean satellites". In: Bagenal, F., McKinnon, W.B. (Eds.), Jupiter: The Planet, Satellites, and Magnetosphere, Cambridge University Press, Cambridge, UK, pp. 427-456, 2004. Stiles, B.W., et al.: "Determining Titan surface topography from Cassini SAR data". Icarus, Vol. 202, pp. 584-598, 2009. Wood, C.A., et al.: "Impact craters on Titan". Icarus, Vol. 206, pp. 334-344, 2010.

  1. Preliminary results of radiation monitoring near uranium mines in Namibia EJOLT Project (DRAFT version)

    International Nuclear Information System (INIS)

    Chareyron, Bruno

    2012-01-01

    As a part of the EJOLT (Environmental Justice Organizations Liability and Trade) project, EARTHLIFE Namibia and CRIIRAD (Commission for Independent Research and Information about Radiation) have organised visits in areas located in the vicinity of uranium mines in Namibia In the course of an on site mission carried out between September 22 and October 2 2011, scientists from the CRIIRAD laboratory took radiation measurements in situ, and collected 14 samples of top soil, 13 samples of surface sediments of the Swakop, Gawib and Khan rivers, 11 underground water samples in the alluvium of Swakop, and Khan rivers and tap water from Arandis city, and one sample of asparagus. Solid samples have been analysed at the CRIIRAD laboratory in France (measurements performed by HpGe gamma spectrometry) and water samples have been monitored for main chemicals by LDA 26 laboratory in France and for radium 226 and radon 222 at the CRIIRAD laboratory. Some of the preliminary findings are summarised in this report: 1 - The dose rate measured by CRIIRAD on the parking of Roessing mine is about 6 times above natural background value (0.9 μSv/h compared to 0.15 μSv/h); 2 - The management of waste rock dumps needs to be improved: Some waste rocks are dumped on the banks of Khan river (at the intersection with Dome Gorge) without fencing and confinement. The radiological impact of this activity has to be studied in detail but preliminary measurements show various impacts on the environment; 3 - The finest fraction of the radioactive tailings dumped on Roessing tailings dam is blown away by the wind and contaminates the surrounding environment; 4 - The high uranium concentration in underground water collected downstream Roessing uranium mine in the Khan river and Swakop river alluvium raises the question of the origin of this uranium

  2. Preliminary results of radiation monitoring near uranium mines in Namibia EJOLT Project (DRAFT version)

    Energy Technology Data Exchange (ETDEWEB)

    Chareyron, Bruno

    2012-04-05

    As a part of the EJOLT (Environmental Justice Organizations Liability and Trade) project, EARTHLIFE Namibia and CRIIRAD (Commission for Independent Research and Information about Radiation) have organised visits in areas located in the vicinity of uranium mines in Namibia In the course of an on site mission carried out between September 22 and October 2 2011, scientists from the CRIIRAD laboratory took radiation measurements in situ, and collected 14 samples of top soil, 13 samples of surface sediments of the Swakop, Gawib and Khan rivers, 11 underground water samples in the alluvium of Swakop, and Khan rivers and tap water from Arandis city, and one sample of asparagus. Solid samples have been analysed at the CRIIRAD laboratory in France (measurements performed by HpGe gamma spectrometry) and water samples have been monitored for main chemicals by LDA 26 laboratory in France and for radium 226 and radon 222 at the CRIIRAD laboratory. Some of the preliminary findings are summarised in this report: 1 - The dose rate measured by CRIIRAD on the parking of Roessing mine is about 6 times above natural background value (0.9 {mu}Sv/h compared to 0.15 {mu}Sv/h); 2 - The management of waste rock dumps needs to be improved: Some waste rocks are dumped on the banks of Khan river (at the intersection with Dome Gorge) without fencing and confinement. The radiological impact of this activity has to be studied in detail but preliminary measurements show various impacts on the environment; 3 - The finest fraction of the radioactive tailings dumped on Roessing tailings dam is blown away by the wind and contaminates the surrounding environment; 4 - The high uranium concentration in underground water collected downstream Roessing uranium mine in the Khan river and Swakop river alluvium raises the question of the origin of this uranium

  3. How old is Autolycus crater?

    Science.gov (United States)

    Hiesinger, Harald; Pasckert, Jan Henrik; van der Bogert, Carolyn H.; Robinson, Mark S.

    2016-04-01

    Accurately determining the lunar cratering chronology is prerequisite for deriving absolute model ages (AMAs) across the lunar surface and throughout the Solar System [e.g., 1]. However, the lunar chronology is only constrained by a few data points over the last 1 Ga and there are no calibration data available between 1 and 3 Ga and beyond 3.9 Ga [2]. Rays from Autolycus and Aristillus cross the Apollo 15 landing site and presumably transported material to this location [3]. [4] proposed that at the Apollo 15 landing site about 32% of any exotic material would come from Autolycus crater and 25% would come from Aristillus crater. [5,6] proposed that the 39Ar-40Ar age of 2.1 Ga derived from three petrologically distinct, shocked Apollo 15 KREEP basalt samples, date Autolycus crater. Grier et al. [7] reported that the optical maturity (OMAT) characteristics of these craters are indistinguishable from the background values despite the fact that both craters exhibit rays that were used to infer relatively young, i.e., Copernican ages [8,9]. Thus, both OMAT characteristics and radiometric ages of 2.1 Ga and 1.29 Ga for Autolycus and Aristillus, respectively, suggest that these two craters are not Copernican in age. [10] interpreted newer U-Pb ages of 1.4 and 1.9 Ga from sample 15405 as the formation ages of Aristillus and Autolycus. If Autolycus is indeed the source of the dated exotic material collected at the Apollo 15 landing site, than performing crater size frequency distribution (CSFD) measurements for Autolycus offers the possibility to add a new calibration point to the lunar chronology, particularly in an age range that was previously unconstrained. We used calibrated and map-projected LRO NAC images to perform CSFD measurements within ArcGIS, using CraterTools [11]. CSFDs were then plotted with CraterStats [12], using the production and chronology functions of [13]. We determined ages of 3.72 and 3.85 Ga for the interior (Ai1) and ejecta area Ae3, which we

  4. The Namibia bridge management system: a tool for preservation of structures on the road network

    CSIR Research Space (South Africa)

    Roux, MP

    2010-10-01

    Full Text Available This paper describes the development and implementation of a bridge management system (BMS) for the Namibia Roads Authority (NRA). Namibia is a vast country (825 420 km2) with a very low population density and the NRA is currently responsible...

  5. Discourses of Education, Protection, and Child Labor: Case Studies of Benin, Namibia and Swaziland

    Science.gov (United States)

    Nordtveit, Bjorn Harald

    2010-01-01

    This article analyses discontinuities between local, national and international discourse in the fields of education, protection of children, and child labor, using Benin, Namibia and Swaziland as case studies. In Benin, child abuse and child labor are related to poverty, whereas in Namibia and Swaziland they are also interrelated with HIV/AIDS.…

  6. Dynamics of crater formations in immersed granular materials

    Science.gov (United States)

    Varas, G.; Vidal, V.; Géminard, J.

    2009-12-01

    Craters are part of the widespread phenomena observed in nature. Among the main applications to natural phenomena, aside from meteorite impact craters, are the formation and growth of volcanic edifices, by successive ejecta emplacement and/or erosion. The time evolution and dynamics play a crucial role here, as the competition between volcanic-jet mass-flux (degassing and ejecta) and crater-size evolution may control directly the eruptive regime. Crater morphology in dry granular material has been extensively studied, both experimentally and theoretically. Most of these studies investigate the final, steady crater shape resulting from the collision of solid bodies with the material surface and scaling laws are derived. In immersed granular material, craters generated by an underwater vortex ring, or underwater impact craters generated by landslide, have been reported. In a previous experimental study, Gostiaux et al. [Gran. Matt., 2002] have investigated the dynamics of air flowing through an immersed granular layer. They reported that, depending on the flow rate, the system exhibits two qualitatively different regimes: At small flow rate, the bubbling regime during which bubbles escape the granular layer independently one from another; At large flow rate, the open-channel regime which corresponds to the formation of a channel crossing the whole thickness of the granular bed through which air escapes almost continuously. At intermediate flow rate, a spontaneous alternation between these two regimes is observed. Here, we report the dynamics of crater formations at the free surface of an immersed granular bed, locally crossed by an ascending gas flow. We reproduce the experimental conditions of Gostiaux et al. (2002) in two dimensions: In a vertical Hele-Shaw cell, the crater consists of two sand piles which develop around the location of the gas emission. We observe that the typical size of the crater increases logarithmically with time, independently of the gas

  7. Proceedings of the Geophysical Laboratory/Lawrence Radiation Laboratory Cratering Symposium

    Energy Technology Data Exchange (ETDEWEB)

    Nordyke, Milo D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    1961-10-01

    The geological papers in this morning's session will deal descriptively with surficial features and end products of impact craters caused by meteorite falls. Such items as breccia, structural deformation, normal and inverse stratigraphy, glass (fused rock), and coesite will frequently be mentioned. Meteor and explosion crater data are presented.

  8. East Part of Sapas Mons with Flooded Crater

    Science.gov (United States)

    1991-01-01

    This Magellan image centered near 9.6 degrees north latitude, 189.5 degrees east longitude of an area 140 kilometers (87 miles) by 110 kilometers (68 miles) covers part of the eastern flank of the volcano Sapas Mons on the western edge of Atla Regio. The bright lobate features along the southern and the western part of the image, oriented in northeast to southwest directions, are lava flows that are rough at the 12.6 centimeter wavelength of the radar. These flows range in width from 5 kilometers to 25 kilometers (3 to 16 miles) with lengths of 50 kilometers to 100 kilometers (31 to 62 miles), extending off the area shown here. Additional radar-dark (smooth) flows are also present. The radar-bright linear structures in the northwest part of the image are interpreted to be faults and fractures possibly associated with the emplacement of magma in the subsurface. Located near the center of the image is a 20 kilometer (12 mile) diameter impact crater. This crater is superimposed on a northeast/southwest trending fracture while the southern part of the crater's ejecta blanket is covered by a 6 kilometer (4 mile) wide radar-bright lava flow. These relations indicate that the crater post dates an episode of fracturing and is older than the lava flows covering its southern edge. This is one of only a few places on Venus in which an impact crater is seen to be covered by volcanic deposits.

  9. Interpretation of Wild 2 Dust Fine Structure: Comparison of Stardust Aluminium Foil Craters to the Three-Dimensional Shape of Experimental Impacts by Artificial Aggregate Particles and Meteorite Powders

    Energy Technology Data Exchange (ETDEWEB)

    Kearsley, A T; Burchell, M J; Price, M C; Graham, G A; Wozniakiewicz, P J; Cole, M J; Foster, N J; Teslich, N

    2009-12-10

    New experimental results show that Stardust crater morphology is consistent with interpretation of many larger Wild 2 dust grains being aggregates, albeit most of low porosity and therefore relatively high density. The majority of large Stardust grains (i.e. those carrying most of the cometary dust mass) probably had density of 2.4 g cm{sup -3} (similar to soda-lime glass used in earlier calibration experiments) or greater, and porosity of 25% or less, akin to consolidated carbonaceous chondrite meteorites, and much lower than the 80% suggested for fractal dust aggregates. Although better size calibration is required for interpretation of the very smallest impacting grains, we suggest that aggregates could have dense components dominated by {micro}m-scale and smaller sub-grains. If porosity of the Wild 2 nucleus is high, with similar bulk density to other comets, much of the pore-space may be at a scale of tens of micrometers, between coarser, denser grains. Successful demonstration of aggregate projectile impacts in the laboratory now opens the possibility of experiments to further constrain the conditions for creation of bulbous (Type C) tracks in aerogel, which we have observed in recent shots. We are also using mixed mineral aggregates to document differential survival of pristine composition and crystalline structure in diverse fine-grained components of aggregate cometary dust analogues, impacted onto both foil and aerogel under Stardust encounter conditions.

  10. Tourism and rural community development in Namibia: policy issues review

    Directory of Open Access Journals (Sweden)

    Erling Kavita

    2016-02-01

    Full Text Available During the past decades, the tourism sector has become an increasing important issue for governments and regional agencies searching for socio-economic development. Especially in the Global South the increasing tourism demand has been seen highly beneficial as evolving tourism can create direct and indirect income and employment effects to the host regions and previously marginalised communities, with potential to aid with the poverty reduction targets. This research note reviews the existing policy and planning frameworks in relation to tourism and rural development in Namibia. Especially the policy aims towards rural community development are overviewed with focus on Community-Based Tourism (CBT initiatives. The research note involves a retrospective review of tourism policies and rural local development initiatives in Namibia where the Ministry of Environment and Tourism (MET initiated a community-based tourism policy. The policy emphasises structures and processes helping local communities to benefit from the tourism sector, and the active and coordinating involvement of communities, especially, is expected to ensure that the benefits of tourism trickle down to the local level where tourist activities take place. However, it is noted that in addition to public policy-makers also other tourism developers and private business environment in Namibia need to recognize the full potential of rural tourism development in order to meet the created politically driven promises at the policy level. In this respect, a national tourism policy could provide an enabling framework, integrating the tourism sector’s development aims to rural and community development needs in future. In addition, there is a need to coordinate a comprehensive vision of what type of rural tourism development or tourism in rural environments holds the most potential to benefit both local communities and the mainstream sector.

  11. Population characteristics of submicrometer-sized craters on regolith particles from asteroid Itokawa

    Science.gov (United States)

    Matsumoto, Toru; Hasegawa, S.; Nakao, S.; Sakai, M.; Yurimoto, H.

    2018-03-01

    We investigated impact crater structures on regolith particles from asteroid Itokawa using scanning electron microscopy. We observed the surfaces of 51 Itokawa particles, ranging from 15 μm to 240 μm in size. Craters with average diameters ranging from 10 nm to 2.8 μm were identified on 13 Itokawa particles larger than 80 μm. We examined the abundance, spatial distribution, and morphology of approximately 900 craters on six Itokawa particles. Craters with sizes in excess of 200 nm are widely dispersed, with spatial densities from 2.6 μm2 to 4.5 μm2; a fraction of the craters was locally concentrated with a density of 0.1 μm2. The fractal dimension of the cumulative crater diameters ranges from 1.3 to 2.3. Craters of several tens of nanometers in diameter exhibit pit and surrounding rim structures. Craters of more than 100 nm in diameter commonly have melted residue at their bottom. These morphologies are similar to those of submicrometer-sized craters on lunar regolith. We estimated the impactor flux on Itokawa regolith-forming craters, assuming that the craters were accumulated during direct exposure to the space environment for 102 to 104 yr. The range of impactor flux onto Itokawa particles is estimated to be at least one order of magnitude higher than the interplanetary dust flux and comparable to the secondary impact flux on the Moon. This indicates that secondary ejecta impacts are probably the dominant cratering process in the submicrometer range on Itokawa regolith particles, as well as on the lunar surface. We demonstrate that secondary submicrometer craters can be produced anywhere in centimeter- to meter-sized depressions on Itokawa's surface through primary interplanetary dust impacts. If the surface unevenness on centimeter to meter scales is a significant factor determining the abundance of submicrometer secondary cratering, the secondary impact flux could be independent of the overall shapes or sizes of celestial bodies, and the secondary

  12. Distribution of hepatitis B virus infection in Namibia

    Directory of Open Access Journals (Sweden)

    P Mhata

    2017-10-01

    Full Text Available Background. Namibia regards hepatitis B virus (HBV infection as a public health problem and introduced hepatitis B vaccinations for infants during 2009. However, information on HBV infection in the country remains limited, and effective public health interventions may be compromised in the absence of adequate evidence-based data. Available data from the World Health Organization (WHO estimate that 15 - 60% of the normal population in many African countries may be positive for one or more of the HBV serological markers. Objective. To investigate the distribution of HBV infection in Namibia, using available laboratory data for 2013. Methods. A cross-sectional descriptive study was conducted using pre-existing electronic laboratory data on HBV infection. The data were retrieved from the central Namibia Institute of Pathology laboratory in Windhoek during January - December 2013. Tests were done on the following three main groups: (i pregnant women during routine antenatal care (ANC visits; (ii patients with HIV/AIDS during antiretroviral therapy clinic visits; and (iii any other individual suspected of having HBV infection. Results. Of a total of 77 238 hepatitis B surface antigen test results retrieved countrywide, 9 087 (11.8% were positive. Of the positive results, 246/9 087 (2.7% were in children aged 0 - 14 years, with the sexes equally affected. HBV infections increased markedly, particularly among females, in the age group 15 - 39 years, reaching a peak in the age group 30 - 34 years. Routine screening of pregnant women for HBV during ANC visits was found to be systematically conducted in only two regions, Ohangwena and Khomas. Conclusions. This study showed high proportions of positive results in pregnant women, patients with HIV/AIDS and individuals suspected of having HBV infection. The Ministry of Health and Social Services and stakeholders may wish to consider improving the routine and surveillance reporting systems for viral hepatitis

  13. Stability of nuclear crater slopes in rock

    International Nuclear Information System (INIS)

    Fleming, Robert W.; Frandsen, Alton D.; LaFrenz, Robert L.

    1970-01-01

    The United States Army Engineer Nuclear Cratering Group was established in 1962 to participate with the Atomic Energy Commission in a joint research and development program to develop nuclear engineering and construction technology. A major part of this research effort has been devoted to studies of the engineering properties of craters. The program to date has included field investigations of crater properties in various media over a broad range of chemical and nuclear explosive yields, studies of man-made and natural slopes, and studies directed toward the development of analytical and empirical methods of crater stability analysis. From this background, a general understanding has been developed of the effects of a cratering explosion on the surrounding medium and of physical nature of the various crater zones which are produced. The stability of nuclear crater slopes has been a subject of prime interest in the feasibility study being conducted for an Atlantic-Pacific sea-level canal. Based on experimental evidence assembled to date, nuclear crater slopes in dry dock and dry alluvium have an initially stable configuration. There have been five nuclear craters produced to date with yields of 0.4 kt or more on which observations are based and the initial configurations of these craters have remained stable for over seven years. The medium, yield, crater dimensions, and date of event for these craters are summarized. It is interesting to note that the Sedan Crater has been subjected to strong seismic motions from nearby detonations without adverse effects

  14. Stability of nuclear crater slopes in rock

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Robert W; Frandsen, Alton D; LaFrenz, Robert L [U.S. Army Engineer Nuclear Cratering Group, Lawrence Radiation Laboratory, Livermore, CA (United States)

    1970-05-15

    The United States Army Engineer Nuclear Cratering Group was established in 1962 to participate with the Atomic Energy Commission in a joint research and development program to develop nuclear engineering and construction technology. A major part of this research effort has been devoted to studies of the engineering properties of craters. The program to date has included field investigations of crater properties in various media over a broad range of chemical and nuclear explosive yields, studies of man-made and natural slopes, and studies directed toward the development of analytical and empirical methods of crater stability analysis. From this background, a general understanding has been developed of the effects of a cratering explosion on the surrounding medium and of physical nature of the various crater zones which are produced. The stability of nuclear crater slopes has been a subject of prime interest in the feasibility study being conducted for an Atlantic-Pacific sea-level canal. Based on experimental evidence assembled to date, nuclear crater slopes in dry dock and dry alluvium have an initially stable configuration. There have been five nuclear craters produced to date with yields of 0.4 kt or more on which observations are based and the initial configurations of these craters have remained stable for over seven years. The medium, yield, crater dimensions, and date of event for these craters are summarized. It is interesting to note that the Sedan Crater has been subjected to strong seismic motions from nearby detonations without adverse effects.

  15. Long-Term Recovery of Life in the Chicxulub Crater

    Science.gov (United States)

    Lowery, C.; Jones, H.; Bralower, T. J.; Smit, J.; Rodriguez-Tovar, F. J.; Whalen, M. T.; Owens, J. D.; Expedition 364 Science Party, I. I.

    2017-12-01

    The Chicxulub Crater on the Yucatán Peninsula of Mexico was formed by the impact of an asteroid 66 Ma that caused the extinction of 75% of genera on Earth. Immediately following the impact, the decimated ecosystem began the long process of recovery, both in terms of primary productivity and species diversity. This well-documented process was heterogeneous across the world ocean, but until the present time it has been inaccessible at ground zero of the impact. IODP/ICDP Exp. 364 recovered 9.5 m of pelagic limestone spanning the entire Paleocene, including a continuous section spanning the first 5 myr following the impact. The Chicxulub Crater is the largest known marine impact crater on Earth, and the recovery of the ecosystem presented here is the first such record of long-term primary succession in the sterile zone of a large impact crater. Planktic and benthic foraminifera, calcareous nannoplankton, calcispheres, bioturbation, and geochemical proxies all indicate that export productivity in the Chicxulub Crater recovered rapidly (within 30 kyr) following the impact. Recovery in terms of diversity and species abundance took much longer, and varied between groups. Planktic foraminifera quickly diversified, with all common Paleocene tropical/subtropical species appearing roughly when expected. Trace fossils appear rapidly after the event, with a progressive recovery through the lowermost Paleocene. Calcareous nannoplankton took much longer to recover, and disaster taxa like Braarudosphaera dominated the assemblage well into the late Paleocene. Paleoecology and geochemistry relate these trends to oceanographic conditions within the Chicxulub Crater. Planktic foraminifera from known depth habitats, including Morozovellids, Acarininids, Chiloguembelinids, and Subbotinids, track changes in the water column structure and paleoredox conditions within the crater. Diverse and abundant macro- and microbenthic organisms indicate food availability and good oxygen conditions

  16. A Tale of Two Craters

    Science.gov (United States)

    2003-01-01

    [figure removed for brevity, see original site] In western Acidalia, two craters of similar size (a few km's) dramatically display the effects of geologic activity. The younger one on the left has been left relatively well preserved, retaining a sharp rim crest, a classic bowl shape, and a clearly defined ejecta blanket. The older one on the right likely has experienced a flood of lava that covered over the ejecta and filled in the bowl (note the breach in the rim). Its rim crest has been worn down by a multitude of subsequent impacts.Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.Image information: VIS instrument. Latitude 35.9, Longitude 311.1 East (48.9 West). 19 meter/pixel resolution.

  17. Detection and characterization of buried lunar craters with GRAIL data

    Science.gov (United States)

    Sood, Rohan; Chappaz, Loic; Melosh, Henry J.; Howell, Kathleen C.; Milbury, Colleen; Blair, David M.; Zuber, Maria T.

    2017-06-01

    We used gravity mapping observations from NASA's Gravity Recovery and Interior Laboratory (GRAIL) to detect, characterize and validate the presence of large impact craters buried beneath the lunar maria. In this paper we focus on two prominent anomalies detected in the GRAIL data using the gravity gradiometry technique. Our detection strategy is applied to both free-air and Bouguer gravity field observations to identify gravitational signatures that are similar to those observed over buried craters. The presence of buried craters is further supported by individual analysis of regional free-air gravity anomalies, Bouguer gravity anomaly maps, and forward modeling. Our best candidate, for which we propose the informal name of Earhart Crater, is approximately 200 km in diameter and forms part of the northwestern rim of Lacus Somniorum, The other candidate, for which we propose the informal name of Ashoka Anomaly, is approximately 160 km in diameter and lies completely buried beneath Mare Tranquillitatis. Other large, still unrecognized, craters undoubtedly underlie other portions of the Moon's vast mare lavas.

  18. Ancient aqueous environments at Endeavour crater, Mars

    Science.gov (United States)

    Arvidson, R. E.; Squyres, S. W.; Bell, J.F.; Catalano, J.G.; Clark, B. C.; Crumpler, L.S.; de Souza, P.A.; Fairén, A.G.; Farrand, W. H.; Fox, V.K.; Gellert, Ralf; Ghosh, A.; Golombeck, M.P.; Grotzinger, J.P.; Guinness, E.A.; Herkenhoff, Kenneth E.; Jolliff, B.L.; Knoll, A.H.; Li, R.; McLennan, S.M.; Ming, D. W.; Mittlefehldt, D. W.; Moore, Johnnie N.; Morris, R.V.; Murchie, S.L.; Parker, T.J.; Paulsen, G.; Rice, J.W.; Ruff, S.W.; Smith, M.D.; Wolff, M.J.

    2014-01-01

    Opportunity has investigated in detail rocks on the rim of the Noachian age Endeavour crater, where orbital spectral reflectance signatures indicate the presence of Fe+3-rich smectites. The signatures are associated with fine-grained, layered rocks containing spherules of diagenetic or impact origin. The layered rocks are overlain by breccias, and both units are cut by calcium sulfate veins precipitated from fluids that circulated after the Endeavour impact. Compositional data for fractures in the layered rocks suggest formation of Al-rich smectites by aqueous leaching. Evidence is thus preserved for water-rock interactions before and after the impact, with aqueous environments of slightly acidic to circum-neutral pH that would have been more favorable for prebiotic chemistry and microorganisms than those recorded by younger sulfate-rich rocks at Meridiani Planum.

  19. Recent copper-working sites in the Khuiseb drainage, Namibia

    International Nuclear Information System (INIS)

    Kinahan, J.

    1982-01-01

    In the article radiocarbon dates are presented for the production of copper artefacts in the Khomas highlands of Namibia during the last four centuries and significant associations are also briefly described. Results from the study suggest that copper beads were widely distributed in Namibia over at least the last 400 years. The archaeological evidence of copper-working in the Khuiseb valley is in partial agreement with historical records of the eighteenth century. The scale of the industry appears to have been small, and its apparent portability suited to a nonsedentary way of life based primarily on foraging. Collectively the group of radiocarbon dates suggests that copper smelting in the Khomas highlands post-dates A.D. 1420 (Pta-2573) while the activity may have continued until as late as A.D. 1840 (Pta-2739). Most of the measurements, however, point to a date in the seventeenth century indicating that the sites are roughly contemporaneous and represent a relatively short time period of about a century

  20. Job satisfaction among urban secondary-school teachers in Namibia

    Directory of Open Access Journals (Sweden)

    Evy George

    2008-05-01

    Full Text Available An exploratory study on the role of extrinsic and intrinsic factors in determining job satisfaction amongst urban secondary-school teachers in Namibia was undertaken. Biographical variables pertaining to the teachers' gender, age, marital status, school resources, teaching experience, academic qualifications, and rank were investigated to determine whether these had any significant relevance, or made any notable contribution, to the level of job satisfaction experienced. Also, the correlation between burnout and job satisfaction was investigated to determine the extent to which these two factors are related. A sample of 337 secondary-school teachers randomly selected from 17 government schools, in the Windhoek region of Namibia, voluntarily participated in the study. Results showed significant levels of dissatisfaction pertaining to intrinsic factors of work and, more especially, those factors relating to school area and rank. A significant correlation between levels of burnout and job satisfaction was found, particularly in respect of emotional exhaustion and depersonalization, which were shown to correlate with low levels of job satisfaction. Limitations and recommendations pertaining to the study are discussed.

  1. Development and Expansion of the Langer Heinrich Operation in Namibia

    Energy Technology Data Exchange (ETDEWEB)

    Marsh, D., E-mail: dave.marsh@paladinenergy.com.au [Paladin Energy Ltd, Perth, Western Australia (Australia)

    2014-05-15

    The Langer Heinrich Uranium Mine (LHU) is located in the west of central Namibia, Southern Africa. It lies 80 km east of the major deepwater port at Walvis Bay and the coastal town of Swakopmund. Designed to produce 2.6Mlb/a U{sub 3}O{sub 8}, LHU was the first conventional mining and processing operation to be brought into production in over a decade. The construction and staged commissioning of the project was successfully achieved on 28 December 2006 and the mine was officially opened by the President of Namibia on the 14{sup th} March 2007. The ramp up to nameplate production was hampered early on by some mechanical and process issues all of which required technical solutions to be developed. With these in place, production now exceeds nameplate and lessons learnt have been incorporated into an expansion to 3.7 Mlb/a currently nearing completion. Further expansion options are also being evaluated and a number of innovative flowsheet developments are under consideration, driven by a recent, large increase in the proven reserves. This paper tracks the development of the LHU operation focusing largely on the metallurgical processes employed, some lessons learnt and some considerations for the future. (author)

  2. Burnout amongst urban secondary school teachers in Namibia

    Directory of Open Access Journals (Sweden)

    Dap Louw

    2011-11-01

    Motivation for the study: The study focused on the magnitude and nature of burnout amongst Namibian teachers as well as the influence of biographical factors on their levels of burnout. Another aim was to determine the extent to which the results of this study correlate with research findings in other countries. Research design, approach and method: The researchers used a non-experimental research method. The study involved more than 300 secondary school teachers from the Windhoek region of Namibia. They administered the Maslach Burnout Inventory (MBI and a biographical questionnaire to achieve the goals of the study. Main findings: The main findings of the study were that the participants experienced similar levels of burnout compared to teachers in other countries. This was especially true for emotional exhaustion. Teaching experience was the biographical variable that yielded the most significant positive correlation with burnout. Practical/managerial implications: The education authorities should address the emotional needs of secondary school teachers in Namibia urgently. They should introduce effective burnout intervention and prevention programmes. These programmes could result in higher levels of job satisfaction and educational effectiveness. They could also lead to increased general fulfilment and better teacher retention.

