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Sample records for sheets earth venus

  1. Field reversing magnetotail current sheets: earth, Venus, and Comet Giacobini-Zinner

    International Nuclear Information System (INIS)

    McComas, D.J.

    1986-09-01

    This dissertation examines the field reversing magnetotail current sheets at the earth, Venus, and Comet Giacobini-Zinner. In the near earth study a new analysis technique is developed to calculate the detailed current density distributions within the cross tail current sheet for the first time. This technique removes the effects of a variable sheet velocity by inverting intersatellite timings between the co-orbiting satellites ISEE-1 and -2. Case studies of three relatively geomagnetically quiet crossings are made; sheet thicknesses and peak current densities are ∼1-5 x 10 4 km and ∼5-50 nA/m 2 . Current density distributions reveal a high density central region, lower density shoulders, and considerable fine structure throughout. In the Venus study another new analysis technique is developed to reconstruct the average tail configuration from a correlation between field magnitude and draping angle in a large statistical data set. In the comet study, high resolution magnetic field and plasma electron data from the ICE traversal of Giacobini-Zinner are combined for the first time to determine the tail/current sheet geometry and calculate certain important but unmeasured local ion and upstream properties. Pressure balance across the tail gives ion temperatures and betas of ∼1.2 x 10 5 K and ∼40 in the center of the current sheet to ∼1 x 10 6 K and ∼3 in the outer lobes. Axial stress balance shows that the velocity shear upstream near the nucleus is >6 (∼1 at ICE), and that a region of strongly enhanced mass loading (ion source rate ∼24 times that upstream from lobes) exists upstream from the current sheet. The integrated downtail mass flux is ∼2.6 x 10 26 H 2 O+/sec, which is only ∼1% of the independently determined total cometary efflux. 79 refs., 37 figs

  2. Field reversing magnetotail current sheets: earth, Venus, and Comet Giacobini-Zinner

    Energy Technology Data Exchange (ETDEWEB)

    McComas, D.J.

    1986-09-01

    This dissertation examines the field reversing magnetotail current sheets at the earth, Venus, and Comet Giacobini-Zinner. In the near earth study a new analysis technique is developed to calculate the detailed current density distributions within the cross tail current sheet for the first time. This technique removes the effects of a variable sheet velocity by inverting intersatellite timings between the co-orbiting satellites ISEE-1 and -2. Case studies of three relatively geomagnetically quiet crossings are made; sheet thicknesses and peak current densities are approx.1-5 x 10/sup 4/ km and approx.5-50 nA/m/sup 2/. Current density distributions reveal a high density central region, lower density shoulders, and considerable fine structure throughout. In the Venus study another new analysis technique is developed to reconstruct the average tail configuration from a correlation between field magnitude and draping angle in a large statistical data set. In the comet study, high resolution magnetic field and plasma electron data from the ICE traversal of Giacobini-Zinner are combined for the first time to determine the tail/current sheet geometry and calculate certain important but unmeasured local ion and upstream properties. Pressure balance across the tail gives ion temperatures and betas of approx.1.2 x 10/sup 5/ K and approx.40 in the center of the current sheet to approx.1 x 10/sup 6/ K and approx.3 in the outer lobes. Axial stress balance shows that the velocity shear upstream near the nucleus is >6 (approx.1 at ICE), and that a region of strongly enhanced mass loading (ion source rate approx.24 times that upstream from lobes) exists upstream from the current sheet. The integrated downtail mass flux is approx.2.6 x 10/sup 26/ H/sub 2/O+/sec, which is only approx.1% of the independently determined total cometary efflux. 79 refs., 37 figs.

  3. Venus: A contrast in evolution to Earth

    International Nuclear Information System (INIS)

    Kaula, W.M.

    1990-01-01

    Of the planets, Venus and Earth are by far the most similar in primary properties, yet they differ markedly in secondary properties. A great impact into Earth is believed to have created its moon and removed its atmosphere; the lack of such an impact into Venus apparently led to a greatly differing atmospheric evolution. The lack of an ocean on Venus prevents the recycling of volatiles and inhibits subduction, so that its crust is probable more voluminous than Earth's, although distorted and quite variable in thickness. Venus's upper mantle appears to be depleted in both volatiles and energy sources because, in addition to the lack of volatile recycling, melts of mantel rocks are more dense than their solid matrix at pressures above 8 gigapascals and hence sink if they occur at depths below 250 kilometers. Appreciable energy sources persist at great depths to sustain the few great mountain complexes. The greatest current problem is reconciling the likelihood of a voluminous crust with indications of considerable strength at shallow depths of 20 to 100 kilometers

  4. Development of Venus Balloon Seismology Missions Through Earth Analog Experiments

    Science.gov (United States)

    Krishnamoorthy, S.; Komjathy, A.; Cutts, J. A.; Pauken, M. T.; Garcia, R. F.; Mimoun, D.; Jackson, J. M.; Kedar, S.; Smrekar, S. E.; Hall, J. L.

    2017-11-01

    The study of a planet’s seismic activity is central to the understanding of its internal structure. We discuss advances made through Earth analog testing for performing remote seismology on Venus using balloons floated in the mid-atmosphere.

  5. Earth-type planets (Mercury, Venus, and Mars)

    Science.gov (United States)

    Marov, M. Y.; Davydov, V. D.

    1975-01-01

    Spacecraft- and Earth-based studies on the physical nature of the planets Mercury, Venus, and Mars are reported. Charts and graphs are presented on planetary surface properties, rotational parameters, atmospheric compositions, and astronomical characteristics.

  6. The Venus-Earth-Jupiter spin-orbit coupling model

    Science.gov (United States)

    Wilson, I. R. G.

    2013-12-01

    A Venus-Earth-Jupiter spin-orbit coupling model is constructed from a combination of the Venus-Earth-Jupiter tidal-torquing model and the gear effect. The new model produces net tangential torques that act upon the outer convective layers of the Sun with periodicities that match many of the long-term cycles that are found in the 10Be and 14C proxy records of solar activity.

  7. How did Earth not End up like Venus?

    Science.gov (United States)

    Jellinek, M.; Lenardic, A.; Weller, M. B.

    2017-12-01

    Recent geodynamic calculations show that terrestrial planets forming with a chondritic initial bulk composition at order 1 AU can evolve to be either "Earth-like" or "Venus-like": Both mobile- and stagnant-lid tectonic regimes are permitted, neither solution is an explicitly stronger attractor and effects related to differences in Sun-Earth distance are irrelevant. What factors might then cause the thermal evolutionary paths of Earth and Venus to diverge dynamically at early times? At what point in Earth's evolution did plate tectonics emerge and when and how did this tectonic mode gain sufficient resilience to persist over much of Earth's evolution? What is the role of volatile cycling and climate: To what extent have the stable climate of Earth and the greenhouse runaway climate of Venus enforced their distinct tectonic regimes over time? In this talk I will explore some of the mechanisms potentially governing the evolutionary divergence of Earth and Venus. I will first review observational constraints that suggest that Earth's entry into the current stable plate tectonic mode was far from assured by 2 Ga. Next I will discuss how models have been used to build understanding of some key dynamical controls. In particular, the probability of "Earth-like" solutions is affected by: 1) small differences in the initial concentrations of heat producing elements (i.e., planetary initial conditions); 2) long-term climate change; and 3) the character of a planet's early evolutionary path (i.e., tectonic hysteresis).

  8. Impact-induced atmospheres and oceans on earth and Venus

    Science.gov (United States)

    Matsui, T.; Abe, Y.

    1986-01-01

    The effects of planetesimal-impact induced atmosphere formation on the earth and Venus are modeled to gain an indication why the two planets, at relatively equal distances from the sun, evolved so differently. Both planets gained approximately 10 to the 21 kg of water from the impacts. The water mass of the accreting planetesimals would have remained, initially, as a hot atmosphere. A two-stream approximation is defined for the temperature profile of a plane parallel atmosphere in radiative equilibrium. It is shown that the Venus atmosphere did not, as happened on earth, condense into a hot ocean after the impact epoch. Instead, the greenhouse effect caused the Venus equilibrium thermal structure to remain higher than the vapor pressure, keepinig the atmosphere in a vapor phase until the vapor dissociated and H2 atoms eventually escaped into space.

  9. Simulation of Venus Atmosphere Dynamics With an Earth Climate GCM

    Science.gov (United States)

    Parish, H. F.; Schubert, G.; Covey, C. C.; Grossman, A.

    2008-12-01

    We describe the results of initial simulations of the Venusian atmosphere, using the Community Atmosphere Model (CAM). The CAM model is a descendant of the NCAR Community Climate Model, and is defined as one of two "high-end" models designated by the US Climate Change Science Program for basic research. It may also be the most widely used 3D climate model in the US. CAM has grown substantially in complexity and Earth-specificity since the original version was released in 1983, and many of these Earth based physics parameterizations need to be adjusted to simulate the Venus atmosphere. Other groups are adapting CAM to simulate the atmospheres of Mars and Titan, thereby promising CAM simulation for all four terrestrial planets known to have substantial atmospheres. Studying these worlds together will provide calibration of Earth-centric studies of climate changes like global warming. It will also provide context for future searches for Earth-like planets orbiting other stars. In this work we will focus on Venus. The Venus atmosphere represents an extreme environment, strongly influenced by the greenhouse effect, and studying the Venus atmosphere may therefore be relevant to the possible future direction of the Earth's climate. The dynamical processes which occur in the Venusian atmosphere are not well understood, including the cause of the strong superrotation of the atmosphere, in which the planetary surface rotates with a period of around 243 days, but the atmosphere near the cloud tops has a rotational period of only around 4 days. We show the results of initial simulations of the dynamics of the Venus atmosphere, using a version of the CAM model with most of the Earth related processes, such as the cloud physics, removed. A simplified form of heating has been applied, similar to the thermal forcing approach used recently by other authors. We investigate the sensitivity of the model results to changes in the physics parameterizations we have used, including

  10. Earth's Atmospheric Electricity Parameter Response During Venus Transit

    Directory of Open Access Journals (Sweden)

    Syam Sundar De

    2015-01-01

    Full Text Available Venus transited across the Sun on 06 June 2012, introducing significant contribution to the tidal characteristics of the solar atmosphere. _ atmosphere was perturbed due to an anomalous Coronal Mass Ejection (CME and γ-radiationγ-radiation influenced by the solar tide due to Venus transit, thereby the Earth-ionosphere waveguide characteristics were changed. In this anomalous situation we measured some atmospheric electricity parameters such as Schumann resonance (SR amplitude, very low frequency (VLF sferics, subionospheric transmitted signals and the point discharge current (PDC along with the vertical electrical potential gradient (PG at the ground surface on the day of transit. The results showed some remarkable variations during the transit as well as pre- and post-transit periods. The observed anomalies in the recorded data were interpreted in terms of the anomalous solar tidal effects initiated due to Venus transit.

  11. Topography of Venus and earth - A test for the presence of plate tectonics

    Science.gov (United States)

    Head, J. W.; Yuter, S. E.; Solomon, S. C.

    1981-01-01

    Comparisons of earth and Venus topography by use of Pioneer/Venus radar altimetry are examined. Approximately 93% of the Venus surface has been mapped with a horizontal resolution of 200 km and a vertical resolution of 200 m. Tectonic troughs have been indicated in plains regions which cover 65% of Venus, and hypsometric comparisons between the two planets' elevation distributions revealed that while the earth has a bimodal height distribution, Venus displays a unimodal configuration, with 60% of the planet surface within 500 m of the modal planet radius. The effects of mapping the earth at the same resolution as the Venus observations were explored. Continents and oceans were apparent, and although folded mountains appeared as high spots, no indications of tectonic activity were discernible. A NASA Venus Orbiting Imaging radar is outlined, which is designed to detect volcanoes, folded mountain ranges, craters, and faults, and thereby allow definition of possible plate-tectonic activity on Venus.

  12. Earthlike planets: Surfaces of Mercury, Venus, earth, moon, Mars

    Science.gov (United States)

    Murray, B.; Malin, M. C.; Greeley, R.

    1981-01-01

    The surfaces of the earth and the other terrestrial planets of the inner solar system are reviewed in light of the results of recent planetary explorations. Past and current views of the origin of the earth, moon, Mercury, Venus and Mars are discussed, and the surface features characteristic of the moon, Mercury, Mars and Venus are outlined. Mechanisms for the modification of planetary surfaces by external factors and from within the planet are examined, including surface cycles, meteoritic impact, gravity, wind, plate tectonics, volcanism and crustal deformation. The origin and evolution of the moon are discussed on the basis of the Apollo results, and current knowledge of Mercury and Mars is examined in detail. Finally, the middle periods in the history of the terrestrial planets are compared, and future prospects for the exploration of the inner planets as well as other rocky bodies in the solar system are discussed.

  13. Venus

    CERN Document Server

    Payment, Simone

    2017-01-01

    This straightforward but fascinating book takes a close look at Venus and shows young people just how different our neighboring planet is from our own. Known as the hottest planet, Venus is an example of the greenhouse effect to the extreme. Young readers will take a tour beneath the sulfur dioxide clouds and see the planet's surface up close with images taken by the Magellan and the Venus Express missions. This book will surely fascinate any young person interested in alien worlds.

  14. Comparison of dayside current layers in Venus' ionosphere and earth's equatorial electrojet

    Science.gov (United States)

    Cole, Keith D.

    1993-01-01

    The major physical aspects of the equatorial electrojet of Earth and the dayside ionospheric current layers of Venus are compared, viz., the electric current intensity and total current, roles of electric field, pressure and gravity, diffusion time scales, and the Bernouille effect. The largest potential differences, of the order of 10 volts, horizontally across the dayside ionosphere of Venus, have important implications for possible dynamo action in the Venus ionosphere and the application of an electric field from the lower atmosphere or from the solar wind. An upper limit to the horizontal scale of vertical magnetic fields in the Venus ionosphere is estimated thereby for the first time. New upper limits on the velocity in, and thickness of, a possible S layer at Venus are presented. If an S layer exists, it is only for extreme conditions of the solar wind. A mechanism for formation of magnetic ropes in the Venus ionosphere is also proposed.

  15. Titan is to Earth's Hydrological Cycle what Venus is to its Greenhouse Effect

    Science.gov (United States)

    Lorenz, R. D.

    2012-06-01

    Titan serves as an extreme extrapolation of Earth's possible present trend toward more violent rainstorms interspersed by long droughts, much as Venus has acted as a bogeyman to illustrate the perils of enhanced greenhouse warming.

  16. Thermal and magmatic processes on Venus, Earth, and Mars

    Science.gov (United States)

    Hauck, Steven Arthur, II

    Venus, Mars, and Earth present unique opportunities and laboratories for studying the thermal and magmatic evolution of terrestrial planets. Key observations from the Magellan mission to Venus were that the surface hosts a mere ˜1000 impact craters and that more than 65% of the surface is covered by volcanic plains. A popular hypothesis suggested the plains were emplaced in 10--100 Myr. However, analysis of the population of impact craters with respect to plains geology suggests that magmatism associated with plains emplacement lasted approximately half the average surface age of the planet, almost 500 Myr. Martian thermo-magmatic evolution is constrained by estimates that the crust was predominantly emplaced within the first 500 Myr, has an average crustal thickness of 50--100 km, and observations that imply that the planet had an internally generated magnetic field early, but is lacking one today. Coupling of a simple, parameterized model of mantle convection to a batch-melting model for peridotite allows reconstruction of reasonable estimates of the conditions and evolutionary path of the crust and mantle. Key elements of the nominal model are inclusion of the energetics of melting, a wet (weak) mantle rheology, self-consistent fractionation of heat producing elements to the crust, a near chondritic abundance of those same elements, and a core with 15 wt% sulfur. Inclusion of the latent heat of melting mantle material is crucial for constraining thermal and magmatic history of Mars. The nominal model results in an average crustal thickness of 67 km that was 75% emplaced by 4 Ga. The subduction of terrestrial oceanic lithosphere is an important heat transfer process related to plate tectonics. The source of deep focus earthquakes may be tied to the thermal structure of downgoing slabs and the potential for catastrophic transformation of metastable olivine below the 410 km discontinuity. The first models of subducting slabs that include thermal conductivity that

  17. Venus-Earth-Mars: Comparative Climatology and the Search for Life in the Solar System

    Science.gov (United States)

    Launius, Roger D.

    2012-01-01

    Both Venus and Mars have captured the human imagination during the twentieth century as possible abodes of life. Venus had long enchanted humans—all the more so after astronomers realized it was shrouded in a mysterious cloak of clouds permanently hiding the surface from view. It was also the closest planet to Earth, with nearly the same size and surface gravity. These attributes brought myriad speculations about the nature of Venus, its climate, and the possibility of life existing there in some form. Mars also harbored interest as a place where life had or might still exist. Seasonal changes on Mars were interpreted as due to the possible spread and retreat of ice caps and lichen-like vegetation. A core element of this belief rested with the climatology of these two planets, as observed by astronomers, but these ideas were significantly altered, if not dashed during the space age. Missions to Venus and Mars revealed strikingly different worlds. The high temperatures and pressures found on Venus supported a “runaway greenhouse theory,” and Mars harbored an apparently lifeless landscape similar to the surface of the Moon. While hopes for Venus as an abode of life ended, the search for evidence of past life on Mars, possibly microbial, remains a central theme in space exploration. This survey explores the evolution of thinking about the climates of Venus and Mars as life-support systems, in comparison to Earth. PMID:25371106

  18. Venus-Earth-Mars: Comparative Climatology and the Search for Life in the Solar System

    Directory of Open Access Journals (Sweden)

    Roger D. Launius

    2012-09-01

    Full Text Available Both Venus and Mars have captured the human imagination during the twentieth century as possible abodes of life. Venus had long enchanted humans—all the more so after astronomers realized it was shrouded in a mysterious cloak of clouds permanently hiding the surface from view. It was also the closest planet to Earth, with nearly the same size and surface gravity. These attributes brought myriad speculations about the nature of Venus, its climate, and the possibility of life existing there in some form. Mars also harbored interest as a place where life had or might still exist. Seasonal changes on Mars were interpreted as due to the possible spread and retreat of ice caps and lichen-like vegetation. A core element of this belief rested with the climatology of these two planets, as observed by astronomers, but these ideas were significantly altered, if not dashed during the space age. Missions to Venus and Mars revealed strikingly different worlds. The high temperatures and pressures found on Venus supported a “runaway greenhouse theory,” and Mars harbored an apparently lifeless landscape similar to the surface of the Moon. While hopes for Venus as an abode of life ended, the search for evidence of past life on Mars, possibly microbial, remains a central theme in space exploration. This survey explores the evolution of thinking about the climates of Venus and Mars as life-support systems, in comparison to Earth.

  19. Venus-Earth-Mars: comparative climatology and the search for life in the solar system.

    Science.gov (United States)

    Launius, Roger D

    2012-09-19

    Both Venus and Mars have captured the human imagination during the twentieth century as possible abodes of life. Venus had long enchanted humans-all the more so after astronomers realized it was shrouded in a mysterious cloak of clouds permanently hiding the surface from view. It was also the closest planet to Earth, with nearly the same size and surface gravity. These attributes brought myriad speculations about the nature of Venus, its climate, and the possibility of life existing there in some form. Mars also harbored interest as a place where life had or might still exist. Seasonal changes on Mars were interpreted as due to the possible spread and retreat of ice caps and lichen-like vegetation. A core element of this belief rested with the climatology of these two planets, as observed by astronomers, but these ideas were significantly altered, if not dashed during the space age. Missions to Venus and Mars revealed strikingly different worlds. The high temperatures and pressures found on Venus supported a "runaway greenhouse theory," and Mars harbored an apparently lifeless landscape similar to the surface of the Moon. While hopes for Venus as an abode of life ended, the search for evidence of past life on Mars, possibly microbial, remains a central theme in space exploration. This survey explores the evolution of thinking about the climates of Venus and Mars as life-support systems, in comparison to Earth.

  20. VenSAR on EnVision: Taking earth observation radar to Venus

    Science.gov (United States)

    Ghail, Richard C.; Hall, David; Mason, Philippa J.; Herrick, Robert R.; Carter, Lynn M.; Williams, Ed

    2018-02-01

    Venus should be the most Earth-like of all our planetary neighbours: its size, bulk composition and distance from the Sun are very similar to those of Earth. How and why did it all go wrong for Venus? What lessons can be learned about the life story of terrestrial planets in general, in this era of discovery of Earth-like exoplanets? Were the radically different evolutionary paths of Earth and Venus driven solely by distance from the Sun, or do internal dynamics, geological activity, volcanic outgassing and weathering also play an important part? EnVision is a proposed ESA Medium class mission designed to take Earth Observation technology to Venus to measure its current rate of geological activity, determine its geological history, and the origin and maintenance of its hostile atmosphere, to understand how Venus and Earth could have evolved so differently. EnVision will carry three instruments: the Venus Emission Mapper (VEM); the Subsurface Radar Sounder (SRS); and VenSAR, a world-leading European phased array synthetic aperture radar that is the subject of this article. VenSAR will obtain images at a range of spatial resolutions from 30 m regional coverage to 1 m images of selected areas; an improvement of two orders of magnitude on Magellan images; measure topography at 15 m resolution vertical and 60 m spatially from stereo and InSAR data; detect cm-scale change through differential InSAR, to characterise volcanic and tectonic activity, and estimate rates of weathering and surface alteration; and characterise of surface mechanical properties and weathering through multi-polar radar data. These data will be directly comparable with Earth Observation radar data, giving geoscientists unique access to an Earth-sized planet that has evolved on a radically different path to our own, offering new insights on the Earth-sized exoplanets across the galaxy.

  1. Global Reference Atmospheric Models, Including Thermospheres, for Mars, Venus and Earth

    Science.gov (United States)

    Justh, Hilary L.; Justus, C. G.; Keller, Vernon W.

    2006-01-01

    This document is the viewgraph slides of the presentation. Marshall Space Flight Center's Natural Environments Branch has developed Global Reference Atmospheric Models (GRAMs) for Mars, Venus, Earth, and other solar system destinations. Mars-GRAM has been widely used for engineering applications including systems design, performance analysis, and operations planning for aerobraking, entry descent and landing, and aerocapture. Preliminary results are presented, comparing Mars-GRAM with measurements from Mars Reconnaissance Orbiter (MRO) during its aerobraking in Mars thermosphere. Venus-GRAM is based on the Committee on Space Research (COSPAR) Venus International Reference Atmosphere (VIRA), and is suitable for similar engineering applications in the thermosphere or other altitude regions of the atmosphere of Venus. Until recently, the thermosphere in Earth-GRAM has been represented by the Marshall Engineering Thermosphere (MET) model. Earth-GRAM has recently been revised. In addition to including an updated version of MET, it now includes an option to use the Naval Research Laboratory Mass Spectrometer Incoherent Scatter Radar Extended Model (NRLMSISE-00) as an alternate thermospheric model. Some characteristics and results from Venus-GRAM and Earth-GRAM thermospheres are also presented.

  2. The effect of recent Venus transit on Earth’s atmosphere

    Directory of Open Access Journals (Sweden)

    H. P. Sardar

    2006-06-01

    Full Text Available Some experiments on June 8, 2004, the day of transit of Venus across the Sun, were undertaken at Kolkata (latitude: 22°34lN to observe the effect, if any, of transit of Venus on FWF, ELF and VLF amplitudes. The result shows a good correlation between their temporal variations during the transit. The observation was unbelievable as the Venus subtends only 1/32th of the cone subtended by Sun on Earth. This anomaly may be explained on the assumption that the height of Venusian atmosphere with high content of CO2, and nitrogen which absorbs electromagnetic and corpuscular radiations from Sun, depleting the solar radiation reaching the Earth to a considerable extent. As a result, relevant parameters of Earth’s atmosphere are modulated and here we show how these changes are reflected in identical behaviour of fair weather field and ELF and VLF spectra.

  3. Upstream waves at Mercury, Venus and earth - Comparison of the properties of one Hertz waves

    Science.gov (United States)

    Orlowski, D. S.; Crawford, G. K.; Russell, C. T.

    1990-01-01

    Previous studies have shown that the Venus foreshock region contains low-frequency upstream waves similar to those in the terrestrial foreshock, but perhaps with different amplitudes than at earth. This paper compares the properties of a second class of upstream waves, analogous to the so-called 1 Hz waves at earth. The waves observed at Mercury, Venus, and earth have very similar properties, i.e., propagation angles less than 55 degrees to the magnetic field and less than 35 degrees to the solar wind flow direction. The waves occur exclusively on the field lines connected to the bow shock. They are most commonly left-hand elliptically polarized with similar fractional amplitudes, approximately 0.1 of the background field strength. Their amplitudes decrease with increasing distance from the shock. The observed frequencies are similar for Mercury, Venus, and earth when scaled by the interplanetary magnetic field. If, as generally assumed at earth, these waves arise in regions of backstreaming electrons, these results imply that similar electron foreshocks occur at earth, Venus and Mercury despite differences in bow shock size and the nature of the obstacle to the solar wind.

  4. Divergent Evolution Among Earth-like Planets: The Case for Venus Exploration

    Science.gov (United States)

    Crisp, D.; Allen, M. A.; Anicich, V. G.; Arvidson, R. E.; Atreya, S. K.; Baines, K. H.; Banerdt, W. B.; Bjoraker, G. L.; Bougher, S. W.; Campbell, B. A.; Carlson, R. W.; Chin, G.; Chutjian, A.; Clancy, R. T.; Clark, B. C.; Cravens, T. E.; del Genio, A. D.; Esposito, L. W.; Fegley, B.; Flasar, M.; Fox, J. L.; Gierasch, P. J.; Goody, R. M.; Grinspoon, D. H.; Gulkis, S.; Hansen, V. L.; Herrick, R. R.; Huestis, D. L.; Hunten, D. M.; Janssen, M. A.; Jenkins, J.; Johnson, C. L.; Keating, G. M.; Kliore, A. J.; Limaye, S. S.; Luhmann, J. G.; Lunine, J. I.; Mahaffy, P.; McGovern, P. J.; Meadows, V. S.; Mills, F. P.; Niemann, H. B.; Owen, T. C.; Oyama, K. I.; Pepin, R. O.; Plaut, J. J.; Reuter, D. C.; Richardson, M. I.; Russell, C. T.; Saunders, R. S.; Schofield, J. T.; Schubert, G.; Senske, D. A.; Shepard, M. K.; Slanger, T. G.; Smrekar, S. E.; Stevenson, D. J.; Titov, D. V.; Ustinov, E. A.; Young, R. E.; Yung, Y. L.

    2002-08-01

    The planet Venus is our most Earth-like neighbor in size, mass, and distance from the sun. In spite of these similarities, and the intense scrutiny that it received early in the space age, the Venus surface and atmosphere are characterized by some of the most enigmatic features seen anywhere in the solar system. A reinvigorated Venus exploration program is essential to the development of a comprehensive understanding of the origin and evolution of Earth-like terrestrial planets. The present NASA inner planets strategy, which focuses exclusively on Mars, will provide an incomplete, and possibly misleading description of processes that produce these objects. If Venus-like terrestrial planets are common, this approach will also impede efforts to interpret observations of extrasolar terrestrial planets, which are expected to become available by the end of the decade. Here, we propose a Venus exploration program that has been designed to explain the origin and divergent evolution of the interiors, surfaces, and atmospheres of the terrestrial planets in our solar system, and provide greater insight into the conditions that may affect the habitability of terrestrial planets in other solar systems.

  5. Plume-induced subduction and accretion on present-day Venus and Archean Earth

    Science.gov (United States)

    Davaille, A.; Smrekar, S. E.; Sibrant, A.; Mittelstaedt, E. L.

    2017-12-01

    Plate tectonics is responsible for the majority of Earth's heat loss, cycling of volatiles between the atmosphere and interior, recycling in the mantle of most of the surface plates, and possibly even for maintaining habitability. Despite its similarity in size and bulk density to Earth, Venus lacks plate tectonics today, and its mode of operation remains debated. Using laboratory experiments in colloidal dispersion which brittle viscosity-elasto-plastic rheology, we recently showed that plume-induced subduction could be operating nowadays on Venus. The experimental fluids were heated from below to produce upwelling plumes, which in turn produced tensile fractures in the lithosphere-like skin that formed on the upper surface. Plume material upwelling through the fractures then spread above the skin, analogous to volcanic flooding, and lead to bending and eventual subduction of the skin along arcuate segments. These segments are analogous to the semi-circular trenches seen on large coronae. Scaling analysis suggests that this regime with limited, plume-induced subduction is favored by a hot lithosphere, such as that found on early Earth or present-day Venus. Moreover, in this regime, subduction proceeds primarily by roll-back and the coronae expands through time at velocity that could reach 10 cm/yr. A second set of experiments focusing on accretion processes suggests that accretion dynamics depends on the strength of the lithosphere, as well as the spreading velocity. Venus hot surface temperature would act to decrease the lithosphere strength, and therefore weaken the ridge axis, that would become highly unstable, showing large sinuosity and producing a number of micro-plates. These plume, subduction, and accretion characteristics explain well the features seen in Artemis coronae, the largest coronae on Venus.

  6. The twin sister planets Venus and Earth why are they so different?

    CERN Document Server

    Malcuit, Robert J

    2014-01-01

    This book explains how it came to be that Venus and Earth, while very similar in chemical composition, zonation, size and heliocentric distance from the Sun, are very different in surface environmental conditions. It is argued here that these differences can be accounted for by planetoid capture processes and the subsequent evolution of the planet-satellite system. Venus captured a one-half moon-mass planetoid early in its history in the retrograde direction and underwent its "fatal attraction scenario" with its satellite (Adonis). Earth, on the other hand, captured a moon-mass planetoid (Luna) early in its history in prograde orbit and underwent a benign estrangement scenario with its captured satellite.

  7. Formation, stratification, and mixing of the cores of Earth and Venus

    OpenAIRE

    Jacobson, Seth A.; Rubie, David C.; Hernlund, John; Morbidelli, Alessandro; Nakajima, Miki

    2017-01-01

    Earth possesses a persistent, internally-generated magnetic field, whereas no trace of a dynamo has been detected on Venus, at present or in the past, although a high surface temperature and recent resurfacing events may have removed paleomagnetic evidence. Whether or not a terrestrial body can sustain an internally generated magnetic field by convection inside its metallic fluid core is determined in part by its initial thermodynamic state and its compositional structure, both of which are i...

  8. Seismic generated infrasounds on Telluric Planets: Modeling and comparisons between Earth, Venus and Mars

    Science.gov (United States)

    Lognonne, P. H.; Rolland, L.; Karakostas, F. G.; Garcia, R.; Mimoun, D.; Banerdt, W. B.; Smrekar, S. E.

    2015-12-01

    Earth, Venus and Mars are all planets in which infrasounds can propagate and interact with the solid surface. This leads to infrasound generation for internal sources (e.g. quakes) and to seismic waves generations for atmospheric sources (e.g. meteor, impactor explosions, boundary layer turbulences). Both the atmospheric profile, surface density, atmospheric wind and viscous/attenuation processes are however greatly different, including major differences between Mars/Venus and Earth due to the CO2 molecular relaxation. We present modeling results and compare the seismic/acoustic coupling strength for Earth, Mars and Venus. This modeling is made through normal modes modelling for models integrating the interior, atmosphere, both with realistic attenuation (intrinsic Q for solid part, viscosity and molecular relaxation for the atmosphere). We complete these modeling, made for spherical structure, by integration of wind, assuming the later to be homogeneous at the scale of the infrasound wavelength. This allows us to compute either the Seismic normal modes (e.g. Rayleigh surface waves), or the acoustic or the atmospheric gravity modes. Comparisons are done, for either a seismic source or an atmospheric source, on the amplitude of expected signals as a function of distance and frequency. Effects of local time are integrated in the modeling. We illustrate the Rayleigh waves modelling by Earth data (for large quakes and volcanoes eruptions). For Venus, very large coupling can occur at resonance frequencies between the solid part and atmospheric part of the planet through infrasounds/Rayleigh waves coupling. If the atmosphere reduced the Q (quality coefficient) of Rayleigh waves in general, the atmosphere at these resonance soffers better propagation than Venus crust and increases their Q. For Mars, Rayleigh waves excitations by atmospheric burst is shown and discussed for the typical yield of impacts. The new data of the Nasa INSIGHT mission which carry both seismic and

  9. Formation, stratification, and mixing of the cores of Earth and Venus

    Science.gov (United States)

    Jacobson, Seth A.; Rubie, David C.; Hernlund, John; Morbidelli, Alessandro; Nakajima, Miki

    2017-09-01

    Earth possesses a persistent, internally-generated magnetic field, whereas no trace of a dynamo has been detected on Venus, at present or in the past, although a high surface temperature and recent resurfacing events may have removed paleomagnetic evidence. Whether or not a terrestrial body can sustain an internally generated magnetic field by convection inside its metallic fluid core is determined in part by its initial thermodynamic state and its compositional structure, both of which are in turn set by the processes of accretion and differentiation. Here we show that the cores of Earth- and Venus-like planets should grow with stable compositional stratification unless disturbed by late energetic impacts. They do so because higher abundances of light elements are incorporated into the liquid metal that sinks to form the core as the temperatures and pressures of metal-silicate equilibration increase during accretion. We model this process and determine that this establishes a stable stratification that resists convection and inhibits the onset of a geodynamo. However, if a late energetic impact occurs, it could mechanically stir the core creating a single homogenous region within which a long-lasting geodynamo would operate. While Earth's accretion has been punctuated by a late giant impact with likely enough energy to mix the core (e.g. the impact that formed the Moon), we hypothesize that the accretion of Venus is characterized by the absence of such energetic giant impacts and the preservation of its primordial stratifications.

  10. Existence of collisional trajectories of Mercury, Mars and Venus with the Earth.

    Science.gov (United States)

    Laskar, J; Gastineau, M

    2009-06-11

    It has been established that, owing to the proximity of a resonance with Jupiter, Mercury's eccentricity can be pumped to values large enough to allow collision with Venus within 5 Gyr (refs 1-3). This conclusion, however, was established either with averaged equations that are not appropriate near the collisions or with non-relativistic models in which the resonance effect is greatly enhanced by a decrease of the perihelion velocity of Mercury. In these previous studies, the Earth's orbit was essentially unaffected. Here we report numerical simulations of the evolution of the Solar System over 5 Gyr, including contributions from the Moon and general relativity. In a set of 2,501 orbits with initial conditions that are in agreement with our present knowledge of the parameters of the Solar System, we found, as in previous studies, that one per cent of the solutions lead to a large increase in Mercury's eccentricity-an increase large enough to allow collisions with Venus or the Sun. More surprisingly, in one of these high-eccentricity solutions, a subsequent decrease in Mercury's eccentricity induces a transfer of angular momentum from the giant planets that destabilizes all the terrestrial planets approximately 3.34 Gyr from now, with possible collisions of Mercury, Mars or Venus with the Earth.

  11. Evolution of a Coronal Mass Ejection from the Sun to Mercury, Venus, Earth and Beyond

    Science.gov (United States)

    Wang, Y.; Shen, C.; Liu, J.; Mengjiao, X.; Guo, J.

    2017-12-01

    A clear magnetic cloud was observed by Messenger at Mercury. By using coronagraph images from SOHO/LASCO and STEREO/COR and the in-situ data from Wind near the Earth, we estimated its propgation velocity and identified the possible CME candidate in the corona and its counterpart recorded by Venus Express near Venus. By applying the CME's DIPS (Deflection in InterPlanetary Space) model, we show that the CME's arrivals at the three different heliocentric distance can be well reproduced. By extending the trajectory of the CME to the orbitor of Mars, we predict the arrival of the CME at Mars, which is in agreement with a significant Forbush decrease observed by MSL. We use uniformly-twisted force-free flux rope model to fit the in-situ measurements at Mercury, Venus and the Earth to study the evolution of the magnetic flux rope, and find that both axial magnetic flux and twist significantly decreased, suggesting that a significant erosion process was on-going and might change the averaged twist of the magnetic flux rope.

  12. Effects of inclination and eccentricity on optimal trajectories between earth and Venus

    Science.gov (United States)

    Gravier, J.-P.; Marchal, C.; Culp, R. D.

    1973-01-01

    The true optimal transfers, including the effects of the inclination and eccentricity of the planets' orbits, between earth and Venus are presented as functions of the corresponding idealized Hohmann transfers. The method of determining the optimal transfers using the calculus of variations is presented. For every possible Hohmann window, specified as a continuous function of the longitude of perihelion of the Hohmann trajectory, the corresponding numerically exact optimal two-impulse transfers are given in graphical form. The cases for which the optimal two-impulse transfer is the absolute optimal, and those for which a three-impulse transfer provides the absolute optimal transfer are indicated. This information furnishes everything necessary for quick and accurate orbit calculations for preliminary Venus mission analysis. This makes it possible to use the actual optimal transfers for advanced planning in place of the standard Hohmann transfers.

  13. The Atmospheres of the Terrestrial Planets:Clues to the Origins and Early Evolution of Venus, Earth, and Mars

    Science.gov (United States)

    Baines, Kevin H.; Atreya, Sushil K.; Bullock, Mark A.; Grinspoon, David H,; Mahaffy, Paul; Russell, Christopher T.; Schubert, Gerald; Zahnle, Kevin

    2015-01-01

    We review the current state of knowledge of the origin and early evolution of the three largest terrestrial planets - Venus, Earth, and Mars - setting the stage for the chapters on comparative climatological processes to follow. We summarize current models of planetary formation, as revealed by studies of solid materials from Earth and meteorites from Mars. For Venus, we emphasize the known differences and similarities in planetary bulk properties and composition with Earth and Mars, focusing on key properties indicative of planetary formation and early evolution, particularly of the atmospheres of all three planets. We review the need for future in situ measurements for improving our understanding of the origin and evolution of the atmospheres of our planetary neighbors and Earth, and suggest the accuracies required of such new in situ data. Finally, we discuss the role new measurements of Mars and Venus have in understanding the state and evolution of planets found in the habitable zones of other stars.

  14. Comparative habitability of the Earth, Venus and Mars in the young solar system.

    Science.gov (United States)

    Nisbet, E. G.

    2008-09-01

    Abstract To be habitable, a planet must be suitable at all scales [1]. The setting in relation to the star must be right, so that surface temperatures can sustain liquid water. The planetary inventory must be suitable, providing surface water, rocks, and accessible thermodynamic disequilibrium. There must be physical habitat, especially mud and hydrothermal systems around volcanoes. Planets are not static: they evolve. Habitability must evolve with the planet. On accretion, the processes of impact and formation of volatile inventory must be suitable. Tectonics and volcanism must supply redox contrasts and biochemical substrates capable not only of starting life but of sustaining it. Mud or soft sediment may be essential: it is unlikely that early life can sustain itself in open water or air. This requirement for mud has tectonic implications. Once life starts, it immediately alters its own environment, by consuming nutrient. Until photosynthesis evolves, inorganic sources must supply sustained redox contrast to the local environment. But life changes its setting, both by risky alterations to the atmospheric greenhouse (drawing down CO2, emitting CH4), and by partitioning reductants (e.g. as dead bodies) and oxidants (waste). Somehow the planet must avoid both freezing and boiling. Early in the history of the solar system, a passing galactic tourist might have rated Venus as the likeliest habitat for life, Mars next, and Earth last of the three. Venus was warm and hospitable, Mars clement, and Earth had been though an impact episode powerful enough to make a silicate atmosphere. By comparison with Earth there are many potential environmental settings on Mars in which life may once have occurred, or may even continue to exist. Perhaps Mars seeded earth? Yet today the reverse order of habitability is the case. Earth today is safeguarded by a reworked atmosphere that is 99% of biological construction, maintained in active disequilibrium with the surface. Mars, in

  15. Study on meteoric particle destruction when passing through the Earth, Mars and Venus atmospheres

    International Nuclear Information System (INIS)

    Apshtejn, Eh.Z.; Pilyugin, N.N.; Vartanyan, N.V.

    1982-01-01

    A problem of a meteoric particle motion with provision for its nonstationary heating up and change of a form due to evaporation in rarefied layers of the Earth, Mars and Venus atmospheres is investigated. Numerical calculations are performed for a series of stone particles with sizes of approximately 1 mm at initial inlet velocity of 15 km/s 0 <= 60 km/s and inlet angles of 10-90 deg. The particle mass carrying away, temperature of particles, luminescence intensity, and meteoric trace electron concentration in successive time periods during the motion along the trajectory are determined. A comparison of the physical theory of met rites with the known approximate solutions and observations is conducted for the Earth atmosphere. Some peculiarities of meteoric particle destruction in different atmospheres are pointed out. Some methods of atmospheric parameter recovery according to observations of meteoric particle motion are proposed on the base of calculated dependences

  16. Venus: The Atmosphere, Climate, Surface, Interior and Near-Space Environment of an Earth-Like Planet

    Science.gov (United States)

    Taylor, Fredric W.; Svedhem, Håkan; Head, James W.

    2018-02-01

    This is a review of current knowledge about Earth's nearest planetary neighbour and near twin, Venus. Such knowledge has recently been extended by the European Venus Express and the Japanese Akatsuki spacecraft in orbit around the planet; these missions and their achievements are concisely described in the first part of the review, along with a summary of previous Venus observations. The scientific discussions which follow are divided into three main sections: on the surface and interior; the atmosphere and climate; and the thermosphere, exosphere and magnetosphere. These reports are intended to provide an overview for the general reader, and also an introduction to the more detailed topical surveys in the following articles in this issue, where full references to original material may be found.

  17. Characterization of Earth as an exoplanet on the basis of VIRTIS-Venus Express data analysis.

    Science.gov (United States)

    Oliva, Fabrizio; Piccioni, Giuseppe; D'Aversa, Emiliano; Bellucci, Giancarlo; Sindoni, Giuseppe; Grassi, Davide; Filacchione, Gianrico; Tosi, Federico; Capaccioni, Fabrizio

    2017-04-01

    The Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS, Piccioni et al., 2007) on board the Venus Express spacecraft observed the planet Earth several times in the course of the mission. In particular, a subset of 48 observations has been taken from a distance at which our planet is imaged at sub-pixel size, as exoplanets are observed using current technologies. We studied this full subset to understand which spectral signatures, related to different surface and cloud types, can be identified from the integrated planet spectrum. As expected, we found that the cloud coverage has a key role in the identification of surface features and that vegetation is very difficult to be detected. To validate our results we built a simple tool capable to simulate observations of an Earth-like planet as seen from a VIRTIS-like spectrometer in the 0.3 - 5.0 μm range. The illumination and viewing geometries, along with the spectrometer instantaneous field of view and spectral grid and sampling, can be defined by the user. The spectral endmembers used to generate the planet have been selected from an observation of Earth registered from the instrument VIRTIS on board the ESA mission Rosetta, with similar characteristics, during the third flyby of the spacecraft around our planet, occurred in November 2009. Hence, we simulated planets made of: vegetation, desert, ocean, water ice clouds and liquid water clouds. Using different amounts for each spectral class we inferred the percentages that are required to identify each class when all the spectral information is integrated into a single pixel. The outcome of this analysis confirms that clouds are not a negligible issue in the research for spectral signatures, in particular those related to the habitability of a planet and its climate conditions, even when the cloud coverage is not so high. Acknowledgements: This study has been performed within the WOW project financed by INAF and thanks to the support from the Italian Space

  18. VESL: The Virtual Earth Sheet Laboratory for Ice Sheet Modeling and Visualization

    Science.gov (United States)

    Cheng, D. L. C.; Larour, E. Y.; Quinn, J. D.; Halkides, D. J.

    2016-12-01

    We introduce the Virtual Earth System Laboratory (VESL), a scientific modeling and visualization tool delivered through an integrated web portal for dissemination of data, simulation of physical processes, and promotion of climate literacy. The current prototype leverages NASA's Ice Sheet System Model (ISSM), a state-of-the-art polar ice sheet dynamics model developed at the Jet Propulsion Lab and UC Irvine. We utilize the Emscripten source-to-source compiler to convert the C/C++ ISSM engine core to JavaScript, and bundled pre/post-processing JS scripts to be compatible with the existing ISSM Python/Matlab API. Researchers using VESL will be able to effectively present their work for public dissemination with little-to-no additional post-processing. This will allow for faster publication in peer-reviewed journals and adaption of results for educational applications. Through future application of this concept to multiple aspects of the Earth System, VESL has the potential to broaden data applications in the geosciences and beyond. At this stage, we seek feedback from the greater scientific and public outreach communities regarding the ease of use and feature set of VESL, as we plan its expansion, and aim to achieve more rapid communication and presentation of scientific results.

  19. VESL: The Virtual Earth Sheet Laboratory for Ice Sheet Modeling and Visualization

    Science.gov (United States)

    Cheng, D. L. C.; Larour, E. Y.; Quinn, J. D.; Halkides, D. J.

    2017-12-01

    We present the Virtual Earth System Laboratory (VESL), a scientific modeling and visualization tool delivered through an integrated web portal. This allows for the dissemination of data, simulation of physical processes, and promotion of climate literacy. The current iteration leverages NASA's Ice Sheet System Model (ISSM), a state-of-the-art polar ice sheet dynamics model developed at the Jet Propulsion Lab and UC Irvine. We utilize the Emscripten source-to-source compiler to convert the C/C++ ISSM engine core to JavaScript, and bundled pre/post-processing JS scripts to be compatible with the existing ISSM Python/Matlab API. Researchers using VESL will be able to effectively present their work for public dissemination with little-to-no additional post-processing. Moreover, the portal allows for real time visualization and editing of models, cloud based computational simulation, and downloads of relevant data. This allows for faster publication in peer-reviewed journals and adaption of results for educational applications. Through application of this concept to multiple aspects of the Earth System, VESL is able to broaden data applications in the geosciences and beyond. At this stage, we still seek feedback from the greater scientific and public outreach communities regarding the ease of use and feature set of VESL. As we plan its expansion, we aim to achieve more rapid communication and presentation of scientific results.

  20. Dynamics of the accumulation process of the Earth group of planets: Formation of the reverse rotation of Venus

    Science.gov (United States)

    Koslov, N. N.; Eneyev, T. M.

    1979-01-01

    A numerical simulation of the process of formation of the terrestrial planets is carried within the framework of a new theory for the accumulation of planetary and satellite systems. The numerical simulation permitted determining the parameters of the protoplanetary disk from which Mercury, Venus and the Earth were formed as result of the evolution. The acquisition of a slow retrograde rotation for Venus was discovered during the course of the investigation, whereas Mercury and the Earth acquired direct rotation about their axes. Deviations of the semimajor axes of these three planets as well as the masses of the Earth and Venus from the true values are small as a rule (l 10%). It is shown that during the accumulation of the terrestrial planets, there existed a profound relationship between the process of formation of the orbits and masses of the planet and the process of formation of their rotation about their axes. Estimates are presented for the radii of the initial effective bodies and the time of evolution for the terrestrial accumulation zone.

  1. Comparison of element compositions of Venus, Earth, Mars and chondrites in the light of D.I. Mendeleev's Periodic law

    International Nuclear Information System (INIS)

    Chuburkov, Yu.T.

    1999-01-01

    The part of free neutral atoms N 0 of all elements being contained in protoplanet cloud is estimated with regard to their abundance and physicochemical properties. Linear dependence of ratio of volatile and nonvolatile elements in chondrites and in eruptive Earth rocks on N 0 is obtained. Ratios of concentrations of element-analogs with different N 0 in substances of Venus, Earth, Mars and chondrites are compared. Obtained data are an evidence that hypothetical process of magnetic separation in protoplanet cloud has been taken place [ru

  2. Dynamic behavior of solar wind as revealed by a correlation study of magnetic fields observed at the Venus and Earth orbits

    Science.gov (United States)

    Marubashi, K.

    1995-01-01

    Correlations between interplanetary magnetic fields (IMFs) at 0.72 AU and 1.0 AU have been examined using data sets obtained from the Pioneer Venus orbiter and Earth-orbiting spacecraft. While the two-sector structures are evident in long-term variations at these two heliocentric distances, the corresponding auto-correlation coefficients are consistently smaller at 1.0 AU than at 0.72 AU. This suggests that the IMF structures become less persistent at 1.0 AU due to the effects of changing solar wind dynamics between the Venus and Earth orbits. Short-term variations exhibit generally poor correlations between IMFs near Venus and those near Earth, though good correlations are sometimes obtained for well-defined structures when the Sun, Venus, and Earth are closely aligned. The rather poor correlations in the background streams indicate that the IMFs are still changing between the Venus and Earth orbits under the strong influence of solar wind dynamics.

  3. The position and shape of the neutral sheet at 30-earth radii distance

    Science.gov (United States)

    Bowling, S. B.; Russell, C. T.

    1976-01-01

    An examination of Explorer 34 encounters with the neutral sheet reveals a much broader arching of the neutral sheet at 30 earth radii than closer to the earth at 20 earth radii. The location of the neutral sheet hinging point in the geomagnetic equatorial plane is found to be a strong function of geomagnetic activity. For Kp less than 2 the apparent hinging distance is close to 11 earth radii. For Kp greater than 4 the apparent hinging distance is close to zero. This dependency reflects a negligible return of the neutral sheet to the solar magnetospheric equatorial plane with distance behind the earth at quiet times but reflects a rapid return at disturbed times, in addition to possible variations in the location of the hinging point in the geomagnetic equatorial plane.

  4. Reentry response of the lightweight radioisotope heater unit resulting from a Cassini Venus-Venus-Earth-Jupiter gravity assist maneuver accident

    International Nuclear Information System (INIS)

    1996-12-01

    Reentry analyses consisting of ablation response, thermal response and thermal stress response have been conducted on the Lightweight Radioisotope Heater Unit (LWRHU) for Cassini/Venus-Venus-Earth-Jupiter-Gravity-Assist (VVEJGA) reentry conditions. Sequential ablation analyses of the LWRHU aeroshell, and the fuel pellet have been conducted in reentry regimes where the aeroshell has been deemed to fail. The failure criterion for ablation is generally assumed to be recession corresponding to 75% and 100% of the wall thickness. The 75% recession failure criteria allows for uncertainties that result mainly because of the high energies involved in the VVEJGA reentries compared to orbital decay reentries. Risk evaluations should consider the fact that for shallow flight paths the unit may disassemble at high-altitude as a result of ablation or may remain intact with a clad that had been molten. Within the limitations of the methodologies and assumptions of the analyses, the results indicate that: (1) For a side-on stable LWRHU reentry, aeroshell ablation failures occur for all reentry angles. (2)For a side-on spinning LWRHU reentry, aeroshell ablation failures are minimal. (3) For the tumbling LWRHU reentry, the aeroshell survives for most angles. (4) For the thermostructural analyses, using both a 1% and 5% allowable strain, all reentry angles and orientations examined resulted in small localized failures, but aeroshell breach is not predicted for any case. The analyses included in this report concentrate on VVEJGA reentry scenarios. Analyses reported previously have demonstrated that the LWRHU has adequate design margin to survive reentry from orbital decay scenarios and most injection scenarios at speeds up to escape speeds. The exception is a narrow range of flight path angles that produce multiple skip trajectories which may have excessive ablation

  5. Reentry response of the lightweight radioisotope heater unit resulting from a Cassini Venus-Venus-Earth-Jupiter gravity assist maneuver accident

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-12-01

    Reentry analyses consisting of ablation response, thermal response and thermal stress response have been conducted on the Lightweight Radioisotope Heater Unit (LWRHU) for Cassini/Venus-Venus-Earth-Jupiter-Gravity-Assist (VVEJGA) reentry conditions. Sequential ablation analyses of the LWRHU aeroshell, and the fuel pellet have been conducted in reentry regimes where the aeroshell has been deemed to fail. The failure criterion for ablation is generally assumed to be recession corresponding to 75% and 100% of the wall thickness. The 75% recession failure criteria allows for uncertainties that result mainly because of the high energies involved in the VVEJGA reentries compared to orbital decay reentries. Risk evaluations should consider the fact that for shallow flight paths the unit may disassemble at high-altitude as a result of ablation or may remain intact with a clad that had been molten. Within the limitations of the methodologies and assumptions of the analyses, the results indicate that: (1) For a side-on stable LWRHU reentry, aeroshell ablation failures occur for all reentry angles. (2)For a side-on spinning LWRHU reentry, aeroshell ablation failures are minimal. (3) For the tumbling LWRHU reentry, the aeroshell survives for most angles. (4) For the thermostructural analyses, using both a 1% and 5% allowable strain, all reentry angles and orientations examined resulted in small localized failures, but aeroshell breach is not predicted for any case. The analyses included in this report concentrate on VVEJGA reentry scenarios. Analyses reported previously have demonstrated that the LWRHU has adequate design margin to survive reentry from orbital decay scenarios and most injection scenarios at speeds up to escape speeds. The exception is a narrow range of flight path angles that produce multiple skip trajectories which may have excessive ablation.

  6. Modeling of atmospheric-coupled Rayleigh waves on planets with atmosphere: From Earth observation to Mars and Venus perspectives.

    Science.gov (United States)

    Lognonné, Philippe; Karakostas, Foivos; Rolland, Lucie; Nishikawa, Yasuhiro

    2016-08-01

    Acoustic coupling between solid Earth and atmosphere has been observed since the 1960s, first from ground-based seismic, pressure, and ionospheric sensors and since 20 years with various satellite measurements, including with global positioning system (GPS) satellites. This coupling leads to the excitation of the Rayleigh surface waves by local atmospheric sources such as large natural explosions from volcanoes, meteor atmospheric air-bursts, or artificial explosions. It contributes also in the continuous excitation of Rayleigh waves and associated normal modes by atmospheric winds and pressure fluctuations. The same coupling allows the observation of Rayleigh waves in the thermosphere most of the time through ionospheric monitoring with Doppler sounders or GPS. The authors review briefly in this paper observations made on Earth and describe the general frame of the theory enabling the computation of Rayleigh waves for models of telluric planets with atmosphere. The authors then focus on Mars and Venus and give in both cases the atmospheric properties of the Rayleigh normal modes and associated surface waves compared to Earth. The authors then conclude on the observation perspectives especially for Rayleigh waves excited by atmospheric sources on Mars and for remote ionospheric observations of Rayleigh waves excited by quakes on Venus.

  7. Incorporation of ice sheet models into an Earth system model: Focus ...

    Indian Academy of Sciences (India)

    Oleg Rybak

    2018-03-06

    Mar 6, 2018 ... Elaboration of a modern Earth system model (ESM) requires incorporation of ice sheet dynamics. Coupling of an ice sheet model (ICM) to an AOGCM is complicated by essential differences in spatial and temporal scales of cryospheric, atmospheric and oceanic components. To overcome this difficulty, we ...

  8. Understanding divergent evolution of Earth-like planets: the case for a Venus exploration program

    Science.gov (United States)

    Crisp, D.

    2002-01-01

    Here, we propose a Venus exploration program designed to explain the origin and divergent evolution of the interiors, surfaces, and atmospheres of the terrestrial planets in our solar system, and provide greater insight into the conditions that may affect the habitability of terrestrial planets in other solar systems.

  9. The comparison of element composition of Venus, Earth, Mars, and chondrites in the light of the Mendeleev Periodic Law

    International Nuclear Information System (INIS)

    Chuburkov, Yu.T.

    1998-01-01

    The share of free neutral atoms, N 0 , for all elements in Protoplanet nebula has been determined with the account of their abundance and physico-chemical properties. The linear dependence for the ratio of nonvolatile and volatile elements in chondrites and igneous rocks of the Earth on N 0 was obtained. The Mendeleev Periodic Law was used to obtain the proof of the existence of the hypothetical process of element magnetic separation in Protoplanet nebula. To this end the concentration ratios of element-analogous with different N 0 in the matters of Venus, Earth, Mars, and chondrites were compared. The data obtained are sufficient demonstration of the existence of the hypothetical process of element magnetic separation in Protoplanet nebula. With the account of the above said, it was shown that Shergotty and Tunguska meteorites by their relative elemental composition are close to Mars and asteroids, respectively. (author)

  10. Current disruptions in the near-earth neutral sheet region

    International Nuclear Information System (INIS)

    Liu, A.T.Y.; Anderson, B.J.; Takahashi, K.; Zanetti, L.J.; McEntire, R.W.; Potemra, T.A.; Lopez, R.E.; Klumpar, D.M.; Greene, E.M.; Strangeway, R.

    1992-01-01

    Observations from the Charge Composition Explorer in 1985 and 1986 revealed fifteen current disruption events in which the magnetic field fluctuations were large and their onsets coincided well with ground onsets of substorm expansion or intensification. Over the disruption interval, the local magnetic field can change by as much as a factor of ∼7. In general, the stronger the current buildup and the closer the neutral sheet, the larger the resultant field change. There is also a tendency for a larger subsequent enhancement in the AE index with a stronger current buildup prior to current disruption. For events with good pitch angle coverage and extended observation in the neutral sheet region the authors find that the particle pressure increases toward the disruption onset and decreases afterward. Just prior to disruption, either the total particle pressure is isotropic, or the perpendicular component (P perpendicular ) dominates the parallel component (P parallel ), the plasma beta is seen to be as high as ∼70, and the observed plasma pressure gradient at the neutral sheet is large along the tail axis. The deduced local current density associated with pressure gradient is ∼27-80 n/Am 2 and is ∼85-105 mA/m when integrated over the sheet thickness. They infer from these results that just prior to the onset of current disruption, (1) an extremely thin current sheet requiring P parallel > P perpendicular for stress balance does not develop at these distances, (2) the thermal ion orbits are in the chaotic or Speiser regime while the thermal electrons are in the adiabatic regime and, in one case, exhibit peaked fluxes perpendicular to the magnetic field, thus implying no electron orbit chaotization to possibly initiate ion tearing instability, and (3) the neutral sheet is in the unstable regime specified by the cross-field current instability

  11. Variations of the Antarctic Ice Sheet in a Coupled Ice Sheet-Earth-Sea Level Model: Sensitivity to Viscoelastic Earth Properties

    Science.gov (United States)

    Pollard, David; Gomez, Natalya; Deconto, Robert M.

    2017-11-01

    A coupled ice sheet-solid Earth-sea level model is applied to long-term variations of the Antarctic ice sheet. A set of radially varying viscoelastic profiles in the global Earth model is used to explore feedbacks on ice sheet variability, including one with a very weak upper mantle zone and thin lithosphere representative of West Antarctic regions. Simulations are performed for (1) the deglacial retreat over the last 20,000 years, (2) the future 5,000 years with greenhouse-gas scenario Representative Concentration Pathway 8.5 (RCP8.5), and (3) the warm Pliocene 3 Ma. For the deglacial period a large ensemble of 625 simulations is analyzed, with a score computed for each run based on comparisons to geologic and modern data. For each of the five Earth profiles, the top-scoring combinations of the other model parameters in the ensemble are used to perform future and Pliocene simulations. For the last deglacial retreat, the viscoelastic Earth profiles produce relatively small differences in overall ice volume and equivalent sea level. In contrast, profiles with weak upper mantle and thin lithosphere produce strong negative feedback and less ice retreat in the future and Pliocene runs. This is due to the faster pace of ice sheet retreat in these runs, leading to greater lags in the viscous bedrock rebound behind the unloading, which allows for greater influence of the viscosity profiles. However, the differences in grounding-line retreat are located primarily in East Antarctic basins, where a weak upper mantle and thin lithosphere may not be realistic, emphasizing the need for lateral heterogeneity in the Earth model.

  12. An unusual volcano on Venus

    Science.gov (United States)

    Moore, H. J.; Plaut, J. J.; Schenk, P. M.; Head, J. W.

    1992-01-01

    Materials that issued from an unusual Venusian volcano produced (1) a complex domical structure about 100 km across with thick, broad flow lobes up to 41 wide, (2) an extensive sheet of thick flows, and (3) radar-bright surfaces that extend to 360-400 km from the volcano. Altimetry indicates that the relief of the domical structure is about 0.5-1.1 km. The lobes and flows have prominant regularly spaced ridges about 686-820 m apart. Thick flows with large ridge separations and broad lobes are rare on Venus. The viscosities of these flows were larger than those of most lava flows on Venus. Comparisons of the dimensions of the volcano's lobes with lava flows on earth suggest that the Venusian lavas may have large silica contents. Radar-bright surfaces around the volcano may represent the result of an explosive eruption or very thin deposits of low-viscosity lavas. Thus, the radar-bright surfaces and lavas of the volcano were derived from a magma that differentiated within the crust or mantle of Venus. The differentiation produced (1) a gas-rich low-viscosity phase, (2) high-viscosity lavas, and (3) a residual primary magma.

  13. Stability of Basalt plus Anhydrite plus Calcite at HP-HT: Implications for Venus, the Earth and Mars

    Science.gov (United States)

    Martin, A. M.; Righter, K.; Treiman, A. H.

    2010-01-01

    "Canali" observed at Venus surface by Magellan are evidence for very long melt flows, but their composition and origin remain uncertain. The hypothesis of water-rich flow is not reasonable regarding the temperature at Venus surface. The length of these channels could not be explained by a silicate melt composition but more likely, by a carbonate-sulfate melt which has a much lower viscosity (Kargel et al 1994). One hypothesis is that calcite CaCO3 and anhydrite CaSO4 which are alteration products of basalts melted during meteorite impacts. A famous example recorded on the Earth (Chicxulub) produced melt and gas rich in carbon and sulfur. Calcite and sulfate evaporites are also present on Mars surface, associated with basalts. An impact on these materials might release C- and S-rich melt or fluid. Another type of planetary phenomenon (affecting only the Earth) might provoke a high pressure destabilization of basalt+anhydrite+calcite. Very high contents of C and S are measured in some Earth s magmas, either dissolved or in the form of crystals (Luhr 2008). As shown by the high H content and high fO2 of primary igneous anhydrite-bearing lavas, the high S content in their source may be explained by subduction of an anhydrite-bearing oceanic crust, either directly (by melting followed by eruption) or indirectly (by release of S-rich melt or fluid that metasomatize the mantle) . Calcite is a major product of oceanic sedimentation and alteration of the crust. Therefore, sulfate- and calcite-rich material may be subducted to high pressures and high temperatures (HP-HT) and release S- and C-rich melts or fluids which could influence the composition of subduction zone lavas or gases. Both phenomena - meteorite impact and subduction - imply HP-HT conditions - although the P-T-time paths are different. Some HP experimental/theoretical studies have been performed on basalt/eclogite, calcite and anhydrite separately or on a combination of two. In this study we performed piston

  14. Convective thinning of the lithosphere: A mechanism for rifting and mid-plate volcanism on Earth, Venus, and Mars

    Science.gov (United States)

    Spohn, T.; Schubert, G.

    1982-01-01

    Thinning of the Earth's lithosphere by heat advected to its base is a possible mechanism for continental rifting and continental and oceanic mid-plate volcanism. It might also account for continental rifting-like processes and volcanism on Venus and Mars. Earth's continental lithosphere can be thinned to the crust in a few tens of million years by heat advected at a rate of 5 to 10 times the normal basal heat flux. This much heat is easily carried to the lithosphere by mantle plumes. The continent is not required to rest over the mantle hot spot but may move at tens of millimeters per year. Because of the constant level of crustal radioactive heat production, the ratio of the final to the initial surface heat flow increases much less than the ratio of the final to initial basal heat flow. For large increases in asthenospheric heat flow, the lithosphere is almost thinned to the crust before any significant change in surface heat flow occurs. Uplift due to thermal expansion upon thinning is a few kilometers. The oceanic lithosphere can be thinned to the crust in less than 10 million years if the heat advection is at a rate around 5 or more times the basal heat flow into 100 Ma old lithosphere. Uplift upon thinning can compensate the subsidence of spreading and cooling lithosphere.

  15. Sea-level and solid-Earth deformation feedbacks in ice sheet modelling

    Science.gov (United States)

    Konrad, Hannes; Sasgen, Ingo; Klemann, Volker; Thoma, Malte; Grosfeld, Klaus; Martinec, Zdeněk

    2014-05-01

    The interactions of ice sheets with the sea level and the solid Earth are important factors for the stability of the ice shelves and the tributary inland ice (e.g. Thomas and Bentley, 1978; Gomez et al, 2012). First, changes in ice extent and ice thickness induce viscoelastic deformation of the Earth surface and Earth's gravity field. In turn, global and local changes in sea level and bathymetry affect the grounding line and, subsequently, alter the ice dynamic behaviour. Here, we investigate these feedbacks for a synthetic ice sheet configuration as well as for the Antarctic ice sheet using a three-dimensional thermomechanical ice sheet and shelf model, coupled to a viscoelastic solid-Earth and gravitationally self-consistent sea-level model. The respective ice sheet undergoes a forcing from rising sea level, warming ocean, and/or changing surface mass balance. The coupling is realized by exchanging ice thickness, Earth surface deformation and sea level periodically. We apply several sets of viscoelastic Earth parameters to our coupled model, e.g. simulating a low-viscous upper mantle present at the Antarctic Peninsula (Ivins et al., 2011). Special focus of our study lies on the evolution of Earth surface deformation and local sea level changes, as well as on the accompanying grounding line evolution. N. Gomez, D. Pollard, J. X. Mitrovica, P. Huybers, and P. U. Clark 2012. Evolution of a coupled marine ice sheet-sea level model, J. Geophys. Res., 117, F01013, doi:10.1029/2011JF002128. E. R. Ivins, M. M. Watkins, D.-N. Yuan, R. Dietrich, G. Casassa, and A. Rülke 2011. On-land ice loss and glacial isostatic adjustment at the Drake Passage: 2003-2009, J. Geophys. Res. 116, B02403, doi: 10.1029/2010JB007607 R. H. Thomas and C. R. Bentley 1978. A model for Holocene retreat of the West Antarctic Ice Sheet, Quaternary Research, 10 (2), pages 150-170, doi: 10.1016/0033-5894(78)90098-4.

  16. A new research project on the interaction of the solid Earth and the Antarctic Ice Sheet

    Science.gov (United States)

    Fukuda, Y.; Nishijima, J.; Kazama, T.; Nakamura, K.; Doi, K.; Suganuma, Y.; Okuno, J.; Araya, A.; Kaneda, H.; Aoyama, Y.

