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Laboratory data and modeling of Pluto’s spectra

This study explores the optical properties and spectral properties of various compounds found on Pluto's surface, including ices, clathrates, hydrates, organics, and minerals. The effects of temperature, phases, composition, compounds, and UV irradiations are also investigated. The study provides insights into the surface thermometry and composition of Pluto.

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Laboratory data and modeling of Pluto’s spectra

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  1. Laboratory data and modeling of Pluto’s spectra Bernard Schmitt Eric Quirico, Sylvain Douté et Olivier Brissaud Laboratoire de Planétologie de Grenoble, CNRS - Université J. Fourier Bernard.Schmitt@obs.ujf-grenoble.fr

  2. Schmitt et al., 1998, Solar System Ices, p.199 Optical properties of ices

  3. Mesurement of spectral properties (0,4 – 200 µm) of molecular solids Infrared Spectrometer with an optical cryogenic system (10 - 300 K) • Solids : • - Ices • Clathrates, Hydrates, • Organics, • Minerals, … • Study effects of: • Temperature • Phases • Composition • Compounds • UV irradiations

  4. Ices, organics, …Near and mid-infrared

  5. Nitrogen 2n • 2 phases • Transition : 35.6K • - 2 very weak bands • - Very sensitive to phase • - Sensitive to temperature • Fundamental band sensitive to CO2, H2O • Spectral shape •  surface thermometer n Grundy et al., 1993, Icarus, 105, 254 Schmitt et al., 1998, Solar System Ices, 199

  6. Methane Vis Near-IR Mid-IR • Very large number of bands of various intensities, down to the visible range • - Band shape sensitive to temperature Grundy et al., 2002, Icarus, 155, 486

  7. Methane

  8. CH4 – N2 mixtures • Spectra very sensitive on the way the molecular mixture is formed • Crystal growth from the liquid under thermodynamic equilibrium best represent the surface of Pluton and Triton ! Schmitt et al., 1998, Solar System Ices, 199

  9. Diluted CH4 – N2 mixtures CH4 spectrum sensitive to : - Pure vs diluted - N2 phase and temperature - CH4 abundance (> 2%) Quirico & Schmitt 1997a Icarus, 127, 354

  10. Rich CH4 – N2 mixtures Spectrum = combination of the spectra of the saturated N2:CH4 solutions Quirico et al; 1996 PSS, 44, 973 Schmitt et al., 1998, Solar System Ices, 199

  11. Water ice Amorphous phase : Spectrum slightly depend on temperature - Similar to high temperature crystalline Crystalline phase : Strong dependence with temperature, especially @ 1.65 µm band  H2O ice thermometer Schmitt et al., 1998, Solar System Ices, 199

  12. Water ice : Phase and temperature Grundy et al., 1998, JGR E, 103, 25809

  13. Ammonia Pure ammonia : - Several phases Ammonia hydrates: - 3 hydrate types + several phases  Complex spectra and not yet well studied (in course …) Schmitt et al., 1998, Solar System Ices, 199

  14. Simple hydrocarbons Quirico & Schmitt 1997a Icarus, 127, 354

  15. Carbon monoxyde 2n 3n Quirico & Schmitt 1997a Icarus, 127, 354 Quirico & Schmitt 1997a Icarus, 128, 181

  16. Carbon dioxyde - Weakly sensitive to temperature Quirico & Schmitt 1997a Icarus, 127, 354

  17. Methanol, nitriles, oxydes, … Many molecules measured or under study : CH3OH, HC3N, C3H4, C2H5CN, C6H6, C3N3H3, …

  18. Mesure de la réflectance spectrale (0,3 – 4,8 µm) bidirectionnelle des surfaces granulaires • Etude effets de la : • - Composition, • - Taille et forme des grains, • - Rugosité de surface, • Indices optiques, … • Mesure spectres et fonctions de diffusion : • - Glaces, minéraux, • - Organiques, • - Matériaux géophysiques, • Applications : • Spectro-imagerie spatiale

  19. yellow tholins poly-HCN black tholins C-H-N compounds • Visible slope and near-IR band strength sensitive to composition and structure of the macromolecular solid Reflectance Wavelength (nm) Bernard et al. 2006, Icarus 185, 301 samples from LISA

  20. surfaces par spectro-imagerie • Composition • Identification de molécules • Etat physique • Modes de coexistence • Abondances • Distribution spatiale • Variations temporelles • Origine - Evolutions • Origine chimique des molécules • Complexité de la matière organique • Microphysique échanges surface/atmosphère • Transports (cycles jour, saison, climat, …) • Liens avec géologie, topographie, …

  21. Molecules identification Quirico et al. 1999 Icarus, 139, 159

  22. Physical state Quirico et al. 1999 Icarus, 139, 159

  23. Distribution, abundance, grain size • Different ways of mixing : • Molecular • Compounds • Granular • Spatial • Stratigraphy (tholins) Douté et al. 1999 Icarus, 142, 421

  24. Complete modeling • Comparison between objects

  25. New-Horizon : spatial distribution Quirico et al. 1999 Icarus, 139, 159

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