  3. Premarital fertility in Namibia: trends, factors and consequences.

    Science.gov (United States)

    Garenne, Michel; Zwang, Julien

    2006-03-01

    Premarital fertility, defined as fertility before first marriage, was found to be highly prevalent in Namibia. According to data from the 1992 and 2000 DHS surveys, the proportion of premarital births was 43% for all births, and 60% for the first birth. This seemed to be primarily due to a late mean age at first marriage (26.4 years) and low levels of contraception before first marriage. Data were analysed using a variety of demographic methods, including multiple decrement life table and multivariate logistic models. Major variations were found by ethno-linguistic groups: Herero and Nama/Damara had the highest levels of premarital fertility (above 60%); Ovambo and Lozi had intermediate levels of premarital fertility (around 40%); Kavongo and San appeared to have kept a more traditional behaviour of early marriage and low levels of premarital fertility (around 20%). The largest ethno-linguistic group, the Ovambo, were in a special situation, with fast increasing age at marriage and average level of premarital fertility. Whites and mixed races also differed, with Afrikaans-speaking groups having a behaviour closer to the average, whereas other Europeans had less premarital fertility despite an average age at marriage. Ethnic differences remained stable after controlling for various socioeconomic factors, such as urbanization, level of education, wealth, access to mass media, and religion. Results are discussed in light of the population dynamics and political history of Namibia in the 20th century.

  4. The Namibia Early Flood Warning System, A CEOS Pilot Project

    Science.gov (United States)

    Mandl, Daniel; Frye, Stuart; Cappelaere, Pat; Sohlberg, Robert; Handy, Matthew; Grossman, Robert

    2012-01-01

    Over the past year few years, an international collaboration has developed a pilot project under the auspices of Committee on Earth Observation Satellite (CEOS) Disasters team. The overall team consists of civilian satellite agencies. For this pilot effort, the development team consists of NASA, Canadian Space Agency, Univ. of Maryland, Univ. of Colorado, Univ. of Oklahoma, Ukraine Space Research Institute and Joint Research Center(JRC) for European Commission. This development team collaborates with regional , national and international agencies to deliver end-to-end disaster coverage. In particular, the team in collaborating on this effort with the Namibia Department of Hydrology to begin in Namibia . However, the ultimate goal is to expand the functionality to provide early warning over the South Africa region. The initial collaboration was initiated by United Nations Office of Outer Space Affairs and CEOS Working Group for Information Systems and Services (WGISS). The initial driver was to demonstrate international interoperability using various space agency sensors and models along with regional in-situ ground sensors. In 2010, the team created a preliminary semi-manual system to demonstrate moving and combining key data streams and delivering the data to the Namibia Department of Hydrology during their flood season which typically is January through April. In this pilot, a variety of moderate resolution and high resolution satellite flood imagery was rapidly delivered and used in conjunction with flood predictive models in Namibia. This was collected in conjunction with ground measurements and was used to examine how to create a customized flood early warning system. During the first year, the team made use of SensorWeb technology to gather various sensor data which was used to monitor flood waves traveling down basins originating in Angola, but eventually flooding villages in Namibia. The team made use of standardized interfaces such as those articulated

  5. Ceres' intriguing Occator crater and its faculae: formation and evolution

    Science.gov (United States)

    Buczkowski, D.; Scully, J. E. C.; Bowling, T.; Bu, C.; Castillo, J. C.; Jaumann, R.; Longobardo, A.; Nathues, A.; Neesemann, A.; Palomba, E.; Platz, T.; Quick, L. C.; Raponi, A.; Raymond, C. A.; Ruesch, O.; Russell, C. T.; Schenk, P.; Stein, N.

    2017-12-01

    Since March 2015, the Dawn spacecraft has orbited and explored Ceres, which is a dwarf planet and the largest object in the asteroid belt (radius 470 km). One of the most intriguing features on Ceres' surface is Occator crater, a 92-km-diameter impact crater that contains distinctive bright spots, called faculae, within its floor (Nathues et al., 2015; Russell et al., 2016; Schenk et al., 2017). Occator crater has been dated to 20-30 million years old (Nathues et al., 2017; Neesemann et al., 2017). The single scattering albedo of Occator's faculae is 0.67-0.80, which is greater than Ceres' average single scattering albedo of 0.09-0.11 (Li et al., 2016). The central facula is named Cerealia Facula, and is located in a 9 km wide and 700 m deep pit. There are also multiple additional faculae in the eastern crater floor, which are named the Vinalia Faculae. The faculae are mostly composed of sodium carbonate, are distinct from Ceres' average surface composition and are proposed to be the solid residues of crystallized brines (De Sanctis et al., 2016). The presence of such bright, apparently fresh, material on the surface of a dwarf planet that is billions of years old is intriguing, and indicates that active processes involving brines occurred within the geologically recent past. The Dawn Science Team has investigated whether the processes that formed the crater and the faculae are entirely endogenic, entirely exogenic or a combination of both. For example, the extensive lobate materials within the crater floor have been proposed to be impact melt, mass wasting deposits or cryolava flows (e.g. Buczkowski et al., 2017; Jaumann et al., 2017; Nathues et al., 2017; Schenk et al., 2017). Each possibility has the potential to provide fascinating insights into Ceres' evolution, including the potential for liquids within Ceres' interior today. The team's in-depth investigation of Occator crater will be presented in an upcoming special issue of the journal Icarus. This special

  6. Stratigraphy of the crater Copernicus

    Science.gov (United States)

    Paquette, R.

    1984-01-01

    The stratigraphy of copernicus based on its olivine absorption bands is presented. Earth based spectral data are used to develop models that also employ cratering mechanics to devise theories for Copernican geomorphology. General geologic information, spectral information, upper and lower stratigraphic units and a chart for model comparison are included in the stratigraphic analysis.

  7. Polycentrism and Poverty: Experiences of Rural Water Supply Reform in Namibia

    Directory of Open Access Journals (Sweden)

    Thomas Falk

    2009-02-01

    This paper investigates how polycentric rural water supply reform impacts on natural resource management and water users’ livelihoods in three communal areas of Namibia. The analysis takes into account the effects of historic discriminative policies and the resulting low financial, human and social capital of rural communities. We conclude that the devolution of institutional and financial responsibility for water supply to users has had a positive impact on rural water management. However, the introduction of cost recovery principles conflicts with the objectives of the Namibian government to alleviate poverty and inequality. The high level of inequality within the country as a whole and also within communities impedes the development of fair fee systems. Polycentrism faces the major challenge of building on existing structures without replicating historic injustices. It allows, however, for the state to mitigate any negative impact on livelihoods. While the reform is in the process of full implementation, the government is discussing various options of how the poor can be guaranteed access to water without diminishing their development opportunities. The Namibian experience demonstrates the difficulties in developing effective incentive mechanisms without undermining major social objectives. Our analyses show that, compared to naive monocentric governance approaches, polycentrism offers much broader opportunities for achieving multidimensional objectives. Nonetheless, a reform does not become successful simply because it is polycentric.

  8. Imaging the Buried Chicxulub Crater with Gravity Gradients and Cenotes

    Science.gov (United States)

    Hildebrand, A. R.; Pilkington, M.; Halpenny, J. F.; Ortiz-Aleman, C.; Chavez, R. E.; Urrutia-Fucugauchi, J.; Connors, M.; Graniel-Castro, E.; Camara-Zi, A.; Vasquez, J.

    1995-09-01

    Differing interpretations of the Bouguer gravity anomaly over the Chicxulub crater, Yucatan Peninsula, Mexico, have yielded diameter estimates of 170 to 320 km. Knowing the crater's size is necessary to quantify the lethal perturbations to the Cretaceous environment associated with its formation. The crater's size (and internal structure) is revealed by the horizontal gradient of the Bouguer gravity anomaly over the structure, and by mapping the karst features of the Yucatan region. To improve our resolution of the crater's gravity signature we collected additional gravity measurements primarily along radial profiles, but also to fill in previously unsurveyed areas. Horizontal gradient analysis of Bouguer gravity data objectively highlights the lateral density contrasts of the impact lithologies and suppresses regional anomalies which may obscure the gravity signature of the Chicxulub crater lithologies. This gradient technique yields a striking circular structure with at least 6 concentric gradient features between 25 and 85 km radius. These features are most distinct in the southwest probably because of denser sampling of the gravity field. Our detailed profiles detected an additional feature and steeper gradients (up to 5 mGal/km) than the original survey. We interpret the outer four gradient maxima to represent concentric faults in the crater's zone of slumping as is also revealed by seismic reflection data. The inner two probably represent the margin of the central uplift and the peak ring and or collapsed transient cavity. Radial gradients in the SW quadrant over the inferred ~40 km-diameter central uplift (4) may represent structural "puckering" as revealed at eroded terrestrial craters. Gradient features related to regional gravity highs and lows are visible outside the crater, but no concentric gradient features are apparent at distances > 90 km radius. The marginal gradient features may be modelled by slump faults as observed in large complex craters on

  9. Geomorphometric analysis of selected Martian craters using polar coordinate transformation

    Science.gov (United States)

    Magyar, Zoltán; Koma, Zsófia; Székely, Balázs

    2016-04-01

    Centrally symmetric landform elements are very common features on the surface of the planet Mars. The most conspicuous ones of them are the impact craters of various size. However, a closer look on these features reveals that they show often asymmetric patterns as well. These are partially related to the geometry of the trajectory of the impacting body, but sometimes it is a result of surface processes (e.g., freeze/thaw cycles, mass movements). Geomorphometric studies have already been carried out to reveal these pecularities. Our approach, the application of polar coordinate transformation (PCT) very sensitively enhances the non-radial and non-circular shapes. We used digital terrain models (DTMs) derived from the ESA Mars Express HRSC imagery. The original DTM or its derivatives (e.g. slope angle or aspect) are PCT transformed. We analyzed the craters inter alia with scattergrams in polar coordinates. The resulting point cloud can be used directly for the analysis, but in some cases an interpolation should be applied to enhance certain non-circular features (especially in case of smaller craters). Visual inspection of the crater slopes, coloured by the aspect, reveals smaller features. Some of them are processing artefacts, but many of them are related to local undulations in the topography or indications of mass movements. In many cases the undulations of the crater rim are due to erosional processes. The drawbacks of the technology are related to the uneven resolution of the projected image: features in the crater centre should be left out from the analysis because PCT has a low resolution around the projection center. Furthermore, the success of the PCT depends on the correct definition of the projection centre: erroneously centered images are not suitable for analysis. The PCT transformed images are also suitable for radial averaging and calculation of standard deviations, resulting in typical, comparable craters shapes. These studies may lead to a deeper

  10. Namibia's transition from whole blood-derived pooled platelets to single-donor apheresis platelet collections

    NARCIS (Netherlands)

    Pitman, John P.; Basavaraju, Sridhar V.; Shiraishi, Ray W.; Wilkinson, Robert; von Finckenstein, Bjorn; Lowrance, David W.; Marfin, Anthony A.; Postma, Maarten; Mataranyika, Mary; Smit Sibinga, Cees Th.

    BACKGROUNDFew African countries separate blood donations into components; however, demand for platelets (PLTs) is increasing as regional capacity to treat causes of thrombocytopenia, including chemotherapy, increases. Namibia introduced single-donor apheresis PLT collections in 2007 to increase PLT

  11. The History of Labour Hire in Namibia: A Lesson for South Africa ...

    African Journals Online (AJOL)

    Labour hire, the practice of hiring out employees to clients by a labour broker, ... of Namibia's history since the early 1900s in the form of the contract labour system. ... true employment relationship; job security; automatic termination; proposed ...

  12. Mineralogical Diversity and Geology of Humboldt Crater Derived Using Moon Mineralogy Mapper Data

    Science.gov (United States)

    Martinot, M.; Besse, S.; Flahaut, J.; Quantin-Nataf, C.; Lozac'h, L.; van Westrenen, W.

    2018-02-01

    Moon Mineralogy Mapper (M3) spectroscopic data and high-resolution imagery data sets were used to study the mineralogy and geology of the 207 km diameter Humboldt crater. Analyses of M3 data, using a custom-made method for M3 spectra continuum removal and spectral parameters calculation, reveal multiple pure crystalline plagioclase detections within the Humboldt crater central peak complex, hinting at its crustal origin. However, olivine, spinel, and glass are observed in the crater walls and rims, suggesting these minerals derive from shallower levels than the plagioclase of the central peak complex. High-calcium pyroxenes are detected in association with volcanic deposits emplaced on the crater's floor. Geologic mapping was performed, and the age of Humboldt crater's units was estimated from crater counts. Results suggest that volcanic activity within this floor-fractured crater spanned over a billion years. The felsic mineralogy of the central peak complex region, which presumably excavated deeper material, and the shallow mafic minerals (olivine and spinel) detected in Humboldt crater walls and rim are not in accordance with the general view of the structure of the lunar crust. Our observations can be explained by the presence of a mafic pluton emplaced in the anorthositic crust prior to the Humboldt-forming impact event. Alternatively, the excavation of Australe basin ejecta could explain the observed mineralogical detections. This highlights the importance of detailed combined mineralogical and geological remote sensing studies to assess the heterogeneity of the lunar crust.

  13. Mineralogical Diversity and Geology of Humboldt Crater Derived Using Moon Mineralogy Mapper Data.

    Science.gov (United States)

    Martinot, M; Besse, S; Flahaut, J; Quantin-Nataf, C; Lozac'h, L; van Westrenen, W

    2018-02-01

    Moon Mineralogy Mapper (M 3 ) spectroscopic data and high-resolution imagery data sets were used to study the mineralogy and geology of the 207 km diameter Humboldt crater. Analyses of M 3 data, using a custom-made method for M 3 spectra continuum removal and spectral parameters calculation, reveal multiple pure crystalline plagioclase detections within the Humboldt crater central peak complex, hinting at its crustal origin. However, olivine, spinel, and glass are observed in the crater walls and rims, suggesting these minerals derive from shallower levels than the plagioclase of the central peak complex. High-calcium pyroxenes are detected in association with volcanic deposits emplaced on the crater's floor. Geologic mapping was performed, and the age of Humboldt crater's units was estimated from crater counts. Results suggest that volcanic activity within this floor-fractured crater spanned over a billion years. The felsic mineralogy of the central peak complex region, which presumably excavated deeper material, and the shallow mafic minerals (olivine and spinel) detected in Humboldt crater walls and rim are not in accordance with the general view of the structure of the lunar crust. Our observations can be explained by the presence of a mafic pluton emplaced in the anorthositic crust prior to the Humboldt-forming impact event. Alternatively, the excavation of Australe basin ejecta could explain the observed mineralogical detections. This highlights the importance of detailed combined mineralogical and geological remote sensing studies to assess the heterogeneity of the lunar crust.

  14. Crater relaxation on Titan aided by low thermal conductivity sand infill

    Science.gov (United States)

    Schurmeier, Lauren R.; Dombard, Andrew J.

    2018-05-01

    Titan's few impact craters are currently many hundreds of meters shallower than the depths expected. Assuming these craters initially had depths equal to that of similar-size fresh craters on Ganymede and Callisto (moons of similar size, composition, and target lithology), then some process has shallowed them over time. Since nearly all of Titan's recognized craters are located within the arid equatorial sand seas of organic-rich dunes, where rain is infrequent, and atmospheric sedimentation is expected to be low, it has been suggested that aeolian infill plays a major role in shallowing the craters. Topographic relaxation at Titan's current heat flow was previously assumed to be an unimportant process on Titan due to its low surface temperature (94 K). However, our estimate of the thermal conductivity of Titan's organic-rich sand is remarkably low (0.025 W m-1 K-1), and when in thick deposits, will result in a thermal blanketing effect that can aid relaxation. Here, we simulate the relaxation of Titan's craters Afekan, Soi, and Sinlap including thermal effects of various amounts of sand inside and around Titan's craters. We find that the combination of aeolian infill and subsequent relaxation can produce the current crater depths in a geologically reasonable period of time using Titan's current heat flow. Instead of needing to fill completely the missing volume with 100% sand, only ∼62%, ∼71%, and ∼97%, of the volume need be sand at the current basal heat flux for Afekan, Soi, and Sinlap, respectively. We conclude that both processes are likely at work shallowing these craters, and this finding contributes to why Titan overall lacks impact craters in the arid equatorial regions.

  15. Evolution of Occator Crater on (1) Ceres

    Energy Technology Data Exchange (ETDEWEB)

    Nathues, A.; Platz, T.; Thangjam, G.; Hoffmann, M.; Corre, L. Le; Reddy, V.; Kallisch, J. [Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Goettingen (Germany); Mengel, K. [IELF, TU Clausthal, Adolph-Roemer-Straße 2A, 38678 Clausthal-Zellerfeld (Germany); Cloutis, E. A. [University of Winnipeg, Winnipeg, MB R3B 2E (Canada); Crown, D. A., E-mail: nathues@mps.mpg.de, E-mail: platz@mps.mpg.de, E-mail: thangjam@mps.mpg.de, E-mail: hoffmann@mps.mpg.de, E-mail: kallisch@mps.mpg.de, E-mail: gkmengel@t-online.de, E-mail: e.cloutis@uwinnipeg.ca, E-mail: lecorre@psi.edu, E-mail: reddy@psi.edu, E-mail: crown@psi.edu [Planetary Science Institute, 1700 East Fort Lowell Rd, Suite 106, Tucson, AZ 85719-2395 (United States)

    2017-03-01

    The dwarf planet Ceres (diameter 939 km) is the largest object in the main asteroid belt. Recent investigations suggest that Ceres is a thermally evolved, volatile-rich body with potential geological activity, a body which was never completely molten but possibly differentiated into a rocky core, an ice-rich mantle, and which may contain remnant internal liquid water. Thermal alteration and exogenic material infall contribute to producing a (dark) carbonaceous chondritic-like surface containing ammoniated phyllosilicates. Here we report imaging and spectroscopic analyses of Occator crater derived from the Framing Camera and the Visible and Infrared Spectrometer onboard Dawn. We found that the central bright spot (Cerealia Facula) of Occator is ∼30 Myr younger than the crater itself. The central spot is located in a central pit which contains a dome that is spectrally homogenous, exhibiting absorption features that are consistent with carbonates. Multiple radial fractures across the dome indicate an extrusive formation process. Our results lead us to conclude that the floor region was subject to past endogenic activity. Dome and bright material in its vicinity formed likely due to a long-lasting, periodic, or episodic ascent of bright material from a subsurface reservoir rich in carbonates. Originally triggered by an impact event, gases, possibly dissolved from a subsurface water/brine layer, enabled material rich in carbonates to ascend through fractures and be deposited onto the surface.

  16. Creating a Business Plan for a Start-up Business Consultancy in Namibia

    OpenAIRE

    von Wietersheim, Julia

    2011-01-01

    The objective of this Thesis is to investigate the process of creating an extensive Business Plan and thereby to practically apply the theory studied during the Degree Programme of International Business. To achieve this objective, a practical business plan for a start-up Business Consultancy in Namibia (called VW-Business Consulting) is created, which at the same time provides a deeper understanding of the current demand for, and awareness of, business consulting companies in Namibia. An...

  17. Crater formation by single ions, cluster ions and ion "showers"

    CERN Document Server

    Djurabekova, Flyura; Timko, Helga; Nordlund, Kai; Calatroni, Sergio; Taborelli, Mauro; Wuensch, Walter

    2011-01-01

    The various craters formed by giant objects, macroscopic collisions and nanoscale impacts exhibit an intriguing resemblance in shapes. At the same time, the arc plasma built up in the presence of sufficiently high electric fields at close look causes very similar damage on the surfaces. Although the plasma–wall interaction is far from a single heavy ion impact over dense metal surfaces or the one of a cluster ion, the craters seen on metal surfaces after a plasma discharge make it possible to link this event to the known mechanisms of the crater formations. During the plasma discharge in a high electric field the surface is subject to high fluxes (~1025 cm-2s-1) of ions with roughly equal energies typically of the order of a few keV. To simulate such a process it is possible to use a cloud of ions of the same energy. In the present work we follow the effect of such a flux of ions impinging the surface in the ‘‘shower’’ manner, to find the transition between the different mechanisms of crater formati...

  18. Ovahimba community in Namibia ventures into crowdsourcing design

    DEFF Research Database (Denmark)

    Stanley, Colin; Winschiers-Theophilus, Heike; Blake, Edwin

    2016-01-01

    Mobile crowdsourcing presents a new avenue for remote communities to participate in socio-economic activities. We are co-designing a mobile crowdsourcing platform to support rural indigenous communities in formulating their own tasks to be crowdsourced rather than completing tasks for others. We ...... present one full simulated cycle of task formulation and evaluation by a pilot community in Northern Namibia. Observations and interactions led to a set of requirements and design implications to support the inclusion of OvaHimba communities into crowdsourcing activities.......Mobile crowdsourcing presents a new avenue for remote communities to participate in socio-economic activities. We are co-designing a mobile crowdsourcing platform to support rural indigenous communities in formulating their own tasks to be crowdsourced rather than completing tasks for others. We...

  19. Magnetic/isotopic characteristic of the spherule-rich impact ejecta blanket from the Chicxulub crater: analog for robotic exploration of similar deposits on Mars

    Czech Academy of Sciences Publication Activity Database

    Kletetschka, Günther

    2007-01-01

    Roč. 39, č. 5 (2007), s. 12-12 ISSN 0016-7592. [Rocky Mountain Section - Annual Meeting /59./. 07.05.2007-09.05.2007, St. George] Keywords : magnetic * isotopes * spherules * impact * Mars Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics http://gsa.confex.com/gsa/2007RM/finalprogram/abstract_121718.htm

  20. Geometric interpretation of the ratio of overall diameter to rim crest diameter for lunar and terrestrial craters.

    Science.gov (United States)

    Siegal, B. S.; Wickman, F. E.

    1973-01-01

    An empirical linear relationship has been established by Pike (1967) between the overall diameter and the rim crest diameter for rimmed, flat-floored as well as bowl-shaped, lunar and terrestrial craters formed by impact and explosion. A similar relationship for experimentally formed fluidization craters has been established by Siegal (1971). This relationship is examined in terms of the geometry of the crater and the slope angles of loose materials. The parameter varies from 1.40 to 1.65 and is found to be dependent on mean interior flat floor radius, exterior and interior rim slope angles, angle of aperture of the crater cone, and the volume fraction of crater void accounted for in the rim. The range of the observed parameter can be understood in terms of simple crater geometry by realistic values of the five parameters.

  1. Floor-fractured craters on the Moon: an evidence of past intrusive magmatic activity

    Science.gov (United States)

    Thorey, C.; Michaut, C.

    2012-12-01

    Floor-fractured lunar craters (FFC's) are a class of craters modified by post impact mechanisms. They are defined by distinctive shallow, often plate-like or convex floors, wide floor moats and radial, concentric and polygonal floor-fractures, suggesting an endogenous process of modification. Two main mechanisms have been proposed to account for such observations : 1) viscous relaxation and 2) spreading of magmatic intrusions at depth below the crater. Here, we propose to test the case of magmatic intrusions. We develop a model for the dynamics of magma spreading below an elastic crust with a crater-like topography and above a rigid horizontal surface. Results show first that the lithostatic pressure increase at the crater rim prevents the intrusion from spreading horizontally giving rise to intrusion thickening and to an uplift of the crater floor. Second, the deformation of the overlying crust exerts a strong control on the intrusion shape, and hence, on the nature of the crater floor uplift. As the deformation can only occur over a minimum flexural wavelength noted Λ, the intrusion shape shows a bell-shaped geometry for crater radius smaller than 3Λ, or a flat top with smooth edges for crater radius larger than 3Λ. For given crustal elastic properties, the crust flexural wavelength increases with the intrusion depth. Therefore, for a large intrusion depth or small crater size, we observe a convex uplift of the crater floor. On the contrary, for a small intrusion depth or large crater size, the crater floor undergoes a piston-like uplift and a circular moat forms just before the rim. The depth of the moat is controlled by the thickening of the crust at the crater rim. On the contrary to viscous relaxation models, our model is thus able to reproduce most of the features of FFC's, including small-scale features. Spreading of a magmatic intrusion at depth can thus be considered as the main endogenous mechanism at the origin of the deformations observed at FFC

  2. Testing models for the formation of the equatorial ridge on Iapetus via crater counting

    Science.gov (United States)

    Damptz, Amanda L.; Dombard, Andrew J.; Kirchoff, Michelle R.

    2018-03-01

    Iapetus's equatorial ridge, visible in global views of the moon, is unique in the Solar System. The formation of this feature is likely attributed to a key event in the evolution of Iapetus, and various models have been proposed as the source of the ridge. By surveying imagery from the Cassini and Voyager missions, this study aims to compile a database of the impact crater population on and around Iapetus's equatorial ridge, assess the relative age of the ridge from differences in cratering between on ridge and off ridge, and test the various models of ridge formation. This work presents a database that contains 7748 craters ranging from 0.83 km to 591 km in diameter. The database includes the study area in which the crater is located, the latitude and longitude of the crater, the major and minor axis lengths, and the azimuthal angle of orientation of the major axis. Analysis of crater orientation over the entire study area reveals that there is no preference for long-axis orientation, particularly in the area with the highest resolution. Comparison of the crater size-frequency distributions show that the crater distribution on the ridge appears to be depleted in craters larger than 16 km with an abruptly enhanced crater population less than 16 km in diameter up to saturation. One possible interpretation is that the ridge is a relatively younger surface with an enhanced small impactor population. Finally, the compiled results are used to examine each ridge formation hypothesis. Based on these results, a model of ridge formation via a tidally disrupted sub-satellite appears most consistent with our interpretation of a younger ridge with an enhanced small impactor population.

  3. Impact microcraters on an Australasian microtektite

    Digital Repository Service at National Institute of Oceanography (India)

    ShyamPrasad, M.; Sudhakar, M.

    Microcraters attributable to impact have been discovered on an Australasian microtektite from a core in the Central Indian Basin. The craters resemble lunar microcraters and those generated during impact experiments. The largest crater here, which...

  4. Disaster risk reduction in the Omusati and Oshana regions of Namibia

    Directory of Open Access Journals (Sweden)

    Elina Amadhila

    2013-08-01

    Full Text Available Namibia often experiences heavy rains in the north and north-eastern parts of the country, which results in severe flooding. For this reason, the country has endorsed the Hyogo Framework for Action (HFA which seeks to develop the resilience of nations and communities to disasters and to assist countries to move away from the approach of emergency response to one of integrated disaster risk reduction. The aim of this article is to assess the resilience of the communities within the identified regions. A quantitative questionnaire was designed to assess people at risk of disaster related impacts. The questionnaire used 20 indicators to measure the level of progress at local level and how local governance plays a role in the mitigation and management of disasters. Analysis of data was done on a limited number of descriptors such as age, gender and local governance involvement, amongst others. There was generally a very high perception of threat (38% in the study regions. Women perceived threat more accurately (mean = 4.09 than men. The community perceived threat more accurately than local government and civil society (mean = 4.08.