    2017-12-01

    A new research project of "Grant-in-Aid for Scientific Research on Innovative Areas" funded by JSPS (Japan Society for the Promotion of Science) has recently been launched. The title of the project is "Giant reservoirs of heat/water/material: Global environmental changes driven by Southern Ocean and Antarctic Ice Sheet", and as a five years project, is aiming to establish a new research area for Antarctic environmental system science. The project consists of 7 research topics, including Antarctic ice sheet and Southern ocean sciences, new observation methodology, modeling and other interdisciplinary topics, and we are involved in the topic A02-2, "Interaction of the solid Earth and the Antarctic Ice Sheet". The Antarctic ice sheet, which relates to the global climate changes through the sea level rise and ocean circulation, is an essential element of the Earth system for predicting the future environment changes. Thus many studies of the ice sheet changes have been conducted by means of geomorphological, geological, geodetic surveys, as well as satellite gravimetry and satellite altimetry. For these studies, one of the largest uncertainties is the effects of GIA. Therefore, GIA as a key to investigate the interaction between the solid Earth and the ice sheet changes, we plan to conduct geomorphological, geological and geodetic surveys in the inland mountain areas and the coastal areas including the surrounding areas of a Japanese station Syowa in East Antarctica, where the in-situ data for constraining GIA models are very few. Combining these new observations with other in-site data, various satellite data and numerical modeling, we aim to estimating a precise GIA model, constructing a reliable ice melting history after the last glacial maximum and obtaining the viscoelastic structure of the Earth's interior. In the presentation, we also show the five years research plans as well. This study was partially supported by JSPS KAKENHI Grant No. 17H06321.

  17. Ion flow ripples in the Earth's plasma sheet

    Science.gov (United States)

    De Spiegeleer, Alexandre; Hamrin, Maria; Pitkänen, Timo; Norqvist, Patrik; Mann, Ingrid

    2016-04-01

    For a long time, magnetotail flows were considered rather smooth and laminar, and primarily dominated by a simple convection flow pattern. However, in the early 90's, high speed bursty bulk flows (BBFs) were discovered and found to commonly perturb the underlying convection flows. In addition, there are other disturbances complicating the magnetotail flow pattern. Instabilities such as the Kelvin-Helmholz instability and the kink instability can cause different types of magnetic field oscillations, such as field line resonances. It is expected that ions will follow these oscillations if the typical time and length scales are larger than the gyroperiod and gyroradius of the ions. Though low-velocity sloshing and ripple disturbances of the average magnetotail convection flows have been observed, their connection with magnetic field oscillations is not fully understood. Furthermore, when studying BFFs, these "Ion Flow Ripples" (IFRs) are often neglected, dismissed as noise or can even erroneously be identified as BBFs. It is therefore of utter importance to find out and understand the role of IFRs in magnetotail dynamics. In a statistical investigation, we use several years of Cluster plasma sheet data to study the low-speed flows in the magnetotail. We investigate different types of IFRs, study their occurrence, and discuss their possible causes.

  18. A new view of Earth's sister: Insights following nine years of Venus Express observations

    Science.gov (United States)

    Titov, Dmitrij; Svedhem, Håkan; Drossart, Pierre; Taylor, Fredric W.; Zhang, Tielong; Barabash, Stas; Paetzold, Martin; Piccioni, Giuseppe; Markiewicz, Wojciech; Vandaele, Ann C.; Wilson, Colin; Bertaux, Jean-Loup

    Since April 2006 ESA’s Venus Express has been performing a global survey of the remarkably dense, cloudy, and dynamic atmosphere of our near neighbour. The mission delivers comprehensive data on the temperature structure, the atmospheric composition, the cloud morphology, the atmospheric dynamics, the solar wind interaction and the escape processes. Vertical profiles of the atmospheric temperature show strong latitudinal trend in the mesosphere and upper troposphere correlated with changes in the cloud top structure and indicate convective instability in the main cloud deck at 50-60 km. Observations reveal significant latitudinal variations and temporal changes in the global cloud top morphology, which modulate the solar energy deposited in the atmosphere. The cloud top altitude varies from 72 km in the low and middle latitudes to 64 km in the polar region, correlated with decrease of the aerosol scale height from 4±1.6 km to 1.7±2.4 km, marking vast polar depression. UV imaging shows for the first time the middle latitudes and polar regions in unprecedented detail. The eye of the Southern polar vortex was found to be a strongly variable feature with complex dynamics. Solar occultation observations and deep atmosphere spectroscopy in spectral transparency windows mapped the distribution of the major trace gases H _{2}O, SO _{2}, CO, COS and their variations above and below the clouds, revealing key features of the dynamical and chemical processes at work. Tracking motions of cloud features provided the most complete characterization of the mean atmospheric circulation as well as its variability. Low and middle latitudes show an almost constant zonal wind speed at the cloud tops and vertical wind shear of 2-3 m/s/km. The zonal wind speed increased from 84±20 m/s to 110±16 m/s over the course of the mission. Towards the pole, the wind speed drops quickly and the vertical shear vanishes. The meridional poleward wind ranges from 0 at equator to about 15 m/s in

  19. Bi-directional electrons in the near-Earth plasma sheet

    Directory of Open Access Journals (Sweden)

    K. Shiokawa

    2003-07-01

    Full Text Available We have studied the occurrence characteristics of bi-directional electron pitch angle anisotropy (enhanced flux in field-aligned directions, F^ /F|| > 1.5 at energies of 0.1–30 keV using plasma and magnetic field data from the AMPTE/IRM satellite in the near-Earth plasma sheet. The occurrence rate increases in the tailward direction from XGSM = - 9 RE to - 19 RE . The occurrence rate is also enhanced in the midnight sector, and furthermore, whenever the elevation angle of the magnetic field is large while the magnetic field intensity is small, B ~ 15 nT. From these facts, we conclude that the bi-directional electrons in the central plasma sheet are produced mainly in the vicinity of the neutral sheet and that the contribution from ionospheric electrons is minor. A high occurrence is also found after earthward high-speed ion flows, suggesting Fermi-type field-aligned electron acceleration in the neutral sheet. Occurrence characteristics of bi-directional electrons in the plasma sheet boundary layer are also discussed.Key words. Magnetospheric physics (magnetospheric configuration and dynamics; magnetotail; plasma sheet

  20. Production of nitrogen oxides by lightning and coronae discharges in simulated early Earth, Venus and Mars environments.

    Science.gov (United States)

    Nna Mvondo, D; Navarro-Gonzalez, R; McKay, C P; Coll, P; Raulin, F

    2001-01-01

    We present measurements for the production of nitrogen oxides (NO and N2O) in CO2-N2 mixtures that simulate different stages of the evolution of the atmospheres of the Earth, Venus and Mars. The nitrogen fixation rates by two different types of electrical discharges, namely lightning and coronae, were studied over a wide range in CO2 and N2 mixing ratios. Nitric oxide (NO) is formed with a maximum energy yield estimated to be ~1.3 x 10(16) molecule J-1 at 80% CO2 and ~1.3 x 10(14) molecule J-1 at 50% CO2 for lightning and coronae discharges, respectively. Nitrous oxide (N2O) is only formed by coronae discharge with a maximum energy yield estimated to be ~1.2 x 10(13) molecule J-1 at 50% CO2. The pronounced difference in NO production in lightning and coronae discharges and the lack of formation of N2O in lightning indicate that the physics and chemistry involved in nitrogen fixation differs substantially in these two forms of electric energy. c2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

  1. Venus: Our Misunderstood Sister

    Science.gov (United States)

    Dyar, Darby; Smrekar, Suzanne E.

    2018-01-01

    Of all known bodies in the galaxy, Venus is the most Earth-like in size, composition, surface age, and incoming energy. As we search for habitable planets around other stars, learning how Venus works is critical to understanding how Earth evolved to host life, and whether rocky exoplanets in stars’ habitable zones are faraway Earths or Venuses. What caused Venus’ path to its present hostile environment, devoid of oceans, magnetic field, and plate tectonics? This talk reviews recent mission results, presents key unresolved science questions, and describes proposed missions to answer these questions.Despite its importance in understanding habitability, Venus is the least-explored rocky planet, last visited by NASA in 1994. Fundamental, unanswered questions for Venus include: 1. How did Venus evolve differently? 2. How have volatiles shaped its evolution? 3. Did Venus catastrophically resurface? 4. What geologic processes are active today? 5. Why does Venus lack plate tectonics?On Earth, plate tectonics supports long-term climate stability and habitability by cycling volatiles in and out of the mantle. New information on planetary volatiles disputes the long-held notion that Venus’ interior is dry; several lines of evidence indicate that planets start out wet, creating long-term atmospheres by outgassing. ESA’s Venus Express mission provided evidence for recent and ongoing volcanism and for Si-rich crust like Earth’s continents. New hypotheses suggest that lithospheric temperature can explain why Venus lacks tectonics, and are consistent with present-day initiation of subduction on Venus.New data are needed to answer these key questions of rocky planet evolution. Orbital IR data can be acquired through windows in Venus’ CO2-rich atmosphere, informing surface mineralogy, rock types, cloud variations, and active volcanism. High resolution gravity, radar, and topography data along with mineralogical constraints must be obtained. Mineralogy and geochemistry

  2. Continuous Planetary Polar Observation from Hybrid Pole-Sitters at Venus, Earth, and Mars

    NARCIS (Netherlands)

    Heiligers, M.J.; van den Oever (student TUDelft), Tom; Ceriotti, M.; Mulligan, P.; McInnes, CR

    2017-01-01

    A pole-sitter is a satellite that is stationed along the polar axis of the Earth, or any other planet, to generate a continuous, hemispherical view of the planet’s polar regions. In order to maintain such a vantage point, a low-thrust propulsion system is required to counterbalance the gravitational

  3. Incorporation of ice sheet models into an Earth system model: Focus on methodology of coupling

    Science.gov (United States)

    Rybak, Oleg; Volodin, Evgeny; Morozova, Polina; Nevecherja, Artiom

    2018-03-01

    Elaboration of a modern Earth system model (ESM) requires incorporation of ice sheet dynamics. Coupling of an ice sheet model (ICM) to an AOGCM is complicated by essential differences in spatial and temporal scales of cryospheric, atmospheric and oceanic components. To overcome this difficulty, we apply two different approaches for the incorporation of ice sheets into an ESM. Coupling of the Antarctic ice sheet model (AISM) to the AOGCM is accomplished via using procedures of resampling, interpolation and assigning to the AISM grid points annually averaged meanings of air surface temperature and precipitation fields generated by the AOGCM. Surface melting, which takes place mainly on the margins of the Antarctic peninsula and on ice shelves fringing the continent, is currently ignored. AISM returns anomalies of surface topography back to the AOGCM. To couple the Greenland ice sheet model (GrISM) to the AOGCM, we use a simple buffer energy- and water-balance model (EWBM-G) to account for orographically-driven precipitation and other sub-grid AOGCM-generated quantities. The output of the EWBM-G consists of surface mass balance and air surface temperature to force the GrISM, and freshwater run-off to force thermohaline circulation in the oceanic block of the AOGCM. Because of a rather complex coupling procedure of GrIS compared to AIS, the paper mostly focuses on Greenland.

  4. Long-Duration Altitude-Controlled Balloons for Venus: A Feasibility Study Informed by Balloon Flights in Remote Environments on Earth

    Science.gov (United States)

    Voss, P. B.; Nott, J.; Cutts, J. A.; Hall, J. L.; Beauchamp, P. M.; Limaye, S. S.; Baines, K. H.; Hole, L. R.

    2013-12-01

    In situ exploration of the upper atmosphere of Venus, approximately 65-77 km altitude, could answer many important questions (Limaye 2013, Crisp 2013). This region contains a time-variable UV absorber of unknown composition that controls many aspects of the heat balance on Venus. Understanding the composition and dynamics of this unknown absorber is an important science goal; in situ optical and chemical measurements are needed. However, conventional approaches do not provide access to this altitude range, repeated traverses, and a mission lifetime of several months needed to effectively carry out the science. This paper examines concepts for altitude-controlled balloons not previously flown on planetary missions that could potentially provide the desired measurements. The concepts take advantage of the fact that at 60 km altitude, for example, the atmospheric density on Venus is about 40% of the sea-level density on earth and the temperature is a moderate 230 K. The solar flux is approximately double that on earth, creating some thermal challenges, but making photovoltaic power highly effective. Using a steady-state thermodynamic model and flight data from Earth, we evaluate the suitability of two types of altitude-controlled balloons for a potential mission on Venus. Such balloons could repeatedly measure profiles, avoid diurnal temperature extremes, and navigate using wind shear. The first balloon design uses air ballast (AB) whereby ambient air can be compressed into or released from a constant-volume balloon, causing it to descend or ascend accordingly. The second design uses lift-gas compression (LGC) to change the volume of a zero-pressure balloon, thereby changing its effective density and altitude. For an altitude range of 60-75 km on Venus, we find that the superpressure volume for a LGC balloon is about 5% of that needed for an AB balloon while the maximum pressurization is the same for both systems. The compressor work per km descent of the LGC balloon

  5. Radarclinometry of the Earth and Venus from space-shuttle and Venera-15 imagery

    Science.gov (United States)

    Wildey, R.L.

    1990-01-01

    the dependence on initial strike of the gravitational potential energy of the vertical slab of terrain under the range-profile. The adopted starting strike for the range integral is the one which minimizes the gravitational potential energy. This radarclinometric method, in combination with my recently published method for determining an effective radar back-scattering function from one-dimensional slope statistics and image pixel-signal statistics, was applied to three images. First, to separate theoretical difficulties from experimental impediments, an artificial radar image was generated from a topographic map of the Lake Champlain West quadrangle in the Adirondack Mountains. Except for the regional trend in elevation, to which radarclinometry is insensitive by design, the agreement between the original and derived topography appears good. The morphologies agree and the range of relief is the same to within 4%. As an example of data of the highest quality available from space-borne radar at the present time, a SIR-B image of very rugged terrain in the coastal mountains of Oregon was similarly processed. The result, after filtering to redistribute photoclinometric errors about the two-dimensional spatial spectrum, agrees with ground truth almost as well. As an example of the worst possible data, in terms of signal-to-noise ratio and radar incidence angle (no detraction from the praise due the first high resolution space-borne radar-imaging of Venus intended), a Venera-15 image segment in Sedna Planitia just north-east of Sapho was processed, using Venera altimetry and Pioneer roughness data for slope statistics, in spite of the resolution mis-match. Considerably more trial-and-error filtering was required. The result appears plausible, but an error check is, of course, impossible. ?? 1990 Kluwer Academic Publishers.

  6. Diapirism on Venus and the Early Earth and The thermal effect of fluid flows in AECL's Tunnel Sealing Experiment

    Science.gov (United States)

    Robin, Catherine M. I.

    2010-12-01

    Flow instabilities occur at all scales in planetary systems. In this thesis we examine three cases of such instabilities, on three very different length scales. In the first part, we test the idea that Archean granite-greenstone belts (GGBs) form by crustal diapirism, or Rayleigh-Taylor instabilities. GGBs are characterized by large granitic domes (50-100 km in diameter) embedded in narrow keel-shaped greenstones. They are ubiquitous in Archean (> 2.5 Ga) terrains, but rare thereafter. We performed finite element calculations for a visco-elastic, temperature-dependent, non-Newtonian crust under conditions appropriate for the Archean, which show that dense low-viscosity volcanics overlying a felsic basement will overturn diapirically in as little as 10 Ma, displacing as much as 60 % of the volcanics to the lower crust. This surprisingly fast overturn rate suggests that diapiric overturn dominated crustal tectonics in the hot conditions of the Early Earth, becoming less important as the Earth cooled. Moreover, the deposition of large volumes of wet basaltic volcanics to the lower crust may provide the source for the formation of the distinctly Archean granitic rocks which dominate Earth's oldest continents. The second part examines the origin of Venusian coronae, circular volcanic features unique to Venus. Coronae are thought to result from small instabilities (diapirs) from the core-mantle boundary, which are typical of stagnant-lid convection. However, most young coronae are located in a region surrounded by long-lived hotspots, typical of a more active style of mantle convection. Using analogue experiments in corn syrup heated from below, we show that the co-existence of diapirs and long-lived mantle plumes are a direct consequence of the catastrophic overturn of the cold Venusian lithosphere thought to have occurred ˜ 700 Ma ago. In the last part we analyze the thermal effect of fluid flow through a full-scale experiment testing clay and concrete tunnel seals in

  7. Modeling Venus-Like Worlds Through Time

    OpenAIRE

    Way, M. J.; Del Genio, Anthony; Amundsen, David S.

    2018-01-01

    We explore the atmospheric and surface history of a hypothetical paleo-Venus climate using a 3-D General Circulation Model. We constrain our model with the in-situ and remote sensing Venus data available today. Given that Venus and Earth are believed to be similar geochemically some aspects of Earth's history are also utilized. We demonstrate that it is possible for ancient Venus and Venus-like exoplanetary worlds to exist within the liquid water habitable zone with insolations up to nearly 2...

  8. Venus cartography

    Science.gov (United States)

    Batson, R. M.; Kirk, R. L.; Edwards, Kathleen; Morgan, H. F.

    1994-01-01

    The entire surface of the planet Venus is being mapped at global and regional scales (1:50 million through 1:1.5 million) with synthetic aperture radar (SAR), radar altimeter, and radiometer measurements of physical properties from the Magellan spacecraft. The mapping includes SAR image mosaics, shaded relief maps, and topographic contour overlays made from altimetry data and by radargrammetric methods. Methods used include new techniques of radar image processing that became operational as a result of the Magellan mission. Special cartographic support products prepared by the USGS include: synthetic stereograms, color thematic maps of physical properties, digital shaded relief maps from opposite-look SAR, and topographic maps by radargrammetry. The area being mapped (at a resolution of 75 m/pixel) is roughly equivalent to that of Earth, including seafloors. The mapping is designed to support geologic and geophysical investigations.

  9. The Plasma Sheet as Natural Symmetry Plane for Dipolarization Fronts in the Earth's Magnetotail

    Science.gov (United States)

    Frühauff, D.; Glassmeier, K.-H.

    2017-11-01

    In this work, observations of multispacecraft mission Time History of Events and Macroscale Interactions during Substorms are used for statistical investigation of dipolarization fronts in the near-Earth plasma sheet of the magnetotail. Using very stringent criteria, 460 events are detected in almost 10 years of mission data. Minimum variance analysis is used to determine the normal directions of the phase fronts, providing evidence for the existence of a natural symmetry of these phenomena, given by the neutral sheet of the magnetotail. This finding enables the definition of a local coordinate system based on the Tsyganenko model, reflecting the intrinsic orientation of the neutral sheet and, therefore, the dipolarization fronts. In this way, the comparison of events with very different background conditions is improved. Through this study, the statistical results of Liu, Angelopoulos, Runov, et al. (2013) are both confirmed and extended. In a case study, the knowledge of this plane of symmetry helps to explain the concave curvature of dipolarization fronts in the XZ plane through phase propagation speeds of magnetoacoustic waves. A second case study is presented to determine the central current system of a passing dipolarization front through a constellation of three spacecraft. With this information, a statistical analysis of spacecraft observations above and below the neutral sheet is used to provide further evidence for the neutral sheet as the symmetry plane and the central current system. Furthermore, it is shown that the signatures of dipolarization fronts are under certain conditions closely related to that of flux ropes, indicating a possible relationship between these two transient phenomena.

  10. Models of the Origin of the Moon; Early History of Earth and Venus (The Role of Tidal Friction in the Formation of Structure of the Planets)

    Science.gov (United States)

    Pechernikova, G. V.; Ruskol, E. L.

    2017-05-01

    An analytical review of the two contemporary models of the origin of the Earth-Moon system in the process of solid-body accretion is presented: socalled co-accretion model and as a result of a gigantic collision with a planetarysized body (i.e. a megaimpact model). The co-accretion model may be considered as a universal mechanism of the origin of planetary satellites, that accompanies the growth of planets. We consider the conditions of this process that secure the sufficient mass and angular momentum of the protolunar disk such as macroimpacts (collisions with the bodies of asteroidal size) into the mantle of the growing Earth, the role of an lunar embryo growing on the geocentric lunar orbit, its tidal interaction with the Earth. The most difficult remains the explanation of chemical composition of the Moon. Different scenarios of megaimpact are reviewed, in which the Earth's mantle is destroyed and the protosatellite disk is filled mainly by its fragments. There is evaluated amount of energy transferred to the Earth from the evolution of lunar orbit. It is an order of magnitude lower than three main sources of the Earth's interior heat, i.e. the heat of accretion, the energy of differentiation and the heat of radioactive sources. The tidal heating of the Venus's interiors could reach 1000K by slowing its axial initial rotation, in addition to three sources mentioned above in concern of the Earth.

  11. On the importance of the albedo parameterization for the mass balance of the Greenland ice sheet in EC-Earth

    Directory of Open Access Journals (Sweden)

    M. M. Helsen

    2017-08-01

    Full Text Available The albedo of the surface of ice sheets changes as a function of time due to the effects of deposition of new snow, ageing of dry snow, bare ice exposure, melting and run-off. Currently, the calculation of the albedo of ice sheets is highly parameterized within the earth system model EC-Earth by taking a constant value for areas with thick perennial snow cover. This is an important reason why the surface mass balance (SMB of the Greenland ice sheet (GrIS is poorly resolved in the model. The purpose of this study is to improve the SMB forcing of the GrIS by evaluating different parameter settings within a snow albedo scheme. By allowing ice-sheet albedo to vary as a function of wet and dry conditions, the spatial distribution of albedo and melt rate improves. Nevertheless, the spatial distribution of SMB in EC-Earth is not significantly improved. As a reason for this, we identify omissions in the current snow albedo scheme, such as separate treatment of snow and ice and the effect of refreezing. The resulting SMB is downscaled from the lower-resolution global climate model topography to the higher-resolution ice-sheet topography of the GrIS, such that the influence of these different SMB climatologies on the long-term evolution of the GrIS is tested by ice-sheet model simulations. From these ice-sheet simulations we conclude that an albedo scheme with a short response time of decaying albedo during wet conditions performs best with respect to long-term simulated ice-sheet volume. This results in an optimized albedo parameterization that can be used in future EC-Earth simulations with an interactive ice-sheet component.

  12. On the importance of the albedo parameterization for the mass balance of the Greenland ice sheet in EC-Earth

    Science.gov (United States)

    Helsen, Michiel M.; van de Wal, Roderik S. W.; Reerink, Thomas J.; Bintanja, Richard; Madsen, Marianne S.; Yang, Shuting; Li, Qiang; Zhang, Qiong

    2017-08-01

    The albedo of the surface of ice sheets changes as a function of time due to the effects of deposition of new snow, ageing of dry snow, bare ice exposure, melting and run-off. Currently, the calculation of the albedo of ice sheets is highly parameterized within the earth system model EC-Earth by taking a constant value for areas with thick perennial snow cover. This is an important reason why the surface mass balance (SMB) of the Greenland ice sheet (GrIS) is poorly resolved in the model. The purpose of this study is to improve the SMB forcing of the GrIS by evaluating different parameter settings within a snow albedo scheme. By allowing ice-sheet albedo to vary as a function of wet and dry conditions, the spatial distribution of albedo and melt rate improves. Nevertheless, the spatial distribution of SMB in EC-Earth is not significantly improved. As a reason for this, we identify omissions in the current snow albedo scheme, such as separate treatment of snow and ice and the effect of refreezing. The resulting SMB is downscaled from the lower-resolution global climate model topography to the higher-resolution ice-sheet topography of the GrIS, such that the influence of these different SMB climatologies on the long-term evolution of the GrIS is tested by ice-sheet model simulations. From these ice-sheet simulations we conclude that an albedo scheme with a short response time of decaying albedo during wet conditions performs best with respect to long-term simulated ice-sheet volume. This results in an optimized albedo parameterization that can be used in future EC-Earth simulations with an interactive ice-sheet component.

  13. Near-earth Thin Current Sheets and Birkeland Currents during Substorm Growth Phase

    International Nuclear Information System (INIS)

    Sorin Zaharia; Cheng, C.Z.

    2003-01-01

    Two important phenomena observed during the magnetospheric substorm growth phase are modeled: the formation of a near-Earth (|X| ∼ 9 R E ) thin cross-tail current sheet, as well as the equatorward shift of the ionospheric Birkeland currents. Our study is performed by solving the 3-D force-balance equation with realistic boundary conditions and pressure distributions. The results show a cross-tail current sheet with large current (J φ ∼ 10 nA/m 2 ) and very high plasma β (β ∼ 40) between 7 and 10 R E . The obtained region-1 and region-2 Birkeland currents, formed on closed field lines due to pressure gradients, move equatorward and become more intense (J parallel max ∼ 3 (micro)A/m 2 ) compared to quiet times. Both results are in agreement with substorm growth phase observations. Our results also predict that the cross-tail current sheet maps into the ionosphere in the transition region between the region-1 and region-2 currents

  14. Geology of Venus

    International Nuclear Information System (INIS)

    Basilevsky, A.T.; Head, J.W. III.

    1988-01-01

    This paper summarizes the emerging picture of the surface of Venus provided by high-resolution earth-based radar telescopes and orbital radar altimetry and imaging systems. The nature and significance of the geological processes operating there are considered. The types of information needed to complete the picture are addressed. 71 references

  15. Potential of the solid-Earth response for limiting long-term West Antarctic Ice Sheet retreat

    Science.gov (United States)

    Konrad, Hannes; Sasgen, Ingo; Pollard, David; Klemann, Volker

    2016-04-01

    The West Antarctic Ice Sheet (WAIS) is assumed to be inherently unstable because it is grounded below sea level in a large part, where the bedrock deepens from today's grounding line towards the interior of the ice sheet. Idealized simulations have shown that bedrock uplift due to isostatic adjustment of the solid Earth and the associated sea-level fall may stop the retreat of such a marine-based ice sheet (Gomez et al., 2012). Here, we employ a coupled model for ice-sheet dynamics and solid-Earth dynamics, including a gravitationally consistent description of sea level, to investigate the influence of the viscoelastic Earth structure on the WAIS' future stability (Konrad et al. 2015). For this, we start from a steady-state condition for the Antarctic Ice Sheet close to present-day observations and apply atmospheric and oceanic forcing of different strength to initiate the retreat of the WAIS and investigate the effect of the viscoelastic deformation on the ice evolution for a range of solid-Earth rheologies. We find that the climate forcing is the primary control on the occurrence of the WAIS collapse. However, for moderate climate forcing and a weak solid-Earth rheology associated with the West Antarctic rift system (asthenosphere viscosities of 3x10^19 Pa s or less), we find that the combined effect of bedrock uplift and gravitational sea-level fall limits the retreat to the Amundsen Sea embayment on millennial time scales. In contrast, a stiffer Earth rheology yields a collapse under these conditions. Under a stronger climate forcing, weak Earth structures do not prevent the WAIS collapse; however, they produce a delay of up to 5000 years in comparison to a stiffer solid-Earth rheology. In an additional experiment, we test the impact of sea-level rise from an assumed fast deglaciation of the Greenland Ice Sheet. In cases when the climatic forcing is too weak to force WAIS collapse by itself, the additional rise in sea-level leads to disintegration of the WAIS

  16. The structure of strongly tilted current sheets in the Earth magnetotail

    Directory of Open Access Journals (Sweden)

    I. Y. Vasko

    2014-02-01

    Full Text Available We investigate strongly tilted (in the y–z GSM plane current sheets (CSs in the Earth magnetotail using data from the Cluster mission. We analyze 29 CS crossings observed in 2001–2004. The characteristic current density, magnetic field at the CS boundary and the CS thickness of strongly tilted CSs are similar to those reported previously for horizontal (not tilted CSs. We confirm that strongly tilted CSs are generally characterized by a rather large northward component of the magnetic field. The field-aligned current in strongly tilted CSs is on average two times larger than the transverse current. The proton adiabaticity parameter, κp, is larger than 0.5 in 85% of strongly tilted CSs due to the large northward magnetic field. Thus, the proton dynamics is stochastic for 18 current sheets with 0.5 p p > 3, whereas electrons are magnetized for all observed current sheets. Strongly tilted CSs provide a unique opportunity to measure the electric field component perpendicular to the CS plane. We find that most of the electric field perpendicular to the CS plane is due to the decoupling of electron and ion motions (plasma polarization. For 27 CSs we determine profiles of the electrostatic potential, which is due to the plasma polarization. Drops in the potential between the neutral plane and the CS boundary are within the range of 200 V to 12 kV, while maximal values of the electric field are within the range of 0.2 mV m−1 to 8 mV m−1. For 16 CSs the observed potentials are in accordance with Ohm's law, if the electron current density is assumed to be comparable to the total current density. In 15 of these CSs the profile of the polarization potential is approximately symmetric with respect to the neutral plane and has minimum therein.

  17. Streaming sausage, kink and tearing instabilities in a current sheet with applications to the earth's magnetotail

    Science.gov (United States)

    Lee, L. C.; Wang, S.; Wei, C. Q.; Tsurutani, B. T.

    1988-01-01

    This paper investigates the growth rates and eigenmode structures of the streaming sausage, kink, and tearing instabilities in a current sheet with a super-Alfvenic flow. The growth rates and eigenmode structures are first considered in the ideal incompressible limit by using a four-layer model, as well as a more realistic case in which all plasma parameters and the magnetic field vary continuously along the direction perpendicular to the magnetic field and plasma flow. An initial-value method is applied to obtain the growth rate and eigenmode profiles of the fastest growing mode, which is either the sausage mode or kink mode. It is shown that, in the earth's magnetotail, where super-Alfvenic plasma flows are observed in the plasma sheet and the ratio between the plasma and magnetic pressures far away from the current layer is about 0.1-0.3 in the lobes, the streaming sausage and streaming tearing instabilities, but not kink modes, are likely to occur.

  18. Is Venus alive?

    Science.gov (United States)

    Taylor, Harry A., Jr.

    Apart from the earth, the near environment of only one other planet, Venus, has been the subject of sustained in situ investigations from space. Owing to the similarity in the physical characteristics of the two bodies, this is most appropriate in that it provides the opportunity to test the credo that through comparative analysis, planetary exploration holds the promise for better understanding of our earth environment.The Pioneer Venus Orbiter was placed into orbit about Venus in December 1978 and has provided a wealth of observations of the planet surface, its atmosphere and clouds, the ionosphere, and the interaction of the solar wind and interplanetary magnetic field with the planetary environment. Among these observations, perhaps the most potentially significant and yet controversial result has been the claimed evidence of extensive lightning and the coupled assertion that the lightning is stimulated by volcanic activity. This lightning- volcanism scenario has become widely publicized in films, books, and numerous journal and magazine articles. Also, these results have had considerable influence in stimulating ongoing research on the basis that active volcanic output might explain otherwise unanswered questions in wide-ranging disciplines, including atmospheric and cloud physics, geology, and plasma physics. Quite naturally, the question of whether Venus is geologically either living or dead is fundamentally significant for comparative planetary analysis.

  19. Magnetospheric Multiscale Mission Observations of Magnetic Flux Ropes in the Earth's Plasma Sheet

    Science.gov (United States)

    Slavin, J. A.; Akhavan-Tafti, M.; Poh, G.; Le, G.; Russell, C. T.; Nakamura, R.; Baumjohann, W.; Torbert, R. B.; Gershman, D. J.; Pollock, C. J.; Giles, B. L.; Moore, T. E.; Burch, J. L.

    2017-12-01

    A major discovery by the Cluster mission and the previous generation of science missions is the presence of earthward and tailward moving magnetic flux ropes in the Earth's plasma sheet. However, the lack of high-time resolution plasma measurements severely limited progress concerning the formation and evolution of these reconnection generated structures. We use high-time resolution magnetic and electric field and plasma measurements from the Magnetospheric Multiscale mission's first tail season to investigate: 1) the distribution of flux rope diameters relative to the local ion and electron inertial lengths; 2) the internal force balance sustaining these structures; and 3) the magnetic connectivity of the flux ropes to the Earth and/or the interplanetary medium; 4) the specific entropy of earthward moving flux ropes and the possible effect of "buoyancy" on how deep they penetrate into the inner magnetosphere; and 5) evidence for coalescence of adjacent flux ropes and/or the division of existing flux ropes through the formation of secondary X-lines. The results of these initial analyses will be discussed in terms of their implications for reconnection-driven magnetospheric dynamics and substorms.

  20. Calculation of mass discharge of the Greenland ice sheet in the Earth System Model

    Directory of Open Access Journals (Sweden)

    O. O. Rybak

    2016-01-01

    Full Text Available Mass discharge calculation is a challenging task for the ice sheet modeling aimed at evaluation of their contribution to the global sea level rise during past interglacials, as well as one of the consequences of future climate change. In Greenland, ablation is the major source of fresh water runoff. It is approximately equal to the dynamical discharge (iceberg calving. Its share might have still larger during the past interglacials when the margins of the GrIS retreated inland. Refreezing of the melted water and its retention are two poorly known processes playing as a counterpart of melting and, thus, exerting influence on the run off. Interaction of ice sheets and climate is driven by energy and mass exchange processes and is complicated by numerous feed-backs. To study the complex of these processes, coupling of an ice sheet model and a climate model (i.e. models of the atmosphere and the ocean in one model is required, which is often called the Earth System Model (ESM. Formalization of processes of interaction between the ice sheets and climate within the ESM requires elaboration of special techniques to deal with dramatic differences in spatial and temporal variability scales within each of three ESM’s blocks. In this paper, we focus on the method of coupling of a Greenland ice sheet model (GrISM with the climate model INMCM having been developed in the Institute of Numerical Mathematics of Russian Academy of Sciences. Our coupling approach consists in applying of a special buffer model, which serves as an interface between GrISM and INMCM. A simple energy and water exchange model (EWBM-G allows realistic description of surface air temperature and precipitation fields adjusted to a relief of elevation of the GrIS surface. In a series of diagnostic numerical experiments with the present-day GrIS geometry and the modeled climate we studied sensitivity of the modeled surface mass balance and run off to the key EWBM-G parameters and compared

  1. Geothermal Heat Flux: Linking Deep Earth's Interior and the Dynamics of Large-Scale Ice Sheets

    Science.gov (United States)

    Rogozhina, Irina; Vaughan, Alan

    2014-05-01

    Regions covered by continental-scale ice sheets have the highest degree of uncertainty in composition and structure of the crust and lithospheric mantle, compounded by the poorest coverage on Earth of direct heat flow measurements. In addition to challenging conditions that make direct measurements and geological survey difficult Greenland and Antarctica are known to be geologically complex. Antarctica in particular is marked by two lithospherically distinct zones. In contrast to young and thin lithosphere of West Antarctica, East Antarctica is a collage of thick Precambrian fragments of Gondwana and earlier supercontinents. However, recent observations and modeling studies have detected large systems of subglacial lakes extending beneath much of the East Antarctic ice sheet base that have been linked to anomalously elevated heat flow. Outcrop samples from the rift margin with Australia (Prydz Bay) have revealed highly radiogenic Cambrian granite intrusives that are implicated in regional increase of crustal heat flux by a factor of two to three compared to the estimated continental background. Taken together, these indicate high variability of heat flow and properties of rocks across Antarctica. Similar conclusions have been made based on direct measurements and observations of the Greenland ice sheet. Airborne ice-penetrating radar and deep ice core projects show very high rates of basal melt for parts of the ice sheet in northern and central Greenland that have been explained by abnormally high heat flux. Archaean in age, the Greenland lithosphere was significantly reworked during the Early Proterozoic. In this region, the interpretation of independent geophysical data is complicated by Proterozoic and Phanerozoic collision zones, compounded by strong thermochemical effects of rifting along the western and eastern continental margins between 80 and 25 million years ago. In addition, high variability of heat flow and thermal lithosphere structure in central

  2. Unified model of low-frequency electromagnetic modes in the anisotropic current sheet of the Earth's magnetotail.

    Science.gov (United States)

    Zelenyi, Lev; Malova, H.; Artemyev, A.; Popov, V.

    Experimental investigation of the Earth's magnetosphere indicates that there is close coupling between the global magnetospheric dynamics and characteristic properties of the magnetotail current sheet (CS). The investigation of CS stability is developed in a frame of analytical self-consistent model of a thin anisotropic current sheet with anisotropic pressure tensor. Ion population is considered in quasiadiabatic approximation, electrons are taken into account in Boltzman approximation. The general case of oblique perturbations with an arbitrary polarization is studied including tearing, kink, sausage and twist modes. In a frame of the linear perturbation theory it is shown that thin current sheets have larger free energy than the well known isotropic ones. It is demonstrated that, contrary to stable Harris-type current sheets, there exists certain "gaps" in the parameter space where system could become unstable for tearing perturbation. The investigation of the development of an oblique perturbation modes demonstrated the possibility of the growth of other low frequency electromagnetic instabilities such kink and sausage modes. Generally, unstable modes exist for any arbitrary angle of propagation while tearing and twist modes are most unstable for propagation along Bx, while kink and sausage modes have maximum growth rate for propagation along current. Our studies might have important implications for understanding magnetospheric dynamics during substorm activization, e.g. current sheet evolution, destruction, flapping and other dynamic plasma processes in the Earth's magnetotail.

  3. Gravity field of Venus - A preliminary analysis

    Science.gov (United States)

    Phillips, R. J.; Sjogren, W. L.; Abbott, E. A.; Smith, J. C.; Wimberly, R. N.; Wagner, C. A.

    1979-01-01

    The gravitational field of Venus obtained by tracking the Pioneer Venus Orbiter is examined. For each spacecraft orbit, two hours of Doppler data centered around periapsis were used to estimate spacecraft position and velocity and the velocity residuals obtained were spline fit and differentiated to produce line of sight gravitational accelerations. Consistent variations in line of sight accelerations from orbit to orbit reveal the presence of gravitational anomalies. A simulation of isostatic compensation for an elevated region on the surface of Venus indicates that the mean depth of compensation is no greater than about 100 km. Gravitational spectra obtained from a Fourier analysis of line of sight accelerations from selected Venus orbits are compared to the earth's gravitational spectrum and spherical harmonic gravitational potential power spectra of the earth, the moon and Mars. The Venus power spectrum is found to be remarkably similar to that of the earth, however systematic variations in the harmonics suggest differences in dynamic processes or lithospheric behavior.

  4. Thin current sheets observation by MMS during a near-Earth's magnetotail reconnection event

    Science.gov (United States)

    Nakamura, R.; Varsani, A.; Nakamura, T.; Genestreti, K.; Plaschke, F.; Baumjohann, W.; Nagai, T.; Burch, J.; Cohen, I. J.; Ergun, R.; Fuselier, S. A.; Giles, B. L.; Le Contel, O.; Lindqvist, P. A.; Magnes, W.; Schwartz, S. J.; Strangeway, R. J.; Torbert, R. B.

    2017-12-01

    During summer 2017, the four spacecraft of the Magnetospheric Multiscale (MMS) mission traversed the nightside magnetotail current sheet at an apogee of 25 RE. They detected a number of flow reversal events suggestive of the passage of the reconnection current sheet. Due to the mission's unprecedented high-time resolution and spatial separation well below the ion scales, structure of thin current sheets is well resolved both with plasma and field measurements. In this study we examine the detailed structure of thin current sheets during a flow reversal event from tailward flow to Earthward flow, when MMS crossed the center of the current sheet . We investigate the changes in the structure of the thin current sheet relative to the X-point based on multi-point analysis. We determine the motion and strength of the current sheet from curlometer calculations comparing these with currents obtained from the particle data. The observed structures of these current sheets are also compared with simulations.

  5. Venus volcanism and El Chichon

    Science.gov (United States)

    Bell, Peter M.

    Reinterpretations of telemetry data returned to earth from the Pioneer Venus Orbiter suggest that the surface of Venus may be characterized by violent immense volcanic activity. L.W. Esposito has made an interactive analysis of Pioneer ultraviolet spectral data and similar data from the earth's atmosphere [Science, 223, 1072-1074, 1984]. Spacecraft analysis of sulfur dioxide in the earth's upper atmosphere, apparently released by El Chich[acu]on, Mexico, in March 1982 (EOS, June 14, 1983, p. 411, and August 16, 1983, p. 506) prompted reanalysis of accumulated Pioneer ultraviolet data. Massive injections of sulfur dioxide into the Venus atmosphere could be the result of volcanic eruptions about the size of the Krakatoa explosive eruption that took place between Java and Summatra in 1883.

  6. Spontaneous magnetic fluctuations and collisionless regulation of the Earth's plasma sheet

    Science.gov (United States)

    Moya, P. S.; Espinoza, C.; Stepanova, M. V.; Antonova, E. E.; Valdivia, J. A.

    2017-12-01

    Even in the absence of instabilities, plasmas often exhibit inherent electromagnetic fluctuations which are present due to the thermal motion of charged particles, sometimes called thermal (quasi-thermal) noise. One of the fundamental and challenging problems of laboratory, space, and astrophysical plasma physics is the understanding of the relaxation processes of nearly collisionless plasmas, and the resultant state of electromagnetic plasma turbulence. The study of thermal fluctuations can be elegantly addressed by using the Fluctuation-Dissipation Theorem that describes the average amplitude of the fluctuations through correlations of the linear response of the media with the perturbations of the equilibrium state (the dissipation). Recently, it has been shown that solar wind plasma beta and temperature anisotropy observations are bounded by kinetic instabilities such as the ion cyclotron, mirror, and firehose instabilities. The magnetic fluctuations observed within the bounded area are consistent with the predictions of the Fluctuation-Dissipation theorem even far below the kinetic instability thresholds, with an enhancement of the fluctuation level near the thresholds. Here, for the very first time, using in-situ magnetic field and plasma data from the THEMIS spacecraft, we show that such regulation also occurs in the Earth's plasma sheet at the ion scales and that, regardless of the clear differences between the solar wind and the magnetosphere environments, spontaneous fluctuation and their collisionless regulation seem to be fundamental features of space and astrophysical plasmas, suggesting the universality of the processes.

  7. A practical approach to the disposal of highly toxic and long-lived spent nuclear fuel waste between Venus and Earth

    International Nuclear Information System (INIS)

    Ehricke, K.A.

    1983-01-01

    Extraterrestrial disposal, while not the only alternative, nevertheless assures definite and irreversible removal of the most toxic and long-lived waste from the biosphere. The disposal 'site' should lie at minimum safe transfer energy level. Primary candidate is the space between Venus and Earth. The number of propulsion phases should be a minimum, preferably only one. Lunar gravity assist can be helpful to achieve higher inclination of the heliocentric orbit relative to the ecliptic. Solidified spent fuel isotopes and actinides, sufficient to reduce the residual terrestrial waste to the radiation level of natural uranium deposits after 30 to 40 yr instead of 1000 to 1500 yr, is deposited into heliocentric orbits. Transportation systems, requirements, costs and the associated socio-economic benefit potentials of an environmentally more benign and a more vigorous nuclear power generation program are presented. Prior to solidification, an interim storage of 10 yr, following removal from the reactor, may be required. The Shuttle, with one Orbiter modified as Nuclear Waste Carrying Orbiter and an out of near-Earth orbit booster, provides a safe and economic transportation system at disposal mission costs from surface to disposal orbit of less than 0.5 cents/kWhe or <= 0.1 cent/kWhe depending on level of orbital operations. Details are discussed. (author)

  8. Meeting Venus

    Science.gov (United States)

    Sterken, Christiaan; Aspaas, Per Pippin

    2013-06-01

    On 2-3 June 2012, the University of Tromsoe hosted a conference about the cultural and scientific history of the transits of Venus. The conference took place in Tromsoe for two very specific reasons. First and foremost, the last transit of Venus of this century lent itself to be observed on the disc of the Midnight Sun in this part of Europe during the night of 5 to 6 June 2012. Second, several Venus transit expeditions in this region were central in the global enterprise of measuring the scale of the solar system in the eighteenth century. The site of the conference was the Nordnorsk Vitensenter (Science Centre of Northern Norway), which is located at the campus of the University of Tromsoe. After the conference, participants were invited to either stay in Tromsoe until the midnight of 5-6 June, or take part in a Venus transit voyage in Finnmark, during which the historical sites Vardoe, Hammerfest, and the North Cape were to be visited. The post-conference program culminated with the participants observing the transit of Venus in or near Tromsoe, Vardoe and even from a plane near Alta. These Proceedings contain a selection of the lectures delivered on 2-3 June 2012, and also a narrative description of the transit viewing from Tromsoe, Vardoe and Alta. The title of the book, Meeting Venus, refers the title of a play by the Hungarian film director, screenwriter and opera director Istvan Szabo (1938-). The autobiographical movie Meeting Venus (1991) directed by him is based on his experience directing Tannhauser at the Paris Opera in 1984. The movie brings the story of an imaginary international opera company that encounters a never ending series of difficulties and pitfalls that symbolise the challenges of any multicultural and international endeavour. As is evident from the many papers presented in this book, Meeting Venus not only contains the epic tales of the transits of the seventeenth, eighteenth and nineteenth centuries, it also covers the conference

  9. Energetic particle beams in the plasma sheet boundary layer following substorm expansion - Simultaneous near-earth and distant tail observations

    Science.gov (United States)

    Scholer, M.; Baker, D. N.; Gloeckler, G.; Ipavich, F. M.; Galvin, A. B.; Klecker, B.; Terasawa, T.; Tsurutani, B. T.

    1986-01-01

    Simultaneous observations of ions and electron beams in the near-earth and deep magnetotail following the onset of substorm are analyzed in terms of the substorm neutral line model. The observations were collected on March 20, 1983 with ISSE 1 and 3. Energy fluxes and intensity-time profiles of protons and electrons are studied. The data reveal that the reconnection at the near-earth neutral line produces ions and electrons for the plasma sheet boundary layer. The maximum electric potential along the neutral line is evaluated.

  10. Venus Middle Atmosphere Chemistry

    Science.gov (United States)

    Mills, F. P.; Sundaram, M.; Slanger, T. G.; Allen, M.; Yung, Y. L.

    2005-08-01

    Venus is the most similar planet to Earth, and years of research have sought to understand their similarities and differences. Yet, it is still not clear what chemical processes maintain the long-term stability of Venus' primarily CO2 atmosphere. CO2 dissociates into CO and O after absorbing photons at wavelengths Express will be reviewed. Recent work evaluating newly proposed mechanisms for producing CO2, which could be important depending on the rates of poorly constrained reactions, will be described. This research was supported by funding from NASA's Planetary Atmospheres program and the Australian Research Council. Part of this work was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. [1] Nair, et al., Icarus 111, 124 (1994), [2] Trauger and Lunine, Icarus 55, 272 (1983), [3] Pernice, et al., PNAS 101, 14007 (2004)

  11. Rate of volcanism on Venus

    International Nuclear Information System (INIS)

    Fegley, B. Jr.; Prinn, R.G.

    1988-07-01

    The maintenance of the global H 2 SO 4 clouds on Venus requires volcanism to replenish the atmospheric SO 2 which is continually being removed from the atmosphere by reaction with calcium minerals on the surface of Venus. The first laboratory measurements of the rate of one such reaction, between SO 2 and calcite (CaCO 3 ) to form anhydrite (CaSO 4 ), are reported. If the rate of this reaction is representative of the SO 2 reaction rate at the Venus surface, then we estimate that all SO 2 in the Venus atmosphere (and thus the H 2 SO 4 clouds) will be removed in 1.9 million years unless the lost SO 2 is replenished by volcanism. The required rate of volcanism ranges from about 0.4 to about 11 cu km of magma erupted per year, depending on the assumed sulfur content of the erupted material. If this material has the same composition as the Venus surface at the Venera 13, 14 and Vega 2 landing sites, then the required rate of volcanism is about 1 cu km per year. This independent geochemically estimated rate can be used to determine if either (or neither) of the two discordant (2 cu km/year vs. 200 to 300 cu km/year) geophysically estimated rates is correct. The geochemically estimated rate also suggests that Venus is less volcanically active than the Earth

  12. Greenland ice sheet beyond 2100: Simulating its evolution and influence using the coupled climate-ice sheet model EC-Earth - PISM

    Science.gov (United States)

    Yang, S.; Christensen, J. H.; Madsen, M. S.; Ringgaard, I. M.; Petersen, R. A.; Langen, P. P.

    2017-12-01

    Greenland ice sheet (GrIS) is observed undergoing a rapid change in the recent decades, with an increasing area of surface melting and ablation and a speeding mass loss. Predicting the GrIS changes and their climate consequences relies on the understanding of the interaction of the GrIS with the climate system on both global and local scales, and requires climate model systems incorporating with an explicit and physically consistent ice sheet module. In this work we study the GrIS evolution and its interaction with the climate system using a fully coupled global climate model with a dynamical ice sheet model for the GrIS. The coupled model system, EC-EARTH - PISM, consisting of the atmosphere-ocean-sea ice model system EC-EARTH, and the Parallel Ice Sheet Model (PISM), has been employed for a 1400-year simulation forced by CMIP5 historical forcing from 1850 to 2005 and continued along an extended RCP8.5 scenario with the forcing peaking at 2200 and stabilized hereafter. The simulation reveals that, following the anthropogenic forcing increase, the global mean surface temperature rapidly rises about 10 °C in the 21st and 22nd century. After the forcing stops increasing after 2200, the temperature change slows down and eventually stabilizes at about 12.5 °C above the preindustrial level. In response to the climate warming, the GrIS starts losing mass slowly in the 21st century, but the ice retreat accelerates substantially after 2100 and ice mass loss continues hereafter at a constant rate of approximately 0.5 m sea level rise equivalence per 100 years, even as the warming rate gradually levels off. Ultimately the volume and extent of GrIS reduce to less than half of its preindustrial value. To understand the interaction of GrIS with the climate system, the characteristics of atmospheric and oceanic circulation in the warm climate are analyzed. The circulation patterns associated with the negative surface mass balance that leads to GrIS retreat are investigated

  13. Implications of the (H2O)n + CO ↔ trans-HCOOH + (H2O)n-1 (n = 1, 2, and 3) reactions for primordial atmospheres of Venus and Earth

    Science.gov (United States)

    Vichietti, R. M.; Spada, R. F. K.; da Silva, A. B. F.; Machado, F. B. C.; Haiduke, R. L. A.

    2018-04-01

    The forward and backward (H2O)n + CO ↔ HCOOH + (H2O)n-1 (n = 1, 2, and 3) reactions were studied in order to furnish trustworthy thermochemical and kinetic data. Stationary point structures involved in these chemical processes were achieved at the B2PLYP/cc-pVTZ level so that the corresponding vibrational frequencies, zero-point energies, and thermal corrections were scaled to consider anharmonicity effects. A complete basis set extrapolation was also employed with the CCSD(T) method in order to improve electronic energy descriptions and providing therefore more accurate results for enthalpies, Gibbs energies, and rate constants. Forward and backward rate constants were encountered at the high-pressure limit between 200 and 4000 K. In turn, modified Arrhenius' equations were fitted from these rate constants (between 700 and 4000 K). Next, considering physical and chemical conditions that have supposedly prevailed on primitive atmospheres of Venus and Earth, our main results indicate that 85-88 per cent of all water forms on these atmospheres were monomers, whereas (H2O)2 and (H2O)3 complexes would represent 12-15 and ˜0 per cent, respectively. Besides, we estimate that Earth's and Venus' primitive atmospheres could have been composed by ˜0.001-0.003 per cent of HCOOH when their temperatures were around 1000-2000 K. Finally, the water loss process on Venus may have occurred by a mechanism that includes the formic acid as intermediate species.

  14. Return to Venus of AKATSUKI, the Japanese Venus Orbiter

    Science.gov (United States)

    Nakamura, M.; Iwagami, N.; Satoh, T.; Taguchi, M.; Watanabe, S.; Takahashi, Y.; Imamura, T.; Suzuki, M.; Ueno, M.; Yamazaki, A.; Fukuhara, T.; Yamada, M.; Ishii, N.; Ogohara, K.

    2011-12-01

    Japanese Venus Climate Orbiter 'AKATSUKI' (PLANET-C) was proposed in 2001 with strong support by international Venus science community and approved as an ISAS mission soon after the proposal. AKATSUKI and ESA's Venus Express complement each other in Venus climate study. Various coordinated observations using the two spacecraft have been planned. Also participating scientists from US have been selected. Its science target is to understand the climate of Venus. The mission life we expected was more than 2 Earth years in Venus orbit. AKATSUKI was successfully launched at 06:58:22JST on May 21, by H-IIA F17. After the separation from H-IIA, the telemetry from AKATSUKI was normally detected by DSN Goldstone station (10:00JST) and the solar cell paddles' expansion was confirmed. AKATSUKI was put into the 3-axis stabilized mode in the initial operation from Uchinoura station and the critical operation was finished at 20:00JST on the same day. The malfunction, which happened during the Venus Orbit Insertion (VOI) on7 Dec, 2010 is as follows. We set all commands on Dec. 5. Attitude control for Venus orbit insertion (VOI) was automatically done on Dec. 6. Orbital maneuver engine (OME) was fired 08:49 JST on Dec. 7. 1min. after firing the spacecraft went into the occultation region and we had no telemetry, but we expected to continuous firing for 12min. Recording on the spacecraft told us later that, unfortunately the firing continued just 152sec. and stopped. The reason of the malfunction of the OME was the blocking of check valve of the gas pressure line to push the fuel to the engine. We failed to make the spacecraft the Venus orbiter, and it is rotating the sun with the orbital period of 203 days. As the Venus orbit the sun with the period of 225 days, AKATSUKI has a chance to meet Venus again in 5 or 6 years depending on the orbit correction plan. Let us summarize the present situation of AKATSUKI. Most of the fuel still remains. But the condition of the propulsion

  15. The Plains of Venus

    Science.gov (United States)

    Sharpton, V. L.

    2013-12-01

    extremely fluid flows (i.e., channel formers), to viscous, possibly felsic lavas of steep-sided domes. Wrinkle ridges deform many plains units and this has been taken to indicate that these ridges essentially form an early stratigraphic marker that limits subsequent volcanism to a minimum. However, subtle backscatter variations within many ridged plains units suggest (but do not prove) that some plains volcanism continued well after local ridge deformation ended. Furthermore, many of volcanic sources show little, if any, indications of tectonic modification and detailed analyses have concluded that resurfacing rates could be similar to those on Earth. Improving constraints on the rates and styles of volcanism within the plains could lend valuable insights into the evolution of Venus's internal heat budget and the transition from thin-lid to thick-lid tectonic regimes. Improved spatial and radiometric resolution of radar images would greatly improve abilities to construct the complex local stratigraphy of ridged plains. Constraining the resurfacing history of Venus is central to understanding how Earth-sized planets evolve and whether or not their evolutionary pathways lead to habitability. This goal can only be adequately addressed if broad coverage is added to the implementation strategies of any future mapping missions to Venus.

  16. Venus's southern polar vortex reveals precessing circulation.

    Science.gov (United States)

    Luz, D; Berry, D L; Piccioni, G; Drossart, P; Politi, R; Wilson, C F; Erard, S; Nuccilli, F

    2011-04-29

    Initial images of Venus's south pole by the Venus Express mission have shown the presence of a bright, highly variable vortex, similar to that at the planet's north pole. Using high-resolution infrared measurements of polar winds from the Venus Express Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument, we show the vortex to have a constantly varying internal structure, with a center of rotation displaced from the geographic south pole by ~3 degrees of latitude and that drifts around the pole with a period of 5 to 10 Earth days. This is indicative of a nonsymmetric and varying precession of the polar atmospheric circulation with respect to the planetary axis.

  17. Evolution of Topographic Stress Perturbations Near the Surface of the Earth and Application to Sheeting Joints

    Science.gov (United States)

    Martel, S. J.

    2014-12-01

    Topography perturbs the near-surface stress fields caused by gravity and by regional horizontal stresses. Two-dimensional analytical solutions for elastic stresses in uniform, isotropic rock allow the effects of gravity and a uniform regional horizontal stress P to be distinguished beneath isolated bell-shaped ridges and valleys. The topographic stress perturbations vary depending on the shape of the topography. Gravity, by itself, causes surface-perpendicular and surface-parallel compressive stresses beneath the crest of a bell-shaped ridge. Regional compression contributes a surface-parallel compression atop broad gentle bell-shaped ridges with steepest slopes less than 45°, but a surface-parallel tension atop narrower ridges with steeper slopes. If P is an order of magnitude less compressive than rg|b|, where r is rock density, g is gravitational acceleration, and b is the topographic relief, then effects of gravity dominate effects of the regional compression near the topographic surface. Conversely, if P is an order of magnitude more compressive than rg|b|, then effects of regional compression dominate the effects of gravity, and tensile stresses can develop normal to the surface beneath gentle convex bell-shaped ridges and the convex portions of bell-shaped valleys. The latter conditions promote the widespread development of sheeting joints. The locations of topographic inflection points help define where sheeting joints can develop at a particular time. As erosion progresses and the shape of the topographic surface changes, sheeting joints can form in new areas and be left as relict structures in others. The distribution of sheeting joints thus reflects the dynamic response of geologic systems that evolve through time.

  18. Physical and numerical modelling of earth pressure on anchored sheet pile walls in sand

    DEFF Research Database (Denmark)

    Krogsbøll, Anette Susanne; Fuglsang, Leif D

    2006-01-01

    The influence of wall flexibility on earth pressure, bending moments and failure modes is studied. Numerical models are compared to results from model tests carried out in a geotechnical centrifuge. The back-fill is dry sand and failure is introduced by allowing the wall to rotate around the anchor......-model showed the right behaviour in pre-failure as well as failure for both flexible and stiff walls, whereas the MC-model showed some shortcomings when stiff walls were modelled....

  19. Physical and numerical modelling of earth pressure on anchored sheet pile walls in sand

    DEFF Research Database (Denmark)

    Krogsbøll, Anette Susanne; Fuglsang, Leif D

    The influence of wall flexibility on earth pressure, bending moments and failure modes is studied. Numerical models are compared to results from model tests carried out in a geotechnical centrifuge. The back-fill is dry sand and failure is introduced by allowing the wall to rotate around the anchor......-model showed the right behaviour in pre-failure as well as failure for both flexible and stiff walls, whereas the MC-model showed some shortcomings when stiff walls were modelled....

  20. Venus Exploration opportunities within NASA's Solar System Exploration roadmap

    Science.gov (United States)

    Balint, Tibor; Thompson, Thomas; Cutts, James; Robinson, James

    2006-01-01

    Science goals to understand the origin, history and environment of Venus have been driving international space exploration missions for over 40 years. Past missions include the Magellan and Pioneer-Venus missions by the US; the Venera program by the USSR; and the Vega missions through international cooperation. Furthermore, the US National Research Council (NRC), in the 2003 Solar System Exploration (SSE) Decadal Survey, identified Venus as a high priority target, thus demonstrating a continuing interest in Earth's sister planet. In response to the NRC recommendation, the 2005 NASA SSE Roadmap included a number of potential Venus missions arching through all mission classes from small Discovery, to medium New Frontiers and to large Flagship class missions. While missions in all of these classes could be designed as orbiters with remote sensing capabilities, the desire for scientific advancements beyond our current knowledge - including what we expect to learn from the ongoing ESA Venus Express mission - point to in-situ exploration of Venus.

  1. Reassessment of planetary protection requirements for Venus missions

    Science.gov (United States)

    Szostak, J.; Riemer, R.; Smith, D.; Rummel, J.

    In 2005 the US Space Studies Board SSB was asked by NASA to reexamine the planetary protection requirements for spacecraft missions to Venus In particular the SSB was tasked to 1 Assess the surface and atmospheric environments of Venus with respect to their ability to support the survival and growth of Earth-origin microbial contamination by future spacecraft missions and 2 Provide recommendations related to planetary protection issues associated with the return to Earth of samples from Venus The task group established by the SSB to address these issues assessed the known aspects of the present-day environment of Venus and the ability of Earth organisms to survive in the physical and chemical conditions found on the planet s surface or in the clouds in the planet s atmosphere As a result of its deliberations the task group found compelling evidence against there being significant dangers of forward or reverse biological contamination as a result of contact between a spacecraft and the surface of Venus or the clouds in the atmosphere of Venus regardless of the current unknowns The task group did however conclude that Venus is a body of interest relative to the process of chemical evolution and the origin of life As a result the task group endorses NASA s current policy of subjecting missions to Venus to the requirements imposed by planetary protection Category II rather than the less restrictive Category I recommended by COSPAR

  2. Modeling the Self-organized Critical Behavior of Earth's Plasma Sheet Reconnection Dynamics

    Science.gov (United States)

    Klimas, Alexander J.

    2006-01-01

    Analyses of Polar UVI auroral image data show that bright night-side high-latitude W emissions exhibit so many of the key properties of systems in self-organized criticality that an alternate interpretation has become virtually impossible. These analyses will be reviewed. It is now necessary to find and model the source of this behavior. We note that the most common models of self-organized criticality are numerical sandpiles. These are, at root, models that govern the transport of some quantity from a region where it is loaded to another where it is unloaded. Transport is enabled by the excitation of a local threshold instability; it is intermittent and bursty, and it exhibits a number of scale-free statistical properties. Searching for a system in the magnetosphere that is analogous and that, in addition, is known to produce auroral signatures, we focus on the reconnection dynamics of the magnetotail plasma sheet. In our previous work, a driven reconnection model has been constructed and has been under study. The transport of electromagnetic (primarily magnetic) energy carried by the Poynting flux into the reconnection region of the model has been examined. All of the analysis techniques (and more) that have been applied to the auroral image data have also been applied to this Poynting flux. New results will be presented showing that this model also exhibits so many of the key properties of systems in self-organized criticality that an alternate interpretation is implausible. A strong correlation between these key properties of the model and those of the auroral UV emissions will be demonstrated. We suggest that, in general, the driven reconnection model is an important step toward a realistic plasma physical model of self-organized criticality and we conclude, more specifically, that it is also a step in the right direction toward modeling the multiscale reconnection dynamics of the magnetotail.

  3. Venus Express ready for lift-off

    Science.gov (United States)

    2005-10-01

    Venus Express is Europe’s first mission to Venus, a place of many mysteries that scientists are still eager to solve. Principal among those mysteries is why a planet so similar to the Earth in size, mass, and composition has evolved so differently over the course of the last 4.6 billion years. ESA’s ESOC establishment, the Space Operations Centre in Darmstadt, Germany will control the mission and organise a launch event from 06:00 to 12:00. A live televised transmission of the launch will bring images from Baikonur to broadcasters and the general public. ESA senior management and specialists will be on hand at ESOC and at other ESA establishments for explanations and interviews. All live transmissions are carried free-to-air. For broadcasters, complete details of the various satellite feeds (on Eutelsat W2) are listed at http://television.esa.int. For the general public, a launch transmission via Astra 1G has again been organised, with all schedule and transmission details online at http://television.esa.int/photos/Astra.pdf On the occasion of the launch of Venus Express, the Planetary Society has teamed up with ESA to invite youths and adults worldwide to enter a Venus Express Art Contest. The theme of the contest is "Postcards from Venus". Entrants are invited to imagine the surface of Venus from an above-ground perspective. The winner will be invited to follow the Venus Orbit Insertion event at ESA's control centre in Darmstadt, Germany, on 6 April 2006. More on the constest at http://planetary.org/postcards_from_venus/ Media representatives wishing to follow the event at ESA/ESOC, or the retransmission at other ESA establishments, are requested to fill in the attached registration form and fax it back to the place of their choice.

  4. VICI (Venus In Situ Composition Investigations): The Next Step in Understanding Venus Climate Evolution

    Science.gov (United States)

    Glaze, L. S.; Garvin, J. B.

    2017-12-01

    Venus provides a natural laboratory to explore an example of terrestrial planet evolution that may be cosmically ubiquitous. By better understanding the composition of the Venus atmosphere and surface, we can better constrain the efficiency of the Venusian greenhouse. VICI is a proposed NASA New Frontiers mission that delivers two landers to Venus on two separate Venus fly-bys. Following six orbital remote sensing missions to Venus (since 1978), VICI would be the first mission to land on the Venus surface since 1985, and the first U.S. mission to enter the Venus atmosphere in 49 years. The four major VICI science objectives are: Atmospheric origin and evolution: Understand the origin of the Venus atmosphere, how it has evolved, including how recently Venus lost its oceans, and how and why it is different from the atmospheres of Earth and Mars, through in situ measurements of key noble gases, nitrogen, and hydrogen. Atmospheric composition and structure: Reveal the unknown chemical processes and structure in Venus' deepest atmosphere that dominate the current climate through two comprehensive, in situ vertical profiles. Surface properties and geologic evolution: For the first time ever, explore the tessera from the surface, specifically to test hypotheses of ancient content-building cycles, erosion, and links to past climates using multi-point mineralogy, elemental chemistry, imaging and topography. Surface-atmosphere interactions: Characterize Venus' surface weathering environment and provide insight into the sulfur cycle at the surface-atmosphere interface by integrating rich atmospheric composition and structure datasets with imaging, surface mineralogy, and elemental rock composition. VICI is designed to study Venus' climate history through detailed atmospheric composition measurements not possible on earlier missions. In addition, VICI images the tessera surface during descent enabling detailed topography to be generated. Finally, VICI makes multiple elemental

  5. Economics as if the earth really mattered. Putting balance back on the balance sheet.

    Science.gov (United States)

    Sherman, D

    1991-09-01

    Some of the thinking in the economic realm which affects the relationship between the economy and the environment is discussed. The standard economic model inherently conflicts with the environment. Humans as consumers have their needs met by maximizing production and efficiency in a free market economy, where an invisible hand guides to profit. The question is raised as to what the environmental impact is for economic growth. The need for clean air, water, and preservation of other living things is not met. It is argued that pollution is a necessary byproduct of production. Economic progress as measured by gross national product (GNP) cannot account for the degradation of nature, e.g., the Alaskan oil spill actually increased GNP. Traditional economics also tell little about the maldistribution of wealth. It is pointed out that Americans spend $5 billion a year on special diets while 400 million around the world are undernourished. Limits to natural resources are also not accounted for by economic theorists, or the value of the seemingly free life-sustaining services performed by a forest in purifying air, preventing erosion and flooding, regulating climate, and supporting biological diversity. It is pointed out that restructuring must occur if the capacity of the Earth to support life is classed in economic terms as an externality. Steady state economic models consider the cycles of production and consumption in the context of the surrounding ecosystem of waste and raw materials and try to achieve a state of equilibrium. Despite the 1972 President's Commission on Population Growth and the American Future's statement that population growth is not necessary for a vital economy, the mythology exists that the economy will collapse, personal income will drop, and business will decline without an ever-growing population. A summary on positive outcomes of zero population growth is given. The economist Julian Simon promotes the view that there is no environmental

  6. A Cubesat Mission to Venus: A Low-Cost Approach to the Investigation of Venus Lightning

    Science.gov (United States)

    Majid, W.; Duncan, C.; Kuiper, T.; Russell, C. T.; Hart, R. A.; Lightsey, E.

