laboratory data and modeling of plutos spectra laboratoire de planétologie de grenoble, cnrs -...
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Laboratory data and modeling of Pluto’s spectra
Laboratoire de Planétologie de Grenoble,
CNRS - Université J. Fourier
Bernard Schmitt
Eric Quirico, Sylvain Douté et Olivier Brissaud
Optical properties of ices
Schmitt et al., 1998, Solar System Ices, p.199
Mesurement of spectral properties (0,4 – 200 µm) of molecular solids
Study effects of:- Temperature- Phases- Composition- Compounds - UV irradiations
Infrared Spectrometer with an optical cryogenic system (10 - 300 K)
Solids : - Ices - Clathrates, Hydrates, - Organics, - Minerals, …
Ices, organics, …Near and mid-infrared
Nitrogen
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 Grundy et al., 1993, Icarus, 105, 254
Schmitt et al., 1998, Solar System Ices, 199
Methane
Grundy et al., 2002, Icarus, 155, 486
-Very large number of bands of various intensities, down to the visible range
- Band shape sensitive to temperature
Vis Near-IR Mid-IR
Methane
CH4 – N2 mixtures
Schmitt et al., 1998, Solar System Ices, 199
- 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 !
Diluted CH4 – N2 mixturesCH4 spectrum sensitive to :
- Pure vs diluted
- N2 phase and temperature
- CH4 abundance (> 2%)
Quirico & Schmitt 1997a Icarus, 127, 354
Schmitt et al., 1998, Solar System Ices, 199
Spectrum = combination of the spectra of the saturated N2:CH4 solutions
Rich CH4 – N2 mixtures
Quirico et al; 1996 PSS, 44, 973
Water ice
Schmitt et al., 1998, Solar System Ices, 199
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
Water ice : Phase and temperature
Grundy et al., 1998, JGR E, 103, 25809
Ammonia
Schmitt et al., 1998, Solar System Ices, 199
Pure ammonia :
- Several phases
Ammonia hydrates:
- 3 hydrate types + several phases
Complex spectra and not yet well studied (in course …)
Simple hydrocarbons
Quirico & Schmitt 1997a Icarus, 127, 354
Carbon monoxyde
Quirico & Schmitt 1997a Icarus, 127, 354
Quirico & Schmitt 1997a Icarus, 128, 181
Carbon dioxyde
Quirico & Schmitt 1997a Icarus, 127, 354
- Weakly sensitive to temperature
Methanol, nitriles, oxydes, …Many molecules measured or under study :
CH3OH, HC3N, C3H4, C2H5CN, C6H6, C3N3H3, …
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
• Visible slope and near-IR band strength sensitive to composition and structure of the macromolecular solid
yellow tholins
poly-HCN
black tholins
samples from LISA
C-H-N compounds
Wavelength (nm)
Ref
lect
ance
Bernard et al. 2006, Icarus 185, 301
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, …
Molecules identification
Quirico et al. 1999 Icarus, 139, 159
Physical state
Quirico et al. 1999 Icarus, 139, 159
Distribution, abundance, grain size
Different ways of mixing :
- Molecular
- Compounds
- Granular
- Spatial
- Stratigraphy
(tholins)
Douté et al. 1999 Icarus, 142, 421
Complete modeling
• Comparison between objects
New-Horizon : spatial distribution
Quirico et al. 1999 Icarus, 139, 159