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  1. If not water then what? - The possible role of CO2 hydrates in terraforming processes on Mars

    NASA Astrophysics Data System (ADS)

    Falenty, A.; Kuhs, W. F.

    similar. The ice coating developed around meta-stable hydrates prevents them from further decomposition. For the long term processes like climate change, it was doubtful that a significant amount of hydrates will survive the decomposition before entering self-preservation state. This discovery extends the already known self-preservation regime of gas hydrates and opens further, alternatives for the explanations of young geomorphologic features observed on Mars frequently related to liquid water flow in terms of a fluidised mixture of water and CO2 gas. [1] J.S.Kargel Mars: A Warmer Wetter Planet, Springer Berlin, 2004. [2] D.K. Staykova, W. F. Kuhs, A. N. Salamatin, and T. Hansen (2003) 1 Formation of Porous Gas Hydrates from Ice Powders: Diffraction Experiments and Multistage Model. J. Phys. Chem. B 107,10299-10311 [3] G. Genov, W. F. Kuhs, D. K. Staykova, E. Goreshnik, and A. N. Salamatin (2004), Experimental studies on the formation of porous gas hydrates, Am. Miner. 89, 1228- 1239 [4] W.F. Kuhs, D.K. Staykova, A.N.Salamatin (2006) Formation of methane hydrate from polydisperse ice powders. J.Phys.Chem. B xxx (in press) [5] W. F. Kuhs, G. Genov, D. K. Staykova, and T. Hansen (2004), Ice perfection and onset of anomalous preservation of gas hydrates, Phys. Chem. Chem. Phys. 6, 4917-4920 2

  2. Morphology changes in stacking-disordered ice Ich as a function of time and temperature

    NASA Astrophysics Data System (ADS)

    Kuhs, Werner F.; Falenty, Andrzej; Hansen, Thomas C.

    2015-04-01

    Laboratory experiments have shown that ice I crystallizing from water vapour [1] or undercooled liquid water [2] under atmospheric conditions initially forms a stacking disordered arrangement of high complexity; the stacking arrangement is different depending on the starting phase[1]. Both cubic and hexagonal components are locally present and various names of this form of ice have been proposed recently: so-called ice Ic or 'ice Ic'[1], ice Isd [2] or ice Ich[3]. It is has been shown that ice Ich undergoes a progressive transformation of cubic into hexagonal stackings with time and/or increasing temperature [1]. As a mechanisms for this annealing we had proposed the cooperative action of Bjerrrum defects and moving dislocations which become active on a time-scale of minutes at temperatures close to 240K [4]. Here we show from electron-microscopic images that the presence of stacking faults is linked to numerous kinks on the prismatic faces of the trigonal ice crystals of ice Ich [1]. We present details on the annealing kinetics in the temperature range between 170 and 240K and suggest that the kinks of ice Ich crystals may be responsible for the roughness deduced from some air-borne light-scattering experiments, an increased reactivity in particular at temperatures below ~ 200K as well as curvature-induced higher vapour pressures of ice Ich as compared to normal ice Ih. [1] W.F.Kuhs, C.Sippel, T.C.Hansen (2012) PNAS 109:21259-21264 [2] T.Malkin, B.J.Murray, A.V.Brukhno, J.Anwar, C.G.Salzmann (2012) PNAS 109: 1041-1045 [3] T.C.Hansen, C.Sippel, W.F.Kuhs (2014) Z.Krist. DOI 10.1515/zkri-2014-1780 [4] W.F.Kuhs, G.Genov, D.K.Staykova, T.Hansen (2004) 6:4917-4920

  3. Laboratory study on the kinetics of CO2 hydrates in a broad p-T range relevant to Mars

    NASA Astrophysics Data System (ADS)

    Falenty, A.; Kuhs, W. F.

    2007-08-01

    , temporary gas outbursts are conceivable. Between 190K and 240K neither annealing of defective ice Ih nor the crystal regrowth is fast enough to effectively slow down outward diffusing gas molecules. In such a scenario slow decomposition is to be expected and therefore the impact on the surface will be very limited. Surprisingly we also have found "self preservation" in a narrow pressure range. The sealing effect is, however, less pronounced as the preservation mechanism differs from the higher temperature one. Therefore only large agglomerations of CO2 hydrates may be effectively saved from further decomposition. [1] J.S.Kargel Mars: A Warmer Wetter Planet, Springer Berlin, 2004. [2] R. Greve, R.A. Mahajan (2005), Icarus 176, 475-485 [3] D.K. Staykova et al. (2003) J. Phys. Chem. B 107,10299-10311 [4] G. Genov et al. (2004), Am. Miner. 89, 1228-1239 [5] W.F. Kuhs et al. (2006) J.Phys.Chem. B 110 (26), 13283-13295 [6] G. Genov PhD thesis, Georg-August Universität, Göttingen, 2004 [7] W. F. Kuhs et al. (2004), Phys. Chem. Chem. Phys. 6, 4917-4920 [8] A. Falenty et al. (2007) In: Physics and Chemistry of Ice (ed. W. F. Kuhs), RSC Publishing, Cambridge, 2007, pp. 171-179

  4. EDITORIAL: Focus on Cloaking and Transformation Optics

    NASA Astrophysics Data System (ADS)

    Leonhardt, Ulf; Smith, David R.