    2013-12-01

    The occurrence of Venus lightning has been detected by atmospheric probes and landers on Venus; by ionospheric satellites; by an orbiting visible spectrometer; at radio frequencies by the Galileo spacecraft while flying by Venus; and by an Earth-based telescope. However, none of these detectors has enabled us to determine the global occurrence rate of lightning in the atmosphere of Venus, nor the altitude at which this lightning is generated. Such measurements are needed in order to determine the processes that generate Venus lightning and to establish the importance of Venus lightning in controlling the chemical composition of the Venus atmosphere. A simple and affordable mission to perform this mapping could be achieved with CubeSat technology. A mother spacecraft with at least three CubeSat partners using RF detection could map the occurrence of lightning globally and determine its altitude of origin, with triangulation of precisely timed RF event arrivals. Such a mission would provide space for complementary investigations and be affordable under the Discovery mission program. We are embarking on a program to develop CubeSat-based instrumentation for such a mission. The initial task is to develop a lightning detector in a CubeSat development kit using a software defined radio (SDR) operating at decameter wavelengths (5-50 MHz). This involves algorithm development as well as selecting or developing radio hardware for a CubeSat. Two units will be tested on the ground in a lightning zone such as New Mexico, where the Long Wavelength Array operates in the same frequency range. When the concept has been proven, flight subsystems such as solar panels, attitude sensing and communication radios will be added to the CubeSats to test performance in low Earth orbit. Experience gained from flight would enable a cluster of sensors to be proposed for a future Venus mission.

  7. Venus - Ishtar gravity anomaly

    Science.gov (United States)

    Sjogren, W. L.; Bills, B. G.; Mottinger, N. A.

    1984-01-01

    The gravity anomaly associated with Ishtar Terra on Venus is characterized, comparing line-of-sight acceleration profiles derived by differentiating Pioneer Venus Orbiter Doppler residual profiles with an Airy-compensated topographic model. The results are presented in graphs and maps, confirming the preliminary findings of Phillips et al. (1979). The isostatic compensation depth is found to be 150 + or - 30 km.

  8. 10. The surface and interior of venus

    Science.gov (United States)

    Masursky, H.; Kaula, W.M.; McGill, G.E.; Pettengill, G.H.; Phillips, R.J.; Russell, C.T.; Schubert, G.; Shapiro, I.I.

    1977-01-01

    Present ideas about the surface and interior of Venus are based on data obtained from (1) Earth-based radio and radar: temperature, rotation, shape, and topography; (2) fly-by and orbiting spacecraft: gravity and magnetic fields; and (3) landers: winds, local structure, gamma radiation. Surface features, including large basins, crater-like depressions, and a linear valley, have been recognized from recent ground-based radar images. Pictures of the surface acquired by the USSR's Venera 9 and 10 show abundant boulders and apparent wind erosion. On the Pioneer Venus 1978 Orbiter mission, the radar mapper experiment will determine surface heights, dielectric constant values and small-scale slope values along the sub-orbital track between 50??S and 75??N. This experiment will also estimate the global shape and provide coarse radar images (40-80 km identification resolution) of part of the surface. Gravity data will be obtained by radio tracking. Maps combining radar altimetry with spacecraft and ground-based images will be made. A fluxgate magnetometer will measure the magnetic fields around Venus. The radar and gravity data will provide clues to the level of crustal differentiation and tectonic activity. The magnetometer will determine the field variations accurately. Data from the combined experiments may constrain the dynamo mechanism; if so, a deeper understanding of both Venus and Earth will be gained. ?? 1977 D. Reidel Publishing Company.

  9. Transit of Venus: Quantitative Observing with Simple Equipment The ...

    Indian Academy of Sciences (India)

    a graph sheet and counting the millimeter squares. Better analysis becomes possible, of course, through the usage of software like. MATLAB or any other software that would allow processing the images of the Sun to determine the fractional area of the sunspot. (or Venus or Mercury during transit) occupied on the projected.

  10. Venus 2000 Mission Design

    Science.gov (United States)

    Folta, David; Marr, Greg; Vaughn, Frank; Houghton, Martin B.

    1997-01-01

    As part of the Discovery Program, National Aeronautics and Space Administration (NASA) has solicited proposals for inter-planetary research to conduct solar system exploration science investigations. A mission, called Venus 2000 (V2k), has been proposed for exploration of the Venus Atmosphere. This is NASAs first voyage to Venus to investigate key science objectives since Magellan and will be launched in summer 2002. In keeping with discovery program requirements to reduce total mission cost and utilize new technology, V2k mission design and control will focus on the use of innovative and proven trajectory analysis programs and control systems provided by the Goddard Space Flight Center (GSFC).

  11. Venus Crater Database

    Data.gov (United States)

    National Aeronautics and Space Administration — This web page leads to a database of images and information about the 900 or so impact craters on the surface of Venus by diameter, latitude, and name.

  12. Venus Landsailing Rover

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA Glenn has developed electronics and low-power photovoltaics that will continue to function even at the Venus temperature of 450°C. So the fundamental elements...

  13. Probing the Interior Structure of Venus

    OpenAIRE

    Stevenson, David J.; Cutts, James A.; Mimoun, David; Arrowsmith, Stephen; Banerdt, W. Bruce; Blom, Philip; Brageot, Emily; Brissaud, Quentin; Chin, Gordon; Gao, Peter; Garcia, Raphael; Hall, Jeffrey L.; Hunter, Gary; Jackson, Jennifer M.; Kerzhanovich, V. V.

    2015-01-01

    The formation, evolution, and structure of Venus remain a mystery more than 50 years after the first visit by a robotic spacecraft. Radar images have revealed a surface that is much younger than those of the Moon, Mercury, and Mars as well as a variety of enigmatic volcanic and tectonic features quite unlike those we are familiar with on Earth. What are the dynamic processes that shape these features, in the absence of any plate tectonics? What is their relationship with the de...

  14. Venus Elongation Measurements for the Transit of Venus, using the ...

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 9; Issue 11. Venus Elongation Measurements for the Transit of Venus, using the Historical Jantar Mantar Observatory. N Rathnasree. Classroom Volume 9 Issue 11 November 2004 pp 46-55 ...

  15. Solar Airplane Concept Developed for Venus Exploration

    Science.gov (United States)

    Landis, Geoffrey A.

    2004-01-01

    An airplane is the ideal vehicle for gathering atmospheric data over a wide range of locations and altitudes, while having the freedom to maneuver to regions of scientific interest. Solar energy is available in abundance on Venus. Venus has an exoatmospheric solar flux of 2600 W/m2, compared with Earth's 1370 W/m2. The solar intensity is 20 to 50 percent of the exoatmospheric intensity at the bottom of the cloud layer, and it increases to nearly 95 percent of the exoatmospheric intensity at 65 km. At these altitudes, the temperature of the atmosphere is moderate, in the range of 0 to 100 degrees Celsius, depending on the altitude. A Venus exploration aircraft, sized to fit in a small aeroshell for a "Discovery" class scientific mission, has been designed and analyzed at the NASA Glenn Research Center. For an exploratory aircraft to remain continually illuminated by sunlight, it would have to be capable of sustained flight at or above the wind speed, about 95 m/sec at the cloud-top level. The analysis concluded that, at typical flight altitudes above the cloud layer (65 to 75 km above the surface), a small aircraft powered by solar energy could fly continuously in the atmosphere of Venus. At this altitude, the atmospheric pressure is similar to pressure at terrestrial flight altitudes.

  16. Dynamics of the atmosphere. [spacecraft observations of Venus

    Science.gov (United States)

    Elson, L. S.

    1982-01-01

    Observations of and possible explanations for the dynamics of the Venus atmosphere as revelaed by Pioneer Venus and the Venera spacecraft are discussed. An important observation was that the entire atmosphere moves in the same retrograde (westward) direction at average speeds of up to about 110 m/sec, which may be explained by zonal jets arising from interactions of meridional cells, viscosity and solar heating. Atmospheric thermal tides, temperature and wind perturbations caused by solar heating were also observed which may have influences on tidal winds and warming at the poles. In addition, atmospheric waves with periods of 5.3 and 2.9 earth days have been detected between the Venus cloud tops, and calculations of baroclinically unstable waves on Venus have been made with a general circulation model.

  17. Venus Altitude Cycling Balloon Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The ISTAR Group ( IG) and team mate Thin Red Line Aerospace (TRLA) propose a Venus altitude cycling balloon (Venus ACB), an innovative superpressure balloon...

  18. Lessons Learned from Radiative Transfer Simulations of the Venus Atmosphere

    Science.gov (United States)

    Arney, G.; Meadows, V. S.; Lincowski, A.

    2017-01-01

    The Venus atmosphere is extremely complex, and because of this the spectrum of Earths sister planet is likewise intricate and a challenge to model accurately. However, accurate modeling of Venus spectrum opens up multiple opportunities to better understand the planet next door, and even for understanding Venus-like planets beyond our solar system. Near-infrared (1-2.5 um, NIR) spectral windows observable on the Venus nigthside present the opportunity to probe beneath the Venusian cloud deck and measure thermal emission from the surface and lower atmosphere remotely from Earth or from orbit. These nigthside spectral windows were discovered by Allen and Crawford (1984) and have since been used measure trace gas abundances in the Venus lower atmosphere (less than 45 km), map surface emissivity varisions, and measure properties of the lower cloud deck. These windows sample radiation from below the cloud base at roughly 45 km, and pressures in this region range from roughly Earthlike (approx. 1 bar) up to 90 bars at the surface. Temperatures in this region are high: they range from about 400 K at the base of the cloud deck up to about 740 K at the surface. This high temperature and pressure presents several challenges to modelers attempting radiative transfer simulations of this region of the atmosphere, which we will review. Venus is also important to spectrally model to predict the remote observables of Venus-like exoplanets in anticipation of data from future observatories. Venus-like planets are likely one of the most common types of terrestrial planets and so simulations of them are valuable for planning observatory and detector properties of future telescopes being designed, as well as predicting the types of observations required to characterize them.

  19. Venus transit 2004: An international education program

    Science.gov (United States)

    Mayo, L.; Odenwald, S.

    2003-04-01

    December 6th, 1882 was the last transit of the planet Venus across the disk of the sun. It was heralded as an event of immense interest and importance to the astronomical community as well as the public at large. There have been only six such occurrences since Galileo first trained his telescope on the heavens in 1609 and on Venus in 1610 where he concluded that Venus had phases like the moon and appeared to get larger and smaller over time. Many historians consider this the final nail in the coffin of the Ptolemaic, Earth centered solar system. In addition, each transit has provided unique opportunities for discovery such as measurement and refinement of the detection of Venus' atmosphere, calculation of longitudes, and calculation of the astronomical unit (and therefore the scale of the solar system). The NASA Sun Earth Connection Education Forum (SECEF) in partnership with the Solar System Exploration (SSE) and Structure and Evolution of the Universe (SEU) Forums, AAS Division for Planetary Sciences (DPS), and a number of NASA space missions and science centers are developing plans for an international education program centered around the June 8, 2004 Venus transit. The transit will be visible in its entirety from Europe and partially from the East Coast of the United States. We will use a series of robotic observatories including the Telescopes In Education (TIE) network distributed in latitude to provide observations of the transit that will allow middle and high school students to calculate the A.U. through application of parallax. We will compare the terrestrial planets in terms of the evolutionary processes that define their magnetic fields, their widely differing interactions with the solar wind, and the implications this has for life on Earth and elsewhere in the universe. We will also use Venus transit as a probe of episodes in American history (e.g. 1769: revolutionary era, 1882: post civil war era, and 2004: modern era). Museums and planetariums in

  20. Geology of Maxwell Montes, Venus

    Science.gov (United States)

    Head, J. W.; Campbell, D. B.; Peterfreund, A. R.; Zisk, S. A.

    1984-01-01

    Maxwell Montes represent the most distinctive topography on the surface of Venus, rising some 11 km above mean planetary radius. The multiple data sets of the Pioneer missing and Earth based radar observations to characterize Maxwell Montes are analyzed. Maxwell Montes is a porkchop shaped feature located at the eastern end of Lakshmi Planum. The main massif trends about North 20 deg West for approximately 1000 km and the narrow handle extends several hundred km West South-West WSW from the north end of the main massif, descending down toward Lakshmi Planum. The main massif is rectilinear and approximately 500 km wide. The southern and northern edges of Maxwell Montes coincide with major topographic boundaries defining the edge of Ishtar Terra.

  1. The Planet Venus

    Science.gov (United States)

    Luhmann, Janet

    This book is not so much for the space scientist looking for background material for research as it is for one interested in the history of planetary exploration. The first half (˜100 pps) is devoted to studies of Venus before the space age, starting at several hundred years BC. It is obvious from the multitude of detailed descriptions of observers' accounts that considerable library research went into this section. While sometimes tedious, this chronology of Venus research is punctuated with amusing facts. While many may know about the Velikovsky theory of the cometary origin of the planet, few may know that Lowell drew pictures of Cytherian canals similar to the canals of Mars or that Frederick the Great of Prussia proposed to name the (once suspected) satellite of Venus D'Alembert, after the mathematician. An equally amusing appendix shows the ups and downs of the rotation period of this planet with the invisible surface. Much attention is focused on early telescope observations, the ashen light, and transits of Venus. At the end of this half, one appreciates that Venus has played a fairly important role in history in the areas of religion, science, and technology.

  2. Solar Wind Interaction and Impact on the Venus Atmosphere

    Science.gov (United States)

    Futaana, Yoshifumi; Stenberg Wieser, Gabriella; Barabash, Stas; Luhmann, Janet G.

    2017-11-01

    Venus has intrigued planetary scientists for decades because of its huge contrasts to Earth, in spite of its nickname of "Earth's Twin". Its invisible upper atmosphere and space environment are also part of the larger story of Venus and its evolution. In 60s to 70s, several missions (Venera and Mariner series) explored Venus-solar wind interaction regions. They identified the basic structure of the near-Venus space environment, for example, existence of the bow shock, magnetotail, ionosphere, as well as the lack of the intrinsic magnetic field. A huge leap in knowledge about the solar wind interaction with Venus was made possible by the 14-year long mission, Pioneer Venus Orbiter (PVO), launched in 1978. More recently, ESA's probe, Venus Express (VEX), was inserted into orbit in 2006, operated for 8 years. Owing to its different orbit from that of PVO, VEX made unique measurements in the polar and terminator regions, and probed the near-Venus tail for the first time. The near-tail hosts dynamic processes that lead to plasma energization. These processes in turn lead to the loss of ionospheric ions to space, slowly eroding the Venusian atmosphere. VEX carried an ion spectrometer with a moderate mass-separation capability and the observed ratio of the escaping hydrogen and oxygen ions in the wake indicates the stoichiometric loss of water from Venus. The structure and dynamics of the induced magnetosphere depends on the prevailing solar wind conditions. VEX studied the response of the magnetospheric system on different time scales. A plethora of waves was identified by the magnetometer on VEX; some of them were not previously observed by PVO. Proton cyclotron waves were seen far upstream of the bow shock, mirror mode waves were observed in magnetosheath and whistler mode waves, possibly generated by lightning discharges were frequently seen. VEX also encouraged renewed numerical modeling efforts, including fluid-type of models and particle-fluid hybrid type of models

  3. Ice sheet in peril

    DEFF Research Database (Denmark)

    Hvidberg, Christine Schøtt

    2016-01-01

    Earth's large ice sheets in Greenland and Antarctica are major contributors to sea level change. At present, the Greenland Ice Sheet (see the photo) is losing mass in response to climate warming in Greenland (1), but the present changes also include a long-term response to past climate transitions...

  4. Entry at Venus

    Science.gov (United States)

    Venkatapathy, Ethiraj; Smith, Brandon

    2016-01-01

    This is lecture to be given at the IPPW 2016, as part of the 2 day course on Short Course on Destination Venus: Science, Technology and Mission Architectures. The attached presentation material is intended to be introduction to entry aspects of Venus in-situ robotic missions. The presentation introduces the audience to the aerodynamic and aerothermodynamic aspects as well as the loads, both aero and thermal, generated during entry. The course touches upon the system design aspects such as TPS design and both high and low ballistic coefficient entry system concepts that allow the science payload to be protected from the extreme entry environment and yet meet the mission objectives.

  5. Muon Excess at Sea Level during the Progress of a Geomagnetic Storm and High-Speed Stream Impact Near the Time of Earth's Heliospheric Sheet Crossing

    Science.gov (United States)

    Augusto, C. R. A.; Navia, C. E.; de Oliveira, M. N.; Nepomuceno, A. A.; Kopenkin, V.; Sinzi, T.

    2017-08-01

    In this article we present results of studying the association between the muon flux variation at ground level, registered by the New-Tupi muon telescopes (22° 53'00'' S, 43° 06'13' W; 3 m above sea level), and the geomagnetic storm on 25 - 29 August 2015 that has raged for several days as a result of a coronal mass ejection (CME) impact on Earth's magnetosphere. A sequence of events started with an M3.5 X-ray class flare on 22 August 2015 at 21:19 UTC. The New-Tupi muon telescopes observed a Forbush decrease (FD) triggered by this geomagnetic storm, which began on 26 August 2015. After Earth crossed the heliospheric current sheet (HCS), an increase in particle flux was observed on 28 August 2015 by spacecraft and ground-level detectors. The observed peak was in temporal coincidence with the impact of a high-speed stream (HSS). We study this increase, which has been observed with a significance above 1.5% by ground-level detectors in different rigidity regimes. We also estimate the lower limit of the energy fluence injected on Earth. In addition, we consider the origin of this increase, such as acceleration of particles by shock waves at the front of the HSS and the focusing effect of the HCS crossing. Our results show possible evidence of a prolonged energetic (up to GeV energies) particle injection within the Earth atmosphere system, driven by the HSS. In most cases, these injected particles are directed to the polar regions. However, the particles from the high-energy tail of the spectrum can reach mid-latitudes, and this could have consequences for the atmospheric chemistry. For instance, the creation of NOx species may be enhanced, and this can lead to increased ozone depletion. This topic requires further study.

  6. Sampling the Cloudtop Region on Venus

    Science.gov (United States)

    Limaye, Sanjay; Ashish, Kumar; Alam, Mofeez; Landis, Geoffrey; Widemann, Thomas; Kremic, Tibor

    2014-05-01

    The details of the cloud structure on Venus continue to be elusive. One of the main questions is the nature and identity of the ultraviolet absorber(s). Remote sensing observations from Venus Express have provided much more information about the ubiquitous cloud cover on Venus from both reflected and emitted radiation from Venus Monitoring Camera (VMC) and Visible InfraRed Imaging Spectrometer (VIRTIS) observations. Previously, only the Pioneer Venus Large Probe has measured the size distribution of the cloud particles, and other probes have measured the bulk optical properties of the cloud cover. However, the direct sampling of the clouds has been possible only below about 62 km, whereas the recent Venus Express observations indicate that the cloud tops extend from about 75 km in equatorial region to about 67 km in polar regions. To sample the cloud top region of Venus, other platforms are required. An unmanned aerial vehicle (UAV) has been proposed previously (Landis et al., 2002). Another that is being looked into, is a semi-buoyant aerial vehicle that can be powered using solar cells and equipped with instruments to not only sample the cloud particles, but also to make key atmospheric measurements - e.g. atmospheric composition including isotopic abundances of noble and other gases, winds and turbulence, deposition of solar and infrared radiation, electrical activity. The conceptual design of such a vehicle can carry a much more massive payload than any other platform, and can be controlled to sample different altitudes and day and night hemispheres. Thus, detailed observations of the surface using a miniature Synthetic Aperture Radar are possible. Data relay to Earth will need an orbiter, preferably in a low inclination orbit, depending on the latitude region selected for emphasis. Since the vehicle has a large surface area, thermal loads on entry are low, enabling deployment without the use of an aeroshell. Flight characteristics of such a vehicle have been

  7. SAEVe: A Long Duration Small Sat Class Venus Lander - Seismic and Atmospheric Exploration of Venus

    Science.gov (United States)

    Kremic, Tibor; Ghail, Richard; Gilmore, Martha; Hunter, Gary; Kiefer, Walter; Limaye, Sanjay; Pauken, Michael; Tolbert, Carol; Wilson, Colin

    2017-01-01

    NASA's science mission directorate has put increasing emphasis on innovative, smaller, and lower cost missions to achieve their science objectives. One example of this was the recent call by the Planetary Science Division for cube and small satellite concepts expected to cost $100M or less, not including launch and weighing less than 180kg. Over 100 proposals were submitted suggesting that indeed this is a size of mission worthy of being considered in future planning. Nineteen missions were selected for study, one being a long-lived Venus mission called SAEVe, for Seismic and Atmospheric Exploration of Venus. The science objectives and relevance of SAEVe include: Is Venus seismically active? What can we learn about its crust (thickness and composition) and its interior (lithosphere, mantle, and core)? What can be learned about its evolutionary history or about the planet / atmosphere interactions? SAEVe begins to address these science questions with simple, but capable, instrumented probes that can survive on the surface of Venus and take temporal measurements over months something never attempted before. The data returned will further our understanding of the solar system and Earth, and aid in meeting the NASA Science Plan goal to ascertain the content, origin, and evolution of the solar system and the chemical and physical processes in our solar system. SAEVe is delivered to Venus as a ride-along on another mission to Venus. Its two small probes are placed into the Venus atmosphere via a single Stardust-like entry capsule, are ejected at different times, free fall, and decelerate in the thickening atmosphere to touchdown under 8 m/s2 or less. The probes will begin taking measurements and transmitting important parameters at or near the surface and will focus on measurements like seismic activity, heat flux, wind speed and direction, basic chemical abundances, temperature, and pressure. At preset intervals, the probes acquire the science measurements and beam the

  8. Sulfur dioxide - Episodic injection shows evidence for active Venus volcanism

    Science.gov (United States)

    Esposito, L. W.

    1984-03-01

    Pioneer Venus ultraviolet spectra from the first 5 years of operation show a decline (by more than a factor of 10) in sulfur dioxide abundance at the cloud tops and in the amount of submicron haze above the clouds. At the time of the Pioneer Venus encounter, the values for both parameters greatly exceeded earlier upper limits. However, Venus had a similar appearance in the late 1950's, implying the episodic injection of sulfur dioxide possibly caused by episodic volcanism. The amount of haze in the Venus middle atmosphere is about ten times that found in earth's stratosphere after the most recent major volcanic eruptions, and the thermal energy required for this injection on Venus is greater by about an order of magnitude than the largest of these recent earth eruptions and about as large as the Krakatoa eruption of 1883. The episodic behavior of sulfur dioxide implies that steady-state models of the chemistry and dynamics of cloud-top regions may be of limited use.

  9. Sulfur dioxide: episodic injection shows evidence for active venus volcanism.

    Science.gov (United States)

    Esposito, L W

    1984-03-09

    Pioneer Venus ultraviolet spectra from the first 5 years of operation show a decline (by more than a factor of 10) in sulfur dioxide abundance at the cloud tops and in the amount of submicron haze above the clouds. At the time of the Pioneer Venus encounter, the values for both parameters greatly exceeded earlier upper limits. However, Venus had a similar appearance in the late 1950's, implying the episodic injection of sulfur dioxide possibly caused by episodic volcanism. The amount of haze in the Venus middle atmosphere is about ten times that found in Earth's stratosphere after the most recent major volcanic eruptions, and the thermal energy required for this injection on Venus is greater by about an order of magnitude than the largest of these recent Earth eruptions and about as large as the Krakatoa eruption of 1883. The episodic behavior of sulfur dioxide implies that steady-state models of the chemistry and dynamics of cloud-top regions may be of limited use.

  10. Venus: The First Habitable World of Our Solar System?

    Science.gov (United States)

    Way, Michael Joseph; Del Genio, Anthony; Kiang, Nancy; Sohl, Linda; Clune, Tom; Aleinov, Igor; Kelley, Maxwell

    2015-01-01

    A great deal of effort in the search for life off-Earth in the past 20+ years has focused on Mars via a plethora of space and ground based missions. While there is good evidence that surface liquid water existed on Mars in substantial quantities, it is not clear how long such water existed. Most studies point to this water existing billions of years ago. However,those familiar with the Faint Young Sun hypothesis for Earth will quickly realize that this problem is even more pronounced for Mars. In this context recent simulations have been completed with the GISS 3-D GCM (1) of paleo Venus (approx. 3 billion years ago) when the sun was approx. 25 less luminous than today. A combination of a less luminous Sun and a slow rotation rate reveal that Venus could have had conditions on its surface amenable to surface liquid water. Previous work has also provided bounds on how much water Venus could have had using measured DH ratios. It is possible that less assumptions have to be made to make Venus an early habitable world than have to be made for Mars, even thoughVenus is a much tougher world on which to confirm this hypothesis.

  11. Earth

    CERN Document Server

    Carter, Jason

    2017-01-01

    This curriculum-based, easy-to-follow book teaches young readers about Earth as one of the eight planets in our solar system in astronomical terms. With accessible text, it provides the fundamental information any student needs to begin their studies in astronomy, such as how Earth spins and revolves around the Sun, why it's uniquely suitable for life, its physical features, atmosphere, biosphere, moon, its past, future, and more. To enhance the learning experience, many of the images come directly from NASA. This straightforward title offers the fundamental information any student needs to sp

  12. The transit of Venus enterprise in Victorian Britain

    CERN Document Server

    Ratcliff, Jessica

    2008-01-01

    In nineteenth century, the British Government spent money measuring the distance between the earth and the sun using observations of the transit of Venus. This book presents a narrative of the two Victorian transit programmes. It draws out their cultural significance and explores the nature of 'big science' in late-Victorian Britain.

  13. Quasi-adiabatic particle acceleration in a magnetic field reversals and the formation of the plasma sheet boundary layer in the earth's magnetotail

    International Nuclear Information System (INIS)

    Zelenyi, L.M.; Vogin, D.V.; Buechner, J.

    1989-01-01

    Two types of regularity exist for the particle motion in the two-dimensional magnetic field reversals (MFR) with the strongly curves magnetic field lines - the usual adiabatic and another one which we called 'quasiadiabatic'. Here we consider the acceleration of MFR particles in stationary and homogeneous electric field induced by the motion of MFR through the ambient plasma (i.e. solar wind). Assuming that the time scale of acceleration is slow in comparison with the period of orbital motion we introduce the new longitudinal invariant I κ . This enables to describe the process of acceleration in a closed form and to obtain for the first time the laws governing the quasiadiabatic ion acceleration in the Earth's mangetotail. The similarities and differences in adiabatic and quasiadiabatic acceleration mechanisms are discussed. The obtained results give and important insights to the problem of the particle heating in hte Earth's magnetotail and to the formation of accelerated plasma streams along the edges of the plasma sheet. (author). 17 refs.; 7 figs

  14. An Exo-Venus in the Solar Neighborhood

    Science.gov (United States)

    Kohler, Susanna

    2017-04-01

    A size comparison of Venus and Earth. Though they are nearly the same size and density, these two planets evolved very differently. [NASA]Earth is great place for life but Venus definitely isnt. Both planets have similar masses and densities. So why did one evolve to support life, while the other turned into a barren and inhospitable hothouse? This is a question we might be able to answer if we can gather observations of other planets similar to Earth and Venus. The recent discovery of an exo-Venus in our solar neighborhood brings us one step closer to thisgoal!A New NeighborA team of scientists led by Isabel Angelo (SETI Institute, NASA Ames Research Center, and UC Berkeley) has announced the discovery of Kepler-1649b, an exoplanet transiting a star located just 219 light-years away from us. Kepler-1649b is unique in being roughly the same size as Earth and Venus and also receiving a similar amount of starlight as Venus does from our Sun.Phase-folded light curve showing the transit of Kepler-1649b. [Angelo et al. 2017]Angelo and collaborators conducted follow-up observations after Keplers detection of 1649b to verify its planetary nature and pin down its properties. They found that Kepler-1649b has a radius of 1.08 times that of Earth, and it receives an incident flux of 2.3 times Earths which is very similar to the incident flux received by Venus. Kepler-1649b orbits a star thats only a quarter of our Suns radius, however, and it therefore orbits significantly closer to its star in order to receive the same flux, circling its host once every 8.7 days.Differences Due to a Small HostIts worth identifying howthis planet might differ from Venus. The authors suggest a few key factors:Kepler-1649b may be more prone to effects of host-star variability. M-dwarf stars like this one are typically more magnetically active than our Sun, and Kepler-1649b is orbiting very close to its star.Kepler-1649b receives comparatively low-energy radiation, compared to Venus. This is

  15. Terrestrial subaqueous seafloor dunes: Possible analogs for Venus

    Science.gov (United States)

    Neakrase, Lynn D. V.; Klose, Martina; Titus, Timothy N.

    2017-06-01

    Dunes on Venus, first discovered with Magellan Synthetic Aperture Radar (SAR) in the early 1990s, have fueled discussions about the viability of Venusian dunes and aeolian grain transport. Confined to two locations on Venus, the existence of the interpreted dunes provides evidence that there could be transportable material being mobilized into aeolian bedforms at the surface. However, because of the high-pressure high-temperature surface conditions, laboratory analog studies are difficult to conduct and results are difficult to extrapolate to full-sized, aeolian bedforms. Field sites of desert dunes, which are well-studied on Earth and Mars, are not analogous to what is observed on Venus because of the differences in the fluid environments. One potentially underexplored possibility in planetary science for Venus-analog dune fields could be subaqueous, seafloor dune fields on Earth. Known to the marine geology communities since the early 1960s, seafloor dunes are rarely cited in planetary aeolian bedform literature, but could provide a necessary thick-atmosphere extension to the classically studied aeolian dune environment literature for thinner atmospheres. Through discussion of the similarity of the two environments, and examples of dunes and ripples cited in marine literature, we provide evidence that subaqueous seafloor dunes could serve as analogs for dunes on Venus. Furthermore, the evidence presented here demonstrates the usefulness of the marine literature for thick-atmosphere planetary environments and potentially for upcoming habitable worlds and oceanic environment research program opportunities. Such useful cross-disciplinary discussion of dune environments is applicable to many planetary environments (Earth, Mars, Venus, Titan, etc.) and potential future missions.

  16. Global Geological Map of Venus

    Science.gov (United States)

    Ivanov, M. A.

    2008-09-01

    Introduction: The Magellan SAR images provide sufficient data to compile a geological map of nearly the entire surface of Venus. Such a global and selfconsistent map serves as the base to address the key questions of the geologic history of Venus. 1) What is the spectrum of units and structures that makes up the surface of Venus [1-3]? 2) What volcanic/tectonic processes do they characterize [4-7]? 3) Did these processes operated locally, regionally, or globally [8- 11]? 4) What are the relationships of relative time among the units [8]? 5) At which length-scale these relationships appear to be consistent [8-10]? 6) What is the absolute timing of formation of the units [12-14]? 7) What are the histories of volcanism, tectonics and the long-wavelength topography on Venus? 7) What model(s) of heat loss and lithospheric evolution [15-21] do these histories correspond to? The ongoing USGS program of Venus mapping has already resulted in a series of published maps at the scale 1:5M [e.g. 22-30]. These maps have a patch-like distribution, however, and are compiled by authors with different mapping philosophy. This situation not always results in perfect agreement between the neighboring areas and, thus, does not permit testing geological hypotheses that could be addressed with a self-consistent map. Here the results of global geological mapping of Venus at the scale 1:10M is presented. The map represents a contiguous area extending from 82.5oN to 82.5oS and comprises ~99% of the planet. Mapping procedure: The map was compiled on C2- MIDR sheets, the resolution of which permits identifying the basic characteristics of previously defined units. The higher resolution images were used during the mapping to clarify geologic relationships. When the map was completed, its quality was checked using published USGS maps [e.g., 22-30] and the catalogue of impact craters [31]. The results suggest that the mapping on the C2-base provided a highquality map product. Units and

  17. Short Large-Amplitude Magnetic Structures (SLAMS) at Venus

    Science.gov (United States)

    Collinson, G. A.; Wilson, L. B.; Sibeck, D. G.; Shane, N.; Zhang, T. L.; Moore, T. E.; Coates, A. J.; Barabash, S.

    2012-01-01

    We present the first observation of magnetic fluctuations consistent with Short Large-Amplitude Magnetic Structures (SLAMS) in the foreshock of the planet Venus. Three monolithic magnetic field spikes were observed by the Venus Express on the 11th of April 2009. The structures were approx.1.5->11s in duration, had magnetic compression ratios between approx.3->6, and exhibited elliptical polarization. These characteristics are consistent with the SLAMS observed at Earth, Jupiter, and Comet Giacobini-Zinner, and thus we hypothesize that it is possible SLAMS may be found at any celestial body with a foreshock.

  18. Disposal of radioactive waste in space towards Venus

    International Nuclear Information System (INIS)

    Anon.

    1980-01-01

    A review is given of an artical in Astronautics and Aeronautics by C. Priest, R. Nixon and E. Rice describing a NASA funded research project on the possible storage of highly radioactive waste in an orbit round the sun between earth and Venus. Minimum distance from earth is expected to be 22.5 million kilometers and it is suggested that storage should be secure for a million years. (G.M.E.)

  19. Venus gravity fields

    Science.gov (United States)

    Sjogren, W. L.; Ananda, M.; Williams, B. G.; Birkeland, P. W.; Esposito, P. S.; Wimberly, R. N.; Ritke, S. J.

    1981-01-01

    Results of Pioneer Venus Orbiter observations concerning the gravity field of Venus are presented. The gravitational data was obtained from reductions of Doppler radio tracking data for the Orbiter, which is in a highly eccentric orbit with periapsis altitude varying from 145 to 180 km and nearly fixed periapsis latitude of 15 deg N. The global gravity field was obtained through the simultaneous estimation of the orbit state parameters and gravity coefficients from long-period variations in orbital element rates. The global field has been described with sixth degree and order spherical harmonic coefficients, which are capable of resolving the three major topographical features on Venus. Local anomalies have been mapped using line-of-sight accelerations derived from the Doppler residuals between 40 deg N and 10 deg S latitude at approximately 300 km spatial resolution. Gravitational data is observed to correspond to topographical data obtained by radar altimeter, with most of the gravitational anomalies about 20-30 milligals. Simulations evaluating the isostatic states of two topographic features indicate that at least partial isostasy prevails, with the possibility of complete compensation.

  20. Technology perspectives in the future exploration of Venus

    Science.gov (United States)

    Cutts, James A.; Balint, Tibor S.; Chassefiere, Eric; Kolawa, Elizabeth A.

    Science goals to understand the origin, history and environment of Venus have been driving international space exploration missions for over 40 years. Today, Venus is still identified as a high priority science target in NASA's Solar System Exploration Roadmap, and clearly fits scientific objectives of ESA's Cosmic Vision Program in addition to the ongoing Venus Express mission, while JAXA is planning to launch its own Venus Climate Orbiter. Technology readiness has often been the pivotal factor in mission prioritization. Missions in all classes—small, medium or large—could be designed as orbiters with remote sensing capabilities, however, the desire for scientific advancements beyond our current knowledge point to in-situ exploration of Venus at the surface and lower atmosphere, involving probes, landers, and aerial platforms. High altitude balloons could circumnavigate Venus repeatedly; deep probes could operate for extended periods utilizing thermal protection technologies, pressure vessel designs and advancements in high temperature electronics. In situ missions lasting for over an Earth day could employ a specially designed dynamic Stirling Radioisotope Generator (SRG) power system, that could provide both electric power and active thermal control to the spacecraft. An air mobility platform, possibly employing metallic bellows, could allow for all axis control, long traversing and surface access at multiple desired locations, thus providing an advantage over static lander or rover based architectures. Sample return missions are also featured in all planetary roadmaps. The Venus exploration plans over the next three decades are anticipated to greatly contribute to our understanding of this planet, which subsequently would advance our overall knowledge about Solar System history and habitability.

  1. Nimbus-3 Medium-Resolution Infrared Radiometer (MRIR) Imagery of the Earth and Atmosphere at Daytime on 4" x 5" Film Sheets V001

    Data.gov (United States)

    National Aeronautics and Space Administration — The MRIRN3IM data product consists of 4 x 5 inch photographic film sheets from the Nimbus-3 Medium Resolution Infrared Radiometer. Each film sheet contains an entire...

  2. Nimbus-2 Medium-Resolution Infrared Radiometer (MRIR) Imagery of the Earth and Atmosphere at Daytime on 4" x 5" Film Sheets V001

    Data.gov (United States)

    National Aeronautics and Space Administration — The MRIRN2IM data product consists of 4 x 5 inch photographic film sheets from the Nimbus-2 Medium Resolution Infrared Radiometer. Each film sheet contains an entire...

  3. Reorientation Histories of Mercury, Venus, the Moon, and Mars

    Science.gov (United States)

    Keane, J. T.; Matsuyama, I.

    2017-09-01

    The spins of planets are not constant with time. Impacts, volcanos, and other large geologic features can reorient planets (a process known as true polar wander). True polar wander can have important implications for the climate, volatiles, and tectonics of planets and moons. However, despite its importance, it has been difficult to study true polar wander for objects beyond the Earth. Here we present the results of the first comprehensive, data-driven investigation into the true polar wander histories of Mercury, Venus, the Moon, and Mars. We find that Mercury and the Moon have both reoriented in response to large impacts, while the spins of Mars and Venus are more strongly affected by volcanism. Venus, in particular, has been subject to some very dramatic episodes of true polar wander in the past.

  4. On the Geological History of Venus

    Science.gov (United States)

    Basilevsky, A. T.; Head, J. W.

    2008-09-01

    of passing of meteoroids through the dense Venus atmosphere, and 3) cratering under the high atmospheric pressure. As a result of these uncertainties, even statistically reliable estimates of the mean surface age of Venus are not very certain: ~750 m.y., but any values between 300 m.y. and 1 b.y. are considered possible [16]. This is why researchers using crater statistics to estimate absolute ages of individual geologic units use fractions or multiples of the mean surface age of Venus, instead of millions or billions of years, designating it as T [e.g., 14, 15]. The new estimates based on the global geologic mapping of [12] suggest that ages of selected units (in T with 2 σ error bars) are: tt, 1.09 ± 0.17; psh, 1.04 ± 0.18; pwr, 1.05 ± 0.12; pl, 0.54 ± 0.19; rt, 0.63 ± 0.26; confirming a new and more reliable basis for earlier estimates [13-15, 17-24]. This returns us to the conclusion made in [11]: …the earlier suite of units (from heavily deformed tesserae through slightly deformed regional plains) occurred during a time period an order of magnitude shorter than the subsequent period (from the end of emplacement of the wrinkle-ridge network until the present). These results imply high global rates of endogenic (volcanic) activity during the first era (comparable to that of mid-oceanic-ridge volcanism of Earth) and much lower global rates of endogenic activity (by two orders of magnitude) for the second period (page 1015, abstract). Conclusions: As it follows from the above consideration, tectonic and volcanic processes in the beginning of the morphologically recognizable part of the geologic history of Venus (since tessera time) were rather active and resurfaced the entire planet. But then, after about 10-20% of the total duration of this part of history they rather sharply occurred sporadically and in separate spots and zones and affected only 15-20% of the Venus. For better understanding the rates of tectonic and volcanic processes on Venus, knowledge

  5. VERITAS: a Discovery-Class Venus Surface Geology and Geophysics Mission

    Science.gov (United States)

    Freeman, Anthony; Smrekar, Suzanne E.; Hensley, Scott; Wallace, Mark; Sotin, Christophe; Darrach, Murray; Xaypraseuth, Peter; Helbert, Joern; Mazarico, Erwan

    2016-01-01

    Our understanding of solar system evolution is limited by a great unanswered question: How Earthlike is Venus? We know that these "twin" planets formed with similar bulk composition and size. Yet the evolutionary path Venus followed has diverged from Earth's, in losing its surface water and becoming hotter than Mercury. What led to this? The answer has profound implications for how terrestrial planets become habitable and the potential for life in the universe.

  6. Hot climate inhibits volcanism on Venus: Constraints from rock deformation experiments and argon isotope geochemistry

    Science.gov (United States)

    Mikhail, Sami; Heap, Michael J.

    2017-07-01

    The disparate evolution of sibling planets Earth and Venus has left them markedly different. Venus' hot (460 °C) surface is dry and has a hypsometry with a very low standard deviation, whereas Earth's average temperature is 4 °C and the surface is wet and has a pronounced bimodal hypsometry. Counterintuitively, despite the hot Venusian climate, the rate of intraplate volcano formation is an order of magnitude lower than that of Earth. Here we compile and analyse rock deformation and atmospheric argon isotope data to offer an explanation for the relative contrast in volcanic flux between Earth and Venus. By collating high-temperature, high-pressure rock deformation data for basalt, we provide a failure mechanism map to assess the depth of the brittle-ductile transition (BDT). These data suggest that the Venusian BDT likely exists between 2 and 12 km depth (for a range of thermal gradients), in stark contrast to the BDT for Earth, which we find to be at a depth of ∼25-27 km using the same method. The implications for planetary evolution are twofold. First, downflexing and sagging will result in the sinking of high-relief structures, due to the low flexural rigidity of the predominantly ductile Venusian crust, offering an explanation for the curious coronae features on the Venusian surface. Second, magma delivery to the surface-the most efficient mechanism for which is flow along fractures (dykes; i.e., brittle deformation)-will be inhibited on Venus. Instead, we infer that magmas must stall and pond in the ductile Venusian crust. If true, a greater proportion of magmatism on Venus should result in intrusion rather than extrusion, relative to Earth. This predicted lower volcanic flux on Venus, relative to Earth, is supported by atmospheric argon isotope data: we argue here that the anomalously unradiogenic present-day atmospheric 40Ar/36Ar ratio for Venus (compared with Earth) must reflect major differences in 40Ar degassing, primarily driven by volcanism. Indeed

  7. Venus' Spectral Signatures and the Potential for Life in the Clouds.

    Science.gov (United States)

    Limaye, Sanjay S; Mogul, Rakesh; Smith, David J; Ansari, Arif H; Słowik, Grzegorz P; Vaishampayan, Parag

    2018-03-30

    The lower cloud layer of Venus (47.5-50.5 km) is an exceptional target for exploration due to the favorable conditions for microbial life, including moderate temperatures and pressures (∼60°C and 1 atm), and the presence of micron-sized sulfuric acid aerosols. Nearly a century after the ultraviolet (UV) contrasts of Venus' cloud layer were discovered with Earth-based photographs, the substances and mechanisms responsible for the changes in Venus' contrasts and albedo are still unknown. While current models include sulfur dioxide and iron chloride as the UV absorbers, the temporal and spatial changes in contrasts, and albedo, between 330 and 500 nm, remain to be fully explained. Within this context, we present a discussion regarding the potential for microorganisms to survive in Venus' lower clouds and contribute to the observed bulk spectra. In this article, we provide an overview of relevant Venus observations, compare the spectral and physical properties of Venus' clouds to terrestrial biological materials, review the potential for an iron- and sulfur-centered metabolism in the clouds, discuss conceivable mechanisms of transport from the surface toward a more habitable zone in the clouds, and identify spectral and biological experiments that could measure the habitability of Venus' clouds and terrestrial analogues. Together, our lines of reasoning suggest that particles in Venus' lower clouds contain sufficient mass balance to harbor microorganisms, water, and solutes, and potentially sufficient biomass to be detected by optical methods. As such, the comparisons presented in this article warrant further investigations into the prospect of biosignatures in Venus' clouds. Key Words: Venus-Clouds-Life-Habitability-Microorganism-Albedo-Spectroscopy-Biosignatures-Aerosol-Sulfuric Acid. Astrobiology 18, xxx-xxx.

  8. Venusians: the Planet Venus in the 18th-Century Extraterrestrial Life Debate

    Science.gov (United States)

    Duner, David

    2013-05-01

    In the seventeenth and eighteenth centuries it became possible to believe in the existence of life on other planets on scientific grounds. Once the Earth was no longer the center of the universe according to Copernicus, once Galileo had aimed his telescope at the Moon and found it a rough globe with mountains and seas, the assumption of life on other planets became much less far-fetched. In general there were no actual differences between Earth and Venus, since both planets orbited the Sun, were of similar size, and possessed mountains and an atmosphere. If there is life on Earth, one may ponder why it could not also exist on Venus. In the extraterrestrial life debate of the seventeenth and eighteenth centuries, the Moon, our closest celestial body, was the prime candidate for life on other worlds, although a number of scientists and scholars also speculated about life on Venus and on other planets, both within our solar system and beyond its frontiers. This chapter discusses the arguments for life on Venus and those scientific findings that were used to support them, which were based in particular on assumptions and claims that both mountains and an atmosphere had been found on Venus. The transits of Venus in the 1760s became especially important for the notion that life could thrive on Venus. Here, I detect two significant cognitive processes that were at work in the search for life on Venus, i.e., analogical reasoning and epistemic perception, while analogies and interpretations of sensory impressions based on prior knowledge played an important role in astrobiological theories.

  9. Laying bare Venus' dark secrets

    International Nuclear Information System (INIS)

    Allen, D.A.

    1987-01-01

    Ground-based IR observations of the dark side of Venus obtained in 1983 and 1985 with the Anglo-Australian Telescope are studied. An IR spectrum of Venus' dark side is analyzed. It is observed that the Venus atmosphere is composed of CO and radiation escapes only at 1.74 microns and 2.2 to 2.4 microns. The possible origin of the radiation, either due to absorbed sunlight or escaping thermal radiation, was investigated. These two hypotheses were eliminated, and it is proposed that the clouds of Venus are transparent and the radiation originates from the same stratum as the brighter portions but is weakened by the passage through the upper layer. The significance of the observed dark side markings is discussed

  10. Venus Suface Sampling and Analysis

    Data.gov (United States)

    National Aeronautics and Space Administration — This effort is developing the technology to transfer particulate samples from a Venus drill (being developed by Honeybee Robotics in a Phase 2 Small Business...

  11. Venus - Phoebe Region

    Science.gov (United States)

    1990-01-01

    This Magellan radar image is of part of the Phoebe region of Venus. It is a mosaic of parts of revolutions 146 and 147 acquired in the first radar test on Aug. 16, 1990. The area in the image is located at 291 degrees east longitude, 19 degrees south latitude. The image shows an area 30 kilometers (19.6 miles) wide and 76 km (47 miles) long. On the basis of Pioneer Venus and Arecibo data, it is known that two major rift zones occur in southern Phoebe Regio and that they terminate at about 20 to 25 degrees south latitude, about 2,000 km (1,240 miles) apart. This image is of an area just north of the southern end of the western rift zone. The region is characterized by a complex geologic history involving both volcanism and faulting. Several of the geologic units show distinctive overlapping or cross cutting relationships that permit identification and separation of geologic events and construction of the geologic history of the region. The oldest rocks in this image form the complexly deformed and faulted, radar bright, hilly terrain in the northern half. Faults of a variety of orientations are observed. A narrow fault trough (about one-half to one km (three tenths to six tenths of a mile) wide is seen crossing the bright hills near the lower part in the middle of the image. This is one of the youngest faults in the faulted, hilly unit as it is seen to cut across many other structures. The fault trough in turn appears to be embayed and flooded by the darker plains that appear in the south half of the image. These plains are interpreted to be of volcanic origin. The dark plains may be formed of a complex of overlapping volcanic flows. For example, the somewhat darker region of plains in the lower left (southwest) corner of the image may be a different age series of plains forming volcanic lava flows. Finally, the narrow bright line crossing the image in its lower part is interpreted to be a fault which cross cuts both plains units and is thus the youngest event in

  12. Two-dimensional current-carrying plasma sheet in the near-Earth geomagnetic tail region:a quasi-stationary evolution

    Directory of Open Access Journals (Sweden)

    A. V. Manankova

    2003-12-01

    Full Text Available A problem concerning stationary configurations of an inhomogeneous, current-carrying, two-dimensional plasma sheet as the solution of the Grad–Shafranov equation with boundary conditions given on cross-sheet profiles at the  foot of the sheet and at infinity is considered, with the aim of using its solution for the description of the interaction of two current systems: the current system of the geomagnetic field, and the tail currents. The obtained solution is an exact analytical solution which contains 5 independent parameters characterizing the intensity of the current sheet. As the solution is exact, it may be applied to describe the most interesting transitional magnetospheric region: that of a strong interaction between the magnetic fields of the geodipole and of the current sheet, i.e. the region where characteristic scales of the change of all variables along and across the sheet are of the same order. This makes it possible to model the structure of the transitional region and its dynamics under quasi-stationary variation of the input parameters. The obtained solution describes the principal processes developing at various phases of magnetospheric disturbances, such as (1 formation of a very intense thin current sheet localized within the transition region, (2 changing from the quasi-dipolar magnetic field to the configuration when a "neck" is formed in this region. An important feature of the obtained solution is the existence of a critical value of one of the parameters of the problem, which leads to the change in the geomagnetic field configuration described above. The solution can be used as an initial condition in simulating dynamical processes in the magnetotail current sheet, as well as in testing the current sheet stability. In the summary a series of limitations in the model problem under consideration is discussed. Key words. Magnetospheric physics (magnetotail; plasma sheet; magnetospheric configuration and dynamics

  13. Two-dimensional current-carrying plasma sheet in the near-Earth geomagnetic tail region:a quasi-stationary evolution

    Directory of Open Access Journals (Sweden)

    A. V. Manankova

    Full Text Available A problem concerning stationary configurations of an inhomogeneous, current-carrying, two-dimensional plasma sheet as the solution of the Grad–Shafranov equation with boundary conditions given on cross-sheet profiles at the  foot of the sheet and at infinity is considered, with the aim of using its solution for the description of the interaction of two current systems: the current system of the geomagnetic field, and the tail currents. The obtained solution is an exact analytical solution which contains 5 independent parameters characterizing the intensity of the current sheet. As the solution is exact, it may be applied to describe the most interesting transitional magnetospheric region: that of a strong interaction between the magnetic fields of the geodipole and of the current sheet, i.e. the region where characteristic scales of the change of all variables along and across the sheet are of the same order. This makes it possible to model the structure of the transitional region and its dynamics under quasi-stationary variation of the input parameters. The obtained solution describes the principal processes developing at various phases of magnetospheric disturbances, such as (1 formation of a very intense thin current sheet localized within the transition region, (2 changing from the quasi-dipolar magnetic field to the configuration when a "neck" is formed in this region. An important feature of the obtained solution is the existence of a critical value of one of the parameters of the problem, which leads to the change in the geomagnetic field configuration described above. The solution can be used as an initial condition in simulating dynamical processes in the magnetotail current sheet, as well as in testing the current sheet stability. In the summary a series of limitations in the model problem under consideration is discussed. Key words. Magnetospheric physics (magnetotail; plasma sheet; magnetospheric configuration and dynamics

  14. New perspectives on the accretion and internal evolution of Venus

    Science.gov (United States)

    O'Rourke, J. G.

    2017-12-01

    Dichotomous conditions on Earth and Venus present one of the most compelling mysteries in our Solar System. Ongoing debate centers on how the internal dynamics of Venus have shaped its atmospheric composition, surface features, and even habitability over geologic time. In particular, Venus may have resembled Earth for billions of years before suffering catastrophic transformation, or perhaps some accretionary process set these twin planets on divergent paths from the beginning. Unfortunately, the limited quality of decades-old data—particularly the low resolution of radar imagery and global topography from NASA's Magellan mission—harms our ability to draw definite conclusions. But some progress is possible given recent advances in modeling techniques and improved topography derived from stereo images that are available for roughly twenty percent of the surface. Here I present simulations of the interior evolution of Venus consistent with all available constraints and, more importantly, identify future measurements that would dramatically narrow the range of acceptable scenarios. Obtaining high-resolution imagery and topography, along with any information about the temporal history of a magnetic field, is extremely important. Deformation of geologic features constrains the surface heat flow and lithospheric rheology during their formation. Determining whether craters with radar-dark floors (which comprise 80% of the population) are actually embayed by lava flows would finally settle the controversy over catastrophic versus equilibrium resurfacing. If the core of Venus has completely solidified, then the lack of an internally generated magnetic field today is unsurprising. We might expect dynamo action in the past since relatively high mantle temperatures may increase the rate of core cooling—unless a lack of giant impacts during accretion permitted chemical stratification that resists convection. In any case, uncertainty about our celestial cousin reveals a

  15. Importance of Including Topography in Numerical Simulations of Venus' Atmospheric Circulation

    Science.gov (United States)

    Parish, H. F.; Schubert, G.; Lebonnois, S.; Covey, C. C.; Walterscheid, R. L.; Grossman, A.

    2012-12-01

    Venus' atmosphere is characterized by strong superrotation, in which the wind velocities at cloud heights are around 60 times faster than the surface rotation rate. The reasons for this strong superrotation are still not well understood. Since the surface of the planet is both a source and sink of atmospheric angular momentum it is important to understand and properly account for the interactions at the surface-atmosphere boundary. A key aspect of the surface-atmosphere interaction is the topography. Topography has been introduced into different general circulation models (GCMs) of Venus' atmosphere, producing significant, but widely varying effects on the atmospheric circulation. The reasons for the inconsistencies among model results are not well known, but our studies suggest they might be related to the influences of different dynamical cores. In our recent study, we have analyzed the angular momentum budget for two Venus GCMs, the Venus Community Atmosphere model (Venus CAM) and the Laboratoire de Meteorologie Dynamique (LMD) Venus GCM. Because of Venus' low magnitude surface winds, surface friction alone supplies only a relatively weak angular momentum forcing to the atmosphere. We find that if surface friction is introduced without including surface topography, the angular momentum balance of the atmosphere may be dominated by effects such as numerical diffusion, a sponge layer, or other numerical residuals that are generally included in all GCMs, and can themselves be sources of angular momentum. However, we find the mountain torque associated with realistic Venus surface topography supplies a much larger source of angular momentum than the surface friction, and dominates nonphysical numerical terms. (A similar effect occurs for rapidly rotating planets like Earth, but in this case numerical errors in the angular momentum budget are relatively small even in the absence of mountain torque). Even if surface friction dominates numerical terms in the angular

  16. Geologic processes on Venus: an update

    Science.gov (United States)

    Masursky, H.

    Studies of Venera 15 and 16 radar image and altimetry data and reevaluation of Pioneer Venus and earlier Venera data have greatly expanded the perception of the variety and complexity of geologic processes on Venus. PV data have discriminated four highland regions (each different in geomorphic appearance), a large upland rolling plains region, and smaller areas of lowland plains. Two highland volcanic centers were identified that may be presently active, as suggested by their geomorphologic appearance combined with positive gravity anomalies, lightning strike clusters, and a change in SO2 content in the upper atmosphere. Geochemical data obtained by the Venera landers have indicated that one upland area and nearby rolling plains are composed of volcanic rocks, probably basalts or syenites. New Venera radar images of the Ishtar Terra region show folded and/or faulted linear terrain and associated volcanic features that may have been deformed by both compressional and extensional forces. Lowland surfaces resemble the mare basaltic lava flows that fill basins on the Moon, Mars and Earth. Ubiquitous crater like forms may be of either volcanic or impact origin; the origin of similar lunar features was determined by the character of their ejecta deposits.

  17. The result of Venus Orbit Insertion of Akatsuki on December 7th, 2015

    Science.gov (United States)

    Sugiyama, K. I.; Nakamura, M.; Imamura, T.; Ishii, N.; Abe, T.; Kawakatsu, Y.; Hirose, C.; Satoh, T.; Suzuki, M.; Ueno, M.; Yamazaki, A.; Iwagami, N.; Watanabe, S.; Taguchi, M.; Fukuhara, T.; Takahashi, Y.; Yamada, M.; Imai, M.; Ohtsuki, S.; Uemizu, K.; Hashimoto, G. L.; Takagi, M.; Matsuda, Y.; Ogohara, K.; Sato, N.; Kasaba, Y.; Kouyama, T.; Hirata, N.; Nakamura, R.; Yamamoto, Y.; Horinouchi, T.; Yamamoto, M.; Hayashi, Y. Y.; Nakatsuka, J.; Kashimura, H.; Sakanoi, T.; Ando, H.; Murakami, S. Y.; Sato, T.; Takagi, S.; Nakajima, K.; Peralta, J.; Lee, Y. J.

    2015-12-01

    Japan launched Venus Climate Orbiter 'Akatsuki' (JAXA's mission code name: PLANET-C) to observe the dynamics of the Venus atmosphere globally and clarify the mechanism of the atmospheric circulation. The launch was on May 21st , 2010 from the Tanegashima Space Center. The cruise to Venus was smooth, however, the first Venus Orbit Insertion (VOI) trial on December 7th, 2010 tuned out to be a failure. Later Akatsuki has been orbiting the sun. Fortunately we keep the spacecraft in a healthy condition and surprisingly we have found another chance to let this spacecraft to meet Venus in 2015. Next VOI trial will be done on December 7th, 2015 and we report the result of this operation at this AGU meeting. This mission is planed to answer the question described below. The radius of the Earth and Venus are almost the same. In addition the radiation from the sun is also almost the same. The climates of these planets, however, are much different. For example, the strong zonal wind is observed on Venus with the period of 4 days, where Venus rotates westward with the period of 243 days. The wind speed is about 100 m s-1. This is called super rotation. We will investigate from data from Akatsuki what attributes to the difference of the climates between Earth and Venus. AKATSUKI was designed for remote sensing from an equatorial, elliptical orbit to tract the atmospheric motion at different altitudes using 5 cameras (3xIR, UV, Visible) and by the radio occultation technique. The first VOI has failed due to a malfunction of the propulsion system. The check valve between the helium tank and the fuel tank was blocked by an unexpected salt formation during the cruising from the Earth to Venus. As a result the main engine (orbital maneuvering engine, OME) became oxidizer-rich and fuel-poor condition, which led to an abnormal combustion in the engine with high temperature, and finally the engine was broken. We decide to use RCS thrusters for Trajectory Control Maneuvers' (TCMs) and

  18. Nonthermal escape of hydrogen and deuterium from Venus and implications for loss of water

    Science.gov (United States)

    Kumar, S.; Hunten, D. M.; Pollack, J. B.

    1983-01-01

    As the dominant nonthermal mechanism for the escape of hydrogen in past Venus atmospheres, the charge exchange of H(+) with H would have provided an escape flux close to the diffusion-limiting value for H-mixing ratios up to 0.002 at the homopause, which also marks the onset of hydrodynamic flow. Charge exchange therefore represents a viable mechanism through which Venus could have lost up to an earth-equivalent ocean of water from its atmosphere over geologic time. Present Venus atmosphere estimates are based on in situ Pioneer Venus mission measurements, and assumptions in the course of extrapolation to past atmospheres have been with respect to the nature of the bulge, circulation pattern, and ion temperature.

  19. LIBS Testing in a Venus Environment Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Configure LIBS system to view samples in the Venus chamber Confirm STP results for LIBS in Venus Chamber configuration Conduct high temperature/high pressure...

  20. Mission Architecture and Technology Options for a Flagship Class Venus In Situ Mission

    Science.gov (United States)

    Balint, Tibor S.; Kwok, Johnny H.; Kolawa, Elizabeth A.; Cutts, James A.; Senske, David A.

    2008-01-01

    Venus, as part of the inner triad with Earth and Mars, represents an important exploration target if we want to learn more about solar system formation and evolution. Comparative planetology could also elucidate the differences between the past, present, and future of these three planets, and can help with the characterization of potential habitable zones in our solar system and, by extension, extrasolar systems. A long lived in situ Venus mission concept, called the Venus Mobile Explorer, was prominently featured in NASA's 2006 SSE Roadmap and supported in the community White Paper by the Venus Exploration Analysis Group (VEXAG). Long-lived in situ missions are expected to belong to the largest (Flagship) mission class, which would require both enabling and enhancing technologies beside mission architecture options. Furthermore, extreme environment mitigation technologies for Venus are considered long lead development items and are expected to require technology development through a dedicated program. To better understand programmatic and technology needs and the motivating science behind them, in this fiscal year (FY08) NASA is funding a Venus Flaghip class mission study, based on key science and technology drivers identified by a NASA appointed Venus Science and Technology Definition Team (STDT). These mission drivers are then assembled around a suitable mission architecture to further refine technology and cost elements. In this paper we will discuss the connection between the final mission architecture and the connected technology drivers from this NASA funded study, which - if funded - could enable a future Flagship class Venus mission and potentially drive a proposed Venus technology development program.

  1. Venus Atmospheric Maneuverable Platform (VAMP)

    Science.gov (United States)

    Griffin, K.; Sokol, D.; Lee, G.; Dailey, D.; Polidan, R.

    2013-12-01

    We have explored a possible new approach to Venus upper atmosphere exploration by applying recent Northrop Grumman (non-NASA) development programs to the challenges associated with Venus upper atmosphere science missions. Our concept is a low ballistic coefficient (gas, wing span, vehicle mass, power supply, propulsion, materials considerations, structural elements, subsystems, and packaging. The interaction between the VAMP vehicle and the supporting orbiter will also be discussed. In this context, we will specifically focus upon four key factors impacting the design and performance of VAMP: 1. Feasibility of and options for the deployment of the vehicle in space 2. Entry into the Venus atmosphere, including descent profile, heat rate, total heat load, stagnation temperature, control, and entry into level flight 3. Characteristics of flight operations and performance in the Venus atmosphere: altitude range, latitude and longitude access, day/night performance, aircraft performance (aerodynamics, power required vs. power available, propulsion, speed, percent buoyancy), performance sensitivity to payload weight 4. Science payload accommodation, constraints, and opportunities We will discuss interdependencies of the above factors and the manner in which the VAMP strawman's characteristics affect the CONOPs and the science objectives. We will show how the these factors provide constraints as well as enable opportunities for novel long duration scientific studies of the Venus upper atmosphere that support VEXAG goals 2 and 3. We will also discuss how the VAMP platform itself can facilitate some of these science measurements.

  2. Investigating the Origin and Evolution of Venus with in Situ Mass Spectrometry

    Science.gov (United States)

    Trainer, M. G.; Mahaffy, P. R.; Brinckerhoff, W. B.; Johnson, N. M.; Glaze, L. S.

    2016-01-01

    The exploration of Venus continues to be a top priority of planetary science. The Planetary Decadal Survey goals for inner-planet exploration seek to discern the origin and diversity of terrestrial planets, understand how the evolution of terrestrial planets relates to the evolution of life, and explore the processes that control climate on Earth-like planets. These goals can only be realized through continued and extensive exploration of Venus, the most mysterious of the terrestrial planets, remarkably different from the Earth despite the gross similarities between these "twin planets". It is unknown if this apparent divergence was intrinsic, programmed during accretion from distinct nebular reservoirs, or a consequence of either measured or catastrophic processes during planetary evolution. Even if the atmosphere of Venus is a more "recent" development, its relationship to the resurfacing of the planet's enigmatic surface is not well understood. Resolving such uncertainties directly addresses the hypothesis of a more clement, possibly water-rich era in Venus' past as well as whether Earth could become more Venus-like in the future.

  3. Transits of Venus in Public Education and Contemporary Research

    Science.gov (United States)

    Pasachoff, J. M.

    2011-10-01

    Transits of Venus are among the rarest predictable astronomical event that humans can enjoy, and the 2012 transit will be visible by almost all the people on Earth. It is our job as educators to bring out the thrill of being able to see the tiny dot of Venus silhouetted against the solar disk even with just a simple eye-protection filter. My Website at http://www.transitofvenus.info brings together not only historical information about the five previous transits of Venus that were observed through the 20th century--1639, 1761, 1769, 1874, and 1882--but also the scientific work carried out at the 2004 transit and at recent transits of Mercury. Based on space observations of the 1999 transit of Mercury with NASA's Transition Region and Coronal Explorer (TRACE), Glenn Schneider and I provided proof of the contemporary explanation of the black-drop effect as an amalgam of instrumental point-spread and solar limb-darkening [1]. Based on observations of the changes in the total solar irradiance during the transit, we provided an analysis of this solar-system analogue to exoplanet transits [2]. High-resolution (0.5 arcsec pixels) observations of ingress and egress with TRACE during the 2004 transit provided information about the visibility of Venus's atmosphere through its refraction of sunlight, interpreted with Venus Express observations [3]. We anticipate observing the 2012 transit with groundbased facilities of the University of Hawaii at Haleakala, and of the National Solar Observatory at Sacramento Peak, and Kitt Peak, as well as with NASA and JAXA spacecraft, including Solar Dynamics Observatory, ACRIMsat, and Hinode. The Program Group on Public Education on the Occasions of Eclipses and Transits of Commission 46 on Education and Development of the International Astronomical Union, which I chair, looks forward to participating in Education and Public Outreach efforts related to the 2012 transit.

  4. Venus project : experimentation at ENEA's pilot site

    International Nuclear Information System (INIS)

    Bargellini, M.L.; Fontana, F.; Niccolai, L.; Scavino, G.; Mancini, R.; Levialdi, S.

    1996-12-01

    The document describes the ENEA's (Italian Agency for New Technologies, Energy and the Environment) experience in the Venus Project (Esprit III 6398). Venus is an advanced visual interface based on icon representation that permits to end-user to inquiry databases. VENUS interfaces to ENEA's databases: cometa materials Module, Cometa Laboratories Module and European Programs. This report contents the results of the experimentation and of the validation carried out in ENEA's related to the Venus generations. Moreover, the description of the architecture, the user requirements syntesis and the validation methodology of the VENUS systems have been included

  5. Venus Global Reference Atmospheric Model

    Science.gov (United States)

    Justh, Hilary L.