  5. Zoonoses: a potential obstacle to the growing wildlife industry of Namibia

    Directory of Open Access Journals (Sweden)

    Kudakwashe Magwedere

    2012-10-01

    Full Text Available Zoonoses, which account for approximately 75% of emerging human infectious diseases worldwide, pose a re-emerging threat to public health. With an ever-increasing interrelationship between humans, livestock and wildlife species, the threat to human health will rise to unprecedented levels. Wildlife species contribute to the majority of emerging diseases; therefore, there is an urgent need to define control systems of zoonoses of wildlife origin but very little information exists. In this review, we examine prevalent zoonotic infections reported in Namibia between 1990 and 2009 and assess their potential impact on the growing wildlife industry. A wide spectrum of zoonotic diseases was confirmed in both livestock and wildlife species, with rabies and anthrax cases being over-represented and also showing the widest species distribution. Whilst vaccination and ante-mortem inspection against these diseases may curb infected livestock species from entering the human food chain, such practices are difficult to implement in free-ranging wildlife species. In this context, there is a need to improve existing control measures and/or develop novel and better interventional strategies to reduce the threat of this re-emerging global problem. This review provides the basis for initiating a multidisciplinary evidence-based approach to control zoonoses in countries with thriving wildlife and game farming.

  6. Comparative Serum Fatty Acid Profiles of Captive and Free-Ranging Cheetahs (Acinonyx jubatus) in Namibia

    Science.gov (United States)

    Wachter, Bettina; Heinrich, Sonja K.; Reyers, Fred; Mienie, Lodewyk J.

    2016-01-01

    Cheetahs (Acinonyx jubatus) are highly specialised large felids, currently listed as vulnerable on the IUCN red data list. In captivity, they are known to suffer from a range of chronic non-infectious diseases. Although low heterozygosity and the stress of captivity have been suggested as possible causal factors, recent studies have started to focus on the contribution of potential dietary factors in the pathogenesis of these diseases. Fatty acids are an important component of the diet, not only providing a source of metabolisable energy, but serving other important functions in hormone production, cellular signalling as well as providing structural components in biological membranes. To develop a better understanding of lipid metabolism in cheetahs, we compared the total serum fatty acid profiles of 35 captive cheetahs to those of 43 free-ranging individuals in Namibia using gas chromatography-mass spectrometry. The unsaturated fatty acid concentrations differed most remarkably between the groups, with all of the polyunsaturated and monounsaturated fatty acids, except arachidonic acid and hypogeic acid, detected at significantly lower concentrations in the serum of the free-ranging animals. The influence of age and sex on the individual fatty acid concentrations was less notable. This study represents the first evaluation of the serum fatty acids of free-ranging cheetahs, providing critical information on the normal fatty acid profiles of free-living, healthy individuals of this species. The results raise several important questions about the potential impact of dietary fatty acid composition on the health of cheetahs in captivity. PMID:27992457

  7. Comparative Serum Fatty Acid Profiles of Captive and Free-Ranging Cheetahs (Acinonyx jubatus) in Namibia.

    Science.gov (United States)

    Tordiffe, Adrian S W; Wachter, Bettina; Heinrich, Sonja K; Reyers, Fred; Mienie, Lodewyk J

    2016-01-01

    Cheetahs (Acinonyx jubatus) are highly specialised large felids, currently listed as vulnerable on the IUCN red data list. In captivity, they are known to suffer from a range of chronic non-infectious diseases. Although low heterozygosity and the stress of captivity have been suggested as possible causal factors, recent studies have started to focus on the contribution of potential dietary factors in the pathogenesis of these diseases. Fatty acids are an important component of the diet, not only providing a source of metabolisable energy, but serving other important functions in hormone production, cellular signalling as well as providing structural components in biological membranes. To develop a better understanding of lipid metabolism in cheetahs, we compared the total serum fatty acid profiles of 35 captive cheetahs to those of 43 free-ranging individuals in Namibia using gas chromatography-mass spectrometry. The unsaturated fatty acid concentrations differed most remarkably between the groups, with all of the polyunsaturated and monounsaturated fatty acids, except arachidonic acid and hypogeic acid, detected at significantly lower concentrations in the serum of the free-ranging animals. The influence of age and sex on the individual fatty acid concentrations was less notable. This study represents the first evaluation of the serum fatty acids of free-ranging cheetahs, providing critical information on the normal fatty acid profiles of free-living, healthy individuals of this species. The results raise several important questions about the potential impact of dietary fatty acid composition on the health of cheetahs in captivity.

  8. Size-Frequency Distribution of Small Lunar Craters: Widening with Degradation and Crater Lifetime

    Science.gov (United States)

    Ivanov, B. A.

    2018-01-01

    The review and new measurements are presented for depth/diameter ratio and slope angle evolution during small ( D model. The uncertainty of crater retention age due to crater degradational widening is estimated. The collected and analyzed data are discussed to be used in the future updating of mechanical models for lunar crater aging.

  9. "We Are Now Free to Speak": Qualitative Evaluation of an Education and Empowerment Training for HIV Patients in Namibia.

    Directory of Open Access Journals (Sweden)

    Ellen W MacLachlan

    Full Text Available Although numerous studies provide evidence that active patient engagement with health care providers improves critical outcomes such as medication adherence, very few of these have been done in low resource settings. In Namibia, patient education and empowerment trainings were conducted in four antiretroviral (ART clinics to increase patient engagement during patient-provider interactions. This qualitative study supplements findings from a randomized controlled trial, by analyzing data from 10 in-depth patient interviews and 94 training evaluation forms. A blended approach of deductive and inductive coding was used to understand training impact. Findings indicated the trainings increased patients' self-efficacy through a combination of improved HIV-related knowledge, greater communication skills and enhanced ability to overcome complex psychosocial barriers, such as fear of speaking up to providers. This study suggests patient empowerment training may be a powerful method to engage HIV patients in their own care and treatment.

  10. Turbulent flow over craters on Mars: Vorticity dynamics reveal aeolian excavation mechanism

    Science.gov (United States)

    Anderson, William; Day, Mackenzie

    2017-10-01

    Impact craters are scattered across Mars. These craters exhibit geometric self-similarity over a spectrum of diameters, ranging from tens to thousands of kilometers. The late Noachian-early Hesperian boundary marks a dramatic shift in the role of mid-latitude craters, from depocenter sedimentary basins to aeolian source areas. At present day, many craters contain prominent layered sedimentary mounds with maximum elevations comparable to the rim height. The mounds are remnants of Noachian deposition and are surrounded by a radial moat. Large-eddy simulation has been used to model turbulent flows over synthetic craterlike geometries. Geometric attributes of the craters and the aloft flow have been carefully matched to resemble ambient conditions in the atmospheric boundary layer of Mars. Vorticity dynamics analysis within the crater basin reveals the presence of counterrotating helical vortices, verifying the efficacy of deflationary models put forth recently by Bennett and Bell [K. Bennett and J. Bell, Icarus 264, 331 (2016)], 10.1016/j.icarus.2015.09.041 and Day et al. [M. Day et al., Geophys. Res. Lett. 43, 2473 (2016)], 10.1002/2016GL068011. We show how these helical counterrotating vortices spiral around the outer rim, gradually deflating the moat and carving the mound; excavation occurs faster on the upwind side, explaining the radial eccentricity of the mounds relative to the surrounding crater basin.

  11. Turbulent flow over craters on Mars: Vorticity dynamics reveal aeolian excavation mechanism.

    Science.gov (United States)

    Anderson, William; Day, Mackenzie

    2017-10-01

    Impact craters are scattered across Mars. These craters exhibit geometric self-similarity over a spectrum of diameters, ranging from tens to thousands of kilometers. The late Noachian-early Hesperian boundary marks a dramatic shift in the role of mid-latitude craters, from depocenter sedimentary basins to aeolian source areas. At present day, many craters contain prominent layered sedimentary mounds with maximum elevations comparable to the rim height. The mounds are remnants of Noachian deposition and are surrounded by a radial moat. Large-eddy simulation has been used to model turbulent flows over synthetic craterlike geometries. Geometric attributes of the craters and the aloft flow have been carefully matched to resemble ambient conditions in the atmospheric boundary layer of Mars. Vorticity dynamics analysis within the crater basin reveals the presence of counterrotating helical vortices, verifying the efficacy of deflationary models put forth recently by Bennett and Bell [K. Bennett and J. Bell, Icarus 264, 331 (2016)]ICRSA50019-103510.1016/j.icarus.2015.09.041 and Day et al. [M. Day et al., Geophys. Res. Lett. 43, 2473 (2016)]GPRLAJ0094-827610.1002/2016GL068011. We show how these helical counterrotating vortices spiral around the outer rim, gradually deflating the moat and carving the mound; excavation occurs faster on the upwind side, explaining the radial eccentricity of the mounds relative to the surrounding crater basin.

  12. Stratigraphy and Evolution of Delta Channel Deposits, Jezero Crater, Mars

    Science.gov (United States)

    Goudge, T. A.; Mohrig, D.; Cardenas, B. T.; Hughes, C. M.; Fassett, C. I.

    2017-01-01

    The Jezero impact crater hosted an open-basin lake that was active during the valley network forming era on early Mars. This basin contains a well exposed delta deposit at the mouth of the western inlet valley. The fluvial stratigraphy of this deposit provides a record of the channels that built the delta over time. Here we describe observations of the stratigraphy of the channel deposits of the Jezero western delta to help reconstruct its evolution.

  13. Cheetahs (Acinonyx jubatus running the gauntlet: an evaluation of translocations into free-range environments in Namibia

    Directory of Open Access Journals (Sweden)

    Florian J. Weise

    2015-10-01

    Full Text Available Following dramatic range and population declines, the cheetah is Africa’s most endangered large felid. In Namibia, private land managers still trap cheetahs but increasingly consider moving animals instead of killing them. Across Africa, managers have translocated perceived conflict carnivores for decades, but rarely evaluated their actions. We analyse the outcomes of 15 cheetah translocations (for 23 adults and 10 dependent offspring into free-range environments in Namibia. We released cheetahs at an average distance of 419.6 km ± 216.1 km SD (range: 71–816 km after captive periods ranging from 1–1,184 days (350.6 days ± 439.0 days SD. An individual’s ability to survive the first year predominantly determined the overall translocation success of 40%. Post-release conflict and homing had less impact on success. Cheetah survival was lowest in the first three months after release. Human persecution (50% of deaths and spotted hyaenas (29% of deaths had the highest effect on survival. The degree of habituation to humans acquired during captivity significantly influenced chances of survival. Cheetahs surviving the initial post-release period (∼90 days often settled into ranges and females reproduced successfully. However, all individuals exhibited extensive movements, frequently roaming >4,000 km2 in the first six months after release (with a maximum of 19,743 km2 in 112 days, resulting in low release site fidelity. Soft release and larger recipient area size did not improve site fidelity. Based on these outcomes, we evaluated which unfenced conservation areas in Namibia could potentially receive cheetahs. We found that there are currently few public and/or private reserves large enough to contain the movement profiles we observed in this study. This suggests that most translocations will result in cheetahs re-entering farmlands where they face a high risk of persecution. In conclusion, translocations into unconfined areas can

  14. Cheetahs (Acinonyx jubatus) running the gauntlet: an evaluation of translocations into free-range environments in Namibia

    Science.gov (United States)

    Lemeris, Joseph R.; Munro, Stuart J.; Bowden, Andrew; Venter, Cicelia; van Vuuren, Marlice; van Vuuren, Rudie J.

    2015-01-01

    Following dramatic range and population declines, the cheetah is Africa’s most endangered large felid. In Namibia, private land managers still trap cheetahs but increasingly consider moving animals instead of killing them. Across Africa, managers have translocated perceived conflict carnivores for decades, but rarely evaluated their actions. We analyse the outcomes of 15 cheetah translocations (for 23 adults and 10 dependent offspring) into free-range environments in Namibia. We released cheetahs at an average distance of 419.6 km ± 216.1 km SD (range: 71–816 km) after captive periods ranging from 1–1,184 days (350.6 days ± 439.0 days SD). An individual’s ability to survive the first year predominantly determined the overall translocation success of 40%. Post-release conflict and homing had less impact on success. Cheetah survival was lowest in the first three months after release. Human persecution (50% of deaths) and spotted hyaenas (29% of deaths) had the highest effect on survival. The degree of habituation to humans acquired during captivity significantly influenced chances of survival. Cheetahs surviving the initial post-release period (∼90 days) often settled into ranges and females reproduced successfully. However, all individuals exhibited extensive movements, frequently roaming >4,000 km2 in the first six months after release (with a maximum of 19,743 km2 in 112 days), resulting in low release site fidelity. Soft release and larger recipient area size did not improve site fidelity. Based on these outcomes, we evaluated which unfenced conservation areas in Namibia could potentially receive cheetahs. We found that there are currently few public and/or private reserves large enough to contain the movement profiles we observed in this study. This suggests that most translocations will result in cheetahs re-entering farmlands where they face a high risk of persecution. In conclusion, translocations into unconfined areas can successfully conserve

  15. Radioactive Seepage through Groundwater Flow from the Uranium Mines, Namibia

    Directory of Open Access Journals (Sweden)

    Tamiru Abiye

    2017-02-01

    Full Text Available The study focused on the seepage of uranium from unlined tailing dams into the alluvial aquifer in the Gawib River floodplain in Namibia where the region solely relies on groundwater for its economic activities as a result of arid climatic condition. The study reviewed previous works besides water sample collection and analyses for major ions, metals and environmental isotopes in addition to field tests on physico-chemical parameters (pH, Electrical Conductivity, Redox and T. Estimation of seepage velocity (true velocity of groundwater flow has been conducted in order to understand the extent of radioactive plume transport. The hydrochemistry, stable isotopes and tritium results show that there is uranium contamination from the unlined uranium tailings in the Gawib shallow aquifer system which suggests high permeability of the alluvial aquifer facilitating groundwater flow in the arid region. The radioactive contaminants could spread into the deeper aquifer system through the major structures such as joints and faults. The contamination plume could also spread downstream into the Swakop River unless serious interventions are employed. There is also a very high risk of the plume to reach the Atlantic Ocean through seasonal flash floods that occurs in the area.

  16. Responsible investment in a developing nation. Roessing in Namibia

    International Nuclear Information System (INIS)

    Johnson, C.

    1997-01-01

    Roessing Uranium Ltd. operates the world's largest open-cast uranium ore mine near the mountain bearing the same name. After extensive prospection and exploration, production was started in 1976. The open-cast mining areas is 3000 m x 1000 m; the deepest bench is situated 250 m underneath the surface level (576 m above sea level); plans envisage working to a depth of 500 m. Benches are prepared at a distance of 15 m. After sales had picked up in recent years, a change was made to operation in three shifts on seven days a week. An average of 350,000 t of rock is blasted once a week, removed by power shovels, and carried off on heavy duty trucks. As a result of the low uranium content of the low-grade ore there is no need for sophisticated radiation protection measures. Yet, Roessing puts great emphasis on safety, which is monitored continuously by national and international independent expert organizations. Personnel are recruited chiefly from Mamibia. The mining school founded by the compancy was donated to the government as a foundation. Roessing has made all provisions necessary to ensure that Namibia can maintain its position among the uranium supplier countries also in the future. (orig.) [de

  17. Marine sources influence fog bioaerosol composition in Namibia and Maine

    Science.gov (United States)

    Evans, S. E.; Dueker, E.; Logan, J. R. V.; Weathers, K. C.

    2017-12-01

    Organic aerosol particles act as condensation nuclei for fogs and clouds (CCN) and are main determinants of fog evolution, chemical processing, and overall aerosol-fog-cloud interactions. Recent work has confirmed the presence of marine bioaerosols, but little is known about their sources, transport, taxonomic diversity or viability. The few studies that have characterized bioaerosols in fog have been limited to culture-based approaches that capture only a fraction of microbial diversity. We characterized fungal and bacterial communities in the fog in two iconic fog systems, the Coast of Maine (USA) and the Namib Desert (Namibia). The biology of fog in both systems was diverse and distinct, by geography, from dry aerosols, and from local sources. The local environment had a dominant influence on fog in both the Namib and Maine; in particular, the biology of fog in Maine, which was collected near the coast, was more similar to microbial communities from the ocean surface. In both systems, differences between pre- and post-fog aerosol communities suggest that fog events can significantly alter microbial aerosol diversity and composition. This insight into the microbial composition of fog indicates that its origin and frequency has the potential to influence the number and diversity of microorganisms that settle in a given environment, and the composition of microbial aerosol communities in ambient or clear conditions. Here we suggest that fog microbes can possess specific traits that enhance nucleation, altering the transport and deposition of marine- and soil-derived organic matter in terrestrial systems.

  18. Coal prospects in Botswana, Mozambique, Zambia, Zimbabwe and Namibia

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2013-12-01

    Increasing demand for coal in Asia is stimulating interest in the potentially large coal resources in Southern African countries such as Botswana, Mozambique, Zambia, Zimbabwe and Namibia. These countries have been slow to utilise their coal as local demand has been limited and the means to export coal has been inadequate. The governments in these regions are now recognising coal as a strategically important commodity, capable of earning foreign revenue but also adding value to the economy by generating much needed electricity. This report looks in turn at the role of coal in the energy economies of each of these countries. As in most emerging economies, the provision of a reliable and cost-effective supply of electricity to industries and people is essential for economic growth and the welfare of communities. Demand for Africa's mineral commodities such as diamonds and copper is driving a massive need for electricity and coal will play a major role. Not only does the mining industry need power, but with these growing industries come communities and commerce which are also in need of energy.

  19. Reciprocity on Demand : Sharing and Exchanging Food in Northwestern Namibia.

    Science.gov (United States)

    Schnegg, Michael

    2015-09-01

    Two competing models concerning food transfers prominent in the anthropological literature conceptualize such transfers either as sharing or as exchange. Sharing is understood as situational transactions formed through demands and unconditional giving, whereas reciprocal exchange is understood in terms of networking and keeping score. I propose that the picture is more complicated than these classifications suggests. Drawing on data collected in Northwestern Namibia, I show that sharing and reciprocal exchange are dynamically interrelated in actual food transfers. As a local norm, people can demand food from anyone, and they are typically given food in response to a demand. However, in practice, food transfer networks emerge (N = 62) that are highly reciprocal and fit the exchange model much better. Although the sharing norm makes no restrictions on whom to ask, in practice people often turn to their neighbors. Interpersonal dynamics account for why some of those ties become strongly reciprocal and others do not. Under these circumstances, unconditional sharing, a norm that has been viewed as an alternative to exchange, can lead to reciprocity via reciprocity on demand.

  20. Empowering Adult Education in Namibia and South Africa during and after Apartheid

    Science.gov (United States)

    Hopfer, Christiane

    1997-01-01

    After more than 40 years of education for Apartheid, the development of empowering adult education with the formerly disadvantaged population groups is one of the major challenges for the democratically elected governments in South Africa and Namibia. One of the strongest forces that sustained Apartheid in Namibia until 1990, and in South Africa until 1994, was an education system with different schools and resources for the different population groups. Despite the strict implementation of the Bantu Education System by the white government, some groups of people could still organise alternative education projects aiming at participants' gaining more control over their own lifes. Groups of women in the Western Cape initiated autonomous pre-school projects and took part in in-service training for pre-school teachers in the 1980s. A similar process took place with adult literacy learners in the National Literacy Programme in Namibia.

  1. Guest editorial: Industrial Engineering in Namibia - A personal and preliminary view

    Directory of Open Access Journals (Sweden)

    Roy Snaddon

    2012-01-01

    Full Text Available While Namibia is a Republic with just over two thirds the geographical area of South Africa, its population is only 2.3 million (under 5 percent of that in South Africa. Its estimated production (measured by GDP is $ 9.4billion (US as compared with $ 287billion (US for South Africa (just over 3 percent making it less wealthy per person than South Africa. As a small economy in Southern Africa many people may say that Industrial Engineering in Namibia does not exist. They are incorrect as Industrial Engineers do “the integration of resources and processes into cohesive strategies, structures and systems for the effective and efficient production of quality goods and services” (Sperotto 19941. That includes all who start and run the wealth creating organisations including those in Namibia.

  2. Changes in abundance and nature of microimpact craters on the surfaces of Australasian microtektites with distance from the proposed source crater location

    Digital Repository Service at National Institute of Oceanography (India)

    ShyamPrasad, M.; Roy, S.K.; Gupta, A.

    of the craters are of erosive type (Fig. 2), i.e., those which contain a central pit which is surrounded by radial and concentric cracks, indicative of high velocity impacts (Hörz et al., 1971). This could be misleading, as observed in our earlier studies... of very small particles at high relative velocities. This location also has 9    the highest spatial density of impacts, i.e., it contains 230 micro-craters/cm 2 of the ocean floor (Table 2). AAS 22/8 (4052 km): Location : 07 0 05.289’S & 78 0...

  3. Technical problems and future cratering experiments

    Energy Technology Data Exchange (ETDEWEB)

    Knox, J B [Lawrence Radiation Laboratory, Livermore, CA (United States)

    1969-07-01

    This paper reviews some of the key technical problems that remain to be solved in nuclear cratering technology. These include: (1) developing a broader understanding of the effects that material properties and water content of the earth materials around the shot have on cratering behavior, (2) extending the experimental investigation of retarc formation to include intermediate yields and various materials, and (3) improving our ability to predict the escape of radioactive material to the atmosphere to form the cloud source responsible for fallout. The formation processes of ejecta craters, retarcs, and subsidence craters are described in the light of our present understanding, and the major gaps in our understanding are indicated. Methods of calculating crater and retarc formation are discussed, with particular reference to the input information needed. Methods for calculating fallout are presented, and their shortcomings are discussed. A preliminary analysis of the safety factors associated with the presently proposed nuclear excavation concepts is presented. (author)

  4. Technical problems and future cratering experiments

    International Nuclear Information System (INIS)

    Knox, J.B.

    1969-01-01

    This paper reviews some of the key technical problems that remain to be solved in nuclear cratering technology. These include: (1) developing a broader understanding of the effects that material properties and water content of the earth materials around the shot have on cratering behavior, (2) extending the experimental investigation of retarc formation to include intermediate yields and various materials, and (3) improving our ability to predict the escape of radioactive material to the atmosphere to form the cloud source responsible for fallout. The formation processes of ejecta craters, retarcs, and subsidence craters are described in the light of our present understanding, and the major gaps in our understanding are indicated. Methods of calculating crater and retarc formation are discussed, with particular reference to the input information needed. Methods for calculating fallout are presented, and their shortcomings are discussed. A preliminary analysis of the safety factors associated with the presently proposed nuclear excavation concepts is presented. (author)

  5. Remote Sensing Observations and Numerical Simulation for Martian Layered Ejecta Craters

    Science.gov (United States)

    Li, L.; Yue, Z.; Zhang, C.; Li, D.

    2018-04-01

    To understand past Martian climates, it is important to know the distribution and nature of water ice on Mars. Impact craters are widely used ubiquitous indicators for the presence of subsurface water or ice on Mars. Remote sensing observations and numerical simulation are powerful tools for investigating morphological and topographic features on planetary surfaces, and we can use the morphology of layered ejecta craters and hydrocode modeling to constrain possible layering and impact environments. The approach of this work consists of three stages. Firstly, the morphological characteristics of the Martian layered ejecta craters are performed based on Martian images and DEM data. Secondly, numerical modeling layered ejecta are performed through the hydrocode iSALE (impact-SALE). We present hydrocode modeling of impacts onto targets with a single icy layer within an otherwise uniform basalt crust to quantify the effects of subsurface H2O on observable layered ejecta morphologies. The model setup is based on a layered target made up of a regolithic layer (described by the basalt ANEOS), on top an ice layer (described by ANEOS equation of H2O ice), in turn on top of an underlying basaltic crust. The bolide is a 0.8 km diameter basaltic asteroid hitting the Martian surface vertically at a velocity of 12.8 km/s. Finally, the numerical results are compared with the MOLA DEM profile in order to analyze the formation mechanism of Martian layered ejecta craters. Our simulations suggest that the presence of an icy layer significantly modifies the cratering mechanics, and many of the unusual features of SLE craters may be explained by the presence of icy layers. Impact cratering on icy satellites is significantly affected by the presence of subsurface H2O.

  6. Research and application of AMT method in Happiness valley district in Namibia

    International Nuclear Information System (INIS)

    Yu Xiang; Zhang Ruliang; Yao Shancong; Fan Honghai; Wang Shengyun

    2013-01-01

    There are great challenges and difficulties in uranium geology work because of large area grass covered land and few outcrops in Happiness valley district in Namibia. To overcome the problems above, AMT method is undertaken to carry out profile investigation. After finding out electric parameters, different lithologic interfaces were divided, two fracture zones and one anticline structure were, this works laid the ground for the exploration of uranium deposit in Namibia and shew that AMT method is an effective one in finding underground structures. (authors)

  7. Redox stratification of an ancient lake in Gale crater, Mars.

    Science.gov (United States)

    Hurowitz, J A; Grotzinger, J P; Fischer, W W; McLennan, S M; Milliken, R E; Stein, N; Vasavada, A R; Blake, D F; Dehouck, E; Eigenbrode, J L; Fairén, A G; Frydenvang, J; Gellert, R; Grant, J A; Gupta, S; Herkenhoff, K E; Ming, D W; Rampe, E B; Schmidt, M E; Siebach, K L; Stack-Morgan, K; Sumner, D Y; Wiens, R C

    2017-06-02

    In 2012, NASA's Curiosity rover landed on Mars to assess its potential as a habitat for past life and investigate the paleoclimate record preserved by sedimentary rocks inside the ~150-kilometer-diameter Gale impact crater. Geological reconstructions from Curiosity rover data have revealed an ancient, habitable lake environment fed by rivers draining into the crater. We synthesize geochemical and mineralogical data from lake-bed mudstones collected during the first 1300 martian solar days of rover operations in Gale. We present evidence for lake redox stratification, established by depth-dependent variations in atmospheric oxidant and dissolved-solute concentrations. Paleoclimate proxy data indicate that a transition from colder to warmer climate conditions is preserved in the stratigraphy. Finally, a late phase of geochemical modification by saline fluids is recognized. Copyright © 2017, American Association for the Advancement of Science.

  8. Sounding Cratonic Fill in Small Buried Craters Using Ground Penetrating Radar: Analog Study to the Martian Case

    OpenAIRE

    Heggy , Essam; Paillou , Philippe

    2006-01-01

    We report results from a 270 MHz GPR survey performed on a recently discovered impact field in the southwestern Egyptian desert. The investigation suggests the ability of radar techniques to detect small-buried craters and probe their filling

  9. El conjunto rupestre de Otjompaue Sud, Africa del Sudoeste (Namibia

    Directory of Open Access Journals (Sweden)

    Ramón VIÑAS

    2009-10-01

    Full Text Available RESUMEN: La campaña para el estudio del arte rupestre en el Macizo del Erongo (Africa del Sudoeste, Namibia, se desarrolló en 1976 en las zonas de las granjas de Etemba, Anibib y Omandumba West y en el sistema montañoso del Khomas Hochland: Otjompaue Sud, Onduno y Hochfelds. En esta ultima region, objeto de este trabajo, se catalogaron 14 abrigos con pinturas, la mayoría de los cuales situados en la granja de Otjompaue Sud. El arte rupestre de esta zona está en vías de desaparición a causa de la alteración de las losas que forman los abrigos, a pesar de ello se han podido verificar escenas de caza, lucha enfermedad o vejez, pastoreo y danza, junto a grupos de animales salvajes y domésticos, realizados en un estilo naturalista y combinando a menudo dos colores, blanco y rojo, en una misma figura. La falta de trabajos arqueológicos hace prácticamente imposible datar las pinturas aunque parece intuirse una cronología del período Wilton con cerámica, es decir, dentro del primer milenio a. C.RÉSUMÉ: La campagne pour l'étude de l'art rupestre aux montagnes de l'Erongo (Afrique du Sudouest, Namibia, fut réalisée en 1976 dans les terrains des fermes d'Etemba, Anibib et Omandumba West et dans le système montagneux du Khomas Hochland: des fermes d'Otjompaue Sud, Onduno et Hochfelds. Dans cette dernière région du Khomas Hochland on a catalogué 14 abris contenant des peintures rupestres, dont la plupart ont été localisées dans la ferme d'Otjompaue Sud. L'art rupestre de cette zone est en train de disparaître à cause de la grave altération des dalles qui forment les abris. Malgré tout, on a vérifié l'existence de scènes de chasse, lutte, pasteurs, danse, maladie ou vieillesse, auprès d'ensembles d'animaux sauvages et domestiques, réalisés dans un style naturaliste et combinant souvent dans une même figure la couleur blanche et rouge. La datation de ces peintures est presque impossible pour le manque d'études arch

  10. Distribution and molecular evolution of bacillus anthracis genotypes in Namibia.

    Directory of Open Access Journals (Sweden)

    Wolfgang Beyer

    Full Text Available The recent development of genetic markers for Bacillus anthracis has made it possible to monitor the spread and distribution of this pathogen during and between anthrax outbreaks. In Namibia, anthrax outbreaks occur annually in the Etosha National Park (ENP and on private game and livestock farms. We genotyped 384 B. anthracis isolates collected between 1983-2010 to identify the possible epidemiological correlations of anthrax outbreaks within and outside the ENP and to analyze genetic relationships between isolates from domestic and wild animals. The isolates came from 20 animal species and from the environment and were genotyped using a 31-marker multi-locus-VNTR-analysis (MLVA and, in part, by twelve single nucleotide polymorphism (SNP markers and four single nucleotide repeat (SNR markers. A total of 37 genotypes (GT were identified by MLVA, belonging to four SNP-groups. All GTs belonged to the A-branch in the cluster- and SNP-analyses. Thirteen GTs were found only outside the ENP, 18 only within the ENP and 6 both inside and outside. Genetic distances between isolates increased with increasing time between isolations. However, genetic distance between isolates at the beginning and end of the study period was relatively small, indicating that while the majority of GTs were only found sporadically, three genetically close GTs, accounting for more than four fifths of all the ENP isolates, appeared dominant throughout the study period. Genetic distances among isolates were significantly greater for isolates from different host species, but this effect was small, suggesting that while species-specific ecological factors may affect exposure processes, transmission cycles in different host species are still highly interrelated. The MLVA data were further used to establish a model of the probable evolution of GTs within the endemic region of the ENP. SNR-analysis was helpful in correlating an isolate with its source but did not elucidate

  11. Wood chip production technology and costs for fuel in Namibia

    Energy Technology Data Exchange (ETDEWEB)

    Leinonen, A.