    2008-11-01

    coordinate transformations. If the coordinates they conjure up run backwards one gets negative refraction, if they exclude some region of space one makes anything inside invisible [4]. In physics, general relativity has honed the theoretical tools for understanding curved space and curved-coordinate transformations. In transformation optics, general relativity has become a theoretical tool for solving practical engineering problems [4]. What an unorthodox connection! This focus issue represents a snapshot of this rapidly developing research area. It is not restricted to optics or electromagnetism, though. Metamaterials for acoustics also exist and can be applied in ways similar to optical metamaterials. So transformation optics not only attracts an unusual mix of scientists, but also spans a range of applications in optics and beyond. Transformation optics has the potential to transform optics, for example by visualizing invisibility and making materials beyond materials—metamaterials. But before we transgress the boundaries to the hermeneutics of transformation optics [5], let the papers speak for themselves. References [1] Yao J, Liu Z, Liu Y, Wang Y, Sun C, Bartal G, Stacy A M and Zhang X 2008 Science 321 930 [2] Valentine J, Zhang S, Zentgraf T, Ulin-Avila E, Genov D A, Bartal G and Zhang X 2008 Nature 455 376 [3] Schurig D, Mock J J, Justice B J, Cummer S A, Pendry J B, Starr A F and Smith D R 2006 Science 314 977 [4] Leonhardt U and Philbin T G 2006 New J. Phys. 8 247 [5] Sokal A D 1996 Social Text 14(46/47) 217 Focus on Cloaking and Transformation Optics Contents Transformation optics for the full dielectric electromagnetic cloak and metal-dielectric planar hyperlens D P Gaillot, C Croënne, F Zhang and D Lippens Transmutation of singularities in optical instruments Tomáš Tyc and Ulf Leonhardt Electromagnetic cloaking with canonical spiral inclusions K Guven, E Saenz, R Gonzalo, E Ozbay and S Tretyakov Theory and potentials of multi-layered plasmonic covers for

  5. EDITORIAL: Focus on Cloaking and Transformation Optics

    NASA Astrophysics Data System (ADS)

    Leonhardt, Ulf; Smith, David R.

    2008-11-01

    coordinate transformations. If the coordinates they conjure up run backwards one gets negative refraction, if they exclude some region of space one makes anything inside invisible [4]. In physics, general relativity has honed the theoretical tools for understanding curved space and curved-coordinate transformations. In transformation optics, general relativity has become a theoretical tool for solving practical engineering problems [4]. What an unorthodox connection! This focus issue represents a snapshot of this rapidly developing research area. It is not restricted to optics or electromagnetism, though. Metamaterials for acoustics also exist and can be applied in ways similar to optical metamaterials. So transformation optics not only attracts an unusual mix of scientists, but also spans a range of applications in optics and beyond. Transformation optics has the potential to transform optics, for example by visualizing invisibility and making materials beyond materials—metamaterials. But before we transgress the boundaries to the hermeneutics of transformation optics [5], let the papers speak for themselves. References [1] Yao J, Liu Z, Liu Y, Wang Y, Sun C, Bartal G, Stacy A M and Zhang X 2008 Science 321 930 [2] Valentine J, Zhang S, Zentgraf T, Ulin-Avila E, Genov D A, Bartal G and Zhang X 2008 Nature 455 376 [3] Schurig D, Mock J J, Justice B J, Cummer S A, Pendry J B, Starr A F and Smith D R 2006 Science 314 977 [4] Leonhardt U and Philbin T G 2006 New J. Phys. 8 247 [5] Sokal A D 1996 Social Text 14(46/47) 217 Focus on Cloaking and Transformation Optics Contents Transformation optics for the full dielectric electromagnetic cloak and metal-dielectric planar hyperlens D P Gaillot, C Croënne, F Zhang and D Lippens Transmutation of singularities in optical instruments Tomáš Tyc and Ulf Leonhardt Electromagnetic cloaking with canonical spiral inclusions K Guven, E Saenz, R Gonzalo, E Ozbay and S Tretyakov Theory and potentials of multi-layered plasmonic covers for