    2017-01-01

    Venus Global Reference Atmospheric Model (Venus-GRAM) is an engineering-level atmospheric model developed by MSFC that is widely used for diverse mission applications including: Systems design; Performance analysis; Operations planning for aerobraking, Entry, Descent and Landing, and aerocapture; Is not a forecast model; Outputs include density, temperature, pressure, wind components, and chemical composition; Provides dispersions of thermodynamic parameters, winds, and density; Optional trajectory and auxiliary profile input files Has been used in multiple studies and proposals including NASA Engineering and Safety Center (NESC) Autonomous Aerobraking and various Discovery proposals; Released in 2005; Available at: https://software.nasa.gov/software/MFS-32314-1.

  6. Kepler-1649b: An Exo-Venus in the Solar Neighborhood

    Energy Technology Data Exchange (ETDEWEB)

    Angelo, Isabel; Rowe, Jason F.; Huber, Daniel [SETI Institute, Mountain View, CA 94043 (United States); Howell, Steve B.; Quintana, Elisa V.; Burningham, Ben; Barclay, Thomas [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Still, Martin [Bay Area Environmental Research Institute, 625 2nd Street, Suite 209, Petaluma, CA 94952 (United States); Mann, Andrew W. [Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States); Ciardi, David R. [NASA Exoplanet Science Institute/Caltech, Pasadena, CA (United States); Kane, Stephen R., E-mail: isabelangelo@berkeley.edu [Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132 (United States)

    2017-04-01

    The Kepler mission has revealed that Earth-sized planets are common, and dozens have been discovered to orbit in or near their host star’s habitable zone. A major focus in astronomy is to determine which of these exoplanets are likely to have Earth-like properties that are amenable to follow-up with both ground- and future space-based surveys, with an ultimate goal of probing their atmospheres to look for signs of life. Venus-like atmospheres will be of particular interest in these surveys. While Earth and Venus evolved to have similar sizes and densities, it remains unclear what factors led to the dramatic divergence of their atmospheres. Studying analogs to both Earth and Venus can thus shed light on the limits of habitability and the potential for life on known exoplanets. Here, we present the discovery and confirmation of Kepler-1649b, an Earth-sized planet orbiting a nearby M5V star that receives incident flux at a level similar to that of Venus. We present our methods for characterizing the star, using a combination of point-spread function photometry, ground-based spectroscopy, and imaging, to confirm the planetary nature of Kepler-1649b. Planets like Kepler-1649b will be prime candidates for atmospheric and habitability studies in the next generation of space missions.

  7. Non-Cooled Power System for Venus Lander

    Science.gov (United States)

    Salazar, Denise; Landis, Geoffrey A.; Colozza, Anthony J.

    2014-01-01

    The Planetary Science Decadal Survey of 2013-2022 stated that the exploration of Venus is of significant interest. Studying the seismic activity of the planet is of particular importance because the findings can be compared to the seismic activity of Earth. Further, the geological and atmospheric properties of Venus will shed light into the past and future of Earth. This paper presents a radioisotope power system (RPS) design for a small low-power Venus lander. The feasibility of the new power system is then compared to that of primary batteries. A requirement for the power source system is to avoid moving parts in order to not interfere with the primary objective of the mission - to collect data about the seismic activity of Venus using a seismometer. The target mission duration of the lander is 117 days, a significant leap from Venera 13, the longest-lived lander on the surface of Venus, which survived for 2 hours. One major assumption for this mission design is that the power source system will not provide cooling to the other components of the lander. This assumption is based on high-temperature electronics technology that will enable the electronics and components of the lander to operate at Venus surface temperature. For the proposed RPS, a customized General Purpose Heat Source Radioisotope Thermoelectric Generator (GPHSRTG) is designed and analyzed. The GPHS-RTG is chosen primarily because it has no moving parts and it is capable of operating for long duration missions on the order of years. This power system is modeled as a spherical structure for a fundamental thermal analysis. The total mass and electrical output of the system are calculated to be 24 kilograms and 26 Watts, respectively. An alternative design for a battery-based power system uses Sodium Sulfur batteries. To deliver a similar electrical output for 117 days, the battery mass is calculated to be 234 kilograms. Reducing mission duration or power required will reduce the required battery mass

  8. Applicability of ultralow-frequency global resonances for investigating lightning activity on Venus

    International Nuclear Information System (INIS)

    Nikolaenko, A.P.; Rabinovich, L.M.

    1987-01-01

    The application to experiments on Venus of methods of investigating global lightning activity that are used on earth in the ultralow-frequency range is discussed. Calculations of the electromagnetic fields in the range from a few Hertz to tens of Hertz are carried out in the framework of the model of the lower ionosphere of Venus, which generalizes the information about the planet's atmosphere which is presently available. The calculations showed that observations of global resonances on Venus must, as on the earth, allow one to obtain data about the global distribution of lightning in space and time, and to make the values of the parameters of the lower ionosphere model more precise

  9. Towards Understanding the Climate of Venus Applications of Terrestrial Models to Our Sister Planet

    CERN Document Server

    Bonnet, Roger-Maurice; Grinspoon, David; Koumoutsaris, Symeon; Lebonnois, Sebastien; Titov, Dmitri

    2013-01-01

    ESA’s Venus Express Mission has monitored Venus since April 2006, and scientists worldwide have used mathematical models to investigate its atmosphere and model its circulation. This book summarizes recent work to explore and understand the climate of the planet through a research program under the auspices of the International Space Science Institute (ISSI) in Bern, Switzerland. Some of the unique elements that are discussed are the anomalies with Venus’ surface temperature (the huge greenhouse effect causes the surface to rise to 460°C, without which would plummet as low as -40°C), its unusual lack of solar radiation (despite being closer to the Sun, Venus receives less solar radiation than Earth due to its dense cloud cover reflecting 76% back) and the juxtaposition of its atmosphere and planetary rotation (wind speeds can climb up to 200 m/s, much faster than Venus’ sidereal day of 243 Earth-days).

  10. Long-Lived Venus Lander Conceptual Design: How To Keep It Cool

    Science.gov (United States)

    Dyson, Ridger W.; Schmitz, Paul C.; Penswick, L. Barry; Bruder, Geoffrey A.

    2009-01-01

    Surprisingly little is known about Venus, our neighboring sister planet in the solar system, due to the challenges of operating in its extremely hot, corrosive, and dense environment. For example, after over two dozen missions to the planet, the longest-lived lander was the Soviet Venera 13, and it only survived two hours on the surface. Several conceptual Venus mission studies have been formulated in the past two decades proposing lander architectures that potentially extend lander lifetime. Most recently, the Venus Science and Technology Definition Team (STDT) was commissioned by NASA to study a Venus Flagship Mission potentially launching in the 2020- 2025 time-frame; the reference lander of this study is designed to survive for only a few hours more than Venera 13 launched back in 1981! Since Cytherean mission planners lack a viable approach to a long-lived surface architecture, specific scientific objectives outlined in the National Science Foundation Decadal Survey and Venus Exploration Advisory Group final report cannot be completed. These include: mapping the mineralogy and composition of the surface on a planetary scale determining the age of various rock samples on Venus, searching for evidence of changes in interior dynamics (seismometry) and its impact on climate and many other key observations that benefit with time scales of at least a full Venus day (Le. daylight/night cycle). This report reviews those studies and recommends a hybrid lander architecture that can survive for at least one Venus day (243 Earth days) by incorporating selective Stirling multi-stage active cooling and hybrid thermoacoustic power.

  11. Venus and Mercury as Planets

    Science.gov (United States)

    1974-01-01

    A general evolutionary history of the solar planetary system is given. The previously observed characteristics of Venus and Mercury (i.e. length of day, solar orbit, temperature) are discussed. The role of the Mariner 10 space probe in gathering scientific information on the two planets is briefly described.

  12. Venus and Mercury as planets

    International Nuclear Information System (INIS)

    1974-01-01

    A general evolutionary history of the solar planetary system is given. The previously observed characteristics of Venus and Mercury (i.e. length of day, solar orbit, temperature) are discussed. The role of the Mariner 10 space probe in gathering scientific information on the two planets is briefly described

  13. A statistical study of ionopause perturbation and associated boundary wave formation at Venus.

    Science.gov (United States)

    Chong, G. S.; Pope, S. A.; Walker, S. N.; Zhang, T.; Balikhin, M. A.

    2017-12-01

    In contrast to Earth, Venus does not possess an intrinsic magnetic field. Hence the interaction between solar wind and Venus is significantly different when compared to Earth, even though these two planets were once considered similar. Within the induced magnetosphere and ionosphere of Venus, previous studies have shown the existence of ionospheric boundary waves. These structures may play an important role in the atmospheric evolution of Venus. By using Venus Express data, the crossings of the ionopause boundary are determined based on the observations of photoelectrons during 2011. Pulses of dropouts in the electron energy spectrometer were observed in 92 events, which suggests potential perturbations of the boundary. Minimum variance analysis of the 1Hz magnetic field data for the perturbations is conducted and used to confirm the occurrence of the boundary waves. Statistical analysis shows that they were propagating mainly in the ±VSO-Y direction in the polar north terminator region. The generation mechanisms of boundary waves and their evolution into the potential nonlinear regime are discussed and analysed.

  14. Transits of Venus and Colonial India

    Science.gov (United States)

    Kochhar, Rajesh

    2012-09-01

    Astronomical expeditions during the colonial period had a political and national significance also. Measuring the earth and mapping the sky were activities worthy of powerful and power- seeking nations. Such was the sanctity of global astronomical activity that many other agendas could be hidden under it. An early astronomy-related expedition turned out to be extremely beneficial, to botany. The expedition sent by the French Government in 1735 to South America under the leadership of Charles Marie de la Condamine (1701--1774) ostensibly for the measurement of an arc of the meridian at Quito in Ecuador surreptitiously collected data that enabled Linnaeus to describe the genus cinchona in 1742. When the pair of transits of Venus occurred in 1761 and 1769, France and England were engaged in a bitter rivalry for control of India. The observation of the transits became a part of the rivalry. A telescope presented by the British to a South Indian King as a decorative toy was borrowed back for actual use. Scientifically the transit observations were a wash out, but the exercise introduced Europe to details of living Indian tradition of eclipse calculations. More significantly, it led to the institutionalization of modern astronomy in India under the auspices of the English East India Company (1787). The transits of Venus of 1874 and 1882 were important not so much for the study of the events as for initiating systematic photography of the Sun. By this, Britain owned most of the world's sunshine, and was expected to help European solar physicists get data from its vast Empire on a regular basis. This and the then genuinely held belief that a study of the sun would help predict failure of monsoons led to the institutionalization of solar physics studies in India (1899). Of course, when the solar physicists learnt that solar activity did not quite determine rainfall in India, they forgot to inform the Government.

  15. Venus Express en route to probe the planet's hidden mysteries

    Science.gov (United States)

    2005-11-01

    Venus Express will eventually manoeuvre itself into orbit around Venus in order to perform a detailed study of the structure, chemistry and dynamics of the planet's atmosphere, which is characterised by extremely high temperatures, very high atmospheric pressure, a huge greenhouse effect and as-yet inexplicable "super-rotation" which means that it speeds around the planet in just four days. The European spacecraft will also be the first orbiter to probe the planet's surface while exploiting the "visibility windows" recently discovered in the infrared waveband. The 1240 kg mass spacecraft was developed for ESA by a European industrial team led by EADS Astrium with 25 main contractors spread across 14 countries. It lifted off onboard a Soyuz-Fregat rocket, the launch service being provided by Starsem. The lift-off from the Baikonur Cosmodrome in Kazakstan this morning took place at 09:33 hours local time (04:33 Central European Time). Initial Fregat upper-stage ignition took place 9 minutes into the flight, manoeuvring the spacecraft into a low-earth parking orbit. A second firing, 1 hour 22 minutes later, boosted the spacecraft to pursue its interplanetary trajectory. Contact with Venus Express was established by ESA's European Space Operations Centre (ESOC) at Darmstadt, Germany approximately two hours after lift-off. The spacecraft has correctly oriented itself in relation to the sun and has deployed its solar arrays. All onboard systems are operating perfectly and the orbiter is communicating with the Earth via its low-gain antenna. In three days' time, it will establish communications using its high-gain antenna. Full speed ahead for Venus Venus Express is currently distancing itself from the Earth full speed, heading on its five-month 350 million kilometre journey inside our solar system. After check-outs to ensure that its onboard equipment and instrument payload are in proper working order, the spacecraft will be mothballed, with contact with the Earth being

  16. Composition and Chemistry of the Neutral Atmosphere of Venus

    Science.gov (United States)

    Marcq, Emmanuel; Mills, Franklin P.; Parkinson, Christopher D.; Vandaele, Ann Carine

    2018-02-01

    This paper deals with the composition and chemical processes occurring in the neutral atmosphere of Venus. Since the last synthesis, observers as well as modellers have emphasised the spatial and temporal variability of minor species, going beyond a static and uniform picture that may have prevailed in the past. The outline of this paper acknowledges this situation and follows closely the different dimensions along which variability in composition can be observed: vertical, latitudinal, longitudinal, temporal. The strong differences between the atmosphere below and above the cloud layers also dictate the structure of this paper. Observational constraints, obtained from both Earth and Venus Express, as well as 1D, 2D and 3D models results obtained since 1997 are also extensively referred and commented by the authors. An non-exhaustive list of topics included follows: modelled and observed latitudinal and vertical profiles of CO and OCS below the clouds of Venus; vertical profiles of CO and SO2 above the clouds as observed by solar occultation and modelled; temporal and spatial variability of sulphur oxides above the clouds. As a conclusion, open questions and topics of interest for further studies are discussed.

  17. Investigating gravity waves evidences in the Venus upper atmosphere

    Science.gov (United States)

    Migliorini, Alessandra; Altieri, Francesca; Shakun, Alexey; Zasova, Ludmila; Piccioni, Giuseppe; Bellucci, Giancarlo; Grassi, Davide

    2014-05-01

    We present a method to investigate gravity waves properties in the upper mesosphere of Venus, through the O2 nightglow observations acquired with the imaging spectrometer VIRTIS on board Venus Express. Gravity waves are important dynamical features that transport energy and momentum. They are related to the buoyancy force, which lifts air particles. Then, the vertical displacement of air particles produces density changes that cause gravity to act as restoring force. Gravity waves can manifest through fluctuations on temperature and density fields, and hence on airglow intensities. We use the O2 nightglow profiles showing double peaked structures to study the influence of gravity waves in shaping the O2 vertical profiles and infer the waves properties. In analogy to the Earth's and Mars cases, we use a well-known theory to model the O2 nightglow emissions affected by gravity waves propagation. Here we propose a statistical discussion of the gravity waves characteristics, namely vertical wavelength and wave amplitude, with respect to local time and latitude. The method is applied to about 30 profiles showing double peaked structures, and acquired with the VIRTIS/Venus Express spectrometer, during the mission period from 2006-07-05 to 2008-08-15.

  18. Specular Reflections: John Brett and the Mirror of Venus

    Directory of Open Access Journals (Sweden)

    James Mussell

    2013-10-01

    Full Text Available Normal 0 false false false EN-GB X-NONE X-NONE MicrosoftInternetExplorer4 When John Brett, the Pre-Raphaelite painter and astronomer, presented his theory of specular reflection in Venus to the Royal Astronomical Society, he provoked a controversy over both the constitution of the planet and the learned society. Brett thought Venus was most likely a ball of molten metal enclosed in a glass envelope and this raised the tantalizing possibility that it might function as a mirror, reflecting back an image of the earth. A few months later another 'Mirror of Venus 'was displayed at the Grosvenor Gallery. The surface of Edward Burne-Jones's painting provides a different model of reflection but one that illuminates the space of the Royal Astronomical Society and the practice of astronomy more broadly. Using Burne-Jones’s painting as a point of comparison, I argue that Brett’s astronomy put into play a desiring, viewing subject that was disavowed in his landscape art.

  19. Magellan: A new view of Venus' geology and geophysics

    Science.gov (United States)

    Bindschadler, D. L.

    1995-07-01

    Within the past fifteen years, the surface of Venus has gone from being the least well understood of all the terrestrial planets to the most thoroughly mapped surface of any terrestrial planet, including the Earth. This is primarily due to the Magellan mission, which has collected a variety of data on the surface morphology, physical properties, and interior density structure of Venus amounting to more than 1 Terabit (1012 bits) of data. Synthetic aperture radar images have been obtained for over 95% of the surface; their high resolution reveals most surface features larger than 100-200 meters across. Using its radar altimeter, Magellan has collected data on surface elevations, sub-meter scale roughness, and radar reflectivity at a resolution of approximately 10 km. Further information on the physical properties of the surface was gathered by measuring the passive microwave emissivity of the surface [Pettengill et al, 1992]. Two-way Doppler tracking of the spacecraft has yielded line-of-sight (LOS) gravity data and a spherical harmonic model of gravity and geoid out to degree 75. Collection of high-resolution gravity data has been aided by an innovative aerobraking maneuver, which used Venus' atmosphere to brake the spacecraft and lower it from a highly elliptical orbit to a near-circular orbit.

  20. Structure and Properties of the Foreshock at Venus

    Science.gov (United States)

    Omidi, N.; Collinson, G.; Sibeck, D.

    2017-10-01

    The interaction of the solar wind with Venus is dominated by the planet's ionosphere that acts as an obstacle to the flow resulting in an induced magnetosphere and bow shock much smaller than their terrestrial counterparts. This study presents a 3-D electromagnetic hybrid (kinetic ions and fluid electrons) simulation of the solar wind interaction with an unmagnetized obstacle to examine the structure and properties of the Cytherean foreshock during periods of near radial IMF, that is, when it lies upstream of the ionosphere. The interaction between the backstreaming ions and the solar wind results in the generation of two classes of ULF waves: (1) parallel propagating sinusoidal waves with periods 20-30 s and (2) highly oblique fast magnetosonic waves. The joint nonlinear evolution of these waves results in the formation of structures called foreshock cavitons with dimensions comparable to the size of the planet. Foreshock cavitons are also present in the terrestrial foreshock. The excavation of plasma and magnetic field from their cores leads to lower average densities and magnetic field strengths in the foreshock. As in the case of Earth, this excavation results in the formation of a fast magnetosonic pulse/shock at the edge of the foreshock named the foreshock compressional boundary. Also similar to Earth is the formation of spontaneous hot flow anomalies (SHFAs) as foreshock cavitons approach the bow shock. The size and properties of SHFAs at Venus are comparable to those at Earth, and their existence has recently been established at Mars and Venus in a companion paper.

  1. Vesper - Venus Chemistry and Dynamics Orbiter - A NASA Discovery Mission Proposal: Submillimeter Investigation of Atmospheric Chemistry and Dynamics

    Science.gov (United States)

    Chin, Gordon

    2011-01-01

    Vesper conducts a focused investigation of the chemistry and dynamics of the middle atmosphere of our sister planet- from the base of the global cloud cover to the lower thermosphere. The middle atmosphere controls the stability of the Venus climate system. Vesper determines what processes maintain the atmospheric chemical stability, cause observed variability of chemical composition, control the escape of water, and drive the extreme super-rotation. The Vesper science investigation provides a unique perspective on the Earth environment due to the similarities in the middle atmosphere processes of both Venus and the Earth. Understanding key distinctions and similarities between Venus and Earth will increase our knowledge of how terrestrial planets evolve along different paths from nearly identical initial conditions.

  2. Venus transits - A French view

    Science.gov (United States)

    Débarbat, Suzanne

    2005-04-01

    After a careful study of Mars observations obtained by Tycho Brahé (1546-1601), Kepler (1571-1630) discovered the now-called Kepler's third law. In 1627 he published his famous Tabulae Rudolphinae, a homage to his protector Rudolph II (1552-1612), tables (Kepler 1609, 1627) from which he predicted Mercury and Venus transits over the Sun. In 1629 Kepler published his Admonitio ad Astronomos Advertisement to Astronomers (Kepler 1630), Avertissement aux Astronomes in French Au sujet de phénomènes rares et étonnants de l'an 1631: l'incursion de Vénus et de Mercure sur le Soleil. This was the beginning of the interest of French astronomers, among many others, in such transits, mostly for Venus, the subject of this paper in which dates are given in the Gregorian calendar.

  3. How the Venus flytrap snaps

    Science.gov (United States)

    Forterre, Yoël; Skotheim, Jan M.; Dumais, Jacques; Mahadevan, L.

    2005-01-01

    The rapid closure of the Venus flytrap (Dionaea muscipula) leaf in about 100ms is one of the fastest movements in the plant kingdom. This led Darwin to describe the plant as ``one of the most wonderful in the world''. The trap closure is initiated by the mechanical stimulation of trigger hairs. Previous studies have focused on the biochemical response of the trigger hairs to stimuli and quantified the propagation of action potentials in the leaves. Here we complement these studies by considering the post-stimulation mechanical aspects of Venus flytrap closure. Using high-speed video imaging, non-invasive microscopy techniques and a simple theoretical model, we show that the fast closure of the trap results from a snap-buckling instability, the onset of which is controlled actively by the plant. Our study identifies an ingenious solution to scaling up movements in non-muscular engines and provides a general framework for understanding nastic motion in plants.

  4. A POTENTIAL SUPER-VENUS IN THE KEPLER-69 SYSTEM

    International Nuclear Information System (INIS)

    Kane, Stephen R.; Gelino, Dawn M.; Barclay, Thomas

    2013-01-01

    Transiting planets have greatly expanded and diversified the exoplanet field. These planets provide greater access to characterization of exoplanet atmospheres and structure. The Kepler mission has been particularly successful in expanding the exoplanet inventory, even to planets smaller than the Earth. The orbital period sensitivity of the Kepler data is now extending into the habitable zones of their host stars, and several planets larger than the Earth have been found to lie therein. Here we examine one such proposed planet, Kepler-69c. We provide new orbital parameters for this planet and an in-depth analysis of the habitable zone. We find that, even under optimistic conditions, this 1.7 R ⊕ planet is unlikely to be within the habitable zone of Kepler-69. Furthermore, the planet receives an incident flux of 1.91 times the solar constant, which is similar to that received by Venus. We thus suggest that this planet is likely a super-Venus rather than a super-Earth in terms of atmospheric properties and habitability, and we propose follow-up observations to disentangle the ambiguity.

  5. Several features of the earthward and tailward streaming of energetic protons (0.29--0.5 MeV) in the earth's plasma sheet

    International Nuclear Information System (INIS)

    Lui, A.T.Y.; Krimigis, S.M.

    1981-01-01

    The characteristics of earthward and tailward streaming of energetic protons (0.29--0.50 MeV) in the magnetotial at downstream distances of 20 to 40 R/sub E/ are examined with approx.5.5-min averaged data from the APL/JHU Charged Particle Measurements Experiment on board the IMP 7 and IMP 8 spacecraft. On the basis of observations from September 1972 to May 1978 it is found that the occurrence frequency of energetic magnetospheric protons streaming either tailward or earthward with a front-to-back flux ratio of >2 is at least 23%. Tailward streaming is found to be prevalent in the postmidnight plasma sheet, while earthward streaming is more frequent in the premidnight sector. The particle spectrum is progressively harder from the dawn flank to the dusk flank of the plasma sheet and is generally harder for tailward streaming than for earthward streaming. It is suggested that the dawn-dusk reversal in the dominant streaming direction results from an underlying circulation pattern of energetic protons in the magnetotail, tailward in the postmidnight region and earthward in the premidnight region

  6. Sulfur dioxide in the Venus atmosphere: I. Vertical distribution and variability

    Science.gov (United States)

    Vandaele, A. C.; Korablev, O.; Belyaev, D.; Chamberlain, S.; Evdokimova, D.; Encrenaz, Th.; Esposito, L.; Jessup, K. L.; Lefèvre, F.; Limaye, S.; Mahieux, A.; Marcq, E.; Mills, F. P.; Montmessin, F.; Parkinson, C. D.; Robert, S.; Roman, T.; Sandor, B.; Stolzenbach, A.; Wilson, C.; Wilquet, V.

    2017-10-01

    Recent observations of sulfur containing species (SO2, SO, OCS, and H2SO4) in Venus' mesosphere have generated controversy and great interest in the scientific community. These observations revealed unexpected spatial patterns and spatial/temporal variability that have not been satisfactorily explained by models. Sulfur oxide chemistry on Venus is closely linked to the global-scale cloud and haze layers, which are composed primarily of concentrated sulfuric acid. Sulfur oxide observations provide therefore important insight into the on-going chemical evolution of Venus' atmosphere, atmospheric dynamics, and possible volcanism. This paper is the first of a series of two investigating the SO2 and SO variability in the Venus atmosphere. This first part of the study will focus on the vertical distribution of SO2, considering mostly observations performed by instruments and techniques providing accurate vertical information. This comprises instruments in space (SPICAV/SOIR suite on board Venus Express) and Earth-based instruments (JCMT). The most noticeable feature of the vertical profile of the SO2 abundance in the Venus atmosphere is the presence of an inversion layer located at about 70-75 km, with VMRs increasing above. The observations presented in this compilation indicate that at least one other significant sulfur reservoir (in addition to SO2 and SO) must be present throughout the 70-100 km altitude region to explain the inversion in the SO2 vertical profile. No photochemical model has an explanation for this behaviour. GCM modelling indicates that dynamics may play an important role in generating an inflection point at 75 km altitude but does not provide a definitive explanation of the source of the inflection at all local times or latitudes The current study has been carried out within the frame of the International Space Science Institute (ISSI) International Team entitled 'SO2 variability in the Venus atmosphere'.

  7. The need for New In Situ Measurements to Understand the Climate, Geology and Evolution of Venus.

    Science.gov (United States)

    Grinspoon, D. H.

    2017-12-01

    , characterize the divergent climate evolution of Venus and Earth and extend our knowledge of the limits of habitability on hot terrestrial planets.

  8. Digital amateur observations of Venus at 0.9μm

    Science.gov (United States)

    Kardasis, E.

    2017-09-01

    Venus atmosphere is extremely dynamic, though it is very difficult to observe any features on it in the visible and even in the near-IR range. Digital observations with planetary cameras in recent years routinely produce high-quality images, especially in the near-infrared (0.7-1μm), since IR wavelengths are less influenced by Earth's atmosphere and Venus's atmosphere is partially transparent in this spectral region. Continuous observations over a few hours may track dark atmospheric features in the dayside and determine their motion. In this work we will present such observations and some dark-feature motion measurements at 0.9μm. Ground-based observations at this wavelength are rare and are complementary to in situ observations by JAXA's Akatsuki orbiter, that studies the atmospheric dynamics of Venus also in this band with the IR1 camera.

  9. Estimation of the rate of volcanism on Venus from reaction rate measurements

    Science.gov (United States)

    Fegley, Bruce, Jr.; Prinn, Ronald G.

    1989-01-01

    Laboratory rate data for the reaction between SO2 and calcite to form anhydrite are presented. If this reaction rate represents the SO2 reaction rate on Venus, then all SO2 in the Venusian atmosphere will disappear in 1.9 Myr unless volcanism replenishes the lost SO2. The required volcanism rate, which depends on the sulfur content of the erupted material, is in the range 0.4-11 cu km of magma erupted per year. The Venus surface composition at the Venera 13, 14, and Vega 2 landing sites implies a volcanism rate of about 1 cu km/yr. This geochemically estimated rate can be used to determine if either (or neither) of two discordant geophysically estimated rates is correct. It also suggests that Venus may be less volcanically active than the earth.

  10. Modeling Venus-like Worlds Through Time and Implications for the Habitable Zone

    Science.gov (United States)

    Way, M.; Del Genio, A. D.; Amundsen, D. S.; Sohl, L. E.; Kiang, N. Y.; Aleinov, I. D.; Kelley, M.

    2017-12-01

    In recent work [1] we demonstrated that the climatic history of Venus may have allowed for surface liquid water to exist for several billion years using a 3D GCM [2]. Model resolution was 4x5 latitude x longitude, 20 atmospheric layers and a 13 layer fully coupled ocean. Several assumptions were made based on what data we have for early Venus: a.) Used a solar spectrum from 2.9 billion years ago, and 715 million years ago for the incident radiation. b.) Assumed Venus had the same slow modern retrograde rotation throughout the 2.9 to 0.715 Gya history explored, although one simulation at faster rotation rate was shown not to be in the HZ. c.) Used atmospheric constituents similar to modern Earth: 1 bar N2, 400ppmv CO2, 1ppmv CH4. d.) Gave the planet a shallow 310m deep ocean constrained by published D/H ratio observations. e.) Used present day Venus topography and one run with Earth topography.In all cases except the faster rotating one the planet was able to maintain surface liquid water. We have now inserted the SOCRATES [3] radiation scheme into our 3D GCM to more accurately calculate heating fluxes for different atmospheric constituents. Using SOCRATES we have explored a number of other possible early histories for Venus including: f.) An aquaplanet configuration at 2.9Gya with present day rotation period.g.) A Land planet configuration at 2.9Gya with the equivalent of 10m of water in soil and lakes. h.) A synchronously rotating version of a, f, and g (supported by recent work of [4] and older work of [5]) i.) A Venus topography with a 310m ocean, but using present day insolation (1.9 x Earth). j.) Versions of most of the worlds above but with solar insolations >1.9 to explore more Venus-like exoplanetary worlds around G-type stars. In these additional cases the planet still resides in the liquid water habitable zone. Studies such as these should help Astronomers better understand whether exoplanets found in the Venus zone [6] are capable of hosting liquid water

  11. The Devil in the Dark: A Fully Self-Consistent Seismic Model for Venus

    Science.gov (United States)

    Unterborn, C. T.; Schmerr, N. C.; Irving, J. C. E.

    2017-12-01

    The bulk composition and structure of Venus is unknown despite accounting for 40% of the mass of all the terrestrial planets in our Solar System. As we expand the scope of planetary science to include those planets around other stars, the lack of measurements of basic planetary properties such as moment of inertia, core-size and thermal profile for Venus hinders our ability to compare the potential uniqueness of the Earth and our Solar System to other planetary systems. Here we present fully self-consistent, whole-planet density and seismic velocity profiles calculated using the ExoPlex and BurnMan software packages for various potential Venusian compositions. Using these models, we explore the seismological implications of the different thermal and compositional initial conditions, taking into account phase transitions due to changes in pressure, temperature as well as composition. Using mass-radius constraints, we examine both the centre frequencies of normal mode oscillations and the waveforms and travel times of body waves. Seismic phases which interact with the core, phase transitions in the mantle, and shallower parts of Venus are considered. We also consider the detectability and transmission of these seismic waves from within the dense atmosphere of Venus. Our work provides coupled compositional-seismological reference models for the terrestrial planet in our Solar System of which we know the least. Furthermore, these results point to the potential wealth of fundamental scientific insights into Venus and Earth, as well as exoplanets, which could be gained by including a seismometer on future planetary exploration missions to Venus, the devil in the dark.

  12. Steel Sheet Pile Walls in Soft Soil

    OpenAIRE

    Kort, D.A.

    2002-01-01

    For almost a century, steel sheet pile walls are applied worldwide as earth retaining structures for excavations and quay walls. Within the framework of the development of European structural codes for Civil Engineering works, the Eurocodes, Eurocode 3 Part 5 for design of steel sheet pile walls was issued in 1997. This code offers possibilities for cheaper and safer steel sheet piling, in comparison with the existing design criteria used in most countries. Two of these design criteria with w...

  13. Carl Sagan and the Exploration of Mars and Venus

    Science.gov (United States)

    Toon, Owen B.; Condon, Estelle P. (Technical Monitor)

    1997-01-01

    Inspired by childhood readings of books by Edgar Rice Burroughs, Carl Sagan's first interest in planetary science focused on Mars and Venus. Typical of much of his career he was skeptical of early views about these planets. Early in this century it was thought that the Martian wave of darkening, a seasonal albedo change on the planet, was biological in origin. He suggested instead that it was due to massive dust storms, as was later shown to be the case. He was the first to recognize that Mars has huge topography gradients across its surface. During the spacecraft era, as ancient river valleys were found on the planet, he directed studies of Mars' ancient climate. He suggested that changes in the planets orbit were involved in climate shifts on Mars, just as they are on Earth. Carl had an early interest in Venus. Contradictory observations led to a controversy about the surface temperature, and Carl was one of the first to recognize that Venus has a massive greenhouse effect at work warming its surface. His work on radiative transfer led to an algorithm that was extensively used by modelers of the Earth's climate and whose derivatives still dominate the calculation of radiative transfer in planetary atmospheres today. Carl inspired a vast number of young scientists through his enthusiasm for new ideas and discoveries, his skeptical approach, and his boundless energy. I had the privilege to work in Carl's laboratory during the peak of the era of Mars' initial exploration. It was an exciting time, and place. Carl made it a wonderful experience.

  14. Steel Sheet Pile Walls in Soft Soil

    NARCIS (Netherlands)

    Kort, D.A.

    2002-01-01

    For almost a century, steel sheet pile walls are applied worldwide as earth retaining structures for excavations and quay walls. Within the framework of the development of European structural codes for Civil Engineering works, the Eurocodes, Eurocode 3 Part 5 for design of steel sheet pile walls was

  15. Doppler Lidar for Wind Measurements on Venus

    Science.gov (United States)

    Singh, Upendra N.; Emmitt, George D.; Yu, Jirong; Kavaya, Michael J.

    2010-01-01

    NASA Langley Research Center has a long history of developing 2-micron laser transmitter for wind sensing. With support from NASA Laser Risk Reduction Program (LRRP) and Instrument Incubator Program (IIP), NASA Langley Research Center has developed a state-of-the-art compact lidar transceiver for a pulsed coherent Doppler lidar system for wind measurement. The transmitter portion of the transceiver employs the high-pulse-energy, Ho:Tm:LuLiF, partially conductively cooled laser technology developed at NASA Langley. The transceiver is capable of 250 mJ pulses at 10 Hz. It is very similar to the technology envisioned for coherent Doppler lidar wind measurements from Earth and Mars orbit. The transceiver is coupled to the large optics and data acquisition system in the NASA Langley VALIDAR mobile trailer. The large optics consists of a 15-cm off-axis beam expanding telescope, and a full-hemispheric scanner. Vertical and horizontal vector winds are measured, as well as relative backscatter. The data acquisition system employs frequency domain velocity estimation and pulse accumulation. It permits real-time display of the processed winds and archival of all data. This lidar system was recently deployed at Howard University facility in Beltsville, Mary-land, along with other wind lidar systems. Coherent Doppler wind lidar ground-based wind measurements and comparisons with other sensors will be presented. A simulation and data product for wind measurement at Venus will be presented.

  16. New Frontiers Science at Venus from Orbit plus Atmospheric Gas Sampling

    Science.gov (United States)

    Smrekar, Suzanne; Dyar, Melinda; Hensley, Scott; Helbert, Joern; VOX Science and Engineering Teams

    2017-10-01

    Venus remains the most Earth-like body in terms of size, composition, surface age, and insulation. Venus Origins Explorer (VOX) determines how Earth’s twin diverged, and enables breakthroughs in our understanding of rocky planet evolution and habitability. At the time of the Decadal Survey the ability to map mineralogy from orbit (Helbert et al.) and present-day radar techniques to detect active deformation were not fully appreciated. VOX leverages these methods and in-situ noble gases to answer New Frontiers science objectives:1. Atmospheric physics/chemistry: noble gases and isotopes to constrain atmospheric sources, escape processes, and integrated volcanic outgassing; global search for current volcanically outgassed water.2. Past hydrological cycles: global tessera composition to determine the role of volatiles in crustal formation.3. Crustal physics/chemistry: global crustal mineralogy/chemistry, tectonic processes, heat flow, resolve the catastrophic vs. equilibrium resurfacing debate, active geologic processes and possible crustal recycling.4. Crustal weathering: surface-atmosphere weathering reactions from redox state and the chemical equilibrium of the near-surface atmosphere.5. Atmospheric properties/winds: map cloud particle modes and their temporal variations, and track cloud-level winds in the polar vortices.6. Surface-atmosphere interactions: chemical reactions from mineralogy; weathering state between new, recent and older flows; possible volcanically outgassed water.VOX’s Atmosphere Sampling Vehicle (ASV) dips into and samples the well-mixed atmosphere, using Venus Original Constituents Experiment (VOCE) to measure noble gases. VOX’s orbiter carries the Venus Emissivity Mapper (VEM) and the Venus Interferometric Synthetic Aperture Radar (VISAR), and maps the gravity field using Ka-band tracking.VOX is the logical next mission to Venus because it delivers: 1) top priority atmosphere, surface, and interior science; 2) key global data for

  17. Space weather at planet Venus during the forthcoming BepiColombo flybys

    Science.gov (United States)

    McKenna-Lawlor, S.; Jackson, B.; Odstrcil, D.

    2018-03-01

    The BepiColombo (BC) Mission which will be launched in 2018, will include during its Cruise Phase two flybys of Venus and five Mercury flybys. It will then enter a one Earth year orbit about Mercury (with a possible one-year extension) during which two spacecraft, one provided by ESA (MPO) and one provided by JAXA (MMO), will perform both autonomous and coordinated observations of the Hermean environment at various separations. The measurements will take place during the minimum of solar cycle 24 and the rise of solar cycle 25. At the start of the minimum of solar cycle 23, four major flares, each associated with the production of MeV particle radiation and CME activity occurred. Predictions of the HAFv.2 model of the arrival of particle radiation and a travelling shock at Venus on 6 December 2006 were verified by in-situ measurements made aboard Venus Express (VEX) by the ASPERA 4 instrument. Interplanetary scintillation observations, as well as the ENLIL 3-D MHD model when employed separately or in combination, enable the making of predictions of the solar wind density and speed at various locations in the inner heliosphere. Both methods, which outdate HAFv.2, are utilized in the present paper to predict (retrospectively) the arrival of the flare related, interplanetary propagating shock recorded at Venus on 6 December 2006 aboard VEX with a view to putting in place the facility to make very reliable space weather predictions for BC during both its Cruise Phase and when in the Hermean environment itself. The successful matching of the December 2006 predictions with in-situ signatures recorded aboard Venus Express provide confidence that the predictive methodology to be adopted will be appropriate to provide space weather predictions for BepiColombo during its Venus flybys and throughout the mission.

  18. Summing Up the Unique Venus Transit 2004 (VT-2004) Programme

    Science.gov (United States)

    2004-11-01

    On June 8, 2004, Venus - the Earth's sister planet - passed in front of the Sun. This rare event - the last one occurred in 1882 - attracted the attention of millions of people all over the world. In a few days' time, on November 5-7, 2004, about 150 educators, media representatives, as well as amateur and professional astronomers will gather in Paris (France) at the international conference "The Venus Transit Experience" to discuss the outcome of the related Venus Transit 2004 (VT-2004) public education programme. This unique project was set up by the European Southern Observatory (ESO), together with the European Association for Astronomy Education (EAAE), the Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE) and the Observatoire de Paris in France, as well as the Astronomical Institute of the Academy of Sciences of the Czech Republic. It was also supported by the European Commission in the framework of the European Science and Technology Week, cf. ESO PR 03/04. The VT-2004 programme successfully exposed the broad public to a number of fundamental issues at the crucial interface between society and basic science. It ensured the most comprehensive real-time coverage of the event via an extremely dynamic Central Display that was updated a short intervals. Thanks to the prior establishment of hundreds of mirror sites, the VT-2004 website was easily accessible all through the transit, even though it experienced about 55 million webhits during a period of 8 hours. The VT-2004 programme established a wide international network of individuals (including school teachers and their students, amateur astronomers, interested laypeople, etc.) and educational institutions (astronomical observatories, planetaria, science centres, etc.), as well as 25 National Nodes with their own websites about the Venus Transit in as many local languages. It collected a large number of photos and drawings. It also included an international Video Contest, inviting all

  19. Laboratory simulations of volcanic ash charging and conditions for volcanic lightning on Venus

    Science.gov (United States)

    Airey, Martin; Warriner-Bacon, Elliot; Aplin, Karen

    2017-04-01

    Lightning may be important in the emergence of life on Earth and elsewhere, as significant chemical reactions occur in the superheated region around the lightning channel. This, combined with the availability of phosphates in volcanic clouds, suggests that volcanic lightning could have been the catalyst for the formation of biological compounds on the early Earth [1]. In addition to meteorological lightning, volcanic activity also generates electrical discharges within charged ash plumes, which can be a significant contributor to atmospheric electricity on geologically active planets. The physical properties of other planetary atmospheres, such as that of Venus, have an effect on the processes that lead to the generation of volcanic lightning. Volcanism is known to have occurred on Venus in the past, and recent observations made by ESA's Venus Express satellite have provided evidence for currently active volcanism [2-4], and lightning discharges [e.g. 5]. Venusian lightning could potentially be volcanic in origin, since no meteorological mechanisms are known to separate charge effectively in its clouds [6]. The hunt for further evidence for lightning at Venus is ongoing, for example by means of the Lightning and Airglow Camera (LAC) [7] on Akatsuki, the current JAXA mission at Venus. Our laboratory experiments simulate ash generation and measure electrical charging of the ash under typical atmospheric conditions on Earth and Venus. The study uses a 1 litre chamber, which, when pressurised and heated, can simulate the high-pressure, high-temperature, carbon dioxide-dominated atmosphere of Venus at 10 km altitude ( 5 MPa, 650 K). A key finding of previous work [8] is that ash plume-forming eruptions are more likely to occur at higher altitudes such as these on Venus. The chamber contains temperature/pressure monitoring and logging equipment, a rock collision apparatus (based on [9]) to generate the charged rock fragments, and charge measurement electrodes connected

  20. Geologic map of the Artemis Chasma quadrangle (V-48), Venus

    Science.gov (United States)

    Bannister, Roger A.; Hansen, Vicki L.

    2010-01-01

    . So although it seems clear what Artemis is not, there is little consensus about what Artemis is, much less how Artemis formed. Debate during the past decade has resulted in the proposal of at least four hypotheses for Artemis' formation. The first (herein referred to as H1) is that Artemis Chasma represents a zone of northwest-directed convergence and subduction. The second hypothesis (herein referred to as H2) is that Artemis consists of a composite structure with a part of its interior region marking the exposure of deformed ductile deep-crustal rocks analogous to a terrestrial metamorphic core complex. The third (herein referred to as H3) is that Artemis reflects the surface expression of an ancient (>3.5 Ga) huge bolide impact event on cold strong lithosphere. The fourth hypothesis (herein referred to as H4) is that Artemis marks the surface expression of a deep mantle plume. Each of these hypotheses holds different implications for Venus geodynamics and evolution processes, and for terrestrial planet processes in general. Viability of H1 would provide support that terrestrial-like plate-tectonic processes once occurred on Earth's sister planet. The feasibility of H2 would require high values of crustal extension and therefore imply that significant horizontal displacements occurred on Venus-displacement that may or may not be related to terrestrial-like plate-tectonic processes. The possibility of H3 would suggest that Venus' surface is extremely old, and that Venus has experienced very little dynamic activity for the last 3.5 billion years or more; this would further imply that Venus is essentially tectonically dead, and has been for most of its history. This view contrasts strongly with studies that highlight a rich history of Venus including activity at least as young as 750 million years ago, and quite likely up to the present. If H4 has credibility, then Artemis could provide clues to cooling mechanisms of Earth's sister planet. Each of these hypotheses

  1. 225 years of the Venus atmosphere investigations

    International Nuclear Information System (INIS)

    Barsukov, V.L.; Volkov, V.P.

    1986-01-01

    Historical review of investigation into the Venus atmosphere is given. It begins from the discovery of planetary atmosphere made by a great Russian scientist Lomonosov in 1761 till the latest atmosphere investigations by means of the Vega-1 and Vega-2 descent vehicles in 1985 within the framework of the international project for studying. The Venus planet and Halley comet. Results of investigation into physical properties and chemical composition of the planetary atmosphere and surface are present in short

  2. Mars's magnetotail: Nature's current sheet laboratory

    Science.gov (United States)

    Artemyev, A. V.; Angelopoulos, V.; Halekas, J. S.; Runov, A.; Zelenyi, L. M.; McFadden, J. P.

    2017-05-01

    The configuration and stability of an important kinetic plasma structure, the current sheet, determine the efficiency of magnetic energy storage, release, and transport in surrounding plasmas. These properties depend on β (the ratio of plasma pressures to magnetic field pressures) and Mach number M (the ratio of bulk velocities to magnetosonic velocities). For the most investigated current sheet, the near-Earth magnetotail current sheet, these parameters fall within a relatively narrow range of values (high β, low M). To investigate current sheet behavior for a wider range of parameters, we explore current sheets in the magnetotail of Mars using Mars Atmosphere and Volatile Evolution (MAVEN) mission observations. We find that low-β, high-M current sheets are abundant in Mars's magnetotail, but high-β, low-M current sheets can also be found there. Low-β current sheets are nearly force-free, whereas high-M current sheets are balanced by a plasma flow gradient along the tail. We compare current sheet distributions in a (β,M) space for the Martian magnetotail, the near-Earth magnetotail (using Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission), and the distant magnetotail (using Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) mission). We also find that the pressure balance in the Martian magnetotail current sheet can occur by contributions from a wide range of ion species, or, in low beta cases, from field-aligned currents generation of a force-free magnetic field configuration. The Martian magnetotail is a natural laboratory where current sheet of various types can be found and investigated.

  3. High Temperature Venus Drill and Sample Delivery System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We proposed to design, build and test a high temperature Pneumatic Drill and Trencher system for Venus subsurface exploration. The Venus Drill and Trencher will be...

  4. GALILEO ORBITER V POS VENUS TRAJECTORY V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — Galileo Orbiter 60 second sampled trajectory data from the Venus flyby in Venus Solar Orbital (VSO) coordinates. These data cover the interval 1990-02-09 00:00 to...

  5. SAEVe: A Long Duration Small Sat Class Venus Lander

    Science.gov (United States)

    Kremic, T.; Ghail, R.; Gilmore, M.; Kiefer, W.; Limaye, S.; Hunter, G.; Tolbert, C.; Pauken, M.; Wilson, C.

    2017-11-01

    SAEVe is a small Venus lander concept selected for further study by the PSDS3 call. SAEVe is an innovative approach to achieving Venus surface science by exploiting recent developments in high temperature electronics and unique operations scheme.

  6. The Search for Another Earth – Part II

    Indian Academy of Sciences (India)

    density of the planet which in turn determines whether the planet is rocky or gaseous. Accordingly, in our solar system, we have four kinds of planets : (1) terrestrial or Earth-sized planets such as the Earth and Venus, (2) subterrestrial planets such as Mercury and Mars, (3) giant gas planets such as Jupiter and Saturn, and (4).

  7. A Google Earth Grand Tour of the Terrestrial Planets

    Science.gov (United States)

    De Paor, Declan; Coba, Filis; Burgin, Stephen

    2016-01-01

    Google Earth is a powerful instructional resource for geoscience education. We have extended the virtual globe to include all terrestrial planets. Downloadable Keyhole Markup Language (KML) files (Google Earth's scripting language) associated with this paper include lessons about Mercury, Venus, the Moon, and Mars. We created "grand…

  8. Winds in the Middle Cloud Deck From the Near-IR Imaging by the Venus Monitoring Camera Onboard Venus Express

    Science.gov (United States)

    Khatuntsev, I. V.; Patsaeva, M. V.; Titov, D. V.; Ignatiev, N. I.; Turin, A. V.; Fedorova, A. A.; Markiewicz, W. J.

    2017-11-01

    For more than 8 years the Venus Monitoring Camera (VMC) onboard the Venus Express orbiter performed continuous imaging of the Venus cloud layer in UV, visible and near-IR filters. We applied the correlation approach to sequences of the near-IR images at 965 nm to track cloud features and determine the wind field in the middle and lower cloud (49-57 km). From the VMC images that spanned from December of 2006 through August of 2013 we derived zonal and meridional components of the wind field. In low-to-middle latitudes (5-65°S) the velocity of the retrograde zonal wind was found to be 68-70 m/s. The meridional wind velocity slowly decreases from peak value of +5.8 ± 1.2 m/s at 15°S to 0 at 65-70°S. The mean meridional speed has a positive sign at 5-65°S suggesting equatorward flow. This result, together with the earlier measurements of the poleward flow at the cloud tops, indicates the presence of a closed Hadley cell in the altitude range 55-65 km. Long-term variations of zonal and meridional velocity components were found during 1,200 Earth days of observation. At 20° ± 5°S the zonal wind speed increases from -67.18 ± 1.81 m/s to -77.30 ± 2.49 m/s. The meridional wind gradually increases from +1.30 ± 1.82 m/s to +8.53 ± 2.14 m/s. Following Bertaux et al. (2016) we attribute this long-term trend to the influence from the surface topography on the dynamical process in the atmosphere via the upward propagation of gravity waves that became apparent in the VMC observations due to slow drift of the Venus Express orbit over Aphrodite Terra.

  9. Extreme Environments Technologies for Probes to Venus and Jupiter

    Science.gov (United States)

    Balint, Tibor S.; Kolawa, Elizabeth A.; Peterson, Craig E.; Cutts, James A.; Belz, Andrea P.

    2007-01-01

    This viewgraph presentation reviews the technologies that are used to mitigate extreme environments for probes at Venus and Jupiter. The contents include: 1) Extreme environments at Venus and Jupiter; 2) In-situ missions to Venus and Jupiter (past/present/future); and 3) Approaches to mitigate conditions of extreme environments for probes with systems architectures and technologies.

  10. Mantle plumes on Venus revisited

    Science.gov (United States)

    Kiefer, Walter S.

    1992-01-01

    The Equatorial Highlands of Venus consist of a series of quasicircular regions of high topography, rising up to about 5 km above the mean planetary radius. These highlands are strongly correlated with positive geoid anomalies, with a peak amplitude of 120 m at Atla Regio. Shield volcanism is observed at Beta, Eistla, Bell, and Atla Regiones and in the Hathor Mons-Innini Mons-Ushas Mons region of the southern hemisphere. Volcanos have also been mapped in Phoebe Regio and flood volcanism is observed in Ovda and Thetis Regiones. Extensional tectonism is also observed in Ovda and Thetis Regiones. Extensional tectonism is also observed in many of these regions. It is now widely accepted that at least Beta, Atla, Eistla, and Bell Regiones are the surface expressions of hot, rising mantel plumes. Upwelling plumes are consistent with both the volcanism and the extensional tectonism observed in these regions. The geoid anomalies and topography of these four regions show considerable variation. Peak geoid anomalies exceed 90 m at Beta and Atla, but are only 40 m at Eistla and 24 m at Bell. Similarly, the peak topography is greater at Beta and Atla than at Eistla and Bell. Such a range of values is not surprising because terrestrial hotspot swells also have a side range of geoid anomalies and topographic uplifts. Kiefer and Hager used cylindrical axisymmetric, steady-state convection calculations to show that mantle plumes can quantitatively account for both the amplitude and the shape of the long-wavelength geoid and topography at Beta and Atla. In these models, most of the topography of these highlands is due to uplift by the vertical normal stress associated with the rising plume. Additional topography may also be present due to crustal thickening by volcanism and crustal thinning by rifting. Smrekar and Phillips have also considered the geoid and topography of plumes on Venus, but they restricted themselves to considering only the geoid-topography ratio and did not

  11. Clementine Observes the Moon, Solar Corona, and Venus

    Science.gov (United States)

    1997-01-01

    In 1994, during its flight, the Clementine spacecraft returned images of the Moon. In addition to the geologic mapping cameras, the Clementine spacecraft also carried two Star Tracker cameras for navigation. These lightweight (0.3 kg) cameras kept the spacecraft on track by constantly observing the positions of stars, reminiscent of the age-old seafaring tradition of sextant/star navigation. These navigation cameras were also to take some spectacular wide angle images of the Moon.In this picture the Moon is seen illuminated solely by light reflected from the Earth--Earthshine! The bright glow on the lunar horizon is caused by light from the solar corona; the sun is just behind the lunar limb. Caught in this image is the planet Venus at the top of the frame.

  12. An astro-comb calibrated solar telescope to search for the radial velocity signature of Venus

    Science.gov (United States)

    Phillips, David F.; Glenday, Alex G.; Dumusque, Xavier; Buchschacher, Nicolas; Cameron, Andrew Collier; Cecconi, Massimo; Charbonneau, David; Cosentino, Rosario; Ghedina, Adriano; Haywood, Raphäelle; Latham, David W.; Li, Chih-Hao; Lodi, Marcello; Lovis, Christophe; Molinari, Emilio; Pepe, Francesco; Sasselov, Dimitar; Szentgyorgyi, Andrew; Udry, Stephane; Walsworth, Ronald L.

    2016-07-01

    We recently demonstrated sub-m/s sensitivity in measuring the radial velocity (RV) between the Earth and Sun using a simple solar telescope feeding the HARPS-N spectrograph at the Italian National Telescope, which is calibrated with a green astro-comb. We are using the solar telescope to characterize the effects of stellar (solar) RV jitter due to activity on the solar surface with the goal of detecting the solar RV signal from Venus, thereby demonstrating the sensitivity of these instruments to detect true Earth-twin exoplanets.

  13. GASN sheets

    International Nuclear Information System (INIS)

    2013-12-01

    This document gathers around 50 detailed sheets which describe and present various aspects, data and information related to the nuclear sector or, more generally to energy. The following items are addressed: natural and artificial radioactive environment, evolution of energy needs in the world, radioactive wastes, which energy for France tomorrow, the consequences in France of the Chernobyl accident, ammunitions containing depleted uranium, processing and recycling of used nuclear fuel, transport of radioactive materials, seismic risk for the basic nuclear installations, radon, the precautionary principle, the issue of low doses, the EPR, the greenhouse effect, the Oklo nuclear reactors, ITER on the way towards fusion reactors, simulation and nuclear deterrence, crisis management in the nuclear field, does nuclear research put a break on the development of renewable energies by monopolizing funding, nuclear safety and security, the plutonium, generation IV reactors, comparison of different modes of electricity production, medical exposure to ionizing radiations, the control of nuclear activities, food preservation by ionization, photovoltaic solar collectors, the Polonium 210, the dismantling of nuclear installations, wind energy, desalination and nuclear reactors, from non-communication to transparency about nuclear safety, the Jules Horowitz reactor, CO 2 capture and storage, hydrogen, solar energy, the radium, the subcontractors of maintenance of the nuclear fleet, biomass, internal radio-contamination, epidemiological studies, submarine nuclear propulsion, sea energy, the Three Mile Island accident, the Chernobyl accident, the Fukushima accident, the nuclear after Fukushima

  14. Transits of Venus and Mercury as muses

    Science.gov (United States)

    Tobin, William

    2013-11-01

    Transits of Venus and Mercury have inspired artistic creation of all kinds. After having been the first to witness a Venusian transit, in 1639, Jeremiah Horrocks expressed his feelings in poetry. Production has subsequently widened to include songs, short stories, novels, novellas, sermons, theatre, film, engravings, paintings, photography, medals, sculpture, stained glass, cartoons, stamps, music, opera, flower arrangements, and food and drink. Transit creations are reviewed, with emphasis on the English- and French-speaking worlds. It is found that transits of Mercury inspire much less creation than those of Venus, despite being much more frequent, and arguably of no less astronomical significance. It is suggested that this is primarily due to the mythological associations of Venus with sex and love, which are more powerful and gripping than Mercury's mythological role as a messenger and protector of traders and thieves. The lesson for those presenting the night sky to the public is that sex sells.

  15. Venus project : experimentation at ENEA`s pilot site

    Energy Technology Data Exchange (ETDEWEB)

    Bargellini, M.L.; Fontana, F. [ENEA, Centro Ricerche Casaccia, Rome (Italy). Dip. Innovazione; Bucci, C.; Ferrara, F.; Sottile, P.A. [GESI s.r.l., Rome (Italy); Niccolai, L.; Scavino, G. [Rome Univ. Sacro Cuore (Italy); Mancini, R.; Levialdi, S. [Rome Univ. La Sapienza (Italy). Dip. di Scienze dell`Informazione

    1996-12-01

    The document describes the ENEA`s (Italian Agency for New Technologies, Energy and the Environment) experience in the Venus Project (Esprit III ). Venus is an advanced visual interface based on icon representation that permits to end-user to inquiry databases. VENUS interfaces to ENEA`s databases: cometa materials Module, Cometa Laboratories Module and European Programs. This report contents the results of the experimentation and of the validation carried out in ENEA`s related to the Venus generations. Moreover, the description of the architecture, the user requirements syntesis and the validation methodology of the VENUS systems have been included.

  16. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Keywords. Earth system model; Greenland; Antarctica; ice sheet; climate dynamics; surface mass balance. Abstract. Elaboration of a modern Earth system model (ESM) requires incorporation of ice sheet dynamics. Coupling of an ice sheet model (ICM) to an AOGCM is complicated by essential differences in spatial and ...

  17. Regional fracture patterns around volcanoes: Possible evidence for volcanic spreading on Venus

    Science.gov (United States)

    López, I.; Lillo, J.; Hansen, V. L.

    2008-06-01

    Magellan data show that the surface of Venus is dominated by volcanic landforms including large flow fields and a wide range of volcanic edifices that occur in different magmatic and tectonic environments. This study presents the results from a comprehensive survey of volcano-rift interaction in the BAT region and its surroundings. We carried out structural mapping of examples where interaction between volcanoes and regional fractures results in a deflection of the fractures around the volcanic features and discuss the nature of the local volcano-related stress fields that might be responsible for the observed variations of the regional fracture systems. We propose that the deflection of the regional fractures around these venusian volcanoes might be related to volcanic spreading, a process recognized as of great importance in the tectonic evolution of volcanoes on Earth and Mars, but not previously described on Venus.

  18. Venus - Volcano With Massive Landslides

    Science.gov (United States)

    1992-01-01

    This Magellan full-resolution mosaic which covers an area 143 by 146 kilometers (89 by 91 miles) is centered at 55 degrees north latitude, 266 degrees east longitude. The bright feature, slightly south of center is interpreted to be a volcano, 15-20 kilometers (9.3 to 12.4 miles) in diameter with a large apron of blocky debris to its right and some smaller aprons to its left. A preferred explanation is that several massive catastrophic landslides dropped down steep slopes and were carried by their momentum out into the smooth, dark lava plains. At the base of the east-facing or largest scallop on the volcano is what appears to be a large block of coherent rock, 8 to 10 kilometers (5 to 6 miles) in length. The similar margin of both the scallop and block and the shape in general is typical of terrestrial slumped blocks (masses of rock which slide and rotate down a slope instead of breaking apart and tumbling). The bright lobe to the south of the volcano may either be a lava flow or finer debris from other landslides. This volcanic feature, characterized by its scalloped flanks is part of a class of volcanoes called scalloped or collapsed domes of which there are more than 80 on Venus. Based on the chute-like shapes of the scallops and the existence of a spectrum of intermediate to well defined examples, it is hypothesized that all of the scallops are remnants of landslides even though the landslide debris is often not visible. Possible explanations for the missing debris are that it may have been covered by lava flows, the debris may have weathered or that the radar may not be recognizing it because the individual blocks are too small

  19. New aspects of plasma sheet dynamics - MHD and kinetic theory

    Directory of Open Access Journals (Sweden)

    H. Wiechen

    Full Text Available Magnetic reconnection is a process of fundamental importance for the dynamics of the Earth's plasma sheet. In this context, the development of thin current sheets in the near-Earth plasma sheet is a topic of special interest because they could be a possible cause of microscopic fluctuations acting as collective non-idealness from a macroscopic point of view. Simulations of the near-Earth plasma sheet including boundary perturbations due to localized inflow through the northern (or southern plasma sheet boundary show developing thin current sheets in the near-Earth plasma sheet about 810 RE tailwards of the Earth. This location is largely independent from the localization of the perturbation. The second part of the paper deals with the problem of the macroscopic non-ideal consequences of microscopic fluctuations. A new model is presented that allows the quantitative calculation of macroscopic non-idealness without considering details of microscopic instabilities or turbulence. This model is only based on the assumption of a strongly fluctuating, mixing dynamics on microscopic scales in phase space. The result of this approach is an expression for anomalous non-idealness formally similar to the Krook resistivity but now describing the macroscopic consequences of collective microscopic fluctuations, not of collisions.

    Key words. Magnetospheric physics (plasma sheet · Space plasma physics (kinetic and MHD theory; magnetic reconnection

  20. Social Media Planning for the June 5, 2012 transit of Venus

    Science.gov (United States)

    Young, C.; Wawro, M.; Cline, T. D.; Schenk, L. C.; Durscher, R.

    2012-12-01

    On June 5, 2012 at sunset on the East Coast of North America and earlier for other parts of the U.S., the planet Venus made its final trek across the face of the sun as seen from Earth until the year 2117! The NASA Goddard Sun-Earth Day and Solar Dynamics Observatory EPO teams developed a social media strategy to support NASAs Transit of Venus event and webcast from Mauna Kea, Hawaii, on June 5, 2012. Our goal was to connect our contacts with a growing and vibrant social media community during all phases of this celestial event! We also wanted to help spread the word about the Transit of Venus by sharing content, facts, videos, images and links about the transit with our networks. Although social media events occurred throughout the world, our strategy was to provide an additional focus on NASA related events in key locations including those events happening in Hawaii, Alaska, and NASA Ames thereby amplifying our outreach efforts while ensuring that a strong connection existed across geographical and cultural borders. We also wanted to provide the public with information that would help them understand the importance of staying connected via social media even if viewing the transit was possible from their own locations. The social media strategy and the transit of Venus events were a great success and well as a learning experience for future social media events. We present the results of our plan as well as ways to improve and expand for future events. In addition, we present our social media template developed for the transit and now used by other heliophysics EPO teams.

  1. Practical Observations of the Transit of Venus

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 9; Issue 5. Practical Observations of the Transit of Venus. B S Shyalaja. Classroom Volume 9 Issue 5 May 2004 pp 79-83. Fulltext. Click here to view fulltext PDF. Permanent link: https://www.ias.ac.in/article/fulltext/reso/009/05/0079-0083 ...

  2. Venus Clouds: A dirty hydrochloric acid model

    Science.gov (United States)

    Hapke, B.

    1971-01-01

    The spectral and polarization data for Venus are consistent with micron-sized, aerosol cloud particles of hydrochloric acid containing soluble and insoluble iron compounds, whose source could be volcanic or crustal dust. The ultraviolet features could arise from variations in the Fe-HCl concentration in the cloud particles.

  3. Abrir una Venus: Hablar con ella

    Directory of Open Access Journals (Sweden)

    Ginnette Barrantes Sáenz

    2013-09-01

    Se propone a Alicia como la Venus abierta que  incita, mediante  la  cita cinematográfica del cine mudo en el cine de Almodóvar, la no tan conocida figura de  amar a una  dormida( Allouch, 2005

  4. Tidal constraints on the interior of Venus

    Science.gov (United States)

    Dumoulin, C.; Tobie, G.; Verhoeven, O.; Rosenblatt, P.; Rambaux, N.

    2017-12-01

    As a prospective study for a future exploration of Venus, we compute the tidal response of Venus' interior assuming various mantle compositions and temperature profiles representative of different scenarios of Venus' formation and evolution. The mantle density and seismic velocities are modeled from thermodynamical equilibria of mantle minerals and used to predict the moment of inertia, Love numbers, and tide-induced phase lag characterizing the signature of the internal structure in the gravity field. The viscoelasticity of the mantle is parameterized using an Andrade rheology. From the models considered here, the moment of inertia lies in the range of 0.327 to 0.342, corresponding to a core radius of 2900 to 3450 km. Viscoelasticity of the mantle strongly increases the potential Love number relative to previously published elastic models. Due to the anelasticity effects, we show that the possibility of a completely solid metal core inside Venus cannot be ruled out based on the available estimate of k2 from the Magellan mission (Konopliv and Yoder, 1996). A Love number k2 lower than 0.27 would indicate the presence of a fully solid iron core, while for larger values, solutions with an entirely or partially liquid core are possible. Precise determination of the Love numbers, k2 and h2, together with an estimate of the tidal phase lag, are required to determine the state and size of the core, as well as the composition and viscosity of the mantle.

  5. Venus: No Breaks from an Extended Childhood

    Science.gov (United States)

    Moore, W. B.; Kankanamge, D. G. J.

    2017-05-01

    High surface temperatures lead to lower heat flow and lower stress as planets transition out of the heat-pipe mode into subsolidus convection. This causes Venus to miss the window for plate tectonics due to an extended heat-pipe childhood.

  6. Sulfuric acid in the Venus clouds.

    Science.gov (United States)

    Sill, G. T.

    1972-01-01

    The extremely dry nature of the Venus upper atmosphere appears to demand the presence of an efficient desiccating agent as the chief constituent of the clouds of Venus. On the basis of polarization measures it is to be expected that this substance is present as spherical droplets, 1 to 2 microns in diameter, with a refractive index n of 1.46 plus or minus 0.02 at 3500A in the observed region of the atmosphere, with T about equal to 235 K. This substance must have ultraviolet, visible, and infrared reflection properties not inconsistent with the observed spectrum of Venus. Sulfuric acid, of about 86% by weight composition, roughly fulfills the first of these properties. The visible and ultraviolet transmission features of a thin layer of elemental bromine and hydrobromic acid dissolved in sulfuric acid somewhat resemble the Venus spectrum, up to 14 microns. The chemical process postulated for forming sulfuric acid involves the oxidation of sulfur and its compounds to sulfuric acid through the agency of elemental bromine produced by the photolytic decomposition of hydrogen bromide.

  7. Venus Global Reference Atmospheric Model Status and Planned Updates

    Science.gov (United States)

    Justh, H. L.; Cianciolol, A. M. Dwyer

    2017-01-01

    The Venus Global Reference Atmospheric Model (Venus-GRAM) was originally developed in 2004 under funding from NASA's In Space Propulsion (ISP) Aerocapture Project to support mission studies at the planet. Many proposals, including NASA New Frontiers and Discovery, as well as other studies have used Venus-GRAM to design missions and assess system robustness. After Venus-GRAM's release in 2005, several missions to Venus have generated a wealth of additional atmospheric data, yet few model updates have been made to Venus-GRAM. This paper serves to address three areas: (1) to present the current status of Venus-GRAM, (2) to identify new sources of data and other upgrades that need to be incorporated to maintain Venus-GRAM credibility and (3) to identify additional Venus-GRAM options and features that could be included to increase its capability. This effort will de-pend on understanding the needs of the user community, obtaining new modeling data and establishing a dedicated funding source to support continual up-grades. This paper is intended to initiate discussion that can result in an upgraded and validated Venus-GRAM being available to future studies and NASA proposals.