    2007-12-15

    This work has been done in the project where the main target is to evaluate the technology and economy to use bush biomass for power production in Namibia. The project has been financed by the Ministry for Foreign Affairs of Finland and the Ministry of Agriculture, Water and Forestry of the Republic of Namibia. The target of this study is to calculate the production costs of bush chips at the power plant using the current production technology and to look possibilities to develop production technology in order to mechanize production technology and to decrease the production costs. The wood production costs are used in feasibility studies, in which the technology and economy of utilization of wood chips for power generation in 5, 10 and 20 MW electric power plants and for power generation in Van Eck coal fired power plant in Windhoek are evaluated. Field tests were made at Cheetah Conservation Farm (CCF) in Otjiwarongo region. CCF is producing wood chips for briquette factory in Otjiwarongo. In the field tests it has been gathered information about this CCF semi-mechanized wood chip production technology. Also new machines for bush biomass chip production have been tested. A new mechanized production chain has been designed on the basis of this information. The production costs for the CCF semi-mechanized and the new production chain have been calculated. The target in the moisture content to produce wood chips for energy is 20 w-%. In the semi-mechanized wood chip production chain the work is done partly manually, and the supply chain is organized into crews of 4.8 men. The production chain consists of manual felling and compiling, drying, chipping with mobile chipper and manual feeding and road transport by a tractor with two trailers. The CCF production chain works well. The chipping and road transport productivity in the semimechanized production chain is low. New production machines, such as chainsaw, brush cutter, lawn mover type cutter, rotator saw in skid

  12. Saying Goodbye to 'Bonneville' Crater

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] Annotated Image NASA's Mars Exploration Rover Spirit took this panoramic camera image on sol 86 (March 31, 2004) before driving 36 meters (118 feet) on sol 87 toward its future destination, the Columbia Hills. This is probably the last panoramic camera image that Spirit will take from the high rim of 'Bonneville' crater, and provides an excellent view of the ejecta-covered path the rover has journeyed thus far. The lander can be seen toward the upper right of the frame and is approximately 321 meters (1060 feet) away from Spirit's current location. The large hill on the horizon is Grissom Hill. The Colombia Hills, located to the left, are not visible in this image.

  13. In plain sight: the Chesapeake Bay crater ejecta blanket

    Science.gov (United States)

    Griscom, D. L.

    2012-02-01

    The discovery nearly two decades ago of a 90 km-diameter impact crater below the lower Chesapeake Bay has gone unnoted by the general public because to date all published literature on the subject has described it as "buried". To the contrary, evidence is presented here that the so-called "upland deposits" that blanket ∼5000 km2 of the U.S. Middle-Atlantic Coastal Plain (M-ACP) display morphologic, lithologic, and stratigraphic features consistent with their being ejecta from the 35.4 Ma Chesapeake Bay Impact Structure (CBIS) and absolutely inconsistent with the prevailing belief that they are of fluvial origin. Specifically supporting impact origin are the facts that (i) a 95 %-pure iron ore endemic to the upland deposits of southern Maryland, eastern Virginia, and the District of Columbia has previously been proven to be impactoclastic in origin, (ii) this iron ore welds together a small percentage of well-rounded quartzite pebbles and cobbles of the upland deposits into brittle sheets interpretable as "spall plates" created in the interference-zone of the CBIS impact, (iii) the predominantly non-welded upland gravels have long ago been shown to be size sorted with an extreme crater-centric gradient far too large to have been the work of rivers, but well explained as atmospheric size-sorted interference-zone ejecta, (iv) new evidence is provided here that ~60 % of the non-welded quartzite pebbles and cobbles of the (lower lying) gravel member of the upland deposits display planar fractures attributable to interference-zone tensile waves, (v) the (overlying) loam member of the upland deposits is attributable to base-surge-type deposition, (vi) several exotic clasts found in a debris flow topographically below the upland deposits can only be explained as jetting-phase crater ejecta, and (vii) an allogenic granite boulder found among the upland deposits is deduced to have been launched into space and sculpted by hypervelocity air friction during reentry. An

  14. Cratering statistics on asteroids: Methods and perspectives

    Science.gov (United States)

    Chapman, C.

    2014-07-01

    Crater size-frequency distributions (SFDs) on the surfaces of solid-surfaced bodies in the solar system have provided valuable insights about planetary surface processes and about impactor populations since the first spacecraft images were obtained in the 1960s. They can be used to determine relative age differences between surficial units, to obtain absolute model ages if the impactor flux and scaling laws are understood, to assess various endogenic planetary or asteroidal processes that degrade craters or resurface units, as well as assess changes in impactor populations across the solar system and/or with time. The first asteroid SFDs were measured from Galileo images of Gaspra and Ida (cf., Chapman 2002). Despite the superficial simplicity of these studies, they are fraught with many difficulties, including confusion by secondary and/or endogenic cratering and poorly understood aspects of varying target properties (including regoliths, ejecta blankets, and nearly-zero-g rubble piles), widely varying attributes of impactors, and a host of methodological problems including recognizability of degraded craters, which is affected by illumination angle and by the ''personal equations'' of analysts. Indeed, controlled studies (Robbins et al. 2014) demonstrate crater-density differences of a factor of two or more between experienced crater counters. These inherent difficulties have been especially apparent in divergent results for Vesta from different members of the Dawn Science Team (cf. Russell et al. 2013). Indeed, they have been exacerbated by misuse of a widely available tool (Craterstats: hrscview.fu- berlin.de/craterstats.html), which incorrectly computes error bars for proper interpretation of cumulative SFDs, resulting in derived model ages specified to three significant figures and interpretations of statistically insignificant kinks. They are further exacerbated, and for other small-body crater SFDs analyzed by the Berlin group, by stubbornly adopting

  15. Underwater research methods for study of nuclear bomb craters, Enewetak, Marshall Islands

    Science.gov (United States)

    Shinn, E.A.; Halley, R.B.; Kindinger, J.L.; Hudson, J.H.; Slate, R.A.

    1990-01-01

    Three craters, created by the explosion of nuclear fusion devices, were mapped, sampled, core drilled and excavated with airlifts at Enewetak Atoll in the Marshall Islands by using scuba and a research submersible. The craters studied were Mike, Oak, and Koa. Tests took place near sea level at the transition between lithified reef flat and unlithified lagoonal sediments, where water depth ranged from 1 to 4 m. Craters produced by the blasts ranged from 30 to 60 m in depth. The purpose of our study was to determine crater diameter and depth immediately after detonation. Observations of submerged roadways and testing structures and upturned crater rims similar to those characteristic of meteor impacts indicate that the initial, or transient, craters were smaller than their present size. At some later time, while the area was too radioactive for direct examination, the sides of the craters slumped owing to dewatering of under lying pulverized rock. Core drilling of crater margins with a diver-operated hydraulic coring device provided additional data. On the seaward margin of the atoll, opposite Mike, a large portion of the atoll rim approximately the size of a city block had slumped into the deep ocean, leaving a clean vertical rock section more than 400m high. An abundance of aggressive grey reef sharks displaying classic territorial behavior prevented use of scuba at the Mike slump site. The two-person submersible R.V. Delta provided protection and allowed observations down to 300 m. During the 6-week period of study, we made more than 300 scuba and 275 submersible dives. Mapping was with side scan sonar and continuous video sweeps supplemented by tape-recorded verbal descriptions made from within the submersible. A mini-ranger navigation system linked to the submersible allowed plotting of bottom features, depth and sediment type with spatial accuracy to within 2 m.

  16. Atypical pit craters on Mars: new insights from THEMIS, CTX and HiRISE observations

    Science.gov (United States)

    Cushing, Glen; Okubo, Chris H.; Titus, Timothy N.

    2015-01-01

    More than 100 pit craters in the Tharsis region of Mars exhibit morphologies, diameters and thermal behaviors that diverge from the much larger bowl-shaped pit craters that occur in most regions across Mars. These Atypical Pit Craters (APCs) generally have sharp and distinct rims, vertical or overhanging walls that extend down to their floors, surface diameters of ~50-350 m, and high depth-to-diameter (d/D) ratios that are usually greater than 0.3 (which is an upper-range value for impacts and bowl-shaped pit craters), and can exceed values of 1.8. Observations by the Mars Odyssey THermal Emission Imaging System (THEMIS) show that APC floor temperatures are warmer at night, and fluctuate with much lower diurnal amplitudes than nearby surfaces or adjacent bowl-shaped pit craters. Kīlauea volcano, Hawai'i, hosts pit craters that formed through subsurface collapse into active volcanic dikes, resulting in pits that can appear morphologically analogous to either APCs or bowl-shaped pit craters. Partially-drained dikes are sometimes exposed within the lower walls and floors of these terrestrial APC analogs and can form extensive cave systems with unique microclimates. Similar caves in martian pit craters are of great interest for astrobiology. This study uses new observations by the Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX) to refine previous work where seven APCs were described from lower-resolution THEMIS visible-wavelength (VIS) observations. Here, we identify locations of 115 APCs, map their distribution across the Tharsis region, characterize their internal morphologies with high-resolution observations, and discuss possible formation mechanisms.

  17. Empowering Local People through Community-based Resource Monitoring: a Comparison of Brazil and Namibia

    Directory of Open Access Journals (Sweden)

    Pedro de Araujo Lima. Constantino

    2012-12-01

    Full Text Available Biological resource monitoring systems are implemented in many countries and often depend on the participation of local people. It has been suggested that these systems empower local participants while promoting conservation. We reviewed three wildlife monitoring systems in indigenous lands and sustainable development reserves in Brazilian Amazonia and one in Namibian Caprivi conservancies, analyzing the strategies adopted and conditions that facilitated local empowerment, as well as potential impacts on conservation. This provided insights into potential avenues to strengthen empowerment outcomes of monitoring systems in Latin America and Africa. We assessed four dimensions of empowerment at individual and community scales: psychological, social, economic, and political. The conditions that facilitated local empowerment included the value of natural resources, rights to trade and manage resources, political organization of communities, and collaboration by stakeholders. The wide range of strategies to empower local people included intensifying local participation, linking them to local education, feeding information back to communities, purposefully selecting participants, paying for monitoring services, marketing monitored resources, and inserting local people into broader politics. Although communities were socially and politically empowered, the monitoring systems more often promoted individual empowerment. Marketing of natural resources promoted higher economic empowerment in conservancies in Namibia, whereas information dissemination was better in Brazil because of integrated education programs. We suggest that practitioners take advantage of local facilitating conditions to enhance the empowerment of communities, bearing in mind that increasing autonomy to make management decisions may not agree with international conservation goals. Our comparative analysis of cases in Latin America and Africa allows for a greater understanding of the

  18. Rights in Education and Self-Identity: Education and Language of Instruction in Namibia

    Science.gov (United States)

    Chavez, Andres

    2016-01-01

    In 1992, the Ministry of Education and Culture in Namibia created a new language policy for schools that presented the possibility of using English as the sole medium of instruction for students starting in Grade 1. The resulting increase in schools that offer only English instruction has been detrimental to education. In order to improve the…

  19. Declining coastal avifauna at a diamond-mining site in Namibia ...

    African Journals Online (AJOL)

    A review of Namibian shorebird densities over two decades and two additional visits to the coastal diamond-mining areas at Elizabeth Bay, southern Namibia, were undertaken to assess the long-term influence of mining activity on density of shorebirds (Charadrii) and particularly threatened African Black Oystercatchers ...

  20. Natural mortality factors for African White-backed Vultures in Namibia?

    African Journals Online (AJOL)

    2007-09-02

    Sep 2, 2007 ... September 2007. Vulture News 57. 63. Figure 2. Lightning damage to the bark of the above camel thorn tree (photographer: Ann Scott). Figure 1. Carcass of an African White-backed Vulture below a nest in a camel thorn tree in the Kalahari Desert, Namibia (photographer: Ann Scott).

  1. Natural mortality factors for African White-backed Vultures in Namibia?

    African Journals Online (AJOL)

    Natural mortality factors for African White-backed Vultures in Namibia? A Scott, M Scott, P Bridgeford, M Bridgeford. Abstract. No Abstract. Vulture News Vol. 57 2007: pp. 62-64. Full Text: EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT · AJOL African Journals Online.

  2. the history of labour hire in namibia: a lesson for south africa

    African Journals Online (AJOL)

    Administrator

    for longer than 72 hours, they could also be relieved of all the cash that they had on ... temporary employees to the mines in Namibia from 1925 to 1943 and were considered ..... 518 /536. The Court a quo dismissed the application with costs.

  3. Vegetation of the eastern communal conservancies in Namibia: I. Phytosociological descriptions

    Directory of Open Access Journals (Sweden)

    Ben J. Strohbach

    2014-11-01

    Conservation implications: This article described 13 plant associations of the central Kalahari in eastern Namibia, an area hitherto virtually unknown to science. The information presented in this article forms a baseline description, which can be used for future monitoring of the vegetation under communal land use.

  4. Putting it in perspective: designing a 3D visualization to contextualize indigenous knowledge in rural Namibia

    DEFF Research Database (Denmark)

    Jensen, Kasper L; Winschiers-Theophilus, Heike; Rodil, Kasper

    2012-01-01

    As part of a long-term research and co-design project we are creating a 3D visualization interface for an indigenous knowledge (IK) management system with rural dwellers of the Herero tribe in Namibia. Evaluations of earlier prototypes and theories on cultural differences in perception led us...

  5. Evaluating social-ecological aspects of buffer zones at the borders of Etosha National Park, Namibia

    Science.gov (United States)

    Lelani M. Mannetti; Ulrich Zeller; Karen J. Esler

    2015-01-01

    The study aims to investigate the premise that the implementation of a buffer zone around a national park provides opportunities for local communities to become active in the management of such areas. The study focuses on the Etosha National Park in Namibia, where the implementation of a buffer zone has been proposed, since the park fence is a potential barrier for...

  6. Extending connections between land and people digitally: designing with rural Herero communities in Namibia

    CSIR Research Space (South Africa)

    Bidwell, NJ

    2012-06-01

    Full Text Available -1 Heritage and Social Media: Understanding Heritage in Participatory Culture June 2012/Chapter 11 Extending connections between land and people digitally: designing with rural Herero communities in Namibia Bidwell NJ1 and Winschiers-Theophilus H2 1...

  7. Double Star Measurements at the Internationale Amateur Sternwarte (IAS) in Namibia in 2008 and 2009

    Science.gov (United States)

    Anton, Rainer

    2010-04-01

    A 40-cm-Cassegrain telescope in Namibia was used for observing double and multiple systems in the southern sky. Digital images were recorded with a CCD camera at high frame rates via a firewire interface directly in a computer. Measurements of 34 double and multiple systems are presented and compared with literature data. Some noteworthy objects are discussed in more detail.

  8. Double Star Measurements at the Internationale Amateur Sternwarte (IAS) in Namibia in 2009

    Science.gov (United States)

    Anton, Rainer

    2012-01-01

    This paper is a continuation of earlier work published in JDSO in 2010. Using a 40-cm-Cassegrain telescope in Namibia and a fast CCD camera, 87 double and multiple systems were recorded and analyzed with the technique of "lucky imaging". Measurements are compared with literature data. Some noteworthy systems are discussed in more detail.

  9. Factors That Influence the Diffusion Process of Mobile Devices in Higher Education in Botswana and Namibia

    Science.gov (United States)

    Asino, Tutaleni I.

    2015-01-01

    This comparative study uses the Diffusion of Innovation (DoI) theoretical framework to explore factors that influence diffusion of mobile devices in higher education in Botswana and Namibia. The five attributes (Relative Avantage, Compatability, Complexity, Trialability, and Observability) of the persuasion stage, which have been found in previous…

  10. Large sulfur isotope fractionations in Martian sediments at Gale crater

    Science.gov (United States)

    Franz, H. B.; McAdam, A. C.; Ming, D. W.; Freissinet, C.; Mahaffy, P. R.; Eldridge, D. L.; Fischer, W. W.; Grotzinger, J. P.; House, C. H.; Hurowitz, J. A.; McLennan, S. M.; Schwenzer, S. P.; Vaniman, D. T.; Archer, P. D., Jr.; Atreya, S. K.; Conrad, P. G.; Dottin, J. W., III; Eigenbrode, J. L.; Farley, K. A.; Glavin, D. P.; Johnson, S. S.; Knudson, C. A.; Morris, R. V.; Navarro-González, R.; Pavlov, A. A.; Plummer, R.; Rampe, E. B.; Stern, J. C.; Steele, A.; Summons, R. E.; Sutter, B.

    2017-09-01

    Variability in the sulfur isotopic composition in sediments can reflect atmospheric, geologic and biological processes. Evidence for ancient fluvio-lacustrine environments at Gale crater on Mars and a lack of efficient crustal recycling mechanisms on the planet suggests a surface environment that was once warm enough to allow the presence of liquid water, at least for discrete periods of time, and implies a greenhouse effect that may have been influenced by sulfur-bearing volcanic gases. Here we report in situ analyses of the sulfur isotopic compositions of SO2 volatilized from ten sediment samples acquired by NASA’s Curiosity rover along a 13 km traverse of Gale crater. We find large variations in sulfur isotopic composition that exceed those measured for Martian meteorites and show both depletion and enrichment in 34S. Measured values of δ34S range from -47 +/- 14‰ to 28 +/- 7‰, similar to the range typical of terrestrial environments. Although limited geochronological constraints on the stratigraphy traversed by Curiosity are available, we propose that the observed sulfur isotopic signatures at Gale crater can be explained by equilibrium fractionation between sulfate and sulfide in an impact-driven hydrothermal system and atmospheric processing of sulfur-bearing gases during transient warm periods.

  11. Floor-fractured craters on Ceres and implications for interior processes

    Science.gov (United States)

    Buczkowski, Debra; Schenk, Paul M.; Scully, Jennifer E. C.; Park, Ryan; Preusker, Frank; Raymond, Carol; Russell, Christopher T.

    2016-10-01

    Several of the impact craters on Ceres have patterns of fractures on their floors. These fractures appear similar to those found within a class of lunar craters referred to as Floor-Fractured Craters (FFCs) [Schultz, 1976].Lunar FFCs are characterized by anomalously shallow floors cut by radial, concentric, and/or polygonal fractures, and have been classified into crater classes, Types 1 through 6, based on their morphometric properties [Schultz, 1976; Jozwiak et al, 2012, 2015]. Models for their formation have included both floor uplift due to magmatic intrusion below the crater or floor shallowing due to viscous relaxation. However, the observation that the depth versus diameter (d/D) relationship of the FFCs is distinctly shallower than the same association for other lunar craters supports the hypotheses that the floor fractures form due to shallow magmatic intrusion under the crater [Jozwiak et al, 2012, 2015].FFCs have also been identified on Mars [Bamberg et al., 2014]. Martian FFCs exhibit morphological characteristics similar to the lunar FFCs, and analyses suggest that the Martian FCCs also formed due to volcanic activity, although heavily influenced by interactions with groundwater and/or ice.We have cataloged the Ceres FFCs according to the classification scheme designed for the Moon. Large (>50 km) Ceres FFCs are most consistent with Type 1 lunar FFCs, having deep floors, central peaks, wall terraces, and radial and/or concentric fractures. Smaller craters on Ceres are more consistent with Type 4 lunar FFCs, having less-pronounced floor fractures and a v-shaped moats separating the wall scarp from the crater interior.An analysis of the d/D ratio for Ceres craters shows that, like lunar FFCs, the Ceres FFCs are anomalously shallow. This suggests that the fractures on the floor of Ceres FFCs may be due the intrusion of a low-density material below the craters that is uplifting their floors. While on the Moon and Mars the intrusive material is hypothesized

  12. Floor-Fractured Craters on Ceres and Implications for Internal Composition and Processes

    Science.gov (United States)

    Buczkowski, D.; Schenk, P.; Scully, J. E. C.; Park, R. S.; Preusker, F.; Raymond, C. A.; Russell, C. T.

    2016-12-01

    Several of the impact craters on Ceres have patterns of fractures on their floors. These fractures appear similar to those found within a class of lunar craters referred to as Floor-Fractured Craters (FFCs) [1]. Lunar FFCs are characterized by anomalously shallow floors cut by radial, concentric, and/or polygonal fractures, and have been classified into crater classes, Types 1 through 6, based on their morphometric properties [1,2]. Models for their formation have included both floor uplift due to magmatic intrusion below the crater or floor shallowing due to viscous relaxation. However, the observation that the depth versus diameter (d/D) relationship of the FFCs is distinctly shallower than the same association for other lunar craters supports the hypotheses that the floor fractures form due to shallow magmatic intrusion under the crater [2]. We have cataloged the Ceres FFCs according to the classification scheme designed for the Moon. Large (>50 km) Ceres FFCs are most consistent with Type 1 lunar FFCs, having deep floors, central peaks, wall terraces, and radial and/or concentric fractures. Smaller craters on Ceres are more consistent with Type 4 lunar FFCs, having less-pronounced floor fractures and v-shaped moats separating the wall scarp from the crater interior. An analysis of the d/D ratio for Ceres craters shows that, like lunar FFCs, the Ceres FFCs are anomalously shallow. This suggests that the fractures on the floor of Ceres FFCs may be due the intrusion of a low-density material below the craters that is uplifting their floors. While on the Moon the intrusive material is hypothesized to be silicate magma, this is unlikely for Ceres. However, a cryovolcanic extrusive edifice has been identified on Ceres [3], suggesting that cryomagmatic intrusions could be responsible for the formation of the Ceres FFCs. References: [1] Schultz P. (1976) Moon, 15, 241-273 [2] Jozwiak L.M. et al (2015) JGR 117, doi: 10.1029/2012JE004134 [3] Ruesch O. et al (2016

  13. Continued monitoring of aeolian activity within Herschel Crater, Mars

    Science.gov (United States)

    Cardinale, Marco; Pozzobon, Riccardo; Michaels, Timothy; Bourke, Mary C.; Okubo, Chris H.; Chiara Tangari, Anna; Marinangeli, Lucia

    2017-04-01

    In this work, we study a dark dune field on the western side of Herschel crater, a 300 km diameter impact basin located near the Martian equator (14.4°S, 130°E), where the ripple and dune motion reflects the actual atmospheric wind conditions. We develop an integrated analysis using (1) automated ripple mapping that yields ripple orientations and evaluates the spatial variation of actual atmospheric wind conditions within the dunes, (2) an optical cross-correlation that allows us to quantify an average ripple migration rate of 0.42 m per Mars year, and (3) mesoscale climate modeling with which we compare the observed aeolian changes with modeled wind stresses and directions. Our observations are consistent with previous work [1] [2] that detected aeolian activity in the western part of the crater. It also demonstrates that not only are the westerly Herschel dunes movable, but that predominant winds from the north are able to keep the ripples and dunes active within most (if not all) of Herschel crater in the current atmospheric conditions. References: [1] Cardinale, M., Silvestro, S., Vaz, D.A., Michaels, T., Bourke, M.C., Komatsu, G., Marinangeli, L., 2016. Present-day aeolian activity in Herschel Crater, Mars. Icarus 265, 139-148. doi:10.1016/j.icarus.2015.10.022. [2] Runyon, K.D., Bridges, N.T., Ayoub, F., Newman, C.E. and Quade, J.J., 2017. An integrated model for dune morphology and sand fluxes on Mars. Earth and Planetary Science Letters, 457, pp.204-212.

  14. Temperature profiles from Pos Crater Lake

    Science.gov (United States)

    Neshyba, Steve; Fernandez, Walter; Diaz-Andrade, José

    In 1984, we took part in an expedition to measure the temperature field and bathymetry of the acid lake (Figure 1) that has formed in the crater of Poás volcano, Costa Rica, since its last eruption in 1953. Obtaining these data was the first step in a long-range study planned by researchers at the Center for Geophysical Research, University of Costa Rica (San Jose, Costa Rica), and the College of Oceanography, Oregon State University (Corvallis). The study will eventually consider all aspects of fluid behavior in a volcanic lake that is heated or otherwise convectively driven by energy injected at the lake bottom.Evidence of convection is clearly visible on the surface of the Poás lake most of the time. Fumarole activity has been continuous since 1953. Phreatic explosions are quite frequent, varying from weak to strong, and the height of the ejected column varies from 1 to more than 500 m. One immediately useful result of the research would be an estimate of the heat transfer from sources within the conduit to the overlying water column. As far as geophysical fluid behavior goes, we are interested in the turbulent and diffusive processes by which heat and chemical species are transferred. We are especially interested in the impact on the density stratification of the density changes that occur as particulates settle downward through the fluid column. The stratification would otherwise be controlled by the turbulent and diffusive processes driven by thermochemical factors.

  15. Strengthening tactical planning and operational frameworks for vector control: the roadmap for malaria elimination in Namibia.