  8. Feasibility of generating a useful laser-induced breakdown spectroscopy plasma on rocks at high pressure: preliminary study for a Venus mission

    International Nuclear Information System (INIS)

    Arp, Zane A.; Cremers, David A.; Harris, Ronny D.; Oschwald, David M.; Parker, Gary R.; Wayne, David M.

    2004-01-01

    Laser-induced breakdown spectroscopy (LIBS) is being developed for future use on landers and rovers to Mars. The method also has potential for use on probes to other planets, the Moon, asteroids and comets. Like Mars, Venus is of strong interest because of its proximity to earth, but unlike Mars, conditions at the surface are far more hostile with temperatures in excess of 700 K and pressures on the order of 9.1 MPa (90 atm). These conditions present a significant challenge to spacecraft design and demand that rapid methods of chemical data gathering be implemented. The advantages of LIBS (e.g. stand-off and very rapid analysis) make the method particularly attractive for Venus exploration because of the expected short operational lifetimes (∼2 h) of surface instrumentation. Although the high temperature of Venus should pose no problem to the analytical capabilities of the LIBS spark, the demonstrated strong dependence of laser plasma characteristics on ambient gas pressures below earth atmospheric pressure requires that LIBS measurements be evaluated at the high Venus surface pressures. Here, we present a preliminary investigation of LIBS at 9.1 MPa for application to the analysis of a basalt rock sample. The results suggest the feasibility of the method for a Venus surface probe and that further study is justified

  9. Scene From The Birth Of Venus: Kajian Karya Fotografi

    Directory of Open Access Journals (Sweden)

    Agra Locita

    2016-01-01

    Full Text Available Scene From The Birth Of Venus is a photographic artwork that created in 1949. The artwork was the result of collaboration between Salvador Dali and two photographers, Baron George Hoyningen-Huene and George Platt Lynes. They created Birth of Venus differently with first painting whom created by Bottocelli Sandro. He depicted the goddess Venus graceful and shy, but it recreated by Salvador Dali in an imaginative photographic artwork. In Scene From The Birth Of Venus, the goddess Venus depicted as half human and fish. Two creations in different way but still in the birth of the goddess Venus theme.  Key words: photography, painting, imaginative

  10. Greenland ice sheet mass balance: a review

    DEFF Research Database (Denmark)

    Khan, Shfaqat Abbas; Aschwanden, Andy; Bjørk, Anders A.

    2015-01-01

    Over the past quarter of a century the Arctic has warmed more than any other region on Earth, causing a profound impact on the Greenland ice sheet (GrIS) and its contribution to the rise in global sea level. The loss of ice can be partitioned into processes related to surface mass balance...... realistic future sea-level changes....

  11. Cholera Fact Sheet

    Science.gov (United States)

    ... sheets Fact files Questions & answers Features Multimedia Contacts Cholera Fact sheet Updated December 2017 Key facts Cholera ... behaviour and to the control of cholera. Oral cholera vaccines Currently there are three WHO pre-qualified ...

  12. MEETING VENUS. A Collection of Papers presented at the Venus Transit Conference Tromsoe 2012

    Science.gov (United States)

    Sterken, Christiaan; Aspaas, Per Pippin

    2013-05-01

    On 2-3 June 2012, the University of Tromsoe hosted a conference about the cultural and scientific history of the transits of Venus. The conference took place in Tromsoe for two very specific reasons. First and foremost, the last transit of Venus of this century lent itself to be observed on the disc of the Midnight Sun in this part of Europe during the night of 5 to 6 June 2012. Second, several Venus transit expeditions in this region were central in the global enterprise of measuring the scale of the solar system in the eighteenth century. The site of the conference was the Nordnorsk Vitensenter (Science Centre of Northern Norway), which is located at the campus of the University of Tromsoe. After the conference, participants were invited to either stay in Tromsoe until the midnight of 5-6 June, or take part in a Venus transit voyage in Finnmark, during which the historical sites Vardoe, Hammerfest, and the North Cape were to be visited. The post-conference program culminated with the participants observing the transit of Venus in or near Tromsoe, Vardoe and even from a plane near Alta. These Proceedings contain a selection of the lectures delivered on 2-3 June 2012, and also a narrative description of the transit viewing from Tromsoe, Vardoe and Alta. The title of the book, Meeting Venus, refers the title of a play by the Hungarian film director, screenwriter and opera director Istvan Szabo (1938-). The autobiographical movie Meeting Venus (1991) directed by him is based on his experience directing Tannhauser at the Paris Opera in 1984. The movie brings the story of an imaginary international opera company that encounters a never ending series of difficulties and pitfalls that symbolise the challenges of any multicultural and international endeavour. As is evident from the many papers presented in this book, Meeting Venus not only contains the epic tales of the transits of the seventeenth, eighteenth and nineteenth centuries, it also covers the conference

  13. The Venus Emissivity Mapper - gaining a global perspective on the surface composition of Venus

    Science.gov (United States)

    Helbert, Joern; Dyar, Melinda; Widemann, Thomas; Marcq, Emmanuel; Maturilli, Alessandro; Mueller, Nils; Kappel, David; Ferrari, Sabrina; D'Amore, Mario; Tsang, Constantine; Arnold, Gabriele; Smrekar, Suzanne; VEM Team

    2017-10-01

    The permanent cloud cover of Venus prohibits observations of the surface with traditional imaging techniques over much of the EM spectral range, leading to the false notion that information about the composition of Venus’ surface could only be derived from lander missions. However, harsh environmental conditions on the surface cause landed missions to be sole site, highly complex, and riskier than orbiting missions.It is now known that 5 transparency windows occur in the Venus atmosphere, ranging from 0.86 µm to 1.18 µm. Recent advances in high temperature laboratory spectroscopy at the PSL at DLR these windows are highly diagnostic for surface mineralogy. Mapping of the southern hemisphere of Venus with VIRTIS on VEX in the 1.02 µm band was a proof-of-concept for an orbital remote sensing approach to surface composition and weathering studies[1-3]. The Venus Emissivity Mapper [4] proposed for the NASA’s Venus Origins Explorer (VOX) and the ESA EnVision proposal builds on these recent advances. It is the first flight instrument specially designed with a sole focus on mapping the surface of Venus using the narrow atmospheric windows around 1 µm. Operating in situ from Venus orbit, VEM will provide a global map of surface composition as well as redox state of the surface, providing a comprehensive picture of surface-atmosphere interaction and support for landing site selection. Continuous observation of the thermal emission of the Venus will provide tight constraints on the current day volcanic activity[5]. This is complemented by measurements of atmospheric water vapor abundance as well as cloud microphysics and dynamics. These data will allow for accurate correction of atmospheric interference on the surface measurements, which provide highly valuable science on their own. A mission combining VEM with a high-resolution radar mapper such as VOX or EnVision in a low circular orbit will provide key insights into the divergent evolution of Venus.1. Smrekar, S

  14. The escape of natural satellites from Mercury and Venus

    International Nuclear Information System (INIS)

    Kumar, S.S.

    1977-01-01

    It is suggested that the slow rotations of Mercury and Venus may be connected with the absence of natural satellites around them. If Mercury or Venus possessed a satellite at the time of formation, the tidal evolution would have caused the satellite to recede. At a sufficiently large distance from the planet, the Sun's gravitational influence makes the satellite orbit unstable. The natural satellites of Mercury and Venus might have escaped as a consequence of this instability. (Auth.)

  15. Venus, Mars, and the ices on Mercury and the moon: astrobiological implications and proposed mission designs.

    Science.gov (United States)

    Schulze-Makuch, Dirk; Dohm, James M; Fairén, Alberto G; Baker, Victor R; Fink, Wolfgang; Strom, Robert G

    2005-12-01

    Venus and Mars likely had liquid water bodies on their surface early in the Solar System history. The surfaces of Venus and Mars are presently not a suitable habitat for life, but reservoirs of liquid water remain in the atmosphere of Venus and the subsurface of Mars, and with it also the possibility of microbial life. Microbial organisms may have adapted to live in these ecological niches by the evolutionary force of directional selection. Missions to our neighboring planets should therefore be planned to explore these potentially life-containing refuges and return samples for analysis. Sample return missions should also include ice samples from Mercury and the Moon, which may contain information about the biogenic material that catalyzed the early evolution of life on Earth (or elsewhere). To obtain such information, science-driven exploration is necessary through varying degrees of mission operation autonomy. A hierarchical mission design is envisioned that includes spaceborne (orbital), atmosphere (airborne), surface (mobile such as rover and stationary such as lander or sensor), and subsurface (e.g., ground-penetrating radar, drilling, etc.) agents working in concert to allow for sufficient mission safety and redundancy, to perform extensive and challenging reconnaissance, and to lead to a thorough search for evidence of life and habitability.

  16. Magma reservoirs and neutral buoyancy zones on Venus - Implications for the formation and evolution of volcanic landforms

    Science.gov (United States)

    Head, James W.; Wilson, Lionel

    1992-01-01

    The production of magma reservoirs and neutral buoyancy zones (NBZs) on Venus and the implications of their development for the formation and evolution of volcanic landforms are examined. The high atmospheric pressure on Venus reduces volatile exsolution and generally serves to inhibit the formation of NBZs and shallow magma reservoirs. For a range of common terrestrial magma-volatile contents, magma ascending and erupting near or below mean planetary radius (MPR) should not stall at shallow magma reservoirs; such eruptions are characterized by relatively high total volumes and effusion rates. For the same range of volatile contents at 2 km above MPR, about half of the cases result in the direct ascent of magma to the surface and half in the production of neutral buoyancy zones. NBZs and shallow magma reservoirs begin to appear as gas content increases and are nominally shallower on Venus than on earth. For a fixed volatile content, NBZs become deeper with increasing elevation: over the range of elevations treated in this study (-1 km to +4.4 km) depths differ by a factor of 2-4. Factors that may account for the low height of volcanoes on Venus are discussed.

  17. HIGH-RESOLUTION SATELLITE IMAGING OF THE 2004 TRANSIT OF VENUS AND ASYMMETRIES IN THE CYTHEREAN ATMOSPHERE

    International Nuclear Information System (INIS)

    Pasachoff, Jay M.; Schneider, Glenn; Widemann, Thomas

    2011-01-01

    This paper presents the only space-borne optical-imaging observations of the 2004 June 8 transit of Venus, the first such transit visible from Earth since AD 1882. The high-resolution, high-cadence satellite images we arranged from NASA's Transition Region and Coronal Explorer (TRACE) reveal the onset of visibility of Venus's atmosphere and give further information about the black-drop effect, whose causes we previously demonstrated from TRACE observations of a transit of Mercury. The atmosphere is gradually revealed before second contact and after third contact, resulting from the changing depth of atmospheric layers refracting the photospheric surface into the observer's direction. We use Venus Express observations to relate the atmospheric arcs seen during the transit to the atmospheric structure of Venus. Finally, we relate the transit images to current and future exoplanet observations, providing a sort of ground truth showing an analog in our solar system to effects observable only with light curves in other solar systems with the Kepler and CoRoT missions and ground-based exoplanet-transit observations.

  18. Venus y el fin del mundo

    Directory of Open Access Journals (Sweden)

    Gonzalo Munévar

    2006-01-01

    Full Text Available Este artículo busca demostrar que los argumentos generales acerca de la exploración científica valen también para las ciencias espaciales. El trabajo se basa en el ejemplo de la exploración de Venus y lo que esta nos dice acerca de nuestro propio planeta. Argumenta que el concepto de la probabilidad de Leslie es incorrecto, como también lo son las dudas sobre la evidencia Venusiana. Así mismo, concluye que no se puede rechazar la importancia que tienen los descubrimientos inesperados que han resultado de la exploración de Venus para ayudarnos a comprender nuestro propio planeta. Y que si van a ser rechazados estos descubrimientos debe ser por razones científicas, no por intuiciones acerca de la probabilidad.

  19. On the Ionospheric Holes of Venus

    Science.gov (United States)

    Collinson, G.; Fedorov, A.; Futaana, Y.; Masunaga, K.; Hartle, R. E.; Stenberg, G.; Budnik, E.; Grebowsky, J. M.; Holmstrom, M.; andre, N.; Barabash, S. V.; Zhang, T.

    2013-12-01

    One of the most intriguing unsolved mysteries that endures from the Pioneer Venus Orbiter is that of ~1000km wide ``Holes" in the nightside Ionosphere. The phenomena remains unexplained, despite their frequent observation during the first three years of the mission, and more than thirty years having elapsed since their first description in the literature. We present new observations by the ESA Venus Express of Ionospheric Holes at very high altitudes, providing us with the opportunity to study this fascinating phenomena with modern instrumentation. We discuss the insight that these new data give us into the effect of Ionospheric Holes on atmospheric escape, and the evidence that suggests that Ionospheric Holes are due to an internal planetary magnetic field.

  20. The cartography of Venus with Magellan data

    Science.gov (United States)

    Kirk, R. L.; Morgan, H. F.; Russell, J. F.

    1993-01-01

    Maps of Venus based on Magellan data are being compiled at 1:50,000,000, 1:5,000,000 and 1:1,500,000 scales. Topographic contour lines based on radar altimetry data are overprinted on the image maps, along with feature nomenclature. Map controls are based on existing knowledge of the spacecraft orbit; photogrammetric triangulation, a traditional basis for geodetic control for bodies where framing cameras were used, is not feasible with the radar images of Venus. Preliminary synthetic aperture radar (SAR) image maps have some data gaps and cosmetic inconsistencies, which will be corrected on final compilations. Eventual revision of geodetic controls and of the adopted Venusian spin-axis location will result in geometric adjustments, particularly on large-scale maps.

  1. Venus clouds - A dirty hydrochloric acid model.

    Science.gov (United States)

    Hapke, B.

    1972-01-01

    The spectral and polarization data for Venus are consistent with micrometer-sized aerosol cloud particles of hydrochloric acid with soluble and insoluble iron compounds, whose source could be volcanic or crustal dust. The yellow color of the clouds could be due to absorption bands in the near UV involving ferric iron and chlorine complexes. It is pointed out that the UV features could arise from variations in the concentrations of iron and hydrochloric acid in the cloud particles.

  2. Energetics of the dayside ionosphere of Venus

    Science.gov (United States)

    Dobe, Zoltan; Nagy, Andrew F.; Brace, Larry H.; Cravens, Thomas E.; Luhmann, Janet G.

    1993-01-01

    A reanalysis of the Pioneer Venus electron temperature data base showed a strong correlation between elevated electron temperatures and induced magnetic fields in the dayside ionosphere above about 200 km. These results suggest, although not conclusively, that the elevated temperatures are the result of reduced vertical conductivities caused by the horizontal, induced fields with a possible contribution from energy deposition by magnetosheath electrons moving along the field from the tail region.

  3. Present Status of Janaese Venus Climate Orbiter

    Science.gov (United States)

    Nakamura, M.; Imamura, T.; Ishii, N.; Satoh, T.; Abe, T.; Ueno, M.; Suzuki, M.; Yamazaki, A.

    2007-08-01

    The start of the Japanese Venus Exploration program was in 2001, and last year (2006) we moved it to Phase C after PDR in August.We would like to report the present status of our Venus Climate Orbiter. Planet-C is the project name in ISAS/JAXA. The launch vehicle is changed from M-V to H-IIA. It will be launched from Tanegashima Space Center (TNSC) in Kagoshima. With this modification, we changed some minor design of the spacecraft and the total weight is slightly heavier than before, but the basic design has not been modified. The launch window will be kept in summer in 2010 and it will arrive at Venus in December 2010. The spacecraft will be directly put into the interplanetary orbit. Now we are preparing the Mechanical and Thermal engineering Model (MTM) which will end in middle of 2007 and will shake it and do the thermal vacuum test. Later this model will be modified to the flight model and the final integration test will be in 2009 which takes 1 year. Development of all the science instruments are going well. The first integration test of science instruments will be in August this year. We can report the results of it in the meeting.

  4. O+ pickup ions outside of Venus' bow shock: Venus Express observations

    Science.gov (United States)

    Wei, Yong; Fraenz, Markus; Dubinin, Eduard; Zhang, Tielong; Jarvinen, Riku; Wan, Weixing; Kallio, Esa; Collinson, Glyn; Barabash, Stars; Norbert, Krupp; Woch, Joachim; Lundin, Rickard; delva, Magda

    2013-04-01

    Pickup ions are ions of planetary origin that become assimilated into the solar wind flow through their interaction with the solar wind magnetic and electric field. The speed of pickup ions varies between zero and twice the underlying plasma flow component perpendicular to magnetic field vector. For the unmagnetized planet Venus and Mars, oxygen (O+) pickup ions are known to be important because they can modify the global configuration of planetary plasma environment and significantly contribute to the atmospheric O+ loss [1]. Since the kinetic energy of an O+ pickup ion can reach 64 times that of a co-moving proton, an instrument must be able to measure O+ ions with energy of at least tens of keV to investigate the O+ pickup ion distribution from planetary ionosphere to solar wind. The in-situ observations and simulations at Mars have shown that the energy of O+ pickup ions can be 55-72 keV outside of the bow shock [2]. For Venus case, the plasma analyzer (OPA) onboard Pioneer Venus Orbiter (PVO), which was designed for solar wind monitoring, has an 8 keV energy limit for O+ detection and the limited sampling and data rate [3]. Therefore, OPA can only measure the O+ pickup ions in the sheath flow or inside the induced magnetosphere where the speed of ambient plasma flow is significantly lower than that of the unshocked solar wind outside of the bow shock. In addition, Galileo also did not capture O+ outside bowshock during its 1-hour Venus flyby though its plasma instrument had ability to cover the energy band of O+ pickup ions [4]. The Ion Mass Analyzer (IMA), included in the Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) package on board Venus Express (VEX), determines the composition, energy, and angular distribution of ions in the energy range ~10 eV/q to 30 keV/q. Note that an O+ ion moving at the typical solar wind speed 400 km/s has kinetic energy 13.4 keV. Therefore, IMA has ability to measure the O+ pickup ions outside of Venus' bow shock. We

  5. Venus Express uurib Maa kurja kaksikut / ref. Triin Thalheim

    Index Scriptorium Estoniae

    2005-01-01

    9. novembril startis Baikonuri kosmodroomilt Veenusele Euroopa Kosmoseagentuuri sond Venus Express, mis peaks planeedi atmosfääri sisenema aprillis. Teadlaste sõnul peab sondi saadetav info aitama mõista naaberplaneedi kliimat ja atmosfääri ning tooma selgust, kas Maa võib kunagi Veenuse sarnaseks muutuda. Lisaks joonis: Venus Express

  6. Venus 2004: east and west elongations and solar transit

    Science.gov (United States)

    McKim, R. J.; Blaxall, K.; Heath, A.

    2007-04-01

    The year 2004 was exceptional in producing the first solar transit of Venus since the late Victorian era. The bright aureole and atmospheric ring were re-observed, and the entire phenomenon was witnessed for the first time ever in hydrogen alpha light. Although routine observations throughout 2004 were unexceptional, patterns of visibility of bright and dark markings, cusp extensions and cusp-caps were recorded. No correlation was found between the latitude of the sub-Earth point and the visibility of either cusp-cap, with the S. cap predominating for most of the year. It was possible to accurately follow individual ultraviolet dark markings over many consecutive rotations, extending from the E. to W. elongations, and thereby to make a current measurement of the synodic atmospheric rotation period for the near-equatorial features: 3.996 ± 0.001 days. The true Ashen Light was reported visually on only a few occasions, but these correspond closely to times when infrared emission from the surface of the dark side was recorded in 1-micron waveband images. Some of the stable dark side albedo features were also visible upon the 1-micron images, and have been tentatively identified with known surface features. Infrared imaging at the same waveband showed little detail on the sunlit disk, but a few bright spots were sufficiently well observed to suggest a synodic rotation period close to 5.0 days, not atypical for the lower cloud decks.

  7. Bilateral topographic symmetry patterns across Aphrodite Terra, Venus

    International Nuclear Information System (INIS)

    Crumpler, L.S.; Head, J.W.

    1988-01-01

    Western Aphrodite Terra, Venus, is characterized by a series of parallel linear structural discontinuities 2000--4000 km in length and 100--200 km wide, which strike at high angles to the general topographic trend of the Aphrodite Terra highlands. The broad chracteristics of the cross-strike discontinuities (CSDs) are similar to both strike-slip fault zones and terrestrial oceanic fracture zones. In an effort to distinguish between these two hypotheses, topographic profiles were taken across Aphrodite Terra to test for bilateral symmetry of the type associated with thermal boundary layer topography at divergent plate boundaries on Earth. In addition to a broad bilateral symmetry at a range of angles across Aphrodite Terra, detailed bilateral symmetry is observed within domains between linear discontinuities in directions generally parallel to the strike of the discontinuities. In addition, within a domain the centers of symmetry of several profiles define a linear rise crest that is oriented normal to the bounding CSDs and terminates against them

  8. Chinese records of the 1874 transit of Venus

    Science.gov (United States)

    Lu, Lingfeng; Li, Huifang

    2013-03-01

    Before the advent of radar, transits of Venus were very important for measuring the distance between the Earth and the Sun. A transit occurred in 1874, and was visible from China, other parts of east and southeast Asia and from India, Australia and New Zealand and certain islands in the Indian and Pacific Oceans. As a result, many astronomers from Western countries came to China to observe it. According to traditional Chinese astrology, the Sun represented the Emperor, and if the Sun was invaded by other astronomical bodies it meant that the Emperor and the country faced some ominous disaster. In the late nineteenth century, Western astronomical knowledge was widely translated into Chinese and spread among Chinese intellectuals, so the 1874 transit supposedly was easily understood by Chinese intellectuals. Before the transit took place, various Chinese publications introduced this kind of celestial event as science news, but at the same time other influential newspapers and journals discussed the astrological connection between the transit and the fortunes of the nation. In this paper we review these interesting Chinese records and discuss the different attitudes towards the transit exhibited by Chinese intellectuals and officials, during a period when Western learning was being widely disseminated throughout China.

  9. Venus surface peeking through the atmosphere - gaining a global perspective on the surface composition through near infrared observations

    Science.gov (United States)

    Helbert, J.; Dyar, M. D.; Maturilli, A.; D'Amore, M.; Ferrari, S.; Mueller, N. T.; Smrekar, S. E.

    2017-12-01

    Venus is the most Earth-like of the terrestrial planets, though very little is known about its surface composition. Thanks to recent advances in laboratory spectroscopy and spectral analysis techniques, this is about to change. Although the atmosphere prohibits observations of the surface with traditional imaging techniques over much of the EM spectral range, five transparent windows between 0.86 µm and 1.18 µm occur in the atmosphere's CO2 spectrum. New high temperature laboratory spectra from the Planetary Spectroscopy Laboratory at DLR show that spectra in these windows are highly diagnostic for surface mineralogy [1]. The Venus Emissivity Mapper (VEM) [2] builds on these recent advances. It is proposed for NASA's Venus Origins Explorer where a radar will provided the needed high-resolution altimetry and ESA's EnVision would provide stereo topography instead. VEM is the first flight instrument specially designed to focus solely on mapping Venus' surface using the windows around 1 µm. Operating in situ from Venus orbit, VEM will provide a global map of composition as well as redox state of the surface, enabling a comprehensive picture of surface-atmosphere interaction on Venus. VEM will return a complex data set containing surface, atmospheric, cloud, and scattering information. Total planned data volume for a typical mission scenario exceeds 1TB. Classical analysis techniques have been successfully used for VIRTIS on Venus Express [3-5] and could be employed with the VEM data. However, application of machine learning approaches to this rich dataset is vastly more efficient, as has already been confirmed with laboratory data. Binary classifiers [6] demonstrate that at current best estimate errors, basalt spectra are confidently discriminated from basaltic andesites, andesites, and rhyolite/granite. Applying the approach of self-organizing maps to the increasingly large set of laboratory measurements allows searching for additional mineralogical indicators

  10. Low-frequency magnetic field fluctuations in Venus' solar wind interaction region: Venus Express observations

    Directory of Open Access Journals (Sweden)

    L. Guicking

    2010-04-01

    Full Text Available We investigate wave properties of low-frequency magnetic field fluctuations in Venus' solar wind interaction region based on the measurements made on board the Venus Express spacecraft. The orbit geometry is very suitable to investigate the fluctuations in Venus' low-altitude magnetosheath and mid-magnetotail and provides an opportunity for a comparative study of low-frequency waves at Venus and Mars. The spatial distributions of the wave properties, in particular in the dayside and nightside magnetosheath as well as in the tail and mantle region, are similar to observations at Mars. As both planets do not have a global magnetic field, the interaction process of the solar wind with both planets is similar and leads to similar instabilities and wave structures. We focus on the spatial distribution of the wave intensity of the fluctuating magnetic field and detect an enhancement of the intensity in the dayside magnetosheath and a strong decrease towards the terminator. For a detailed investigation of the intensity distribution we adopt an analytical streamline model to describe the plasma flow around Venus. This allows displaying the evolution of the intensity along different streamlines. It is assumed that the waves are generated in the vicinity of the bow shock and are convected downstream with the turbulent magnetosheath flow. However, neither the different Mach numbers upstream and downstream of the bow shock, nor the variation of the cross sectional area and the flow velocity along the streamlines play probably an important role in order to explain the observed concentration of wave intensity in the dayside magnetosheath and the decay towards the nightside magnetosheath. But, the concept of freely evolving or decaying turbulence is in good qualitative agreement with the observations, as we observe a power law decay of the intensity along the streamlines. The observations support the assumption of wave convection through the magnetosheath, but

  11. Venus Surface Composition Constrained by Observation and Experiment

    Science.gov (United States)

    Gilmore, Martha; Treiman, Allan; Helbert, Jörn; Smrekar, Suzanne

    2017-11-01

    New observations from the Venus Express spacecraft as well as theoretical and experimental investigation of Venus analogue materials have advanced our understanding of the petrology of Venus melts and the mineralogy of rocks on the surface. The VIRTIS instrument aboard Venus Express provided a map of the southern hemisphere of Venus at ˜1 μm allowing, for the first time, the definition of surface units in terms of their 1 μm emissivity and derived mineralogy. Tessera terrain has lower emissivity than the presumably basaltic plains, consistent with a more silica-rich or felsic mineralogy. Thermodynamic modeling and experimental production of melts with Venera and Vega starting compositions predict derivative melts that range from mafic to felsic. Large volumes of felsic melts require water and may link the formation of tesserae to the presence of a Venus ocean. Low emissivity rocks may also be produced by atmosphere-surface weathering reactions unlike those seen presently. High 1 μm emissivity values correlate to stratigraphically recent flows and have been used with theoretical and experimental predictions of basalt weathering to identify regions of recent volcanism. The timescale of this volcanism is currently constrained by the weathering of magnetite (higher emissivity) in fresh basalts to hematite (lower emissivity) in Venus' oxidizing environment. Recent volcanism is corroborated by transient thermal anomalies identified by the VMC instrument aboard Venus Express. The interpretation of all emissivity data depends critically on understanding the composition of surface materials, kinetics of rock weathering and their measurement under Venus conditions. Extended theoretical studies, continued analysis of earlier spacecraft results, new atmospheric data, and measurements of mineral stability under Venus conditions have improved our understanding atmosphere-surface interactions. The calcite-wollastonite CO2 buffer has been discounted due, among other things, to

  12. Sun-Earth Day Connects History, Culture and Science

    Science.gov (United States)

    Cline, T.; Thieman, J.

    2003-12-01

    The NASA Sun-Earth Connection Education forum annually promotes and event called Sun-Earth Day: a national celebration of the Sun, the space around the Earth (geospace), and how all of it affects life on our planet. For the past 3 years this event has provided a venue by which classrooms, museums, planetaria, and at NASA centers have had a sensational time sharing stories, images, and activities related to the Sun-Earth connections and the views o fthe Sun from Earth. Each year we select a different theme by which NASA Space Science can be further related to cross-curricular activities. Sun-Earth Day 2002, "Celebrate the Equinox", drew parallels between Native American Cultures and NASA's Sun-Earth Connection research via cultural stories, interviews, web links, activities and Native American participation. Sun-Earth Day 2003, "Live From the Aurora", shared the beauty of the Aurora through a variety of activities and stories related to perspectives of Northern Peoples. Sun-Earth Day 2004 will share the excitement of the transit of Venus through comparisons of Venus with Earth and Mars, calculations of the distances to nearby stars, and the use of transits to identify extra-solar planets. Finally, Sun-Earth Day 2005 will bring several of these themes together by turning our focus to the history and culture surrounding ancient observatories such as Chaco Canyon, Machu Picchu, and Chichen Itza.

  13. Structural evolution of western Fortuna Tessera, Venus

    Science.gov (United States)

    Pritchard, M. E.; Hansen, V. L.; Willis, J. J.

    1997-09-01

    Western Fortuna Tessera, Ishtar Terra, records polyphase deformation. Structures include: ribbons forming long, narrow, steep-sided troughs that reflect surface layer extension; N-trending folds related to Maxwell Montes deformation; short, wide, NW-trending graben that reflect late local extension; and, within the southwestern map area, gentle, E-trending warps, which postdate ribbon structures. Flood lava flows postdate deformation. Ribbon structures change orientation radially from NNE to WNW. These observations caution against the correlation of Fortuna Tessera with tessera elsewhere on Venus and against the proposal that tessera forms a global stratigraphic layer.

  14. Venus gravity - Analysis of Beta Regio

    Science.gov (United States)

    Esposito, P. B.; Sjogren, W. L.; Mottinger, N. A.; Bills, B. G.; Abbott, E.

    1982-01-01

    Radio tracking data acquired over Beta Regio were analyzed to obtain a surface mass distribution from which a detailed vertical gravity field was derived. In addition, a corresponding vertical gravity field was evaluated solely from the topography of the Beta region. A comparison of these two maps confirms the strong correlation between gravity and topography which was previously seen in line-of-sight gravity maps. It also demonstrates that the observed gravity is a significant fraction of that predicted from the topography alone. The effective depth of complete isostatic compensation for the Beta region is estimated to be 330 km, which is somewhat deeper than that found for other areas of Venus.

  15. Analysis of VENUS-3 benchmark experiment

    International Nuclear Information System (INIS)

    Kodeli, I.; Sartori, E.

    1998-01-01

    The paper presents the revision and the analysis of VENUS-3 benchmark experiment performed at CEN/SCK, Mol (Belgium). This benchmark was found to be particularly suitable for validation of current calculation tools like 3-D neutron transport codes, and in particular of the 3D sensitivity and uncertainty analysis code developed within the EFF project. The compilation of the integral experiment was integrated into the SINBAD electronic data base for storing and retrieving information about the shielding experiments for nuclear systems. SINBAD now includes 33 reviewed benchmark descriptions and several compilations waiting for the review, among them many benchmarks relevant for pressure vessel dosimetry system validation.(author)

  16. Dynamics and chemistry of Venus' large and complex cloud system : a science case for an in-situ long-term chemical laboratory

    Science.gov (United States)

    Widemann, Thomas; Määttänen, Anni; Wilquet, Valérie; McGouldrick, Kevin; Jessup, Kandis Lea; Wilson, Colin; Limaye, Sanjay; EuroVenus Consortium, the

    2014-05-01

    The planet Venus is the closest to the planet Earth both geographically and geometrically, with an average solar distance only 0.3AU smaller than that of Earth and an equatorial radius that is only 5% smaller than Earth's. But the similarities appear to end there. How did the environments of Venus and Earth become so divergent? The answer to this question relies upon an understanding of Venus' origins, the nature of its present atmosphere, and the role that the clouds have played in evolution and current state of Venus. Venus' clouds are composed of highly concentrated solutions of sulfuric acid and water. The sulfuric acid is produced photochemically from reactions involving water vapor and various sulfur species such as SO2 in the upper atmosphere around 62 km. The region from 50-60 km altitude is convectively unstable, suggesting that most of the cloud formation here is convectively driven, as are cumulus clouds on Earth but with sulfuric acid taking the place of water as the main condensable species. The clouds of Venus are ubiquitous, play a significant role in the radiative balance of the planet, are used as tracers to probe the atmospheric circulation, and are a key part of a global sulfurohydrological cycle that redistributes key greenhouse gasses such as SO2 and H2O. Thus understanding the clouds of Venus holds the key to understanding how Venus itself came to be the world of extremes that it is today. ESA's Venus Express mission, launched in Nov. 2005, has significantly improved our knowledge about the atmosphere of Venus by providing global long-term remote sensing observations with complete coverage in latitude and local solar time. However major questions remain about key minor species and how they vary throughout the major atmospheric regimes in the upper atmosphere, near the cloud tops where photolysis and condensation processes occur, near the surface where coupling and interchange with the atmosphere occurs, and in the middle atmosphere where they

  17. Geology of the Venus equatorial region from Pioneer Venus radar imaging

    International Nuclear Information System (INIS)

    Senske, D.A.; Head, J.W.

    1989-01-01

    The surface characteristics and morphology of the equatorial region of Venus were first described by Masursky et al. who showed this part of the planet to be characterized by two topographic provinces, rolling plains and highlands, and more recently by Schaber who described and interpreted tectonic zones in the highlands. Using Pioneer Venus (PV) radar image data (15 deg S to 45 deg N), Senske and Head examined the distribution, characteristics, and deposits of individual volcanic features in the equatorial region, and in addition classified major equatorial physiographic and tectonic units on the basis of morphology, topographic signature, and radar properties derived from the PV data. Included in this classification are: plains (undivided), inter-highland tectonic zones, tectonically segmented linear highlands, upland rises, tectonic junctions, dark halo plains, and upland plateaus. In addition to the physiographic units, features interpreted as coronae and volcanic mountains have also been mapped. The latter four of the physiographic units along with features interpreted to be coronae

  18. Geology of the Venus equatorial region from Pioneer Venus radar imaging

    Science.gov (United States)

    Senske, D. A.

    1990-01-01

    The data collected by Pioneer Venus have been used to map the broad radar characteristics of the equatorial region on the basis of radar brightness and texture. Seven units are defined and are used to assess the geologic character of the equatorial region. The correspondence between features in the 15 deg region of overlap between Pioneer Venus ans Venera 15/16 images is examined and used to extend units mapped in the northern high latitudes into the equatorial region. Using the properties of rms slope, reflectivity, the scattering behavior of the surface, and topographic signature, seven physiographic units are mapped on the basis of the distribution of the radar units in the equatorial region and are identified by increasing complexity as plains, dark halo plains, upland rises, upland plateaus, interhighland tectonic zones, tectonically segmented linear highlands, and tectonic junctions. The distribution of larger circular structures interpreted as coronae is also examined.

  19. Experimental reconstruction of Lomonosov's discovery of Venus's atmosphere with antique refractors during the 2012 transit of Venus

    Science.gov (United States)

    Koukarine, A.; Nesterenko, I.; Petrunin, Yu.; Shiltsev, V.

    2013-11-01

    In 1761, the Russian polymath Mikhail Vasilievich Lomonosov (1711-1765) discovered the atmosphere of Venus during its transit over the Sun's disc. In this paper we report on experimental reenactments of Lomonosov's discovery with antique refractors during the transit of Venus June 5-6, 2012. We conclude that Lomonosov's telescope was fully adequate to the task of detecting the arc of light around Venus off the Sun's disc during ingress or egress provided proper experimental techniques as described by Lomonosov in his 1761 report are employed.

  20. Plumes as a Mechanism for Equilibrium Resurfacing of Venus

    Science.gov (United States)

    Hansen, V. L.; Young, D. A.

    2004-03-01

    End member hypotheses catastrophic- and equilibrium-volcanic-resurfacing fall short in addressing Venus' crater database, and both assume crater removal by burial. We propose an alternative hypothesis that includes crater destruction by annealing.

  1. In Situ Partial Melt on Venus: Evidence for Ancient Water?

    Science.gov (United States)

    Hansen, V. L.

    2003-03-01

    Shield terrain comprises countless tiny lava flows that coalesced to form an ultra-thin discontinuous regionally extensive mechanically strong layer; lava represents point-source crustal partial melt and may provide evidence for ancient Venus water.

  2. Venus Preserves a Rare Record of Early Terrestrial Planet Processes

    Science.gov (United States)

    Hansen, V. L.; López, I.

    2009-03-01

    Geologic relations and thermal modeling indicate that ribbon tessera terrain (rtt) records a unique and ancient era of Venus evolution. A new global geologic map of rtt preserves a rare record of early terrestrial planet evolution processes.

  3. Harsh Environment Gas Sensor Array for Venus Atmospheric Measurements Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Makel Engineering and the Ohio State University propose to develop a harsh environment tolerant gas sensor array for atmospheric analysis in future Venus missions....

  4. Sapphire Viewports for a Venus Probe, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed Phase 1 program will demonstrate that sapphire viewports are feasible for use in Venus probes. TvU's commercial viewport products have demonstrated that...

  5. Thermal Insulator for a Venus Lander, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — A lander on the surface of Venus is heated by the 460 C surface temperature, which, even with the best current designs using passive insulation, cause its...

  6. Transit of Venus: Quantitative Observing with Simple Equipment The ...

    Indian Academy of Sciences (India)

    gmail.com. The possibilities of quantitative student observations during the transit of Venus, using simple equipment, are discussed. The equipment could ... These observations could have been by naked eye and the above reference seems to ...

  7. Application of Submerged Grouted Anchors in Sheet Pile Quay Walls

    OpenAIRE

    Mollahasani, Ali

    2014-01-01

    Sheet pile walls are one of the oldest earth retention systems utilized in civil engineering projects. They are used for various purposes; such as excavation support system, cofferdams, cut-off walls under dams, slope stabilization, waterfront structures, and flood walls. Sheet pile walls are one of the most common types of quay walls used in port construction. The worldwide increases in utilization of large ships for transportation have created an urgent need of deepening the seabed within p...

  8. Power System for Venus Surface Exploration

    Science.gov (United States)

    Landis, Geoffrey A.; Mellott, Kenneth

    2002-01-01

    A radioisotope power and cooling system is designed to provide electrical power for a probe operating on the surface of Venus. Most foreseeable electronics devices and sensors cannot operate at the 450 C ambient surface temperature of Venus. Because the mission duration is substantially long and the use of thermal mass to maintain an operable temperature range is likely impractical, some type of active refrigeration may be required to keep electronic components at a temperature below ambient. The fundamental cooling parameters are the cold sink temperature, the hot sink temperature, and the amount of heat to be removed. In this instance, it is anticipated that electronics would have a nominal operating temperature of 300 C. Due to the highly thermal convective nature of the high-density (90 bar CO2) atmosphere, the hot sink temperature was assumed to be 50 C, which provided a 500 C temperature of the cooler's heat rejecter to the ambient atmosphere. The majority of the heat load on the cooler is from the high temperature ambient surface environment on Venus, with a small contribution of heat generation from electronics and sensors. Both thermoelectric (RTG) and dynamic power conversion systems were analyzed, based on use of a standard isotope (General-purpose heat source, or GPHS) brick. For the radioisotope Stirling power converter configuration designed, the Sage model predicts a thermodynamic power output capacity of 478.1 watts, which slightly exceeds the required 469.1 watts. The hot sink temperature is 1200 C, and the cold sink temperature is 500 C. The required heat input is 1740 watts. This gives a thermodynamic efficiency of 27.48 %. It is estimated that the mechanical efficiency of the power converter design is on the order of 85 %, based on experimental measurements taken from 500-watt power class, laboratory-tested Stirling engines. The overall efficiency is calculated to be 23.36 %. The mass of the power converter is estimated at approximately 21.6 kg

  9. Venus Surface Power and Cooling System Design

    Science.gov (United States)

    Landis, Geoffrey A.; Mellott, Kenneth D.

    2004-01-01

    A radioisotope power and cooling system is designed to provide electrical power for the a probe operating on the surface of Venus. Most foreseeable electronics devices and sensors simply cannot operate at the 450 C ambient surface temperature of Venus. Because the mission duration is substantially long and the use of thermal mass to maintain an operable temperature range is likely impractical, some type of active refrigeration may be required to keep certain components at a temperature below ambient. The fundamental cooling requirements are comprised of the cold sink temperature, the hot sink temperature, and the amount of heat to be removed. In this instance, it is anticipated that electronics would have a nominal operating temperature of 300 C. Due to the highly thermal convective nature of the high-density atmosphere, the hot sink temperature was assumed to be 50 C, which provided a 500 C temperature of the cooler's heat rejecter to the ambient atmosphere. The majority of the heat load on the cooler is from the high temperature ambient surface environment on Venus. Assuming 5 cm radial thickness of ceramic blanket insulation, the ambient heat load was estimated at approximately 77 watts. With an estimated quantity of 10 watts of heat generation from electronics and sensors, and to accommodate some level of uncertainty, the total heat load requirement was rounded up to an even 100 watts. For the radioisotope Stirling power converter configuration designed, the Sage model predicts a thermodynamic power output capacity of 478.1 watts, which slightly exceeds the required 469.1 watts. The hot sink temperature is 1200 C, and the cold sink temperature is 500 C. The required heat input is 1740 watts. This gives a thermodynamic efficiency of 27.48 %. The maximum theoretically obtainable efficiency is 47.52 %. It is estimated that the mechanical efficiency of the power converter design is on the order of 85 %, based on experimental measurements taken from 500 watt power

  10. Optimal Design of Sheet Pile Wall Embedded in Clay

    Science.gov (United States)

    Das, Manas Ranjan; Das, Sarat Kumar

    2015-09-01

    Sheet pile wall is a type of flexible earth retaining structure used in waterfront offshore structures, river protection work and temporary supports in foundations and excavations. Economy is an essential part of a good engineering design and needs to be considered explicitly in obtaining an optimum section. By considering appropriate embedment depth and sheet pile section it may be possible to achieve better economy. This paper describes optimum design of both cantilever and anchored sheet pile wall penetrating clay using a simple optimization tool Microsoft Excel ® Solver. The detail methodology and its application with examples are presented for cantilever and anchored sheet piles. The effects of soil properties, depth of penetration and variation of ground water table on the optimum design are also discussed. Such a study will help professional while designing the sheet pile wall penetrating clay.

  11. Anesthesia Fact Sheet

    Science.gov (United States)

    ... Education About NIGMS NIGMS Home > Science Education > Anesthesia Anesthesia Tagline (Optional) Middle/Main Content Area En español ... Version (464 KB) Other Fact Sheets What is anesthesia? Anesthesia is a medical treatment that prevents patients ...

  12. Global ice sheet modeling

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, T.J.; Fastook, J.L. [Univ. of Maine, Orono, ME (United States). Institute for Quaternary Studies

    1994-05-01

    The University of Maine conducted this study for Pacific Northwest Laboratory (PNL) as part of a global climate modeling task for site characterization of the potential nuclear waste respository site at Yucca Mountain, NV. The purpose of the study was to develop a global ice sheet dynamics model that will forecast the three-dimensional configuration of global ice sheets for specific climate change scenarios. The objective of the third (final) year of the work was to produce ice sheet data for glaciation scenarios covering the next 100,000 years. This was accomplished using both the map-plane and flowband solutions of our time-dependent, finite-element gridpoint model. The theory and equations used to develop the ice sheet models are presented. Three future scenarios were simulated by the model and results are discussed.

  13. Global ice sheet modeling

    International Nuclear Information System (INIS)

    Hughes, T.J.; Fastook, J.L.

    1994-05-01

    The University of Maine conducted this study for Pacific Northwest Laboratory (PNL) as part of a global climate modeling task for site characterization of the potential nuclear waste respository site at Yucca Mountain, NV. The purpose of the study was to develop a global ice sheet dynamics model that will forecast the three-dimensional configuration of global ice sheets for specific climate change scenarios. The objective of the third (final) year of the work was to produce ice sheet data for glaciation scenarios covering the next 100,000 years. This was accomplished using both the map-plane and flowband solutions of our time-dependent, finite-element gridpoint model. The theory and equations used to develop the ice sheet models are presented. Three future scenarios were simulated by the model and results are discussed

  14. Structural Biology Fact Sheet

    Science.gov (United States)

    ... beta sheets (blue; thinner, tangled strands). Credit: RCSB Protein Data Bank. Even though proteins are strings of amino acids, ... structure of more than 122,000 proteins. The Protein Data Bank stores these structures and gives scientists access to ...

  15. Sepsis Fact Sheet

    Science.gov (United States)

    ... Education About NIGMS NIGMS Home > Science Education > Sepsis Sepsis Tagline (Optional) Middle/Main Content Area PDF Version ( ... KB) En español Other Fact Sheets What is sepsis? Sepsis is a serious medical condition. It is ...

  16. Respirator Fact Sheet

    Science.gov (United States)

    ... to protect myself, my family, and/or my employees? If available and used correctly, a respirator can ... Respirator Fact Sheet [PDF - 706 KB] Follow NIOSH Facebook Flickr Pinterest Twitter YouTube NIOSH Homepage NIOSH A- ...

  17. The Venus Emissivity Mapper - Investigating the Atmospheric Structure and Dynamics of Venus' Polar Region

    Science.gov (United States)

    Widemann, T.; Marcq, E.; Tsang, C.; Mueller, N. T.; Kappel, D.; Helbert, J.; Dyar, M. D.; Smrekar, S. E.

    2017-12-01

    Venus' climate evolution is driven by the energy balance of its global cloud layers. Venus displays the best-known case of polar vortices evolving in a fast-rotating atmosphere. Polar vortices are pervasive in the Solar System and may also be present in atmosphere-bearing exoplanets. While much progress has been made since the early suggestion that the Venus clouds are H2O-H2SO4 liquid droplets (Young 1973), several cloud parameters are still poorly constrained, particularly in the lower cloud layer and optically thicker polar regions. The average particle size is constant over most of the planet but increases toward the poles. This indicates that cloud formation processes are different at latitudes greater than 60°, possibly as a result of the different dynamical regimes that exist in the polar vortices (Carlson et al. 1993, Wilson et al. 2008, Barstow et al. 2012). Few wind measurements exist in the polar region due to unfavorable viewing geometry of currently available observations. Cloud-tracking data indicate circumpolar circulation close to solid-body rotation. E-W winds decrease to zero velocity close to the pole. N-S circulation is marginal, with extremely variable morphology and complex vorticity patterns (Sanchez-Lavega et al. 2008, Luz et al. 2011, Garate-Lopez et al. 2013). The Venus Emissivity Mapper (VEM; Helbert et al., 2016) proposed for NASA's Venus Origins Explorer (VOX) and the ESA M5/EnVision orbiters has the capability to better constrain the microphysics (vertical, horizontal, time dependence of particle size distribution, or/and composition) of the lower cloud particles in three spectral bands at 1.195, 1.310 and 1.510 μm at a spatial resolution of 10 km. Circular polar orbit geometry would provide an unprecedented study of both polar regions within the same mission. In addition, VEM's pushbroom method will allow short timescale cloud dynamics to be assessed, as well as local wind speeds, using repeated imagery at 90 minute intervals

  18. Energy information sheets

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-07-01

    The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

  19. The Reappearance of Venus Observed 8 October 2015

    Science.gov (United States)

    Dunham, David W.; Dunham, Joan B.

    2018-01-01

    The reappearance of Venus on October 8, 2015 offered a unique opportunity to attempt observation of the ashen light of Venus as the unlit side of Venus emerged from behind the dark side of the Moon. The dark side of Venus would be offered to observers without interference from the bright side of Venus or of the Moon. Observations were made from Alice Springs, Australia visually with a 20-cm Schmidt-Cassegrain and with a low-light level surveillance camera on a 25-cm reflector. No evidence of the dark side was noted by the visual observer, the video shows little indication of Venus prior to the bright side reappearance. The conclusion reached is that the ashen light, as it was classically defined, is not observable visually or with small telescopes in the visual regime.The presentation describes the prediction, observation technique, and various analyses by the authors and others to draw conclusions from the data.To date, the authors have been unable to locate any reports of others attempting to observe this unique event. That is a pity since, not only was it interesting for an attempt to verify past observations of the ashen light, it was also a visually stunning event.

  20. An Encounter between the Sun and Venus

    CERN Multimedia

    2004-01-01

    The astronomical event of the year will take place on Tuesday, 8 June, when Venus transits across the disk of the sun. In the framework of CERN's 50th anniversary celebrations, the CERN Astronomy Club and the Orion Club invite you to attend their observation of the event on the car park of the Val-Thoiry shopping centre (France) between 7.15 a.m. and 1.30 p.m. Various instruments will be set up in a special tent so that the event can be observed without any risk of damage to the eyes. As the observation of this astronomical event will depend on the weather forecast, confirmation of the above arrangements will be given on the 50th anniversary website the day before.

  1. Nuclear instrumentation in VENUS-F

    Directory of Open Access Journals (Sweden)

    Wagemans J.

    2018-01-01

    Full Text Available VENUS-F is a fast zero power reactor with 30 wt% U fuel and Pb/Bi as a coolant simulator. Depending on the experimental configuration, various neutron spectra (fast, epithermal, and thermal islands are present. This paper gives a review of the nuclear instrumentation that is applied for reactor control and in a large variety of physics experiments. Activation foils and fission chambers are used to measure spatial neutron flux profiles, spectrum indices, reactivity effects (with positive period and compensation method or the MSM method and kinetic parameters (with the Rossi-alpha method. Fission chamber calibrations are performed in the standard irradiation fields of the BR1 reactor (prompt fission neutron spectrum and Maxwellian thermal neutron spectrum.

  2. Nuclear instrumentation in VENUS-F

    Science.gov (United States)

    Wagemans, J.; Borms, L.; Kochetkov, A.; Krása, A.; Van Grieken, C.; Vittiglio, G.

    2018-01-01

    VENUS-F is a fast zero power reactor with 30 wt% U fuel and Pb/Bi as a coolant simulator. Depending on the experimental configuration, various neutron spectra (fast, epithermal, and thermal islands) are present. This paper gives a review of the nuclear instrumentation that is applied for reactor control and in a large variety of physics experiments. Activation foils and fission chambers are used to measure spatial neutron flux profiles, spectrum indices, reactivity effects (with positive period and compensation method or the MSM method) and kinetic parameters (with the Rossi-alpha method). Fission chamber calibrations are performed in the standard irradiation fields of the BR1 reactor (prompt fission neutron spectrum and Maxwellian thermal neutron spectrum).

  3. Sulfuric Acid Vapor in the Atmosphere of Venus as Observed by the Venus Express Radio Science Experiment VeRa

    Science.gov (United States)

    Oschlisniok, Janusz; Pätzold, Martin; Häusler, Bernd; Tellmann, Silvia; Bird, Michael; Andert, Thomas

    2017-10-01

    The cloud deck within Venus' atmosphere, which covers the entire planet between approx. 50 and 70 km altitude, consists mostly of liquid and gaseous sulfuric acid. The gaseous part increases strongly just below the main clouds and builds an approx. 15 km thick haze layer of H2SO4. This region is responsible for a strong absorption of radio waves as seen in Mariner, Pioneer Venus, Magellan and Venera radio science observations. The amount of H2SO4 is derived from the observed absorption as a function of altitude and latitude. The radio science experiment VeRa onboard Venus Express probed the atmosphere of Venus between 2006 and 2015 with radio signals at 13 cm (S-band) and 3.6 cm (X-band) wavelengths. The orbit of the Venus Express spacecraft allowed to sound the atmosphere over a wide range of latitudes and local times providing a global picture of the sulfuric acid vapor distribution. We present absorptivity and H2SO4 profiles derived from X-band signal attenuation for the time of the entire Venus Express mission. More than 600 H2SO4 profiles show the global sulfuric acid vapor distribution covering the northern and southern hemisphere on the day- and night side of the planet. A distinct latitudinal H2SO4 gradient and a southern northern symmetry are clearly visible. Observations over 8 years allow to study also long-term variations. Indications for temporal H2SO4 variations are found, at least at northern polar latitudes. The results shall be compared with observations retrieved by other experiments (VIRTIS, SPICAV) onboard Venus Express as well as with previous observations like Mariner, Pioneer Venus and the Magellan spacecraft.

  4. Sulfuric Acid Vapor in the Atmosphere of Venus as observed by the Venus Express Radio Science Experiment VeRa.

    Science.gov (United States)

    Oschlisniok, J.; Paetzold, M.; Häusler, B.; Tellmann, S.; Bird, M. K.; Andert, T.

    2017-12-01

    The cloud deck within Venus' atmosphere, which covers the entire planet between approx. 50 and 70 km altitude, consists mostly of liquid and gaseous sulfuric acid. The gaseous part increases strongly just below the main clouds and builds an approx. 15 km thick haze layer of H2SO4. This region is responsible for a strong absorption of radio waves as seen in Mariner, Pioneer Venus, Magellan and Venera radio science observations. The amount of H2SO4 is derived from the observed absorption as a function of altitude and latitude. The radio science experiment VeRa onboard Venus Express probed the atmosphere of Venus between 2006 and 2015 with radio signals at 13 cm (S-band) and 3.6 cm (X-band) wavelengths. The orbit of the Venus Express spacecraft allowed to sound the atmosphere over a wide range of latitudes and local times providing a global picture of the sulfuric acid vapor distribution. We present absorptivity and H2SO4 profiles derived from X-band signal attenuation for the time of the entire Venus Express mission. More than 600 H2SO4 profiles show the global sulfuric acid vapor distribution covering the northern and southern hemisphere on the day- and night side of the planet. A distinct latitudinal H2SO4 gradient and a southern northern symmetry are clearly visible. Observations over 8 years allow to study also long-term variations. Indications for temporal H2SO4 variations are found, at least at northern polar latitudes. The results shall be compared with observations retrieved by other experiments (VIRTIS, SPICAV) onboard Venus Express as well as with previous observations like Mariner, Pioneer Venus and the Magellan spacecraft.

  5. Whistler mode waves from lightning on Venus: Magnetic control of ionospheric access

    Science.gov (United States)

    Russell, C. T.; Zhang, T. L.; Wei, H. Y.

    2008-09-01

    The fluxgate magnetometer on Venus Express samples the magnetic field near periapsis at 128 Hz. Bursts of plane-polarized magnetic waves in the vicinity of 100 Hz are observed propagating at small angles to the magnetic field. The magnetic field is generally horizontal in the region around periapsis, located at high northern latitudes. When the magnetic field remains within 15° of horizontal during the 2-min periapsis pass, no such waves are observed; but when there are brief periods during which the local magnetic field dips into the atmosphere by more than 15°, the bursts begin to appear. Such radial excursions of the magnetic field occur 25% of the time in the region around periapsis. The bursts are seen only on passes with these excursions. We interpret this magnetic control in terms of the coupling between the electromagnetic wave from lightning discharges refracted vertically by the increasing electron density and the nearly horizontal ionospheric magnetic field along which the energy is guided to the spacecraft. The inferred rate of electric discharges in the Venus atmosphere is about 20% of that seen in the Earth's atmosphere.

  6. On the reality of the Venus winds. [Venera satellite and Mariner space probe data

    Science.gov (United States)

    Ainsworth, J. E.; Herman, J. R.

    1975-01-01

    The Venera measurements of wind speed along with the Mariner measurements of lower-region of strong turbulence are evidence for a wide band of variable high speed retrograde horizontal winds which girdle Venus at the equator. In one interpretation of the Mariner 10 UV photographs, the 20km region above the top of the visible cloud is characterized by variable high-speed retrograde horizontal winds which orbit Venus with an average period of 4 earth days, and by many features indicating vertical convection. This suggests that the Venera-Mariner band of winds at 45km extends to the top of the UV cloud and beyond, and that the upper-region of strong turbulence detected by the Mariners may result from vertical convection currents carried along by high speed horizontal winds. In another interpretation, the predominate motions are attributed to wavelike disturbances with a 4-day period. For this case the upper-region of strong turbulence may be due in large part to vertical wind-shear resulting from a rapid decrease in wind speed within a relatively short distance about the Venera-Mariner band of high speed winds.

  7. Impact-driven planetary desiccation: The origin of the dry Venus

    Science.gov (United States)

    Kurosawa, Kosuke

    2015-11-01

    The fate of surface water on Venus is one of the most important outstanding problems in comparative planetology. Although Venus should have had a large amount of surface water (like the Earth) during its formation, the current water content on the Venusian surface is only 1 part in 100 000 of that of the mass of Earth's oceans. Here a new concept is proposed to explain water removal on a steam-covered proto Venus, referred to as ;impact-driven planetary desiccation;. Since a steam atmosphere is photochemically unstable, water vapor dissociates into hydrogen and oxygen. Then, hydrogen escapes easily into space through hydrodynamic escape driven by strong extreme ultraviolet radiation from the young Sun. The focus is on the intense impact bombardment during the terminal stage of planetary accretion as generators of a significant amount of reducing agent. The fine-grained ejecta remove the residual oxygen, the counter part of escaped hydrogen, via the oxidation of iron-bearing rocks in a hot atmosphere. Thus, hypervelocity impacts cause net desiccation of the planetary surface. I constructed a stochastic cratering model using a Monte Carlo approach to investigate the cumulative mass of nonoxidized, ejected rocks due to the intense impact bombardment. The ejecta mass after each impact was calculated using the π-group scaling laws and a modified Maxwell's Z model. The effect of projectile penetration into the ground on the ejecta mass was also included. Next, an upper limit on the total amount of removed water was calculated using the stoichiometric limit of the oxidation of basaltic rocks, taking into account the effect of fast H2 escape. It is shown that a thick steam atmosphere with a mass equivalent to that of the terrestrial oceans would be removed. The cumulative mass of rocky ejecta released into the atmosphere reaches 1 wt% of the host planet, which is 10 000 times of the current mass of the Earth's atmosphere. These results strongly suggest that chemical

  8. The Venera-D Mission Concept: Evaluation by a Joint Science Definition Team of a Means for the Comprehensive Scientific Exploration of Venus

    Science.gov (United States)

    Senske, D.; Zasova, L. V.; Economou, T.; Eismont, N.; Esposito, L. W.; Gerasimov, M.; Ignatiev, N. I.; Ivanov, M.; Jessup, K. L.; Korablev, O.; Tibor, K.; Limaye, S. S.; Martynov, A.; Ocampo, A.

    2016-12-01

    Located in the same part of the solar system and formed out of the same protoplanetary material, Venus is Earth's twin. Although these siblings have nearly the same size, mass, and density, the climate of Venus, fueled by a massive CO2 atmosphere has an enormous greenhouse effect with a surface pressure of 90 atm. and a temperature of 470°C. Shrouded in clouds of sulfuric acid, the surface lacks water and has been sculpted by volcanism and deformed by faulting and folding forming rifts and belts of mountains. The lack of an intrinsic magnetic field suggests the planet's interior structure may be different than that of the earth. The study of Venus will aid in better understanding our own world and the possible future evolution of our climate. In particular, the instability of our climate and the increase in amount of greenhouse gases-can our climate be slowly going in Venus' direction? Despite the advancement in understanding achieved from previous and ongoing missions, the key questions concerning the origin and evolution of Venus and its climate cannot be solved by observations from orbit alone. Direct measurements in the atmosphere and on the surface are required. In this regard, a Joint Science Definition Team (JSDT) chartered by NASA and IKI/Roscosmos has been studying a concept for the comprehensive investigation of Venus that would consist of an orbiter (>3 yr. of operation) and a lander (2 hrs. on the surface). The scientific goals of the concept are tied closely to the key objectives established by VEXAG and the NASA Planetary Decadal Survey and include: investigation of the thermal structure and chemical composition of the atmosphere and clouds, abundances and isotopic ratios of the light and noble gases; study of the thermal balance, dynamics, and super-rotation of the atmosphere; determination of the surface mineralogy and elemental composition including key radioactive isotopes; study of potential current volcanic and electrical activity; and study of

  9. Venus Interior Probe Using In-situ Power and Propulsion (VIP-INSPR), Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We envision a novel architecture for Venus Interior Probes based on in-situ resources for power generation (VIP-INSPR). Proposed Venus probe is based on the...

  10. The Creation of a Beneficial Bioshpere from Co2 in the Clouds of Venus

    Science.gov (United States)

    Linaraki, D. L.; Oungrinis, K. A.

    2017-02-01

    This research resulted in an architectural design for a Venus colony based on multiple factors combination, such as psychology of space, predicted near-future technology, and the identified environmental conditions on Venus.

  11. PIONEER 12 VENUS ORBITING RADAR DERIVED RADAR IMAGES V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of five VICAR2 format images of Venus derived from Pioneer Venus radar altimeter measurements. Data are presented in simple cylindrical...

  12. Magnetic configurations of the tilted current sheets in magnetotail

    Directory of Open Access Journals (Sweden)

    C. Shen

    2008-11-01

    Full Text Available In this research, the geometrical structures of tilted current sheet and tail flapping waves have been analysed based on multiple spacecraft measurements and some features of the tilted current sheets have been made clear for the first time. The geometrical features of the tilted current sheet revealed in this investigation are as follows: (1 The magnetic field lines (MFLs in the tilted current sheet are generally plane curves and the osculating planes in which the MFLs lie are about vertical to the equatorial plane, while the normal of the tilted current sheet leans severely to the dawn or dusk side. (2 The tilted current sheet may become very thin, the half thickness of its neutral sheet is generally much less than the minimum radius of the curvature of the MFLs. (3 In the neutral sheet, the field-aligned current density becomes very large and has a maximum value at the center of the current sheet. (4 In some cases, the current density is a bifurcated one, and the two humps of the current density often superpose two peaks in the gradient of magnetic strength, indicating that the magnetic gradient drift current is possibly responsible for the formation of the two humps of the current density in some tilted current sheets. Tilted current sheets often appear along with tail current sheet flapping waves. It is found that, in the tail flapping current sheets, the minimum curvature radius of the MFLs in the current sheet is rather large with values around 1 RE, while the neutral sheet may be very thin, with its half thickness being several tenths of RE. During the flapping waves, the current sheet is tilted substantially, and the maximum tilt angle is generally larger than 45°. The phase velocities of these flapping waves are several tens km/s, while their periods and wavelengths are several tens of minutes, and several earth radii, respectively. These tail flapping events generally last several hours and occur during quiet periods or periods of

  13. Magnetic Storms at Mars and Earth

    DEFF Research Database (Denmark)

    Vennerstrøm, Susanne; Falkenberg, Thea Vilstrup

    In analogy with magnetic storms at the Earth, periods of significantly enhanced global magnetic activity also exist at Mars. The extensive database of magnetic measurements from Mars Global Surveyor (MGS), covering almost an entire solar cycle, is used in combination with geomagnetic activity...... indices at Earth to compare the occurrence of magnetic storms at Mars and Earth. Based on superposed epochs analysis the time-development of typical magnetic storms at Mars and Earth is described. In contradiction to storms at Earth, most magnetic storms at Mars are found to be associated...... with heliospheric current sheet crossings, where the IMF changes polarity. While most storms at the Earth occur due to significant southward excursions of the IMF associated with CMEs, at Mars most storms seem to be associated with the density enhancement of the heliospheric current sheet. Density enhancements...

  14. Global ice sheet/RSL simulations using the higher-order Ice Sheet System Model.

    Science.gov (United States)

    Larour, E. Y.; Ivins, E. R.; Adhikari, S.; Schlegel, N.; Seroussi, H. L.; Morlighem, M.

    2017-12-01

    Relative sea-level rise is driven by processes that are intimately linked to the evolution ofglacial areas and ice sheets in particular. So far, most Earth System models capable of projecting theevolution of RSL on decadal to centennial time scales have relied on offline interactions between RSL andice sheets. In particular, grounding line and calving front dynamics have not been modeled in a way that istightly coupled with Elasto-Static Adjustment (ESA) and/or Glacial-Isostatic Adjustment (GIA). Here, we presenta new simulation of the entire Earth System in which both Greenland and Antarctica ice sheets are tightly coupledto an RSL model that includes both ESA and GIA at resolutions and time scales compatible with processes suchas grounding line dynamics for Antarctica ice shelves and calving front dynamics for Greenland marine-terminatingglaciers. The simulations rely on the Ice Sheet System Model (ISSM) and show the impact of higher-orderice flow dynamics and coupling feedbacks between ice flow and RSL. We quantify the exact impact of ESA andGIA inclusion on grounding line evolution for large ice shelves such as the Ronne and Ross ice shelves, as well asthe Agasea Embayment ice streams, and demonstate how offline vs online RSL simulations diverge in the long run,and the consequences for predictions of sea-level rise.This work was performed at the California Institute of Technology's Jet Propulsion Laboratory undera contract with the National Aeronautics and Space Administration's Cryosphere Science Program.

  15. Safety advice sheets

    CERN Multimedia

    HSE Unit

    2013-01-01

    You never know when you might be faced with questions such as: when/how should I dispose of a gas canister? Where can I find an inspection report? How should I handle/store/dispose of a chemical substance…?   The SI section of the DGS/SEE Group is primarily responsible for safety inspections, evaluating the safety conditions of equipment items, premises and facilities. On top of this core task, it also regularly issues “Safety Advice Sheets” on various topics, designed to be of assistance to users but also to recall and reinforce safety rules and procedures. These clear and concise sheets, complete with illustrations, are easy to display in the appropriate areas. The following safety advice sheets have been issued so far: Other sheets will be published shortly. Suggestions are welcome and should be sent to the SI section of the DGS/SEE Group. Please send enquiries to general-safety-visits.service@cern.ch.

  16. Using REE tracers to measure sheet erosion changing to rill erosion

    International Nuclear Information System (INIS)

    Liu Puling; Xue Yazhou; Song Wei; Wang Mingyi; Ju Tongjun

    2004-01-01

    Rare Earth Elements (REE) tracer method was used to study sheet erosion changing to rill erosion on slope land. By placing different rare earth elements of different soil depth across a slope in an indoor plot, two simulated rainfalls were applied to study the change of erosion type and the rill erosion process. The results indicate that the main erosion type is sheet erosion at the beginning of the rainfalls, and serious erosion happens after rill erosion appears. Accumulated sheet and rill erosion amounts increase with the rainfalls time. The percentage of sheet erosion amount decreases and rill erosion percentage increases with time. At the end of the rainfalls, the total rill erosion amounts are 4-5 times more than sheet erosion. In this paper, a new REE tracer method was used to quantitatively distinguish sheet and rill erosion amounts. The new REE tracer method should be useful to future studying of erosion processes on slope lands. (authors)

  17. 3D modeling of lightning-induced electromagnetic pulses on Venus, Jupiter and Saturn

    Science.gov (United States)

    Pérez-Invernón, Francisco J.; Luque, Alejandro; Gordillo-Vázquez, Francisco J.