    Science.gov (United States)

    Chanda, Emmanuel; Ameneshewa, Birkinesh; Angula, Hans A; Iitula, Iitula; Uusiku, Pentrina; Trune, Desta; Islam, Quazi M; Govere, John M

    2015-08-05

    Namibia has made tremendous gains in malaria control and the epidemiological trend of the disease has changed significantly over the past years. In 2010, the country reoriented from the objective of reducing disease morbidity and mortality to the goal of achieving malaria elimination by 2020. This manuscript outlines the processes undertaken in strengthening tactical planning and operational frameworks for vector control to facilitate expeditious malaria elimination in Namibia. The information sources for this study included all available data and accessible archived documentary records on malaria vector control in Namibia. A methodical assessment of published and unpublished documents was conducted via a literature search of online electronic databases, Google Scholar, PubMed and WHO, using a combination of search terms. To attain the goal of elimination in Namibia, systems are being strengthened to identify and clear all infections, and significantly reduce human-mosquito contact. Particularly, consolidating vector control for reducing transmission at the identified malaria foci will be critical for accelerated malaria elimination. Thus, guarding against potential challenges and the need for evidence-based and sustainable vector control instigated the strengthening of strategic frameworks by: adopting the integrated vector management (IVM) strategy; initiating implementation of the global plan for insecticide resistance management (GPIRM); intensifying malaria vector surveillance; improving data collection and reporting systems on DDT; updating the indoor residual spraying (IRS) data collection and reporting tool; and, improving geographical reconnaissance using geographical information system-based satellite imagery. Universal coverage with IRS and long-lasting insecticidal nets, supplemented by larval source management in the context of IVM and guided by vector surveillance coupled with rational operationalization of the GPIRM, will enable expeditious

  16. Combined analysis of 2-D electrical resistivity, seismic refraction and geotechnical investigations for Bukit Bunuh complex crater

    International Nuclear Information System (INIS)

    Azwin, I N; Saad, Rosli; Nordiana, M M; Bery, Andy Anderson; Hidayah, I N E; Saidin, Mokhtar

    2015-01-01

    Interest in studying impact crater on earth has increased tremendously due to its importance in geologic events, earth inhabitant history as well as economic value. The existences of few shock metamorphism and crater morphology evidences are discovered in Bukit Bunuh, Malaysia thus detailed studies are performed using geophysical and geotechnical methods to verify the type of the crater and characteristics accordingly. This paper presents the combined analysis of 2-D electrical resistivity, seismic refraction, geotechnical SPT N value, moisture content and RQD within the study area. Three stages of data acquisition are made starting with regional study followed by detailed study on West side and East side. Bulk resistivity and p-wave seismic velocity were digitized from 2-D resistivity and seismic sections at specific distance and depth for corresponding boreholes and samples taken. Generally, Bukit Bunuh shows the complex crater characteristics. Standard table of bulk resistivity and p-wave seismic velocity against SPT N value, moisture content and RQD are produce according to geological classifications of impact crater; inside crater, rim/slumped terrace and outside crater

  17. Combined analysis of 2-D electrical resistivity, seismic refraction and geotechnical investigations for Bukit Bunuh complex crater

    Science.gov (United States)

    Azwin, I. N.; Saad, Rosli; Saidin, Mokhtar; Nordiana, M. M.; Anderson Bery, Andy; Hidayah, I. N. E.

    2015-01-01

    Interest in studying impact crater on earth has increased tremendously due to its importance in geologic events, earth inhabitant history as well as economic value. The existences of few shock metamorphism and crater morphology evidences are discovered in Bukit Bunuh, Malaysia thus detailed studies are performed using geophysical and geotechnical methods to verify the type of the crater and characteristics accordingly. This paper presents the combined analysis of 2-D electrical resistivity, seismic refraction, geotechnical SPT N value, moisture content and RQD within the study area. Three stages of data acquisition are made starting with regional study followed by detailed study on West side and East side. Bulk resistivity and p-wave seismic velocity were digitized from 2-D resistivity and seismic sections at specific distance and depth for corresponding boreholes and samples taken. Generally, Bukit Bunuh shows the complex crater characteristics. Standard table of bulk resistivity and p-wave seismic velocity against SPT N value, moisture content and RQD are produce according to geological classifications of impact crater; inside crater, rim/slumped terrace and outside crater.

  18. An anthropogenic origin of the "Sirente crater," Abruzzi, Italy

    Science.gov (United States)

    Speranza, Fabio; Sagnotti, Leonardo; Rochette, Pierre

    2004-04-01

    In this paper, we review the recent hypothesis, based mostly on geomorphological features, that a ~130 m-wide sag pond, surrounded by a saddle-shaped rim from the Sirente plain (Abruzzi, Italy), is the first-discovered meteoritic crater of Italy. Sub-circular depressions (hosting ponds), with geomorphological features and size very similar to those exhibited by the main Sirente sag, are exposed in other neighboring intermountain karstic plains from Abruzzi. We have sampled present day soils from these sag ponds and from the Sirente sags (both the main "crater" and some smaller ones, recently interpreted as a crater field) and various Abruzzi paleosols from excavated trenches with an age range encompassing the estimated age of the "Sirente crater." For all samples, we measured the magnetic susceptibility and determined the Ni and Cr contents of selected specimens. The results show that the magnetic susceptibility values and the geochemical composition are similar for all samples (from Sirente and other Abruzzi sags) and are both significantly different from the values reported for soils contaminated by meteoritic dust. No solid evidence pointing at an impact origin exists, besides the circular shape and rim of the main sag. The available observations and data suggest that the "Sirente crater," together with analogous large sags in the Abruzzi intermountain plains, have to be attributed to the historical phenomenon of "transumanza" (seasonal migration of sheep and shepherds), a custom that for centuries characterized the basic social-economical system of the Abruzzi region. Such sags were excavated to provide water for millions of sheep, which spent summers in the Abruzzi karstic high pasture lands, on carbonatic massifs deprived of natural superficial fresh water. Conversely, the distribution of the smaller sags from the Sirente plain correlates with the local pattern of the calcareous bedrock and, together with the characteristics of their internal structure, are

  19. Nuclear cratering on a digital computer

    Energy Technology Data Exchange (ETDEWEB)

    Terhune, R W; Stubbs, T F; Cherry, J T [Lawrence Radiation Laboratory, University of California, Livermore, CA (United States)

    1970-05-01

    Computer programs based on the artificial viscosity method are applied to developing an understanding of the physics of cratering, with emphasis on cratering by nuclear explosives. Two established codes, SOC (spherical symmetry) and TENSOR (cylindrical symmetry), are used to illustrate the effects of variations in the material properties of various media on the cratering processes, namely shock, spall, and gas acceleration. Water content is found to be the most important material property, followed by strength, porosity, and compressibility. Crater profile calculations are presented for Pre-Gondola Charley (20-ton nitromethane detonation in shale) and Sedan (100-kt nuclear detonation in alluvium). Calculations also are presented for three 1-Mt yields in saturated Divide basalt and 1-Mt yield in dry Buckboard basalt, to show crater geometry as a function of the burial depth for large explosive yields. The calculations show, for megaton-level yields, that gas acceleration is the dominate mechanism in determining crater size and depends in turn on the water content in the medium. (author)

  20. Nuclear cratering on a digital computer

    International Nuclear Information System (INIS)

    Terhune, R.W.; Stubbs, T.F.; Cherry, J.T.

    1970-01-01

    Computer programs based on the artificial viscosity method are applied to developing an understanding of the physics of cratering, with emphasis on cratering by nuclear explosives. Two established codes, SOC (spherical symmetry) and TENSOR (cylindrical symmetry), are used to illustrate the effects of variations in the material properties of various media on the cratering processes, namely shock, spall, and gas acceleration. Water content is found to be the most important material property, followed by strength, porosity, and compressibility. Crater profile calculations are presented for Pre-Gondola Charley (20-ton nitromethane detonation in shale) and Sedan (100-kt nuclear detonation in alluvium). Calculations also are presented for three 1-Mt yields in saturated Divide basalt and 1-Mt yield in dry Buckboard basalt, to show crater geometry as a function of the burial depth for large explosive yields. The calculations show, for megaton-level yields, that gas acceleration is the dominate mechanism in determining crater size and depends in turn on the water content in the medium. (author)

  1. Global Distribution of On-Set Diameters of Rampart Ejecta Craters on Mars: Their Implication to the History of Martian Water

    Science.gov (United States)

    Boyce, Joseph M.; Roddy, David J.; Soderblom, Lawrence A.; Hare, Trent

    2000-01-01

    A global map is presented of on-set diameters of rampart craters. These craters are proposed to result from impact into wet targets. This map shows both global latitudinal and regional trends that are consistent with the climate and geologic history of Mars.

  2. Review: Larissa Förster, Postkoloniale Erinnerungslandschaften. Wie Deutsche und Herero in Namibia des Kriegs von 1904 gedenken (2010 Buchbesprechung: Larissa Förster, Postkoloniale Erinnerungslandschaften. Wie Deutsche und Herero in Namibia des Kriegs von 1904 gedenken (2010

    Directory of Open Access Journals (Sweden)

    Reinhart Kößler

    2010-01-01

    Full Text Available Review of the Monograph: Larissa Förster (2010, Postkoloniale Erinnerungslandschaften. Wie Deutsche und Herero in Namibia des Kriegs von 1904 gedenken, Frankfurt am Main & New York: Campus, ISBN 978-3-593-39160-1, 391 pages. Besprechung der Monographie: Larissa Förster (2010, Postkoloniale Erinnerungslandschaften. Wie Deutsche und Herero in Namibia des Kriegs von 1904 gedenken, Frankfurt am Main & New York: Campus, ISBN 978-3-593-39160-1, 391 Seiten.

  3. Implications of the 2015 World Health Organization isoniazid preventive therapy recommendations on tuberculosis prevention efforts in Namibia.

    Science.gov (United States)

    Oloo, Stella Anne

    2016-07-01

    The World Health Organization recently released guidelines recommending 36-month use of isoniazid preventive therapy in adults and adolescents living with HIV in resource-limited settings. Namibia continues to grapple with one of the highest incidences of tuberculosis (TB) worldwide. Implementation of these guidelines requires considerations of TB epidemiology, health infrastructure, programmatic priorities and patient adherence. This article explores the challenges Namibia currently faces in its fight against TB and the implications of the new guidelines on Namibian TB prevention efforts.

  4. Pancam Peek into 'Victoria Crater' (Stereo)

    Science.gov (United States)

    2006-01-01

    [figure removed for brevity, see original site] Left-eye view of a stereo pair for PIA08776 [figure removed for brevity, see original site] Right-eye view of a stereo pair for PIA08776 A drive of about 60 meters (about 200 feet) on the 943rd Martian day, or sol, of Opportunity's exploration of Mars' Meridiani Planum region (Sept. 18, 2006) brought the NASA rover to within about 50 meters (about 160 feet) of the rim of 'Victoria Crater.' This crater has been the mission's long-term destination for the past 21 Earth months. Opportunity reached a location from which the cameras on top of the rover's mast could begin to see into the interior of Victoria. This stereo anaglyph was made from frames taken on sol 943 by the panoramic camera (Pancam) to offer a three-dimensional view when seen through red-blue glasses. It shows the upper portion of interior crater walls facing toward Opportunity from up to about 850 meters (half a mile) away. The amount of vertical relief visible at the top of the interior walls from this angle is about 15 meters (about 50 feet). The exposures were taken through a Pancam filter selecting wavelengths centered on 750 nanometers. Victoria Crater is about five times wider than 'Endurance Crater,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle Crater,' where Opportunity first landed. The great lure of Victoria is the expectation that a thick stack of geological layers will be exposed in the crater walls, potentially several times the thickness that was previously studied at Endurance and therefore, potentially preserving several times the historical record.

  5. Open Access Discovery of alunite in Cross crater, Terra Sirenum, Mars: Evidence for acidic, sulfurous waters

    Science.gov (United States)

    Ehlmann, Bethany L.; Swayze, Gregg A.; Milliken, Ralph E.; Mustard, John F.; Clark, Roger N.; Murchie, Scott L.; Breit, George N.; Wray, James J.; Gondet, Brigitte; Poulet, Francois; Carter, John; Calvin, Wendy M.; Benzel, William M.; Seelos, Kimberly D.

    2016-01-01

    Cross crater is a 65 km impact crater, located in the Noachian highlands of the Terra Sirenum region of Mars (30°S, 158°W), which hosts aluminum phyllosilicate deposits first detected by the Observatoire pour la Minéralogie, L’Eau, les Glaces et l’Activitié (OMEGA) imaging spectrometer on Mars Express. Using high-resolution data from the Mars Reconnaissance Orbiter, we examine Cross crater’s basin-filling sedimentary deposits. Visible/shortwave infrared (VSWIR) spectra from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) show absorptions diagnostic of alunite. Combining spectral data with high-resolution images, we map a large (10 km × 5 km) alunite-bearing deposit in southwest Cross crater, widespread kaolin-bearing sediments with variable amounts of alunite that are layered in <10 m scale beds, and silica- and/or montmorillonite-bearing deposits that occupy topographically lower, heavily fractured units. The secondary minerals are found at elevations ranging from 700 to 1550 m, forming a discontinuous ring along the crater wall beneath darker capping materials. The mineralogy inside Cross crater is different from that of the surrounding terrains and other martian basins, where Fe/Mg-phyllosilicates and Ca/Mg-sulfates are commonly found. Alunite in Cross crater indicates acidic, sulfurous waters at the time of its formation. Waters in Cross crater were likely supplied by regionally upwelling groundwaters as well as through an inlet valley from a small adjacent depression to the east, perhaps occasionally forming a lake or series of shallow playa lakes in the closed basin. Like nearby Columbus crater, Cross crater exhibits evidence for acid sulfate alteration, but the alteration in Cross is more extensive/complete. The large but localized occurrence of alunite suggests a localized, high-volume source of acidic waters or vapors, possibly supplied by sulfurous (H2S- and/or SO2-bearing) waters in contact with a magmatic source, upwelling

  6. Optimizing laser crater enhanced Raman scattering spectroscopy

    Science.gov (United States)

    Lednev, V. N.; Sdvizhenskii, P. A.; Grishin, M. Ya.; Fedorov, A. N.; Khokhlova, O. V.; Oshurko, V. B.; Pershin, S. M.

    2018-05-01

    The laser crater enhanced Raman scattering (LCERS) spectroscopy technique has been systematically studied for chosen sampling strategy and influence of powder material properties on spectra intensity enhancement. The same nanosecond pulsed solid state Nd:YAG laser (532 nm, 10 ns, 0.1-1.5 mJ/pulse) was used for laser crater production and Raman scattering experiments for L-aspartic acid powder. Increased sampling area inside crater cavity is the key factor for Raman signal improvement for the LCERS technique, thus Raman signal enhancement was studied as a function of numerous experimental parameters including lens-to-sample distance, wavelength (532 and 1064 nm) and laser pulse energy utilized for crater production. Combining laser pulses of 1064 and 532 nm wavelengths for crater ablation was shown to be an effective way for additional LCERS signal improvement. Powder material properties (particle size distribution, powder compactness) were demonstrated to affect LCERS measurements with better results achieved for smaller particles and lower compactness.

  7. Cratering efficiency on coarse-grain targets: Implications for the dynamical evolution of asteroid 25143 Itokawa

    Science.gov (United States)

    Tatsumi, Eri; Sugita, Seiji

    2018-01-01

    Remote sensing observations made by the spacecraft Hayabusa provided the first direct evidence of a rubble-pile asteroid: 25143 Itokawa. Itokawa was found to have a surface structure very different from other explored asteroids; covered with coarse pebbles and boulders ranging at least from cm to meter size. The cumulative size distribution of small circular depressions on Itokawa, most of which may be of impact origin, has a significantly shallower slope than that on the Moon; small craters are highly depleted on Itokawa compared to the Moon. This deficiency of small circular depressions and other features, such as clustered fragments and pits on boulders, suggest that the boulders on Itokawa might behave like armor, preventing crater formation: the ;armoring effect;. This might contribute to the low number density of small crater candidates. In this study, the cratering efficiency reduction due to coarse-grained targets was investigated based on impact experiments at velocities ranging from ∼ 70 m/s to ∼ 6 km/s using two vertical gas gun ranges. We propose a scaling law extended for cratering on coarse-grained targets (i.e., target grain size ≳ projectile size). We have found that the crater efficiency reduction is caused by energy dissipation at the collision site where momentum is transferred from the impactor to the first-contact target grain, and that the armoring effect can be classified into three regimes: (1) gravity scaled regime, (2) reduced size crater regime, or (3) no apparent crater regime, depending on the ratio of the impactor size to the target grain size and the ratio of the impactor kinetic energy to the disruption energy of a target grain. We found that the shallow slope of the circular depressions on Itokawa cannot be accounted for by this new scaling law, suggesting that obliteration processes, such as regolith convection and migration, play a greater role in the depletion of circular depressions on Itokawa. Based on the new extended

  8. Experiences and Perceptions of Barriers to Health Services for Elderly in Rural Namibia

    Directory of Open Access Journals (Sweden)

    Gert Van Rooy

    2015-07-01

    Full Text Available We investigate barriers to accessing health facilities (e.g., transportation and cost of services and health service delivery barriers (e.g., timeliness of services scheduling of appointments, language that the literature suggest are operative. Semistructured interviews were utilized with respondents in three purposefully selected regional research sites in Namibia. All questions were translated into local languages. It is found that although many senior citizens appreciate the use of modern health care and are exempted from paying health care consultation fees, they still prefer to use traditional health medicine because of the long distance to health care facilities, which when they decide to travel translates into high transportation costs. Referrals to hospitals become very expensive. There is a need to consider the unique issues (extended family system affecting access to health care for elderly people in Namibia to achieve equitable access to health care services.

  9. Laboratory information management system: an example of international cooperation in Namibia.

    Science.gov (United States)

    Colangeli, Patrizia; Ferrilli, Monica; Quaranta, Fabrizio; Malizia, Elio; Mbulu, Rosa-Stella; Mukete, Esther; Iipumbu, Lukas; Kamhulu, Anna; Tjipura-Zaire, Georgina; Di Francesco, Cesare; Lelli, Rossella; Scacchia, Massimo

    2012-01-01

    The authors describe the project undertaken by the Istituto G. Caporale to provide a laboratory information management system (LIMS) to the Central Veterinary Laboratory (CVL) in Windhoek, Namibia. This robust laboratory management tool satisfies Namibia's information obligations under international quality standard ISO 17025:2005. The Laboratory Information Management System (LIMS) for Africa was designed to collect and manage all necessary information on samples, tests and test results. The system involves the entry of sample data on arrival, as required by Namibian sampling plans, the tracking of samples through the various sections of the CVL, the collection of test results, generation of test reports and monitoring of outbreaks through data interrogation functions, eliminating multiple registrations of the same data on paper records. It is a fundamental component of the Namibian veterinary information system.

  10. The exhibition Namibia-Germany: a shared/divided history. Resistance, violence, memory

    Directory of Open Access Journals (Sweden)

    Clara Himmelheber

    2014-10-01

    Full Text Available The year 2004 was the centenary of the outbreak of a colonial war in former German South West Africa in which thousands of Africans were killed by the colonial power. Although of crucial importance for Namibia, the war had not entered public memory in Germany. The exhibition aimed at presenting colonial history, as well as the contemporary relationships between the two countries, showing a ‘shared’ and a ‘divided’ history. The exhibition created a public debate, which certainly supported the initiative of the German Minister of Economic Co-operation and Development to deliver an apology at the commemoration in August 2004 in Namibia. The article is a post-reflection of one of the co-curators on the exhibition putting it into a larger context and reviewing it concurrently.

  11. Factors that influence attitudes and sexual behavior among constituency youth workers in Oshana Region, Namibia.

    Science.gov (United States)

    Lawoyin, Olusheyi O; Kanthula, Ruth M

    2010-03-01

    This survey was carried out to assess attitudes and behaviour among youth within four constituencies in Oshana region, Namibia and to understand to how certain social and cultural factors inform attitudes and influence sexual behaviour among the population of young people surveyed. Using a structured questionnaire, data were collected from a random sample of eighty young men and women between the ages of 15-30 years from four constituencies in Oshana region. Survey outcomes revealed attitudes and certain factors that are linked to sexual risk behaviour such as multiple sexual partnerships. Outcomes also reveal an influence of established socio-cultural norms on gender dynamics within relationships and a culture of reserve around discussions of sex and sexuality among young people. Stakeholder interventions should be directed towards incorporating approaches that address these factors as part of efforts to curb the incidence of HIV among young people in Namibia.

  12. Atmospheric Tides in Gale Crater, Mars

    Science.gov (United States)

    Guzewich, Scott D,; Newman, C. E; de la Torre Juarez, M.; Wilson, R. J.; Lemmon, M.; Smith, M. D.; Kahanpaa, H.; Harri, A.-M.

    2015-01-01

    Atmospheric tides are the primary source of daily air pressure variation at the surface of Mars. These tides are forced by solar heating of the atmosphere and modulated by the presence of atmospheric dust, topography, and surface albedo and thermal inertia. This results in a complex mix of sun-synchronous and nonsun- synchronous tides propagating both eastward and westward around the planet in periods that are integer fractions of a solar day. The Rover Environmental Monitoring Station on board the Mars Science Laboratory has observed air pressure at a regular cadence for over 1 Mars year and here we analyze and diagnose atmospheric tides in this pressure record. The diurnal tide amplitude varies from 26 to 63 Pa with an average phase of 0424 local true solar time, while the semidiurnal tide amplitude varies from 5 to 20 Pa with an average phase of 0929. We find that both the diurnal and semidiurnal tides in Gale Crater are highly correlated to atmospheric opacity variations at a value of 0.9 and to each other at a value of 0.77, with some key exceptions occurring during regional and local dust storms. We supplement our analysis with MarsWRF general circulation modeling to examine how a local dust storm impacts the diurnal tide in its vicinity. We find that both the diurnal tide amplitude enhancement and regional coverage of notable amplitude enhancement linearly scales with the size of the local dust storm. Our results provide the first long-term record of surface pressure tides near the martian equator.

  13. Crater monitoring through social media observations

    Science.gov (United States)

    Gialampoukidis, I.; Vrochidis, S.; Kompatsiaris, I.

    2017-09-01

    We have collected more than one lunar image per two days from social media observations. Each one of the collected images has been clustered into two main groups of lunar images and an additional cluster is provided (noise) with pictures that have not been assigned to any cluster. The proposed lunar image clustering process provides two classes of lunar pictures, at different zoom levels; the first showing a clear view of craters grouped into one cluster and the second demonstrating a complete view of the Moon at various phases that are correlated with the crawling date. The clustering stage is unsupervised, so new topics can be detected on-the-fly. We have provided additional sources of planetary images using crowdsourcing information, which is associated with metadata such as time, text, location, links to other users and other related posts. This content has crater information that can be fused with other planetary data to enhance crater monitoring.

  14. A concept of row crater enhancement

    International Nuclear Information System (INIS)

    Redpath, B.B.

    1970-01-01

    Linear craters formed by the simultaneous detonation of a row of buried explosives will probably have a wider application than single charges in the explosive excavation of engineering structures. Most cratering experience to date has been with single charges, and an analytical procedure for the design of a row of charges to excavate a crater with a specified configuration has been lacking. There are no digital computer codes having direct application to a row of charges as there are for single charges. This paper derives a simple relationship which can be used to design row charges with some assurance of achieving the desired result and with considerable flexibility in the choice of explosive yield of the individual charges

  15. Mafic Materials in Scott Crater? A Test for Lunar Reconnaissance Orbiter

    Science.gov (United States)

    Cooper, Bonnie L.

    2007-01-01

    Clementine 750 nm and multispectral ratio data, along with Lunar Orbiter and radar data, were used to study the crater Scott in the lunar south polar region. The multispectral data provide evidence for mafic materials, impact melts, anorthositic materials, and a small pyroclastic deposit. High-resolution radar data and Lunar Orbiter photography for this area show differences in color and surface texture that correspond with the locations of the hypothesized mafic and anorthositic areas on the crater floor. This region provides a test case for the upcoming Lunar Reconnaissance Orbiter. Verification of the existence of a mafic deposit at this location is relevant to future lunar resource utilization planning.

  16. Rim Structure, Stratigraphy, and Aqueous Alteration Exposures Along Opportunity Rover's Traverse of the Noachian Endeavour Crater

    Science.gov (United States)

    Crumpler, L.S.; Arvidson, R. E.; Golombek, M.; Grant, J. A.; Jolliff, B. L.; Mittlefehldt, D. W.

    2017-01-01

    The Mars Exploration Rover Opportunity has traversed 10.2 kilometers along segments of the west rim of the 22-kilometer-diameter Noachian Endeavour impact crater as of sol 4608 (01/09/17). The stratigraphy, attitude of units, lithology, and degradation state of bedrock outcrops exposed on the crater rim have been examined in situ and placed in geologic context. Structures within the rim and differences in physical properties of the identified lithologies have played important roles in localizing outcrops bearing evidence of aqueous alteration.

  17. Comment on 'A schematic model of crater modification by gravity' by H. J. Melosh

    International Nuclear Information System (INIS)

    Pike, R.J.

    1983-01-01

    Size-dependent variations in the morphology of impact craters on planets and satellites pose controversial problems. H. J. Melosh has continued to emphasize theoretical analysis in modeling the morphologic transition from simple to complex craters. His latest results [Melosh, 1982] outline a comprehensive hypothesis wherein deep-seated collapse of the transient cavity as a Bingham plastic material to produce central peaks and, seemingly, slump terraces is brought about by acoustic fluidization. However, Melosh's paper also contains inconsistent or ambiguously reported observations and some statements and interpretations that need to be clarified

  18. Lomonosov Crater, Day and Night

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] Released 16 June 2004 This pair of images shows part of Lomonosov Crater. Day/Night Infrared Pairs The image pairs presented focus on a single surface feature as seen in both the daytime and nighttime by the infrared THEMIS camera. The nighttime image (right) has been rotated 180 degrees to place north at the top. Infrared image interpretation Daytime: Infrared images taken during the daytime exhibit both the morphological and thermophysical properties of the surface of Mars. Morphologic details are visible due to the effect of sun-facing slopes receiving more energy than antisun-facing slopes. This creates a warm (bright) slope and cool (dark) slope appearance that mimics the light and shadows of a visible wavelength image. Thermophysical properties are seen in that dust heats up more quickly than rocks. Thus dusty areas are bright and rocky areas are dark. Nighttime: Infrared images taken during the nighttime exhibit only the thermophysical properties of the surface of Mars. The effect of sun-facing versus non-sun-facing energy dissipates quickly at night. Thermophysical effects dominate as different surfaces cool at different rates through the nighttime hours. Rocks cool slowly, and are therefore relatively bright at night (remember that rocks are dark during the day). Dust and other fine grained materials cool very quickly and are dark in nighttime infrared images. Image information: IR instrument. Latitude 64.9, Longitude 350.7 East (9.3 West). 100 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project

  19. Closure plan for Corrective Action Unit 109: U-2bu subsidence crater, Nevada Test Site, Nevada

    International Nuclear Information System (INIS)

    1999-03-01

    The U-2bu subsidence crater, Corrective Action Unit 109, will be closed in accordance with the Resource Conservation and Recovery Act, the Nevada Division of Environmental Protection operational permit, and the Federal Facility Agreement and Consent Order. The U-2bu subsidence crater is located in Area 2 of the Nevada Test Site. It was created in 1971 by an underground nuclear test with the name Miniata. The crater has a diameter of 288 meters (944 feet) and an approximate depth of 35 meters (115 feet). Based on the results of the analyses reported in the site characterization report, the only constituents of concern in the U-2bu subsidence crater include leachable lead and total petroleum hydrocarbons. Closure activities will include the excavation and disposal of impacted soil from the top of the crater. Upon completion of excavation, verification samples will be collected to show that the leachable lead has been removed to concentrations below the regulatory action level. After sample results show that the lead has been removed, the excavated area will be backfilled and a soil flood diversion berm will be constructed as a best management practice. An independent registered professional engineer will certify the site was closed following the approved Closure Plan. Post-closure care is not warranted for this site because closure activities will involve removal of the Resource Conservation and Recovery Act constituents of concern

  20. Closure Plan for Corrective Action Unit 109: U-2bu Subsidence Crater Nevada Test Site, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Shannon Parsons

    1999-03-01

    The U-2bu subsidence crater, Corrective Action Unit 109, will be closed in accordance with the Resource Conservation and Recovery Act, the Nevada Division of Environmental Protection operational permit, and the Federal Facilities Agreement and Consent Order. The U-2bu subsidence crater is located in Area 2 of the Nevada Test Site. It was created in 1971 by an underground nuclear test with the name Miniata. The crater has a diameter of 288 meters (944 feet) and an approximate depth of 35 meters (115 feet). The subsidence crater was used as a land disposal unit for radioactive and hazardous waste from 1973 to 1988. Site disposal history is supported by memorandums, letters, and personnel who worked at the Nevada Test Site at the time of active disposal. Closure activities will include the excavation and disposal of impacted soil form the tip of the crater. Upon completion of excavation, verification samples will be collected to show that lead has been removed to concentrations be low regulatory action level. The area will then be backfilled and a soil flood diversion berm will be constructed, and certified by an independent professional engineer as to having followed the approved Closure Plan.

  1. Closure plan for Corrective Action Unit 109: U-2bu subsidence crater, Nevada Test Site, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-03-01

    The U-2bu subsidence crater, Corrective Action Unit 109, will be closed in accordance with the Resource Conservation and Recovery Act, the Nevada Division of Environmental Protection operational permit, and the Federal Facility Agreement and Consent Order. The U-2bu subsidence crater is located in Area 2 of the Nevada Test Site. It was created in 1971 by an underground nuclear test with the name Miniata. The crater has a diameter of 288 meters (944 feet) and an approximate depth of 35 meters (115 feet). Based on the results of the analyses reported in the site characterization report, the only constituents of concern in the U-2bu subsidence crater include leachable lead and total petroleum hydrocarbons. Closure activities will include the excavation and disposal of impacted soil from the top of the crater. Upon completion of excavation, verification samples will be collected to show that the leachable lead has been removed to concentrations below the regulatory action level. After sample results show that the lead has been removed, the excavated area will be backfilled and a soil flood diversion berm will be constructed as a best management practice. An independent registered professional engineer will certify the site was closed following the approved Closure Plan. Post-closure care is not warranted for this site because closure activities will involve removal of the Resource Conservation and Recovery Act constituents of concern.

  2. Optimizing laser crater enhanced Raman spectroscopy.

    Science.gov (United States)

    Lednev, V N; Sdvizhenskii, P A; Grishin, M Ya; Filichkina, V A; Shchegolikhin, A N; Pershin, S M

    2018-03-20

    Raman signal enhancement by laser crater production was systematically studied for 785 nm continuous wave laser pumping. Laser craters were produced in L-aspartic acid powder by a nanosecond pulsed solid state neodymium-doped yttrium aluminum garnet laser (532 nm, 8 ns, 1 mJ/pulse), while Raman spectra were then acquired by using a commercial spectrometer with 785 nm laser beam pumping. The Raman signal enhancement effect was studied in terms of the number of ablating pulses used, the lens-to-sample distance, and the crater-center-laser-spot offset. The influence of the experiment parameters on Raman signal enhancement was studied for different powder materials. Maximum Raman signal enhancement reached 11 fold for loose powders but decreased twice for pressed tablets. Raman signal enhancement was demonstrated for several diverse powder materials like gypsum or ammonium nitrate with better results achieved for the samples tending to give narrow and deep craters upon the laser ablation stage. Alternative ways of cavity production (steel needle tapping and hole drilling) were compared with the laser cratering technique in terms of Raman signal enhancement. Drilling was found to give the poorest enhancement of the Raman signal, while both laser ablation and steel needle tapping provided comparable results. Here, we have demonstrated for the first time, to the best of our knowledge, that a Raman signal can be enhanced 10 fold with the aid of simple cavity production by steel needle tapping in rough highly reflective materials. Though laser crater enhancement Raman spectroscopy requires an additional pulsed laser, this technique is more appropriate for automatization compared to the needle tapping approach.

  3. Being stressed outside the park — conservation of African elephants (Loxodonta africana) in Namibia

    OpenAIRE

    Hunninck, Louis; Ringstad, Iris; Jackson, Craig Ryan; May, Roelof Frans; Fossøy, Frode; Uiseb, Kenneth; Killian, Werner; Røskaft, Eivin

    2017-01-01

    The conservation of the African savanna elephant (Loxodonta africana) is of prime importance for many African countries. Interactions between elephants and humans are known to induce stress and thereby have the potential to affect elephants’ fitness. In Namibia, anthropogenic disturbances are increasing due to increasing human population size and development, particularly near protected areas, such as national parks. In this study, we investigated elephant stress levels in relation to their l...

  4. Profile, perceptions and future expectations of medical laboratory scientists in Namibia

    Directory of Open Access Journals (Sweden)

    Bruce H. Noden

    2015-08-01

    Full Text Available Background: Public healthcare systems in sub-Saharan Africa are challenged by healthcare worker shortages, loss of trained staff and attrition to the private sector. Studies have historically focused on medical doctors, nurses and pharmacists, with limited focus on medical laboratory scientists. Objectives: This study addresses the professional perspectives and expectations of the first two classes of biomedical science students, who graduated from the Polytechnic of Namibiain 2012 and 2013. Methods: A questionnaire was developed to capture qualitative and quantitative data from fourth-year students completing their final semester. Data collected included: demographic information; students’ experience; professional expectations; and perceptions about the future of biomedical science education in Namibia. Results: Amongst the 42 of 45 enrolled students who completed the questionnaire, nearly two-thirds anticipated working in government hospitals (29% or industry (35%, with fewer planning careers in private hospitals (12% or academia (14%. Most expressed an interest inworking abroad (64% and/or in the capital (64%, with fewer interested in small urban areas (48%. Only 7% expressed interest in working in a rural area. Regarding their view of the future of biomedical science in Namibia, 38% responded that it was encouraging, whereas therest responded that it was uncertain (52%, negative (2% or unknown (7%. Conclusion: Members of the first graduating classes of Namibia’s nascent Biomedical Science degree programme reported a perceived lack of opportunity for professional advancement in the field if they remained in Namibia. Continued thought needs to be given to develop sustainable strategies and opportunities to retain Namibian biomedical laboratory scientists in Namibia.

  5. The Etendeka lavas SWA/Namibia: geology, chemistry and spatial and temporal relationships

    International Nuclear Information System (INIS)

    Marsh, J.S.; Erlank, A.J.; Duncan, A.R.; Miller, R.McG.; Rex, D.C.

    1981-01-01

    The paper discusses a geologic survey on the Etendeka lavas in South West Africa/Namibia with special attention to the geology, chemistry and spatial and temporal relationships in the area. K/Ar age data indicate that the bulk of the Etendeka lavas are about 120 m.y. old. In the study use was also made of 87 Sr/ 86 Sr, 143 Nd/ 144 Nd, 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb isotope ratios

  6. Molecular Genetic Insights on Cheetah (Acinonyx jubatus) Ecology and Conservation in Namibia

    OpenAIRE

    Marker, Laurie L.; Wilkerson, Alison J. Pearks; Sarno, Ronald J.; Martenson, Janice; Breitenmoser-Würsten, Christian; O'Brien, Stephen J.; Johnson, Warren E.

    2017-01-01

    The extent and geographic patterns of molecular genetic diversity of the largest remaining free-ranging cheetah population were described in a survey of 313 individuals from throughout Namibia. Levels of relatedness, including paternity/maternity (parentage), were assessed across all individuals using 19 polymorphic microsatellite loci, and unrelated cheetahs (n = 89) from 7 regions were genotyped at 38 loci to document broad geographical patterns. There was limited differentiation among regi...

  7. At the Edge? HIV Stigma and Centrality in a Community’s Social Network in Namibia

    OpenAIRE

    Smith, Rachel A; Baker, Michelle

    2012-01-01

    Social network analysis was used to examine the relationship between HIV/AIDS stigmatization, perceived risk, and centrality in the community network (via participation in community groups). The findings from respondents in Keetmanshoop, Namibia (N = 375) showed an interaction between stigma and risk perceptions: those who perceived higher HIV risk and stronger HIV stigma participated in fewer community groups and participated in groups with members who participated less widely across the net...

  8. Laboratory and Field Investigations of Small Crater Repair Technologies

    National Research Council Canada - National Science Library

    Priddy, Lucy P; Tingle, Jeb S; McCaffrey, Timothy J; Rollings, Ray S

    2007-01-01

    .... This airfield damage repair (ADR) investigation consisted of laboratory testing of selected crater fill and capping materials, as well as full-scale field testing of small crater repairs to evaluate field mixing methods, installation...

  9. Preliminary Results from Initial Investigations of Ceres' Cratering Record from Dawn Imaging Data

    Science.gov (United States)

    Schmedemann, Nico; Michael, Gregory; Ivanov, Boris A.; Kneissl, Thomas; Neesemann, Adrian; Hiesinger, Harald; Jaumann, Ralf; Raymond, Carol A.; Russell, Christopher T.

    2015-04-01

    The highly successful Dawn mission [1] finished data collection at Vesta in 2012 and is now on its way to the dwarf planet Ceres. According to the current Ceres approach timeline of the Dawn mission, the ground resolution of the Dawn FC camera [2] will be about 10 times better than Hubble data [3] at the time of the presentation of this work. This may allow for identification of craters about 15 km in diameter. Initial mapping of sample areas may provide enough information of the cratering record in order to compare it with the theoretical Ceres crater production function we present at the 46th LPSC conference (March 16-20, 2015, The Woodlands, Texas) [4]. Our preliminary crater production function for Ceres is derived from the assumption of an icy crust just below a thin surface layer of dust [5], and a projectile population that is very similar to the one that impacted the Moon [6]. In order to scale the lunar cratering record to Ceres we use the Ivanov scaling laws [7], which allow for crater scaling based on parameters that can be derived from observations. The lunar-like approach gave reasonable good results for the crater production function on the asteroids Vesta, Ida, Lutetia and Gaspra [8]. Since the lunar surface is of basaltic composition, the correct scaling between the different materials is challenging. One crucial parameter is the transition diameter from simple to complex craters. Based on the simple to complex transition diameter on Iapetus, an icy satellite of Saturn, we expect this transition at about 12 km crater size at Ceres. This value may be slightly different due to the different temperatures at Ceres and Iapetus. If the simple to complex transition is observed at much larger diameters, the reason could be a substantial fraction of rock in the shallow subsurface of Ceres. In an ice-rich surface material high relaxation rates may also be expected that could change the shape of the crater production function. A thorough geological mapping

  10. What Prevents Men Aged 40-64 Years from Prostate Cancer Screening in Namibia?

    International Nuclear Information System (INIS)

    Kangmennaang, J.; Mkandawire, P.; Luginaah, I.

    2016-01-01

    Although a growing body of evidence demonstrates the public health burden of prostate cancer in SSA, relatively little is known about the underlying factors surrounding the low levels of testing for the disease in the context of this region. Using Namibia Demographic Health Survey dataset (NDHS, 2013), we examined the factors that influence men’s decision to screen for prostate cancer in Namibia. Methods. We use complementary log-log regression models to explore the determinants of screening for prostate cancer. We also corrected for the effect of unobserved heterogeneity that may affect screening behaviours at the cluster level. Results. The results show that health insurance coverage (OR = 2.95, ) is an important predictor of screening for prostate cancer in Namibia. In addition, higher education and discussing reproductive issues with a health worker (OR = 2.02, P = 0.05) were more likely to screening for prostate cancer. Conclusions. A universal health insurance scheme may be necessary to increase uptake of prostate cancer screening. However it needs to be acknowledged that expanded screening can have negative consequences and any allocation of scarce resources towards screening must be guided by evidence obtained from the local context about the costs and benefits of screening.

  11. Prevalence and antimicrobial resistance pattern of Salmonella in animal feed produced in Namibia.

    Science.gov (United States)

    Shilangale, Renatus P; Di Giannatale, Elisabetta; Chimwamurombe, Percy M; Kaaya, Godwin P

    2012-01-01

    The occurrence of Salmonella is a global challenge in the public health and food production sectors. Our study investigated the prevalence, serovar and antimicrobial susceptibility of strains of Salmonella serovars isolated from animal feed (meat-and-bone and blood meal) samples from two commercial abattoirs in Namibia. A total of 650 samples (n=650) were examined for the presence of Salmonella. Results showed that 10.9% (n=71) were positive for Salmonella. Of the Salmonella serovars isolated, S. Chester was the most commonly isolated serovar (19.7%), followed by S. Schwarzengrund at 12.7%. From the Salmonella isolates, 19.7% (n=14) were resistant to one or more of the antimicrobials (nalidixic acid, trimethoprim-sulfamethoxazole, sulfisoxazole, streptomycin and/or tetracycline), whereas 80.3% (n=57) were susceptible to all 16 antimicrobials tested. Resistance to sulfisoxazole and the trimethroprimsuflamethoxazole combination were the most common. The resistant isolates belonged to ten different Salmonella serovars. The susceptibility of most of the Salmonella isolated to the antimicrobials tested indicates that anti-microbial resistance is not as common and extensive in Namibia as has been reported in many other countries. It also appears that there is a range of antimicrobials available that are effective in managing Salmonella infections in Namibia. However, there is some evidence that resistance is developing and this will need further monitoring to ensure it does not become a problem.

  12. Monitoring Murder Crime in Namibia Using Bayesian Space-Time Models

    Directory of Open Access Journals (Sweden)

    Isak Neema

    2012-01-01

    Full Text Available This paper focuses on the analysis of murder in Namibia using Bayesian spatial smoothing approach with temporal trends. The analysis was based on the reported cases from 13 regions of Namibia for the period 2002–2006 complemented with regional population sizes. The evaluated random effects include space-time structured heterogeneity measuring the effect of regional clustering, unstructured heterogeneity, time, space and time interaction and population density. The model consists of carefully chosen prior and hyper-prior distributions for parameters and hyper-parameters, with inference conducted using Gibbs sampling algorithm and sensitivity test for model validation. The posterior mean estimate of the parameters from the model using DIC as model selection criteria show that most of the variation in the relative risk of murder is due to regional clustering, while the effect of population density and time was insignificant. The sensitivity analysis indicates that both intrinsic and Laplace CAR prior can be adopted as prior distribution for the space-time heterogeneity. In addition, the relative risk map show risk structure of increasing north-south gradient, pointing to low risk in northern regions of Namibia, while Karas and Khomas region experience long-term increase in murder risk.

  13. Prevalence of human immunodeficiency virus, syphilis, hepatitis B and C in blood donations in Namibia.

    Science.gov (United States)

    Mavenyengwa, Rooyen T; Mukesi, Munyaradzi; Chipare, Israel; Shoombe, Esra

    2014-05-05

    Transfusion Transmissible Infections (TTIs) such as Human Immunodeficiency Virus (HIV), syphilis, hepatitis B virus (HBV) and hepatitis C virus (HCV) are infections which are common in some communities in Southern Africa. It is important to screen blood donations for these infections. This is a retrospective study which involved reviewing of previous blood donation records for the year 2012 in Namibia. The records were analyzed to determine the prevalence of HIV, syphilis, Hepatitis B and C among blood donations with regard to gender, age and geographical region of the donors. The findings indicated a significantly low prevalence of HIV, syphilis, HBsAg and anti-Hepatitis C among the blood donations. A low infection rate of 1.3% by any of the four tested TTIs was found among the blood donations given by the donor population in Namibia in 2012. The blood donations given by the donor population in Namibia has a low infection rate with the HIV, syphilis, HBsAg and anti-HCV. A strict screening regime must continue to be used as the infections are still present albeit in small numbers.

  14. Model and experiences of initiating collaboration with traditional healers in validation of ethnomedicines for HIV/AIDS in Namibia

    Directory of Open Access Journals (Sweden)

    Chinsembu Kazhila C

    2009-10-01

    Full Text Available Abstract Many people with Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS in Namibia have access to antiretroviral drugs but some still use traditional medicines to treat opportunistic infections and offset side-effects from antiretroviral medication. Namibia has a rich biodiversity of indigenous plants that could contain novel anti-HIV agents. However, such medicinal plants have not been identified and properly documented. Various ethnomedicines used to treat HIV/AIDS opportunistic infections have not been scientifically validated for safety and efficacy. These limitations are mostly attributable to the lack of collaboration between biomedical scientists and traditional healers. This paper presents a five-step contextual model for initiating collaboration with Namibian traditional healers in order that candidate plants that may contain novel anti-HIV agents are identified, and traditional medicines used to treat HIV/AIDS opportunistic infections are subjected to scientific validation. The model includes key structures and processes used to initiate collaboration with traditional healers in Namibia; namely, the National Biosciences Forum, a steering committee with the University of Namibia (UNAM as the focal point, a study tour to Zambia and South Africa where other collaborative frameworks were examined, commemorations of the African Traditional Medicine Day (ATMD, and consultations with stakeholders in north-eastern Namibia. Experiences from these structures and processes are discussed. All traditional healers in north-eastern Namibia were willing to collaborate with UNAM in order that their traditional medicines could be subjected to scientific validation. The current study provides a framework for future collaboration with traditional healers and the selection of candidate anti-HIV medicinal plants and ethnomedicines for scientific testing in Namibia.

  15. Wind-Eroded Crater Floors and Intercrater Plains, Terra Sabaea, Mars

    Science.gov (United States)

    Irwin, Rossman P.; Wray, James J.; Mest, Scott C.; Maxwell, Ted A.

    2018-02-01

    Ancient impact craters with wind-eroded layering on their floors provide a record of resurfacing materials and processes on early Mars. In a 54 km Noachian crater in Terra Sabaea (20.2°S, 42.6°E), eolian deflation of a friable, dark-toned layer up to tens of meters thick has exposed more resistant, underlying light-toned material. These layers differ significantly from strata of similar tone described in other regions of Mars. The light-toned material has no apparent internal stratification, and visible/near-infrared spectral analysis suggests that it is rich in feldspar. Its origin is ambiguous, as we cannot confidently reject igneous, pyroclastic, or clastic alternatives. The overlying dark-toned layer is probably a basaltic siltstone or sandstone that was emplaced mostly by wind, although its weak cementation and inverted fluvial paleochannels indicate some modification by water. Negative-relief channels are not found on the crater floor, and fluvial erosion is otherwise weakly expressed in the study area. Small impacts onto this crater's floor have exposed deeper friable materials that appear to contain goethite. Bedrock outcrops on the crater walls are phyllosilicate bearing. The intercrater plains contain remnants of a post-Noachian thin, widespread, likely eolian mantle with an indurated surface. Plains near Hellas-concentric escarpments to the north are more consistent with volcanic resurfacing. A 48 km crater nearby contains similar dark-over-light outcrops but no paleochannels. Our findings indicate that dark-over-light stratigraphy has diverse origins across Mars and that some dark-toned plains with mafic mineralogy are not of igneous origin.

  16. Coesite from Wabar crater, near Al Hadida, Arabia

    Science.gov (United States)

    Chao, E.C.T.; Fahey, J.J.; Littler, J.

    1961-01-01

    The third natural occurrence of coesite, the high pressure polymorph of silica, is found at the Wabar meteorite crater, Arabia. The Wabar crater is about 300 feet in diameter and about 40 feet deep. It is the smallest of three craters where coesite has been found.

  17. 3D structure of the Gusev Crater region

    NARCIS (Netherlands)

    van Kan - Parker, M.; Zegers, T.E.; kneissl, T.; Ivanov, B.; Neukum, G.; Foing, B.

    2010-01-01

    Gusev Crater lies within the Aeolis Quadrangle of Mars at the boundary between the northern lowlands and southern highlands. The ancient valley Ma'adim Vallis dissects the highlands south of Gusev Crater and is thought to have fed the crater with sediments.High Resolution Stereo Camera data and

  18. Post-traumatic stress disorder amongst children aged 8–18 affected by the 2011 northern-Namibia floods

    Directory of Open Access Journals (Sweden)

    Simon Taukeni

    2016-01-01

    Full Text Available Extreme flooding in the northern parts of Namibia occurred in 2011, impacting many schoolgoing children in the region. The rationale for the current research is to assess post-traumatic stress disorder (PTSD on school children as a result of the floods. A self-administered Child Trauma Screening Questionnaire (CTSQ with closed-ended questions was administered to 480 children between the ages of eight and 18 years at their respective schools. The CTSQ consists of five items assessing re-experiencing and five items assessing hyper-arousal symptoms. The results show that 55.2% of learners aged 12 and below and 72.8% of learners aged 13 and above reported experiencing symptoms of trauma from the floods 2 years after the event. These percentages were quite high and are therefore a cause for concern. Given the magnitude of this problem, it is important for the government and other stakeholders to provide the necessary psychological and/or emotional support in the event of future floods or similar disasters.

  19. Mapping decadal land cover changes in the woodlands of north eastern Namibia using the Landsat satellite archive (1975-2014)

    Science.gov (United States)

    Wingate, Vladimir; Phinn, Stuart; Kuhn, Nikolaus

    2016-04-01

    Woodland savannahs provide essential ecosystem functions and services to communities. On the African continent, they are widely utilized and converted to intensive land uses. This study investigates the land cover changes over 108,038 km2 in NE Namibia using multi-sensor Landsat imagery, at decadal intervals from 1975 to 2014, with a post-classification change detection method and supervised Regression Tree classifiers. We discuss likely impacts of land tenure and reforms over the past four decades on changes in land use and land cover. These included losses, gains and exchanges between predominant land cover classes. Exchanges comprised logical conversions between woodland and agricultural classes, implying woodland clearing for arable farming, cropland abandonment and vegetation succession. The dominant change was a reduction in the area of the woodland class due to the expansion of the agricultural class, specifically, small-scale cereal and pastoral production. Woodland area decreased from 90% of the study area in 1975 to 83% in 2014, while cleared land increased from 9% to 14%. We found that the main land cover changes are conversion from woodland to agricultural and urban land uses, driven by urban expansion and woodland clearing for subsistence-based agriculture and pastoralism.

  20. Origin of discrepancies between crater size-frequency distributions of coeval lunar geologic units via target property contrasts

    Science.gov (United States)

    van der Bogert, C. H.; Hiesinger, H.; Dundas, C. M.; Krüger, T.; McEwen, A. S.; Zanetti, M.; Robinson, M. S.

    2017-12-01

    Recent work on dating Copernican-aged craters, using Lunar Reconnaissance Orbiter (LRO) Camera data, re-encountered a curious discrepancy in crater size-frequency distribution (CSFD) measurements that was observed, but not understood, during the Apollo era. For example, at Tycho, Copernicus, and Aristarchus craters, CSFDs of impact melt deposits give significantly younger relative and absolute model ages (AMAs) than impact ejecta blankets, although these two units formed during one impact event, and would ideally yield coeval ages at the resolution of the CSFD technique. We investigated the effects of contrasting target properties on CSFDs and their resultant relative and absolute model ages for coeval lunar impact melt and ejecta units. We counted craters with diameters through the transition from strength- to gravity-scaling on two large impact melt deposits at Tycho and King craters, and we used pi-group scaling calculations to model the effects of differing target properties on final crater diameters for five different theoretical lunar targets. The new CSFD for the large King Crater melt pond bridges the gap between the discrepant CSFDs within a single geologic unit. Thus, the observed trends in the impact melt CSFDs support the occurrence of target property effects, rather than self-secondary and/or field secondary contamination. The CSFDs generated from the pi-group scaling calculations show that targets with higher density and effective strength yield smaller crater diameters than weaker targets, such that the relative ages of the former are lower relative to the latter. Consequently, coeval impact melt and ejecta units will have discrepant apparent ages. Target property differences also affect the resulting slope of the CSFD, with stronger targets exhibiting shallower slopes, so that the final crater diameters may differ more greatly at smaller diameters. Besides their application to age dating, the CSFDs may provide additional information about the

  1. Summary of results of cratering experiments

    Energy Technology Data Exchange (ETDEWEB)

    Toman, J [Lawrence Radiation Laboratory, Livermore, CA (United States)

    1969-07-01

    The use of nuclear excavation as a construction technique for producing harbors, canals, highway cuts, and other large excavations requires a high assurance that the yield and depth of burst selected for the explosive will produce the desired configuration within an acceptable degree of tolerance. Nuclear excavation technology advanced significantly during 1968 as a result of the successful execution of Projects Cabriolet, Buggy, and Schooner. Until these experiments were conducted, the only nuclear data available for designing large excavations were derived from Sedan (100 kt in alluvium), Danny Boy (0.42 kt in basalt), and Sulky (0.090 kt in basalt). Applicable experience has now been extended to include two additional rock types: tuff and porphyritic trachyte, non-homogeneous formations with severe geologic layering, and a nuclear row in hard rock. The continued development of cratering calculations using in situ geophysical measurements and high-pressure test data have provided a means for predicting the cratering characteristics of untested materials. Chemical explosive cratering experiments conducted in the pre-Gondola series during the past several years have been directed toward determining the behavior of weak, wet clay shales. This material is important to nuclear excavation because of potential long-term stability problems which may affect the cratered slopes. (author)

  2. Inclement Weather Crater Repair Tool Kit

    Science.gov (United States)

    2017-11-30

    9. Corrugated steel quadcons. ....................................................................................................... 14 Figure 10...Saw cutting around crater upheaval. ERDC/GSL TR-17-26 6 The excavation team is responsible for breaking up the damaged portland cement ...in the table located on Sheet 2 in Appendix A. The corrugated steel quadcons (Item 1) are equipped with double swing doors on both ends of the

  3. Summary of results of cratering experiments

    International Nuclear Information System (INIS)

    Toman, J.

    1969-01-01

    The use of nuclear excavation as a construction technique for producing harbors, canals, highway cuts, and other large excavations requires a high assurance that the yield and depth of burst selected for the explosive will produce the desired configuration within an acceptable degree of tolerance. Nuclear excavation technology advanced significantly during 1968 as a result of the successful execution of Projects Cabriolet, Buggy, and Schooner. Until these experiments were conducted, the only nuclear data available for designing large excavations were derived from Sedan (100 kt in alluvium), Danny Boy (0.42 kt in basalt), and Sulky (0.090 kt in basalt). Applicable experience has now been extended to include two additional rock types: tuff and porphyritic trachyte, non-homogeneous formations with severe geologic layering, and a nuclear row in hard rock. The continued development of cratering calculations using in situ geophysical measurements and high-pressure test data have provided a means for predicting the cratering characteristics of untested materials. Chemical explosive cratering experiments conducted in the pre-Gondola series during the past several years have been directed toward determining the behavior of weak, wet clay shales. This material is important to nuclear excavation because of potential long-term stability problems which may affect the cratered slopes. (author)

  4. Fluids, evaporation and precipitates at Gale Crater

    OpenAIRE

    Schwenzer, S. P.; Bridges, J. C.; Leveille, R.; Wiens, R. C.; Mangold, N.; McAdam, A.; Conrad, P.; Kelley, S. P.; Westall, F.; Martín-Torres, F.; Zorzano, M.-P.

    2015-01-01

    The Mars Science Laboratory (MSL) mission landed in Gale Crater, Mars, on 6th August 2012, and has explored the Yellowknife Bay area. The detailed mineralogical and sedimentological studies provide a unique opportunity to characterise the secondary fluids associated with this habitable environment.

  5. The intercrater plains of Mercury and the Moon: Their nature, origin and role in terrestrial planet evolution. Cratering histories of the intercrater plains. Ph.D. Thesis

    Science.gov (United States)

    Leake, M. A.

    1982-01-01

    The intercrater plains of Mercury and the Moon are defined, in part, by their high densities of small craters. The crater size frequency statistics presented in this chapter may help constrain the relative ages and origins of these surfaces. To this end, the effects of common geologic processes on crater frequency statistics are compared with the diameter frequency distributions of the intercrater regions of the Moon and Mercury. Such analyses may determine whether secondary craters dominate the distribution at small diameters, and whether volcanic plains or ballistic deposits form the intercrater surface. Determining the mass frequency distribution and flux of the impacting population is a more difficult problem. The necessary information such as scaling relationships between projectile energy and crater diameter, the relative fluxes of solar system objects, and the absolute ages of surface units is model dependent and poorly constrained, especially for Mercury.

  6. Sulfate Deposition in Regolith Exposed in Trenches on the Plains Between the Spirit Landing Site and Columbia Hills in Gusev Crater, Mars

    Science.gov (United States)

    Wang, Alian; Haskin, L. A.; Squyres, S. W.; Arvidson, R.; Crumpler, L.; Gellert, R.; Hurowitz, J.; Schroeder, C.; Tosca, N.; Herkenhoff, K.

    2005-01-01

    During its exploration within Gusev crater between sol 01 and sol 158, the Spirit rover dug three trenches (Fig. 1) to expose the subsurface regolith [1, 2, 9]. Laguna trench (approx. 6 cm deep, approx.203 m from the rim of Bonneville crater) was dug in Laguna Hollow at the boundary of the impact ejecta from Bonneville crater and the surrounding plains. The Big Hole trench (approx. 6-7 cm deep) and The Boroughs trench (approx. 11 cm deep) were dug in the plains between the Bonneville crater and the Columbia Hills (approx.556 m and approx.1698 m from the rim of Bonneville crater respectively). The top, wall and floor regolith of the three trenches were investigated using the entire set of Athena scientific instruments [10].