    2017-04-01

    Atmospheric electricity is a common phenomenon in some planets of The Solar System. We know that atmospheric discharges exist on Earth and gaseous planets; however, some characteristics of lightning on Saturn and Jupiter as well as their relevance on the effects of lightning in the atmospheres of these planets are still unknown. In the case of Venus, there exist some radio evidences of lightning, but the lack of optical observations suggests exploring indirect methods of detection, such as searching for lightning-induced transient optical emissions from the upper atmosphere. The Akatsuki probe, currently orbiting Venus, is equipped with a camera whose temporal resolution is high enough to detect optical emissions from lightning discharges and to measure nightglow enhancements. In this work, we extend previous models [1,2] to investigate the chemical impact and transient optical emissions produced by possible lightning-emitted electromagnetic pulses (EMP) in Venus, Saturn and Jupiter. Using a 3D FDTD ("Finite Differences Time Domain") model we solve the Maxwell equations coupled with the Langevin equation for electrons [3] and with a kinetic scheme, different for each planetary atmosphere. This method is useful to investigate the temporal and spatial impact of lightning-induced electromagnetic fields in the atmosphere of each planet for different lightning characteristics (e.g. energy released, orientation). This 3D FDTD model allows us to include the saturnian and jovian background magnetic field inclination and magnitude at different latitudes, and to determine the effects of different lightning channel inclinations. Results provide useful information to interpret lightning observations on giant gaseous planets and in the search for indirect optical signals from atmospheric discharge on Venus such as fast nightglow transient enhancements related to lightning as seen on Earth. Furthermore, we underline the observation of electrical discharges characteristics as a

  18. Energy information sheets

    Energy Technology Data Exchange (ETDEWEB)

    1993-12-02

    The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the general public. Written for the general public, the EIA publication Energy Information Sheets was developed to provide information on various aspects of fuel production, prices, consumption and capability. The information contained herein pertains to energy data as of December 1991. Additional information on related subject matter can be found in other EIA publications as referenced at the end of each sheet.

  19. ULF waves upstream of the Venus bow shock - Properties of one-hertz waves

    Science.gov (United States)

    Orlowski, D. S.; Russell, C. T.

    1991-01-01

    Pioneer Venus Orbiter data are used here to study the properties of a class of ULF upstream waves with relatively high observed frequencies. These waves show significant similarity to 'one-Hz' waves identified at earth in the ISEE 1 and 2 observations and the whistler waves identified earlier by IMP 6 observations. The waves appear almost immediately after the spacecraft crosses the magnetic field tangent line to the bow shock surface into the region of connected field lines. The wave amplitude decreases with distance from the shock measured along the magnetic field line. Group velocities calculated using the cold plasma dispersion relation indicate that the waves have sufficient upstream velocities to propagate form the shock into the solar wind. The totality of observations seem best explained by a source of right-handed whistler mode waves at the bow shock.

  20. Tectonics of the southern escarpment of Ishtar Terra on Venus from observations of morphology and gravity

    International Nuclear Information System (INIS)

    Janle, P.; Jannsen, D.

    1984-01-01

    Maxima of calculated topographical line-of-sight (LOS) gravity attractions caused by Ishtar Terra are shifted to the north with respect to the measured LOS free air gravity maxima south of the highland. This implies a tendency to isostatic compensation of central Ishtar and mass surpluses at the continental border and the southern forelands. The authors present a scenario compatible with the interpretation of the gravity anomalies and morphological features. The existence of global plate tectonics on Venus like on Earth is not necessarily implied, but at least limited horizontal movements of the Venusian lithosphere seem to be likely. This result shows that plate recycling must be considered for heat transfer through the lithosphere beside conduction and hot spot volcanism. (Auth.)

  1. Columbus State University Global Observation and Outreach for the 2012 Transit of Venus

    Science.gov (United States)

    Perry, Matthew; McCarty, C.; Bartow, M.; Hood, J. C.; Lodder, K.; Johnson, M.; Cruzen, S. T.; Williams, R. N.

    2013-01-01

    Faculty, staff and students from Columbus State University’s (CSU’s) Coca-Cola Space Science Center presented a webcast of the 2012 Transit of Venus from three continents to a global audience of 1.4 million unique viewers. Team members imaged the transit with telescopes using white-light, hydrogen-alpha, and calcium filters, from Alice Springs, Australia; the Gobi Desert, Mongolia; Bryce Canyon, UT; and Columbus, GA. Images were webcast live during the transit in partnership with NASA’s Sun-Earth Day program, and Science Center staff members were featured on NASA TV. Local members of the public were brought in for a series of outreach initiatives, in both Georgia and Australia, before and during the transit. The data recorded from the various locations have been archived for use in demonstrating principles such as the historical measurement of the astronomical unit.

  2. Late Veneer consequences on Venus' long term evolution

    Science.gov (United States)

    Gillmann, C.; Golabek, G.; Tackley, P. J.; Raymond, S. N.

    2017-12-01

    Modelling of Venus' evolution is able to produce scenarios consistent with present-day observation. These results are however heavily dependent on atmosphere escape and initial volatile inventory. This primordial history (the first 500 Myr) is heavily influenced by collisions. We investigate how Late Veneer impacts change the initial state of Venus and their consequences on its coupled mantle/atmosphere evolution. We focus on volatile fluxes: atmospheric escape and mantle degassing. Mantle dynamics is simulated using the StagYY code. Atmosphere escape covers both thermal and non-thermal processes. Surface conditions are calculated with a radiative-convective model. Feedback of the atmosphere on the mantle through surface temperature is included. Large impacts are capable of contributing to atmospheric escape, volatile replenishment and energy transfer. We use the SOVA hydrocode to take into account volatile loss and deposition during a collision. Large impacts are not numerous enough to substantially erode Venus' atmosphere. Single impacts don't have enough eroding power. Swarms of small bodies (lack of plate tectonics and volatile recycling in the interior of Venus, Late Veneer collisions could help explain why Venus seems dry today.

  3. Neutral sheet crossings in the distant magnetotail

    International Nuclear Information System (INIS)

    Heikkila, W.J.; Slavin, J.A.; Smith, E.J.; Baker, D.N.; Zwickl, R.D.

    1985-01-01

    We have analyzed the magnetic field data from ISEE-3 in the distant magnetotail for 18 crossings of the cross-tail current sheet (or so-called natural sheet) to determine the direction of the normal component B/sub z/. The crossings occurred near the middle of the aberrated magnetotail (0 0.4 nT), consistent with closed field lines connected to the earth. In 3 cases B/sub z/ was very close to zero; in several instances there was structure in B/sub y/, suggesting localized currents with x or z directions. One may have been a magnetopause crossing. The strong preponderance of northward B/sub z/ favors a model of the magnetotail which is dominated by boundary layer plasma, flowing tailward on closed magnetic field lines, which requires the existence of an electric field in the sense from dusk to dawn. 37 refs., 15 figs., 1 tab

  4. Effects of electron pressure anisotropy on current sheet configuration

    International Nuclear Information System (INIS)

    Artemyev, A. V.; Angelopoulos, V.; Runov, A.; Vasko, I. Y.

    2016-01-01

    Recent spacecraft observations in the Earth's magnetosphere have demonstrated that the magnetotail current sheet can be supported by currents of anisotropic electron population. Strong electron currents are responsible for the formation of very thin (intense) current sheets playing the crucial role in stability of the Earth's magnetotail. We explore the properties of such thin current sheets with hot isotropic ions and cold anisotropic electrons. Decoupling of the motions of ions and electrons results in the generation of a polarization electric field. The distribution of the corresponding scalar potential is derived from the electron pressure balance and the quasi-neutrality condition. We find that electron pressure anisotropy is partially balanced by a field-aligned component of this polarization electric field. We propose a 2D model that describes a thin current sheet supported by currents of anisotropic electrons embedded in an ion-dominated current sheet. Current density profiles in our model agree well with THEMIS observations in the Earth's magnetotail.

  5. MEaSUREs Greenland Ice Sheet Velocity Map from InSAR Data V002

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set, part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) program, contains seasonal (winter) ice-sheet-wide...

  6. MEaSUREs Greenland Ice Sheet Velocity Map from InSAR Data

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set, part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) program, provides annual ice-sheet-wide velocity maps...

  7. MEaSUREs Greenland Ice Sheet Velocity Map from InSAR Data V001

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set, part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) program, provides annual ice-sheet-wide velocity maps...

  8. MEaSUREs Multi-year Greenland Ice Sheet Velocity Mosaic V001

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set, part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) program, contains a multi-year ice-sheet-wide velocity...

  9. The separatrix tentacle effect of ion acceleration to the plasma sheet boundary

    Science.gov (United States)

    Buechner, Joerg; Zelenyi, Lev M.

    1990-02-01

    The effect of a continuous ion acceleration in the earth's magnetotail due to chaotic particle scattering caused by separatrix traversals in the velocity space is described. This effect operates almost everywhere in the plasma sheet, but outside and independent of neutral lines. As a distributed inner source, it supports fast ion streams at the boundary of the plasma sheet.

  10. The separatrix tentacle effect of ion acceleration to the plasma sheet boundary

    Energy Technology Data Exchange (ETDEWEB)

    Buechner, J. (Central Institute for Astrophysics, Potsdam (German Democratic Republic)); Zelenyi, L.M. (Space Research Institute, Moscow (USSR))

    1990-02-01

    The authors describe the effect of a continuous ion-acceleration in the Earth's magnetotail due to chaotic particle scattering caused by separatrix traversals in the velocity space. This effect operates almost everywhere in the plasma sheet, but outside and independent of neutral lines. As a distributed inner source it supports fast ion streams at the boundary of the plasma sheet.

  11. Ice Sheets & Ice Cores

    DEFF Research Database (Denmark)

    Mikkelsen, Troels Bøgeholm

    Since the discovery of the Ice Ages it has been evident that Earth’s climate is liable to undergo dramatic changes. The previous climatic period known as the Last Glacial saw large oscillations in the extent of ice sheets covering the Northern hemisphere. Understanding these oscillations known...

  12. Pseudomonas - Fact Sheet

    OpenAIRE

    Public Health Agency

    2012-01-01

    Fact sheet on Pseudomonas, including:What is Pseudomonas?What infections does it cause?Who is susceptible to pseudomonas infection?How will I know if I have pseudomonas infection?How can Pseudomonas be prevented from spreading?How can I protect myself from Pseudomonas?How is Pseudomonas infection treated?

  13. Collisionless current sheet equilibria

    Science.gov (United States)

    Neukirch, T.; Wilson, F.; Allanson, O.

    2018-01-01

    Current sheets are important for the structure and dynamics of many plasma systems. In space and astrophysical plasmas they play a crucial role in activity processes, for example by facilitating the release of magnetic energy via processes such as magnetic reconnection. In this contribution we will focus on collisionless plasma systems. A sensible first step in any investigation of physical processes involving current sheets is to find appropriate equilibrium solutions. The theory of collisionless plasma equilibria is well established, but over the past few years there has been a renewed interest in finding equilibrium distribution functions for collisionless current sheets with particular properties, for example for cases where the current density is parallel to the magnetic field (force-free current sheets). This interest is due to a combination of scientific curiosity and potential applications to space and astrophysical plasmas. In this paper we will give an overview of some of the recent developments, discuss their potential applications and address a number of open questions.

  14. Ethanol Basics (Fact Sheet)

    Energy Technology Data Exchange (ETDEWEB)

    2015-01-01

    Ethanol is a widely-used, domestically-produced renewable fuel made from corn and other plant materials. More than 96% of gasoline sold in the United States contains ethanol. Learn more about this alternative fuel in the Ethanol Basics Fact Sheet, produced by the U.S. Department of Energy's Clean Cities program.

  15. Tectonic evolution of Lavinia Planitia, Venus

    Science.gov (United States)

    Squyres, Steven W.; Frank, Sharon L.; Mcgill, George E.; Solomon, Sean C.

    1991-01-01

    High resolution radar images from the Magellan spacecraft have revealed the first details of the morphology of the Lavinia Planitia region of Venus. Lavinia is a broad lowland over 2000 km across, centered at about 45 deg S latitude, 345 deg E longitude. Herein, the tectonic evolution of Lavinia is discussed, and its possible relationship to processes operating in the planet's interior. The discussion is restricted to the region from 37.3 to 52.6 deg S latitude and from about 340 to 0 deg E longitude. One of the most interesting characteristics of Lavinia is that the entire region possesses a regional tectonic framework of striking regularity. Lavinia is also transected by a complex pattern of belts of intense tectonic deformation known as ridge belts. Despite the gross topographic similarity of all of the ridge belts in Lavinia, they exhibit two rather distinct styles of near surface deformation. One is composed of sets of broad, arch-like ridges rising above the surrounding plains. In the other type, obvious fold-like ridges are rare to absent in the radar images. Both type show evidence for small amounts of shear distributed across the belts.

  16. Variability of dayside electron temperature at Venus

    Science.gov (United States)

    Mahajan, K. K.; Ghosh, S.; Paul, R.; Hoegy, W. R.

    1994-01-01

    Langmuir probe measurements on Pioneer Venus Orbiter show that electron temperature (Te) profiles exhibit two distinct regions. The lower, but more extended region is in the main ionosphere where Te increases slowly with altitude. The other, less extended region is in the ionopause, where Te rise sharply with altitude. If horizontal magnetic fields and flux ropes in the ionosphere inhibit vertical thermal conductivity sufficiently, then the observed Te profile could be explained with EUV as the major heat source (Cravens et al., 1980). The rise in Te in the ionopause region has generally been attributed to solar wind heating (Brace and Kliore, 1991). We suggest that this sharp rise in Te is due primarily to the steep fall in electron density, Ne. If the heating rate is essentially unchanged and heat conduction is not of primary importance, then a steep rise in Te will maintain a constant electron cooling rate for a steeply falling Ne. We have observed large orbit to orbit variations in Te in the ionopause region which are found to be inversely related to changes in Ne. Variations in solar wind dynamic pressure do not seem to have a direct effect on Te, rather the effect is indirect coming through the sharp decrease in Ne.

  17. Poludnista Dorsa, Venus: History and context of a deformation belt

    Science.gov (United States)

    Young, D. A.; Hansen, V. L.

    2005-03-01

    Rolling lowlands comprise 80% of Venus's surface, and thus developing a geological understating of resurfacing and tectonism is critical for our understanding of Venus' evolution. In this paper, global, regional, and local approaches to interpreting Magellan synthetic aperture radar and altimetry radar data are used to constrain modes of lowland evolution, convection processes, and lithospheric structure. Detailed geologic mapping is combined with altimetry data test models of deformation belt evolution in Venus's lowlands. Poludnista Dorsa, a complex 2000-km-long deformation belt, is highly segmented and broadly time transgressive. Long-wavelength deformation is spatially independent of local short-wavelength deformation within the deformation belt and temporally predates regional deformation marked by wrinkle ridges. A mechanically layered lithosphere of regional extent is not required by the local geologic history; local lithospheric thinning or progressive regional thickening of the mechanical layer better explains the observed sequence of events.

  18. Venus Aerosol Properties from Modelling and Akatsuki IR2 Observations

    Science.gov (United States)

    McGouldrick, K.

    2017-09-01

    I am creating computer simulations of the clouds of Venus. In these simulations, I make changes to the properties of the aerosols that affect their ability to form, grow, evaporate, or combine with other particles. I then use the results of these models to predict how bright or dark Venus might appear when viewed at infrared wavelengths. By comparing this calculated brightness with the infrared observations made by the IR2 infrared camera on the Akatsuki spacecraft (currently orbiting Venus since its arrival in December 2015, built by the Japan Aerospace Exploration Agency (JAXA)), I hope to explain the causes for the changes that are seen to occur in the clouds via these and other images.

  19. Emplacement of Antarctic ice sheet mass affects circumpolar ocean flow

    NARCIS (Netherlands)

    Rugenstein, Maria; Stocchi, Paolo; von der Heydt, Anna; Dijkstra, Hendrik; Brinkhuis, Henk

    2014-01-01

    During the Cenozoic the Antarctic continent experienced large fluctuations in ice-sheet volume. We investigate the effects of Glacial Isostatic Adjustment (GIA) on Southern Ocean circulation for the first continental scale glaciation of Antarctica (~34 Myr) by combining solid Earth and ocean dynamic

  20. Emplacement of Antarctic ice sheet mass affects circumpolar ocean flow

    NARCIS (Netherlands)

    Rugenstein, M.; Stocchi, P.; van der Heydt, A.; Brinkhuis, H.

    2014-01-01

    During the Cenozoic the Antarctic continent experienced large fluctuations in ice-sheet volume. We investigate the effects of Glacial Isostatic Adjustment (GIA) on Southern Ocean circulation for the first continental scale glaciation of Antarctica (~ 34 Myr) by combining solid Earth and ocean

  1. The role of ice sheets in the pleistocene climate

    NARCIS (Netherlands)

    Oerlemans, J.

    1991-01-01

    Northern hemisphere ice sheets have played an important role in the climatic evolution of the Pleistocene. The characteristic time-scale of icesheet growth has the same order-of-magnitude as that for the orbital insolation variations. The interaction with the solid earth, the importance of the

  2. Rubella - Fact Sheet for Parents

    Science.gov (United States)

    ... and 4 through 6 years Fact Sheet for Parents Color [2 pages] Español: Rubéola The best way ... according to the recommended schedule. Fact Sheets for Parents Diseases and the Vaccines that Prevent Them Chickenpox ...

  3. Cupid's Arrow: An Innovative Nanosat to Sample Venus' Upper Atmosphere

    Science.gov (United States)

    Bienstock, Bernie; Darrach, Murray; Madzunkov, Stojan; Sotin, Christophe

    2016-01-01

    In NASA's Discovery 2014 AO, the opportunity to propose a Technology Demonstration Opportunity (TDO) to enhance the primary mission was specified. For the Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy (VERITAS) mission, we elected to include the Cupid's Arrow nanosat TDO to sample and measure the abundances of noble gases and their isotopic ratios in Venus's upper atmosphere below the homopause. This paper will provide a basic overview of the VERITAS mission, with a focus on the Cupid's Arrow concept including a description of the mission, spacecraft design, and JPL's quadrupole ion trap mass spectrometer (QITMS) instrument specifications and design. In previous planetary entry probe mission designs, particularly at Venus, engineers w ere focused on entry and descent. A landed probe was also proposed for the New Frontiers SAGE mission. For Cupid's Arrow, the nanosat is designed to skim through the upper atmosphere, just below the homopause, in order to sample the atmosphere, perform the analysis, and then exit the atmosphere to transmit its data to the orbiting VERITAS spacecraft. Cupid's Arrow is a compelling addition to the VERITAS geology mission. A key missing link in our understanding of Venus' evolution is the noble gas abundances and their isotopic ratios. Not since Pioneer Venus have these measurements been made in the Venus atmosphere and never in the upper atmosphere, just below the homopause, to the degree of accuracy that will be accomplished by VERITAS' Cupid's Arrow nanosat.Such measurements were ranked as the number 1 investigation of the number 1 objective of the goal "Atmospheric Formation, Evolution, and Climate History ".

  4. Possible Signs of Fauna and Flora on Venus

    Science.gov (United States)

    Ksanfomality, Leonid V.; Selivanov, Arnold S.; Gektin, Yuryi M.

    2015-08-01

    Habitability of planets is a fundamental question of science. Some of exoplanets possess physical conditions close to those of Venus. The planet Venus, despite its dense and hot (735 K) oxygen-free atmosphere of CO2, having a high pressure of 9.2 MPa at the surface, can be a natural laboratory for this kind of studies. The only existing data on the planet’s surface are still the results obtained by the Soviet VENERA landers.The TV experiments of Venera-9 and 10 (October, 1975) and Venera-13 and 14 (March, 1982) delivered 41 panoramas of Venus surface (or their fragments). The experiments were of extreme technical complexity. There have not been any similar missions to Venus in the subsequent 40 and 33 years. In the absence of new landing missions to Venus, the VENERA panoramas have been re-processed by modern means. The results of these missions are studied anew. A dozen of relatively large objects, from a decimeter to half a meter in size, with an unusual morphology have been found which moved very slowly or changed slightly their shape. Certain unusual findings that have a structure similar to the Earth’ fauna and flora were found in different areas of the planet. There are more then 30 papers on the topic published in 2012-2014 (e.g., “Acta Astronautica”, 2014, V. 105, pp. 521-533). Due to the availability of up to eight duplicates of the images obtained and their low level of masking noise, the VENERA archive panoramas permit identifying and exploring some types of hypothetical life forms of Venus. Analysis of treated once again VENERA panoramic images revealed objects that might indicate the presence of about 12 hypothetical forms of Venusian flora and fauna. Among them is ‘amisada’ that stands out with its unusual lizard shape against the stone plates surrounding it.

  5. Targeting the Plains of Venus from Orbit

    Science.gov (United States)

    Sharpton, V. L.

    2014-05-01

    Lowland plains house a spectacular array of poorly understood volcanic, tectonic, and impact features that are key to settling the continuing global stratigraphy debate and resolving how the only other accessible Earth-sized planet has evolved.

  6. Description, accessibility and usage of SOIR/Venus Express atmospheric profiles of Venus distributed in VESPA (Virtual European Solar and Planetary Access)

    Science.gov (United States)

    Trompet, L.; Geunes, Y.; Ooms, T.; Mahieux, A.; Wilquet, V.; Chamberlain, S.; Robert, S.; Thomas, I. R.; Erard, S.; Cecconi, B.; Le Sidaner, P.; Vandaele, A. C.

    2018-01-01

    Venus Express SOIR profiles of pressure, temperature and number densities of different constituents of the mesosphere and lower thermosphere of Venus are the only experimental data covering the 60 km to 220 km range of altitudes at the terminator of Venus. This unique dataset is now available in the open access VESPA infrastructure. This paper describes the content of these data products and provides some use cases.

  7. Resonances and librations of some Apollo and Amor asteroids with the Earth.

    Science.gov (United States)

    Ip, W.-H.; Mehra, R.

    1973-01-01

    The orbital evolution of the Apollo asteroids 1620 Geographos and 1685 Toro and Amor asteroids 433 Eros, 1221 Amor, and 1627 Ivar are investigated by numerical integration. All these asteroids, with the exception of Geographos, exhibit systematic orbital couplings with the Earth during the time interval studied (1600-2350 A.D.). 1685 Toro is captured into libration once with Venus due to the 13.5 resonance, and once with the Earth due to the 8:5 resonance. Both librations are unstable because of the effect of the 13:8 near commensurability of the Venus-Earth system. 433 Eros exhibits no libration pattern; the regular variation of its orbital period is due to the beat-effect of the 4:7 resonance with the Earth.

  8. Martian sand sheet characterization and implications for formation: A case study

    Science.gov (United States)

    Runyon, Kirby D.; Bridges, Nathan T.; Newman, Claire E.

    2017-12-01

    Windblown sand and dust dominate surface geologic processes in Mars' current environment. Besides sand dune fields, areally extensive sand sheets are common across Mars, blanketing the underlying topography with several meters of rippled sand. Earth's sand sheets commonly form upwind or cross-wind to dunes and both partially trap and source sediment to downwind dunes. In contrast, Mars' sheets are frequently located downwind of active barchan and dome sand dunes, suggesting they cannot be a sediment source for the dunes as on Earth. Here, we characterize a Martian sand sheet and its geologic context, model the regional atmospheric circulation, and more broadly consider the implications for sand sheet formation on Mars. Our case study sand sheet in central Herschel Crater is dunes, crater rims, and small hills. The sheet has actively migrating superposing ripples with estimated total sand fluxes comparable to total fluxes measured from slip faces on local, regional, and global dunes, some of which have eroded away. A smooth geologic unit interpreted as outcrops of paleo-sand sheets is adjacent to the active sheets. Our observations and atmospheric modeling-which predict wind shear stresses above the sand suspension threshold-indicate that the upwind dunes may be eroding and their sand deposited downwind in sheets in what may be a cyclical process, possibly related to Mars' axial obliquity cycles.

  9. High Altitude Venus Operations Concept Trajectory Design, Modeling and Simulation

    Science.gov (United States)

    Lugo, Rafael A.; Ozoroski, Thomas A.; Van Norman, John W.; Arney, Dale C.; Dec, John A.; Jones, Christopher A.; Zumwalt, Carlie H.

    2015-01-01

    A trajectory design and analysis that describes aerocapture, entry, descent, and inflation of manned and unmanned High Altitude Venus Operation Concept (HAVOC) lighter-than-air missions is presented. Mission motivation, concept of operations, and notional entry vehicle designs are presented. The initial trajectory design space is analyzed and discussed before investigating specific trajectories that are deemed representative of a feasible Venus mission. Under the project assumptions, while the high-mass crewed mission will require further research into aerodynamic decelerator technology, it was determined that the unmanned robotic mission is feasible using current technology.

  10. The electric wind of Venus: A global and persistent "polar wind"-like ambipolar electric field sufficient for the direct escape of heavy ionospheric ions

    Science.gov (United States)

    Collinson, Glyn A.; Frahm, Rudy A.; Glocer, Alex; Coates, Andrew J.; Grebowsky, Joseph M.; Barabash, Stas; Domagal-Goldman, Shawn D.; Fedorov, Andrei; Futaana, Yoshifumi; Gilbert, Lin K.; Khazanov, George; Nordheim, Tom A.; Mitchell, David; Moore, Thomas E.; Peterson, William K.; Winningham, John D.; Zhang, Tielong L.

    2016-06-01

    Understanding what processes govern atmospheric escape and the loss of planetary water is of paramount importance for understanding how life in the universe can exist. One mechanism thought to be important at all planets is an "ambipolar" electric field that helps ions overcome gravity. We report the discovery and first quantitative extraterrestrial measurements of such a field at the planet Venus. Unexpectedly, despite comparable gravity, we show the field to be five times stronger than in Earth's similar ionosphere. Contrary to our understanding, Venus would still lose heavy ions (including oxygen and all water-group species) to space, even if there were no stripping by the solar wind. We therefore find that it is possible for planets to lose heavy ions to space entirely through electric forces in their ionospheres and such an "electric wind" must be considered when studying the evolution and potential habitability of any planet in any star system.

  11. The Electric Wind of Venus: A global and persistent "polar wind" like ambipolar electric field sufficient for the direct escape of heavy ionospheric ions

    Science.gov (United States)

    Collinson, G.; Frahm, R.; Glocer, A.; Coates, A. J.; Grebowsky, J. M.; Barbash, S.; Fedorov, A.; Futaana, Y.; Gilbert, L.; Khazanov, G. V.; Domagal-Goldman, S. D.; Nordheim, T.; Mitchell, D. L.; Moore, T. E.; Peterson, W.; Winningham, D.; Zhang, T.

    2016-12-01

    Understanding what processes govern atmospheric escape and the loss of planetary water is of paramount importance for understanding how life in the universe can exist. One mechanism thought to be important at all planets is an "ambipolar" electric field that helps ions overcome gravity. We report the discovery and first quantitative extraterrestrial measurements of such a field at the planet Venus. Unexpectedly, despite comparable gravity, we show the field to be five times stronger than in Earth's similar ionosphere. Contrary to our understanding, Venus would still lose heavy ions (including oxygen and all water-group species) to space, even if there were no stripping by the solar wind. We therefore find it is possible for planets to lose heavy ions to space entirely through electric forces in their ionospheres, and such an "electric wind" must be considered when studying the evolution and potential habitability of any planet in any star system

  12. The Electric Wind of Venus: A Global and Persistent Polar Wind -Like Ambipolar Electric Field Sufficient for the Direct Escape of Heavy Ionospheric Ions

    Science.gov (United States)

    Collinson, Glyn A.; Frahm, Rudy A.; Glocer, Alex; Coates, Andrew J.; Grebowsky, Joseph M.; Barabash, Stas; Domagal-Goldman, Shawn D.; Federov, Andrei; Futaana, Yoshifumi; Gilbert, Lin K.; hide

    2016-01-01

    Understanding what processes govern atmospheric escape and the loss of planetary water is of paramount importance for understanding how life in the universe can exist. One mechanism thought to be important at all planets is an ambipolar electric field that helps ions overcome gravity. We report the discovery and first quantitative extraterrestrial measurements of such a field at the planet Venus. Unexpectedly, despite comparable gravity, we show the field to be five times stronger than in Earths similar ionosphere. Contrary to our understanding, Venus would still lose heavy ions (including oxygen and all water-group species) to space, even if there were no stripping by the solar wind. We therefore find that it is possible for planets to lose heavy ions to space entirely through electric forces in their ionospheres and such an electric wind must be considered when studying the evolution and potential habitability of any planet in any star system.

  13. Aerobraking at Venus: A science and technology enabler

    Science.gov (United States)

    Hibbard, Kenneth; Glaze, Lori; Prince, Jill

    2012-04-01

    Venus remains one of the great unexplored planets in our solar system, with key questions remaining on the evolution of its atmosphere and climate, its volatile cycles, and the thermal and magmatic evolution of its surface. One potential approach toward answering these questions is to fly a reconnaissance mission that uses a multi-mode radar in a near-circular, low-altitude orbit of ∼400 km and 60-70° inclination. This type of mission profile results in a total mission delta-V of ∼4.4 km/s. Aerobraking could provide a significant portion, potentially up to half, of this energy transfer, thereby permitting more mass to be allocated to the spacecraft and science payload or facilitating the use of smaller, cheaper launch vehicles.Aerobraking at Venus also provides additional science benefits through the measurement of upper atmospheric density (recovered from accelerometer data) and temperature values, especially near the terminator where temperature changes are abrupt and constant pressure levels drop dramatically in altitude from day to night.Scientifically rich, Venus is also an ideal location for implementing aerobraking techniques. Its thick lower atmosphere and slow planet rotation result in relatively more predictable atmospheric densities than Mars. The upper atmosphere (aerobraking altitudes) of Venus has a density variation of 8% compared to Mars' 30% variability. In general, most aerobraking missions try to minimize the duration of the aerobraking phase to keep costs down. These short phases have limited margin to account for contingencies. It is the stable and predictive nature of Venus' atmosphere that provides safer aerobraking opportunities.The nature of aerobraking at Venus provides ideal opportunities to demonstrate aerobraking enhancements and techniques yet to be used at Mars, such as flying a temperature corridor (versus a heat-rate corridor) and using a thermal-response surface algorithm and autonomous aerobraking, shifting many daily ground

  14. Single sheet iron oxides

    DEFF Research Database (Denmark)

    Yin, Zhou

    activity. LDH single sheets have been reported to be effective sorbents, catalysts in electrochemical and photochemical reactions, and building thin films together with other nanomaterials for designing new functionalities. Here we focus on the delamination of FeII-FeIII LDHs into single sheet iron oxide...... was rapid compared to other iron oxides, reaching equilibrium within 60 minutes. Arsenic sorption and acid-base titration data could be successfully described with a 1pk Basic Stern Model (BSM). The point of zero charge was around 8. The intrinsic surface complexation equilibrium constants (log K...... became abundant at low pH. (3) Electrochemical reduction of chlorinated compounds using an SSI modified electrode. Here, the electrochemical reactivity of SSIs coated on indium tin oxide coated glass electrodes was investigated. Iron on the SSI modified electrode showed a typical Cyclic Voltammetry...

  15. Film sheet cassette

    International Nuclear Information System (INIS)

    1981-01-01

    A novel film sheet cassette is described for handling CAT photographic films under daylight conditions and facilitating their imaging. A detailed description of the design and operation of the cassette is given together with appropriate illustrations. The resulting cassette is a low-cost unit which is easily constructed and yet provides a sure light-tight seal for the interior contents of the cassette. The individual resilient fingers on the light-trap permit the ready removal of the slide plate for taking pictures. The stippled, non-electrostatic surface of the pressure plate ensures an air layer and free slidability of the film for removal and withdrawal of the film sheet. The advantage of the daylight system is that a darkroom need not be used for inserting and removing the film in and out of the cassette resulting in a considerable time saving. (U.K.)

  16. Biomolecular Science (Fact Sheet)

    Energy Technology Data Exchange (ETDEWEB)

    2012-04-01

    A brief fact sheet about NREL Photobiology and Biomolecular Science. The research goal of NREL's Biomolecular Science is to enable cost-competitive advanced lignocellulosic biofuels production by understanding the science critical for overcoming biomass recalcitrance and developing new product and product intermediate pathways. NREL's Photobiology focuses on understanding the capture of solar energy in photosynthetic systems and its use in converting carbon dioxide and water directly into hydrogen and advanced biofuels.

  17. Information sheets on energy

    International Nuclear Information System (INIS)

    2004-01-01

    These sheets, presented by the Cea, bring some information, in the energy domain, on the following topics: the world energy demand and the energy policy in France and in Europe, the part of the nuclear power in the energy of the future, the greenhouse gases emissions and the fight against the greenhouse effect, the carbon dioxide storage cost and the hydrogen economy. (A.L.B.)

  18. Physical conditions on the early Earth

    Science.gov (United States)

    Lunine, Jonathan I

    2006-01-01

    The formation of the Earth as a planet was a large stochastic process in which the rapid assembly of asteroidal-to-Mars-sized bodies was followed by a more extended period of growth through collisions of these objects, facilitated by the gravitational perturbations associated with Jupiter. The Earth's inventory of water and organic molecules may have come from diverse sources, not more than 10% roughly from comets, the rest from asteroidal precursors to chondritic bodies and possibly objects near Earth's orbit for which no representative class of meteorites exists today in laboratory collections. The final assembly of the Earth included a catastrophic impact with a Mars-sized body, ejecting mantle and crustal material to form the Moon, and also devolatilizing part of the Earth. A magma ocean and steam atmosphere (possibly with silica vapour) existed briefly in this period, but terrestrial surface waters were below the critical point within 100 million years after Earth's formation, and liquid water existed continuously on the surface within a few hundred million years. Organic material delivered by comets and asteroids would have survived, in part, this violent early period, but frequent impacts of remaining debris probably prevented the continuous habitability of the Earth for one to several hundred million years. Planetary analogues to or records of this early time when life began include Io (heat flow), Titan (organic chemistry) and Venus (remnant early granites). PMID:17008213

  19. Kinetic Studies of Thin Current Sheets at Magnetosheath Jets

    Science.gov (United States)

    Eriksson, E.; Vaivads, A.; Khotyaintsev, Y. V.; Graham, D. B.; Yordanova, E.; Hietala, H.; Markidis, S.; Giles, B. L.; Andre, M.; Russell, C. T.; Le Contel, O.; Burch, J. L.

    2017-12-01

    In near-Earth space one of the most turbulent plasma environments is the magnetosheath (MSH) downstream of the quasi-parallel shock. The particle acceleration and plasma thermalization processes there are still not fully understood. Regions of strong localized currents are believed to play a key role in those processes. The Magnetospheric Multiscale (MMS) mission has sufficiently high cadence to study these processes in detail. We present details of studies of two different events that contain strong current regions inside the MSH downstream of the quasi-parallel shock. In both cases the shape of the current region is in the form of a sheet, however they show internal 3D structure on the scale of the spacecraft separation (15 and 20 km, respectively). Both current sheets have a normal magnetic field component different from zero indicating that the regions at the different sides of the current sheets are magnetically connected. Both current sheets are boundaries between two different plasma regions. Furthermore, both current sheets are observed at MSH jets. These jets are characterized by localized dynamic pressure being larger than the solar wind dynamic pressure. One current sheet does not seem to be reconnecting while the other shows reconnection signatures. Inside the non-reconnecting current sheet we observe locally accelerated electron beams along the magnetic field. At energies above the beam energy we observe a loss cone consistent with part of the hot MSH-like electrons escaping into the colder solar wind-like plasma. This suggests that the acceleration process within this current sheet is similar to the one that occurs at the bow shock, where electron beams and loss cones are also observed. Therefore, we conclude that electron beams observed in the MSH do not have to originate from the bow shock, but can also be generated locally inside the MSH. The reconnecting current sheet also shows signs of thermalization and electron acceleration processes that are

  20. Technology development for long-lived Venus landers.

    Science.gov (United States)

    Ekonomov, 1.; Korablev, O.; Zasova, L.

    2007-08-01

    Simultaneously with many successful lander missions on Venus in 1972-1985 Soviet Union began develop long-lived lander on surface of Venus. The basic problem were extreme conditions on a surface: P=10MPa, T=500 C . Then operations have been stopped and have renewed in 2006 already in new Russia. Mission "VENERA (VENUS) - D" is included into the Federal space program of Russia on 2006 - 2015 with launch in 2016. To this date Russia alone can't create a reliable electronics for 500 C, but we have got examples GaN electronics for 350 C. Cooling technology with boiling water is offered for interior devices of lander at pressure 10 MPa and temperature 310 C. As the power source of an electronics we use high-temperature galvanic cells on the base of Li4Si [LiCl, KCl, LiF] FeS2 which are released in Russia as reserve power sources. They are capable to work directly on a surface of Venus without any thermal protection. At lander two kinds of vacuum technology can be used: 1) in multilayer (MLI ) thermal blanket for lander, 2) in electro-vacuum devices, for example transmitter . For creation and maintenance of vacuum at temperature 400-500 C: chemical gas absorbers ( getter materials ) are used, they actively absorb both carbon dioxide and nitrogen .

  1. Venus Transit 2004, A New Experiment For Education And Communication

    Science.gov (United States)

    Stavinschi, M.; Mioc, V.; Maris, G.

    On June 8, 2004, the Venus transit in front of the Sun took place. It was a rare astronomical phenomenon, because the last Venus transit took place in 1882 and was only partially visible in Europe. Such a rare phenomenon mobilized all who are curious about the sky, but it also was a good opportunity for specialists to spread some knowledge about the universe in public. IAAR adhered to the International Consortium Venus-2004 acting as a National Node. The Romanian researchers in astronomy, together with the amateur astronomers and teachers, set up an ambitious national programme addressed to the school young people as well as to the public. National meetings and conferences, activities for informing the public, contests with astronomical subjects for children were organised in order to make known the Venus transit event. Organisms with large impact on the public (mass media) and even factors of decision were contacted in order to get a correct understanding of the phenomenon. We try to show here how a such a event become a new experiment for education and communication, ending with some particular conclusions.

  2. Ribbon terrain formation and implications for lithosphere evolution, Venus

    Science.gov (United States)

    Hansen, V. L.; Willis, J. J.

    1997-03-01

    Venus terrain ribbons comprise a fabric of alternating, parallel, closely-spaced, radar-dark/bright lineaments showing a distinct dark-bright pairing. It is presently argued that the opening of tensile fractures within a brittle layer above a sharp brittle ductile transition over a ductile substrate can account for the formation of the observed geometric characteristics of ribbon terrain.

  3. Results of Equilibrium Resurfacing Monta Carlo Models on Venus

    Science.gov (United States)

    Bjonnes, E. E.; Hansen, V. L.; Swenson, J. B.

    2008-03-01

    Previous equilibrium resurfacing tests failed to include increments between 10 and 0.03%. We tested this parameter space and found that there is no statistical evidence that equilibrium resurfacing cannot meet the two key observations of Venus' impact crater data set.

  4. Plant Physiology: The Venus Flytrap Counts on Secretion.

    Science.gov (United States)

    Brownlee, Colin

    2017-08-07

    The Venus flytrap effectively detects, traps, digests and absorbs insect prey. A recent study links the mechanical stimulation of sensory hair cells with short- and long-term signalling giving rise to different downstream secretion events that bring about conditions for prey digestion. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Transit of Venus: Quantitative Observing with Simple Equipment

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 17; Issue 5. Transit of Venus: Quantitative Observing with Simple Equipment. N Rathnasree Pritpal Kaur. Classroom Volume 17 Issue 5 May 2012 pp 497-504. Fulltext. Click here to view fulltext PDF. Permanent link:

  6. Cleopatra Crater, a Circular Portal to the Soul of Venus

    Science.gov (United States)

    Herrick, R. R.

    2014-05-01

    Cleopatra is on the flanks of Maxwell Montes, the tallest mountain range on Venus. Inside the peak ring is a 60-km wide, flat area that represents a relatively safe area to obtain a sample of tessera, plus the geology of the area is important.

  7. Venus näitas lillekleite / Regina Hansen

    Index Scriptorium Estoniae

    Hansen, Regina

    2001-01-01

    Sunflower Beauty Contest esitles ööklubis Venus eluslilledest valmistatud kleite. Parimaks tunnistati kaupluse Annilill floristid tööga "My Bunny", teiseks tunnistati Katrin Pedaru ja Ninell Soosaare "C'est la vie", kolmanda koha pälvis Karina Saberi töö "Unistus"

  8. Introduction to the special issue on Venus exploration

    Science.gov (United States)

    Svedhem, H.; Wilson, C.; Piccioni, G.

    2015-08-01

    Venus Express ended its mission in December 2014 after an extraordinary successful eight and a half years at Venus. The first years of the mission concentrated on the original objectives of the mission, namely to study the dynamics, structure and chemistry of the atmosphere, to investigate the plasma environment and its interaction with the solar wind, and to study certain topics of the surface and the surface atmosphere interaction. The latter part of the mission was focussing on dedicated campaigns for the study of specific topics, often in coordination with ground based observations. The highly elliptical polar orbit permitted a study of all latitudes, particularly of the polar regions. The optimised payload and orbit of the mission, together with the systematic and long-term observations of the atmosphere has enabled a wealth of data to be analysed. It has already resulted in many exciting new findings and a significantly improved understanding of Venus, even if only a part of the data has been analysed so far. In the last year of the mission a two month long aerobraking campaign was performed, resulting in a valuable data set on the structure of the atmosphere down to below 130 km - a region difficult to sample with remote techniques, before the fuel ran out at the end of November 2014. This campaign also provided a lot of engineering and operational experience, useful for future missions that may use aerobraking techniques at Venus or other planets.

  9. The 1761 discovery of Venus' atmosphere: Lomonosov and others

    Science.gov (United States)

    Shiltsev, Vladimir

    2014-03-01

    Russian polymath Mikhail Vasil'evich Lomonosov claimed to have discovered the atmosphere of Venus during the planet's transit over the Sun's disc in 1761. Although several other astronomers observed similar effects during the 1761 and 1769 transits, Lomonosov's claim for priority is the strongest as he was the first to publish a comprehensive scientific report, and the first to offer a detailed explanation of the aureole around Venus at ingress and egress, which was caused by refraction of the sunlight through Venus' atmosphere. His observations, moreover, were successfully reconstructed experimentally using antique telescopes during the 2012 transit. In this paper we review details of Lomonosov's observations (which usually are poorly covered by commentators and often misunderstood); compare other reports of the eighteenth century transit observations, and summarize their findings in a comprehensive table; and address recent calls to reconsider Lomonosov's priority. After reviewing the available documentation we conclude that everything we learned before, during and after the twenty-first century transits only supports further the widely-accepted attribution of the discovery of Venus' atmosphere to Lomonosov.

  10. Evidences for recent plume-induced subduction, microplates and localized lateral plate motions on Venus

    Science.gov (United States)

    Davaille, Anne; Smrekar, Suzanne

    2017-04-01

    Using laboratory experiments and theoretical modeling, we recently showed that plumes could induce roll-back subduction around large coronae. When a hot plume rises under a brittle and visco-elasto-plastic skin/lithosphere, the latter undergoes a flexural deformation which puts it under tension. Radial cracks and rifting of the skin then develop, sometimes using pre-existing weaknesses. Plume material upwells through the cracks (because it is more buoyant) and spreads as a axisymmetric gravity current above the broken denser skin. The latter bends and sinks under the combined force of its own weight and that of the plume gravity current. However, due to the brittle character of the upper part of the experimental lithosphere, it cannot deform viscously to accomodate the sinking motions. Instead, the plate continues to tear, as a sheet of paper would do upon intrusion. Several slabs are therefore produced, associated with trenches localized along partial circles on the plume, and strong roll-back is always observed. Depending on the lithospheric strength, roll-back can continue and triggers a complete resurfacing, or it stops when the plume stops spreading. Two types of microplates are also observed. First, the upwelling plume material creates a set of new plates interior to the trench segments. These plates move rapidly and expand through time, but do not subduct.. In a few cases, we also observe additional microplates exterior to the trenches. This happens when the subducting plate contains preexisting heterogeneities (e.g. fractures) and the subducted slab is massive enough for slab pull to become efficient and induce horizontal plate motions. Scalings derived from the experiments suggest that Venus lithosphere is soft enough to undergo such a regime. And indeed, at least two candidates can be identified on Venus, where plume-induced subduction could have operated. (1) Artemis Coronae is the largest (2300 km across) coronae on Venus and is bounded over 270° of

  11. Annual review of earth and planetary sciences. Volume 16

    Science.gov (United States)

    Wetherill, George W.; Albee, Arden L.; Stehli, Francis G.

    Various papers on earth and planetary science topics are presented. The subjects addressed include: role and status of earth science field work; phase relations of prealuminous granitic rocks and their petrogenetic implications; chondritic meteorites and the solar nebula; volcanic winters; mass wasting on continental margins; earthquake ground motions; ore deposits as guides to geologic history of the earth; geology of high-level nuclear waste disposal; and tectonic evolution of the Caribbean. Also discussed are: the earth's rotation; the geophysics of a restless caldera (Long Valley, California); observations of cometary nuclei; geology of Venus; seismic stratigraphy; in situ-produced cosmogenic isotopes in terrestrial rocks; time variations of the earth's magnetic field; deep slabs, geochemical heterogeneity, and the large-scale structure of mantle convection; early proterozoic assembly and growth of Laurentia; concepts and methods of high-resolution event stratigraphy.

  12. Search for HBr and bromine photochemistry on Venus

    Science.gov (United States)

    Krasnopolsky, Vladimir A.; Belyaev, Denis A.

    2017-09-01

    HBr (1-0) R2 2605.8/6.2 cm-1, the strongest line of the strongest band of HBr, was observed when searching for this species on Venus. The observation was conducted using the NASA IRTF and a high-resolution long-slit spectrograph CSHELL with resolving power of 4 × 104. 101 spectra of Venus were analyzed, and the retrieved HBr abundances varied from -8 to + 5 ppb. Their mean value is -1.2 ppb, standard deviation is 2.5 ppb, and uncertainty of the mean is 0.25 ppb. The negative value presumes a systematic error, and the estimated upper limit of the HBr mixing ratio at the cloud tops of Venus is ∼1 ppb. From the simultaneously retrieved CO2 abundances, this corresponds to an altitude of 78 km for the uniform distribution of HBr. A simplified version of the bromine photochemistry is included into the photochemical model (Krasnopolsky 2012, Icarus 218, 230-246). Photolysis of HBr and its reactions with O and H deplete the HBr mixing ratio at 70-80 km relative to that below 60 km by a factor of ≈300. Reanalysis of the observational data with the calculated profile of HBr gives an upper limit of 20-70 ppb for HBr below 60 km and the aerosol optical depth of 0.7 at 70 km and 3.84 μm. The bromine chemistry may be effective on Venus even under the observed upper limit. However, if a Cl/Br ratio in the Venus atmosphere is similar to that in the Solar System, then HBr is ≈1 ppb in the lower atmosphere and the bromine chemistry is insignificant. Thermodynamic calculations based on the chemical kinetic model (Krasnopolsky 2013, Icarus 225, 570-580) predict HBr as a major bromine species in the lower atmosphere.

  13. Ice sheet growth with laterally varying bedrock relaxation time

    Science.gov (United States)

    van der Wal, Wouter; Vizcaino Rubio, Pablo; De Boer, Bas; van de Wal, Roderik

    2017-04-01

    Isostatic response of the bedrock, or glacial isostatic adjustment (GIA) in included in most ice sheet models. This is important because the surface elevation determines the mass balance and thereby implicitly also the strength of the mass balance feedback where higher surface elevation yields lower temperatures implying less melt and vice versa. Usually a single relaxation time or a set of relaxation times is used to model the response everywhere on Earth or at least for an entire ice sheet. In reality the viscosity in the Earth's mantle, and hence the relaxation time experienced by the ice, varies with location. Seismic studies indicate that several regions that were covered by ice during the last glacial cycle are underlain by mantle in which viscosity varies with orders of magnitude, such as Antarctica and North America. The question is whether such a variation of viscosity influences ice evolution. Several GIA models exist that can deal with 3D viscosity, but their large computation times make it nearly impossible to couple them to ice sheet models. Here we use the ANICE ice-sheet model (de Boer et al. 2013) with a simple bedrock-relaxation model in which a different relaxation time is used for separate regions. A temperature anomaly is applied to grow a schematic ice sheet on a flat earth, with other forcing mechanisms neglected. It is shown that in locations with a fast relaxation time of 300 years the equilibrium ice sheet is significantly thinner and narrower but also ice thickness in neighbouring regions (with the more standard relaxation time of 3000 years) is affected.

  14. Dense sheet Z-pinches

    International Nuclear Information System (INIS)

    Tetsu, Miyamoto

    1999-01-01

    The steady state and quasi-steady processes of infinite- and finite-width sheet z-pinches are studied. The relations corresponding to the Bennett relation and Pease-Braginskii current of cylindrical fiber z-pinches depend on a geometrical factor in the sheet z-pinches. The finite-width sheet z-pinch is approximated by a segment of infinite-width sheet z-pinch, if it is wide enough, and corresponds to a number of (width/thickness) times fiber z-pinch plasmas of the diameter that equals the sheet thickness. If the sheet current equals this number times the fiber current, the plasma created in the sheet z-pinches is as dense as in the fiber z-pinches. The total energy of plasma and magnetic field per unit mass is approximately equal in both pinches. Quasi-static transient processes are different in several aspects from the fiber z-pinch. No radiation collapse occurs in the sheet z-pinch. The stability is improved in the sheet z-pinches. The fusion criterions and the experimental arrangements to produce the sheet z-pinches are also discussed. (author)

  15. Lithospheric flexure beneath the Freyja Montes Foredeep, Venus: Constraints on lithospheric thermal gradient and heat flow

    International Nuclear Information System (INIS)

    Solomon, S.C.; Head, J.W.

    1990-01-01

    Analysis of Venera 15 and 16 radar images and topographic data from the Freyja Montes region on Venus suggest that this mountain belt formed as a result of a sequence of underthrusts of the lithosphere of the North Polar Plains beneath the highlands of Ishtar Terra. The Freyja Montes deformation zone consists, south to north, of a linear orogenic belt, an adjacent plateau, a steep scarp separating the plateau from the North Polar Plains, a linear depression at the base of the scarp, and an outer rise. The topographic profile of the depression and outer rise are remarkably similar to that of a foreland deep and rise formed by the flexure of the underthrusting plate beneath a terrestrial mountain range. The authors test the lithospheric flexure hypothesis and they estimate the effective thickness T e of the elastic lithosphere of the underthrusting portion of the North Polar Plains by fitting individual topographic profiles to deflection curves for a broken elastic plate. The theoretical curves fit the observed topographic profiles to within measurement error for values of flexural rigidity D in the range (0.8-3) x 10 22 N m, equivalent to T e in the range 11-18 km. Under the assumption that the base of the mechanical lithosphere is limited by the creep strength of olivine, the mean lithospheric thermal gradient is 14-23 K/km. That the inferred thermal gradient is similar to the value expected for the global mean gradient on the basis of scaling from Earth provides support for the hypothesis that simple conduction dominates lithospheric heat transport on Venus relative to lithospheric recycling and volcanism

  16. The Greenland Ice Sheet Monitoring Network (GLISN)

    Science.gov (United States)

    Anderson, K. R.; Beaudoin, B. C.; Butler, R.; Clinton, J. F.; Dahl-Jensen, T.; Ekstrom, G.; Giardini, D.; Govoni, A.; Hanka, W.; Kanao, M.; Larsen, T.; Lasocki, S.; McCormack, D. A.; Mykkeltveit, S.; Nettles, M.; Agostinetti, N. P.; Stutzmann, E.; Tsuboi, S.; Voss, P.

    2010-12-01

    The GreenLand Ice Sheet monitoring Network (GLISN) is an international, broadband seismic capability for Greenland, being installed and implemented through the collaboration of Denmark, Canada, Germany, Italy, Japan, Norway, Poland, Switzerland, and USA. GLISN is a real-time sensor array of seismic stations to enhance and upgrade the performance of the sparse Greenland seismic infrastructure for detecting, locating, and characterizing glacial earthquakes and other cryo-seismic phenomena, and contributing to our understanding of Ice Sheet dynamics. Complementing data from satellites, geodesy, and other sources, and in concert with these technologies, GLISN will provide a powerful tool for detecting change, and will advance new frontiers of research in the glacial systems; the underlying geological and geophysical processes affecting the Greenland Ice Sheet; interactions between oceans, climate, and the cryosphere; and other multidisciplinary areas of interest to geoscience and climate dynamics. The glacial processes that induce seismic events (internal deformation, sliding at the base, disintegration at the calving front, drainage of supra-glacial lakes) are all integral to the overall dynamics of glaciers, and seismic observations of glaciers therefore provide a quantitative means for monitoring changes in their behavior over time. Long-term seismic monitoring of the Greenland Ice Sheet will contribute to identifying possible unsuspected mechanisms and metrics relevant to ice sheet collapse, and will provide new constraints on Ice Sheet dynamic processes and their potential roles in sea-level rise during the coming decades. GLISN will provide a new, fiducial reference network in and around Greenland for monitoring these phenomena in real-time, and for the broad seismological study of Earth and earthquakes. The 2010 summer field season saw the installation or upgrade of 9 stations in the GLISN network. Sites visited under the GLISN project include Station Nord (NOR

  17. Large-scale Modeling of the Greenland Ice Sheet on Long Timescales

    DEFF Research Database (Denmark)

    Solgaard, Anne Munck

    this threshold towards colder temperatures in line with a recent study, but the new threshold value depends on the choice of method. It was found using the adaptive patterns that the Greenland ice sheet can reform under present-day conditions. A further study where additional coupling between the ice-sheet model...... is investigated as well as its early history. The studies are performed using an ice-sheet model in combination with relevant forcing from observed and modeled climate. Changes in ice-sheet geometry influences atmospheric flow (and vice versa) hereby changing the forcing patterns. Changes in the overall climate...... for the build-up of the Greenland ice sheet that lead to the intensification of the Northern Hemisphere glaciations at the end of the Pliocene. A study of output from the climate model, EC-EARTH, reveals some of the challenges faced when using this to force ice-sheet evolution or when full coupling of ice...

  18. Experiments on sheet metal shearing

    OpenAIRE

    Gustafsson, Emil

    2013-01-01

    Within the sheet metal industry, different shear cutting technologies are commonly used in several processing steps, e.g. in cut to length lines, slitting lines, end cropping etc. Shearing has speed and cost advantages over competing cutting methods like laser and plasma cutting, but involves large forces on the equipment and large strains in the sheet material.Numerical models to predict forces and sheared edge geometry for different sheet metal grades and different shear parameter set-ups a...

  19. Sensitivity of Pliocene ice sheets to orbital forcing

    Science.gov (United States)

    Dolan, A.M.; Haywood, A.M.; Hill, D.J.; Dowsett, H.J.; Hunter, S.J.; Lunt, D.J.; Pickering, S.J.

    2011-01-01

    The stability of the Earth's major ice sheets is a critical uncertainty in predictions of future climate and sea level change. One method of investigating the behaviour of the Greenland and the Antarctic ice sheets in a warmer-than-modern climate is to look back at past warm periods of Earth history, for example the Pliocene. This paper presents climate and ice sheet modelling results for the mid-Pliocene warm period (mPWP; 3.3 to 3.0 million years ago), which has been identified as a key interval for understanding warmer-than-modern climates (Jansen et al., 2007). Using boundary conditions supplied by the United States Geological Survey PRISM Group (Pliocene Research, Interpretation and Synoptic Mapping), the Hadley Centre coupled ocean–atmosphere climate model (HadCM3) and the British Antarctic Survey Ice Sheet Model (BASISM), we show large reductions in the Greenland and East Antarctic Ice Sheets (GrIS and EAIS) compared to modern in standard mPWP experiments. We also present the first results illustrating the variability of the ice sheets due to realistic orbital forcing during the mid-Pliocene. While GrIS volumes are lower than modern under even the most extreme (cold) mid-Pliocene orbit (losing at least 35% of its ice mass), the EAIS can both grow and shrink, losing up to 20% or gaining up to 10% of its present-day volume. The changes in ice sheet volume incurred by altering orbital forcing alone means that global sea level can vary by more than 25 m during the mid-Pliocene. However, we have also shown that the response of the ice sheets to mPWP orbital hemispheric forcing can be in anti-phase, whereby the greatest reductions in EAIS volume are concurrent with the smallest reductions of the GrIS. If this anti-phase relationship is in operation throughout the mPWP, then the total eustatic sea level response would be dampened compared to the ice sheet fluctuations that are theoretically possible. This suggests that maximum eustatic sea level rise does not

  20. A simple holistic hypothesis for the self-destruction of ice sheets

    Science.gov (United States)

    Hughes, T.

    2011-07-01

    Ice sheets are the only components of Earth's climate system that can self-destruct. This paper presents the quantitative force balance for bottom-up modeling of ice sheets, as first presented qualitatively in this journal as a way to quantify ice-bed uncoupling leading to self-destruction of ice sheets ( Hughes, 2009a). Rapid changes in sea level and climate can result if a large ice-sheet self-destructs quickly, as did the former Laurentide Ice Sheet of North America between 8100 and 7900 BP, thereby terminating the last cycle of Quaternary glaciation. Ice streams discharge up to 90 percent of ice from past and present ice sheets. A hypothesis is presented in which self-destruction of an ice sheet begins when ubiquitous ice-bed decoupling, quantified as a floating fraction of ice, proceeds along ice streams. This causes ice streams to surge and reduce thickness by some 90 percent, and height above sea level by up to 99 percent for floating ice, so the ice sheet undergoes gravitational collapse. Ice collapsing over marine embayments becomes floating ice shelves that may then disintegrate rapidly. This floods the world ocean with icebergs that reduce the ocean-to-atmosphere heat exchange, thereby triggering climate change. Calving bays migrate up low stagnating ice streams and carve out the accumulation zone of the collapsed ice sheet, which prevents its recovery, decreases Earth's albedo, and terminates the glaciation cycle. This sequence of events may coincide with a proposed life cycle of ice streams that drain the ice sheet. A first-order treatment of these life cycles is presented that depends on the longitudinal force balance along the flowbands of ice streams and gives a first approximation to ice-bed uncoupling at snapshots during gravitational collapse into ice shelves that disintegrate, thereby removing the ice sheet. The stability of the Antarctic Ice Sheet is assessed using this bottom-up approach.

  1. Structure of High Energy, Heavy Ions in Venus' Upper Ionosphere

    Science.gov (United States)

    Persson, Moa; Futaana, Yoshifumi; Nilsson, Hans; Stenberg Wieser, Gabriella; Hamrin, Maria; Fedorov, Andrei; Barabash, Stas

    2017-04-01

    The solar wind interacts with the atmosphere of Venus, and can reach directly down to the ionosphere. The interaction has previously been studied using the Pioneer Venus mission (PVO) and is now known to cause variations in the density in the ionosphere [Taylor et al., 1980], a transport of ions towards the night side [Knudsen et al., 1980], and an outflow of ions from the atmosphere [Barabash et al., 2007]. Measurements made by PVO showed that the main constituents of Venus ionosphere in the altitude range 150-400 km is the O+ and O2+ ions, where the former dominates from 180 km and higher, and the latter dominates from 180 km down to 150 km [Taylor et al., 1980]. New measurements, made by the Ion Mass Analyzer (IMA) onboard the Venus Express spacecraft, reveal the high-energy (10 eV to 15 keV) plasma characteristics in the ionosphere of Venus. Using the data collected during the low altitude (down to 130 km) pericentre passages during the aerobraking time period, we are able to extract the height profile of the total heavy ion content (O+ and O2+ ions) of Venus ionosphere. The results show two scale heights separated at 200 km; 10 km for 200 km. We interpret the results as two heavy ion components, namely, the O+ ions are dominant for >200 km, while the O2+ is dominant for methods of mass separation, to extract the two ion components of the scale height profiles, (O+ and O2+). First method is to use the moderate mass separation capabilities of the IMA instrument. The individual mass spectra are fitted by two Gaussian curves, representing O+ and O2+, derived from ground calibration information. The second method uses the energy spectrum, which sometimes has two discrete peaks. By assuming the same velocity for different components in the spacecraft reference frame (resulting in different energy for different masses), we can separate the composition. We will discuss the results of the obtained mass separated height profiles.

  2. The relative influence of H2O and CO2 on the primitive surface conditions of Venus

    Science.gov (United States)

    Salvador, A.; Massol, H.; Davaille, A.; Marcq, E.; Sarda, P.; Chassefiere, E.

    2017-12-01

    How the volatile content influences the primordial surface conditions of terrestrial planets and, thus, their future geodynamic evolution is an important question to answer. We simulate the secular convective cooling of a 1-D magma ocean (MO) in interaction with its outgassed atmosphere. A first rapid cooling stage, where efficient MO cooling and degassing take place, producing the atmosphere, is followed by a second quasi steady state where the heat flux balance is dominated by the solar flux. The end ofthe rapid cooling stage (ERCS) is reached when the mantle heat flux becomes negligible compared tothe absorbed solar flux. Varying the initial CO2 and H2O contents and the solar distance, we showed that the resulting surface conditions at ERCS strongly depend on these parameters and that water ocean's formation obeys simple scaling laws.Although today's Venus is located beyond the inner edge of the habitable zone due to its high albedo, its high CO2/H2O ratio prevents any water ocean formation.We already showed that depending on the formation time of its cloudcover and resulting albedo, only 0.3 Earth ocean mass might be sufficient to form a water ocean onearly Venus. Here we investigate more precisely these results by taking into account the effect of shortwave radiation on the radiative budget by computing the feedbacks between atmospheric composition and incident stellar flux instead of using a prescribed albedo value.

  3. Soft Costs Fact Sheet

    Energy Technology Data Exchange (ETDEWEB)

    None

    2016-05-01

    This fact sheet is an overview of the systems integration subprogram at the U.S. Department of Energy SunShot Initiative. Soft costs can vary significantly as a result of a fragmented energy marketplace. In the U.S., there are 18,000 jurisdictions and 3,000 utilities with different rules and regulations for how to go solar. The same solar equipment may vary widely in its final installation price due to process and market variations across jurisdictions, creating barriers to rapid industry growth. SunShot supports the development of innovative solutions that enable communities to build their local economies and establish clean energy initiatives that meet their needs, while at the same time creating sustainable solar market conditions.

  4. Systems Integration Fact Sheet

    Energy Technology Data Exchange (ETDEWEB)

    None

    2016-06-01

    This fact sheet is an overview of the Systems Integration subprogram at the U.S. Department of Energy SunShot Initiative. The Systems Integration subprogram enables the widespread deployment of safe, reliable, and cost-effective solar energy technologies by addressing the associated technical and non-technical challenges. These include timely and cost-effective interconnection procedures, optimal system planning, accurate prediction of solar resources, monitoring and control of solar power, maintaining grid reliability and stability, and many more. To address the challenges associated with interconnecting and integrating hundreds of gigawatts of solar power onto the electricity grid, the Systems Integration program funds research, development, and demonstration projects in four broad, interrelated focus areas: grid performance and reliability, dispatchability, power electronics, and communications.

  5. Photovoltaics Fact Sheet

    Energy Technology Data Exchange (ETDEWEB)

    None

    2016-02-01

    This fact sheet is an overview of the Photovoltaics (PV) subprogram at the U.S. Department of Energy SunShot Initiative. The U.S. Department of Energy (DOE)’s Solar Energy Technologies Office works with industry, academia, national laboratories, and other government agencies to advance solar PV, which is the direct conversion of sunlight into electricity by a semiconductor, in support of the goals of the SunShot Initiative. SunShot supports research and development to aggressively advance PV technology by improving efficiency and reliability and lowering manufacturing costs. SunShot’s PV portfolio spans work from early-stage solar cell research through technology commercialization, including work on materials, processes, and device structure and characterization techniques.

  6. A reconciled estimate of ice-sheet mass balance

    DEFF Research Database (Denmark)

    Shepherd, Andrew; Ivins, Erik R; A, Geruo

    2012-01-01

    We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth's polar ice sheets. We find that there is good...... agreement between different satellite methods--especially in Greenland and West Antarctica--and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by -142 ± 49, +14...... ± 43, -65 ± 26, and -20 ± 14 gigatonnes year(-1), respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 ± 0.20 millimeter year(-1) to the rate of global sea-level rise....

  7. A Reconciled Estimate of Ice-Sheet Mass Balance

    Science.gov (United States)

    Shepherd, Andrew; Ivins, Erik R.; Geruo, A.; Barletta, Valentia R.; Bentley, Mike J.; Bettadpur, Srinivas; Briggs, Kate H.; Bromwich, David H.; Forsberg, Rene; Galin, Natalia; hide

    2012-01-01

    We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth's polar ice sheets. We find that there is good agreement between different satellite methods-especially in Greenland and West Antarctica-and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by -142 plus or minus 49, +14 plus or minus 43, -65 plus or minus 26, and -20 plus or minus 14 gigatonnes year(sup -1), respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 plus or minus 0.20 millimeter year(sup -1) to the rate of global sea-level rise.

  8. Material Safety Data Sheets (MSDS)

    CERN Document Server

    Lalley, J

    About 250.000 Material Safety Data sheets from the U.S. Government Department of Defense MSDS database, a mirror of data from siri.uvm.edu, MSDS sheets maintained by Cornell University Environmental Health and Safety and other Cornell departments.