  7. Namibia - Community-Based Rangeland and Livestock Management

    Data.gov (United States)

    Millennium Challenge Corporation — This is a mixed methods impact evaluation that randomly assigned which geographic areas were eligible to receive the program. The quantitative data collection and...

  8. Moving beyond a Destructive Past to a Decolonised and Inclusive Future: The Role of "Ubuntu"-Style Education in Providing Culturally Relevant Pedagogy for Namibia

    Science.gov (United States)

    Biraimah, Karen L.

    2016-01-01

    Namibia has one of the most dehumanising and destructive colonial pasts of any nation in Africa, or, for that matter, the world. Before colonisation, the area now known as Namibia was home to diverse cultural groups. The successive colonial regimes of Germany and South Africa inflicted genocide, brutality and apartheid on the region. Namibia…

  9. Compositions of Bedrock Containing Craters on Mars as Viewed by TES, THEMIS, and CRISM

    Science.gov (United States)

    Edwards, C. S.; Rogers, D.; Bandfield, J. L.; Christensen, P. R.

    2009-12-01

    An investigation of Martian high thermal inertia crater surfaces has been made using derived THEMIS thermal inertia data. High thermal inertia surfaces or interpreted bedrock are defined as any pixel in a THEMIS image with a thermal inertia over 1200 J K-1m-2s-1/2 and may refer to in situ rock exposures or rock-dominated surfaces. While three different surface morphologies (valley and crater walls, crater floors, and plains surface) were originally identified [Edwards et al., in press], the focus of this study is to better characterize the compositional, thermophysical, and geological characteristics of the crater floors surface. These surfaces may be related to impact-associated volcanism that often occurs in conjunction with large energetic impacts. These craters are commonly modified, lack a central peak, have shallow sloped walls, and little to no visible ejecta, indicating the relatively old ages of these impacts. They are generally large, ranging in size from 18.5 to 179km in diameter, with an average of ~52km [Edwards et al., in press]. Boulders are also observed in high-resolution imagery (e.g. HiRISE) along with fine scale randomly oriented cracks and fractures. TES spectra for ~60 of the 92 originally identified sites have been examined in detail and can be broken down into two distinctive spectral groups, olivine bearing (~80%, with >10% olivine and often >20%) and non-olivine bearing craters (~20%, with inertia crater floors. In this case, magma is likely derived from decompression melting of the mantle due to the removal of overlying material. This magma reaches the surface through fractures and cracks in the basement rock likely caused by the impact event. This is consistent with the observed compositions, as material derived directly from the Martian mantle is expected to be significantly more mafic than the surrounding country rock. These sites are likely locations where the some of the most primitive material on Mars is observed and can be used to

  10. Wrinkle Ridges and Young Fresh Crater

    Science.gov (United States)

    2002-01-01

    (Released 10 May 2002) The Science Wrinkle ridges are a very common landform on Mars, Mercury, Venus, and the Moon. These ridges are linear to arcuate asymmetric topographic highs commonly found on smooth plains. The origin of wrinkle ridges is not certain and two leading hypotheses have been put forth by scientists over the past 40 years. The volcanic model calls for the extrusion of high viscosity lavas along linear conduits. This thick lava accumulated over these conduits and formed the ridges. The other model is tectonic and advocates that the ridges are formed by compressional faulting and folding. Today's THEMIS image is of the ridged plains of Lunae Planum located between Kasei Valles and Valles Marineris in the northern hemisphere of the planet. Wrinkle ridges are found mostly along the eastern side of the image. The broadest wrinkle ridges in this image are up to 2 km wide. A 3 km diameter young fresh crater is located near the bottom of the image. The crater's ejecta blanket is also clearly seen surrounding the sharp well-defined crater rim. These features are indicative of a very young crater that has not been subjected to erosional processes. The Story The great thing about the solar system is that planets are both alike and different. They're all foreign enough to be mysterious and intriguing, and yet familiar enough to be seen as planetary 'cousins.' By comparing them, we can learn a lot about how planets form and then evolve geologically over time. Crinkled over smooth plains, the long, wavy raised landforms seen here are called 'wrinkle ridges,' and they've been found on Mars, Mercury, Venus, and the Moon - that is, on rocky bodies that are a part of our inner solar system. We know from this observation that planets (and large-enough moons) follow similar processes. What we don't know for sure is HOW these processes work. Scientists have been trying to understand how wrinkle ridges form for 40 years, and they still haven't reached a conclusion. That

  11. Geologic Structures in Crater Walls on Vesta

    Science.gov (United States)

    Mittlefehldt, David W.; Beck, A. W.; Ammannito, E.; Carsenty, U.; DeSanctis, M. C.; LeCorre, L.; McCoy, T. J.; Reddy, V.; Schroeder, S. E.

    2012-01-01

    The Framing Camera (FC) on the Dawn spacecraft has imaged most of the illuminated surface of Vesta with a resolution of apporpx. 20 m/pixel through different wavelength filters that allow for identification of lithologic units. The Visible and Infrared Mapping Spectrometer (VIR) has imaged the surface at lower spatial resolution but high spectral resolution from 0.25 to 5 micron that allows for detailed mineralogical interpretation. The FC has imaged geologic structures in the walls of fresh craters and on scarps on the margin of the Rheasilvia basin that consist of cliff-forming, competent units, either as blocks or semi-continuous layers, hundreds of m to km below the rims. Different units have different albedos, FC color ratios and VIR spectral characteristics, and different units can be juxtaposed in individual craters. We will describe different examples of these competent units and present preliminary interpretations of the structures. A common occurrence is of blocks several hundred m in size of high albedo (bright) and low albedo (dark) materials protruding from crater walls. In many examples, dark material deposits lie below coherent bright material blocks. In FC Clementine color ratios, bright material is green indicating deeper 1 m pyroxene absorption band. VIR spectra show these to have deeper and wider 1 and 2 micron pyroxene absorption bands than the average vestan surface. The associated dark material has subdued pyroxene absorption features compared to the average vestan surface. Some dark material deposits are consistent with mixtures of HED materials with carbonaceous chondrites. This would indicate that some dark material deposits in crater walls are megabreccia blocks. The same would hold for bright material blocks found above them. Thus, these are not intact crustal units. Marcia crater is atypical in that the dark material forms a semi-continuous, thin layer immediately below bright material. Bright material occurs as one or more layers. In

  12. Heavy Cratering near Callisto's South Pole

    Science.gov (United States)

    1997-01-01

    Images from NASA's Galileo spacecraft provide new insights into this region near Callisto's south pole. This two frame mosaic shows a heavily cratered surface with smooth plains in the areas between craters. North is to the top of the image. The smoothness of the plains appears to increase toward the south pole, approximately 480 kilometers (293 miles) south of the bottom of the image. This smoothness of Callisto's surface was not evident in images taken during the 1979 flyby of NASA's Voyager spacecraft because the resolution was insufficient to show the effect. This smooth surface, and the process(es) that cause it, are among the most intriguing aspects of Callisto. Although not fully understood, the process(es) responsible for this smoothing could include erosion by tiny meteorites and energetic ions. Some craters, such as Keelut, the 47 kilometer (29 mile) crater in the lower right corner, have sharp, well defined rims. Keelut contains an inner ring surrounding a central depression about 17 kilometers (11 miles) in diameter. Keelut, and the more irregularly shaped, degraded Reginleif, the 32 kilometer (19.5 mile) crater in the top center of the image, are very shallow and have flat floors. Crater forms can be seen down to less than 2 kilometers (1.2 miles) in diameter in the image. Each picture element (pixel) in this image is approximately 0.68 kilometers (0.41 miles) across.This image which was taken by the Galileo spacecraft's solid state imaging (CCD) system during its eighth orbit around Jupiter, on May 6th, 1997. The center of the image is located at 71.3 degrees south latitude, 97.6 degrees west longitude, and was taken when the spacecraft was approximately 35,470 kilometers (21,637 miles) from Callisto.The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http

  13. An analysis of policies for cotrimoxazole, amoxicillin and azithromycin use in Namibia's public sector: Findings and therapeutic implications.

    Science.gov (United States)

    Kibuule, Dan; Mubita, Mwangana; Naikaku, Ester; Kalemeera, Francis; Godman, Brian B; Sagwa, Evans

    2017-02-01

    Despite Namibia's robust medicine use systems and policies, antibiotic use indicators remain suboptimal. Recent medicine use surveys rank cotrimoxazole, amoxicillin and azithromycin (CAA) among the most used medicines. However, there is rising resistance to CAA (55.9%-96.7%). Unfortunately, to date, there have been limited studies evaluating policies to improve antibiotic use in Namibia. To evaluate public sector pharmaceutical policies and guidelines influencing the therapeutic use of CAA antibiotics in Namibia. Evaluate Namibia's pharmaceutical policies and guidelines for CAA use through quantitative text analysis. The main outcome variables were the existence of antibiotic policies, therapeutic indications per antibiotic and the type/level of healthcare facility allowed to use the antibiotic. Policies for antibiotic use were limited, with only the draft Namibia Medicines Policy having a statement on antibiotic use. Several essential antibiotics had no therapeutic indications mentioned in the guidelines. Twenty-nine antibiotics were listed for 69 therapeutic indications; CAA (49.3%) antibiotics and ATC J01C/J01D (48%) having the highest indications per antibiotic. For CAA antibiotics, this suggested use was mainly for acute respiratory infections (n=22, 37.2%). Published policies (58.6%-17/29) recommended antibiotics for use at the primary healthcare (PHC) level, with CAA antibiotics recommended mostly for respiratory tract infections and genitourinary infections. Policy and guidelines for antibiotic use in Namibia are not comprehensive and are skewed towards PHCs. Existing policies promote the wide use of CAA antibiotics, which may inadvertently result in their inappropriate use enhancing resistance rates. This calls for the development of more comprehensive antibiotic guidelines and essential medicine lists in tandem with local antimicrobial resistance patterns. In addition, educational initiatives among all key stakeholder groups. © 2017 John Wiley & Sons Ltd.

  14. Detection of Crater Rims by Image Analysis in Very High Resolution Images of Mars, Mercury and the Moon

    Science.gov (United States)

    Pina, P.; Marques, J. S.; Bandeira, L.

    2013-12-01

    The adaptive nature of automated crater detection algorithms permits achieving a high level of autonomous detections in different surfaces and consequently becoming an important tool in the update of crater catalogues. Nevertheless, the available approaches assume all craters as circular and only provide as output the radius and location of each crater. However, the delineation of impact craters following the local variability of the rims is also important to, among others, evaluate their degree of degradation or preservation, namely those studies related to ancient climate analysis. This contour determination is normally prepared in a manual way but can advantageously be done by image analysis methods, eliminating subjectivity and allowing large scale delineations. We have recently proposed a pair of independent approaches to tackle with this problem, one based on processing the crater image in polar coordinates [1], the other using morphological operators [2], which achieved a good degree of success on very high resolution images from Mars [3-4], but where enough room for improvement was still available. Thus, the integration of both approaches into a single one, suppressing the individual drawbacks of the previous approaches, permitted to strength the detection procedure. We describe now the novel sequence of processing that we have built and test it intensively in a wider variety of planetary surfaces, namely, those of Mars, Mercury and the Moon, using the very high resolution images provided by HiRISE, MDIS and LROC cameras. The automated delineations of the craters are compared to a ground-truth reference (manually delineated contours), so a quantitative evaluation can be performed; on a dataset constituted by more than one thousand impact craters we have obtained a global high delineation rate. The breakdown by crater size on each surface is performed. The whole processing procedure works on raster images and also delivers the output in the same image format

  15. Layers of 'Cabo Frio' in 'Victoria Crater'

    Science.gov (United States)

    2006-01-01

    This view of 'Victoria crater' is looking southeast from 'Duck Bay' towards the dramatic promontory called 'Cabo Frio.' The small crater in the right foreground, informally known as 'Sputnik,' is about 20 meters (about 65 feet) away from the rover, the tip of the spectacular, layered, Cabo Frio promontory itself is about 200 meters (about 650 feet) away from the rover, and the exposed rock layers are about 15 meters (about 50 feet) tall. This is an approximately true color rendering of images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity during the rover's 952nd sol, or Martian day, (Sept. 28, 2006) using the camera's 750-nanometer, 530-nanometer and 430-nanometer filters.

  16. Local soil quality assessment of north-central Namibia: integrating farmers' and technical knowledge

    Directory of Open Access Journals (Sweden)

    B. Prudat

    2018-02-01

    Full Text Available Soil degradation is a major threat for farmers of semi-arid north-central Namibia. Soil conservation practices can be promoted by the development of soil quality (SQ evaluation toolboxes that provide ways to evaluate soil degradation. However, such toolboxes must be adapted to local conditions to reach farmers. Based on qualitative (interviews and soil descriptions and quantitative (laboratory analyses data, we developed a set of SQ indicators relevant for our study area that integrates farmers' field experiences (FFEs and technical knowledge. We suggest using participatory mapping to delineate soil units (Oshikwanyama soil units, KwSUs based on FFEs, which highlight mostly soil properties that integrate long-term productivity and soil hydrological characteristics (i.e. internal SQ. The actual SQ evaluation of a location depends on the KwSU described and is thereafter assessed by field soil texture (i.e. chemical fertility potential and by soil colour shade (i.e. SOC status. This three-level information aims to reveal SQ improvement potential by comparing, for any location, (a estimated clay content against median clay content (specific to KwSU and (b soil organic status against calculated optimal values (depends on clay content. The combination of farmers' and technical assessment cumulates advantages of both systems of knowledge, namely the integrated long-term knowledge of the farmers and a short- and medium-term SQ status assessment. The toolbox is a suggestion for evaluating SQ and aims to help farmers, rural development planners and researchers from all fields of studies understanding SQ issues in north-central Namibia. This suggested SQ toolbox is adapted to a restricted area of north-central Namibia, but similar tools could be developed in most areas where small-scale agriculture prevails.

  17. Estimation of the prevalence and rate of acute transfusion reactions occurring in Windhoek, Namibia

    Science.gov (United States)

    Meza, Benjamin P.L.; Lohrke, Britta; Wilkinson, Robert; Pitman, John P.; Shiraishi, Ray W.; Bock, Naomi; Lowrance, David W.; Kuehnert, Matthew J.; Mataranyika, Mary; Basavaraju, Sridhar V.

    2014-01-01

    Background Acute transfusion reactions are probably common in sub-Saharan Africa, but transfusion reaction surveillance systems have not been widely established. In 2008, the Blood Transfusion Service of Namibia implemented a national acute transfusion reaction surveillance system, but substantial under-reporting was suspected. We estimated the actual prevalence and rate of acute transfusion reactions occurring in Windhoek, Namibia. Methods The percentage of transfusion events resulting in a reported acute transfusion reaction was calculated. Actual percentage and rates of acute transfusion reactions per 1,000 transfused units were estimated by reviewing patients’ records from six hospitals, which transfuse >99% of all blood in Windhoek. Patients’ records for 1,162 transfusion events occurring between 1st January – 31st December 2011 were randomly selected. Clinical and demographic information were abstracted and Centers for Disease Control and Prevention National Healthcare Safety Network criteria were applied to categorize acute transfusion reactions1. Results From January 1 – December 31, 2011, there were 3,697 transfusion events (involving 10,338 blood units) in the selected hospitals. Eight (0.2%) acute transfusion reactions were reported to the surveillance system. Of the 1,162 transfusion events selected, medical records for 785 transfusion events were analysed, and 28 acute transfusion reactions were detected, of which only one had also been reported to the surveillance system. An estimated 3.4% (95% confidence interval [CI]: 2.3–4.4) of transfusion events in Windhoek resulted in an acute transfusion reaction, with an estimated rate of 11.5 (95% CI: 7.6–14.5) acute transfusion reactions per 1,000 transfused units. Conclusion The estimated actual rate of acute transfusion reactions is higher than the rate reported to the national haemovigilance system. Improved surveillance and interventions to reduce transfusion-related morbidity and mortality

  18. Local soil quality assessment of north-central Namibia: integrating farmers' and technical knowledge

    Science.gov (United States)

    Prudat, Brice; Bloemertz, Lena; Kuhn, Nikolaus J.

    2018-02-01

    Soil degradation is a major threat for farmers of semi-arid north-central Namibia. Soil conservation practices can be promoted by the development of soil quality (SQ) evaluation toolboxes that provide ways to evaluate soil degradation. However, such toolboxes must be adapted to local conditions to reach farmers. Based on qualitative (interviews and soil descriptions) and quantitative (laboratory analyses) data, we developed a set of SQ indicators relevant for our study area that integrates farmers' field experiences (FFEs) and technical knowledge. We suggest using participatory mapping to delineate soil units (Oshikwanyama soil units, KwSUs) based on FFEs, which highlight mostly soil properties that integrate long-term productivity and soil hydrological characteristics (i.e. internal SQ). The actual SQ evaluation of a location depends on the KwSU described and is thereafter assessed by field soil texture (i.e. chemical fertility potential) and by soil colour shade (i.e. SOC status). This three-level information aims to reveal SQ improvement potential by comparing, for any location, (a) estimated clay content against median clay content (specific to KwSU) and (b) soil organic status against calculated optimal values (depends on clay content). The combination of farmers' and technical assessment cumulates advantages of both systems of knowledge, namely the integrated long-term knowledge of the farmers and a short- and medium-term SQ status assessment. The toolbox is a suggestion for evaluating SQ and aims to help farmers, rural development planners and researchers from all fields of studies understanding SQ issues in north-central Namibia. This suggested SQ toolbox is adapted to a restricted area of north-central Namibia, but similar tools could be developed in most areas where small-scale agriculture prevails.

  19. Life stories of depressed adult women in peri-urban Namibia.

    Science.gov (United States)

    Shifiona, N N; Poggenpoel, M; Myburgh, C P H

    2006-05-01

    The problems women in peri-urban Namibia are faced with are multi-dimensional. Like women in other communities they face the pressure of having a number of responsibilities, namely working, being a wife and mother, taking care of their families and perhaps caring for aging parents. Sometimes the pressure can be too overwhelming to manage. As a result, many women become depressed. Studies on depression among black African women in Namibia could not be traced. It was therefore considered to find out how women suffering from depression from this part of the world tell their life stories. The purpose of the study was two-fold: Firstly, to explore and describe the life stories of depressed adult women in peri-urban Namibia, and secondly to use the information obtained to describe guidelines for psychiatric nurses working with these patients at psychiatric outpatient clinics as well as in the community. A qualitative phenomenological research design of an explorative, descriptive and contextual nature was used. The researcher approached the subjects and their experiences with an open mind. Ten depressed adult women between 21-55 years were involved in the research. The researcher strived to adhere to the principles of trustworthiness. To ensure this Guba's model (in Krefting, 1991: 217) of trustworthiness was adopted. All the interviews were analysed following Tesch's method (Creswell, 1994: 154-55). The services of an independent coder were obtained. The results indicated that impaired interpersonal interactions and stressful life events have a negative influence on the daily life of women leading to the development of depressive symptoms. Guidelines to support psychiatric nurses working with depressed women were drawn up.

  20. Complementary benefits of tourism and hunting to communal conservancies in Namibia.

    Science.gov (United States)

    Naidoo, Robin; Weaver, L Chris; Diggle, Richard W; Matongo, Greenwell; Stuart-Hill, Greg; Thouless, Chris

    2016-06-01

    Tourism and hunting both generate substantial revenues for communities and private operators in Africa, but few studies have quantitatively examined the trade-offs and synergies that may result from these two activities. We evaluated financial and in-kind benefit streams from tourism and hunting on 77 communal conservancies in Namibia from 1998 to 2013, where community-based wildlife conservation has been promoted as a land-use that complements traditional subsistence agriculture. We used data collected annually for all communal conservancies to characterize whether benefits were derived from hunting or tourism. We classified these benefits into 3 broad classes and examined how benefits flowed to stakeholders within communities under the status quo and under a simulated ban on hunting. Across all conservancies, total benefits from hunting and tourism increased at roughly the same rate, although conservancies typically started generating benefits from hunting within 3 years of formation as opposed to after 6 years for tourism. Disaggregation of data revealed that the main benefits from hunting were income for conservancy management and food in the form of meat for the community at large. The majority of tourism benefits were salaried jobs at lodges. A simulated ban on trophy hunting significantly reduced the number of conservancies that could cover their operating costs, whereas eliminating income from tourism did not have as severe an effect. Given that the benefits generated from hunting and tourism typically begin at different times in a conservancy's life-span (earlier vs. later, respectively) and flow to different segments of local communities, these 2 activities together may provide the greatest incentives for conservation on communal lands in Namibia. A singular focus on either hunting or tourism would reduce the value of wildlife as a competitive land-use option and have grave repercussions for the viability of community-based conservation efforts in Namibia

  1. Tectonics and sedimentation of late Proterozoic Damaran convergent continental margin, Khomas Hochland, central Namibia

    International Nuclear Information System (INIS)

    Kukla, P.A.

    1990-01-01

    The Late Proterozoic Khomas Trough comprises metasedimentary and metabasic rocks of the Kuiseb Formation and its evolution plays an important role in understanding the Damara orogenic belt as a whole. An attempt was made to characterize the metasedimentary and metabasic rocks encountered by means of sedimentological, structural, petrographical, mineralogical and geochemical methods. This led to the modelling of the geotectonic evolution of the Khomas Trough with particular focus on the sedimentary palaeoenvironments and the structural evolution of this area during Pan-African orogeny in Namibia. 251 refs., 81 figs., 14 tabs

  2. An Approach to User Interface Design with Two Indigenous Groups in Namibia

    DEFF Research Database (Denmark)

    Rodil, Kasper; Winschiers-Theophilus, Heike; Stanley, Colin

    2014-01-01

    indigenous knowledge practices with digital object taxonomies. We present a method (picture card sorting) of discovering taxonomies that influence the users' interaction with a prototype system to preserve indigenous knowledge. Finally we describe the design implications, a new design approach based...... a user interface of a tablet based system aimed at preserving Indigenous Knowledge for rural Herero communities, we present findings from two sites in Namibia, complementing prior research. Participants who had little or no previous experience with technologies informed our endeavour of aligning local...

  3. Methods of flood extent mapping using SAR imagery in the Zambezi (Caprivi) Region, Namibia

    CSIR Research Space (South Africa)

    Kemp, J

    2014-10-01

    Full Text Available mapping using SAR imagery in the Zambezi (Caprivi) Region, Namibia Jaco Kemp1, Mariel Bessinger1, Melanie Luck-Vogel2 y o u r k n o w l e d g e p a r t n e r Department of Geography and Environmental Studies 2 Zambezi Region y o... u r k n o w l e d g e p a r t n e r Department of Geography and Environmental Studies 3 Zambezi Region y o u r k n o w l e d g e p a r t n e r Department of Geography and Environmental Studies 4 Zambezi...

  4. The isostatic state of Mead crater

    Science.gov (United States)

    Banerdt, W. B.; Konopliv, A. S.; Rappaport, N. J.; Sjogren, W. L.; Grimm, R. E.; Ford, P. G.

    1994-01-01

    We have analyzed high-resolution Magellan Doppler tracking data over Mead crater, using both line-of-sight and spherical harmonic methods, and have found a negative gravity anomaly of about 4-5 mgal (at spacecraft altitude, 182 km). This is consistent with no isostatic compensation of the present topography; the uncertainty in the analysis allows perhaps as much as 30% compensation at shallow dpeths (approximately 25 km). This is similar to observations of large craters on Earth, which are not generally compensated, but contrasts with at least some lunar basins which are inferred to have large Moho uplifts and corresponding positive Bouguer anomalies. An uncompensated load of this size requires a lithosphere with an effective elastic lithosphere thickness greater than 30 km. In order for the crust-mantle boundary not to have participated in the deformation associated with the collapse of the transient cavity during the creation of the crater, the yield strength near the top of the mantle must have been significantly higher on Earth and Venus than on the Moon at the time of basin formation. This might be due to increased strength against frictional sliding at the higher confining pressures within the larger planets. Alternatively, the thinner crusts of Earth and Venus compared to that of the Moon may result in higher creep strength of the upper mantle at shallower depths.

  5. Ejecta from single-charge cratering explosions

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, R H

    1970-05-15

    The objective was to obtain experimental data tracing the location of ejecta to its origin within the crater region. The experiment included ten high-explosive spherical charges weighing from 8 to 1000 pounds and detonated in a playa dry lake soil on the Tonopah Test Range. Each event included from 24 to 40 locations of distinctly different tracer material embedded in a plane in the expected crater region. Tracers consisted of glass, ceramic and bugle beads, chopped metal, and plastic wire. Results of this experiment yielded data on tracer dispersion as a function of charge weight, charge burial depth and tracer emplacement position. Tracer pattern parameters such as center-of-tracer mass, range to center-of-tracer mass, and angle to center-of-tracer mass were determined. There is a clear tendency for range (to center-of-tracer mass) and the size of the dispersion pattern to decrease as tracer emplacement depth increases. Increasing tracer emplacement depth and range tends to decrease the area over which tracers are dispersed on the ground surface. Tracers at the same scaled position relative to the charge were deposited closer to the crater (on a scaled basis) as charge weight was increased. (author)

  6. Characterizing dark mantle deposits in the lunar crater Alphonsus

    Science.gov (United States)

    Shkuratov, Y. G.; Ivanov, M. A.; Korokhin, V. V.; Kaydash, V. G.; Basilevsky, A. T.; Videen, G.; Hradyska, L. V.; Velikodsky, Y. I.; Marchenko, G. P.

    2018-04-01

    We analyze available remote-sensing data of the crater Alphonsus, focusing on the analysis of the crater's dark mantle deposits (DMDs), which includes images from NASA Clementine and Lunar Reconnaissance Orbiter (LRO), Japanese Selene (Kaguya), and Indian Chandrayaan-1 missions. The Alphonsus DMDs are gentle-sloped flat hills with typical heights of several meters, which are presented with pyroclastic materials. Our determination of the absolute ages of the Alphonsus DMDs by the technique of crater size-frequency distributions shows that they are ∼200-400 m.y. old. However, being geologically young, the Alphonsus DMDs are not seen in OMAT maps. The DMDs have noticeably lower content of TiO2 (2-3%) than the mare regions to the west (>4%). The assessment of total pyroxene shows it has a higher abundance in the DMDs, although LRO Diviner measurements of the Chirstiansen feature suggest, rather, a high abundance of olivine. The DMDs pyroclastic material has no signs of OH/H2O compounds. We may suggest that this characteristic of the DMDs either relates to their impact reworking and loss of the OH/H2O compounds or to the non-water volatiles as the driving agent of the pyroclastic activity. The compositional assessments of the DMDs may be flawed from contamination with the surrounding material due to horizontal and vertical transportation due to impacts. This effect probably can be observed in LROC NAC images of high resolution. A very dark material outcropping on the slopes of the vent depression is seen due to renovation of the regolith on the steep walls of the depression. Thus, at smaller phase angles, the pyroclastic material is dark and at larger phase angles it appears almost like the surrounding material. This means that the phase dependence of the outcropping dark material is shallow; i.e. the dark surface is smoother than its surroundings. This may suggest venting of gases resulting in fluidization of the granular pyroclastic material of the deposit.

  7. Huygens Crater: Insights into Noachian Volcanism, Stratigraphy, and Aqueous Processes

    Science.gov (United States)

    Ackiss, S. E.; Wray, J. J.; Seelos, K. D.; Niles, P. B.

    2015-01-01

    Huygens crater is a well preserved peak ring structure on Mars centered at 13.5 deg S, 55.5 deg E in the Noachian highlands between Terras Tyrrhena and Sabaea near the NW rim of Hellas basin. With a diameter of approximately 470 km, it uplifted and exhumed pre-Noachian crustal materials from depths greater than 25 km, penetrating below the thick, ubiquitous layer of Hellas ejecta. In addition, Huygens served as a basin for subsequent aqueous activity, including erosion/deposition by fluvial valley networks and subsurface alteration that is now exposed by smaller impacts. Younger mafic-bearing plains that partially cover the basin floor and surrounding intercrater areas were likely emplaced by later volcanism.

  8. Coulomb explosion sputtering, crater and blister formation by HCI

    International Nuclear Information System (INIS)

    Parilis, E.S.