  9. Conjugate Shear Fractures at 'Ki Corona,' Southeast Parga Chasma, Venus

    Science.gov (United States)

    Willis, J. J.; Hansen, V. L.

    1996-03-01

    Brittle tensile failure of Venus' surface is evident in many tectonic regimes, including as extension fractures associated with caldera collapse, radial and concentric fractures of coronae, fractures normal to folds, and fracture belts. However, evidence of brittle shear failure has been described at only two localities_intersecting fractures oblique to wrinkle ridges in Lavinia Planitia were interpreted as conjugate shear fractures by Watters, and en echelon fractures in Guinevere Planitia record dominant extension. but with a component of shear. We confirm these earlier interpretations, and recognize the widespread nature of conjugate shear fractures across the Venus surface, identifying examples at over 100 locations in varied tectonic regimes, including coronae, wrinkle-ridged plains, and fracture belts. However, we focus here on fracture and fold relations at "Ki Corona" (46.8 degrees S, 302.5 degrees E), and their implications toward corona evolution.

  10. Venus. I - Carbon monoxide distribution and molecular-line searches

    Science.gov (United States)

    Wilson, W. J.; Klein, M. J.; Kahar, R. K.; Gulkis, S.; Olsen, E. T.; Ho, P. T. P.

    1981-01-01

    An observational program to study variations of the vertical distribution of CO in the Venus atmosphere is presented. Measurements of the J = 0 - 1 absorption line at 2.6 mm wavelength are reported for two phase angles in 1977, one near eastern elongation (February) and the other near inferior conjunction (April). The two spectra are significantly different, with the April absorption line being narrower and deeper. The results of numerical inversion calculations show that the CO mixing ratio increases by a factor of approximately 100 between 78 and 100 km and that the CO abundance above approximately 100 km is greatest on the night-side hemisphere. These conclusions are in qualitative agreement with theoretical models. In addition to the CO observations, a search for other molecules was made to provide further information on the composition of the Venus middle atmosphere. The J = 0 - 1 transition of (C-13)O was detected and upper limits were derived for nine other molecules.

  11. Basic theory and model calculations of the Venus ionosphere

    Science.gov (United States)

    Nagy, A. F.; Cravens, T. E.; Gombosi, T. I.

    1983-01-01

    An assessment is undertaken of current understanding of the physical and chemical processes that control Venus's ionospheric behavior, in view of the data that has been made available by the Venera and Pioneer Venus missions. Attention is given to the theoretical framework used in general planetary ionosphere studies, especially to the equations describing the controlling physical and chemical processes, and to the current status of the ion composition, density and thermal structure models developed to reproduce observed ionospheric behavior. No truly comprehensive and successful model of the nightside ionosphere has been published. Furthermore, although dayside energy balance calculations yield electron and ion temperature values that are in close agreement with measured values, the energetics of the night side eludes understanding.

  12. Data acquisition system for the VENUS detector at TRISTAN

    Energy Technology Data Exchange (ETDEWEB)

    Amako, K.; Arai, Y.; Sakamoto, H.; Teramoto, Y.; Uehara, S.; Yasu, Y.; Chiba, Y.; Endo, I.; Hayashibara, I.; Ohsugi, T.

    1988-11-01

    A data acquisition system for the VENUS detector at the TRISTAN electron-positron collider is presented. The whole system of the VENUS detector consists of nine different kinds of principal detectors, and the total number of electronics channels of the system reaches about 30 000. A FASTBUS system was introduced as the main data path and the TKO and the CAMAC standard have also been utilized for the frontened electronics. A FASTBUS interface to an on-line computer (VAX11/780), simplex segment interconnect and many data acquisition modules were developed. Most of the data are analyzed in a VAX cluster system in real time. Data logging is done in a main frame computer (FACOM M382) by using an automatic loading cartridge tape subsystem.

  13. Image processing and products for the Magellan mission to Venus

    Science.gov (United States)

    Clark, Jerry; Alexander, Doug; Andres, Paul; Lewicki, Scott; Mcauley, Myche

    1992-01-01

    The Magellan mission to Venus is providing planetary scientists with massive amounts of new data about the surface geology of Venus. Digital image processing is an integral part of the ground data system that provides data products to the investigators. The mosaicking of synthetic aperture radar (SAR) image data from the spacecraft is being performed at JPL's Multimission Image Processing Laboratory (MIPL). MIPL hosts and supports the Image Data Processing Subsystem (IDPS), which was developed in a VAXcluster environment of hardware and software that includes optical disk jukeboxes and the TAE-VICAR (Transportable Applications Executive-Video Image Communication and Retrieval) system. The IDPS is being used by processing analysts of the Image Data Processing Team to produce the Magellan image data products. Various aspects of the image processing procedure are discussed.

  14. Pioneer Venus Orbiter Radar Mapper - Design and operation

    Science.gov (United States)

    Pettengill, G. H.; Horwood, D. F.; Keller, C. H.

    1980-01-01

    The Radar Mapper Experiment, carried aboard the Pioneer Venus Orbiter spacecraft, is designed to obtain a near-global picture of the topography, meter-scale surface slopes and reflectivity of Venus. Constraints imposed by the choice of orbit limit radar coverage to a latitude band lying between 74 deg N and 61 deg S completely around the planet. In addition to the altimetry objectives, the experiment seeks an image of the radar scattering properties of the surface at oblique incidence. Sensitivity limits the imaged region to a band around the planet lying between 45 deg N and 10 deg S. Altimetric error is less than 200 m; altimetric surface 'footprint' size varies from about 10 km in diameter at a spacecraft altitude of 200 km, to 50 km at a maximum altitude of 4700 km. Imaging varies from 20 to 40 km, depending on spacecraft altitude.

  15. Mantle differentiation and thermal evolution of Mars, Mercury, and Venus

    International Nuclear Information System (INIS)

    Spohn, T.

    1991-01-01

    In the present models for the thermal evolution of Mercury, Venus, and Mars encompass core and mantle chemical differentiation, lithospheric growth, and volcanic heat-transfer processes. Calculation results indicate that crust and lithosphere thicknesses are primarily dependent on planet size as well as the bulk concentration of planetary radiogenic elements and the lithosphere's thermal conductivity. The evidence for Martian volcanism for at least 3.5 Gyr, and in Mercury for up to 1 Gyr, in conjunction with the presence of a magnetic field on Mercury and its absence on Mars, suggest the dominance of a lithospheric conduction heat-transfer mechanism in these planets for most of their thermal history; by contrast, volcanic heat piping may have been an important heat-transfer mechanism on Venus. 50 refs

  16. Plasma dynamics in current sheets

    International Nuclear Information System (INIS)

    Bogdanov, S.Yu.; Drejden, G.V.; Kirij, N.P.; AN SSSR, Leningrad

    1992-01-01

    Plasma dynamics in successive stages of current sheet evolution is investigated on the base of analysis of time-spatial variations of electron density and electrodynamic force fields. Current sheet formation is realized in a two-dimensional magnetic field with zero line under the action of relatively small initial disturbances (linear regimes). It is established that in the limits of the formed sheet is concentrated dense (N e ∼= 10 16 cm -3 ) (T i ≥ 100 eV, bar-Z i ≥ 2) hot pressure of which is balanced by the magnetic action of electrodynamic forces is carried out both plasma compression in the sheet limits and the acceleration along the sheet surface from a middle to narrow side edges

  17. Parabolic features and the erosion rate on Venus

    Science.gov (United States)

    Strom, Robert G.

    1993-01-01

    The impact cratering record on Venus consists of 919 craters covering 98 percent of the surface. These craters are remarkably well preserved, and most show pristine structures including fresh ejecta blankets. Only 35 craters (3.8 percent) have had their ejecta blankets embayed by lava and most of these occur in the Atla-Beta Regio region; an area thought to be recently active. parabolic features are associated with 66 of the 919 craters. These craters range in size from 6 to 105 km diameter. The parabolic features are thought to be the result of the deposition of fine-grained ejecta by winds in the dense venusian atmosphere. The deposits cover about 9 percent of the surface and none appear to be embayed by younger volcanic materials. However, there appears to be a paucity of these deposits in the Atla-Beta Regio region, and this may be due to the more recent volcanism in this area of Venus. Since parabolic features are probably fine-grain, wind-deposited ejecta, then all impact craters on Venus probably had these deposits at some time in the past. The older deposits have probably been either eroded or buried by eolian processes. Therefore, the present population of these features is probably associated with the most recent impact craters on the planet. Furthermore, the size/frequency distribution of craters with parabolic features is virtually identical to that of the total crater population. This suggests that there has been little loss of small parabolic features compared to large ones, otherwise there should be a significant and systematic paucity of craters with parabolic features with decreasing size compared to the total crater population. Whatever is erasing the parabolic features apparently does so uniformly regardless of the areal extent of the deposit. The lifetime of parabolic features and the eolian erosion rate on Venus can be estimated from the average age of the surface and the present population of parabolic features.

  18. Analysis of Volcanic Deposits on Venus Using Radar Polarimetry

    Science.gov (United States)

    Douglas, M.; Carter, L. M.

    2015-12-01

    The atmosphere of Venus is relatively transparent at radio wavelengths, providing an opportunity to examine its volcanic planetary surface using radar. The highest resolution radar images come from the Magellan mission, which mapped 98% of Venus's surface by transmitting and receiving unidirectionally polarized radio waves. Upgrades to the ground-based Arecibo telescope in 1999 allowed further imaging of the surface of Venus at conjunction in 1999, 2001, and 2004 by the transmission of a circularly polarized beam at 12.6cm wavelength and then the reception of two orthogonal circular polarization components [Carter et al., 2006]. We apply the Stokes vector method to the Arecibo measurements to calculate the circular polarization ratio (CPR), an indication of surface roughness, and the degree of linear polarization (DLP), a measure of whether there is subsurface scattering of the radar wave. We combine both the CPR and DLP datasets to enable a more holistic geologic interpretation of Magellan images. This allows us to examine geographic variations in high-altitude, high-emissivity regions such Beta Regio, and to investigate regions that may contain young lava flows such as Themis Regio. Our approach permits a more precise geologic mapping of the textures of coronas and lava flow fields, including the identification of abnormally rugged lava flows. The data were also used to search for pyroclastics emanating from large and intermediate sized volcanoes within the region visible to Arecibo.

  19. Near-infrared oxygen airglow from the Venus nightside

    Science.gov (United States)

    Crisp, D.; Meadows, V. S.; Allen, D. A.; Bezard, B.; Debergh, C.; Maillard, J.-P.

    1992-01-01

    Groundbased imaging and spectroscopic observations of Venus reveal intense near-infrared oxygen airglow emission from the upper atmosphere and provide new constraints on the oxygen photochemistry and dynamics near the mesopause (approximately 100 km). Atomic oxygen is produced by the Photolysis of CO2 on the dayside of Venus. These atoms are transported by the general circulation, and eventually recombine to form molecular oxygen. Because this recombination reaction is exothermic, many of these molecules are created in an excited state known as O2(delta-1). The airglow is produced as these molecules emit a photon and return to their ground state. New imaging and spectroscopic observations acquired during the summer and fall of 1991 show unexpected spatial and temporal variations in the O2(delta-1) airglow. The implications of these observations for the composition and general circulation of the upper venusian atmosphere are not yet understood but they provide important new constraints on comprehensive dynamical and chemical models of the upper mesosphere and lower thermosphere of Venus.

  20. Novel Architecture for a Long-Life, Lightweight Venus Lander

    International Nuclear Information System (INIS)

    Bugby, D.; Seghi, S.; Kroliczek, E.; Pauken, M.

    2009-01-01

    This paper describes a novel concept for an extended lifetime, lightweight Venus lander. Historically, to operate in the 480 deg. C, 90 atm, corrosive, mostly CO 2 Venus surface environment, previous landers have relied on thick Ti spherical outer shells and thick layers of internal insulation. But even the most resilient of these landers operated for only about 2 hours before succumbing to the environment. The goal on this project is to develop an architecture that extends lander lifetime to 20-25 hours and also reduces mass compared to the Pioneer Venus mission architecture. The idea for reducing mass is to: (a) contain the science instruments within a spherical high strength lightweight polymer matrix composite (PMC) tank; (b) surround the PMC tank with an annular shell of high performance insulation pre-pressurized to a level that (after landing) will exceed the external Venus surface pressure; and (c) surround the insulation with a thin Ti outer shell that contains only a net internal pressure, eliminating buckling overdesign mass. The combination of the PMC inner tank and thin Ti outer shell is lighter than a single thick Ti outer shell. The idea for extending lifetime is to add the following three features: (i) an expendable water supply that is placed within the insulation or is contained in an additional vessel within the PMC tank; (ii) a thin spherical evaporator shell placed within the insulation a short radial distance from the outer shell; and (iii) a thin heat-intercepting liquid cooled shield placed inboard of the evaporator shell. These features lower the temperature of the insulation below what it would have been with the insulation alone, reducing the internal heat leak and lengthening lifetime. The use of phase change materials (PCMs) inside the PMC tank is also analyzed as a lifetime-extending design option. The paper describes: (1) analytical modeling to demonstrate reduced mass and extended life; (2) thermal conductivity testing of high

  1. Study of upper haze of Venus from Venus Express SPICAV-IR data

    Science.gov (United States)

    Luginin, Mikhail; Fedorova, Anna; Belyaev, Denis; Montmessin, Franck; Wilquet, Valerie; Korablev, Oleg; Bertaux, Jean-Loup; Carine Vandaele, Ann

    2017-04-01

    The upper haze of Venus located at 70-90 km is composed of submicron aerosol particles of H2SO4 (Esposito et al., 1983). Three channels of SPICAV/SOIR instrument onboard the VEX orbiter provided the occultation profiles in three spectral ranges that resulted in the discovery of the bimodal nature of the size distribution in the upper haze comprising a mode with a radius of 0.1-0.3 μm, and a coarser mode of radius 0.4-1.0 μm; while the presence of detached haze layers was also reported (Montmessin et al., 2008; Wilquet et al., 2009). Recently, results from 222 SPICAV-IR solar occultations observed from May 2006 to November 2014 were reported (Luginin et al., 2016). Microphysical properties of the mesospheric haze were derived from the vertical profiles of atmospheric extinction obtained at 10 near-IR wavelengths. Bimodal distribution of particles was found to be consistent with data for some orbits with mean radius for mode 1 reff1=0.12±0.03 μm and reff2=0.84±0.16 μm for mode 2. The radius for the single mode case was found to be Reff=0.54±0.25 μm, being 1.5 to 2 times smaller at polar region (60°N-90°N). In the bimodal case the number density profiles decreased smoothly for both modes, from 500 cm-3 at 75 km to 50 cm-3 at 90 km for mode 1, and from 1 cm-3 at 75 km to 0.1 cm-3 at 90 km for mode 2. In this paper, we pursue the study of the aerosols in the Venus' upper haze. Scale heights were retrieved from 43 number density profiles in unimodal case. The mean scale height is found to be 3.6 ± 0.7 km. Scale height is larger at polar region than at middle latitudes both on morning and evening terminators ( 5 km at 85°N vs 2 km at 70°N). Retrieved scale heights is consistent with a mean upward motion of 1 mm/s at 80 km and 1 cm/s at 90 km. In several occultations, detached haze layers at altitudes between 70 and 90 km were observed. The structures sometimes can be observed over consecutive orbits. In some instances, detached haze layers are shifted in

  2. Equilibrium resurfacing of Venus: Results from new Monte Carlo modeling and implications for Venus surface histories

    Science.gov (United States)

    Bjonnes, E. E.; Hansen, V. L.; James, B.; Swenson, J. B.

    2012-02-01

    Venus' impact crater population imposes two observational constraints that must be met by possible model surface histories: (1) near random spatial distribution of ˜975 craters, and (2) few obviously modified impact craters. Catastrophic resurfacing obviously meets these constraints, but equilibrium resurfacing histories require a balance between crater distribution and modification to be viable. Equilibrium resurfacing scenarios with small incremental resurfacing areas meet constraint 1 but not 2, whereas those with large incremental resurfacing areas meet constraint 2 but not 1. Results of Monte Carlo modeling of equilibrium resurfacing ( Strom et al., 1994) is widely cited as support for catastrophic resurfacing hypotheses and as evidence against hypotheses of equilibrium resurfacing. However, the Monte Carlo models did not consider intermediate-size incremental resurfacing areas, nor did they consider histories in which the era of impact crater formation outlasts an era of equilibrium resurfacing. We construct three suites of Monte Carlo experiments that examine incremental resurfacing areas not previously considered (5%, 1%, 0.7%, and 0.1%), and that vary the duration of resurfacing relative to impact crater formation time (1:1 [suite A], 5:6 [suite B], and 2:3 [suite C]). We test the model results against the two impact crater constraints. Several experiments met both constraints. The shorter the time period of equilibrium resurfacing, or the longer the time of crater formation following the cessation of equilibrium resurfacing, the larger the possible areas of incremental resurfacing that satisfy both constraints. Equilibrium resurfacing is statistically viable for suite A at 0.1%, suite B at 0.1%, and suite C for 1%, 0.7%, and 0.1% areas of incremental resurfacing.

  3. Rare earths

    International Nuclear Information System (INIS)

    Cranstone, D.A.

    1980-01-01

    There has been no Canadian production of the rare earth oxides since 1977. World production in 1978, the last year for which figures are available, is estimated to have been about 41000 tonnes, mostly from Australia and the United States. The United States Bureau of Mines estimates that world reserves contain about 7 million tonnes of rare earth oxides and 35 million tonnes of yttrium. The largest yttrium reserves are in India, while China is believed to have the world's largest reserves of rare earth oxides. World consumption of rare aarths increased slightly in 1980, but is still only a small fraction of known reserves. Rare earths are used mainly in high-strength magnets, automobile exhaust systems, fluorescent tube and television screen phosphors, metallurgical applications, petroleum cracking catalysts, and glass polishing

  4. Earth Sciences

    International Nuclear Information System (INIS)

    Anon.

    1980-01-01

    The following papers were presented at the earth science session: earth science developments in support of water isolation; development of models and parameters for ground-water flow in fractured rock masses; isotope geochemistry as a tool for determining regional ground-water flow; natural analogs of radionuclide migration; nuclide retardation data: its use in the NWTS program; and ground-water geochemistry and interaction with basalt at Hanford

  5. Modelling the Antarctic Ice Sheet

    DEFF Research Database (Denmark)

    Pedersen, Jens Olaf Pepke; Holm, A.

    2015-01-01

    Science) Antarctic Ice Sheet (DAIS) model (Shaffer 2014) is forced by reconstructed time series of Antarctic temperature, global sea level and ocean subsurface temperature over the last two glacial cycles. In this talk a modelling work of the Antarctic ice sheet over most of the Cenozoic era using...... the DAIS model will be presented. G. Shaffer (2014) Formulation, calibration and validation of the DAIS model (version 1), a simple Antarctic ice sheet model sensitive to variations of sea level and ocean subsurface temperature, Geosci. Model Dev., 7, 1803‐1818...

  6. Earth materials and earth dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, K; Shankland, T. [and others

    2000-11-01

    In the project ''Earth Materials and Earth Dynamics'' we linked fundamental and exploratory, experimental, theoretical, and computational research programs to shed light on the current and past states of the dynamic Earth. Our objective was to combine different geological, geochemical, geophysical, and materials science analyses with numerical techniques to illuminate active processes in the Earth. These processes include fluid-rock interactions that form and modify the lithosphere, non-linear wave attenuations in rocks that drive plate tectonics and perturb the earth's surface, dynamic recrystallization of olivine that deforms the upper mantle, development of texture in high-pressure olivine polymorphs that create anisotropic velocity regions in the convecting upper mantle and transition zone, and the intense chemical reactions between the mantle and core. We measured physical properties such as texture and nonlinear elasticity, equation of states at simultaneous pressures and temperatures, magnetic spins and bonding, chemical permeability, and thermal-chemical feedback to better characterize earth materials. We artificially generated seismic waves, numerically modeled fluid flow and transport in rock systems and modified polycrystal plasticity theory to interpret measured physical properties and integrate them into our understanding of the Earth. This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

  7. Sausage mode instability of thin current sheets as a cause of magnetospheric substorms

    Directory of Open Access Journals (Sweden)

    J. Büchner

    Full Text Available Observations have shown that, prior to substorm explosions, thin current sheets are formed in the plasma sheet of the Earth's magnetotail. This provokes the question, to what extent current-sheet thinning and substorm onsets are physically, maybe even causally, related. To answer this question, one has to understand the plasma stability of thin current sheets. Kinetic effects must be taken into account since particle scales are reached in the course of tail current-sheet thinning. We present the results of theoretical investigations of the stability of thin current sheets and about the most unstable mode of their decay. Our conclusions are based upon a non-local linear dispersion analysis of a cross-magnetic field instability of Harris-type current sheets. We found that a sausage-mode bulk current instability starts after a sheet has thinned down to the ion inertial length. We also present the results of three-dimensional electromagnetic PIC-code simulations carried out for mass ratios up to Mi / me=64. They verify the linearly predicted properties of the sausage mode decay of thin current sheets in the parameter range of interest.

    Key words. Magnetospheric physics (plasma waves and instabilities; storms and substorms · Space plasma physics (magnetic reconnection

  8. Investigation of winds in Venus mesosphere by digital method using UV images from VMC aboard Venus Express.

    Science.gov (United States)

    Patsaeva, Marina; Khatuntsev, Igor; Ignatiev, Nikolai

    2013-04-01

    Investigation of winds at the top cloud layer is important for understanding the global circulation of the Venus atmosphere. The Venus Monitoring Camera (VMC) aboard Venus Express has acquired a huge number of UV (365 nm) images. UV images of top cloud layer are customary to obtain the wind velocity due to their high contrast. Visual estimation of wind velocities is a labor intensive procedure. Authors have developed a digital method to estimate velocities of shifts of cloud details. The method is based on analysis of correlations between two UV images acquired at different moments. The method takes into account the change of a correlation function due to latitudinal peculiarities of cloud morphology and eliminates image regions which are far from the sub-spacecraft point. The digital method provides with good vector coverage of the Venus day side (9-16 local time) from the equator to high latitudes. The best agreement between the digital and visual methods is observed at low latitudes (below 35S). The discrepancy at higher latitudes is related to complicated cloud morphology, namely domination of streaks, which increases errors in the zonal wind speed. The method is productive for long-scale circulation at the top cloud layer. Sizes of regions for correlation were chosen empirically as a trade-off of sensitivity against noise immunity and varies from 10x7.5 ° to 20x10 ° depending on grid step. 580 orbits covering ten Venus years have been processed by using the digital method. The database of shift vectors counts about 400000 records. The mean wind speed at low latitudes is about 100 m/s. Wind vector fields were obtained for every orbit. The zonal wind speed in the equatorial region exhibits short-period (about 4.8 days) and long-period variations (long-term trend). Vector field averaged by all orbits show deviations of the main stream up to 5 degrees poleward in the early afternoon (12.5-14.5h) at 45-55S. The mean absolute value of the wind speed increases from

  9. Identification of Postclassic Maya Constellations from the Venus Pages of the Dresden Codex

    Directory of Open Access Journals (Sweden)

    Changbom Park

    2010-01-01

    Full Text Available Ancient Mayan civilization, flourished from 1200 B.C. to 1500 A.D., has left numerous hieroglyphic texts on astronomical observations and calendar. In particular, the Dresden Codex contains the most details of such ancient Mayan heritage. Page 24 and those from 46 to 50 of the Dresden Codex describe the Mayan Venus calendar along with the augural descriptions. We note that the calendar in Dresden Codex is Venus-solar calendar. Our work focuses on the possibility that the calendar was made to work in conjunction with the periodic appearance of constellations on the sky. By analyzing the descriptions in the Venus pages, we propose that the columns in each page describe the motion of Venus with respect to major constellations at dates corresponding to special events while the calendar dates increase horizontally in the synodic period of Venus. We present twenty Mayan constellations identified from the Venus pages assuming that the first date of page 46 is February 6, 1228. We also report our understanding of verb expressions about the relative movement of constellations and Venus.La civilización maya, que floreció del 1200 a.C. a 1500 d.C., dejó numerosos textos jeroglíficos sobre el calendario y observaciones astronómicos. El Códice de Dresde, en particular, contiene el más detallado de dichos antiguos legados mayas. Las páginas 24 y 46 a 50 de dicho códice describen el calendario de Venus con los augurios correspondientes. Nosotros hemos notado que éste es un calendario Venus-Solar, y nuestro trabajo se enfoca sobre la posibilidad de que estuviera hecho para trabajar en conjunción con la aparición de determinadas constelaciones en el cielo. Es a través del análisis y descripción de las páginas de Venus que proponemos que las columnas en cada página describen el movimiento de Venus respecto de constelaciones mayores, en fechas que corresponden a eventos especiales, mientras que las fechas calendáricas se incrementan

  10. Plasma heating and acceleration in current sheets formed in discharges in argon

    Directory of Open Access Journals (Sweden)

    Kyrie N.P.

    2017-01-01

    Full Text Available According to present notion, flares on the sun and other stars, substorms in magnetospheres of Earth and other planets, and disruptive instabilities in tokamak plasma are connected to development of current sheets in magnetized plasma. Therefore, current sheet dynamics and magnetic reconnection processes were studied actively during the last several decades. This paper presents the results of experimental studies of plasma heating and acceleration in current sheets formed in discharges in argon. The temperature and energy of directed motion of argon ions of different degrees of ionization were measured by spectroscopic methods. It was found that Ar II, Ar III and Ar IV ions are localized in different regions of the sheet. It was shown that Ampere forces applied to the sheet can accelerate the argon ions to observed energies.

  11. Current sheets with inhomogeneous plasma temperature: Effects of polarization electric field and 2D solutions

    International Nuclear Information System (INIS)

    Catapano, F.; Zimbardo, G.; Artemyev, A. V.; Vasko, I. Y.

    2015-01-01

    We develop current sheet models which allow to regulate the level of plasma temperature and density inhomogeneities across the sheet. These models generalize the classical Harris model via including two current-carrying plasma populations with different temperature and the background plasma not contributing to the current density. The parameters of these plasma populations allow regulating contributions of plasma density and temperature to the pressure balance. A brief comparison with spacecraft observations demonstrates the model applicability for describing the Earth magnetotail current sheet. We also develop a two dimensional (2D) generalization of the proposed model. The interesting effect found for 2D models is the nonmonotonous profile (along the current sheet) of the magnetic field component perpendicular to the current sheet. Possible applications of the model are discussed

  12. 2007 Swimming Season Fact Sheets

    Science.gov (United States)

    To help beachgoers make informed decisions about swimming at U.S. beaches, EPA annually publishes state-by-state data about beach closings and advisories for the previous year's swimming season. These fact sheets summarize that information by state.

  13. 2006 Swimming Season Fact Sheets

    Science.gov (United States)

    To help beachgoers make informed decisions about swimming at U.S. beaches, EPA annually publishes state-by-state data about beach closings and advisories for the previous year's swimming season. These fact sheets summarize that information by state.

  14. 2009 Swimming Season Fact Sheets

    Science.gov (United States)

    To help beachgoers make informed decisions about swimming at U.S. beaches, EPA annually publishes state-by-state data about beach closings and advisories for the previous year's swimming season. These fact sheets summarize that information by state.

  15. 2008 Swimming Season Fact Sheets

    Science.gov (United States)

    To help beachgoers make informed decisions about swimming at U.S. beaches, EPA annually publishes state-by-state data about beach closings and advisories for the previous year's swimming season. These fact sheets summarize that information by state.

  16. 2010 Swimming Season Fact Sheets

    Science.gov (United States)

    To help beachgoers make informed decisions about swimming at U.S. beaches, EPA annually publishes state-by-state data about beach closings and advisories for the previous year's swimming season. These fact sheets summarize that information by state.

  17. 2012 Swimming Season Fact Sheets

    Science.gov (United States)

    To help beachgoers make informed decisions about swimming at U.S. beaches, EPA annually publishes state-by-state data about beach closings and advisories for the previous year's swimming season. These fact sheets summarize that information by state.

  18. State Fact Sheets on COPD

    Science.gov (United States)

    ... Submit Search The CDC Chronic Obstructive Pulmonary Disease (COPD) Note: Javascript is disabled or is not supported ... message, please visit this page: About CDC.gov . COPD Homepage Data and Statistics Fact Sheets Publications Publications ...

  19. Energy information sheets, July 1998

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-07-01

    The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

  20. Energy information sheets, September 1996

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-09-01

    The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

  1. A tale of two telescopes: North Queensland and the 1882 transit of Venus

    Science.gov (United States)

    Orchiston, Wayne; Darlington, Vicki

    2017-08-01

    The 1882 transit of Venus offered the final opportunity for astronomers to use these rare events to pin down the distance from the Earth to the Sun. A British party based itself in southern Queensland, but total cloud cover prevented any observations being made on the critical day. In this paper we trace the preparations of the British party, and then show how they laid the foundations for the development of astronomy in Queensland by selling their two 6-in Cooke refractors before returning to Britain. Both instruments were purchased by a Townsville amateur astronomer, Edwin Norris, and although he installed one in an observatory, he made little use of it. However, he subsequently sold the other telescope to J. Ewen Davidson of Mackay, who also erected an obser-vatory for it. Davidson then used his instrument for cometary astronomy, in the process discovering two new comets, one of which now bears his name. Unfortunately, recent attempts to track down the present whereabouts of the two telescopes have failed.

  2. On the Thermal Protection Systems of Landers for Venus Exploration

    Science.gov (United States)

    Ekonomov, A. P.; Ksanfomality, L. V.

    2018-01-01

    The landers of the Soviet Venera series—from Venera-9 to Venera-14—designed at the Lavochkin Association are a man-made monument to spectacular achievements of Soviet space research. For more than 40 years, they have remained the uneclipsed Soviet results in space studies of the Solar System. Within the last almost half a century, the experiments carried out by the Venera-9 to Venera-14 probes for studying the surface of the planet have not been repeated by any space agency in the world, mainly due to quite substantial technical problems. Since that time, no Russian missions with landers have been sent to Venus either. On Venus, there is an anoxic carbon dioxide atmosphere, where the pressure is 9.2 MPa and the temperature is 735 K near the surface. A long-lived lander should experience these conditions for an appreciable length of time. What technical solutions could provide a longer operation time for a new probe investigating the surface of Venus, if its thermal scheme is constructed similar to that of the Venera series? Onboard new landers, there should be a sealed module, where the physical conditions required for operating scientific instruments are maintained for a long period. At the same time, new high-temperature electronic equipment that remains functional under the above-mentioned conditions have appeared. In this paper, we consider and discuss different variants of the system for a long-lived sealed lander, in particular, the absorption of the penetrating heat due to water evaporation and the thermal protection construction for the instruments with intermediate characteristics.

  3. Two activities with a simple model of the solar system: discovering Kepler’s 3rd law and investigating apparent motion of Venus

    Science.gov (United States)

    Rovšek, Barbara; Guštin, Andrej

    2018-01-01

    An astronomy ‘experiment’ composed of three parts is described in the article. Being given necessary data a simple model of inner planets of the solar system is made in the first part with planets’ circular orbits using appropriate scale. In the second part revolution of the figurines used as model representations of the planets along their orbits is observed. In the third part of activity apparent motion of Venus with respect to the observer on the Earth is studied. In the second part of the paper problems are given, which relate to experimental activities and are designed to test if learning outcomes of the experiment have been achieved: if correlation between orbital radius and orbital velocity has been perceived, concepts related to motion of Venus as observed from the Earth have been acquired and periodicity recognized. Described astronomy ‘experiment’ was one of the three science experiments given to 11 and 12 years old students prior to Slovene science competition in 2017 (the call for competition is at www.dmfa.si, guidelines for the experiment (in Slovene) can be found at www.kresnickadmfa.si/files/2016/07/poskus_1617_r67p1_S.pdf). At the end of the paper the results obtained at competition are presented.

  4. In-situ exploration of Venus on a global scale : direct measurements of origins and evolution, meterology, dynamics, and chemistry by a long-duration aerial science station

    Science.gov (United States)

    Baines, Kevin H.; Atreya, Sushi; Carlson, Robert W.; Chutjian, Ara; Crisp, David; Hall, Jeffrey L.; Jones, Dayton L.; Kerzhanovich, Victor V.; Limaye, Sanjay S.

    2005-01-01

    Drifting in the strong winds of Venus under benign Earth-like temperature and pressure conditions, an instrumented balloon-borne science station presents a viable means to explore, in-situ, the Venusian atmosphere on a global scale. Flying over the ground at speeds exceeding 240 km/hour while floating in the Venusian skies near 55 km altitude for several weeks, such an aerostat can conduct a 'world tour' of our neighboring planet, as it circumnavigates the globe multiple times during its flight from equatorial to polar latitudes. Onboard science sensors can repeatedly and directly sample gas compositions, atmospheric pressures and temperatures and cloud particle properties, giving unprecedented insight into the chemical processes occurring within the sulfuric clouds. Additionally, interferometric tracking via Earth-based radio observatories can yield positions and windspeeds to better than 10 cm/sec over one-hour periods, providing important information for understanding the planet's meridional circulation and enigmatic zonal super-rotation, as well as local dynamics associated with meteorological processes. As well, hundreds of GCMS spectra collected during the flight can provide measurements of noble gas compositions and their isotopes with unprecedented accuracy, thereby enabling fundamental new insights into Venus's origin and evolution.

  5. Solar rotation effects on the thermospheres of Mars and Earth.

    Science.gov (United States)

    Forbes, Jeffrey M; Bruinsma, Sean; Lemoine, Frank G

    2006-06-02

    The responses of Earth's and Mars' thermospheres to the quasi-periodic (27-day) variation of solar flux due to solar rotation were measured contemporaneously, revealing that this response is twice as large for Earth as for Mars. Per typical 20-unit change in 10.7-centimeter radio flux (used as a proxy for extreme ultraviolet flux) reaching each planet, we found temperature changes of 42.0 +/- 8.0 kelvin and 19.2 +/- 3.6 kelvin for Earth and Mars, respectively. Existing data for Venus indicate values of 3.6 +/- 0.6 kelvin. Our observational result constrains comparative planetary thermosphere simulations and may help resolve existing uncertainties in thermal balance processes, particularly CO2 cooling.

  6. The Ancient Mariner and the transit of Venus.

    Science.gov (United States)

    Griffin-Short, Rita

    2003-12-01

    The achievements of William Wales FRS - astronomer, classical scholar, demographer, editor, mathematician, meteorologist and humane teacher - have been overshadowed by the fame of Cook's extraordinary voyages, and overlooked as a significant influence on Samuel Taylor Coleridge's early development. The Royal Society sent Wales to Hudson Bay, Canada, and James Cook to Tahiti, both to observe the 1769 transit of Venus as part of an international project to calculate solar parallax, and hence the distance to the Sun. Wales later taught mathematics and navigation science at Christ's Hospital School to a precocious Coleridge, whose creative mind translated tales of polar adventures into memorable poetry.

  7. Whistler Wave Propagation Through the Ionosphere of Venus

    Science.gov (United States)

    Pérez-Invernón, F. J.; Lehtinen, N. G.; Gordillo-Vázquez, F. J.; Luque, A.

    2017-11-01

    We investigate the attenuation of whistler waves generated by hypotetical Venusian lightning occurring at the altitude of the cloud layer under different ionospheric conditions. We use the Stanford full-wave method for stratified media of Lehtinen and Inan (2008) to model wave propagation through the ionosphere of Venus. This method calculates the electromagnetic field created by an arbitrary source in a plane-stratified medium (i.e., uniform in the horizontal direction). We see that the existence of holes in electronic densities and the magnetic field configuration caused by solar wind play an important role in the propagation of electromagnetic waves through the Venusian ionosphere.

  8. Sulfuric acid cloud interpretation of the infrared spectrum of Venus

    Science.gov (United States)

    Martonchik, J. V.

    1974-01-01

    Sulfuric acid single-cloud models are compared with the Venus spectrum in the 8-14 micron region. The results indicate that a cloud composed of a 75 percent H2SO4 solution and with a particle density of 100 per cu cm is in good agreement with observations. In addition to explaining the 11.2 micron absorption, this model also predicts an absorption feature at 16.7 microns which should be detectable if the observation is made from an aircraft.

  9. The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet-climate model

    NARCIS (Netherlands)

    Stap, Lennert B.; Van De Wal, Roderik S.W.; De Boer, Bas; Bintanja, Richard; Lourens, Lucas J.

    2017-01-01

    Since the inception of the Antarctic ice sheet at the Eocene-Oligocene transition ( ~34 Myr ago), land ice has played a crucial role in Earth's climate. Through feedbacks in the climate system, land ice variability modifies atmospheric temperature changes induced by orbital, topographical, and

  10. Simulating the Antarctic ice sheet in the late-Pliocene warm period : PLISMIP-ANT, an ice-sheet model intercomparison project

    NARCIS (Netherlands)

    De Boer, B.; Dolan, A. M.; Bernales, J.; Gasson, E.; Goelzer, Heiko; Golledge, N. R.; Sutter, J.; Huybrechts, P.; Lohmann, G.; Rogozhina, I.; Abe-Ouchi, A.; Saito, F.; Van De Wal, R. S W

    2015-01-01

    In the context of future climate change, understanding the nature and behaviour of ice sheets during warm intervals in Earth history is of fundamental importance. The late Pliocene warm period (also known as the PRISM interval: 3.264 to 3.025 million years before present) can serve as a potential

  11. Possible giant metamorphic core complex at the center of Artemis Corona, Venus

    Science.gov (United States)

    Spencer, J.E.

    2001-01-01

    Hundreds of circular features on Venus known as coronae are characterized by annular fractures and commonly associated radial fractures and lava flows. Coronae are thought to have been produced by buoyant mantle diapirs that flatten and spread at the base of the lithosphere and cause fracturing, uplift, and magmatism. The interior of Artemis Corona, by far the largest corona at 2100 km diameter, is divided in half by a northeast-trending deformation belt that contains numerous rounded ridges resembling antiforms. The largest of these ridges, located at the center of Artemis Corona, is ???5 km high on its steep northwest flank where it is adjacent to a flat-bottomed, 10-km-wide trough interpreted as a rift valley. The 280-km-long antiformal ridge is marked by perpendicular grooves that cross the ???50-km-wide ridge and extend southeastward as far as 120 km across adjacent plains. The grooves abruptly terminate northwestward at the rift trough. The large antiformal ridge terminates southwestward at a transform shear zone that parallels the grooves. These features-rift valley, antiformal uplift, grooves, and transform shear zone-are morphologically and geometrically similar to grooved, elevated, submarine metamorphic core complexes on the inside corners of ridge-transform intersections of slow-spreading ridges on Earth. As with submarine core complexes, the grooved surface on Venus is interpreted as the footwall of a large-displacement normal fault, and the grooves are inferred to be the product of plastic molding of the footwall to irregularities on the underside of the hanging wall followed by tectonic exhumation of the molded grooves and conveyer-belt-like transport up and over the large antiform and across the southeastern plains. According to this interpretation, the trend of the grooves records the direction of extension, which is perpendicular to the thrusts at the leading edge of the annular thrust belt 1000 km to the southeast. Both may have formed at the

  12. Digital Earth - A sustainable Earth

    Science.gov (United States)

    Mahavir

    2014-02-01

    All life, particularly human, cannot be sustainable, unless complimented with shelter, poverty reduction, provision of basic infrastructure and services, equal opportunities and social justice. Yet, in the context of cities, it is believed that they can accommodate more and more people, endlessly, regardless to their carrying capacity and increasing ecological footprint. The 'inclusion', for bringing more and more people in the purview of development is often limited to social and economic inclusion rather than spatial and ecological inclusion. Economic investment decisions are also not always supported with spatial planning decisions. Most planning for a sustainable Earth, be at a level of rural settlement, city, region, national or Global, fail on the capacity and capability fronts. In India, for example, out of some 8,000 towns and cities, Master Plans exist for only about 1,800. A chapter on sustainability or environment is neither statutorily compulsory nor a norm for these Master Plans. Geospatial technologies including Remote Sensing, GIS, Indian National Spatial Data Infrastructure (NSDI), Indian National Urban Information Systems (NUIS), Indian Environmental Information System (ENVIS), and Indian National GIS (NGIS), etc. have potential to map, analyse, visualize and take sustainable developmental decisions based on participatory social, economic and social inclusion. Sustainable Earth, at all scales, is a logical and natural outcome of a digitally mapped, conceived and planned Earth. Digital Earth, in fact, itself offers a platform to dovetail the ecological, social and economic considerations in transforming it into a sustainable Earth.

  13. A scaling law for aeolian dunes on Mars, Venus, Earth, and for subaqueous ripples

    OpenAIRE

    Claudin, Philippe; Andreotti, Bruno

    2006-01-01

    The linear stability analysis of the equations governing the evolution of a flat sand bed submitted to a turbulent shear flow predicts that the wavelength $\\lambda$ at which the bed destabilises to form dunes should scale with the drag length $L_{\\rm drag} = \\frac{\\rho_s}{\\rho_f} d$. This scaling law is tested using existing and new measurements performed in water (subaqueous ripples), in air (aeolian dunes and fresh snow dunes), in a high pressure CO$_2$ wind tunnel reproducing conditions cl...

  14. Automobile sheet metal part production with incremental sheet forming

    Directory of Open Access Journals (Sweden)

    İsmail DURGUN

    2016-02-01

    Full Text Available Nowadays, effect of global warming is increasing drastically so it leads to increased interest on energy efficiency and sustainable production methods. As a result of adverse conditions, national and international project platforms, OEMs (Original Equipment Manufacturers, SMEs (Small and Mid-size Manufacturers perform many studies or improve existing methodologies in scope of advanced manufacturing techniques. In this study, advanced manufacturing and sustainable production method "Incremental Sheet Metal Forming (ISF" was used for sheet metal forming process. A vehicle fender was manufactured with or without die by using different toolpath strategies and die sets. At the end of the study, Results have been investigated under the influence of method and parameters used.Keywords: Template incremental sheet metal, Metal forming

  15. Horizontal electromagnetic casting of thin metal sheets

    Science.gov (United States)

    Hull, John R.; Lari, Robert J.; Praeg, Walter F.; Turner, Larry R.

    1987-01-01

    Thin metal sheets are cast by magnetically suspending molten metal deposited within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled to form a solid metal sheet. Magnetic flux increases as the molten metal sheet moves downward and decreases as the molten metal sheet moves upward to stabilize the sheet and maintain it in equilibrium as it is linearly displaced and solidified by cooling gases. A conducting shield is electrically coupled to the molten metal sheet by means of either metal sheet engaging rollers or brushes on the solidified metal, and by means of an electrode in the vessel containing the molten metal thereby providing a return path for the eddy currents induced in the metal sheet by the AC coil generated magnetic flux. Variation in the geometry of the conducting shield allows the magnetic flux between the metal sheet and the conducting shield to be varied and the thickness in surface quality of the metal sheet to be controlled. Side guards provide lateral containment for the molten metal sheet and stabilize and shape the magnetic field while a leader sheet having electromagnetic characteristics similar to those of the metal sheet is used to start the casting process and precedes the molten metal sheet through the magnet and forms a continuous sheet therewith. The magnet may be either U-shaped with a single racetrack coil or may be rectangular with a pair of facing bedstead coils.

  16. Horizontal electromagnetic casting of thin metal sheets

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R. (Hinsdale, IL); Lari, Robert J. (Aurora, IL); Praeg, Walter F. (Palos Park, IL); Turner, Larry R. (Naperville, IL)

    1988-01-01

    Thin metal sheets are cast by magnetically suspending molten metal deposited within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled to form a solid metal sheet. Magnetic flux increases as the molten metal sheet moves downward and decreases as the molten metal sheet moves upward to stabilize the sheet and maintain it in equilibrium as it is linearly displaced and solidified by cooling gases. A conducting shield is electrically coupled to the molten metal sheet by means of either metal sheet engaging rollers or brushes on the solidified metal, and by means of an electrode in the vessel containing the molten metal thereby providing a return path for the eddy currents induced in the metal sheet by the AC coil generated magnetic flux. Variation in the geometry of the conducting shield allows the magnetic flux between the metal sheet and the conducting shield to be varied and the thickness in surface quality of the metal sheet to be controlled. Side guards provide lateral containment for the molten metal sheet and stabilize and shape the magnetic field while a leader sheet having electromagnetic characteristics similar to those of the metal sheet is used to start the casting process and precedes the molten metal sheet through the magnet and forms a continuous sheet therewith. The magnet may be either U-shaped with a single racetrack coil or may be rectangular with a pair of facing bedstead coils.

  17. Venus Mobile Explorer with RPS for Active Cooling: A Feasibility Study

    Science.gov (United States)

    Leifer, Stephanie D.; Green, Jacklyn R.; Balint, Tibor S.; Manvi, Ram

    2009-01-01

    We present our findings from a study to evaluate the feasibility of a radioisotope power system (RPS) combined with active cooling to enable a long-duration Venus surface mission. On-board power with active cooling technology featured prominently in both the National Research Council's Decadal Survey and in the 2006 NASA Solar System Exploration Roadmap as mission-enabling for the exploration of Venus. Power and cooling system options were reviewed and the most promising concepts modeled to develop an assessment tool for Venus mission planners considering a variety of future potential missions to Venus, including a Venus Mobile Explorer (either a balloon or rover concept), a long-lived Venus static lander, or a Venus Geophysical Network. The concepts modeled were based on the integration of General Purpose Heat Source (GPHS) modules with different types of Stirling cycle heat engines for power and cooling. Unlike prior investigations which reported on single point design concepts, this assessment tool allows the user to generate either a point design or parametric curves of approximate power and cooling system mass, power level, and number of GPHS modules needed for a "black box" payload housed in a spherical pressure vessel.

  18. Soldering sheets using soft solders

    Directory of Open Access Journals (Sweden)

    Milan Brožek

    2013-01-01

    Full Text Available The paper contains strength tests results of joints soldered using lead and leadless soft solders. For tests lead solders types Pb60Sn40 and Sn60Pb40 and leadless soft solders types Sn95.5Ag3.8Cu0.7 and Sn96Ag4 were used. As basic materials steel sheet, zinc-coated steel sheet, copper sheet and brass sheet 100 x 20 x 1 mm was the test samples size. Always two sheets were cleaned and jointed together. For heating the propane-butane + air flame was used. Then the tested assemblies were loaded using the universal tensile-strength testing machine till to failure. At the tests the force needed for assemblies failure and failure type (in soldered joint, in basic material were recorded. From measured data the solder strength was calculated. From the experiment results it follows that from the point of view of the soldered joints strength as well of the solder strength relatively small differences were found. At the same time it is evident that the joint strength and solder strength depend on soldered material type and on soldered joint lapping length. On the basis of carried out experiments it can be stated that the substitution of lead solders by leadless solders is possible without risk of soldered joints strength decrease.

  19. Uranium mining sites - Thematic sheets

    International Nuclear Information System (INIS)

    2009-01-01

    A first sheet proposes comments, data and key numbers about uranium extraction in France: general overview of uranium mining sites, status of waste rock and tailings after exploitation, site rehabilitation. The second sheet addresses the sources of exposure to ionizing radiations due to ancient uranium mining sites: discussion on the identification of these sources associated with these sites, properly due to mining activities or to tailings, or due to the transfer of radioactive substances towards water and to the contamination of sediments, description of the practice and assessment of radiological control of mining sites. A third sheet addresses the radiological exposure of public to waste rocks, and the dose assessment according to exposure scenarios: main exposure ways to be considered, studied exposure scenarios (passage on backfilled path and grounds, stay in buildings built on waste rocks, keeping mineralogical samples at home). The fourth sheet addresses research programmes of the IRSN on uranium and radon: epidemiological studies (performed on mine workers; on French and on European cohorts, French and European studies on the risk of lung cancer associated with radon in housing), study of the biological effects of chronic exposures. The last sheet addresses studies and expertises performed by the IRSN on ancient uranium mining sites in France: studies commissioned by public authorities, radioactivity control studies performed by the IRSN about mining sites, participation of the IRSN to actions to promote openness to civil society

  20. Complete plasma dropouts at Vela satellites during thinning of the plasma sheet

    International Nuclear Information System (INIS)

    Lui, A.T.Y.; Hones, E.W. Jr.; Venkatesan, D.; Akasofu, S.; Bame, S.J.

    1975-01-01

    Five satellite years of Vela data are examined for plasma sheet thinnings. Complete proton disappearances (plasma dropouts) are the main subject here. During such times, the Vela satellite is temporarily in the high-latitude tail lobe. The distribution of such plasma dropouts within the magnetotail suggests that the semithickness of the plasma sheet near midnight seldom reaches less than 1 R/sub E/ during substorms and that the dawn and dusk portions of the plasma sheet remain thicker than the midnight portion. But it is also shown that the plasma sheet occasionally becomes very thin near the dusk magnetopause. No such severe thinnings of the plasma sheet are found near the dawn magnetopause. Plasma dropouts can occur regardless of the sign of the Z component of the IMF, but their frequency of occurrence seems to be greater when the Z component is negative.Three plasma dropouts which occurred in the midnight sector at unusually large distances from the estimated position of the neutral sheet were observed during geomagnetic storms. It is likely that the midnight sector of the plasma sheet can become very thick (approx.18 R/sub E/) at certain times during the main phase of storms. Detailed measurements in the plasma sheet were obtained near the beginning of a geomagnetic storm whose sc triggered a substorm. A compression of the plasma sheet at X/sub SM/approx. =-15 R/sub E/ occurred about 10 min after the sc onset at the earth and about 5 min after the start of plasma sheet thinning associated with the sc-related substorm. If compression-thinning of the plasma sheet initiated this substorm, the triggering action must have occurred earthward of X/sub SM/approx. =-15 R/sub E/

  1. Theoretical study of the luminance distribution on the Venus disk

    International Nuclear Information System (INIS)

    Bigourd, C.; Deuze, J.L.; Devaux, C.; Herman, M.; Lenoble, J.

    1974-01-01

    The analysis of the sunlight scattered by Venus gives some insight upon its clouds. The measurements of polarized light are probably more sensitive to the nature of their constituents, and some recent studies seem to be able to give a satisfactory interpretation of this part of the scattered light. But the polarized light concerns the upper part of the clouds, and it is interesting to compare these with intensity measurements. The phase curves, for the integrated light, leave some indetermination, so we have studied if the intensity distribution on the Venus disk could give more accurate informations. This work based on some plates kindly communicated by A. Dolfus, and analysed at Meudon Observatory, is more a preliminary investigation of the sensitivity of the method than an interpretation of the partial results presented. A simple model, of homogeneous plane parallel cloud, has been used, and the influence of various parameters has been tested (single scattering albedo, refractive index of particles and size distribution, optical depth of the cloud). (Auth.)

  2. 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.

  3. Extreme Temperature Pulse Injection Position Sensor for Venus Environment

    Science.gov (United States)

    Ji, Jerri; Kumar, Nishant; Singh, Sase; Narine, Roop

    After developed two types of extreme temperature motors (Switched Reluctance Motor and Blushless DC Motor), Honeybee Robotics has successfully developed an Extreme Temperature Pulse Injection Position Sensor that can be used to commutate motors and provide positional information. This paper presents an insight into the challenges of designing extreme tempera-ture electro-mechanical system and provides results of the experiment performed in the Venus environment. The operational temperature range for existing commutation devices, include Hall Sensors, Resolvers and Encoders is limited to temperatures less than 180C. The Extreme Temperature Pulse Injection Position Sensor is capable of working continuously at 460C and at 92 atm. The design of this device involves a unique rotor design and an innovative phase pulsing algorithm implemented through a high speed DSP. The shape of the rotor provides a unique flow-path to the lines-of-flux through the poles of the stator. The pulsing algorithm makes it possible to nullify the effects of parametric changes (wire resistance, permeability, air gap, etc.) due to increase in temperature. The algorithm relies on the relative flux density between two stator poles rather than the absolute measurement of the flux density in each pole. Extreme temperature position sensor, along with scalable extreme temperature motor and gearhead allow for creation of robot arms and even mobility systems for future Venus missions to achieve their goals and objectives.

  4. Solar Energetic Particle Transport Near a Heliospheric Current Sheet

    Energy Technology Data Exchange (ETDEWEB)

    Battarbee, Markus; Dalla, Silvia [Jeremiah Horrocks Institute, University of Central Lancashire, PR1 2HE (United Kingdom); Marsh, Mike S., E-mail: mbattarbee@uclan.ac.uk [Met Office, Exeter, EX1 3 PB (United Kingdom)

    2017-02-10

    Solar energetic particles (SEPs), a major component of space weather, propagate through the interplanetary medium strongly guided by the interplanetary magnetic field (IMF). In this work, we analyze the implications that a flat Heliospheric Current Sheet (HCS) has on proton propagation from SEP release sites to the Earth. We simulate proton propagation by integrating fully 3D trajectories near an analytically defined flat current sheet, collecting comprehensive statistics into histograms, fluence maps, and virtual observer time profiles within an energy range of 1–800 MeV. We show that protons experience significant current sheet drift to distant longitudes, causing time profiles to exhibit multiple components, which are a potential source of confusing interpretations of observations. We find that variation of the current sheet thickness within a realistic parameter range has little effect on particle propagation. We show that the IMF configuration strongly affects the deceleration of protons. We show that in our model, the presence of a flat equatorial HCS in the inner heliosphere limits the crossing of protons into the opposite hemisphere.

  5. Development of the Brazilian national sheet scintillator converter of neutron

    International Nuclear Information System (INIS)

    Barbosa, Andre Luis Nunes

    2008-03-01

    Both the national domain of the technology for the separation of rare earth elements and the large reserves of these minerals in Brazilian territory, motivated the study of national sheets scintillators converter of neutrons, using a granular mixture Gd 2 O 3 -Zn S:Ag. Three methodologies were used for the manufacture of such sheets, namely: deposition done with a compressed-air gun on a sheet of cellulose type CG3460-3M; fusion of granular mixture with EVA in the mixing chamber and deposition of granular mixture on the substrate of EVA. It was used the flux of the order of 4,46 x 10 5 neutrons thermic/cm 2 .s, coming from the channel irradiation, J-9, of the reactor Argonauta/IEN/CNEN and the radiographic film AA-400 Kodak Industrex. The performances of national scintillator neutrons converter sheets were analyzed and the images obtained with the, demonstrated that the methodologies proposed are technically feasible and can contribute to the reduction of cost of this technique for NDA, but which lack optimization is aimed at increasing the number of photons of light to allow its use in neutrongraphies in Real Time (NRTR). (author)

  6. Corona Formation and Heat Loss on Venus by Coupled Upwelling and Delamination

    Science.gov (United States)

    Smrekar, Suzanne E.; Stofan, Ellen R.

    1997-01-01

    Coronae are volcanotectonic features that are unique to Venus and are interpreted to be small-scale upwellings. A model in which upwelling causes delamination at the edge of the plume head, along with deformation of a pre-existing depleted mantel Layer, can produce the full range of topographic forms of coronae. If half of the coronae are active, delamination of the lower lithosphere could account for about 10% of venus's heat loss, with another 15% due to upwelling. Delamination may occur in other geologic enviroment and could help account for 'Venus' heat loss 'deficit'.

  7. Can a time-stratigraphic classification system be developed for Venus?

    Science.gov (United States)

    Tanaka, K. L.; Schaber, G. G.

    1992-01-01

    Magellan radar images reveal that Venus' exposed geologic record covers a relatively short and recent time span, as indicated by the low density of impact craters across the planet. Therefore, because impact cratering in itself will not be a useful tool to define geologic ages on Venus, it was questioned whether a useful stratigraphic scheme can be developed for the planet. We believe that a venusian stratigraphy is possible and that it can be based on the following: (1) an examination of the rationale and methods that have been used to develop such schemes for the other planets; and (2) what can be gleaned from Magellan and other datasets of Venus.

  8. Terrestrial spreading centers under Venus conditions - Evaluation of a crustal spreading model for Western Aphrodite Terra

    Science.gov (United States)

    Sotin, C.; Senske, D. A.; Head, J. W.; Parmentier, E. M.

    1989-01-01

    The model of Reid and Jackson (1981) for terrestrial spreading centers is applied to Venus conditions. On the basis of spreading rate, mantle temperature, and surface temperature, the model predicts both isostatic topography and crustal thickness. The model and Pioneer Venus altimetry and gravity data are used to test the hypothesis of Head and Crumpler (1987) that Western Aphrodite Terra is the location of crustal spreading on Venus. It is concluded that a spreading center model for Ovda Regio in Western Aphrodite Terra could account for the observed topography and line-of-sight gravity anomalies found in the Pioneer data.

  9. Oxygen ionization rates at Mars and Venus - Relative contributions of impact ionization and charge exchange

    Science.gov (United States)

    Zhang, M. H. G.; Luhmann, J. G.; Nagy, A. F.; Spreiter, J. R.; Stahara, S. S.

    1993-01-01

    Oxygen ion production rates above the ionopauses of Venus and Mars are calculated for photoionization, charge exchange, and solar wind electron impact ionization processes. The latter two require the use of the Spreiter and Stahara (1980) gas dynamic model to estimate magnetosheath velocities, densities, and temperatures. The results indicate that impact ionization is the dominant mechanism for the production of O(+) ions at both Venus and Mars. This finding might explain both the high ion escape rates measured by Phobos 2 and the greater mass loading rate inferred for Venus from the bow shock positions.

  10. DAVINCI: Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging

    Science.gov (United States)

    Glaze, Lori S.; Garvin, James B.; Robertson, Brent; Johnson, Natasha M.; Amato, Michael J.; Thompson, Jessica; Goodloe, Colby; Everette, Dave

    2017-01-01

    DAVINCI is one of five Discovery-class missions selected by NASA in October 2015 for Phase A studies. Launching in November 2021 and arriving at Venus in June of 2023, DAVINCI would be the first U.S. entry probe to target Venus atmosphere in 45 years. DAVINCI is designed to study the chemical and isotopic composition of a complete cross-section of Venus atmosphere at a level of detail that has not been possible on earlier missions and to image the surface at optical wavelengths and process-relevant scales.

  11. Non-dissipative shapable sheet

    Science.gov (United States)

    Oppenheimer, Naomi; Witten, Thomas

    2014-03-01

    A sheet of paper that has been crumpled and flattened retains some amount of shapability that a bare, uncrumpled, sheet does not have: when deformed by external forces, it retains the deformed shape after the forces are removed. Using a frustrated two dimensional lattice of springs, we show that such shapability can be attained in a non-dissipative system. Numerical investigations suggest an extensive number of bistable energy minima using several variants of this scheme. The numerical sheet can be bent into a nearly-closed cylinder that holds its shape. We verify that the deformed shape is locally stable and compare its bending modulus in the deformed state with that in the initial flat state. We investigate the threshold for non-elastic deformation using various kinds of forcing.

  12. Root-growth-inhibiting sheet

    Science.gov (United States)

    Burton, Frederick G.; Cataldo, Dominic A.; Cline, John F.; Skiens, W. Eugene; Van Voris, Peter

    1993-01-01

    In accordance with this invention, a porous sheet material is provided at intervals with bodies of a polymer which contain a 2,6-dinitroaniline. The sheet material is made porous to permit free passage of water. It may be either a perforated sheet or a woven or non-woven textile material. A particularly desirable embodiment is a non-woven fabric of non-biodegradable material. This type of material is known as a "geotextile" and is used for weed control, prevention of erosion on slopes, and other landscaping purposes. In order to obtain a root repelling property, a dinitroaniline is blended with a polymer which is attached to the geotextile or other porous material.

  13. Geologic map of the Rusalka Planitia Quadrangle (V-25), Venus

    Science.gov (United States)

    Young, Duncan A.; Hansen, Vicki L.

    2003-01-01

    The Rusalka Planitia quadrangle (herein referred to as V-25) occupies an 8.1 million square kilometer swath of lowlands nestled within the eastern highlands of Aphrodite Terra on Venus. The region (25?-0? N., 150?-180? E.) is framed by the crustal plateau Thetis Regio to the southwest, the coronae of the Diana-Dali chasmata complex to the south, and volcanic rise Atla Regio to the west. Regions to the north, and the quadrangle itself, are part of the vast lowlands, which cover four-fifths of the surface of Venus. The often-unspectacular lowlands of Venus are typically lumped together as ridged or regional plains. However, detailed mapping reveals the mode of resurfacing in V-25's lowlands: a mix of corona-related flow fields and local edifice clusters within planitia superimposed on a background of less clearly interpretable extended flow fields, large volcanoes, probable corona fragments, and edifice-flow complexes. The history detailed within the Rusalka Planitia quadrangle is that of the extended evolution of long-wavelength topographic basins in the presence of episodes of extensive corona-related volcanism, pervasive low-intensity small-scale eruptions, and an early phase of regional circumferential shortening centered on central Aphrodite Terra. Structural reactivation both obscures and illuminates the tectonic development of the region. The data are consistent with progressive lithospheric thickening, although the critical lack of an independent temporal marker on Venus severely hampers our ability to test this claim and correlate between localities. Two broad circular basins dominate V-25 geology: northern Rusalka Planitia lies in the southern half of the quadrangle, whereas the smaller Llorona Planitia sits along the northwestern corner of V-25. Similar large topographic basins occur throughout the lowlands of Venus, and gravity data suggest that some basins may represent dynamic topography over mantle downwellings. Both planitiae include coronae and

  14. Sheet Bending using Soft Tools

    Science.gov (United States)

    Sinke, J.

    2011-05-01

    Sheet bending is usually performed by air bending and V-die bending processes. Both processes apply rigid tools. These solid tools facilitate the generation of software for the numerical control of those processes. When the lower rigid die is replaced with a soft or rubber tool, the numerical control becomes much more difficult, since the soft tool deforms too. Compared to other bending processes the rubber backed bending process has some distinct advantages, like large radius-to-thickness ratios, applicability to materials with topcoats, well defined radii, and the feasibility of forming details (ridges, beads). These advantages may give the process exclusive benefits over conventional bending processes, not only for industries related to mechanical engineering and sheet metal forming, but also for other disciplines like Architecture and Industrial Design The largest disadvantage is that also the soft (rubber) tool deforms. Although the tool deformation is elastic and recovers after each process cycle, the applied force during bending is related to the deformation of the metal sheet and the deformation of the rubber. The deformation of the rubber interacts with the process but also with sheet parameters. This makes the numerical control of the process much more complicated. This paper presents a model for the bending of sheet materials using a rubber lower die. This model can be implemented in software in order to control the bending process numerically. The model itself is based on numerical and experimental research. In this research a number of variables related to the tooling and the material have been evaluated. The numerical part of the research was used to investigate the influence of the features of the soft lower tool, like the hardness and dimensions, and the influence of the sheet thickness, which also interacts with the soft tool deformation. The experimental research was focused on the relation between the machine control parameters and the most

  15. Ice sheet hydrology - a review

    International Nuclear Information System (INIS)

    Jansson, Peter; Naeslund, Jens-Ove; Rodhe, Lars

    2007-03-01

    This report summarizes the theoretical knowledge on water flow in and beneath glaciers and ice sheets and how these theories are applied in models to simulate the hydrology of ice sheets. The purpose is to present the state of knowledge and, perhaps more importantly, identify the gaps in our understanding of ice sheet hydrology. Many general concepts in hydrology and hydraulics are applicable to water flow in glaciers. However, the unique situation of having the liquid phase flowing in conduits of the solid phase of the same material, water, is not a commonly occurring phenomena. This situation means that the heat exchange between the phases and the resulting phase changes also have to be accounted for in the analysis. The fact that the solidus in the pressure-temperature dependent phase diagram of water has a negative slope provides further complications. Ice can thus melt or freeze from both temperature and pressure variations or variations in both. In order to provide details of the current understanding of water flow in conjunction with deforming ice and to provide understanding for the development of ideas and models, emphasis has been put on the mathematical treatments, which are reproduced in detail. Qualitative results corroborating theory or, perhaps more often, questioning the simplifications made in theory, are also given. The overarching problem with our knowledge of glacier hydrology is the gap between the local theories of processes and the general flow of water in glaciers and ice sheets. Water is often channelized in non-stationary conduits through the ice, features which due to their minute size relative to the size of glaciers and ice sheets are difficult to incorporate in spatially larger models. Since the dynamic response of ice sheets to global warming is becoming a key issue in, e.g. sea-level change studies, the problems of the coupling between the hydrology of an ice sheet and its dynamics is steadily gaining interest. New work is emerging

  16. Ice sheet hydrology - a review

    Energy Technology Data Exchange (ETDEWEB)

    Jansson, Peter; Naeslund, Jens-Ove [Dept. of Physical Geography and Quaternary Geology, Stockholm Univ., Stockholm (Sweden); Rodhe, Lars [Geological Survey of Sweden, Uppsala (Sweden)

    2007-03-15

    This report summarizes the theoretical knowledge on water flow in and beneath glaciers and ice sheets and how these theories are applied in models to simulate the hydrology of ice sheets. The purpose is to present the state of knowledge and, perhaps more importantly, identify the gaps in our understanding of ice sheet hydrology. Many general concepts in hydrology and hydraulics are applicable to water flow in glaciers. However, the unique situation of having the liquid phase flowing in conduits of the solid phase of the same material, water, is not a commonly occurring phenomena. This situation means that the heat exchange between the phases and the resulting phase changes also have to be accounted for in the analysis. The fact that the solidus in the pressure-temperature dependent phase diagram of water has a negative slope provides further complications. Ice can thus melt or freeze from both temperature and pressure variations or variations in both. In order to provide details of the current understanding of water flow in conjunction with deforming ice and to provide understanding for the development of ideas and models, emphasis has been put on the mathematical treatments, which are reproduced in detail. Qualitative results corroborating theory or, perhaps more often, questioning the simplifications made in theory, are also given. The overarching problem with our knowledge of glacier hydrology is the gap between the local theories of processes and the general flow of water in glaciers and ice sheets. Water is often channelized in non-stationary conduits through the ice, features which due to their minute size relative to the size of glaciers and ice sheets are difficult to incorporate in spatially larger models. Since the dynamic response of ice sheets to global warming is becoming a key issue in, e.g. sea-level change studies, the problems of the coupling between the hydrology of an ice sheet and its dynamics is steadily gaining interest. New work is emerging

  17. Sheet Beam Klystron Instability Analysis

    International Nuclear Information System (INIS)

    Bane, K.