    2001-01-01

    A simple theoretical model based on gradual Auger neutralization of a highly charged ion as it approaches the surface, with consequent positive charge deposition in surface layers and their expansion due to Coulomb repulsion provides the means to make some estimates that could explain the creation of very shallow blisters and craters on surface, as well as sputtering of up to 10 3 atoms in a single ion impact. Calculation of the dependence of blister size on projectile charge, based on charge evolution, gives some results fitting the experimental data. The model deals not just with the conducting properties of the solid, but with its structure as well, for instance the layered structure of mica. While the general source of energy remains the same, the particular mechanism of its realization depends largely on the composition, structure and electronic properties of the solid. The composition of the ejecta is discussed within the framework of the shock wave approach. (orig.)

  9. Influence of Fault-Controlled Topography on Fluvio-Deltaic Sedimentary Systems in Eberswalde Crater, Mars

    Science.gov (United States)

    Rice, Melissa S.; Gupta, Sanjeev; Bell, James F., III; Warner, Nicholas H.

    2011-01-01

    Eberswalde crater was selected as a candidate landing site for the Mars Science Laboratory (MSL) mission based on the presence of a fan-shaped sedimentary deposit interpreted as a delta. We have identified and mapped five other candidate fluvio -deltaic systems in the crater, using images and digital terrain models (DTMs) derived from the Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX). All of these systems consist of the same three stratigraphic units: (1) an upper layered unit, conformable with (2) a subpolygonally fractured unit, unconformably overlying (3) a pitted unit. We have also mapped a system of NNE-trending scarps interpreted as dip-slip faults that pre-date the fluvial -lacustrine deposits. The post-impact regional faulting may have generated the large-scale topography within the crater, which consists of a Western Basin, an Eastern Basin, and a central high. This topography subsequently provided depositional sinks for sediment entering the crater and controlled the geomorphic pattern of delta development.

  10. Imaging the Chicxulub central crater zone from large scale seismic acoustic wave propagation and gravity modeling

    Science.gov (United States)

    Fucugauchi, J. U.; Ortiz-Aleman, C.; Martin, R.

    2017-12-01

    Large complex craters are characterized by central uplifts that represent large-scale differential movement of deep basement from the transient cavity. Here we investigate the central sector of the large multiring Chicxulub crater, which has been surveyed by an array of marine, aerial and land-borne geophysical methods. Despite high contrasts in physical properties,contrasting results for the central uplift have been obtained, with seismic reflection surveys showing lack of resolution in the central zone. We develop an integrated seismic and gravity model for the main structural elements, imaging the central basement uplift and melt and breccia units. The 3-D velocity model built from interpolation of seismic data is validated using perfectly matched layer seismic acoustic wave propagation modeling, optimized at grazing incidence using shift in the frequency domain. Modeling shows significant lack of illumination in the central sector, masking presence of the central uplift. Seismic energy remains trapped in an upper low velocity zone corresponding to the sedimentary infill, melt/breccias and surrounding faulted blocks. After conversion of seismic velocities into a volume of density values, we use massive parallel forward gravity modeling to constrain the size and shape of the central uplift that lies at 4.5 km depth, providing a high-resolution image of crater structure.The Bouguer anomaly and gravity response of modeled units show asymmetries, corresponding to the crater structure and distribution of post-impact carbonates, breccias, melt and target sediments

  11. Mineral-produced high-pressure striae and clay polish: Key evidence for nonballistic transport of ejecta from Ries crater

    Science.gov (United States)

    Chao, E.C.T.

    1976-01-01

    Recently discovered mineral-produced, deeply incised striae and mirror-like polish on broken surfaces of limestone fragments from the sedimentary ejecta of the Ries impact crater of southern Germany are described. The striae and polish were produced under high confining pressures during high-velocity nonballistic transport of the ejecta mass within the time span of the cratering event (measured in terms of seconds). The striae on these fragments were produced by scouring by small mineral grains embedded in the surrounding clay matrix, and the polish was formed under the same condition, by movements of relatively fragment-free clay against the fragment surfaces. The occurrence of these striae and polish is key evidence for estimating the distribution and determining the relative importance of nonballistic and ballistic transport of ejecta from the shallow Ries stony meteorite impact crater.

  12. The Gale Crater Mound in a Regional Geologic Setting: Comparison Study of Wind Erosion in Gale Crater and Within a 1000 KM Radius

    Science.gov (United States)

    Dapremont. A.; Allen, C.; Runyon, C.

    2014-01-01

    Gale is a Late Noachian/Early Hesperian impact crater located on the dichotomy boundary separating the southern highlands and the northern lowlands of Mars. NASA's Curiosity Rover is currently exploring Gale, searching for evidence of habitability early in Mars history. With an approximate diameter of 155 km, and a approx. 5 km central mound informally titled Mt. Sharp, Gale represents a region of geologic interest due to the abundance of knowledge that can be derived, through its sedimentary deposits, pertaining to the environmental evolution of Mars. This study was undertaken to compare wind erosional features in Gale Crater and within sediments in a 1000 km radial area. The ultimate objective of this comparison was to determine if or how Gale relates to the surrounding region.

  13. Crater populations in the early history of Mercury

    International Nuclear Information System (INIS)

    Guest, J.E.; Gault, D.E.

    1976-01-01

    Crater populations on two major geologic units of Mercury have been classified into three morphologic types which characterize their state of degradation. The results indicate that one or more processes either prior to or contemporary with the formation of the 1300 km diameter Caloris Planitia reduced the population of fresh craters smaller than 70--80 km diameter and totally erased the population of fresh craters smaller than 20--30 km

  14. Constraints on early events in Martian history as derived from the cratering record

    International Nuclear Information System (INIS)

    Barlow, N.G.

    1990-01-01

    The shapes and densities of crater size-frequency distribution curves are used to constrain two major events early in Martian history: termination of high obliteration rates and viability of the multiple impact origin of the crustal dichotomy. Distribution curves of fresh craters superposed on uplands, intercrater plains, and ridged plains display shapes and densities indicative of formation prior to the end of heavy bombardment. This observation correlates with other geologic evidence, suggesting a major change in the erosional regime following the last major basin size impact (i.e., Argrye). In addition, the multisloped nature of the curves supports the idea that the downturn in the crater size-frequency distribution curves reflects the size-frequency distribution of the impactors rather than being the result of erosion. The crustal dichotomy formed prior to the heavy bombardment intermediate epoch based on distribution curves of knobby terrain; if the dichotomy resulted from a single gigantic impact, this observation places constraints on when this event happened. An alternate theory for dichotomy formation, the multiple-impact basin idea, is questioned: since distribution curves of large basins as well as heavy bombardment era units are not represented by a -3 differential power law function, this study finds fewer basins missing on Mars compare to the Moon and Mercury than previously reported. The area covered by these missing basins is less than that covered the northern plains

  15. Interventions geared towards strengthening the health system of Namibia through the integration of palliative care.

    Science.gov (United States)

    Freeman, Rachel; Luyirika, Emmanuel Bk; Namisango, Eve; Kiyange, Fatia

    2016-01-01

    The high burden of non-communicable diseases and communicable diseases in Africa characterised by late presentation and diagnosis makes the need for palliative care a priority from the point of diagnosis to death and through bereavement. Palliative care is an intervention that requires a multidisciplinary team to address the multifaceted needs of the patient and family. Thus, its development takes a broad approach that involves engaging all key stakeholders ranging from policy makers, care providers, educators, the public, patients, and families. The main focus of stakeholder engagement should address some core interventions geared towards improving knowledge and awareness, strengthening skills and attitudes about palliative care. These interventions include educating health and allied healthcare professionals on the palliative care-related problems of patients and best practices for care, explaining palliative care as a clinical and holistic discipline and demonstrating its effectiveness, the need to include palliative care into national policies, strategic plans, training curriculums of healthcare professionals and the engagement of patients, families, and communities. Interventions from a five-year programme that was aimed at strengthening the health system of Namibia through the integration of palliative care for people living with HIV and AIDS and cancer in Namibia are shared. This article illustrates how a country can implement the World Health Organisation's public health strategy for developing palliative care services, which recommends four pillars: government policy, education, drug availability, and implementation.

  16. Being stressed outside the park—conservation of African elephants (Loxodonta africana) in Namibia

    Science.gov (United States)

    Ringstad, Iris H; Jackson, Craig R; May, Roel; Fossøy, Frode; Uiseb, Kenneth; Killian, Werner; Palme, Rupert; Røskaft, Eivin

    2017-01-01

    Abstract The conservation of the African savanna elephant (Loxodonta africana) is of prime importance for many African countries. Interactions between elephants and humans are known to induce stress and thereby have the potential to affect elephants’ fitness. In Namibia, anthropogenic disturbances are increasing due to increasing human population size and development, particularly near protected areas, such as national parks. In this study, we investigated elephant stress levels in relation to their land use, specifically their protection status, comparing elephants within Etosha National Park in Namibia with elephants residing outside the park. We noninvasively collected dung samples of 91 elephants and determined the concentration of faecal glucocorticoid metabolites (fGCM), an indicator of physiological stress. Elephants outside the park (N = 35) had significantly higher concentrations of fGCM than those inside ENP (N = 56), suggesting that, despite including community-based conservancies, unprotected areas are more stressful for elephants than protected areas, most likely due to increased interactions with humans. We also found that males had lower fGCM concentrations than females, but no significant effect of age, body size or group size was detected. Additionally, herd sizes were significantly smaller and calf recruitment was potentially lower in unprotected areas. These findings underpin the importance of protected areas such as ENP, while encouraging decision-makers to continue reducing and mitigating potential human-induced disturbances. PMID:29270294

  17. Namibia: un esempio di cooperazione internazionale per lo studio delle patologie emergenti

    Directory of Open Access Journals (Sweden)

    Attilio Pini

    2009-06-01

    Full Text Available L'Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise è impegnato da anni nella ricerca e sperimentazione mirate ad approfondire la conoscenza delle malattie esotiche, cioè di quelle malattie che non sono presenti sul territorio nazionale. Per poter raggiungere tali obiettivi, è importante impegnarsi nella creazione di una rete di collaborazioni con Laboratori ed Enti di ricerca a livello nazionale ed internazionale. I rapporti che l'Istituto ha instaurato soprattutto con la Namibia e più di recente Botswana si stanno rivelando di notevole aiuto per la reciproca crescita tecnico-scientifica. L'Istituto coopera con i Servizi Veterinari della Namibia fornendo supporto tecnico-scientifico e nel 2005, ha allestito un proprio Laboratorio di Virologia, presso il Central Veterinary Laboratory di Windhoek, nel quale, personale dell'Istituto e namibiano, in unita' di intenti, condividono le competenze diagnostiche e la ricerca scientifica. Scopo del seguente lavoro è descrivere le attività svolte nell'ambito di questo rapporto di collaborazione.

  18. In search of spring mires in Namibia: the Waterberg area revisited

    Directory of Open Access Journals (Sweden)

    A.P. Grootjans

    2015-07-01

    Full Text Available The scarcity of peatlands and mires in Namibia is well known. Peatlands have been found in the north, which is the wettest part of the country. In the 1930s, spring mires were reported by German geologists in the Waterberg area, which also has relatively high annual precipitation. This short note reports some field observations and a literature search for old documents that mention the occurrence of springs and spring mires in the Waterberg region. The search was done by IMCG members who visited the Waterberg area in August 2014. We found springs, but no real mires. However, we found remnants of what might have been a large spring mire similar to that reported by the German geologist Paul Range, who found “local spring mires (Quellmoore with a peat thickness of several metres in northern South-West Africa”. Whether or not our peat remnants were situated at the same site as the Range discovery could not be assessed. We compared the landscape position of the peat remnants and spring in the Waterberg area of Namibia with information from an ongoing ecohydrological study in the Waterberg area of Limpopo Province, South Africa.

  19. Evaluation of the audit committees of government ministries in Namibia: Their compositions, functions and regulations

    Directory of Open Access Journals (Sweden)

    Angela Winnie Kandandu

    2015-09-01

    Full Text Available The aim of the underlying study to this paper is to evaluate the audit committees in the government ministries in Namibia; by assessing their composition, the function and regulations that govern committees. The study used a qualitative approach of inquiry. A purposive sampling method was used as the researcher selected ministries with audit committees. Thematic and content analysis was used in this study. Both primary and secondary and data were used. On primary data, interviews were conducted and recorded with a voice recorder. Secondary data was during the review of existing literature on the subject. The study found that from the 4 government ministries with audit committees, only one ministry consisted of independent members as well as an independent chairperson, while 3 ministries are chaired by members within their organisations. There was clear evidence of lack of accounting / financial /auditing competence among the committee members. This trend is contrary to the best practice which requires that the chairperson of the audit committees be independent of the ministry as well as the members of the audit committee. The finding indicates possibility of lack of capacity to carry out the functions of audit committees; weak internal control systems; chances of conflict of interest and complacency due to the lack of independence. There is avenue for further research as more ministries in Namibia are now establishing their audit committees, especially as the Namibian Code of Corporate Governance (the NamCode gains more popularity among the public sector.

  20. A step too far? Making health equity interventions in Namibia more sufficient

    Directory of Open Access Journals (Sweden)

    Ithindi Taati

    2003-04-01

    Full Text Available Abstract Background Equality of health status is the health equity goal being pursued in developed countries and advocated by development agencies such as WHO and The Rockefeller Foundation for developing countries also. Other concepts of fair distribution of health such as equity of access to medical care may not be sufficient to equalise health outcomes but, nevertheless, they may be more practical and effective in advancing health equity in developing countries. Methods A framework for relating health equity goals to development strategies allowing progressive redistribution of primary health care resources towards the more deprived communities is formulated. The framework is applied to the development of primary health care in post-independence Namibia. Results In Namibia health equity has been advanced through the progressive application of health equity goals of equal distribution of primary care resources per head, equality of access for equal met need and equality of utilisation for equal need. For practical and efficiency reasons it is unlikely that health equity would have been advanced further or more effectively by attempting to implement the goal of equality of health status. Conclusion The goal of equality of health status may not be appropriate in many developing country situations. A stepwise approach based on progressive redistribution of medical services and resources may be more appropriate. This conclusion challenges the views of health economists who emphasise the need to select a single health equality goal and of development agencies which stress that equality of health status is the most important dimension of health equity.

  1. A Prototype Flood Early Warning SensorWeb System for Namibia

    Science.gov (United States)

    Sohlberg, R. A.; Mandl, D.; Frye, S. W.; Cappelaere, P. G.; Szarzynski, J.; Policelli, F.; van Langenhove, G.

    2010-12-01

    During the past two years, there have been extensive floods in the country of Namibia, Africa which have affected up to a quarter of the population. Via a collaboration between a group funded by the Earth Science Technology Office (ESTO) at NASA that has been performing various SensorWeb prototyping activities for disasters, the Department of Hydrology in Namibia and the United Nations Space-based Information for Disaster and Emergency Response (UN-SPIDER) , experiments were conducted on how to apply various satellite resources integrated into a SensorWeb architecture along with in-situ sensors such as river gauges and rain gauges into a flood early warning system. The SensorWeb includes a global flood model and a higher resolution basin specific flood model. Furthermore, flood extent and status is monitored by optical and radar types of satellites and integrated via some automation. We have taken a practical approach to find out how to create a working system by selectively using the components that provide good results. The vision for the future is to combine this with the country side dwelling unit data base to create risk maps that provide specific warnings to houses within high risk areas based on near term predictions. This presentation will show some of the highlights of the effort thus far plus our future plans.

  2. Molecular genetic insights on cheetah (Acinonyx jubatus) ecology and conservation in Namibia.

    Science.gov (United States)

    Marker, Laurie L; Pearks Wilkerson, Alison J; Sarno, Ronald J; Martenson, Janice; Breitenmoser-Würsten, Christian; O'Brien, Stephen J; Johnson, Warren E

    2008-01-01

    The extent and geographic patterns of molecular genetic diversity of the largest remaining free-ranging cheetah population were described in a survey of 313 individuals from throughout Namibia. Levels of relatedness, including paternity/maternity (parentage), were assessed across all individuals using 19 polymorphic microsatellite loci, and unrelated cheetahs (n = 89) from 7 regions were genotyped at 38 loci to document broad geographical patterns. There was limited differentiation among regions, evidence that this is a generally panmictic population. Measures of genetic variation were similar among all regions and were comparable with Eastern African cheetah populations. Parentage analyses confirmed several observations based on field studies, including 21 of 23 previously hypothesized family groups, 40 probable parent/offspring pairs, and 8 sibling groups. These results also verified the successful integration and reproduction of several cheetahs following natural dispersal or translocation. Animals within social groups (family groups, male coalitions, or sibling groups) were generally related. Within the main study area, radio-collared female cheetahs were more closely interrelated than similarly compared males, a pattern consistent with greater male dispersal. The long-term maintenance of current patterns of genetic variation in Namibia depends on retaining habitat characteristics that promote natural dispersal and gene flow of cheetahs.

  3. Resilience among older caregivers in rural Namibia: The role of financial status, social support and health.

    Science.gov (United States)

    Kalomo, Eveline Ndii; Lee, Kyoung Hag; Lightfoot, Elizabeth; Freeman, Rachel

    2018-04-23

    Namibia has one of the highest human immunodeficiency virus (HIV) prevalence rates and one of the highest rates of orphanhood in the world, and older caregivers provide much of the care to Namibians living with HIV and acquired immune deficiency syndrome (AIDS) (UNAIDS, 2014). In this study, the authors explore how financial status, social support, and health were related to the resilience of caregivers caring for people affected by HIV and AIDS in rural northern Namibia, Africa. Data were collected through a structured interview from (N = 147) caregivers from the Zambezi region. Findings from this study show that employment and physical health were significantly associated with increased resilience in older caregivers. Our findings point to the need for employment assistance and health services to improve the resilience of caregivers caring for people living with HIV and AIDS. We conclude that there is a need for more vigorous concerted efforts from public and private sector practitioners and policy makers to create more sustained formal employment opportunities and intervention programs aimed at improving the overall health of older HIV caregivers, especially those residing in rural HIV endemic communities in developing countries.

  4. Characteristics of ejecta and alluvial deposits at Meteor Crater, Arizona and Odessa Craters, Texas: Results from ground penetrating radar

    Science.gov (United States)

    Grant, J. A.; Schultz, P. H.

    1991-01-01

    Previous ground penetrating radar (GRP) studies around 50,000 year old Meteor Crater revealed the potential for rapid, inexpensive, and non-destructive sub-surface investigations for deep reflectors (generally greater than 10 m). New GRP results are summarized focusing the shallow sub-surfaces (1-2 m) around Meteor Crater and the main crater at Odessa. The following subject areas are covered: (1) the thickness, distribution, and nature of the contact between surrounding alluvial deposits and distal ejecta; and (2) stratigraphic relationships between both the ejecta and alluvium derived from both pre and post crater drainages. These results support previous conclusions indicating limited vertical lowering (less than 1 m) of the distal ejecta at Meteor Crater and allow initial assessment of the gradational state if the Odessa craters.

  5. In situ flash X-ray observation of projectile penetration processes and crater cavity growth in porous gypsum target analogous to low-density asteroids

    Science.gov (United States)

    Yasui, Minami; Arakawa, Masahiko; Hasegawa, Sunao; Fujita, Yukihiro; Kadono, Toshihiko

    2012-11-01

    Recent studies of impact craters formed on low-density asteroids led to the proposal of a new crater formation mechanism dominated by pore collapse and compaction. Thus, it is important to study the crater formation process associated with the projectile penetration on porous cohesive targets. Laboratory impact experiments were conducted for a porous gypsum target with porosity of 50%, and flash X-rays were used to visualize the interior of the target for in situ observation of crater formation and projectile penetration. Spherical projectiles made of three different materials, stainless steel, aluminum, and nylon were impacted at 1.9-2.4 km/s (low-velocity impact) and 5.6-6.4 km/s (high-velocity impact) by using a two-stage light-gas gun. Two imaging plates were used to take two X-ray images at a different delay time from the impact moment for one shot. Two types of crater cavity shape were found on the porous gypsum target, that is, penetration holes or hemispherical cavities, depending on the projectile size and density, and the impact velocity. The drag coefficient of a projectile was determined by measuring the penetration depth changing with time, and we found that it was closely related to the crater cavity shape: it was about 0.9 for a penetration hole, while it was 2.3-3.9 for a hemispherical cavity. This large value for a hemispherical cavity could have been caused by the deformation or the disruption of the projectile. The cratering efficiency, ρtVcr(t)/mp, was found to have a power law relationship to the scaling time for crater growth, πt = vit/rp, where vi is the impact velocity, rp is the projectile radius, and t is the time after the impact, and all data for stainless steel and aluminum projectiles merged completely and could be fitted by a power-law equation of ρtVcr(t)/mp=2.69×10-1πt1.10. Furthermore, the scaled crater volume, πV = Vcr_finalρt/mp, where Vcr_final is the final crater cavity volume, ρt is the target density, and mp is the

  6. Revisiting the Importance of Knowledge: From Namibia, a Case for Promoting Knowledge by Campaigns to Reduce Stigma

    Science.gov (United States)

    Chung, Adrienne H.; Rimal, Rajiv N.

    2015-01-01

    Reducing stigma against people living with HIV is key to encouraging HIV testing, which in turn is an important component in the treatment-as-prevention approach. We analyzed nationally representative survey data of participants aged 15 years and older in Namibia (N = 4,300) to determine whether knowledge about HIV and self-efficacy to protect…

  7. Experiences of Student Support in the Distance Mode Bachelor of Nursing Science Degree at the University of Namibia

    Science.gov (United States)

    Du Plessis, Carol Denise; Alexander, Lucy; Ashipala, Daniel Opotamutale; Kamenye, Esther

    2016-01-01

    The aim of this study was to understand the way in which students experienced the support services offered by the University of Namibia's distance education unit--the Centre for External Studies. The study explored students' experiences and their perceptions of the administrative, social and academic support services provided by the University of…

  8. Communicative Approaches To Teaching English in Namibia: The Issue of Transfer of Western Approaches To Developing Countries.

    Science.gov (United States)

    O'Sullivan, Margo C.

    2001-01-01

    Examines Namibia's communicative approach to teaching English speaking and listening skills by exploring the extent to which this approach is appropriate to the Namibian context. Raises the issue of transfer, specifically that communicative approaches are transferable to the Namibian context if they are simplified and adequate prescriptive…

  9. Automated detection of malaria pigment: feasibility for malaria diagnosing in an area with seasonal malaria in northern Namibia

    NARCIS (Netherlands)

    de Langen, Adrianus J.; van Dillen, Jeroen; de Witte, Piet; Mucheto, Samson; Nagelkerke, Nico; Kager, Piet

    2006-01-01

    OBJECTIVE: To evaluate the feasibility of automated malaria detection with the Cell-Dyn 3700 (Abbott Diagnostics, Santa Clara, CA, USA) haematology analyser for diagnosing malaria in northern Namibia. METHODS: From April to June 2003, all patients with a positive blood smear result and a subset of

  10. Relating sedimentary processes in the Bagnold Dunes to the development of crater basin aeolian stratification

    Science.gov (United States)

    Ewing, R. C.; Lapotre, M. G. A.; Lewis, K. W.; Day, M. D.; Stein, N.; Rubin, D. M.; Sullivan, R. J., Jr.; Banham, S.; Thomas, N. M.; Lamb, M. P.; Gupta, S.; Fischer, W. W.

    2017-12-01

    Wind-blown sand dunes are ubiquitous on the surface of Mars and are a recognized component of the martian stratigraphic record. Our current knowledge of the aeolian sedimentary processes that determine dune morphology, drive dune dynamics, and create aeolian cross-stratification are based upon orbital studies of ripple and dune morphodynamics, rover observations of stratification on Mars, Earth analogs, and experimental and theoretical studies of sand movement under martian conditions. Exploration of the Bagnold Dunes by the Curiosity Rover in Gale Crater, Mars provided the first opportunity to make in situ observations of martian dunes from the grain-to-dune scale. We used the suite of cameras on Curiosity, including Navigation Camera, Mast Camera, and Mars Hand Lens Imager. We measured grainsize and identified sedimentary processes similar to processes on terrestrial dunes, such as grainfall, grainflow, and impact ripples. Impact ripple grainsize had a median of 0.103 mm. Measurements of grainflow slopes indicate a relaxation angle of 29° and grainfall slopes indicate critical angles of at least 32°. Dissimilar to terrestrial dunes, large, meter-scale ripples form on all slopes of the dunes. The ripples form both sinuous and linear crestlines, have symmetric and asymmetric profiles, range in height between 12cm and 28cm, and host grainfall, grainflow, and impact ripples. The largest ripples are interpreted to integrate the annual wind cycle within the crater, whereas smaller large ripples and impact ripples form or reorient to shorter term wind cycling. Assessment of sedimentary processes in combination with dune type across the Bagnold Dunes shows that dune-field pattern development in response to a complex crater-basin wind regime dictates the distribution of geomorphic processes. From a stratigraphic perspective, zones of highest potential accumulation correlate with zones of wind convergence, which produce complex winds and dune field patterns thereby

  11. Investigation of plasma ablation and crater formation processes in the Prague Asterix Laser System laser facility

    Czech Academy of Sciences Publication Activity Database

    Borodziuk, S.; Kasperczuk, A.; Pisarczyk, T.; Gus'kov, S.; Ullschmied, Jiří; Králiková, Božena; Rohlena, Karel; Skála, Jiří; Pisarczyk, P.; Kálal, M.

    2004-01-01

    Roč. 34, č. 1 (2004), s. 31-42 ISSN 0078-5466 R&D Projects: GA MŠk LN00A100 Grant - others:HPRI-CT(XX) 1999-00053 Institutional research plan: CEZ:AV0Z2043910; CEZ:AV0Z1010921 Source of funding: R - rámcový projekt EK Keywords : laser-produced plasma * interferometric measurements * crater Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.308, year: 2004

  12. On a possible parent crater for Australasian tektites: Geochemical, isotopic, geographical and other constraints

    Czech Academy of Sciences Publication Activity Database

    Mizera, Jiří; Řanda, Zdeněk; Kameník, Jan

    2016-01-01

    Roč. 154, MAR (2016), s. 123-137 ISSN 0012-8252 R&D Projects: GA ČR GA13-22351S; GA MŠk(CZ) LM2011019 Institutional support: RVO:67985891 ; RVO:61389005 Keywords : Australasian tektite * Parent crater * Geochemical analysis * Isotope analysis * Chinese loess * Badain Jaran Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders; DD - Geochemistry (USMH-B) Impact factor: 7.051, year: 2016

  13. Payments for Environmental Services as source of development funding for small-scale farmers in northern Namibia: preliminary results

    Science.gov (United States)

    Angombe, Simon; Bloemertz, Lena; Käch, Simon; Asino, Josefina; Kuhn, Nikolaus J.

    2013-04-01

    Studies in Africa suggest that improving Soil Organic Carbon (SOC) on cropland soils increases yields, but also offers the opportunity of earning carbon credits. Further potential for earning carbon credits and generating Payments for Environmental Services (PES) lies in an integrated approach to landscape carbon management, including shrubland and pasture used for grazing and timber supply. These studies indicate that funds raised from PES could be used to foster the development of small-scale farming in northern Namibia. However, the limited information on soil quality and the rationale for particular soil management and land use practices applied by small-scale farmers in Namibia prohibits a conclusive assessment of the potential of Payment for PES as a source of income or funding opportunity for development initiatives in Northern Central Regions of Namibia. Therefore, the aim of this study is the identification of potential intervention mechanisms to improve the livelihood of small scale-farmers and reducing land degradation with the support of PES in the communal regions of northern Namibia. The work in Namibia aimed at identifying existing soil management and land use practices as well as soil quality, including carbon stocks, on land used by small-scale farmers in the densely populated northern central region. The main objective of the first part of the field work was to develop an overview of farming practices and soil quality as well as sampling and interviewing approaches. Four settlements were selected for the field work based on their distance to the urbanized road corridor between Oshakati and the Angolan border. Initial results confirm the potential to increase productivity on land used by small-scale farmers as well as the opportunity to develop landscape carbon stocks. However, limits to earning PES might be the lack of a market, and thus incentive for the farmers, to shift from subsistence to commercial fa