    2009-01-01

    Using the principle of energy balance we develop a 2D theory for calculating growth rates of instability in a two-cavity model of a sheet beam klystron. An important ingredient is a TE-like mode in the gap that also gives a longitudinal kick to the beam. When compared with a self-consistent particle-in-cell calculation, with sheet beam klystron-type parameters, agreement is quite good up to half the design current, 65 A; at full current, however, other, current-dependent effects come in and the results deviate significantly

  18. Hydrogeological map of Kabo Sheet 80NW topographical sheet 1 ...

    African Journals Online (AJOL)

    A hydro geological mapping of the Federal Surveys of Nigeria, Kabo Sheet 80 NW, on scale 1:50,000 were made with areal coverage of 729Km2 on the Crystalline Basement Complex, and the hydrogeoogical maps produced are maps of depth to the water table and maps of configuration peak of dry season and wet ...

  19. Earth's glacial record and its tectonic setting

    Science.gov (United States)

    Eyles, N.

    1993-09-01

    clearly established glacial parentage. The same remarks apply to many successions of laminated and thin-bedded facies interpreted as "varvites". Despite suggestions of much lower values of solar luminosity (the weak young sun hypothesis), the stratigraphic record of Archean glaciations is not extensive and may be the result of non-preservation. However, the effects of very different Archean global tectonic regimes and much higher geothermal heat flows, combined with a Venus-like atmosphere warmed by elevated levels of CO 2, cannot be ruled out. The oldest unambiguous glacial succession in Earth history appears to be the Early Proterozoic Gowganda Formation of the Huronian Supergroup in Ontario; the age of this event is not well-constrained but glaciation coincided with regional rifting, and may be causally related to, oxygenation of Earth's atmosphere just after 2300 Ma. New evidence that oxygenation is tectonically, not biologically driven, stresses the intimate relationship between plate tectonics, evolution of the atmosphere and glaciation. Global geochemical controls, such as elevated atmospheric CO 2 levels, may be responsible for a long mid-Proterozoic non-glacial interval after 2000 Ma that was terminated by the Late Proterozoic glaciations just after 800 Ma. A persistent theme in both Late Proterozoic and Phanerozoic glaciations is the adiabatic effect of tectonic uplift, either along collisional margins or as a result of passive margin uplifts in areas of extended crust, as the trigger for glaciation; the process is reinforced by global geochemical feedback, principally the drawdown of atmospheric CO 2 and Milankovitch "astronomical" forcing but these are unlikely, by themselves, to inititiate glaciation. The same remarks apply to late Cenozoic glaciations. Late Proterozoic glacially-influenced strata occur on all seven continents and fall into two tectonostratigraphic types. In the first category are thick sucessions of turbidites and mass flows deposited along

  20. Formation of sheeting joints in Yosemite National Park, California

    Science.gov (United States)

    Martel, S. J.

    2009-04-01

    The formation of sheeting joints (i.e., "exfoliation joints"), opening mode fractures subparallel to the Earth's surface, has been a classic unresolved problem in geology. Diverse new observations and analyses support the hypothesis that sheeting joints develop in response to a near-surface tension induced by compressive stresses parallel to a convex slope (hypothesis 1) rather than the conventional explanation that the joints form as a result of removal of overburden by erosion (hypothesis 2). The opening mode displacements across the joints together with the absence of mineral precipitates within the joints mean that sheeting joints open in response to a near-surface tension normal to the surface (N) rather than a pressurized fluid. An absolute tension must arise in the shallow subsurface if a plot of N as a function of depth normal to the surface (z) has a positive slope at the surface (z=0). The differential equations of static equilibrium require that this slope (derivative) equals k2 P22 + k3 P33 - ?g cosβ, where k2 and k3 are the principal curvatures of the surface, P22 and P33 are the respective surface-parallel normal stresses along the principal curvatures, ? is the material density, g is gravitational acceleration, and β is the slope. This derivative will be positive and sheeting joints can open if the surface-parallel stress in at least one direction is sufficiently compressive (negative) and the curvature in that direction is sufficiently convex (negative). Hypotheses 1 and 2 are being tested using geologic mapping and aerial LIDAR data from Yosemite National Park, California. The abundance of sheeting joints on convex ridges there, where erosion is a local minimum, coupled with their scarcity in the adjacent concave valleys, where erosion is a local maximum, is consistent with hypothesis 1 but inconsistent with hypothesis 2. At several sites with sheeting joints, measurements of the current topographic curvatures and the current surface

  1. The relationship between fluctuating plasma sheet and substorm development: Cluster and Double Star TC1 case study

    Science.gov (United States)

    Takada, T.; Nakamura, R.; Zhang, T. L.; Asano, Y.; Baumjohann, W.; Klecker, B.; Reme, H.; Balogh, A.; Carr, C. M.; Frey, H. U.

    During magnetospheric substorms the magnetic field configuration in the near-Earth tail often changes drastically from tail-like to a more dipolar configuration This dipolarization seems to be caused by the disruption of cross-tail currents in the near-Earth tail or by bursty bulk flows BBFs in the midtail Around the disturbances it is also known that the plasma sheet sometimes fluctuates strongly magnetotail flapping kink-like motion or sausage modes The relationship between such a fluctuating plasma sheet and BBFs dipolarization is still unknown In this study conjunction events of Cluster in the midtail region and Double Star TC1 in near-Earth tail are investigated We present two global dipolarization events observed by Cluster and TC1 on Sep 3 2004 that were preceded by a fluctuating plasma sheet Dipolarization took place associated with a global onset and a fluctuating plasma sheet was observed during periods of pseudo-breakup In the first case a fluctuation of plasma sheet kink-like preceded an auroral brightening In the second case a fluctuating plasma sheet kink-like and sausage mode followed the auroral brightening In both cases the following substorm expands globally and both spacecraft observe the propagating dipolarization front We discuss how the fluctuating plasma sheet relates to localized activation during the growth phase and leads to a large scale onset of the substorm

  2. Fermi surfaces of rare-earth nickel borocarbides

    Energy Technology Data Exchange (ETDEWEB)

    Dugdale, S B; Utfeld, C; Wilkinson, I; Laverock, J; Major, Zs; Alam, M A [H H Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Canfield, P C [Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)], E-mail: s.b.dugdale@bristol.ac.uk

    2009-01-15

    A full three-dimensional study of the Fermi surface of LuNi{sub 2}B{sub 2}C is presented, using positron annihilation. The previously identified nesting feature, part of a complex multiply connected Fermi surface sheet, is clearly revealed and observed to extend across approximately 20% of the Brillouin zone. A cuboidal Fermi surface sheet is also found, in agreement with de Haas-van Alphen observations. The Fermi surface topology of the rare-earth nickel borocarbides is shown to vary little for rare-earth elements such as Er, Tm and Yb, suggesting that this topology is broadly common.

  3. Circumlunar Free-Return Cycler Orbits for a Manned Earth-Moon Space Station

    Science.gov (United States)

    Genova, Anthony L.; Aldrin, Buzz

    2015-01-01

    Multiple free-return circumlunar cycler orbits were designed to allow regular travel between the Earth and Moon by a manned space station. The presented cycler orbits contain circumlunar free-return "figure-8" segments and yield lunar encounters every month. Smaller space "taxi" vehicles can rendezvous with (and depart from) the cycling Earth-Moon space station to enter lunar orbit (and/or land on the lunar surface), return to Earth, or reach destinations including Earth-Moon L1 and L2 halo orbits, near-Earth objects (NEOs), Venus, and Mars. To assess the practicality of the selected orbits, relevant cycler characteristics (including (Delta)V maintenance requirements) are presented and compared.

  4. Higher Education Act. Fact Sheet.

    Science.gov (United States)

    National Council on Disability, 2004

    2004-01-01

    This fact sheet highlights the challenges for students with disabilities in the nation's university system and recommends solutions that would result in better support systems for postsecondary students with disabilities. This document discusses several interrelated issues that impact student preparation and access to postsecondary education. The…

  5. Fact Sheet: Vulnerable Young Children

    Science.gov (United States)

    Shaw, Evelyn, Comp.; Goode, Sue, Comp.

    2008-01-01

    This fact sheet provides data on infants, toddlers and young children who are experiencing high stress as a result of a number of risk factors specifically identified in the Individuals with Disabilities Education Improvement Act of 2004 (IDEA 2004), including substantiated abuse or neglect, foster care placement, homelessness, exposure to family…

  6. Off-Balance Sheet Financing.

    Science.gov (United States)

    Adams, Matthew C.

    1998-01-01

    Examines off-balance sheet financing, the facilities use of outsourcing for selected needs, as a means of saving operational costs and using facility assets efficiently. Examples of using outside sources for energy supply and food services, as well as partnering with business for facility expansion are provided. Concluding comments address tax…

  7. Learning from Balance Sheet Visualization

    Science.gov (United States)

    Tanlamai, Uthai; Soongswang, Oranuj

    2011-01-01

    This exploratory study examines alternative visuals and their effect on the level of learning of balance sheet users. Executive and regular classes of graduate students majoring in information technology in business were asked to evaluate the extent of acceptance and enhanced capability of these alternative visuals toward their learning…

  8. Stabilization of Inviscid Vortex Sheets

    Science.gov (United States)

    Protas, Bartosz; Sakajo, Takashi

    2017-11-01

    In this study we investigate the problem of stabilizing inviscid vortex sheets via feedback control. Such models, expressed in terms of the Birkhoff-Rott equation, are often used to describe the Kevin-Helmholtz instability of shear layers and are known to be strongly unstable to small-scale perturbations. First, we consider the linear stability of a straight vortex sheet in the periodic setting with actuation in the form of an array of point vortices or sources located a certain distance away from the sheet. We establish conditions under which this system is controllable and observable. Next, using methods of the linear control theory, we synthesize a feedback control strategy which stabilizes a straight vortex sheet in the linear regime. Given the poor conditioning of the discretized problem, reliable solution of the resulting algebraic Riccati equation requires the use of high-precision arithmetic. Finally, we demonstrate that this control approach also succeeds in the nonlinear regime, provided the magnitude of the initial perturbation is sufficiently small.

  9. Magnetic Resonance Facility (Fact Sheet)

    Energy Technology Data Exchange (ETDEWEB)

    2012-03-01

    This fact sheet provides information about Magnetic Resonance Facility capabilities and applications at NREL's National Bioenergy Center. Liquid and solid-state analysis capability for a variety of biomass, photovoltaic, and materials characterization applications across NREL. NREL scientists analyze solid and liquid samples on three nuclear magnetic resonance (NMR) spectrometers as well as an electron paramagnetic resonance (EPR) spectrometer.

  10. Gravity-assist trajectories to Venus, Mars, and the ice giants: Mission design with human and robotic applications

    Science.gov (United States)

    Hughes, Kyle M.

    Gravity-assist trajectories to Uranus and Neptune are found (with the allowance of impulsive maneuvers using chemical propulsion) for launch dates ranging from 2024 to 2038 for Uranus and 2020 to 2070 for Neptune. Solutions are found using a patched conic model with analytical ephemeris via the Satellite Tour Design Program (STOUR), originally developed at the Jet Propulsion Laboratory (JPL). Delivered payload mass is computed for all solutions for select launch vehicles, and attractive solutions are identified as those that deliver a specified amount of payload mass into orbit at the target body in minimum time. The best cases for each launch year are cataloged for orbiter missions to Uranus and Neptune. Solutions with sufficient delivered payload for a multi-planet mission (e.g. sending a probe to Saturn on the way to delivering an orbiter at Uranus) become available when the Space Launch System (SLS) launch vehicle is employed. A set of possible approach trajectories are modeled at the target planet to assess what (if any) adjustments are needed for ring avoidance, and to determine the probe entry conditions. Mars free-return trajectories are found with an emphasis on short flight times for application to near-term human flyby missions (similar to that of Inspiration Mars). Venus free-returns are also investigated and proposed as an alternative to a human Mars flyby mission. Attractive Earth-Mars free-return opportunities are identified that use an intermediate Venus flyby. One such opportunity, in 2021, has been adopted by the Inspiration Mars Foundation as a backup to the currently considered 2018 Mars free-return opportunity. Methods to establish spacecraft into Earth-Mars cycler trajectories are also investigated to reduce the propellant cost required to inject a 95-metric ton spacecraft into a cycler orbit. The establishment trajectories considered use either a V-infinity leveraging maneuver or low thrust. The V-infinity leveraging establishment

  11. Geologic Mapping of the Helen Planitia Quadrangle (V52), Venus: The First Results

    Science.gov (United States)

    López, I.; Hansen, V. L.

    2003-03-01

    Preliminary geologic mapping of the Helen Planitia Quadrangle (V52), Venus is in progress. This area allows the investigation of the transition between the mesolands of Eastern Parga Chasmata and the lowlands of Helen Planitia.

  12. Constraints A-Z for the Surface Evolution of Venus, and Proposed History

    Science.gov (United States)

    Hansen, V. L.

    2012-03-01

    This contribution summarizes constraints A through Z for surface evolution of Venus, as derived from geologic mapping and analysis from a wide range of studies. All viable resurfacing models must be able to accommodate each of these constraints.

  13. PVO VENUS ONMS BROWSE NEUTRAL DENSITY 12 SECOND V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set was designed to determine the composition of the neutral thermosphere/exosphere of Venus. The term composition includes both the type of neutral gases...

  14. Harsh Environment Gas Sensor Array for Venus Atmospheric Measurements, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Makel Engineering and the Ohio State University propose to develop a harsh environment tolerant gas sensor array for atmospheric analysis in future Venus missions....

  15. Thermal Management System for Long-Lived Venus Landers, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Long-lived Venus landers require power and cooling. Heat from the roughly 64 General Purpose Heat Source (GPHS) modules must be delivered to the convertor with...

  16. Venus Interior Probe Using In-situ Power and Propulsion (VIP-INSPR), Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Venus, despite being our closest neighboring planet, is under-explored due to its hostile environment. The atmosphere is composed primarily of CO2, with a 92 bar...

  17. The boundary layers as the primary transport regions of the earth's magnetotail

    Science.gov (United States)

    Eastman, T. E.; Frank, L. A.; Huang, C. Y.

    1985-01-01

    A comprehensive survey of ISEE and IMP LEPEDEA plasma measurements in the earth's magnetotail reveals that the magnetospheric boundary layer and the plasma sheet boundary layer are the primary transport regions there. These plasma measurements also reveal various components of the plasma sheet, including the central plasma sheet and plasma sheet boundary layer. A significant new result reported here is that of cold- and hot-plasma components that are spatially co-present within the central plasma sheet. Such plasma components cannot be explained merely by temporal variations in spectra involving the entire plasma sheet. Contributions to a low temperature component of the plasma sheet enter directly from the boundary layer located along the magnetotail flanks. Field-aligned flows predominate within the plasma sheet boundary layer which is almost always present and is located near the high- and low-latitude border of the plasma sheet. The plasma sheet boundary layer comprises highly anisotropic ion distributions, including counter-streaming ion beams, that evolve into the hot, isotropic component of the plasma sheet. Tailward acceleration regions generate these ion beams with plasma input from the magnetospheric boundary layer. Antisunward-flowing ion beams, at E/q less than 1 kV and of ionospheric composition, are frequently observed in the plasma sheet boundary layer and in tail lobes. These ion beams are likely accelerated at low altitude over the polar cap and especially along auroral field lines.

  18. The SPICAV-SOIR instrument probing the atmosphere of Venus: an overview

    Science.gov (United States)

    Trompet, Loïc; Mahieux, Arnaud; Wilquet, Valérie; Robert, Séverine; Chamberlain, Sarah; Thomas, Ian; Carine Vandaele, Ann; Bertaux, Jean-Loup

    2016-04-01

    The Solar Occultation in the Infrared (SOIR) channel mounted on top of the SPICAV instrument of the ESA's Venus Express mission has observed the atmosphere of Venus during more than eight years. This IR spectrometer (2.2-4.3 μm) with a high spectral resolution (0.12 cm-1) combined an echelle grating with an acousto-optic tunable filter for order selection. SOIR performed more than 1500 solar occultation measurements leading to about two millions spectra. The Royal Belgian Institute for Space Aeronomy (BIRA-IASB) was in charge of SOIR's development and operations as well as its data pipeline. BIRA-IASB carried out several studies on the composition of Venus mesosphere and lower thermosphere: carbon dioxide, carbon monoxide, hydrogen halide (HF, HCl, DF, DCl), sulfur dioxide, water (H2O, HDO) as well as sulphuric acid aerosols in the upper haze of Venus. Density and temperature profiles of the upper atmosphere of Venus (60 km to 170 km) at the terminator have been retrieved from SOIR's spectra using different assumptions, wherein the hydrostatic equilibrium and the local thermodynamical equilibrium in the radiative transfer calculations. These results allow us to produce an Atmospheric model of Venus called Venus Atmosphere from SOIR measurements at the Terminator (VAST). Data obtained by SOIR will also contribute to update the Venus International Reference Atmosphere (VIRA). Recently, the treatment of the raw data to transmittance has been optimized, and a new dataset of spectra has been produced. All raw spectra (PSA level 2) as well as calibrated spectra (PSA level 3) have been delivered to ESA's Planetary Science Archive (PDSPSA). Consequently the re-analysis of all spectra has been undergone. We will briefly present the improvements implemented in the data pipeline. We will also show a compilation of results obtained by the instrument considering the complete mission duration.

  19. Present-day mass changes for the Greenland ice sheet and their interaction with bedrock adjustment

    NARCIS (Netherlands)

    Olaizola, M.; van de Wal, R.S.W.; Helsen, M.M.; de Boer, B.

    2011-01-01

    Since the launch in 2002 of the Gravity Recovery and Climate Experiment (GRACE) satellites, several estimates of the mass balance of the Greenland Ice Sheet (GrIS) have been produced. To obtain ice mass changes estimates, data need to be corrected for the effect of deformation changes of the Earth's

  20. Accelerated mass loss from Greenland ice sheet : Links to atmospheric circulation in the North Atlantic

    NARCIS (Netherlands)

    Seo, Ki-Weon; Waliser, Duane E.; Lee, Choon-Ki; Tian, Baijun; Scambos, Ted; Kim, Baek-Min; van Angelen, Jan H.|info:eu-repo/dai/nl/325922470; van den Broeke, Michiel R.|info:eu-repo/dai/nl/073765643

    Understanding the mechanisms that drive the mass imbalance of the Greenland ice sheet (GrIS) is critical to the accurate projection of its contribution to future sea level rise. Greenland's ice mass loss has been accelerating recently. Using satellite Earth-gravity and regional climate model data,

  1. Last Interglacial climate and sea-level evolution from a coupled ice sheet-climate model

    NARCIS (Netherlands)

    Goelzer, Heiko; Huybrechts, Philippe; Marie-France, Loutre; Fichefet, Thierry

    2016-01-01

    As the most recent warm period in Earth's history with a sea-level stand higher than present, the Last Interglacial (LIG, ∼130 to 115kyrgBP) is often considered a prime example to study the impact of a warmer climate on the two polar ice sheets remaining today. Here we simulate the Last Interglacial

  2. Strategic surfaces in sheet metal forming

    DEFF Research Database (Denmark)

    Olsson, David Dam; Andreasen, Jan Lasson; Bay, Niels

    Out-line: Introduction to tribology in sheet metal forming Developed strategic surfaces Tribological testing of strategic surfaces Conclusion......Out-line: Introduction to tribology in sheet metal forming Developed strategic surfaces Tribological testing of strategic surfaces Conclusion...

  3. Whooping Cough (Pertussis) - Fact Sheet for Parents

    Science.gov (United States)

    ... months 4 through 6 years Fact Sheet for Parents Color [2 pages] Español: Tosferina (pertussis) The best ... according to the recommended schedule. Fact Sheets for Parents Diseases and the Vaccines that Prevent Them Chickenpox ...

  4. Obliquity-paced Pliocene West Antarctic ice sheet oscillations

    Science.gov (United States)

    Naish, T.; Powell, R.; Levy, R.; Wilson, G.; Scherer, R.; Talarico, F.; Krissek, L.; Niessen, F.; Pompilio, M.; Wilson, T.; Carter, L.; DeConto, R.; Huybers, P.; McKay, R.; Pollard, D.; Ross, J.; Winter, D.; Barrett, P.; Browne, G.; Cody, R.; Cowan, E.; Crampton, J.; Dunbar, G.; Dunbar, N.; Florindo, F.; Gebhardt, C.; Graham, I.; Hannah, M.; Hansaraj, D.; Harwood, D.; Helling, D.; Henrys, S.; Hinnov, L.; Kuhn, G.; Kyle, P.; Laufer, A.; Maffioli, P.; Magens, D.; Mandernack, K.; McIntosh, W.; Millan, C.; Morin, R.; Ohneiser, C.; Paulsen, T.; Persico, D.; Raine, I.; Reed, J.; Riesselman, C.; Sagnotti, L.; Schmitt, D.; Sjunneskog, C.; Strong, P.; Taviani, M.; Vogel, S.; Wilch, T.; Williams, T.

    2009-01-01

    Thirty years after oxygen isotope records from microfossils deposited in ocean sediments confirmed the hypothesis that variations in the Earth's orbital geometry control the ice ages1, fundamental questions remain over the response of the Antarctic ice sheets to orbital cycles2. Furthermore, an understanding of the behaviour of the marine-based West Antarctic ice sheet (WAIS) during the 'warmer-than-present' early-Pliocene epoch (5–3 Myr ago) is needed to better constrain the possible range of ice-sheet behaviour in the context of future global warming3. Here we present a marine glacial record from the upper 600 m of the AND-1B sediment core recovered from beneath the northwest part of the Ross ice shelf by the ANDRILL programme and demonstrate well-dated, 40-kyr cyclic variations in ice-sheet extent linked to cycles in insolation influenced by changes in the Earth's axial tilt (obliquity) during the Pliocene. Our data provide direct evidence for orbitally induced oscillations in the WAIS, which periodically collapsed, resulting in a switch from grounded ice, or ice shelves, to open waters in the Ross embayment when planetary temperatures were up to 3 °C warmer than today4 and atmospheric CO2 concentration was as high as 400 p.p.m.v. (refs 5, 6). The evidence is consistent with a new ice-sheet/ice-shelf model7 that simulates fluctuations in Antarctic ice volume of up to +7 m in equivalent sea level associated with the loss of the WAIS and up to +3 m in equivalent sea level from the East Antarctic ice sheet, in response to ocean-induced melting paced by obliquity. During interglacial times, diatomaceous sediments indicate high surface-water productivity, minimal summer sea ice and air temperatures above freezing, suggesting an additional influence of surface melt8 under conditions of elevated CO2.

  5. Fluvial geomorphology on Earth-like planetary surfaces: A review.

    Science.gov (United States)

    Baker, Victor R; Hamilton, Christopher W; Burr, Devon M; Gulick, Virginia C; Komatsu, Goro; Luo, Wei; Rice, James W; Rodriguez, J A P

    2015-09-15

    Morphological evidence for ancient channelized flows (fluvial and fluvial-like landforms) exists on the surfaces of all of the inner planets and on some of the satellites of the Solar System. In some cases, the relevant fluid flows are related to a planetary evolution that involves the global cycling of a volatile component (water for Earth and Mars; methane for Saturn's moon Titan). In other cases, as on Mercury, Venus, Earth's moon, and Jupiter's moon Io, the flows were of highly fluid lava. The discovery, in 1972, of what are now known to be fluvial channels and valleys on Mars sparked a major controversy over the role of water in shaping the surface of that planet. The recognition of the fluvial character of these features has opened unresolved fundamental questions about the geological history of water on Mars, including the presence of an ancient ocean and the operation of a hydrological cycle during the earliest phases of planetary history. Other fundamental questions posed by fluvial and fluvial-like features on planetary bodies include the possible erosive action of large-scale outpourings of very fluid lavas, such as those that may have produced the remarkable canali forms on Venus; the ability of exotic fluids, such as methane, to create fluvial-like landforms, as observed on Saturn's moon, Titan; and the nature of sedimentation and erosion under different conditions of planetary surface gravity. Planetary fluvial geomorphology also illustrates fundamental epistemological and methodological issues, including the role of analogy in geomorphological/geological inquiry.

  6. Large-scale Modeling of the Greenland Ice Sheet on Long Timescales

    DEFF Research Database (Denmark)

    Solgaard, Anne Munck

    is investigated as well as its early history. The studies are performed using an ice-sheet model in combination with relevant forcing from observed and modeled climate. Changes in ice-sheet geometry influences atmospheric flow (and vice versa) hereby changing the forcing patterns. Changes in the overall climate...... for the build-up of the Greenland ice sheet that lead to the intensification of the Northern Hemisphere glaciations at the end of the Pliocene. A study of output from the climate model, EC-EARTH, reveals some of the challenges faced when using this to force ice-sheet evolution or when full coupling of ice...... also alter the patterns. On this basis, output from a climate model is used to construct adaptive forcing patterns that are computationally fast and takes into account that the patterns respond to changes in a non-uniform way both spatially and temporally. The adaptive patterns were applied to study...

  7. Future Antarctic bed topography and its implications for ice sheet dynamics

    Science.gov (United States)

    Adhikari, S.; Ivins, E. R.; Larour, E.; Seroussi, H.; Morlighem, M.; Nowicki, S.

    2014-06-01

    The Antarctic bedrock is evolving as the solid Earth responds to the past and ongoing evolution of the ice sheet. A recently improved ice loading history suggests that the Antarctic Ice Sheet (AIS) has generally been losing its mass since the Last Glacial Maximum. In a sustained warming climate, the AIS is predicted to retreat at a greater pace, primarily via melting beneath the ice shelves. We employ the glacial isostatic adjustment (GIA) capability of the Ice Sheet System Model (ISSM) to combine these past and future ice loadings and provide the new solid Earth computations for the AIS. We find that past loading is relatively less important than future loading for the evolution of the future bed topography. Our computations predict that the West Antarctic Ice Sheet (WAIS) may uplift by a few meters and a few tens of meters at years AD 2100 and 2500, respectively, and that the East Antarctic Ice Sheet is likely to remain unchanged or subside minimally except around the Amery Ice Shelf. The Amundsen Sea Sector in particular is predicted to rise at the greatest rate; one hundred years of ice evolution in this region, for example, predicts that the coastline of Pine Island Bay will approach roughly 45 mm yr-1 in viscoelastic vertical motion. Of particular importance, we systematically demonstrate that the effect of a pervasive and large GIA uplift in the WAIS is generally associated with the flattening of reverse bed slope, reduction of local sea depth, and thus the extension of grounding line (GL) towards the continental shelf. Using the 3-D higher-order ice flow capability of ISSM, such a migration of GL is shown to inhibit the ice flow. This negative feedback between the ice sheet and the solid Earth may promote stability in marine portions of the ice sheet in the future.

  8. Future Antarctic Bed Topography and Its Implications for Ice Sheet Dynamics

    Science.gov (United States)

    Adhikari, Surendra; Ivins, Erik R.; Larour, Eric Y.; Seroussi, Helene L.; Morlighem, Mathieu; Nowicki, S.

    2014-01-01

    The Antarctic bedrock is evolving as the solid Earth responds to the past and ongoing evolution of the ice sheet. A recently improved ice loading history suggests that the Antarctic Ice Sheet (AIS) has generally been losing its mass since the Last Glacial Maximum. In a sustained warming climate, the AIS is predicted to retreat at a greater pace, primarily via melting beneath the ice shelves.We employ the glacial isostatic adjustment (GIA) capability of the Ice Sheet System Model (ISSM) to combine these past and future ice loadings and provide the new solid Earth computations for the AIS.We find that past loading is relatively less important than future loading for the evolution of the future bed topography. Our computations predict that the West Antarctic Ice Sheet (WAIS) may uplift by a few meters and a few tens of meters at years AD 2100 and 2500, respectively, and that the East Antarctic Ice Sheet is likely to remain unchanged or subside minimally except around the Amery Ice Shelf. The Amundsen Sea Sector in particular is predicted to rise at the greatest rate; one hundred years of ice evolution in this region, for example, predicts that the coastline of Pine Island Bay will approach roughly 45mmyr-1 in viscoelastic vertical motion. Of particular importance, we systematically demonstrate that the effect of a pervasive and large GIA uplift in the WAIS is generally associated with the flattening of reverse bed slope, reduction of local sea depth, and thus the extension of grounding line (GL) towards the continental shelf. Using the 3-D higher-order ice flow capability of ISSM, such a migration of GL is shown to inhibit the ice flow. This negative feedback between the ice sheet and the solid Earth may promote stability in marine portions of the ice sheet in the future.

  9. Distant plasma sheet ion distributions during reconnection

    OpenAIRE

    Owen, C. J.; Mist, R. T.

    2001-01-01

    Previous models of the plasma sheet following reconnection and current sheet acceleration predict 'lima-bean' ion distributions. These are inconsistent with observational constraints. We postulate that following initial interaction with the current sheet, a fraction of outflow ions are backscattered and re-encounter the current sheet. Fermi acceleration processes then generate an additional high-energy outflow population. In the backscatter region these ions form a complete shell in velocity ...

  10. The Quasi-monochromatic ULF Wave Boundary in the Venusian Foreshock: Venus Express Observations

    Science.gov (United States)

    Shan, Lican; Mazelle, Christian; Meziane, Karim; Romanelli, Norberto; Ge, Yasong S.; Du, Aimin; Lu, Quanming; Zhang, Tielong

    2018-01-01

    The location of ultralow-frequency (ULF) quasi-monochromatic wave onset upstream of Venus bow shock is explored using Venus Express magnetic field data. We report the existence of a spatial foreshock boundary behind which ULF waves are present. We have found that the ULF wave boundary at Venus is sensitive to the interplanetary magnetic field (IMF) direction like the terrestrial one and appears well defined for a cone angle larger than 30°. In the Venusian foreshock, the inclination angle of the wave boundary with respect to the Sun-Venus direction increases with the IMF cone angle. We also found that for the IMF nominal direction (θBX = 36°) at Venus' orbit, the value of this inclination angle is 70°. Moreover, we have found that the inferred velocity of an ion traveling along the ULF boundary is in a qualitative agreement with a quasi-adiabatic reflection of a portion of the solar wind at the bow shock. For an IMF nominal direction at Venus, the inferred bulk speed of ions traveling along this boundary is 1.07 VSW, sufficiently enough to overcome the solar wind convection. This strongly suggests that the backstreaming ions upstream of the Venusian bow shock provide the main energy source for the ULF waves.

  11. On the origin of plasma sheet reconfiguration during the substorm growth phase

    Science.gov (United States)

    Gordeev, Evgeny; Sergeev, Victor; Merkin, Viacheslav; Kuznetsova, Maria

    2017-09-01

    Recently, Hsieh and Otto (2014) suggested that transport of the closed magnetic flux to the dayside reconnection region may be a key process which controls the reconfiguration of magnetotail during the substorm growth phase. We investigate this problem using global self-consistent MHD simulations and confirm that magnetotail reconfiguration is essentially a 3-D process which cannot be fully described based on 2-D-like tail evolution powered by the magnetic flux loading into the lobes. We found that near-Earth return convection strength on the nightside is directly related to the intensity of dayside reconnection, which causes the formation of antisunward azimuthal pressure gradients that force plasma to flow toward the dayside magnetopause. This near-Earth part of global convection develops immediately after the onset of dayside reconnection and reaches a quasi-steady level in 10-15 min. Its magnitude exceeds the total sunward flux transport in the midtail plasma sheet at X≈-20RE by an order of magnitude, causing significant amount (0.1-0.2 GWb) of closed magnetic flux to be removed from the near-Earth plasma sheet during moderate substorm. In that region the Bz depletion and current sheet thinning are closely related to each other, and the local Jy(Bz) relationship in the simulations matches reasonably well the power law expression found in the plasma sheet. In summary, global simulations confirm quantitatively that near-Earth return convection is primarily responsible for the severe depletion of the closed magnetic flux in the plasma sheet, major tail stretching, and current sheet thinning in the near magnetotail at r < 15RE.

  12. Structural analysis of central and eastern Ovda Regio, Venus

    Science.gov (United States)

    Ghent, R. R.; Hansen, V. L.

    1997-03-01

    Ovda Regio is the largest of the Venusian crustal plateaus and lies in Western Aphrodite Terra, Venus. An understanding of the strain history of this region will provide a key to understanding the processes involved in the formation of Ovda Regio and of crustal plateaus in general. This paper reports on a detailed structural mapping and analysis of Ovda and implications for the tectonic evolution of Ovda and other crustal plateaus. The tectonic features of Ovda Regio were mapped using Magellan SAR images. The three major structures seen in Ovda Regio are folds, ribbons, and graben. The folds are interpreted to be contractional, and the graben and ribbons extensional. The strain history recorded in Ovda Regio involves early extension, followed by contraction, then later extension. This strain history is consistent with the formation of Ovda Regio by mantle upwelling.

  13. Venus' spectroscopic phase variation - Implications of the Mariner 10 photographs

    Science.gov (United States)

    Chamberlain, J. W.

    1975-01-01

    The recent ultraviolet photographs of Venus by Mariner 10 have shown an irregular cloud structure. There is an apparent tendency for clearing along a wide equatorial band more or less centered on the subsolar point. This synoptic picture is in marked contrast to the uniform cloud cover conventionally used in model calculations of the variation with phase of CO2 absorption bands. To illustrate the consequences of subsolar weakening of CO2 absorption, a mathematically simple (but realistically naive) model is used. Two conclusions are reached: (1) efforts to distinguish between single- and double-layer models for the clouds from spectroscopic data alone are not merely ambiguous (as argued earlier by Chamberlain and Smith); with present data they are hopeless; (2) the decrease in the CO2 absorption close to full phase, as reported by Young et al., could result entirely from an equatorial darkening that is relatively inconsequential at the crescent phase and increasingly predominant for fuller phases.

  14. "Chiriguano" Astronomy - Venus and a Guarani New Year

    Science.gov (United States)

    Pereira, Gonzalo

    A Supreme Decree emitted by the government of Bolivia instituted the celebration of the June solstices in view of the fact that the indigenous people, both the Andean highlands and the Amazon and Chaco, "have commemorated this event for thousands of years" (Gobierno del Estado Plurinacional de Bolivia, Decreto Supremo N° 0173, June16, 2009, La Paz). In the case of the lowlands' indigenous, particularly the Guarani people, the decree mentions the planet Venus as the argument for this celebration. In this case of study and in light of astronomical and ethnographic evidence, we analyze the relevance of this decree in the case of the Guarani people of the Bolivian Chaco region, known as "Chiriguanos".

  15. Venus atmosphere profile from a maximum entropy principle

    Directory of Open Access Journals (Sweden)

    L. N. Epele

    2007-10-01

    Full Text Available The variational method with constraints recently developed by Verkley and Gerkema to describe maximum-entropy atmospheric profiles is generalized to ideal gases but with temperature-dependent specific heats. In so doing, an extended and non standard potential temperature is introduced that is well suited for tackling the problem under consideration. This new formalism is successfully applied to the atmosphere of Venus. Three well defined regions emerge in this atmosphere up to a height of 100 km from the surface: the lowest one up to about 35 km is adiabatic, a transition layer located at the height of the cloud deck and finally a third region which is practically isothermal.

  16. Comparative kinematical analyses of Venus flytrap (Dionaea muscipula snap traps

    Directory of Open Access Journals (Sweden)

    Simon Poppinga

    2016-05-01

    Full Text Available Although the Venus flytrap (Dionaea muscipula can be considered as one of the most extensively investigated carnivorous plants, knowledge is still scarce about diversity of the snap-trap motion, the functionality of snap traps under varying environmental conditions, and their opening motion. By conducting simple snap-trap closure experiments in air and under water, we present striking evidence that adult Dionaea snaps similarly fast in aerial and submersed states and, hence, is potentially able to gain nutrients from fast aquatic prey during seasonal inundation. We reveal three snapping modes of adult traps, all incorporating snap buckling, and show that millimeter-sized, much slower seedling traps do not yet incorporate such elastic instabilities. Moreover, opening kinematics of young and adult Dionaea snap traps reveal that reverse snap buckling is not performed, corroborating the assumption that growth takes place on certain trap lobe regions. Our findings are discussed in an evolutionary, biomechanical, functional–morphological and biomimetic context.

  17. 21 CFR 880.5180 - Burn sheet.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Burn sheet. 880.5180 Section 880.5180 Food and... Burn sheet. (a) Identification. A burn sheet is a device made of a porous material that is wrapped aroung a burn victim to retain body heat, to absorb wound exudate, and to serve as a barrier against...

  18. Simulation of stationary sheet metal cutting processes

    NARCIS (Netherlands)

    Wisselink, H.H.; Huetink, Han

    1998-01-01

    In stationary sheet metal cutting processes, like guillotining and slitting, the sheet is cut progressively from one end to the other. This in contrary with transient processes (blanking) where the sheet is cut at once. Where transient shearing processes can be modelled in 2-D (plain strain or

  19. Simulation of the European ice sheet through the last glacial cycle and prediction of future glaciation

    International Nuclear Information System (INIS)

    Boulton, G.S.; Payne, A.

    1992-12-01

    Global climates of the recent past appear to correlate with patterns of variation in the earths orbit round the sun. As such orbital changes can be predicted into the future, it is argued that the pattern of natural long-term future change can also be estimated. From this, future trends of glaciation can be inferred. The physical and mathematical basis of a time-dependent, thermo mechanically coupled, three dimensional ice sheet model is described. The model is driven by changes in the equilibrium line altitude (ELA) on its surface. This causes flexure of the underlying lithosphere. The model is tuned to the maximum extension of the last (Weichselian) ice sheet and driven by an ELA fluctuation which reflects the NE Atlantic sea surface temperature fluctuation pattern during the last glacial cycle in such a way that the model reproduces the ice sheet margin at the glacial maximum. The distribution of internal ice sheet velocity, temperature, basal melting rate and sub glacial permafrost penetration are all computed. The model is then tested against its predictions of the areal pattern of ice sheet expansion and decay, the pattern of crustal flexure and relative sea level change, and the distribution of till produced by the last European ice sheet. The tested model is then driven by predictions of future climate change to produce simulations of future ice sheet glaciation in northern Europe

  20. Magellan radio occultation measurements of atmospheric waves on Venus

    Science.gov (United States)

    Hinson, David P.; Jenkins, J. M.

    1995-01-01

    Radio occultation experiments were conducted at Venus on three consecutive orbits of the Magellan spacecraft in October 1991. Each occultation occurred over the same topography (67 deg N, 127 deg E) and at the same local time (22 hr 5 min), but the data are sensitive to zonal variations because the atmosphere rotates significantly during one orbit. Through comparisons between observations and predictions of standard wave theory, we have demonstrated that small-scale oscillations in retrieved temperature profiles as well as scintillations in received signal intensity are caused by a spectrum of vertically propagating internal gravity waves. There is a strong similarity between the intensity scintillations observed here and previous measurements, which pertain to a wide range of locations and experiment dates. This implies that the same basic phenomenon underlies all the observations and hence that gravity waves are a persistent, global feature of Venus' atmosphere. We obtained a fairly complete characterization of a gravity wave that appears above the middle cloud in temperature measurements on all three orbits. The amplitude and vertical wavelength are about 4 K and 2.5 km respectively, at 65 km. A model for radiative damping implies that the wave intrinsic frequency is approximately 2 x 10(exp 4) rad/sec, the corresponding ratio between horizontal and vertical wavelengths is approximately 100. The wave is nearly stationary relative to the surface or the Sun. Radiative attenuation limits the wave amplitude at altitudes above approximately 65 km, leading to wave drag on the mean zonal winds of about +0.4 m/sec per day (eastward). The sign, magnitude, and location of this forcing suggest a possible role in explaining the decrease with height in the zonal wind speed that is believed to occur above the cloud tops. Temperature oscillations with larger vertical wavelengths (5-10 km) were also observed on all three orbits, but we are able unable to interpret these

  1. An Atmospheric Variability Model for Venus Aerobraking Missions

    Science.gov (United States)

    Tolson, Robert T.; Prince, Jill L. H.; Konopliv, Alexander A.

    2013-01-01

    Aerobraking has proven to be an enabling technology for planetary missions to Mars and has been proposed to enable low cost missions to Venus. Aerobraking saves a significant amount of propulsion fuel mass by exploiting atmospheric drag to reduce the eccentricity of the initial orbit. The solar arrays have been used as the primary drag surface and only minor modifications have been made in the vehicle design to accommodate the relatively modest aerothermal loads. However, if atmospheric density is highly variable from orbit to orbit, the mission must either accept higher aerothermal risk, a slower pace for aerobraking, or a tighter corridor likely with increased propulsive cost. Hence, knowledge of atmospheric variability is of great interest for the design of aerobraking missions. The first planetary aerobraking was at Venus during the Magellan mission. After the primary Magellan science mission was completed, aerobraking was used to provide a more circular orbit to enhance gravity field recovery. Magellan aerobraking took place between local solar times of 1100 and 1800 hrs, and it was found that the Venusian atmospheric density during the aerobraking phase had less than 10% 1 sigma orbit to orbit variability. On the other hand, at some latitudes and seasons, Martian variability can be as high as 40% 1 sigmaFrom both the MGN and PVO mission it was known that the atmosphere, above aerobraking altitudes, showed greater variability at night, but this variability was never quantified in a systematic manner. This paper proposes a model for atmospheric variability that can be used for aerobraking mission design until more complete data sets become available.

  2. The photochemical stability of the Venus atmosphere against UV radiation

    International Nuclear Information System (INIS)

    Mills, F.P.; Slanger, T.G.; Allen, M.

    2004-01-01

    Full text: One unresolved question regarding the Venus atmosphere is what chemical mechanism(s) stabilize its primary constituent (CO 2 ) against UV radiation. CO 2 photolyzes on the day side into CO and O after absorbing photons at 2 rather than recombining with CO to form CO 2 , and the intense night side O 2 airglow observed quantitatively supports this. CO and O 2 are photochemically stable in an otherwise pure CO 2 atmosphere so significant abundances of CO and O 2 could accumulate on Venus if no catalytic mechanism existed to speed the reformation of CO 2 . However, the observational upper limit on ground state O 2 is equivalent to 2 from CO and O 2 . Recent laboratory work verified the existence of the ClC(O)OO catalytic mechanism that has been used in photochemical models since the early 1980s. However, there are significant uncertainties in the rates for the component steps of this catalytic mechanism. An alternative mechanism for production of CO 2 that has not previously been modeled but which could be competitive with the ClCO(O)O mechanism is the reaction CO + O 2 (c 1 Σ - u ) → CO 2 + O( 1 D) or O( 1 S), Reaction (1). A range of values for Reaction (1) will be examined in model calculations to compare with observational (UV to IR) constraints and to assess under what conditions this mechanism is competitive with the ClC(O)OO catalytic mechanism. The sensitivity of the results to uncertainties in the CO 2 UV absorption cross section also will be examined

  3. The last British-Irish Ice Sheet: A data-rich environment for ice sheet modelling

    Science.gov (United States)

    Ely, Jeremy; Clark, Chris; Hindmarsh, Richard; Bradley, Sarah

    2017-04-01

    In order to simulate the future dynamics of the Greenland and Antarctic ice sheets, robust numerical models validated by observations of past ice sheet behaviour are required. The extent and dynamics of contemporary ice sheets have been observed at a decadal scale. But a much longer record of ice sheet behaviour (10 ka) can be collated by studying the evidence left behind by palaeo-ice sheets. Extensive geomorphological and geochronological evidence for the past behaviour of the last British-Irish Ice Sheet has been gathered through over 150 years of research and BRITICE-CHRONO, a recent consortium project. This large volume of empirical evidence makes the last British-Irish Ice Sheet one of the best constrained palaeo-ice sheets in the world, and a data-rich environment for ice sheet modelling experiments. Yet, integrating this data and its associated uncertainty and abstraction into ice sheet modelling experiments remains challenging. Here we summarise the available geomorphological and geochronological data and discuss how this will be integrated into ice sheet modelling experiments. Several packages of data, each with its own associated level of interpretation (ranging from raw data to empirically reconstructed ice sheet margins), will be made available to the ice-sheet modelling community. Furthermore, we demonstrate our approach to simulating the empirically reconstructed behaviour of the British-Irish Ice Sheet through a series of ice sheet modelling experiments which account for relative sea level change, and uncertainty in empirically reconstructed ice sheet extent.

  4. A Tailward Moving Current Sheet Normal Magnetic Field Front Followed by an Earthward Moving Dipolarization Front

    Science.gov (United States)

    Hwang, K.-J.; Goldstein, M. L.; Moore, T. E.; Walsh, B. M.; Baishev, D. G.; Moiseyev, A. V.; Shevtsov, B. M.; Yumoto, K.

    2014-01-01

    A case study is presented using measurements from the Cluster spacecraft and ground-based magnetometers that show a substorm onset propagating from the inner to outer plasma sheet. On 3 October 2005, Cluster, traversing an ion-scale current sheet at the near-Earth plasma sheet, detected a sudden enhancement of Bz, which was immediately followed by a series of flux rope structures. Both the local Bz enhancement and flux ropes propagated tailward. Approximately 5 min later, another Bz enhancement, followed by a large density decrease, was observed to rapidly propagate earthward. Between the two Bz enhancements, a significant removal of magnetic flux occurred, possibly resulting from the tailward moving Bz enhancement and flux ropes. In our scenario, this flux removal caused the magnetotail to be globally stretched so that the thinnest sheet formed tailward of Cluster. The thinned current sheet facilitated magnetic reconnection that quickly evolved from plasma sheet to lobe and generated the later earthward moving dipolarization front (DF) followed by a reduction in density and entropy. Ground magnetograms located near the meridian of Cluster's magnetic foot points show two-step bay enhancements. The positive bay associated with the first Bz enhancement indicates that the substorm onset signatures propagated from the inner to the outer plasma sheet, consistent with the Cluster observation. The more intense bay features associated with the later DF are consistent with the earthward motion of the front. The event suggests that current disruption signatures that originated in the near-Earth current sheet propagated tailward, triggering or facilitating midtail reconnection, thereby preconditioning the magnetosphere for a later strong substorm enhancement.

  5. Aplikasi Dua Segitiga Sebangun pada Studi Venus Transit di Matahari Tanggal 8 Juni 2004 dari BPD LAPAN Watukosek

    Directory of Open Access Journals (Sweden)

    Nanang Widodo

    2013-11-01

    Full Text Available Transit planet Venus di cakram matahari (jari-jari = 696000 km merupakan peristiwa alam yang dapat dilihat secara berkala. Planet Venus merupakan planet kedua dalam sistem tata surya yang mempunyai orbit lebih dekat ke matahari (= 0,723 Astronomical Unit dibanding jarak bumi-matahari (= 149.600.000 km = 1 AU. Sehingga pada suatu waktu tertentu ada peluang berada tepat di depan Bumi, saat menghadap matahari atau dikenal dengan transit Venus. Proses pengamatan fenomena transit Venus di cakram matahari tersebut dapat diimplimentasikan sebagai aplikasi dua segitiga sebangun, Dimana jari-jari planet Venus (jari-jari = 6051,8 km dinyatakan sebagai tinggi benda dan jari-jari tinggi bayangan Venus sebesar 20880 km (= 3,65 mm pada cakram matahari. Dimana diameter matahari 1.392.000 km (= 240 mm pada lembar sket. Dengan pengukuran jarak tempuh Venus transit 72,4 mm (419 920 km di cakram matahari terhadap waktu kontak pertama bayangan Venus pada jam 05.28 UT (12.28 WIB di tepi timur hingga akhir transit pada 17.50 UT (14.50 WIB diperoleh kecepatan bayangan Venus sebesar 49,286 km/detik

  6. Sulfur Earth

    Science.gov (United States)

    de Jong, B. H.

    2007-12-01

    Variations in surface tension affect the buoyancy of objects floating in a liquid. Thus an object floating in water will sink deeper in the presence of dishwater fluid. This is a very minor but measurable effect. It causes for instance ducks to drown in aqueous solutions with added surfactant. The surface tension of liquid iron is very strongly affected by the presence of sulfur which acts as a surfactant in this system varying between 1.9 and 0.4 N/m at 10 mass percent Sulfur (Lee & Morita (2002), This last value is inferred to be the maximum value for Sulfur inferred to be present in the liquid outer core. Venting of Sulfur from the liquid core manifests itself on the Earth surface by the 105 to 106 ton of sulfur vented into the atmosphere annually (Wedepohl, 1984). Inspection of surface Sulfur emission indicates that venting is non-homogeneously distributed over the Earth's surface. The implication of such large variation in surface tension in the liquid outer core are that at locally low Sulfur concentration, the liquid outer core does not wet the predominantly MgSiO3 matrix with which it is in contact. However at a local high in Sulfur, the liquid outer core wets this matrix which in the fluid state has a surface tension of 0.4 N/m (Bansal & Doremus, 1986), couples with it, and causes it to sink. This differential and diapiric movement is transmitted through the essentially brittle mantle (1024 Pa.s, Lambeck & Johnson, 1998; the maximum value for ice being about 1030 Pa.s at 0 K, in all likely hood representing an upper bound of viscosity for all materials) and manifests itself on the surface by the roughly 20 km differentiation, about 0.1 % of the total mantle thickness, between topographical heights and lows with concomitant lateral movement in the crust and upper mantle resulting in thin skin tectonics. The brittle nature of the medium though which this movement is transmitted suggests that the extremes in topography of the D" layer are similar in range to

  7. Geometry of thin liquid sheet flows

    Science.gov (United States)

    Chubb, Donald L.; Calfo, Frederick D.; Mcconley, Marc W.; Mcmaster, Matthew S.; Afjeh, Abdollah A.

    1994-01-01

    Incompresible, thin sheet flows have been of research interest for many years. Those studies were mainly concerned with the stability of the flow in a surrounding gas. Squire was the first to carry out a linear, invicid stability analysis of sheet flow in air and compare the results with experiment. Dombrowski and Fraser did an experimental study of the disintegration of sheet flows using several viscous liquids. They also detected the formulation of holes in their sheet flows. Hagerty and Shea carried out an inviscid stability analysis and calculated growth rates with experimental values. They compared their calculated growth rates with experimental values. Taylor studied extensively the stability of thin liquid sheets both theoretically and experimentally. He showed that thin sheets in a vacuum are stable. Brown experimentally investigated thin liquid sheet flows as a method of application of thin films. Clark and Dumbrowski carried out second-order stability analysis for invicid sheet flows. Lin introduced viscosity into the linear stability analysis of thin sheet flows in a vacuum. Mansour and Chigier conducted an experimental study of the breakup of a sheet flow surrounded by high-speed air. Lin et al. did a linear stability analysis that included viscosity and a surrounding gas. Rangel and Sirignano carried out both a linear and nonlinear invisid stability analysis that applies for any density ratio between the sheet liquid and the surrounding gas. Now there is renewed interest in sheet flows because of their possible application as low mass radiating surfaces. The objective of this study is to investigate the fluid dynamics of sheet flows that are of interest for a space radiator system. Analytical expressions that govern the sheet geometry are compared with experimental results. Since a space radiator will operate in a vacuum, the analysis does not include any drag force on the sheet flow.

  8. Greenland ice sheet mass balance: a review.

    Science.gov (United States)

    Khan, Shfaqat A; Aschwanden, Andy; Bjørk, Anders A; Wahr, John; Kjeldsen, Kristian K; Kjær, Kurt H

    2015-04-01

    Over the past quarter of a century the Arctic has warmed more than any other region on Earth, causing a profound impact on the Greenland ice sheet (GrIS) and its contribution to the rise in global sea level. The loss of ice can be partitioned into processes related to surface mass balance and to ice discharge, which are forced by internal or external (atmospheric/oceanic/basal) fluctuations. Regardless of the measurement method, observations over the last two decades show an increase in ice loss rate, associated with speeding up of glaciers and enhanced melting. However, both ice discharge and melt-induced mass losses exhibit rapid short-term fluctuations that, when extrapolated into the future, could yield erroneous long-term trends. In this paper we review the GrIS mass loss over more than a century by combining satellite altimetry, airborne altimetry, interferometry, aerial photographs and gravimetry data sets together with modelling studies. We revisit the mass loss of different sectors and show that they manifest quite different sensitivities to atmospheric and oceanic forcing. In addition, we discuss recent progress in constructing coupled ice-ocean-atmosphere models required to project realistic future sea-level changes.

  9. Combined Radiation Belt - Plasma Sheet System Modeling

    Science.gov (United States)

    Aseev, Nikita; Shprits, Yuri; Kellerman, Adam; Drozdov, Alexander; Zhu, Hui

    2017-04-01

    Recent years have given rise to numerous mathematical models of the Earth's radiation belt dynamics. Driven by observations at geosynchronous orbit (GEO) where satellites (e.g. GOES and LANL) provide extensive in-situ measurements, radiation belt models usually take into account only diffusion processes in the energetic electron belts (100 keV and greater), leaving aside the dynamics of colder source population (tens of keV). Such models are able to reconstruct the radiation belt state, but they are not capable of predicting the electron dynamics at GEO, where many communication and navigation satellites currently operate. In this work we present combined four-dimensional electron radiation belt - plasma sheet model accounting for adiabatic advective transport, radial diffusion due to interaction with ULF waves, local acceleration of electrons, scattering into the atmosphere, magnetopause shadowing, and adiabatic effects due to contraction and expansion of the magnetic field. The developed model is applicable to energetic, relativistic and ultrarelativistic electrons as well as to source electron population. The model provides spatial particle distribution allowing us to compare and validate the model with multiple satellite measurements at different MLT sectors (e.g. Van Allen Probes, GOES, LANL, THEMIS). The model can be helpful for the prediction of crucial for satellite operators geosynchronous electron fluxes and electron radiation belt dynamics including the heart of the outer belt, slot region and inner belt.

  10. Ice sheet hydrology from observations

    Energy Technology Data Exchange (ETDEWEB)

    Jansson, Peter (Dept. of Physical Geography and Quaternary Geology, Stockholm Univ-, Stockholm (Sweden))

    2010-11-15

    The hydrological systems of ice sheets are complex. Our view of the system is split, largely due to the complexity of observing the systems. Our basic knowledge of processes have been obtained from smaller glaciers and although applicable in general to the larger scales of the ice sheets, ice sheets contain features not observable on smaller glaciers due to their size. The generation of water on the ice sheet surface is well understood and can be satisfactorily modeled. The routing of water from the surface down through the ice is not complicated in terms of procat has been problematic is the way in which the couplings between surface and bed has been accomplished through a kilometer of cold ice, but with the studies on crack propagation and lake drainage on Greenland we are beginning to understand also this process and we know water can be routed through thick cold ice. Water generation at the bed is also well understood but the main problem preventing realistic estimates of water generation is lack of detailed information about geothermal heat fluxes and their geographical distribution beneath the ice. Although some average value for geothermal heat flux may suffice, for many purposes it is important that such values are not applied to sub-regions of significantly higher fluxes. Water generated by geothermal heat constitutes a constant supply and will likely maintain a steady system beneath the ice sheet. Such a system may include subglacial lakes as steady features and reconfiguration of the system is tied to time scales on which the ice sheet geometry changes so as to change pressure gradients in the basal system itself. Large scale re-organization of subglacial drainage systems have been observed beneath ice streams. The stability of an entirely subglacially fed drainage system may hence be perturbed by rapid ice flow. In the case of Antarctic ice streams where such behavior has been observed, the ice streams are underlain by deformable sediments. It is

  11. Ohm's law for a current sheet

    Science.gov (United States)

    Lyons, L. R.; Speiser, T. W.

    1985-01-01

    The paper derives an Ohm's law for single-particle motion in a current sheet, where the magnetic field reverses in direction across the sheet. The result is considerably different from the resistive Ohm's law often used in MHD studies of the geomagnetic tail. Single-particle analysis is extended to obtain a self-consistency relation for a current sheet which agrees with previous results. The results are applicable to the concept of reconnection in that the electric field parallel to the current is obtained for a one-dimensional current sheet with constant normal magnetic field. Dissipated energy goes directly into accelerating particles within the current sheet.

  12. Technology to Market Fact Sheet

    Energy Technology Data Exchange (ETDEWEB)

    None

    2016-02-01

    This fact sheet is an overview of the Technology to Market subprogram at the U.S. Department of Energy SunShot Initiative. The SunShot Initiative’s Technology to Market subprogram builds on SunShot’s record of moving groundbreaking and early-stage technologies and business models through developmental phases to commercialization. Technology to Market targets two known funding gaps: those that occur at the prototype commercialization stage and those at the commercial scale-up stage.

  13. Boundary layers as the primary transport regions of the earth's magnetotail

    International Nuclear Information System (INIS)

    Eastman, T.E.; Frank, L.A.; Huang, C.Y.

    1985-01-01

    A comprehensive survey of ISEE and IMP LEPEDEA plasma measurements in the earth's magnetotail reveals that the magnetospheric boundary layer and the plasma sheet boundary layer are the primary transport regions there. These plasma measurements also distinguish various components of the plasma sheet, including the central plasma sheet and plasma sheet boundary layer. A significant new result reported here is the existence of cold-and hot-plasma components that are spatially copresent within the central plasma sheet. Such plasma components cannot be explained merely by temporal variations in spectra involving the entire plasma sheet. Contributions to a low-temperature component of the plasma sheet enter directly from the boundary layer located along the magnetotail flanks. Field-aligned flows predominate within the plasma sheet boundary layer, which is almost always present and is located near the northern and southern border of the plasma sheet. The plasma sheet boundary layer comprises highly anisotropic ion distributions, including counteracting ion beams, that evolve into the hot, isotropic component of the plasma sheet

  14. Individual and combined effects of ice sheets and precession on MIS-13 climate

    Directory of Open Access Journals (Sweden)

    Q. Z. Yin

    2009-06-01

    Full Text Available An Earth System Model of Intermediate Complexity is used to investigate the role of insolation and of the size of ice sheets on the regional and global climate of marine isotope stage (MIS 13. The astronomical forcing is selected at two dates with opposite precession, one when northern hemisphere (NH summer occurs at perihelion (at 506 ka (1 ka=1000 years BP, and the other when it occurs at aphelion (at 495 ka BP. Five different volumes of the Eurasian ice sheet (EA and North American ice sheet (NA, ranging from 0 to the Last Glacial Maximum (LGM one, are used. The global cooling due to the ice sheets is mainly related to their area, little to their height. The regional cooling and warming anomalies caused by the ice sheets intensify with increasing size. Precipitation over different monsoon regions responds differently to the size of the ice sheets. Over North Africa and India, precipitation decreases with increasing ice sheet size due to the southward shift of the Intertropical Convergence Zone (ITCZ, whatever the astronomical configuration is. However, the situation is more complicated over East Asia. The ice sheets play a role through both reducing the land/ocean thermal contrast and generating a wave train which is topographically induced by the EA ice sheet. This wave train contributes to amplify the Asian land/ocean pressure gradient in summer and finally reinforces the precipitation. The presence of this wave train depends on the combined effect of the ice sheet size and insolation. When NH summer occurs at perihelion, the EA is able to induce this wave train whatever its size is, and this wave train plays a more important role than the reduction of the land/ocean thermal contrast. Therefore, the ice sheets reinforce the summer precipitation over East China whatever their sizes are. However, when NH summer occurs at aphelion, there is a threshold in the ice volume beyond which the wave train is not induced anymore. Therefore, below this

  15. Intensity variation of cosmic rays near the heliospheric current sheet

    International Nuclear Information System (INIS)

    Badruddin, K.S.; Yadav, R.S.; Yadav, N.R.

    1985-01-01

    Cosmic ray intensity variations near the heliospheric current sheet-both above and below it-have been studied during 1964-76. Superposed epoch analysis of the cosmic ray neutron monitor data with respect to sector boundaries (i.e., heliospheric current sheet crossings) has been performed. In this analysis data from neutron monitors well distributed in latitude over the Earth's surface is used. First, this study has been made during the two solar activity minimum periods 1964-65 and 1975-76, using the data from Thule (cut-off rigidity O GV), Deep River (cut-off rigidity 1.02 GV), Rome (cut-off rigidity 6.32 GV) and Huancayo (cut-off rigidity 13.45 GV) neutron monitors. The data is analyzed from Deep River, Rome and Huancayo neutron monitors, for which data is available for the full period (1964-76), by dividing the periods according to the changes in solar activity, interplanetary magnetic field polarity and coronal holes. All these studies have shown a negative gradient with respect to heliomagnetic latitude (current sheet). These results have been discussed in the light of theoretical and observational evidences. Suggestions have been given to overcome the discrepancy between the observational and theoretical results. Further, possible explanations for these observational results have been suggested. (author)

  16. Nonadiabatic heating of the central plasma sheet at substorm onset

    International Nuclear Information System (INIS)

    Huang, C.Y.; Frank, L.A.; Rostoker, G.; Fennell, J.; Mitchell, D.G.

    1992-01-01

    Heating events in the plasma sheet boundary layer and central plasma sheet are found to occur at the onset of expansive phase activity. The main effect is a dramatic increase in plasma temperature, coincident with a partial dipolarization of the magnetic field. Fluxes of energetic particles increase without dispersion during these events which occur at all radial distances up to 23 R E , the apogee of the ISEIE spacecraft. A major difference between these heating events and those observed at geosynchronous distances lies in the heating mechanism which is nonadiabatic beyond 10 R E but may be adiabatic closer to Earth. The energy required to account for the increase in plasma thermal energy is comparable with that required for Joule heating of the ionosphere. The plasma sheet must be considered as a major sink in the energy balance of substorm. The authors estimate lobe magnetic pressures during these events. Changes in lobe pressure are generally not correlated with onsets or intensifications of expansive phase activity

  17. Die Deformation Measurement System during Sheet Metal Forming

    Science.gov (United States)

    Funada, J.; Takahashi, S.; Fukiharu, H.

    2011-08-01

    In order to reduce affection to the earth environment, it is necessary to lighten the vehicles. For this purpose, high tensile steels are applied. Because of high strength, high forming force is required for producing automotive sheet metal parts. In this situation, since the dies are elastic, they are deformed during forming parts. For reducing die developing period, sheet metal forming simulation is widely applied. In the numerical simulation, rigid dies are usually used for shortening computing time. It means that the forming conditions in the actual forming and the simulation are different. It will make large errors in the results between actual forming and simulation. It can be said that if contact pressure between dies and a sheet metal in the simulation can be reproduced in the actual forming, the differences of forming results between them can also been reduced. The basic idea is to estimate die shape which can produce the same distribution as computed from simulation with rigid dies. In this study, die deformation analyses with Finite Element Method as basic technologies are evaluated. For example, simple shape and actual dies elastic contact problems were investigated. The contact width between simple shape dies was investigated. The computed solutions were in good agreement with experimental results. The one case of the actual dies in two cases was also investigated. Bending force was applied to the blank holder with a mechanical press machine. The methodology shown with applying inductive displacement sensor for measuring die deformation during applying force was also proposed.

  18. On the nature of the plasma sheet boundary layer

    Energy Technology Data Exchange (ETDEWEB)

    Hones, E.W. Jr. (Mission Research Corp., Los Alamos, NM (USA) Los Alamos National Lab., NM (USA))

    1990-01-01

    The regions of the plasma sheet adjacent to the north and south lobes of the magnetotail have been described by many experimenters as locations of beams of energetic ions and fast-moving plasma directed primarily earthward and tailward along magnetic field lines. Measurements taken as satellites passed through one or the other of these boundary layers have frequently revealed near-earth mirroring of ions and a vertical segregation of velocities of both earthward-moving and mirroring ions with the fastest ions being found nearest the lobe-plasma sheet interface. These are features expected for particles from a distant tail source {bar E} {times} {bar B} drifting in a dawn-to-dusk electric field and are consistent with the source being a magnetic reconnection region. The plasma sheet boundary layers are thus understood as separatrix layers, bounded at their lobeward surfaces by the separatrices from the distant neutral line. This paper will review the observations that support this interpretation. 10 refs., 7 figs.

  19. Simulation of the last glacial cycle with a coupled climate ice-sheet model of intermediate complexity

    Directory of Open Access Journals (Sweden)

    A. Ganopolski

    2010-04-01

    Full Text Available A new version of the Earth system model of intermediate complexity, CLIMBER-2, which includes the three-dimensional polythermal ice-sheet model SICOPOLIS, is used to simulate the last glacial cycle forced by variations of the Earth's orbital parameters and atmospheric concentration of major greenhouse gases. The climate and ice-sheet components of the model are coupled bi-directionally through a physically-based surface energy and mass balance interface. The model accounts for the time-dependent effect of aeolian dust on planetary and snow albedo. The model successfully simulates the temporal and spatial dynamics of the major Northern Hemisphere (NH ice sheets, including rapid glacial inception and strong asymmetry between the ice-sheet growth phase and glacial termination. Spatial extent and elevation of the ice sheets during the last glacial maximum agree reasonably well with palaeoclimate reconstructions. A suite of sensitivity experiments demonstrates that simulated ice-sheet evolution during the last glacial cycle is very sensitive to some parameters of the surface energy and mass-balance interface and dust module. The possibility of a considerable acceleration of the climate ice-sheet model is discussed.

  20. Virtual Earth System Laboratory (VESL): Effective Visualization of Earth System Data and Process Simulations

    Science.gov (United States)

    Quinn, J. D.; Larour, E. Y.; Cheng, D. L. C.; Halkides, D. J.

    2016-12-01

    The Virtual Earth System Laboratory (VESL) is a Web-based tool, under development at the Jet Propulsion Laboratory and UC Irvine, for the visualization of Earth System data and process simulations. It contains features geared toward a range of applications, spanning research and outreach. It offers an intuitive user interface, in which model inputs are changed using sliders and other interactive components. Current capabilities include simulation of polar ice sheet responses to climate forcing, based on NASA's Ice Sheet System Model (ISSM). We believe that the visualization of data is most effective when tailored to the target audience, and that many of the best practices for modern Web design/development can be applied directly to the visualization of data: use of negative space, color schemes, typography, accessibility standards, tooltips, etc cetera. We present our prototype website, and invite input from potential users, including researchers, educators, and students.